Patent Publication Number: US-2022225434-A1

Title: Sidelink Configuration of Wireless Device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/US2020/054304, filed Oct. 5, 2020, which claims the benefit of U.S. Provisional Application No. 62/910,250, filed Oct. 3, 2019, all of which are hereby incorporated by reference in their entireties. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Examples of several of the various embodiments of the present disclosure are described herein with reference to the drawings. 
       FIG. 1A  and  FIG. 1B  illustrate example mobile communication networks in which embodiments of the present disclosure may be implemented. 
       FIG. 2A  and  FIG. 2B  respectively illustrate a New Radio (NR) user plane and control plane protocol stack. 
       FIG. 3  illustrates an example of services provided between protocol layers of the NR user plane protocol stack of  FIG. 2A . 
       FIG. 4A  illustrates an example downlink data flow through the NR user plane protocol stack of  FIG. 2A . 
       FIG. 4B  illustrates an example format of a MAC subheader in a MAC PDU. 
       FIG. 5A  and  FIG. 5B  respectively illustrate a mapping between logical channels, transport channels, and physical channels for the downlink and uplink. 
       FIG. 6  is an example diagram showing RRC state transitions of a UE. 
       FIG. 7  illustrates an example configuration of an NR frame into which OFDM symbols are grouped. 
       FIG. 8  illustrates an example configuration of a slot in the time and frequency domain for an NR carrier. 
       FIG. 9  illustrates an example of bandwidth adaptation using three configured BWPs for an NR carrier. 
       FIG. 10A  illustrates three carrier aggregation configurations with two component carriers. 
       FIG. 10B  illustrates an example of how aggregated cells may be configured into one or more PUCCH groups. 
       FIG. 11A  illustrates an example of an SS/PBCH block structure and location. 
       FIG. 11B  illustrates an example of CSI-RSs that are mapped in the time and frequency domains. 
       FIG. 12A  and  FIG. 12B  respectively illustrate examples of three downlink and uplink beam management procedures. 
       FIG. 13A ,  FIG. 13B , and  FIG. 13C  respectively illustrate a four-step contention-based random access procedure, a two-step contention-free random access procedure, and another two-step random access procedure. 
       FIG. 14A  illustrates an example of CORESET configurations for a bandwidth part. 
       FIG. 14B  illustrates an example of a CCE-to-REG mapping for DCI transmission on a CORESET and PDCCH processing. 
       FIG. 15  illustrates an example of a wireless device in communication with a base station. 
       FIG. 16A ,  FIG. 16B ,  FIG. 16C , and  FIG. 16D  illustrate example structures for uplink and downlink transmission. 
       FIG. 17  is an example of the deployment scenario of D2D communication outside network coverage as per an aspect of an example embodiment of the present disclosure. 
       FIG. 18  illustrates a resource pool for sidelink operations as per an aspect of an example embodiment of the present disclosure. 
       FIG. 19  illustrates a procedure performed by a UE to acquire radio resources for a sidelink while the UE is in RRC idle or RRC inactive state and has sidelink data to transmit as per an aspect of an example embodiment of the present disclosure. 
       FIG. 20  illustrates two RRC connection procedures (A and B) as per an aspect of an example embodiment of the present disclosure. 
       FIG. 21  illustrates a procedure for a UE to acquire a sidelink radio resource in RRC connected state from a base station as per an aspect of an example embodiment of the present disclosure. 
       FIG. 22  illustrates a procedure performed by a UE to acquire SIB, other than SIB1, in RRC idle or RRC inactive as per an aspect of an example embodiment of the present disclosure. 
       FIG. 23  illustrates a procedure performed by a UE to select between a 2-step and 4-step SI request procedure for acquiring an SIB other than SIB1 as per an aspect of an example embodiment of the present disclosure. 
       FIG. 24  illustrates an SI request signal flow for a 2-step SI request procedure (signal flow A) and for a 4-step SI request procedure (signal flow B) as per an aspect of an example embodiment of the present disclosure. 
       FIG. 25  illustrates two example procedures for a UE to acquire one or more SIBs in RRC connected state as per an aspect of an example embodiment of the present disclosure. 
       FIG. 26  illustrates a procedure to receive sidelink authorization information by a base station from an AMF as per an aspect of an example embodiment of the present disclosure. 
       FIG. 27  illustrates a procedure to acquire configuration parameters of a sidelink (Option 1) as per an aspect of an example embodiment of the present disclosure. 
       FIG. 28  illustrates a procedure to acquire configuration parameters of a sidelink (Option 2) as per an aspect of an example embodiment of the present disclosure. 
       FIG. 29  illustrates a procedure to transit an RRC state of UE between RRC connected state and RRC inactive state as per an aspect of an example embodiment of the present disclosure. 
       FIG. 30  illustrates an enhanced procedure to store sidelink bearer configuration in RRC inactive state as per an aspect of an example embodiment of the present disclosure. 
       FIG. 31  illustrates an enhanced procedure to restore/resume sidelink bearer configuration in RRC inactive state as per an aspect of an example embodiment of the present disclosure. 
       FIG. 32  illustrates a procedure to acquire configuration parameters of a sidelink in RRC inactive state by combining procedures with respect to  FIG. 27  and respect to  FIG. 31  as per an aspect of an example embodiment of the present disclosure. 
       FIG. 33  illustrates a procedure to acquire configuration parameters of a sidelink in RRC connected state (Option 1) as per an aspect of an example embodiment of the present disclosure. 
       FIG. 34  illustrates a procedure to acquire configuration parameters of a sidelink in RRC connected state (Option 2) as per an aspect of an example embodiment of the present disclosure. 
       FIG. 35  illustrates latency for acquiring radio resources for a sidelink service as per an aspect of an example embodiment of the present disclosure. 
       FIG. 36  illustrates a UE behavior for requesting a sidelink SIB as per an aspect of an example embodiment of the present disclosure. 
       FIG. 37  illustrates a procedure to manage RRC connection (Option 1) as per an aspect of an example embodiment of the present disclosure. 
       FIG. 38  illustrates a procedure to manage RRC connection (Option 2) as per an aspect of an example embodiment of the present disclosure. 
       FIG. 39  illustrates a procedure to manage RRC connection for a sidelink SIB (Option 1) as per an aspect of an example embodiment of the present disclosure. 
       FIG. 40  illustrates a procedure to manage RRC connection for a sidelink SIB as per an aspect of an example embodiment of the present disclosure. 
       FIG. 41  is a flow diagram of an aspect of an example embodiment of the present disclosure. 
       FIG. 42  is a flow diagram of an aspect of an example embodiment of the present disclosure. 
    
    
     DETAILED DESCRIPTION 
     In the present disclosure, various embodiments are presented as examples of how the disclosed techniques may be implemented and/or how the disclosed techniques may be practiced in environments and scenarios. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the scope. In fact, after reading the description, it will be apparent to one skilled in the relevant art how to implement alternative embodiments. The present embodiments should not be limited by any of the described exemplary embodiments. The embodiments of the present disclosure will be described with reference to the accompanying drawings. Limitations, features, and/or elements from the disclosed example embodiments may be combined to create further embodiments within the scope of the disclosure. Any figures which highlight the functionality and advantages, are presented for example purposes only. The disclosed architecture is sufficiently flexible and configurable, such that it may be utilized in ways other than that shown. For example, the actions listed in any flowchart may be re-ordered or only optionally used in some embodiments. 
     Embodiments may be configured to operate as needed. The disclosed mechanism may be performed when certain criteria are met, for example, in a wireless device, a base station, a radio environment, a network, a combination of the above, and/or the like. Example criteria may be based, at least in part, on for example, wireless device or network node configurations, traffic load, initial system set up, packet sizes, traffic characteristics, a combination of the above, and/or the like. When the one or more criteria are met, various example embodiments may be applied. Therefore, it may be possible to implement example embodiments that selectively implement disclosed protocols. 
     A base station may communicate with a mix of wireless devices. Wireless devices and/or base stations may support multiple technologies, and/or multiple releases of the same technology. Wireless devices may have some specific capability(ies) depending on wireless device category and/or capability(ies). When this disclosure refers to a base station communicating with a plurality of wireless devices, this disclosure may refer to a subset of the total wireless devices in a coverage area. This disclosure may refer to, for example, a plurality of wireless devices of a given LTE or 5G release with a given capability and in a given sector of the base station. The plurality of wireless devices in this disclosure may refer to a selected plurality of wireless devices, and/or a subset of total wireless devices in a coverage area which perform according to disclosed methods, and/or the like. There may be a plurality of base stations or a plurality of wireless devices in a coverage area that may not comply with the disclosed methods, for example, those wireless devices or base stations may perform based on older releases of LTE or 5G technology. 
     In this disclosure, “a” and “an” and similar phrases are to be interpreted as “at least one” and “one or more.” Similarly, any term that ends with the suffix “(s)” is to be interpreted as “at least one” and “one or more.” In this disclosure, the term “may” is to be interpreted as “may, for example.” In other words, the term “may” is indicative that the phrase following the term “may” is an example of one of a multitude of suitable possibilities that may, or may not, be employed by one or more of the various embodiments. The terms “comprises” and “consists of”, as used herein, enumerate one or more components of the element being described. The term “comprises” is interchangeable with “includes” and does not exclude unenumerated components from being included in the element being described. By contrast, “consists of” provides a complete enumeration of the one or more components of the element being described. The term “based on”, as used herein, should be interpreted as “based at least in part on” rather than, for example, “based solely on”. The term “and/or” as used herein represents any possible combination of enumerated elements. For example, “A, B, and/or C” may represent A; B; C; A and B; A and C; B and C; or A, B, and C. 
     If A and B are sets and every element of A is an element of B, A is called a subset of B. In this specification, only non-empty sets and subsets are considered. For example, possible subsets of B={cell1, cell2} are: {cell1}, {cell2}, and {cell1, cell2}. The phrase “based on” (or equally “based at least on”) is indicative that the phrase following the term “based on” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “in response to” (or equally “in response at least to”) is indicative that the phrase following the phrase “in response to” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “depending on” (or equally “depending at least to”) is indicative that the phrase following the phrase “depending on” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “employing/using” (or equally “employing/using at least”) is indicative that the phrase following the phrase “employing/using” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. 
     The term configured may relate to the capacity of a device whether the device is in an operational or non-operational state. Configured may refer to specific settings in a device that effect the operational characteristics of the device whether the device is in an operational or non-operational state. In other words, the hardware, software, firmware, registers, memory values, and/or the like may be “configured” within a device, whether the device is in an operational or nonoperational state, to provide the device with specific characteristics. Terms such as “a control message to cause in a device” may mean that a control message has parameters that may be used to configure specific characteristics or may be used to implement certain actions in the device, whether the device is in an operational or non-operational state. 
     In this disclosure, parameters (or equally called, fields, or Information elements: IEs) may comprise one or more information objects, and an information object may comprise one or more other objects. For example, if parameter (IE) N comprises parameter (IE) M, and parameter (IE) M comprises parameter (IE) K, and parameter (IE) K comprises parameter (information element) J. Then, for example, N comprises K, and N comprises J. In an example embodiment, when one or more messages comprise a plurality of parameters, it implies that a parameter in the plurality of parameters is in at least one of the one or more messages, but does not have to be in each of the one or more messages. 
     Many features presented are described as being optional through the use of “may” or the use of parentheses. For the sake of brevity and legibility, the present disclosure does not explicitly recite each and every permutation that may be obtained by choosing from the set of optional features. The present disclosure is to be interpreted as explicitly disclosing all such permutations. For example, a system described as having three optional features may be embodied in seven ways, namely with just one of the three possible features, with any two of the three possible features or with three of the three possible features. 
     Many of the elements described in the disclosed embodiments may be implemented as modules. A module is defined here as an element that performs a defined function and has a defined interface to other elements. The modules described in this disclosure may be implemented in hardware, software in combination with hardware, firmware, wetware (e.g. hardware with a biological element) or a combination thereof, which may be behaviorally equivalent. For example, modules may be implemented as a software routine written in a computer language configured to be executed by a hardware machine (such as C, C++, Fortran, Java, Basic, Matlab or the like) or a modeling/simulation program such as Simulink, Stateflow, GNU Octave, or Lab VIEWMathScript. It may be possible to implement modules using physical hardware that incorporates discrete or programmable analog, digital and/or quantum hardware. Examples of programmable hardware comprise: computers, microcontrollers, microprocessors, application-specific integrated circuits (ASICs); field programmable gate arrays (FPGAs); and complex programmable logic devices (CPLDs). Computers, microcontrollers and microprocessors are programmed using languages such as assembly, C, C++ or the like. FPGAs, ASICs and CPLDs are often programmed using hardware description languages (HDL) such as VHSIC hardware description language (VHDL) or Verilog that configure connections between internal hardware modules with lesser functionality on a programmable device. The mentioned technologies are often used in combination to achieve the result of a functional module. 
       FIG. 1A  illustrates an example of a mobile communication network  100  in which embodiments of the present disclosure may be implemented. The mobile communication network  100  may be, for example, a public land mobile network (PLMN) run by a network operator. As illustrated in  FIG. 1A , the mobile communication network  100  includes a core network (CN)  102 , a radio access network (RAN)  104 , and a wireless device  106 . 
     The CN  102  may provide the wireless device  106  with an interface to one or more data networks (DNs), such as public DNs (e.g., the Internet), private DNs, and/or intra-operator DNs. As part of the interface functionality, the CN  102  may set up end-to-end connections between the wireless device  106  and the one or more DNs, authenticate the wireless device  106 , and provide charging functionality. 
     The RAN  104  may connect the CN  102  to the wireless device  106  through radio communications over an air interface. As part of the radio communications, the RAN  104  may provide scheduling, radio resource management, and retransmission protocols. The communication direction from the RAN  104  to the wireless device  106  over the air interface is known as the downlink and the communication direction from the wireless device  106  to the RAN  104  over the air interface is known as the uplink. Downlink transmissions may be separated from uplink transmissions using frequency division duplexing (FDD), time-division duplexing (TDD), and/or some combination of the two duplexing techniques. 
     The term wireless device may be used throughout this disclosure to refer to and encompass any mobile device or fixed (non-mobile) device for which wireless communication is needed or usable. For example, a wireless device may be a telephone, smart phone, tablet, computer, laptop, sensor, meter, wearable device, Internet of Things (IoT) device, vehicle road side unit (RSU), relay node, automobile, and/or any combination thereof. The term wireless device encompasses other terminology, including user equipment (UE), user terminal (UT), access terminal (AT), mobile station, handset, wireless transmit and receive unit (WTRU), and/or wireless communication device. 
     The RAN  104  may include one or more base stations (not shown). The term base station may be used throughout this disclosure to refer to and encompass a Node B (associated with UMTS and/or 3G standards), an Evolved Node B (eNB, associated with E-UTRA and/or 4G standards), a remote radio head (RRH), a baseband processing unit coupled to one or more RRHs, a repeater node or relay node used to extend the coverage area of a donor node, a Next Generation Evolved Node B (ng-eNB), a Generation Node B (gNB, associated with NR and/or 5G standards), an access point (AP, associated with, for example, WiFi or any other suitable wireless communication standard), and/or any combination thereof. A base station may comprise at least one gNB Central Unit (gNB-CU) and at least one a gNB Distributed Unit (gNB-DU). 
     A base station included in the RAN  104  may include one or more sets of antennas for communicating with the wireless device  106  over the air interface. For example, one or more of the base stations may include three sets of antennas to respectively control three cells (or sectors). The size of a cell may be determined by a range at which a receiver (e.g., a base station receiver) can successfully receive the transmissions from a transmitter (e.g., a wireless device transmitter) operating in the cell. Together, the cells of the base stations may provide radio coverage to the wireless device  106  over a wide geographic area to support wireless device mobility. 
     In addition to three-sector sites, other implementations of base stations are possible. For example, one or more of the base stations in the RAN  104  may be implemented as a sectored site with more or less than three sectors. One or more of the base stations in the RAN  104  may be implemented as an access point, as a baseband processing unit coupled to several remote radio heads (RRHs), and/or as a repeater or relay node used to extend the coverage area of a donor node. A baseband processing unit coupled to RRHs may be part of a centralized or cloud RAN architecture, where the baseband processing unit may be either centralized in a pool of baseband processing units or virtualized. A repeater node may amplify and rebroadcast a radio signal received from a donor node. A relay node may perform the same/similar functions as a repeater node but may decode the radio signal received from the donor node to remove noise before amplifying and rebroadcasting the radio signal. 
     The RAN  104  may be deployed as a homogenous network of macrocell base stations that have similar antenna patterns and similar high-level transmit powers. The RAN  104  may be deployed as a heterogeneous network. In heterogeneous networks, small cell base stations may be used to provide small coverage areas, for example, coverage areas that overlap with the comparatively larger coverage areas provided by macrocell base stations. The small coverage areas may be provided in areas with high data traffic (or so-called “hotspots”) or in areas with weak macrocell coverage. Examples of small cell base stations include, in order of decreasing coverage area, microcell base stations, picocell base stations, and femtocell base stations or home base stations. 
     The Third-Generation Partnership Project (3GPP) was formed in 1998 to provide global standardization of specifications for mobile communication networks similar to the mobile communication network  100  in  FIG. 1A . To date, 3GPP has produced specifications for three generations of mobile networks: a third generation (3G) network known as Universal Mobile Telecommunications System (UMTS), a fourth generation (4G) network known as Long-Term Evolution (LTE), and a fifth generation (5G) network known as 5G System (5GS). Embodiments of the present disclosure are described with reference to the RAN of a 3GPP 5G network, referred to as next-generation RAN (NG-RAN). Embodiments may be applicable to RANs of other mobile communication networks, such as the RAN  104  in  FIG. 1A , the RANs of earlier 3G and 4G networks, and those of future networks yet to be specified (e.g., a 3GPP 6G network). NG-RAN implements 5G radio access technology known as New Radio (NR) and may be provisioned to implement 4G radio access technology or other radio access technologies, including non-3GPP radio access technologies. 
       FIG. 1B  illustrates another example mobile communication network  150  in which embodiments of the present disclosure may be implemented. Mobile communication network  150  may be, for example, a PLMN run by a network operator. As illustrated in  FIG. 1B , mobile communication network  150  includes a 5G core network (5G-CN)  152 , an NG-RAN  154 , and UEs  156 A and  156 B (collectively UEs  156 ). These components may be implemented and operate in the same or similar manner as corresponding components described with respect to  FIG. 1A . 
     The 5G-CN  152  provides the UEs  156  with an interface to one or more DNs, such as public DNs (e.g., the Internet), private DNs, and/or intra-operator DNs. As part of the interface functionality, the 5G-CN  152  may set up end-to-end connections between the UEs  156  and the one or more DNs, authenticate the UEs  156 , and provide charging functionality. Compared to the CN of a 3GPP 4G network, the basis of the 5G-CN  152  may be a service-based architecture. This means that the architecture of the nodes making up the 5G-CN  152  may be defined as network functions that offer services via interfaces to other network functions. The network functions of the 5G-CN  152  may be implemented in several ways, including as network elements on dedicated or shared hardware, as software instances running on dedicated or shared hardware, or as virtualized functions instantiated on a platform (e.g., a cloud-based platform). 
     As illustrated in  FIG. 1B , the 5G-CN  152  includes an Access and Mobility Management Function (AMF)  158 A and a User Plane Function (UPF)  158 B, which are shown as one component AMF/UPF  158  in  FIG. 1B  for ease of illustration. The UPF  158 B may serve as a gateway between the NG-RAN  154  and the one or more DNs. The UPF  158 B may perform functions such as packet routing and forwarding, packet inspection and user plane policy rule enforcement, traffic usage reporting, uplink classification to support routing of traffic flows to the one or more DNs, quality of service (QoS) handling for the user plane (e.g., packet filtering, gating, uplink/downlink rate enforcement, and uplink traffic verification), downlink packet buffering, and downlink data notification triggering. The UPF  158 B may serve as an anchor point for intra-/inter-Radio Access Technology (RAT) mobility, an external protocol (or packet) data unit (PDU) session point of interconnect to the one or more DNs, and/or a branching point to support a multi-homed PDU session. The UEs  156  may be configured to receive services through a PDU session, which is a logical connection between a UE and a DN. 
     The AMF  158 A may perform functions such as Non-Access Stratum (NAS) signaling termination, NAS signaling security, Access Stratum (AS) security control, inter-CN node signaling for mobility between 3GPP access networks, idle mode UE reachability (e.g., control and execution of paging retransmission), registration area management, intra-system and inter-system mobility support, access authentication, access authorization including checking of roaming rights, mobility management control (subscription and policies), network slicing support, and/or session management function (SMF) selection. NAS may refer to the functionality operating between a CN and a UE, and AS may refer to the functionality operating between the UE and a RAN. 
     The 5G-CN  152  may include one or more additional network functions that are not shown in  FIG. 1B  for the sake of clarity. For example, the 5G-CN  152  may include one or more of a Session Management Function (SMF), an NR Repository Function (NRF), a Policy Control Function (PCF), a Network Exposure Function (NEF), a Unified Data Management (UDM), an Application Function (AF), and/or an Authentication Server Function (AUSF). 
     The NG-RAN  154  may connect the 5G-CN  152  to the UEs  156  through radio communications over the air interface. The NG-RAN  154  may include one or more gNBs, illustrated as gNB  160 A and gNB  160 B (collectively gNBs  160 ) and/or one or more ng-eNBs, illustrated as ng-eNB  162 A and ng-eNB  162 B (collectively ng-eNBs  162 ). The gNBs  160  and ng-eNBs  162  may be more generically referred to as base stations. The gNBs  160  and ng-eNBs  162  may include one or more sets of antennas for communicating with the UEs  156  over an air interface. For example, one or more of the gNBs  160  and/or one or more of the ng-eNBs  162  may include three sets of antennas to respectively control three cells (or sectors). Together, the cells of the gNBs  160  and the ng-eNBs  162  may provide radio coverage to the UEs  156  over a wide geographic area to support UE mobility. 
     As shown in  FIG. 1B , the gNBs  160  and/or the ng-eNBs  162  may be connected to the 5G-CN  152  by means of an NG interface and to other base stations by an Xn interface. The NG and Xn interfaces may be established using direct physical connections and/or indirect connections over an underlying transport network, such as an internet protocol (IP) transport network. The gNBs  160  and/or the ng-eNBs  162  may be connected to the UEs  156  by means of a Uu interface. For example, as illustrated in  FIG. 1B , gNB  160 A may be connected to the UE  156 A by means of a Uu interface. The NG, Xn, and Uu interfaces are associated with a protocol stack. The protocol stacks associated with the interfaces may be used by the network elements in  FIG. 1B  to exchange data and signaling messages and may include two planes: a user plane and a control plane. The user plane may handle data of interest to a user. The control plane may handle signaling messages of interest to the network elements. 
     The gNBs  160  and/or the ng-eNBs  162  may be connected to one or more AMF/UPF functions of the 5G-CN  152 , such as the AMF/UPF  158 , by means of one or more NG interfaces. For example, the gNB  160 A may be connected to the UPF  158 B of the AMF/UPF  158  by means of an NG-User plane (NG-U) interface. The NG-U interface may provide delivery (e.g., non-guaranteed delivery) of user plane PDUs between the gNB  160 A and the UPF  158 B. The gNB  160 A may be connected to the AMF  158 A by means of an NG-Control plane (NG-C) interface. The NG-C interface may provide, for example, NG interface management, UE context management, UE mobility management, transport of NAS messages, paging, PDU session management, and configuration transfer and/or warning message transmission. 
     The gNBs  160  may provide NR user plane and control plane protocol terminations towards the UEs  156  over the Uu interface. For example, the gNB  160 A may provide NR user plane and control plane protocol terminations toward the UE  156 A over a Uu interface associated with a first protocol stack. The ng-eNBs  162  may provide Evolved UMTS Terrestrial Radio Access (E-UTRA) user plane and control plane protocol terminations towards the UEs  156  over a Uu interface, where E-UTRA refers to the 3GPP 4G radio-access technology. For example, the ng-eNB  162 B may provide E-UTRA user plane and control plane protocol terminations towards the UE  156 B over a Uu interface associated with a second protocol stack. 
     The 5G-CN  152  was described as being configured to handle NR and 4G radio accesses. It will be appreciated by one of ordinary skill in the art that it may be possible for NR to connect to a 4G core network in a mode known as “non-standalone operation.” In non-standalone operation, a 4G core network is used to provide (or at least support) control-plane functionality (e.g., initial access, mobility, and paging). Although only one AMF/UPF  158  is shown in  FIG. 1B , one gNB or ng-eNB may be connected to multiple AMF/UPF nodes to provide redundancy and/or to load share across the multiple AMF/UPF nodes. 
     As discussed, an interface (e.g., Uu, Xn, and NG interfaces) between the network elements in  FIG. 1B  may be associated with a protocol stack that the network elements use to exchange data and signaling messages. A protocol stack may include two planes: a user plane and a control plane. The user plane may handle data of interest to a user, and the control plane may handle signaling messages of interest to the network elements. 
       FIG. 2A  and  FIG. 2B  respectively illustrate examples of NR user plane and NR control plane protocol stacks for the Uu interface that lies between a UE  210  and a gNB  220 . The protocol stacks illustrated in  FIG. 2A  and  FIG. 2B  may be the same or similar to those used for the Uu interface between, for example, the UE  156 A and the gNB  160 A shown in  FIG. 1B . 
       FIG. 2A  illustrates a NR user plane protocol stack comprising five layers implemented in the UE  210  and the gNB  220 . At the bottom of the protocol stack, physical layers (PHYs)  211  and  221  may provide transport services to the higher layers of the protocol stack and may correspond to layer 1 of the Open Systems Interconnection (OSI) model. The next four protocols above PHYs  211  and  221  comprise media access control layers (MACs)  212  and  222 , radio link control layers (RLCs)  213  and  223 , packet data convergence protocol layers (PDCPs)  214  and  224 , and service data application protocol layers (SDAPs)  215  and  225 . Together, these four protocols may make up layer 2, or the data link layer, of the OSI model. 
       FIG. 3  illustrates an example of services provided between protocol layers of the NR user plane protocol stack. Starting from the top of  FIG. 2A  and  FIG. 3 , the SDAPs  215  and  225  may perform QoS flow handling. The UE  210  may receive services through a PDU session, which may be a logical connection between the UE  210  and a DN. The PDU session may have one or more QoS flows. A UPF of a CN (e.g., the UPF  158 B) may map IP packets to the one or more QoS flows of the PDU session based on QoS requirements (e.g., in terms of delay, data rate, and/or error rate). The SDAPs  215  and  225  may perform mapping/de-mapping between the one or more QoS flows and one or more data radio bearers. The mapping/de-mapping between the QoS flows and the data radio bearers may be determined by the SDAP  225  at the gNB  220 . The SDAP  215  at the UE  210  may be informed of the mapping between the QoS flows and the data radio bearers through reflective mapping or control signaling received from the gNB  220 . For reflective mapping, the SDAP  225  at the gNB  220  may mark the downlink packets with a QoS flow indicator (QFI), which may be observed by the SDAP  215  at the UE  210  to determine the mapping/de-mapping between the QoS flows and the data radio bearers. 
     The PDCPs  214  and  224  may perform header compression/decompression to reduce the amount of data that needs to be transmitted over the air interface, ciphering/deciphering to prevent unauthorized decoding of data transmitted over the air interface, and integrity protection (to ensure control messages originate from intended sources. The PDCPs  214  and  224  may perform retransmissions of undelivered packets, in-sequence delivery and reordering of packets, and removal of packets received in duplicate due to, for example, an intra-gNB handover. The PDCPs  214  and  224  may perform packet duplication to improve the likelihood of the packet being received and, at the receiver, remove any duplicate packets. Packet duplication may be useful for services that require high reliability. 
     Although not shown in  FIG. 3 , PDCPs  214  and  224  may perform mapping/de-mapping between a split radio bearer and RLC channels in a dual connectivity scenario. Dual connectivity is a technique that allows a UE to connect to two cells or, more generally, two cell groups: a master cell group (MCG) and a secondary cell group (SCG). A split bearer is when a single radio bearer, such as one of the radio bearers provided by the PDCPs  214  and  224  as a service to the SDAPs  215  and  225 , is handled by cell groups in dual connectivity. The PDCPs  214  and  224  may map/de-map the split radio bearer between RLC channels belonging to cell groups. 
     The RLCs  213  and  223  may perform segmentation, retransmission through Automatic Repeat Request (ARQ), and removal of duplicate data units received from MACs  212  and  222 , respectively. The RLCs  213  and  223  may support three transmission modes: transparent mode (TM); unacknowledged mode (UM); and acknowledged mode (AM). Based on the transmission mode an RLC is operating, the RLC may perform one or more of the noted functions. The RLC configuration may be per logical channel with no dependency on numerologies and/or Transmission Time Interval (TTI) durations. As shown in  FIG. 3 , the RLCs  213  and  223  may provide RLC channels as a service to PDCPs  214  and  224 , respectively. 
     The MACs  212  and  222  may perform multiplexing/demultiplexing of logical channels and/or mapping between logical channels and transport channels. The multiplexing/demultiplexing may include multiplexing/demultiplexing of data units, belonging to the one or more logical channels, into/from Transport Blocks (TBs) delivered to/from the PHYs  211  and  221 . The MAC  222  may be configured to perform scheduling, scheduling information reporting, and priority handling between UEs by means of dynamic scheduling. Scheduling may be performed in the gNB  220  (at the MAC  222 ) for downlink and uplink. The MACs  212  and  222  may be configured to perform error correction through Hybrid Automatic Repeat Request (HARQ) (e.g., one HARQ entity per carrier in case of Carrier Aggregation (CA)), priority handling between logical channels of the UE  210  by means of logical channel prioritization, and/or padding. The MACs  212  and  222  may support one or more numerologies and/or transmission timings. In an example, mapping restrictions in a logical channel prioritization may control which numerology and/or transmission timing a logical channel may use. As shown in  FIG. 3 , the MACs  212  and  222  may provide logical channels as a service to the RLCs  213  and  223 . 
     The PHYs  211  and  221  may perform mapping of transport channels to physical channels and digital and analog signal processing functions for sending and receiving information over the air interface. These digital and analog signal processing functions may include, for example, coding/decoding and modulation/demodulation. The PHYs  211  and  221  may perform multi-antenna mapping. As shown in  FIG. 3 , the PHYs  211  and  221  may provide one or more transport channels as a service to the MACs  212  and  222 . 
       FIG. 4A  illustrates an example downlink data flow through the NR user plane protocol stack.  FIG. 4A  illustrates a downlink data flow of three IP packets (n, n+1, and m) through the NR user plane protocol stack to generate two TBs at the gNB  220 . An uplink data flow through the NR user plane protocol stack may be similar to the downlink data flow depicted in  FIG. 4A . 
     The downlink data flow of  FIG. 4A  begins when SDAP  225  receives the three IP packets from one or more QoS flows and maps the three packets to radio bearers. In  FIG. 4A , the SDAP  225  maps IP packets n and n+1 to a first radio bearer  402  and maps IP packet m to a second radio bearer  404 . An SDAP header (labeled with an “H” in  FIG. 4A ) is added to an IP packet. The data unit from/to a higher protocol layer is referred to as a service data unit (SDU) of the lower protocol layer and the data unit to/from a lower protocol layer is referred to as a protocol data unit (PDU) of the higher protocol layer. As shown in  FIG. 4A , the data unit from the SDAP  225  is an SDU of lower protocol layer PDCP  224  and is a PDU of the SDAP  225 . 
     The remaining protocol layers in  FIG. 4A  may perform their associated functionality (e.g., with respect to  FIG. 3 ), add corresponding headers, and forward their respective outputs to the next lower layer. For example, the PDCP  224  may perform IP-header compression and ciphering and forward its output to the RLC  223 . The RLC  223  may optionally perform segmentation (e.g., as shown for IP packet m in  FIG. 4A ) and forward its output to the MAC  222 . The MAC  222  may multiplex a number of RLC PDUs and may attach a MAC subheader to an RLC PDU to form a transport block. In NR, the MAC subheaders may be distributed across the MAC PDU, as illustrated in  FIG. 4A . In LTE, the MAC subheaders may be entirely located at the beginning of the MAC PDU. The NR MAC PDU structure may reduce processing time and associated latency because the MAC PDU subheaders may be computed before the full MAC PDU is assembled. 
       FIG. 4B  illustrates an example format of a MAC subheader in a MAC PDU. The MAC subheader includes: an SDU length field for indicating the length (e.g., in bytes) of the MAC SDU to which the MAC subheader corresponds; a logical channel identifier (LCID) field for identifying the logical channel from which the MAC SDU originated to aid in the demultiplexing process; a flag (F) for indicating the size of the SDU length field; and a reserved bit (R) field for future use. 
       FIG. 4B  further illustrates MAC control elements (CEs) inserted into the MAC PDU by a MAC, such as MAC  223  or MAC  222 . For example,  FIG. 4B  illustrates two MAC CEs inserted into the MAC PDU. MAC CEs may be inserted at the beginning of a MAC PDU for downlink transmissions (as shown in  FIG. 4B ) and at the end of a MAC PDU for uplink transmissions. MAC CEs may be used for in-band control signaling. Example MAC CEs include: scheduling-related MAC CEs, such as buffer status reports and power headroom reports; activation/deactivation MAC CEs, such as those for activation/deactivation of PDCP duplication detection, channel state information (CSI) reporting, sounding reference signal (SRS) transmission, and prior configured components; discontinuous reception (DRX) related MAC CEs; timing advance MAC CEs; and random access related MAC CEs. A MAC CE may be preceded by a MAC subheader with a similar format as described for MAC SDUs and may be identified with a reserved value in the LCID field that indicates the type of control information included in the MAC CE. 
     Before describing the NR control plane protocol stack, logical channels, transport channels, and physical channels are first described as well as a mapping between the channel types. One or more of the channels may be used to carry out functions associated with the NR control plane protocol stack described later below. 
       FIG. 5A  and  FIG. 5B  illustrate, for downlink and uplink respectively, a mapping between logical channels, transport channels, and physical channels. Information is passed through channels between the RLC, the MAC, and the PHY of the NR protocol stack. A logical channel may be used between the RLC and the MAC and may be classified as a control channel that carries control and configuration information in the NR control plane or as a traffic channel that carries data in the NR user plane. A logical channel may be classified as a dedicated logical channel that is dedicated to a specific UE or as a common logical channel that may be used by more than one UE. A logical channel may also be defined by the type of information it carries. The set of logical channels defined by NR include, for example:
         a paging control channel (PCCH) for carrying paging messages used to page a UE whose location is not known to the network on a cell level;   a broadcast control channel (BCCH) for carrying system information messages in the form of a master information block (MIB) and several system information blocks (SIBs), wherein the system information messages may be used by the UEs to obtain information about how a cell is configured and how to operate within the cell;   a common control channel (CCCH) for carrying control messages together with random access;   a dedicated control channel (DCCH) for carrying control messages to/from a specific the UE to configure the UE; and   a dedicated traffic channel (DTCH) for carrying user data to/from a specific the UE.       

     Transport channels are used between the MAC and PHY layers and may be defined by how the information they carry is transmitted over the air interface. The set of transport channels defined by NR include, for example:
         a paging channel (PCH) for carrying paging messages that originated from the PCCH;   a broadcast channel (BCH) for carrying the MIB from the BCCH;   a downlink shared channel (DL-SCH) for carrying downlink data and signaling messages, including the SIBs from the BCCH;   an uplink shared channel (UL-SCH) for carrying uplink data and signaling messages; and   a random access channel (RACH) for allowing a UE to contact the network without any prior scheduling.       

     The PHY may use physical channels to pass information between processing levels of the PHY. A physical channel may have an associated set of time-frequency resources for carrying the information of one or more transport channels. The PHY may generate control information to support the low-level operation of the PHY and provide the control information to the lower levels of the PHY via physical control channels, known as L1/L2 control channels. The set of physical channels and physical control channels defined by NR include, for example:
         a physical broadcast channel (PBCH) for carrying the MIB from the BCH;   a physical downlink shared channel (PDSCH) for carrying downlink data and signaling messages from the DL-SCH, as well as paging messages from the PCH;   a physical downlink control channel (PDCCH) for carrying downlink control information (DCI), which may include downlink scheduling commands, uplink scheduling grants, and uplink power control commands;   a physical uplink shared channel (PUSCH) for carrying uplink data and signaling messages from the UL-SCH and in some instances uplink control information (UCI) as described below;   a physical uplink control channel (PUCCH) for carrying UCI, which may include HARQ acknowledgments, channel quality indicators (CQI), pre-coding matrix indicators (PMI), rank indicators (RI), and scheduling requests (SR); and   a physical random access channel (PRACH) for random access.       

     Similar to the physical control channels, the physical layer generates physical signals to support the low-level operation of the physical layer. As shown in  FIG. 5A  and  FIG. 5B , the physical layer signals defined by NR include: primary synchronization signals (PSS), secondary synchronization signals (SSS), channel state information reference signals (CSI-RS), demodulation reference signals (DMRS), sounding reference signals (SRS), and phase-tracking reference signals (PT-RS). These physical layer signals will be described in greater detail below. 
       FIG. 2B  illustrates an example NR control plane protocol stack. As shown in  FIG. 2B , the NR control plane protocol stack may use the same/similar first four protocol layers as the example NR user plane protocol stack. These four protocol layers include the PHYs  211  and  221 , the MACs  212  and  222 , the RLCs  213  and  223 , and the PDCPs  214  and  224 . Instead of having the SDAPs  215  and  225  at the top of the stack as in the NR user plane protocol stack, the NR control plane stack has radio resource controls (RRCs)  216  and  226  and NAS protocols  217  and  237  at the top of the NR control plane protocol stack. 
     The NAS protocols  217  and  237  may provide control plane functionality between the UE  210  and the AMF  230  (e.g., the AMF  158 A) or, more generally, between the UE  210  and the CN. The NAS protocols  217  and  237  may provide control plane functionality between the UE  210  and the AMF  230  via signaling messages, referred to as NAS messages. There is no direct path between the UE  210  and the AMF  230  through which the NAS messages can be transported. The NAS messages may be transported using the AS of the Uu and NG interfaces. NAS protocols  217  and  237  may provide control plane functionality such as authentication, security, connection setup, mobility management, and session management. 
     The RRCs  216  and  226  may provide control plane functionality between the UE  210  and the gNB  220  or, more generally, between the UE  210  and the RAN. The RRCs  216  and  226  may provide control plane functionality between the UE  210  and the gNB  220  via signaling messages, referred to as RRC messages. RRC messages may be transmitted between the UE  210  and the RAN using signaling radio bearers and the same/similar PDCP, RLC, MAC, and PHY protocol layers. The MAC may multiplex control-plane and user-plane data into the same transport block (TB). The RRCs  216  and  226  may provide control plane functionality such as: broadcast of system information related to AS and NAS; paging initiated by the CN or the RAN; establishment, maintenance and release of an RRC connection between the UE  210  and the RAN; security functions including key management; establishment, configuration, maintenance and release of signaling radio bearers and data radio bearers; mobility functions; QoS management functions; the UE measurement reporting and control of the reporting; detection of and recovery from radio link failure (RLF); and/or NAS message transfer. As part of establishing an RRC connection, RRCs  216  and  226  may establish an RRC context, which may involve configuring parameters for communication between the UE  210  and the RAN. 
       FIG. 6  is an example diagram showing RRC state transitions of a UE. The UE may be the same or similar to the wireless device  106  depicted in  FIG. 1A , the UE  210  depicted in  FIG. 2A  and  FIG. 2B , or any other wireless device described in the present disclosure. As illustrated in  FIG. 6 , a UE may be in at least one of three RRC states: RRC connected  602  (e.g., RRC_CONNECTED), RRC idle  604  (e.g., RRC_IDLE), and RRC inactive  606  (e.g., RRC_INACTIVE). 
     In RRC connected  602 , the UE has an established RRC context and may have at least one RRC connection with a base station. The base station may be similar to one of the one or more base stations included in the RAN  104  depicted in  FIG. 1A , one of the gNBs  160  or ng-eNBs  162  depicted in  FIG. 1B , the gNB  220  depicted in  FIG. 2A  and  FIG. 2B , or any other base station described in the present disclosure. The base station with which the UE is connected may have the RRC context for the UE. The RRC context, referred to as the UE context, may comprise parameters for communication between the UE and the base station. These parameters may include, for example: one or more AS contexts; one or more radio link configuration parameters; bearer configuration information (e.g., relating to a data radio bearer, signaling radio bearer, logical channel, QoS flow, and/or PDU session); security information; and/or PHY, MAC, RLC, PDCP, and/or SDAP layer configuration information. While in RRC connected  602 , mobility of the UE may be managed by the RAN (e.g., the RAN  104  or the NG-RAN  154 ). The UE may measure the signal levels (e.g., reference signal levels) from a serving cell and neighboring cells and report these measurements to the base station currently serving the UE. The UE&#39;s serving base station may request a handover to a cell of one of the neighboring base stations based on the reported measurements. The RRC state may transition from RRC connected  602  to RRC idle  604  through a connection release procedure  608  or to RRC inactive  606  through a connection inactivation procedure  610 . 
     In RRC idle  604 , an RRC context may not be established for the UE. In RRC idle  604 , the UE may not have an RRC connection with the base station. While in RRC idle  604 , the UE may be in a sleep state for the majority of the time (e.g., to conserve battery power). The UE may wake up periodically (e.g., once in every discontinuous reception cycle) to monitor for paging messages from the RAN. Mobility of the UE may be managed by the UE through a procedure known as cell reselection. The RRC state may transition from RRC idle  604  to RRC connected  602  through a connection establishment procedure  612 , which may involve a random access procedure as discussed in greater detail below. 
     In RRC inactive  606 , the RRC context previously established is maintained in the UE and the base station. This allows for a fast transition to RRC connected  602  with reduced signaling overhead as compared to the transition from RRC idle  604  to RRC connected  602 . While in RRC inactive  606 , the UE may be in a sleep state and mobility of the UE may be managed by the UE through cell reselection. The RRC state may transition from RRC inactive  606  to RRC connected  602  through a connection resume procedure  614  or to RRC idle  604  though a connection release procedure  616  that may be the same as or similar to connection release procedure  608 . 
     An RRC state may be associated with a mobility management mechanism. In RRC idle  604  and RRC inactive  606 , mobility is managed by the UE through cell reselection. The purpose of mobility management in RRC idle  604  and RRC inactive  606  is to allow the network to be able to notify the UE of an event via a paging message without having to broadcast the paging message over the entire mobile communications network. The mobility management mechanism used in RRC idle  604  and RRC inactive  606  may allow the network to track the UE on a cell-group level so that the paging message may be broadcast over the cells of the cell group that the UE currently resides within instead of the entire mobile communication network. The mobility management mechanisms for RRC idle  604  and RRC inactive  606  track the UE on a cell-group level. They may do so using different granularities of grouping. For example, there may be three levels of cell-grouping granularity: individual cells; cells within a RAN area identified by a RAN area identifier (RAI); and cells within a group of RAN areas, referred to as a tracking area and identified by a tracking area identifier (TAI). 
     Tracking areas may be used to track the UE at the CN level. The CN (e.g., the CN  102  or the 5G-CN  152 ) may provide the UE with a list of TAIs associated with a UE registration area. If the UE moves, through cell reselection, to a cell associated with a TAI not included in the list of TAIs associated with the UE registration area, the UE may perform a registration update with the CN to allow the CN to update the UE&#39;s location and provide the UE with a new the UE registration area. 
     RAN areas may be used to track the UE at the RAN level. For a UE in RRC inactive  606  state, the UE may be assigned a RAN notification area. A RAN notification area may comprise one or more cell identities, a list of RAIs, or a list of TAIs. In an example, a base station may belong to one or more RAN notification areas. In an example, a cell may belong to one or more RAN notification areas. If the UE moves, through cell reselection, to a cell not included in the RAN notification area assigned to the UE, the UE may perform a notification area update with the RAN to update the UE&#39;s RAN notification area. 
     A base station storing an RRC context for a UE or a last serving base station of the UE may be referred to as an anchor base station. An anchor base station may maintain an RRC context for the UE at least during a period of time that the UE stays in a RAN notification area of the anchor base station and/or during a period of time that the UE stays in RRC inactive  606 . 
     A gNB, such as gNBs  160  in  FIG. 1B , may be split in two parts: a central unit (gNB-CU), and one or more distributed units (gNB-DU). A gNB-CU may be coupled to one or more gNB-DUs using an F1 interface. The gNB-CU may comprise the RRC, the PDCP, and the SDAP. A gNB-DU may comprise the RLC, the MAC, and the PHY. 
     In NR, the physical signals and physical channels (discussed with respect to  FIG. 5A  and  FIG. 5B ) may be mapped onto orthogonal frequency divisional multiplexing (OFDM) symbols. OFDM is a multicarrier communication scheme that transmits data over F orthogonal subcarriers (or tones). Before transmission, the data may be mapped to a series of complex symbols (e.g., M-quadrature amplitude modulation (M-QAM) or M-phase shift keying (M-PSK) symbols), referred to as source symbols, and divided into F parallel symbol streams. The F parallel symbol streams may be treated as though they are in the frequency domain and used as inputs to an Inverse Fast Fourier Transform (IFFT) block that transforms them into the time domain. The IFFT block may take in F source symbols at a time, one from each of the F parallel symbol streams, and use each source symbol to modulate the amplitude and phase of one of F sinusoidal basis functions that correspond to the F orthogonal subcarriers. The output of the IFFT block may be F time-domain samples that represent the summation of the F orthogonal subcarriers. The F time-domain samples may form a single OFDM symbol. After some processing (e.g., addition of a cyclic prefix) and up-conversion, an OFDM symbol provided by the IFFT block may be transmitted over the air interface on a carrier frequency. The F parallel symbol streams may be mixed using an FFT block before being processed by the IFFT block. This operation produces Discrete Fourier Transform (DFT)-precoded OFDM symbols and may be used by UEs in the uplink to reduce the peak to average power ratio (PAPR). Inverse processing may be performed on the OFDM symbol at a receiver using an FFT block to recover the data mapped to the source symbols. 
       FIG. 7  illustrates an example configuration of an NR frame into which OFDM symbols are grouped. An NR frame may be identified by a system frame number (SFN). The SFN may repeat with a period of 1024 frames. As illustrated, one NR frame may be 10 milliseconds (ms) in duration and may include 10 subframes that are 1 ms in duration. A subframe may be divided into slots that include, for example, 14 OFDM symbols per slot. 
     The duration of a slot may depend on the numerology used for the OFDM symbols of the slot. In NR, a flexible numerology is supported to accommodate different cell deployments (e.g., cells with carrier frequencies below 1 GHz up to cells with carrier frequencies in the mm-wave range). A numerology may be defined in terms of subcarrier spacing and cyclic prefix duration. For a numerology in NR, subcarrier spacings may be scaled up by powers of two from a baseline subcarrier spacing of 15 kHz, and cyclic prefix durations may be scaled down by powers of two from a baseline cyclic prefix duration of 4.7 μs. For example, NR defines numerologies with the following subcarrier spacing/cyclic prefix duration combinations: 15 kHz/4.7 μs; 30 kHz/2.3 μs; 60 kHz/1.2 μs; 120 kHz/0.59 μs; and 240 kHz/0.29 μs. 
     A slot may have a fixed number of OFDM symbols (e.g., 14 OFDM symbols). A numerology with a higher subcarrier spacing has a shorter slot duration and, correspondingly, more slots per subframe.  FIG. 7  illustrates this numerology-dependent slot duration and slots-per-subframe transmission structure (the numerology with a subcarrier spacing of 240 kHz is not shown in  FIG. 7  for ease of illustration). A subframe in NR may be used as a numerology-independent time reference, while a slot may be used as the unit upon which uplink and downlink transmissions are scheduled. To support low latency, scheduling in NR may be decoupled from the slot duration and start at any OFDM symbol and last for as many symbols as needed for a transmission. These partial slot transmissions may be referred to as mini-slot or subslot transmissions. 
       FIG. 8  illustrates an example configuration of a slot in the time and frequency domain for an NR carrier. The slot includes resource elements (REs) and resource blocks (RBs). An RE is the smallest physical resource in NR. An RE spans one OFDM symbol in the time domain by one subcarrier in the frequency domain as shown in  FIG. 8 . An RB spans twelve consecutive REs in the frequency domain as shown in  FIG. 8 . An NR carrier may be limited to a width of 275 RBs or 275×12=3300 subcarriers. Such a limitation, if used, may limit the NR carrier to 50, 100, 200, and 400 MHz for subcarrier spacings of 15, 30, 60, and 120 kHz, respectively, where the 400 MHz bandwidth may be set based on a 400 MHz per carrier bandwidth limit. 
       FIG. 8  illustrates a single numerology being used across the entire bandwidth of the NR carrier. In other example configurations, multiple numerologies may be supported on the same carrier. 
     NR may support wide carrier bandwidths (e.g., up to 400 MHz for a subcarrier spacing of 120 kHz). Not all UEs may be able to receive the full carrier bandwidth (e.g., due to hardware limitations). Also, receiving the full carrier bandwidth may be prohibitive in terms of UE power consumption. In an example, to reduce power consumption and/or for other purposes, a UE may adapt the size of the UE&#39;s receive bandwidth based on the amount of traffic the UE is scheduled to receive. This is referred to as bandwidth adaptation. 
     NR defines bandwidth parts (BWPs) to support UEs not capable of receiving the full carrier bandwidth and to support bandwidth adaptation. In an example, a BWP may be defined by a subset of contiguous RBs on a carrier. A UE may be configured (e.g., via RRC layer) with one or more downlink BWPs and one or more uplink BWPs per serving cell (e.g., up to four downlink BWPs and up to four uplink BWPs per serving cell). At a given time, one or more of the configured BWPs for a serving cell may be active. These one or more BWPs may be referred to as active BWPs of the serving cell. When a serving cell is configured with a secondary uplink carrier, the serving cell may have one or more first active BWPs in the uplink carrier and one or more second active BWPs in the secondary uplink carrier. 
     For unpaired spectra, a downlink BWP from a set of configured downlink BWPs may be linked with an uplink BWP from a set of configured uplink BWPs if a downlink BWP index of the downlink BWP and an uplink BWP index of the uplink BWP are the same. For unpaired spectra, a UE may expect that a center frequency for a downlink BWP is the same as a center frequency for an uplink BWP. 
     For a downlink BWP in a set of configured downlink BWPs on a primary cell (PCell), a base station may configure a UE with one or more control resource sets (CORESETs) for at least one search space. A search space is a set of locations in the time and frequency domains where the UE may find control information. The search space may be a UE-specific search space or a common search space (potentially usable by a plurality of UEs). For example, a base station may configure a UE with a common search space, on a PCell or on a primary secondary cell (PSCell), in an active downlink BWP. 
     For an uplink BWP in a set of configured uplink BWPs, a BS may configure a UE with one or more resource sets for one or more PUCCH transmissions. A UE may receive downlink receptions (e.g., PDCCH or PDSCH) in a downlink BWP according to a configured numerology (e.g., subcarrier spacing and cyclic prefix duration) for the downlink BWP. The UE may transmit uplink transmissions (e.g., PUCCH or PUSCH) in an uplink BWP according to a configured numerology (e.g., subcarrier spacing and cyclic prefix length for the uplink BWP). 
     One or more BWP indicator fields may be provided in Downlink Control Information (DCI). A value of a BWP indicator field may indicate which BWP in a set of configured BWPs is an active downlink BWP for one or more downlink receptions. The value of the one or more BWP indicator fields may indicate an active uplink BWP for one or more uplink transmissions. 
     A base station may semi-statically configure a UE with a default downlink BWP within a set of configured downlink BWPs associated with a PCell. If the base station does not provide the default downlink BWP to the UE, the default downlink BWP may be an initial active downlink BWP. The UE may determine which BWP is the initial active downlink BWP based on a CORESET configuration obtained using the PBCH. 
     A base station may configure a UE with a BWP inactivity timer value for a PCell. The UE may start or restart a BWP inactivity timer at any appropriate time. For example, the UE may start or restart the BWP inactivity timer (a) when the UE detects a DCI indicating an active downlink BWP other than a default downlink BWP for a paired spectra operation; or (b) when a UE detects a DCI indicating an active downlink BWP or active uplink BWP other than a default downlink BWP or uplink BWP for an unpaired spectra operation. If the UE does not detect DCI during an interval of time (e.g., 1 ms or 0.5 ms), the UE may run the BWP inactivity timer toward expiration (for example, increment from zero to the BWP inactivity timer value, or decrement from the BWP inactivity timer value to zero). When the BWP inactivity timer expires, the UE may switch from the active downlink BWP to the default downlink BWP. 
     In an example, a base station may semi-statically configure a UE with one or more BWPs. A UE may switch an active BWP from a first BWP to a second BWP in response to receiving a DCI indicating the second BWP as an active BWP and/or in response to an expiry of the BWP inactivity timer (e.g., if the second BWP is the default BWP). 
     Downlink and uplink BWP switching (where BWP switching refers to switching from a currently active BWP to a not currently active BWP) may be performed independently in paired spectra. In unpaired spectra, downlink and uplink BWP switching may be performed simultaneously. Switching between configured BWPs may occur based on RRC signaling, DCI, expiration of a BWP inactivity timer, and/or an initiation of random access. 
       FIG. 9  illustrates an example of bandwidth adaptation using three configured BWPs for an NR carrier. A UE configured with the three BWPs may switch from one BWP to another BWP at a switching point. In the example illustrated in  FIG. 9 , the BWPs include: a BWP  902  with a bandwidth of 40 MHz and a subcarrier spacing of 15 kHz; a BWP  904  with a bandwidth of 10 MHz and a subcarrier spacing of 15 kHz; and a BWP  906  with a bandwidth of 20 MHz and a subcarrier spacing of 60 kHz. The BWP  902  may be an initial active BWP, and the BWP  904  may be a default BWP. The UE may switch between BWPs at switching points. In the example of  FIG. 9 , the UE may switch from the BWP  902  to the BWP  904  at a switching point  908 . The switching at the switching point  908  may occur for any suitable reason, for example, in response to an expiry of a BWP inactivity timer (indicating switching to the default BWP) and/or in response to receiving a DCI indicating BWP  904  as the active BWP. The UE may switch at a switching point  910  from active BWP  904  to BWP  906  in response receiving a DCI indicating BWP  906  as the active BWP. The UE may switch at a switching point  912  from active BWP  906  to BWP  904  in response to an expiry of a BWP inactivity timer and/or in response receiving a DCI indicating BWP  904  as the active BWP. The UE may switch at a switching point  914  from active BWP  904  to BWP  902  in response receiving a DCI indicating BWP  902  as the active BWP. 
     If a UE is configured for a secondary cell with a default downlink BWP in a set of configured downlink BWPs and a timer value, UE procedures for switching BWPs on a secondary cell may be the same/similar as those on a primary cell. For example, the UE may use the timer value and the default downlink BWP for the secondary cell in the same/similar manner as the UE would use these values for a primary cell. 
     To provide for greater data rates, two or more carriers can be aggregated and simultaneously transmitted to/from the same UE using carrier aggregation (CA). The aggregated carriers in CA may be referred to as component carriers (CCs). When CA is used, there are a number of serving cells for the UE, one for a CC. The CCs may have three configurations in the frequency domain. 
       FIG. 10A  illustrates the three CA configurations with two CCs. In the intraband, contiguous configuration  1002 , the two CCs are aggregated in the same frequency band (frequency band A) and are located directly adjacent to each other within the frequency band. In the intraband, non-contiguous configuration  1004 , the two CCs are aggregated in the same frequency band (frequency band A) and are separated in the frequency band by a gap. In the interband configuration  1006 , the two CCs are located in frequency bands (frequency band A and frequency band B). 
     In an example, up to 32 CCs may be aggregated. The aggregated CCs may have the same or different bandwidths, subcarrier spacing, and/or duplexing schemes (TDD or FDD). A serving cell for a UE using CA may have a downlink CC. For FDD, one or more uplink CCs may be optionally configured for a serving cell. The ability to aggregate more downlink carriers than uplink carriers may be useful, for example, when the UE has more data traffic in the downlink than in the uplink. 
     When CA is used, one of the aggregated cells for a UE may be referred to as a primary cell (PCell). The PCell may be the serving cell that the UE initially connects to at RRC connection establishment, reestablishment, and/or handover. The PCell may provide the UE with NAS mobility information and the security input. UEs may have different PCells. In the downlink, the carrier corresponding to the PCell may be referred to as the downlink primary CC (DL PCC). In the uplink, the carrier corresponding to the PCell may be referred to as the uplink primary CC (UL PCC). The other aggregated cells for the UE may be referred to as secondary cells (SCells). In an example, the SCells may be configured after the PCell is configured for the UE. For example, an SCell may be configured through an RRC Connection Reconfiguration procedure. In the downlink, the carrier corresponding to an SCell may be referred to as a downlink secondary CC (DL SCC). In the uplink, the carrier corresponding to the SCell may be referred to as the uplink secondary CC (UL SCC). 
     Configured SCells for a UE may be activated and deactivated based on, for example, traffic and channel conditions. Deactivation of an SCell may mean that PDCCH and PDSCH reception on the SCell is stopped and PUSCH, SRS, and CQI transmissions on the SCell are stopped. Configured SCells may be activated and deactivated using a MAC CE with respect to  FIG. 4B . For example, a MAC CE may use a bitmap (e.g., one bit per SCell) to indicate which SCells (e.g., in a subset of configured SCells) for the UE are activated or deactivated. Configured SCells may be deactivated in response to an expiration of an SCell deactivation timer (e.g., one SCell deactivation timer per SCell). 
     Downlink control information, such as scheduling assignments and scheduling grants, for a cell may be transmitted on the cell corresponding to the assignments and grants, which is known as self-scheduling. The DCI for the cell may be transmitted on another cell, which is known as cross-carrier scheduling. Uplink control information (e.g., HARQ acknowledgments and channel state feedback, such as CQI, PMI, and/or RI) for aggregated cells may be transmitted on the PUCCH of the PCell. For a larger number of aggregated downlink CCs, the PUCCH of the PCell may become overloaded. Cells may be divided into multiple PUCCH groups. 
       FIG. 10B  illustrates an example of how aggregated cells may be configured into one or more PUCCH groups. A PUCCH group  1010  and a PUCCH group  1050  may include one or more downlink CCs, respectively. In the example of  FIG. 10B , the PUCCH group  1010  includes three downlink CCs: a PCell  1011 , an SCell  1012 , and an SCell  1013 . The PUCCH group  1050  includes three downlink CCs in the present example: a PCell  1051 , an SCell  1052 , and an SCell  1053 . One or more uplink CCs may be configured as a PCell  1021 , an SCell  1022 , and an SCell  1023 . One or more other uplink CCs may be configured as a primary Scell (PSCell)  1061 , an SCell  1062 , and an SCell  1063 . Uplink control information (UCI) related to the downlink CCs of the PUCCH group  1010 , shown as UCI  1031 , UCI  1032 , and UCI  1033 , may be transmitted in the uplink of the PCell  1021 . Uplink control information (UCI) related to the downlink CCs of the PUCCH group  1050 , shown as UCI  1071 , UCI  1072 , and UCI  1073 , may be transmitted in the uplink of the PSCell  1061 . In an example, if the aggregated cells depicted in  FIG. 10B  were not divided into the PUCCH group  1010  and the PUCCH group  1050 , a single uplink PCell to transmit UCI relating to the downlink CCs, and the PCell may become overloaded. By dividing transmissions of UCI between the PCell  1021  and the PSCell  1061 , overloading may be prevented. 
     A cell, comprising a downlink carrier and optionally an uplink carrier, may be assigned with a physical cell ID and a cell index. The physical cell ID or the cell index may identify a downlink carrier and/or an uplink carrier of the cell, for example, depending on the context in which the physical cell ID is used. A physical cell ID may be determined using a synchronization signal transmitted on a downlink component carrier. A cell index may be determined using RRC messages. In the disclosure, a physical cell ID may be referred to as a carrier ID, and a cell index may be referred to as a carrier index. For example, when the disclosure refers to a first physical cell ID for a first downlink carrier, the disclosure may mean the first physical cell ID is for a cell comprising the first downlink carrier. The same/similar concept may apply to, for example, a carrier activation. When the disclosure indicates that a first carrier is activated, the specification may mean that a cell comprising the first carrier is activated. 
     In CA, a multi-carrier nature of a PHY may be exposed to a MAC. In an example, a HARQ entity may operate on a serving cell. A transport block may be generated per assignment/grant per serving cell. A transport block and potential HARQ retransmissions of the transport block may be mapped to a serving cell. 
     In the downlink, a base station may transmit (e.g., unicast, multicast, and/or broadcast) one or more Reference Signals (RSs) to a UE (e.g., PSS, SSS, CSI-RS, DMRS, and/or PT-RS, as shown in  FIG. 5A ). In the uplink, the UE may transmit one or more RSs to the base station (e.g., DMRS, PT-RS, and/or SRS, as shown in  FIG. 5B ). The PSS and the SSS may be transmitted by the base station and used by the UE to synchronize the UE to the base station. The PSS and the SSS may be provided in a synchronization signal (SS)/physical broadcast channel (PBCH) block that includes the PSS, the SSS, and the PBCH. The base station may periodically transmit a burst of SS/PBCH blocks. 
       FIG. 11A  illustrates an example of an SS/PBCH block&#39;s structure and location. A burst of SS/PBCH blocks may include one or more SS/PBCH blocks (e.g., 4 SS/PBCH blocks, as shown in  FIG. 11A ). Bursts may be transmitted periodically (e.g., every 2 frames or 20 ms). A burst may be restricted to a half-frame (e.g., a first half-frame having a duration of 5 ms). It will be understood that  FIG. 11A  is an example, and that these parameters (number of SS/PBCH blocks per burst, periodicity of bursts, position of burst within the frame) may be configured based on, for example: a carrier frequency of a cell in which the SS/PBCH block is transmitted; a numerology or subcarrier spacing of the cell; a configuration by the network (e.g., using RRC signaling); or any other suitable factor. In an example, the UE may assume a subcarrier spacing for the SS/PBCH block based on the carrier frequency being monitored, unless the radio network configured the UE to assume a different subcarrier spacing. 
     The SS/PBCH block may span one or more OFDM symbols in the time domain (e.g., 4 OFDM symbols, as shown in the example of  FIG. 11A ) and may span one or more subcarriers in the frequency domain (e.g., 240 contiguous subcarriers). The PSS, the SSS, and the PBCH may have a common center frequency. The PSS may be transmitted first and may span, for example, 1 OFDM symbol and 127 subcarriers. The SSS may be transmitted after the PSS (e.g., two symbols later) and may span 1 OFDM symbol and 127 subcarriers. The PBCH may be transmitted after the PSS (e.g., across the next 3 OFDM symbols) and may span  240  subcarriers. 
     The location of the SS/PBCH block in the time and frequency domains may not be known to the UE (e.g., if the UE is searching for the cell). To find and select the cell, the UE may monitor a carrier for the PSS. For example, the UE may monitor a frequency location within the carrier. If the PSS is not found after a certain duration (e.g., 20 ms), the UE may search for the PSS at a different frequency location within the carrier, as indicated by a synchronization raster. If the PSS is found at a location in the time and frequency domains, the UE may determine, based on a known structure of the SS/PBCH block, the locations of the SSS and the PBCH, respectively. The SS/PBCH block may be a cell-defining SS block (CD-SSB). In an example, a primary cell may be associated with a CD-SSB. The CD-SSB may be located on a synchronization raster. In an example, a cell selection/search and/or reselection may be based on the CD-SSB. 
     The SS/PBCH block may be used by the UE to determine one or more parameters of the cell. For example, the UE may determine a physical cell identifier (PCI) of the cell based on the sequences of the PSS and the SSS, respectively. The UE may determine a location of a frame boundary of the cell based on the location of the SS/PBCH block. For example, the SS/PBCH block may indicate that it has been transmitted in accordance with a transmission pattern, wherein a SS/PBCH block in the transmission pattern is a known distance from the frame boundary. 
     The PBCH may use a QPSK modulation and may use forward error correction (FEC). The FEC may use polar coding. One or more symbols spanned by the PBCH may carry one or more DMRSs for demodulation of the PBCH. The PBCH may include an indication of a current system frame number (SFN) of the cell and/or a SS/PBCH block timing index. These parameters may facilitate time synchronization of the UE to the base station. The PBCH may include a master information block (MIB) used to provide the UE with one or more parameters. The MIB may be used by the UE to locate remaining minimum system information (RMSI) associated with the cell. The RMSI may include a System Information Block Type 1 (SIB1). The SIB1 may contain information needed by the UE to access the cell. The UE may use one or more parameters of the MIB to monitor PDCCH, which may be used to schedule PDSCH. The PDSCH may include the SIB1. The SIB1 may be decoded using parameters provided in the MIB. The PBCH may indicate an absence of SIB1. Based on the PBCH indicating the absence of SIB1, the UE may be pointed to a frequency. The UE may search for an SS/PBCH block at the frequency to which the UE is pointed. 
     The UE may assume that one or more SS/PBCH blocks transmitted with a same SS/PBCH block index are quasi co-located (QCLed) (e.g., having the same/similar Doppler spread, Doppler shift, average gain, average delay, and/or spatial Rx parameters). The UE may not assume QCL for SS/PBCH block transmissions having different SS/PBCH block indices. 
     SS/PBCH blocks (e.g., those within a half-frame) may be transmitted in spatial directions (e.g., using different beams that span a coverage area of the cell). In an example, a first SS/PBCH block may be transmitted in a first spatial direction using a first beam, and a second SS/PBCH block may be transmitted in a second spatial direction using a second beam. 
     In an example, within a frequency span of a carrier, a base station may transmit a plurality of SS/PBCH blocks. In an example, a first PCI of a first SS/PBCH block of the plurality of SS/PBCH blocks may be different from a second PCI of a second SS/PBCH block of the plurality of SS/PBCH blocks. The PCIs of SS/PBCH blocks transmitted in different frequency locations may be different or the same. 
     The CSI-RS may be transmitted by the base station and used by the UE to acquire channel state information (CSI). The base station may configure the UE with one or more CSI-RSs for channel estimation or any other suitable purpose. The base station may configure a UE with one or more of the same/similar CSI-RSs. The UE may measure the one or more CSI-RSs. The UE may estimate a downlink channel state and/or generate a CSI report based on the measuring of the one or more downlink CSI-RSs. The UE may provide the CSI report to the base station. The base station may use feedback provided by the UE (e.g., the estimated downlink channel state) to perform link adaptation. 
     The base station may semi-statically configure the UE with one or more CSI-RS resource sets. A CSI-RS resource may be associated with a location in the time and frequency domains and a periodicity. The base station may selectively activate and/or deactivate a CSI-RS resource. The base station may indicate to the UE that a CSI-RS resource in the CSI-RS resource set is activated and/or deactivated. 
     The base station may configure the UE to report CSI measurements. The base station may configure the UE to provide CSI reports periodically, aperiodically, or semi-persistently. For periodic CSI reporting, the UE may be configured with a timing and/or periodicity of a plurality of CSI reports. For aperiodic CSI reporting, the base station may request a CSI report. For example, the base station may command the UE to measure a configured CSI-RS resource and provide a CSI report relating to the measurements. For semi-persistent CSI reporting, the base station may configure the UE to transmit periodically, and selectively activate or deactivate the periodic reporting. The base station may configure the UE with a CSI-RS resource set and CSI reports using RRC signaling. 
     The CSI-RS configuration may comprise one or more parameters indicating, for example, up to 32 antenna ports. The UE may be configured to employ the same OFDM symbols for a downlink CSI-RS and a control resource set (CORESET) when the downlink CSI-RS and CORESET are spatially QCLed and resource elements associated with the downlink CSI-RS are outside of the physical resource blocks (PRBs) configured for the CORESET. The UE may be configured to employ the same OFDM symbols for downlink CSI-RS and SS/PBCH blocks when the downlink CSI-RS and SS/PBCH blocks are spatially QCLed and resource elements associated with the downlink CSI-RS are outside of PRBs configured for the SS/PBCH blocks. 
     Downlink DMRSs may be transmitted by a base station and used by a UE for channel estimation. For example, the downlink DMRS may be used for coherent demodulation of one or more downlink physical channels (e.g., PDSCH). An NR network may support one or more variable and/or configurable DMRS patterns for data demodulation. At least one downlink DMRS configuration may support a front-loaded DMRS pattern. A front-loaded DMRS may be mapped over one or more OFDM symbols (e.g., one or two adjacent OFDM symbols). A base station may semi-statically configure the UE with a number (e.g. a maximum number) of front-loaded DMRS symbols for PDSCH. A DMRS configuration may support one or more DMRS ports. For example, for single user-MIMO, a DMRS configuration may support up to eight orthogonal downlink DMRS ports per UE. For multiuser-MIMO, a DMRS configuration may support up to 4 orthogonal downlink DMRS ports per UE. A radio network may support (e.g., at least for CP-OFDM) a common DMRS structure for downlink and uplink, wherein a DMRS location, a DMRS pattern, and/or a scrambling sequence may be the same or different. The base station may transmit a downlink DMRS and a corresponding PDSCH using the same precoding matrix. The UE may use the one or more downlink DMRSs for coherent demodulation/channel estimation of the PDSCH. 
     In an example, a transmitter (e.g., a base station) may use a precoder matrices for a part of a transmission bandwidth. For example, the transmitter may use a first precoder matrix for a first bandwidth and a second precoder matrix for a second bandwidth. The first precoder matrix and the second precoder matrix may be different based on the first bandwidth being different from the second bandwidth. The UE may assume that a same precoding matrix is used across a set of PRBs. The set of PRBs may be denoted as a precoding resource block group (PRG). 
     A PDSCH may comprise one or more layers. The UE may assume that at least one symbol with DMRS is present on a layer of the one or more layers of the PDSCH. A higher layer may configure up to 3 DMRSs for the PDSCH. 
     Downlink PT-RS may be transmitted by a base station and used by a UE for phase-noise compensation. Whether a downlink PT-RS is present or not may depend on an RRC configuration. The presence and/or pattern of the downlink PT-RS may be configured on a UE-specific basis using a combination of RRC signaling and/or an association with one or more parameters employed for other purposes (e.g., modulation and coding scheme (MCS)), which may be indicated by DCI. When configured, a dynamic presence of a downlink PT-RS may be associated with one or more DCI parameters comprising at least MCS. An NR network may support a plurality of PT-RS densities defined in the time and/or frequency domains. When present, a frequency domain density may be associated with at least one configuration of a scheduled bandwidth. The UE may assume a same precoding for a DMRS port and a PT-RS port. A number of PT-RS ports may be fewer than a number of DMRS ports in a scheduled resource. Downlink PT-RS may be confined in the scheduled time/frequency duration for the UE. Downlink PT-RS may be transmitted on symbols to facilitate phase tracking at the receiver. 
     The UE may transmit an uplink DMRS to a base station for channel estimation. For example, the base station may use the uplink DMRS for coherent demodulation of one or more uplink physical channels. For example, the UE may transmit an uplink DMRS with a PUSCH and/or a PUCCH. The uplink DM-RS may span a range of frequencies that is similar to a range of frequencies associated with the corresponding physical channel. The base station may configure the UE with one or more uplink DMRS configurations. At least one DMRS configuration may support a front-loaded DMRS pattern. The front-loaded DMRS may be mapped over one or more OFDM symbols (e.g., one or two adjacent OFDM symbols). One or more uplink DMRSs may be configured to transmit at one or more symbols of a PUSCH and/or a PUCCH. The base station may semi-statically configure the UE with a number (e.g. maximum number) of front-loaded DMRS symbols for the PUSCH and/or the PUCCH, which the UE may use to schedule a single-symbol DMRS and/or a double-symbol DMRS. An NR network may support (e.g., for cyclic prefix orthogonal frequency division multiplexing (CP-OFDM)) a common DMRS structure for downlink and uplink, wherein a DMRS location, a DMRS pattern, and/or a scrambling sequence for the DMRS may be the same or different. 
     A PUSCH may comprise one or more layers, and the UE may transmit at least one symbol with DMRS present on a layer of the one or more layers of the PUSCH. In an example, a higher layer may configure up to three DMRSs for the PUSCH. 
     Uplink PT-RS (which may be used by a base station for phase tracking and/or phase-noise compensation) may or may not be present depending on an RRC configuration of the UE. The presence and/or pattern of uplink PT-RS may be configured on a UE-specific basis by a combination of RRC signaling and/or one or more parameters employed for other purposes (e.g., Modulation and Coding Scheme (MCS)), which may be indicated by DCI. When configured, a dynamic presence of uplink PT-RS may be associated with one or more DCI parameters comprising at least MCS. A radio network may support a plurality of uplink PT-RS densities defined in time/frequency domain. When present, a frequency domain density may be associated with at least one configuration of a scheduled bandwidth. The UE may assume a same precoding for a DMRS port and a PT-RS port. A number of PT-RS ports may be fewer than a number of DMRS ports in a scheduled resource. For example, uplink PT-RS may be confined in the scheduled time/frequency duration for the UE. 
     SRS may be transmitted by a UE to a base station for channel state estimation to support uplink channel dependent scheduling and/or link adaptation. SRS transmitted by the UE may allow a base station to estimate an uplink channel state at one or more frequencies. A scheduler at the base station may employ the estimated uplink channel state to assign one or more resource blocks for an uplink PUSCH transmission from the UE. The base station may semi-statically configure the UE with one or more SRS resource sets. For an SRS resource set, the base station may configure the UE with one or more SRS resources. An SRS resource set applicability may be configured by a higher layer (e.g., RRC) parameter. For example, when a higher layer parameter indicates beam management, an SRS resource in a SRS resource set of the one or more SRS resource sets (e.g., with the same/similar time domain behavior, periodic, aperiodic, and/or the like) may be transmitted at a time instant (e.g., simultaneously). The UE may transmit one or more SRS resources in SRS resource sets. An NR network may support aperiodic, periodic and/or semi-persistent SRS transmissions. The UE may transmit SRS resources based on one or more trigger types, wherein the one or more trigger types may comprise higher layer signaling (e.g., RRC) and/or one or more DCI formats. In an example, at least one DCI format may be employed for the UE to select at least one of one or more configured SRS resource sets. An SRS trigger type 0 may refer to an SRS triggered based on a higher layer signaling. An SRS trigger type 1 may refer to an SRS triggered based on one or more DCI formats. In an example, when PUSCH and SRS are transmitted in a same slot, the UE may be configured to transmit SRS after a transmission of a PUSCH and a corresponding uplink DMRS. 
     The base station may semi-statically configure the UE with one or more SRS configuration parameters indicating at least one of following: a SRS resource configuration identifier; a number of SRS ports; time domain behavior of an SRS resource configuration (e.g., an indication of periodic, semi-persistent, or aperiodic SRS); slot, mini-slot, and/or subframe level periodicity; offset for a periodic and/or an aperiodic SRS resource; a number of OFDM symbols in an SRS resource; a starting OFDM symbol of an SRS resource; an SRS bandwidth; a frequency hopping bandwidth; a cyclic shift; and/or an SRS sequence ID. 
     An antenna port is defined such that the channel over which a symbol on the antenna port is conveyed can be inferred from the channel over which another symbol on the same antenna port is conveyed. If a first symbol and a second symbol are transmitted on the same antenna port, the receiver may infer the channel (e.g., fading gain, multipath delay, and/or the like) for conveying the second symbol on the antenna port, from the channel for conveying the first symbol on the antenna port. A first antenna port and a second antenna port may be referred to as quasi co-located (QCLed) if one or more large-scale properties of the channel over which a first symbol on the first antenna port is conveyed may be inferred from the channel over which a second symbol on a second antenna port is conveyed. The one or more large-scale properties may comprise at least one of: a delay spread; a Doppler spread; a Doppler shift; an average gain; an average delay; and/or spatial Receiving (Rx) parameters. 
     Channels that use beamforming require beam management. Beam management may comprise beam measurement, beam selection, and beam indication. A beam may be associated with one or more reference signals. For example, a beam may be identified by one or more beamformed reference signals. The UE may perform downlink beam measurement based on downlink reference signals (e.g., a channel state information reference signal (CSI-RS)) and generate a beam measurement report. The UE may perform the downlink beam measurement procedure after an RRC connection is set up with a base station. 
       FIG. 11B  illustrates an example of channel state information reference signals (CSI-RSs) that are mapped in the time and frequency domains. A square shown in  FIG. 11B  may span a resource block (RB) within a bandwidth of a cell. A base station may transmit one or more RRC messages comprising CSI-RS resource configuration parameters indicating one or more CSI-RSs. One or more of the following parameters may be configured by higher layer signaling (e.g., RRC and/or MAC signaling) for a CSI-RS resource configuration: a CSI-RS resource configuration identity, a number of CSI-RS ports, a CSI-RS configuration (e.g., symbol and resource element (RE) locations in a subframe), a CSI-RS subframe configuration (e.g., subframe location, offset, and periodicity in a radio frame), a CSI-RS power parameter, a CSI-RS sequence parameter, a code division multiplexing (CDM) type parameter, a frequency density, a transmission comb, quasi co-location (QCL) parameters (e.g., QCL-scramblingidentity, crs-portscount, mbsfn-subframeconfiglist, csi-rs-configZPid, qcl-csi-rs-configNZPid), and/or other radio resource parameters. 
     The three beams illustrated in  FIG. 11B  may be configured for a UE in a UE-specific configuration. Three beams are illustrated in  FIG. 11B  (beam #1, beam #2, and beam #3), more or fewer beams may be configured. Beam #1 may be allocated with CSI-RS  1101  that may be transmitted in one or more subcarriers in an RB of a first symbol. Beam #2 may be allocated with CSI-RS  1102  that may be transmitted in one or more subcarriers in an RB of a second symbol. Beam #3 may be allocated with CSI-RS  1103  that may be transmitted in one or more subcarriers in an RB of a third symbol. By using frequency division multiplexing (FDM), a base station may use other subcarriers in a same RB (for example, those that are not used to transmit CSI-RS  1101 ) to transmit another CSI-RS associated with a beam for another UE. By using time domain multiplexing (TDM), beams used for the UE may be configured such that beams for the UE use symbols from beams of other UEs. 
     CSI-RSs such as those illustrated in  FIG. 11B  (e.g., CSI-RS  1101 ,  1102 ,  1103 ) may be transmitted by the base station and used by the UE for one or more measurements. For example, the UE may measure a reference signal received power (RSRP) of configured CSI-RS resources. The base station may configure the UE with a reporting configuration and the UE may report the RSRP measurements to a network (for example, via one or more base stations) based on the reporting configuration. In an example, the base station may determine, based on the reported measurement results, one or more transmission configuration indication (TCI) states comprising a number of reference signals. In an example, the base station may indicate one or more TCI states to the UE (e.g., via RRC signaling, a MAC CE, and/or a DCI). The UE may receive a downlink transmission with a receive (Rx) beam determined based on the one or more TCI states. In an example, the UE may or may not have a capability of beam correspondence. If the UE has the capability of beam correspondence, the UE may determine a spatial domain filter of a transmit (Tx) beam based on a spatial domain filter of the corresponding Rx beam. If the UE does not have the capability of beam correspondence, the UE may perform an uplink beam selection procedure to determine the spatial domain filter of the Tx beam. The UE may perform the uplink beam selection procedure based on one or more sounding reference signal (SRS) resources configured to the UE by the base station. The base station may select and indicate uplink beams for the UE based on measurements of the one or more SRS resources transmitted by the UE. 
     In a beam management procedure, a UE may assess (e.g., measure) a channel quality of one or more beam pair links, a beam pair link comprising a transmitting beam transmitted by a base station and a receiving beam received by the UE. Based on the assessment, the UE may transmit a beam measurement report indicating one or more beam pair quality parameters comprising, e.g., one or more beam identifications (e.g., a beam index, a reference signal index, or the like), RSRP, a precoding matrix indicator (PMI), a channel quality indicator (CQI), and/or a rank indicator (RI). 
       FIG. 12A  illustrates examples of three downlink beam management procedures: P1, P2, and P3. Procedure P1 may enable a UE measurement on transmit (Tx) beams of a transmission reception point (TRP) (or multiple TRPs), e.g., to support a selection of one or more base station Tx beams and/or UE Rx beams (shown as ovals in the top row and bottom row, respectively, of P1). Beamforming at a TRP may comprise a Tx beam sweep for a set of beams (shown, in the top rows of P1 and P2, as ovals rotated in a counter-clockwise direction indicated by the dashed arrow). Beamforming at a UE may comprise an Rx beam sweep for a set of beams (shown, in the bottom rows of P1 and P3, as ovals rotated in a clockwise direction indicated by the dashed arrow). Procedure P2 may be used to enable a UE measurement on Tx beams of a TRP (shown, in the top row of P2, as ovals rotated in a counter-clockwise direction indicated by the dashed arrow). The UE and/or the base station may perform procedure P2 using a smaller set of beams than is used in procedure P1, or using narrower beams than the beams used in procedure P1. This may be referred to as beam refinement. The UE may perform procedure P3 for Rx beam determination by using the same Tx beam at the base station and sweeping an Rx beam at the UE. 
       FIG. 12B  illustrates examples of three uplink beam management procedures: U1, U2, and U3. Procedure U1 may be used to enable a base station to perform a measurement on Tx beams of a UE, e.g., to support a selection of one or more UE Tx beams and/or base station Rx beams (shown as ovals in the top row and bottom row, respectively, of U1). Beamforming at the UE may include, e.g., a Tx beam sweep from a set of beams (shown in the bottom rows of U1 and U3 as ovals rotated in a clockwise direction indicated by the dashed arrow). Beamforming at the base station may include, e.g., an Rx beam sweep from a set of beams (shown, in the top rows of U1 and U2, as ovals rotated in a counter-clockwise direction indicated by the dashed arrow). Procedure U2 may be used to enable the base station to adjust its Rx beam when the UE uses a fixed Tx beam. The UE and/or the base station may perform procedure U2 using a smaller set of beams than is used in procedure P1, or using narrower beams than the beams used in procedure P1. This may be referred to as beam refinement The UE may perform procedure U3 to adjust its Tx beam when the base station uses a fixed Rx beam. 
     A UE may initiate a beam failure recovery (BFR) procedure based on detecting a beam failure. The UE may transmit a BFR request (e.g., a preamble, a UCI, an SR, a MAC CE, and/or the like) based on the initiating of the BFR procedure. The UE may detect the beam failure based on a determination that a quality of beam pair link(s) of an associated control channel is unsatisfactory (e.g., having an error rate higher than an error rate threshold, a received signal power lower than a received signal power threshold, an expiration of a timer, and/or the like). 
     The UE may measure a quality of a beam pair link using one or more reference signals (RSs) comprising one or more SS/PBCH blocks, one or more CSI-RS resources, and/or one or more demodulation reference signals (DMRSs). A quality of the beam pair link may be based on one or more of a block error rate (BLER), an RSRP value, a signal to interference plus noise ratio (SINR) value, a reference signal received quality (RSRQ) value, and/or a CSI value measured on RS resources. The base station may indicate that an RS resource is quasi co-located (QCLed) with one or more DM-RSs of a channel (e.g., a control channel, a shared data channel, and/or the like). The RS resource and the one or more DMRSs of the channel may be QCLed when the channel characteristics (e.g., Doppler shift, Doppler spread, average delay, delay spread, spatial Rx parameter, fading, and/or the like) from a transmission via the RS resource to the UE are similar or the same as the channel characteristics from a transmission via the channel to the UE. 
     A network (e.g., a gNB and/or an ng-eNB of a network) and/or the UE may initiate a random access procedure. A UE in an RRC_IDLE state and/or an RRC_INACTIVE state may initiate the random access procedure to request a connection setup to a network. The UE may initiate the random access procedure from an RRC_CONNECTED state. The UE may initiate the random access procedure to request uplink resources (e.g., for uplink transmission of an SR when there is no PUCCH resource available) and/or acquire uplink timing (e.g., when uplink synchronization status is non-synchronized). The UE may initiate the random access procedure to request one or more system information blocks (SIBs) (e.g., other system information such as SIB2, SIB3, and/or the like). The UE may initiate the random access procedure for a beam failure recovery request. A network may initiate a random access procedure for a handover and/or for establishing time alignment for an SCell addition. 
       FIG. 13A  illustrates a four-step contention-based random access procedure. Prior to initiation of the procedure, a base station may transmit a configuration message  1310  to the UE. The procedure illustrated in  FIG. 13A  comprises transmission of four messages: a Msg 1  1311 , a Msg 2  1312 , a Msg 3  1313 , and a Msg 4  1314 . The Msg 1  1311  may include and/or be referred to as a preamble (or a random access preamble). The Msg 2  1312  may include and/or be referred to as a random access response (RAR). 
     The configuration message  1310  may be transmitted, for example, using one or more RRC messages. The one or more RRC messages may indicate one or more random access channel (RACH) parameters to the UE. The one or more RACH parameters may comprise at least one of following: general parameters for one or more random access procedures (e.g., RACH-configGeneral); cell-specific parameters (e.g., RACH-ConfigCommon); and/or dedicated parameters (e.g., RACH-configDedicated). The base station may broadcast or multicast the one or more RRC messages to one or more UEs. The one or more RRC messages may be UE-specific (e.g., dedicated RRC messages transmitted to a UE in an RRC_CONNECTED state and/or in an RRC_INACTIVE state). The UE may determine, based on the one or more RACH parameters, a time-frequency resource and/or an uplink transmit power for transmission of the Msg 1  1311  and/or the Msg 3  1313 . Based on the one or more RACH parameters, the UE may determine a reception timing and a downlink channel for receiving the Msg 2  1312  and the Msg 4  1314 . 
     The one or more RACH parameters provided in the configuration message  1310  may indicate one or more Physical RACH (PRACH) occasions available for transmission of the Msg 1  1311 . The one or more PRACH occasions may be predefined. The one or more RACH parameters may indicate one or more available sets of one or more PRACH occasions (e.g., prach-ConfigIndex). The one or more RACH parameters may indicate an association between (a) one or more PRACH occasions and (b) one or more reference signals. The one or more RACH parameters may indicate an association between (a) one or more preambles and (b) one or more reference signals. The one or more reference signals may be SS/PBCH blocks and/or CSI-RSs. For example, the one or more RACH parameters may indicate a number of SS/PBCH blocks mapped to a PRACH occasion and/or a number of preambles mapped to a SS/PBCH blocks. 
     The one or more RACH parameters provided in the configuration message  1310  may be used to determine an uplink transmit power of Msg 1  1311  and/or Msg 3  1313 . For example, the one or more RACH parameters may indicate a reference power for a preamble transmission (e.g., a received target power and/or an initial power of the preamble transmission). There may be one or more power offsets indicated by the one or more RACH parameters. For example, the one or more RACH parameters may indicate: a power ramping step; a power offset between SSB and CSI-RS; a power offset between transmissions of the Msg 1  1311  and the Msg 3  1313 ; and/or a power offset value between preamble groups. The one or more RACH parameters may indicate one or more thresholds based on which the UE may determine at least one reference signal (e.g., an SSB and/or CSI-RS) and/or an uplink carrier (e.g., a normal uplink (NUL) carrier and/or a supplemental uplink (SUL) carrier). 
     The Msg 1  1311  may include one or more preamble transmissions (e.g., a preamble transmission and one or more preamble retransmissions). An RRC message may be used to configure one or more preamble groups (e.g., group A and/or group B). A preamble group may comprise one or more preambles. The UE may determine the preamble group based on a pathloss measurement and/or a size of the Msg 3  1313 . The UE may measure an RSRP of one or more reference signals (e.g., SSBs and/or CSI-RSs) and determine at least one reference signal having an RSRP above an RSRP threshold (e.g., rsrp-ThresholdSSB and/or rsrp-ThresholdCSI-RS). The UE may select at least one preamble associated with the one or more reference signals and/or a selected preamble group, for example, if the association between the one or more preambles and the at least one reference signal is configured by an RRC message. 
     The UE may determine the preamble based on the one or more RACH parameters provided in the configuration message  1310 . For example, the UE may determine the preamble based on a pathloss measurement, an RSRP measurement, and/or a size of the Msg 3  1313 . As another example, the one or more RACH parameters may indicate: a preamble format; a maximum number of preamble transmissions; and/or one or more thresholds for determining one or more preamble groups (e.g., group A and group B). A base station may use the one or more RACH parameters to configure the UE with an association between one or more preambles and one or more reference signals (e.g., SSBs and/or CSI-RSs). If the association is configured, the UE may determine the preamble to include in Msg 1  1311  based on the association. The Msg 1  1311  may be transmitted to the base station via one or more PRACH occasions. The UE may use one or more reference signals (e.g., SSBs and/or CSI-RSs) for selection of the preamble and for determining of the PRACH occasion. One or more RACH parameters (e.g., ra-ssb-OccasionMskIndex and/or ra-OccasionList) may indicate an association between the PRACH occasions and the one or more reference signals. 
     The UE may perform a preamble retransmission if no response is received following a preamble transmission. The UE may increase an uplink transmit power for the preamble retransmission. The UE may select an initial preamble transmit power based on a pathloss measurement and/or a target received preamble power configured by the network. The UE may determine to retransmit a preamble and may ramp up the uplink transmit power. The UE may receive one or more RACH parameters (e.g., PREAMBLE_POWER_RAMPING_STEP) indicating a ramping step for the preamble retransmission. The ramping step may be an amount of incremental increase in uplink transmit power for a retransmission. The UE may ramp up the uplink transmit power if the UE determines a reference signal (e.g., SSB and/or CSI-RS) that is the same as a previous preamble transmission. The UE may count a number of preamble transmissions and/or retransmissions (e.g., PREAMBLE_TRANSMISSION_COUNTER). The UE may determine that a random access procedure completed unsuccessfully, for example, if the number of preamble transmissions exceeds a threshold configured by the one or more RACH parameters (e.g., preambleTransMax). 
     The Msg 2  1312  received by the UE may include an RAR. In some scenarios, the Msg 2  1312  may include multiple RARs corresponding to multiple UEs. The Msg 2  1312  may be received after or in response to the transmitting of the Msg 1  1311 . The Msg 2  1312  may be scheduled on the DL-SCH and indicated on a PDCCH using a random access RNTI (RA-RNTI). The Msg 2  1312  may indicate that the Msg 1  1311  was received by the base station. The Msg 2  1312  may include a time-alignment command that may be used by the UE to adjust the UE&#39;s transmission timing, a scheduling grant for transmission of the Msg 3  1313 , and/or a Temporary Cell RNTI (TC-RNTI). After transmitting a preamble, the UE may start a time window (e.g., ra-ResponseWindow) to monitor a PDCCH for the Msg 2  1312 . The UE may determine when to start the time window based on a PRACH occasion that the UE uses to transmit the preamble. For example, the UE may start the time window one or more symbols after a last symbol of the preamble (e.g., at a first PDCCH occasion from an end of a preamble transmission). The one or more symbols may be determined based on a numerology. The PDCCH may be in a common search space (e.g., a Type1-PDCCH common search space) configured by an RRC message. The UE may identify the RAR based on a Radio Network Temporary Identifier (RNTI). RNTIs may be used depending on one or more events initiating the random access procedure. The UE may use random access RNTI (RA-RNTI). The RA-RNTI may be associated with PRACH occasions in which the UE transmits a preamble. For example, the UE may determine the RA-RNTI based on: an OFDM symbol index; a slot index; a frequency domain index; and/or a UL carrier indicator of the PRACH occasions. An example of RA-RNTI may be as follows: 
       RA-RNTI=1 +s _id+14 ×t _id+14×80 ×f _id+14×80×8 ×ul _carrier_id
 
     where s_id may be an index of a first OFDM symbol of the PRACH occasion (e.g., 0≤s_id&lt;14), t_id may be an index of a first slot of the PRACH occasion in a system frame (e.g., 0≤t_id&lt;80), f_id may be an index of the PRACH occasion in the frequency domain (e.g., 0≤f_id&lt;8), and ul_carrier_id may be a UL carrier used for a preamble transmission (e.g., 0 for an NUL carrier, and 1 for an SUL carrier). 
     The UE may transmit the Msg 3  1313  in response to a successful reception of the Msg 2  1312  (e.g., using resources identified in the Msg 2  1312 ). The Msg 3  1313  may be used for contention resolution in, for example, the contention-based random access procedure illustrated in  FIG. 13A . In some scenarios, a plurality of UEs may transmit a same preamble to a base station and the base station may provide an RAR that corresponds to a UE. Collisions may occur if the plurality of UEs interpret the RAR as corresponding to themselves. Contention resolution (e.g., using the Msg 3  1313  and the Msg 4  1314 ) may be used to increase the likelihood that the UE does not incorrectly use an identity of another the UE. To perform contention resolution, the UE may include a device identifier in the Msg 3  1313  (e.g., a C-RNTI if assigned, a TC-RNTI included in the Msg 2  1312 , and/or any other suitable identifier). 
     The Msg 4  1314  may be received after or in response to the transmitting of the Msg 3  1313 . If a C-RNTI was included in the Msg 3  1313 , the base station will address the UE on the PDCCH using the C-RNTI. If the UE&#39;s unique C-RNTI is detected on the PDCCH, the random access procedure is determined to be successfully completed. If a TC-RNTI is included in the Msg 3  1313  (e.g., if the UE is in an RRC_IDLE state or not otherwise connected to the base station), Msg 4  1314  will be received using a DL-SCH associated with the TC-RNTI. If a MAC PDU is successfully decoded and a MAC PDU comprises the UE contention resolution identity MAC CE that matches or otherwise corresponds with the CCCH SDU sent (e.g., transmitted) in Msg 3  1313 , the UE may determine that the contention resolution is successful and/or the UE may determine that the random access procedure is successfully completed. 
     The UE may be configured with a supplementary uplink (SUL) carrier and a normal uplink (NUL) carrier. An initial access (e.g., random access procedure) may be supported in an uplink carrier. For example, a base station may configure the UE with two separate RACH configurations: one for an SUL carrier and the other for an NUL carrier. For random access in a cell configured with an SUL carrier, the network may indicate which carrier to use (NUL or SUL). The UE may determine the SUL carrier, for example, if a measured quality of one or more reference signals is lower than a broadcast threshold. Uplink transmissions of the random access procedure (e.g., the Msg 1  1311  and/or the Msg 3  1313 ) may remain on the selected carrier. The UE may switch an uplink carrier during the random access procedure (e.g., between the Msg 1  1311  and the Msg 3  1313 ) in one or more cases. For example, the UE may determine and/or switch an uplink carrier for the Msg 1  1311  and/or the Msg 3  1313  based on a channel clear assessment (e.g., a listen-before-talk). 
       FIG. 13B  illustrates a two-step contention-free random access procedure. Similar to the four-step contention-based random access procedure illustrated in  FIG. 13A , a base station may, prior to initiation of the procedure, transmit a configuration message  1320  to the UE. The configuration message  1320  may be analogous in some respects to the configuration message  1310 . The procedure illustrated in  FIG. 13B  comprises transmission of two messages: a Msg 1  1321  and a Msg 2  1322 . The Msg 1  1321  and the Msg 2  1322  may be analogous in some respects to the Msg 1  1311  and a Msg 2  1312  illustrated in  FIG. 13A , respectively. As will be understood from  FIGS. 13A and 13B , the contention-free random access procedure may not include messages analogous to the Msg 3  1313  and/or the Msg 4  1314 . 
     The contention-free random access procedure illustrated in  FIG. 13B  may be initiated for a beam failure recovery, other SI request, SCell addition, and/or handover. For example, a base station may indicate or assign to the UE the preamble to be used for the Msg 1  1321 . The UE may receive, from the base station via PDCCH and/or RRC, an indication of a preamble (e.g., ra-PreambleIndex). 
     After transmitting a preamble, the UE may start a time window (e.g., ra-ResponseWindow) to monitor a PDCCH for the RAR. In the event of a beam failure recovery request, the base station may configure the UE with a separate time window and/or a separate PDCCH in a search space indicated by an RRC message (e.g., recoverySearchSpaceId). The UE may monitor for a PDCCH transmission addressed to a Cell RNTI (C-RNTI) on the search space. In the contention-free random access procedure illustrated in  FIG. 13B , the UE may determine that a random access procedure successfully completes after or in response to transmission of Msg 1  1321  and reception of a corresponding Msg 2  1322 . The UE may determine that a random access procedure successfully completes, for example, if a PDCCH transmission is addressed to a C-RNTI. The UE may determine that a random access procedure successfully completes, for example, if the UE receives an RAR comprising a preamble identifier corresponding to a preamble transmitted by the UE and/or the RAR comprises a MAC sub-PDU with the preamble identifier. The UE may determine the response as an indication of an acknowledgement for an SI request. 
       FIG. 13C  illustrates another two-step random access procedure. Similar to the random access procedures illustrated in  FIGS. 13A and 13B , a base station may, prior to initiation of the procedure, transmit a configuration message  1330  to the UE. The configuration message  1330  may be analogous in some respects to the configuration message  1310  and/or the configuration message  1320 . The procedure illustrated in  FIG. 13C  comprises transmission of two messages: a Msg A  1331  and a Msg B  1332 . 
     Msg A  1331  may be transmitted in an uplink transmission by the UE. Msg A  1331  may comprise one or more transmissions of a preamble  1341  and/or one or more transmissions of a transport block  1342 . The transport block  1342  may comprise contents that are similar and/or equivalent to the contents of the Msg 3  1313  illustrated in  FIG. 13A . The transport block  1342  may comprise UCI (e.g., an SR, a HARQ ACK/NACK, and/or the like). The UE may receive the Msg B  1332  after or in response to transmitting the Msg A  1331 . The Msg B  1332  may comprise contents that are similar and/or equivalent to the contents of the Msg 2  1312  (e.g., an RAR) illustrated in  FIGS. 13A and 13B  and/or the Msg 4  1314  illustrated in  FIG. 13A . 
     The UE may initiate the two-step random access procedure in  FIG. 13C  for licensed spectrum and/or unlicensed spectrum. The UE may determine, based on one or more factors, whether to initiate the two-step random access procedure. The one or more factors may be: a radio access technology in use (e.g., LTE, NR, and/or the like); whether the UE has valid TA or not; a cell size; the UE&#39;s RRC state; a type of spectrum (e.g., licensed vs. unlicensed); and/or any other suitable factors. 
     The UE may determine, based on two-step RACH parameters included in the configuration message  1330 , a radio resource and/or an uplink transmit power for the preamble  1341  and/or the transport block  1342  included in the Msg A  1331 . The RACH parameters may indicate a modulation and coding schemes (MCS), a time-frequency resource, and/or a power control for the preamble  1341  and/or the transport block  1342 . A time-frequency resource for transmission of the preamble  1341  (e.g., a PRACH) and a time-frequency resource for transmission of the transport block  1342  (e.g., a PUSCH) may be multiplexed using FDM, TDM, and/or CDM. The RACH parameters may enable the UE to determine a reception timing and a downlink channel for monitoring for and/or receiving Msg B  1332 . 
     The transport block  1342  may comprise data (e.g., delay-sensitive data), an identifier of the UE, security information, and/or device information (e.g., an International Mobile Subscriber Identity (IMSI)). The base station may transmit the Msg B  1332  as a response to the Msg A  1331 . The Msg B  1332  may comprise at least one of following: a preamble identifier; a timing advance command; a power control command; an uplink grant (e.g., a radio resource assignment and/or an MCS); a UE identifier for contention resolution; and/or an RNTI (e.g., a C-RNTI or a TC-RNTI). The UE may determine that the two-step random access procedure is successfully completed if: a preamble identifier in the Msg B  1332  is matched to a preamble transmitted by the UE; and/or the identifier of the UE in Msg B  1332  is matched to the identifier of the UE in the Msg A  1331  (e.g., the transport block  1342 ). 
     A UE and a base station may exchange control signaling. The control signaling may be referred to as L1/L2 control signaling and may originate from the PHY layer (e.g., layer 1) and/or the MAC layer (e.g., layer 2). The control signaling may comprise downlink control signaling transmitted from the base station to the UE and/or uplink control signaling transmitted from the UE to the base station. 
     The downlink control signaling may comprise: a downlink scheduling assignment; an uplink scheduling grant indicating uplink radio resources and/or a transport format; a slot format information; a preemption indication; a power control command; and/or any other suitable signaling. The UE may receive the downlink control signaling in a payload transmitted by the base station on a physical downlink control channel (PDCCH). The payload transmitted on the PDCCH may be referred to as downlink control information (DCI). In some scenarios, the PDCCH may be a group common PDCCH (GC-PDCCH) that is common to a group of UEs. 
     A base station may attach one or more cyclic redundancy check (CRC) parity bits to a DCI in order to facilitate detection of transmission errors. When the DCI is intended for a UE (or a group of the UEs), the base station may scramble the CRC parity bits with an identifier of the UE (or an identifier of the group of the UEs). Scrambling the CRC parity bits with the identifier may comprise Modulo-2 addition (or an exclusive OR operation) of the identifier value and the CRC parity bits. The identifier may comprise a 16-bit value of a radio network temporary identifier (RNTI). 
     DCIs may be used for different purposes. A purpose may be indicated by the type of RNTI used to scramble the CRC parity bits. For example, a DCI having CRC parity bits scrambled with a paging RNTI (P-RNTI) may indicate paging information and/or a system information change notification. The P-RNTI may be predefined as “FFFE” in hexadecimal. A DCI having CRC parity bits scrambled with a system information RNTI (SI-RNTI) may indicate a broadcast transmission of the system information. The SI-RNTI may be predefined as “FFFF” in hexadecimal. A DCI having CRC parity bits scrambled with a random access RNTI (RA-RNTI) may indicate a random access response (RAR). A DCI having CRC parity bits scrambled with a cell RNTI (C-RNTI) may indicate a dynamically scheduled unicast transmission and/or a triggering of PDCCH-ordered random access. A DCI having CRC parity bits scrambled with a temporary cell RNTI (TC-RNTI) may indicate a contention resolution (e.g., a Msg 3 analogous to the Msg 3  1313  illustrated in  FIG. 13A ). Other RNTIs configured to the UE by a base station may comprise a Configured Scheduling RNTI (CS-RNTI), a Transmit Power Control-PUCCH RNTI (TPC-PUCCH-RNTI), a Transmit Power Control-PUSCH RNTI (TPC-PUSCH-RNTI), a Transmit Power Control-SRS RNTI (TPC-SRS-RNTI), an Interruption RNTI (INT-RNTI), a Slot Format Indication RNTI (SFI-RNTI), a Semi-Persistent CSI RNTI (SP-CSI-RNTI), a Modulation and Coding Scheme Cell RNTI (MCS-C-RNTI), and/or the like. 
     Depending on the purpose and/or content of a DCI, the base station may transmit the DCIs with one or more DCI formats. For example, DCI format 0_0 may be used for scheduling of PUSCH in a cell. DCI format 0_0 may be a fallback DCI format (e.g., with compact DCI payloads). DCI format 0_1 may be used for scheduling of PUSCH in a cell (e.g., with more DCI payloads than DCI format 0_0). DCI format 1_0 may be used for scheduling of PDSCH in a cell. DCI format 1_0 may be a fallback DCI format (e.g., with compact DCI payloads). DCI format 1_1 may be used for scheduling of PDSCH in a cell (e.g., with more DCI payloads than DCI format 1_0). DCI format 2_0 may be used for providing a slot format indication to a group of UEs. DCI format 2_1 may be used for notifying a group of UEs of a physical resource block and/or OFDM symbol where the UE may assume no transmission is intended to the UE. DCI format 2_2 may be used for transmission of a transmit power control (TPC) command for PUCCH or PUSCH. DCI format 2_3 may be used for transmission of a group of TPC commands for SRS transmissions by one or more UEs. DCI format(s) for new functions may be defined in future releases. DCI formats may have different DCI sizes, or may share the same DCI size. 
     After scrambling a DCI with a RNTI, the base station may process the DCI with channel coding (e.g., polar coding), rate matching, scrambling and/or QPSK modulation. A base station may map the coded and modulated DCI on resource elements used and/or configured for a PDCCH. Based on a payload size of the DCI and/or a coverage of the base station, the base station may transmit the DCI via a PDCCH occupying a number of contiguous control channel elements (CCEs). The number of the contiguous CCEs (referred to as aggregation level) may be 1, 2, 4, 8, 16, and/or any other suitable number. A CCE may comprise a number (e.g., 6) of resource-element groups (REGs). A REG may comprise a resource block in an OFDM symbol. The mapping of the coded and modulated DCI on the resource elements may be based on mapping of CCEs and REGs (e.g., CCE-to-REG mapping). 
       FIG. 14A  illustrates an example of CORESET configurations for a bandwidth part. The base station may transmit a DCI via a PDCCH on one or more control resource sets (CORESETs). A CORESET may comprise a time-frequency resource in which the UE tries to decode a DCI using one or more search spaces. The base station may configure a CORESET in the time-frequency domain. In the example of  FIG. 14A , a first CORESET  1401  and a second CORESET  1402  occur at the first symbol in a slot. The first CORESET  1401  overlaps with the second CORESET  1402  in the frequency domain. A third CORESET  1403  occurs at a third symbol in the slot. A fourth CORESET  1404  occurs at the seventh symbol in the slot. CORESETs may have a different number of resource blocks in frequency domain. 
       FIG. 14B  illustrates an example of a CCE-to-REG mapping for DCI transmission on a CORESET and PDCCH processing. The CCE-to-REG mapping may be an interleaved mapping (e.g., for the purpose of providing frequency diversity) or a non-interleaved mapping (e.g., for the purposes of facilitating interference coordination and/or frequency-selective transmission of control channels). The base station may perform different or same CCE-to-REG mapping on different CORESETs. A CORESET may be associated with a CCE-to-REG mapping by RRC configuration. A CORESET may be configured with an antenna port quasi co-location (QCL) parameter. The antenna port QCL parameter may indicate QCL information of a demodulation reference signal (DMRS) for PDCCH reception in the CORESET. 
     The base station may transmit, to the UE, RRC messages comprising configuration parameters of one or more CORESETs and one or more search space sets. The configuration parameters may indicate an association between a search space set and a CORESET. A search space set may comprise a set of PDCCH candidates formed by CCEs at a given aggregation level. The configuration parameters may indicate: a number of PDCCH candidates to be monitored per aggregation level; a PDCCH monitoring periodicity and a PDCCH monitoring pattern; one or more DCI formats to be monitored by the UE; and/or whether a search space set is a common search space set or a UE-specific search space set. A set of CCEs in the common search space set may be predefined and known to the UE. A set of CCEs in the UE-specific search space set may be configured based on the UE&#39;s identity (e.g., C-RNTI). 
     As shown in  FIG. 14B , the UE may determine a time-frequency resource for a CORESET based on RRC messages. The UE may determine a CCE-to-REG mapping (e.g., interleaved or non-interleaved, and/or mapping parameters) for the CORESET based on configuration parameters of the CORESET. The UE may determine a number (e.g., at most 10) of search space sets configured on the CORESET based on the RRC messages. The UE may monitor a set of PDCCH candidates according to configuration parameters of a search space set. The UE may monitor a set of PDCCH candidates in one or more CORESETs for detecting one or more DCIs. Monitoring may comprise decoding one or more PDCCH candidates of the set of the PDCCH candidates according to the monitored DCI formats. Monitoring may comprise decoding a DCI content of one or more PDCCH candidates with possible (or configured) PDCCH locations, possible (or configured) PDCCH formats (e.g., number of CCEs, number of PDCCH candidates in common search spaces, and/or number of PDCCH candidates in the UE-specific search spaces) and possible (or configured) DCI formats. The decoding may be referred to as blind decoding. The UE may determine a DCI as valid for the UE, in response to CRC checking (e.g., scrambled bits for CRC parity bits of the DCI matching a RNTI value). The UE may process information contained in the DCI (e.g., a scheduling assignment, an uplink grant, power control, a slot format indication, a downlink preemption, and/or the like). 
     The UE may transmit uplink control signaling (e.g., uplink control information (UCI)) to a base station. The uplink control signaling may comprise hybrid automatic repeat request (HARQ) acknowledgements for received DL-SCH transport blocks. The UE may transmit the HARQ acknowledgements after receiving a DL-SCH transport block. Uplink control signaling may comprise channel state information (CSI) indicating channel quality of a physical downlink channel. The UE may transmit the CSI to the base station. The base station, based on the received CSI, may determine transmission format parameters (e.g., comprising multi-antenna and beamforming schemes) for a downlink transmission. Uplink control signaling may comprise scheduling requests (SR). The UE may transmit an SR indicating that uplink data is available for transmission to the base station. The UE may transmit a UCI (e.g., HARQ acknowledgements (HARQ-ACK), CSI report, SR, and the like) via a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). The UE may transmit the uplink control signaling via a PUCCH using one of several PUCCH formats. 
     There may be five PUCCH formats and the UE may determine a PUCCH format based on a size of the UCI (e.g., a number of uplink symbols of UCI transmission and a number of UCI bits). PUCCH format 0 may have a length of one or two OFDM symbols and may include two or fewer bits. The UE may transmit UCI in a PUCCH resource using PUCCH format 0 if the transmission is over one or two symbols and the number of HARQ-ACK information bits with positive or negative SR (HARQ-ACK/SR bits) is one or two. PUCCH format 1 may occupy a number between four and fourteen OFDM symbols and may include two or fewer bits. The UE may use PUCCH format 1 if the transmission is four or more symbols and the number of HARQ-ACK/SR bits is one or two. PUCCH format 2 may occupy one or two OFDM symbols and may include more than two bits. The UE may use PUCCH format 2 if the transmission is over one or two symbols and the number of UCI bits is two or more. PUCCH format 3 may occupy a number between four and fourteen OFDM symbols and may include more than two bits. The UE may use PUCCH format 3 if the transmission is four or more symbols, the number of UCI bits is two or more and PUCCH resource does not include an orthogonal cover code. PUCCH format 4 may occupy a number between four and fourteen OFDM symbols and may include more than two bits. The UE may use PUCCH format 4 if the transmission is four or more symbols, the number of UCI bits is two or more and the PUCCH resource includes an orthogonal cover code. 
     The base station may transmit configuration parameters to the UE for a plurality of PUCCH resource sets using, for example, an RRC message. The plurality of PUCCH resource sets (e.g., up to four sets) may be configured on an uplink BWP of a cell. A PUCCH resource set may be configured with a PUCCH resource set index, a plurality of PUCCH resources with a PUCCH resource being identified by a PUCCH resource identifier (e.g., pucch-Resourceid), and/or a number (e.g. a maximum number) of UCI information bits the UE may transmit using one of the plurality of PUCCH resources in the PUCCH resource set. When configured with a plurality of PUCCH resource sets, the UE may select one of the plurality of PUCCH resource sets based on a total bit length of the UCI information bits (e.g., HARQ-ACK, SR, and/or CSI). If the total bit length of UCI information bits is two or fewer, the UE may select a first PUCCH resource set having a PUCCH resource set index equal to “0”. If the total bit length of UCI information bits is greater than two and less than or equal to a first configured value, the UE may select a second PUCCH resource set having a PUCCH resource set index equal to “1”. If the total bit length of UCI information bits is greater than the first configured value and less than or equal to a second configured value, the UE may select a third PUCCH resource set having a PUCCH resource set index equal to “2”. If the total bit length of UCI information bits is greater than the second configured value and less than or equal to a third value (e.g., 1406), the UE may select a fourth PUCCH resource set having a PUCCH resource set index equal to “3”. 
     After determining a PUCCH resource set from a plurality of PUCCH resource sets, the UE may determine a PUCCH resource from the PUCCH resource set for UCI (HARQ-ACK, CSI, and/or SR) transmission. The UE may determine the PUCCH resource based on a PUCCH resource indicator in a DCI (e.g., with a DCI format 1_0 or DCI for 1_1) received on a PDCCH. A three-bit PUCCH resource indicator in the DCI may indicate one of eight PUCCH resources in the PUCCH resource set. Based on the PUCCH resource indicator, the UE may transmit the UCI (HARQ-ACK, CSI and/or SR) using a PUCCH resource indicated by the PUCCH resource indicator in the DCI. 
       FIG. 15  illustrates an example of a wireless device  1502  in communication with a base station  1504  in accordance with embodiments of the present disclosure. The wireless device  1502  and base station  1504  may be part of a mobile communication network, such as the mobile communication network  100  illustrated in  FIG. 1A , the mobile communication network  150  illustrated in  FIG. 1B , or any other communication network. Only one wireless device  1502  and one base station  1504  are illustrated in  FIG. 15 , but it will be understood that a mobile communication network may include more than one UE and/or more than one base station, with the same or similar configuration as those shown in  FIG. 15 . 
     The base station  1504  may connect the wireless device  1502  to a core network (not shown) through radio communications over the air interface (or radio interface)  1506 . The communication direction from the base station  1504  to the wireless device  1502  over the air interface  1506  is known as the downlink, and the communication direction from the wireless device  1502  to the base station  1504  over the air interface is known as the uplink. Downlink transmissions may be separated from uplink transmissions using FDD, TDD, and/or some combination of the two duplexing techniques. 
     In the downlink, data to be sent to the wireless device  1502  from the base station  1504  may be provided to the processing system  1508  of the base station  1504 . The data may be provided to the processing system  1508  by, for example, a core network. In the uplink, data to be sent to the base station  1504  from the wireless device  1502  may be provided to the processing system  1518  of the wireless device  1502 . The processing system  1508  and the processing system  1518  may implement layer 3 and layer 2 OSI functionality to process the data for transmission. Layer 2 may include an SDAP layer, a PDCP layer, an RLC layer, and a MAC layer, for example, with respect to  FIG. 2A ,  FIG. 2B ,  FIG. 3 , and  FIG. 4A . Layer 3 may include an RRC layer as with respect to  FIG. 2B . 
     After being processed by processing system  1508 , the data to be sent to the wireless device  1502  may be provided to a transmission processing system  1510  of base station  1504 . Similarly, after being processed by the processing system  1518 , the data to be sent to base station  1504  may be provided to a transmission processing system  1520  of the wireless device  1502 . The transmission processing system  1510  and the transmission processing system  1520  may implement layer 1 OSI functionality. Layer 1 may include a PHY layer with respect to  FIG. 2A ,  FIG. 2B ,  FIG. 3 , and  FIG. 4A . For transmit processing, the PHY layer may perform, for example, forward error correction coding of transport channels, interleaving, rate matching, mapping of transport channels to physical channels, modulation of physical channel, multiple-input multiple-output (MIMO) or multi-antenna processing, and/or the like. 
     At the base station  1504 , a reception processing system  1512  may receive the uplink transmission from the wireless device  1502 . At the wireless device  1502 , a reception processing system  1522  may receive the downlink transmission from base station  1504 . The reception processing system  1512  and the reception processing system  1522  may implement layer 1 OSI functionality. Layer 1 may include a PHY layer with respect to  FIG. 2A ,  FIG. 2B ,  FIG. 3 , and  FIG. 4A . For receive processing, the PHY layer may perform, for example, error detection, forward error correction decoding, deinterleaving, demapping of transport channels to physical channels, demodulation of physical channels, MIMO or multi-antenna processing, and/or the like. 
     As shown in  FIG. 15 , a wireless device  1502  and the base station  1504  may include multiple antennas. The multiple antennas may be used to perform one or more MIMO or multi-antenna techniques, such as spatial multiplexing (e.g., single-user MIMO or multi-user MIMO), transmit/receive diversity, and/or beamforming. In other examples, the wireless device  1502  and/or the base station  1504  may have a single antenna. 
     The processing system  1508  and the processing system  1518  may be associated with a memory  1514  and a memory  1524 , respectively. Memory  1514  and memory  1524  (e.g., one or more non-transitory computer readable mediums) may store computer program instructions or code that may be executed by the processing system  1508  and/or the processing system  1518  to carry out one or more of the functionalities discussed in the present application. Although not shown in  FIG. 15 , the transmission processing system  1510 , the transmission processing system  1520 , the reception processing system  1512 , and/or the reception processing system  1522  may be coupled to a memory (e.g., one or more non-transitory computer readable mediums) storing computer program instructions or code that may be executed to carry out one or more of their respective functionalities. 
     The processing system  1508  and/or the processing system  1518  may comprise one or more controllers and/or one or more processors. The one or more controllers and/or one or more processors may comprise, for example, a general-purpose processor, a digital signal processor (DSP), a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) and/or other programmable logic device, discrete gate and/or transistor logic, discrete hardware components, an on-board unit, or any combination thereof. The processing system  1508  and/or the processing system  1518  may perform at least one of signal coding/processing, data processing, power control, input/output processing, and/or any other functionality that may enable the wireless device  1502  and the base station  1504  to operate in a wireless environment. 
     The processing system  1508  and/or the processing system  1518  may be connected to one or more peripherals  1516  and one or more peripherals  1526 , respectively. The one or more peripherals  1516  and the one or more peripherals  1526  may include software and/or hardware that provide features and/or functionalities, for example, a speaker, a microphone, a keypad, a display, a touchpad, a power source, a satellite transceiver, a universal serial bus (USB) port, a hands-free headset, a frequency modulated (FM) radio unit, a media player, an Internet browser, an electronic control unit (e.g., for a motor vehicle), and/or one or more sensors (e.g., an accelerometer, a gyroscope, a temperature sensor, a radar sensor, a lidar sensor, an ultrasonic sensor, a light sensor, a camera, and/or the like). The processing system  1508  and/or the processing system  1518  may receive user input data from and/or provide user output data to the one or more peripherals  1516  and/or the one or more peripherals  1526 . The processing system  1518  in the wireless device  1502  may receive power from a power source and/or may be configured to distribute the power to the other components in the wireless device  1502 . The power source may comprise one or more sources of power, for example, a battery, a solar cell, a fuel cell, or any combination thereof. The processing system  1508  and/or the processing system  1518  may be connected to a GPS chipset  1517  and a GPS chipset  1527 , respectively. The GPS chipset  1517  and the GPS chipset  1527  may be configured to provide geographic location information of the wireless device  1502  and the base station  1504 , respectively. 
       FIG. 16A  illustrates an example structure for uplink transmission. A baseband signal representing a physical uplink shared channel may perform one or more functions. The one or more functions may comprise at least one of: scrambling; modulation of scrambled bits to generate complex-valued symbols; mapping of the complex-valued modulation symbols onto one or several transmission layers; transform precoding to generate complex-valued symbols; precoding of the complex-valued symbols; mapping of precoded complex-valued symbols to resource elements; generation of complex-valued time-domain Single Carrier-Frequency Division Multiple Access (SC-FDMA) or CP-OFDM signal for an antenna port; and/or the like. In an example, when transform precoding is enabled, a SC-FDMA signal for uplink transmission may be generated. In an example, when transform precoding is not enabled, an CP-OFDM signal for uplink transmission may be generated by  FIG. 16A . These functions are illustrated as examples and it is anticipated that other mechanisms may be implemented in various embodiments. 
       FIG. 16B  illustrates an example structure for modulation and up-conversion of a baseband signal to a carrier frequency. The baseband signal may be a complex-valued SC-FDMA or CP-OFDM baseband signal for an antenna port and/or a complex-valued Physical Random Access Channel (PRACH) baseband signal. Filtering may be employed prior to transmission. 
       FIG. 16C  illustrates an example structure for downlink transmissions. A baseband signal representing a physical downlink channel may perform one or more functions. The one or more functions may comprise: scrambling of coded bits in a codeword to be transmitted on a physical channel; modulation of scrambled bits to generate complex-valued modulation symbols; mapping of the complex-valued modulation symbols onto one or several transmission layers; precoding of the complex-valued modulation symbols on a layer for transmission on the antenna ports; mapping of complex-valued modulation symbols for an antenna port to resource elements; generation of complex-valued time-domain OFDM signal for an antenna port; and/or the like. These functions are illustrated as examples and it is anticipated that other mechanisms may be implemented in various embodiments. 
       FIG. 16D  illustrates another example structure for modulation and up-conversion of a baseband signal to a carrier frequency. The baseband signal may be a complex-valued OFDM baseband signal for an antenna port. Filtering may be employed prior to transmission. 
     A wireless device may receive from a base station one or more messages (e.g. RRC messages) comprising configuration parameters of a plurality of cells (e.g. primary cell, secondary cell). The wireless device may communicate with at least one base station (e.g. two or more base stations in dual-connectivity) via the plurality of cells. The one or more messages (e.g. as a part of the configuration parameters) may comprise parameters of physical, MAC, RLC, PCDP, SDAP, RRC layers for configuring the wireless device. For example, the configuration parameters may comprise parameters for configuring physical and MAC layer channels, bearers, etc. For example, the configuration parameters may comprise parameters indicating values of timers for physical, MAC, RLC, PCDP, SDAP, RRC layers, and/or communication channels. 
     A timer may begin running once it is started and continue running until it is stopped or until it expires. A timer may be started if it is not running or restarted if it is running. A timer may be associated with a value (e.g. the timer may be started or restarted from a value or may be started from zero and expire once it reaches the value). The duration of a timer may not be updated until the timer is stopped or expires (e.g., due to BWP switching). A timer may be used to measure a time period/window for a process. When the specification refers to an implementation and procedure related to one or more timers, it will be understood that there are multiple ways to implement the one or more timers. For example, it will be understood that one or more of the multiple ways to implement a timer may be used to measure a time period/window for the procedure. For example, a random access response window timer may be used for measuring a window of time for receiving a random access response. In an example, instead of starting and expiry of a random access response window timer, the time difference between two time stamps may be used. When a timer is restarted, a process for measurement of time window may be restarted. Other example implementations may be provided to restart a measurement of a time window. 
       FIG. 17  illustrates examples of device-to-device (D2D) communication, in which there is a direct communication between wireless devices. In an example, D2D communication may be performed via a sidelink (SL). The wireless devices may exchange sidelink communications via a sidelink interface (e.g., a PC5 interface). Sidelink differs from uplink (in which a wireless device communicates to a base station) and downlink (in which a base station communicates to a wireless device). A wireless device and a base station may exchange uplink and/or downlink communications via a user plane interface (e.g., a Uu interface). 
     As shown in the figure, wireless device #1 and wireless device #2 may be in a coverage area of base station #1. For example, both wireless device #1 and wireless device #2 may communicate with the base station #1 via a Uu interface. Wireless device #3 may be in a coverage area of base station #2. Base station #1 and base station #2 may share a network and may jointly provide a network coverage area. Wireless device #4 and wireless device #5 may be outside of the network coverage area. 
     In-coverage D2D communication may be performed when two wireless devices share a network coverage area. Wireless device #1 and wireless device #2 are both in the coverage area of base station #1. Accordingly, they may perform an in-coverage intra-cell D2D communication, labeled as sidelink A. Wireless device #2 and wireless device #3 are in the coverage areas of different base stations, but share the same network coverage area. Accordingly, they may perform an in-coverage inter-cell D2D communication, labeled as sidelink B. Partial-coverage D2D communications may be performed when one wireless device is within the network coverage area and the other wireless device is outside the network coverage area. Wireless device #3 and wireless device #4 may perform a partial-coverage D2D communication, labeled as sidelink C. Out-of-coverage D2D communications may be performed when both wireless devices are outside of the network coverage area. Wireless device #4 and wireless device #5 may perform an out-of-coverage D2D communication, labeled as sidelink D. 
     Sidelink communications may be configured using physical channels, for example, a physical sidelink broadcast channel (PSBCH), a physical sidelink feedback channel (PSFCH), a physical sidelink discovery channel (PSDCH), a physical sidelink control channel (PSCCH), and/or a physical sidelink shared channel (PSSCH). PSBCH may be used by a first wireless device to send broadcast information to a second wireless device. PSBCH may be similar in some respects to PBCH. The broadcast information may comprise, for example, a slot format indication, resource pool information, a sidelink system frame number, or any other suitable broadcast information. PSFCH may be used by a first wireless device to send feedback information to a second wireless device. The feedback information may comprise, for example, HARQ feedback information. PSDCH may be used by a first wireless device to send discovery information to a second wireless device. The discovery information may be used by a wireless device to signal its presence and/or the availability of services to other wireless devices in the area. PSCCH may be used by a first wireless device to send sidelink control information (SCI) to a second wireless device. PSCCH may be similar in some respects to PDCCH and/or PUCCH. The control information may comprise, for example, time/frequency resource allocation information (RB size, a number of retransmissions, etc.), demodulation related information (DMRS, MCS, RV, etc.), identifying information for a transmitting wireless device and/or a receiving wireless device, a process identifier (HARQ, etc.), or any other suitable control information. The PSCCH may be used to allocate, prioritize, and/or reserve sidelink resources for sidelink transmissions. PSSCH may be used by a first wireless device to send and/or relay data and/or network information to a second wireless device. PSSCH may be similar in some respects to PDSCH and/or PUSCH. Each of the sidelink channels may be associated with one or more demodulation reference signals. Sidelink operations may utilize sidelink synchronization signals to establish a timing of sidelink operations. Wireless devices configured for sidelink operations may send sidelink synchronization signals, for example, with the PSBCH. The sidelink synchronization signals may include primary sidelink synchronization signals (PSSS) and secondary sidelink synchronization signals (SSSS). 
     Sidelink resources may be configured to a wireless device in any suitable manner. A wireless device may be pre-configured for sidelink, for example, pre-configured with sidelink resource information. Additionally or alternatively, a network may broadcast system information relating to a resource pool for sidelink. Additionally or alternatively, a network may configure a particular wireless device with a dedicated sidelink configuration. The configuration may identify sidelink resources to be used for sidelink operation (e.g., configure a sidelink band combination). 
     The wireless device may operate in different modes, for example, an assisted mode (which may be referred to as mode 1) or an autonomous mode (which may be referred to as mode 2). Mode selection may be based on a coverage status of the wireless device, a radio resource control status of the wireless device, information and/or instructions from the network, and/or any other suitable factors. For example, if the wireless device is idle or inactive, or if the wireless device is outside of network coverage, the wireless device may select to operate in autonomous mode. For example, if the wireless device is in a connected mode (e.g., connected to a base station), the wireless device may select to operate (or be instructed by the base station to operate) in assisted mode. For example, the network (e.g., a base station) may instruct a connected wireless device to operate in a particular mode. 
     In an assisted mode, the wireless device may request scheduling from the network. For example, the wireless device may send a scheduling request to the network and the network may allocate sidelink resources to the wireless device. Assisted mode may be referred to as network-assisted mode, gNB-assisted mode, or base station-assisted mode. In an autonomous mode, the wireless device may select sidelink resources based on measurements within one or more resource pools (for example, pre-configure or network-assigned resource pools), sidelink resource selections made by other wireless devices, and/or sidelink resource usage of other wireless devices. 
     To select sidelink resources, a wireless device may observe a sensing window and a selection window. During the sensing window, the wireless device may observe SCI transmitted by other wireless devices using the sidelink resource pool. The SCIs may identify resources that may be used and/or reserved for sidelink transmissions. Based on the resources identified in the SCIs, the wireless device may select resources within the selection window (for example, resource that are different from the resources identified in the SCIs). The wireless device may transmit using the selected sidelink resources. 
       FIG. 18  illustrates an example of a resource pool for sidelink operations. A wireless device may operate using one or more sidelink cells. A sidelink cell may include one or more resource pools. Each resource pool may be configured to operate in accordance with a particular mode (for example, assisted or autonomous). The resource pool may be divided into resource units. In the frequency domain, each resource unit may comprise, for example, one or more resource blocks which may be referred to as a sub-channel. In the time domain, each resource unit may comprise, for example, one or more slots, one or more subframes, and/or one or more OFDM symbols. The resource pool may be continuous or non-continuous in the frequency domain and/or the time domain (for example, comprising contiguous resource units or non-contiguous resource units). The resource pool may be divided into repeating resource pool portions. The resource pool may be shared among one or more wireless devices. Each wireless device may attempt to transmit using different resource units, for example, to avoid collisions. 
     Sidelink resource pools may be arranged in any suitable manner. In the figure, the example resource pool is non-contiguous in the time domain and confined to a single sidelink BWP. In the example resource pool, frequency resources are divided into a Nf resource units per unit of time, numbered from zero to Nf−1. The example resource pool may comprise a plurality of portions (non-contiguous in this example) that repeat every k units of time. In the figure, time resources are numbered as n, n+1 . . . n+k, n+k+1 . . . , etc. 
     A wireless device may select for transmission one or more resource units from the resource pool. In the example resource pool, the wireless device selects resource unit (n,0) for sidelink transmission. The wireless device may further select periodic resource units in later portions of the resource pool, for example, resource unit (n+k,0), resource unit (n+2k,0), resource unit (n+3k,0), etc. The selection may be based on, for example, a determination that a transmission using resource unit (n,0) will not (or is not likely) to collide with a sidelink transmission of a wireless device that shares the sidelink resource pool. The determination may be based on, for example, behavior of other wireless devices that share the resource pool. For example, if no sidelink transmissions are detected in resource unit (n−k,0), then the wireless device may select resource unit (n,0), resource (n+k,0), etc. For example, if a sidelink transmission from another wireless device is detected in resource unit (n−k,1), then the wireless device may avoid selection of resource unit (n,1), resource (n+k,1), etc. 
     Different sidelink physical channels may use different resource pools. For example, PSCCH may use a first resource pool and PSSCH may use a second resource pool. Different resource priorities may be associated with different resource pools. For example, data associated with a first QoS, service, priority, and/or other characteristic may use a first resource pool and data associated with a second QoS, service, priority, and/or other characteristic may use a second resource pool. For example, a network (e.g., a base station) may configure a priority level for each resource pool, a service to be supported for each resource pool, etc. For example, a network (e.g., a base station) may configure a first resource pool for use by unicast UEs, a second resource pool for use by groupcast UEs, etc. For example, a network (e.g., a base station) may configure a first resource pool for transmission of sidelink data, a second resource pool for transmission of discovery messages, etc. 
     An E-UTRA RAN connected to 5G core (5GC) may support an RRC inactive state with similar characteristics to the RRC inactive state of NR connected to 5GC. 
     An RRC layer of a base station (e.g., NG-RAN base station) and a UE may support at least one of:
         PLMN selection;   Broadcast of system information;   Cell re-selection mobility;   Paging initiated by NG-RAN (RAN paging);   RAN-based notification area (RNA) managed by NG-RAN;   DRX for RAN paging configured by NG-RAN;   5GC-NG-RAN connection (both C/U-planes) established for the UE;   The UE AS context stored in NG-RAN and the UE; or   NG-RAN knowing the RNA which the UE belongs to.       

     A UE may remain in CM-CONNECTED and move within an area configured by the base station without notifying the base station when the UE is in RRC inactive state where the area is an RNA. In RRC inactive state, a last serving gNB node may keep the UE context and the UE-associated NG connection with the serving AMF and UPF. Based on received downlink data from the UPF or downlink UE-associated signaling from the AMF while the UE is in RRC inactive state, the last serving gNB may page in the cells corresponding to the RNA and may send RAN Paging via an Xn interface to neighbor gNB(s) if the RNA includes cells of neighbor gNB(s). 
     An AMF may provide to the base station a Core Network Assistance Information to assist the base station&#39;s decision whether a UE can be sent to RRC inactive state. The Core Network Assistance Information may include the registration area configured for the UE, the Periodic Registration Update timer, a UE Identity Index value, the UE specific DRX, an indication if the UE is configured with Mobile Initiated Connection Only (MICO) mode by the AMF, or the expected UE behavior. The base station may use the UE specific DRX and the UE Identity Index value to determine a paging occasion for RAN paging. The base station may use periodic registration update timer to configure Periodic RNA Update timer. The base station may use an expected UE behaviour to assist the UE RRC state transition decision. 
     A base station may initiate a RRC connection release procedure to transit an RRC state of a UE from RRC connected state to RRC idle state, from an RRC connected state to RRC inactive state, from RRC inactive state back to RRC inactive state when the UE tries to resume, or from RRC inactive state to RRC idle state when the UE tries to resume. The procedure may also be used to release and redirect a UE to another frequency. The base station may provide a suspend configuration when transitioning RRC state of the UE to RRC inactive state. The suspend configuration may comprise at least one of a resume identity, RNA configuration, RAN paging cycle, or network hop chaining count (NCC) wherein the RNA configuration may comprise RNA notification area information, or periodic RNA update timer value. The base station may use the resume identity (e.g., I-RNTI) to identify the UE context when the UE is in RRC inactive state. 
     If a UE sends a request to access a gNB other than a last serving gNB, The gNB receiving the request (receiving gNB) may trigger the retrieve UE context procedure via an Xn interface to get the UE context from the last serving gNB and may also trigger an address indication procedure via an Xn interface including tunnel information for potential recovery of data from the last serving gNB. Upon successful UE context retrieval, the receiving gNB may perform the slice-aware admission control in case of receiving slice information and become the serving gNB. The receiving gNB further may trigger the path switch request via an N2 interface and applicable RRC procedures. After the path switch procedure, the serving gNB may trigger release of the UE context at the last serving gNB by means of the UE context release procedure via an Xn interface. In case the UE is not reachable at the last serving gNB, the receiving gNB may
         fail any AMF initiated UE-associated class  1  procedure which allows the signalling of unsuccessful operation in the respective response message; or   trigger the NAS non delivery indication procedure to report the non-delivery of any NAS PDU received from the AMF for the UE.
 
If the UE accesses a gNB other than the last serving gNB and the receiving gNB does not find a valid UE Context, the receiving gNB may perform establishment of a new RRC connection instead of resumption of the previous RRC connection. the UE context retrieval will also fail and hence a new RRC connection needs to be established if the serving AMF changes.
       

     A UE in RRC inactive state may initiate an RNA update procedure when the UE moves out of the configured RNA. When receiving RNA update request from the UE, the receiving gNB may trigger the retrieve UE context procedure to get the UE context from the last serving gNB and may decide to send the UE back to RRC inactive state, move the UE into an RRC connected state, or send the UE to RRC idle state. In case of periodic RNA update, if the last serving gNB decides not to relocate the UE context, the receiving gNB may fail the retrieve UE context procedure and sends the UE back to RRC inactive state, or to RRC idle state directly by an encapsulated RRC Release message. 
     A last serving base station may configure an RNA to a UE in RRC inactive state. The RNA may cover a single or multiple cells, and/or be contained within a CN registration area; The UE may send a RAN-based notification area update (RNAU) periodically and also send when the cell reselection procedure of the UE selects a cell that does not belong to the configured RNA. 
     An RNA may be configured with:
         List of cells:   List of RAN areas:       

     A base station may provide at least one of RAN area IDs to a UE, where a RAN area is a subset of a CN Tracking Area or equal to a CN Tracking Area. A RAN area is specified by one RAN area ID, which consists of a TAC and optionally a RAN area Code. The base station broadcasts one or more RAN area IDs in the system information. A base station may provide different RNA definitions to different UEs. 
     A UE may monitor paging channels for core network (CN) paging while in RRC idle state. A UE also may monitor paging channels for RAN paging while in RRC inactive state. 
     A base station may broadcast a sidelink SIB. The sidelink SIB may comprise information elements (e.g. resource or frequency) per type of a sidelink service (e.g. sidelink discovery, sidelink communication or V2X communication), or UE type (e.g. pedestrian or vehicle). The information elements may comprise at least one of: 
     Resource pools for reception per frequency; 
     Resource pools for transmission per frequency; 
     Exceptional pools; 
     Syncronization information (e.g. frequency list). 
     Resource selection configuration; 
     Zone configuration; 
     Inter-frequency list information; 
     Synchronization reference type; 
     Threshold for sidelink tx prioritization 
     Anchor carrier frequency list; 
     Threshold for sidelink tx prioritization; 
     Transmission paprameters and Channel Busy Ratio (CBR) configuration; or 
     Packet duplication configuration. 
     A base station may transmit System Information (SI) messages carrying SIBs other than SIB1 on the DL-SCH. The base station may transmit one or more SI messages within periodically occurring time domain windows, referred to as SI-windows. One or more SI-windows may have the same length and may be configured to not overlap in time. The base station may transmit an SI message a number of times within an SI-window. The base station may configure any SIB, except SIB1, to be cell specific or area specific using an indication in SIB1. A cell specific SIB is applicable only within a cell that provides the SIB, while an area specific SIB is applicable within an area referred to as an SI area, which includes one or more cells and may be identified by a system Information Area ID. 
     A UE may apply an SI acquisition procedure to acquire SI upon, for example, cell-selection (e.g., upon power on), cell-reselection, return from out of coverage, after reconfiguration with sync completion, after entering the network from another radio access technology (RAT), upon receiving an indication that system information has changed, upon receiving a public warning system (PWS) notification, and when the UE does not have a valid version of a stored SIB. When a UE acquires a MIB, a SIB1, or an SI message in a serving cell and stores the acquired SI, then the UE may store one or more of the following if present: an associated area scope, a first PLMN identity in a PLMN identity info list, a cell identity, a system Information Area ID, and a value tag. The UE may use a valid stored version of SI, except SI of a MIB, SIB1, SIB6, SIB7 or SIB8, after cell re-selection, upon return from out of coverage, or after the reception of SI change indication. 
     A network may configure a sidelink service (e.g., D2D or V2X) using sidelink configuration parameters. More particularly, a network entity of the network may configure the sidelink service using sidelink configuration parameters. For example, the network entity may be a V2X control function or a proximity service (ProSe) control function or a policy control function (PCF). The network may send the sidelink configuration parameters to a UE via a base station. The sidelik configuration parameters may comprise configuration parameters for sidelink provisioning, sidelink over PC5, and sidelink over Uu interface. In addition or as an alternative the network providing the sidelink configuration parameters to the UE, the sidelink configuration parameters may be pre-configured in the UE, configured in a Subscriber Identify Module (SIM), or using any combination of these techniques. The sidelink configuration parameters may comprise a sidelink control function address and parameters of a PDN connection (and/or PDU session) for communication with a sidelink control function. The sidelink configuration parameters for sidelink over PC5 may comprise at least one of authorization policy, radio parameters for the sidelink over PC5, or other configuration parameters (or policy). An authorization policy may comprise at least one of:
         a list of PLMNs in which the UE is authorized to use the sidelink over PC5 when the UE is served by the base station; or   an indication of whether the UE is authorized to use sidelink over PC5 when the UE is not served by the base station.
 
The radio parameters may comprise radio parameters with geographical area usage constraints.
 
The UE may use the radio parameters to perform the sidelink service over a PC5 reference point when the UE reliably locates itself in a corresponding geographical area to which the radio parameters are to be used within.
 
The other configuration parameters (or policy) may comprise at least one of:
   The mapping of destination layer-2 ID(s) and the V2X services, e.g. provider service identifier (PSID) or intelligent transport systems application identifier (ITS-AID)s of the sidelink application.   The mapping of ProSe per-packet priority (PPPP) and packet delay budget (PDB) for sidelink service (autonomous resources selection mode).   The list of sidelink services, (e.g. PSID or ITS-AIDs) of the sidelink applications, with geographical area(s) that require privacy support.   The mapping of service types (e.g. PSID or ITS-AIDs) to sidelink frequencies for further information) with geographical area(s).   The mapping of service types (e.g. PSID or ITS-AIDs) to Tx Profiles.   The list of sidelink services, (e.g. PSID or ITS-AIDs) of the sidelink applications, allowed to use a specific proSe per-packet priority (PPPR) value.       

       FIG. 19  shows an example procedure performed by a UE to acquire radio resources for a sidelink service while the UE is in RRC idle state or RRC inactive state and has sideline data to transmit. A base station may broadcast a SIB for a sidelink service (e.g., D2D or V2X). The SIB for the sidelink service (sidelink SIB) may indicate a resource pool for sidelink transmission on one or more frequencies. The UE in RRC idle state or RRC inactive state may initiate a procedure to establish an RRC connection based on the sidelink SIB. If the sidelink SIB is broadcast by the cell on which the UE camps and the valid version of the sidelink SIB includes a resource pool for the sidelink transmission on a concerned frequency of the UE (or a desired or required frequency of the UE), the UE in RRC idle state or RRC inactive state may not need to perform a procedure to establish an RRC connection for the sidelink service. The UE may perform the sidelink service with the resource pool on the concerned frequency indicated in the sidelink SIB in RRC idle state or RRC inactive state. If the sidelink SIB is broadcast by the cell on which the UE camps and the valid version of any sidelink SIB does not include a resource pool for the sidelink transmission on a concerned frequency of the UE (or a desired or required frequency of the UE), the UE may initiate the procedure to establish an RRC connection to request the one or more radio resources for the sidelink service to the base station. For example, the UE may need a resource pool on a frequency f1. The base station broadcasts a sidelink SIB that includes a resource pool on a frequency f2 and not on f1. The UE may then initiate the procedure to establish an RRC connection to request the one or more radio resources on the frequency f1 for the sidelink service. 
       FIG. 20  shows two example RRC connection procedures (A and B). Procedure A is performed by a UE in RRC idle state, and procedure B is performed by a UE in RRC inactive state. For establishing the RRC connection, the UE may perform a random access procedure and a contention resolution procedure. For the random access procedure as explained above in  FIG. 13 , the UE may send a Msg 1 with a random access preamble and receive a Msg 2 with a random access response. Upon receiving the random access response, the UE may perform the contention resolution procedure by sending a Msg 3 with an RRC request message and receiving a Msg 4 with an RRC response message. The UE may request radio resources for the sidelink service after establishing the RRC connection. 
     A UE may perform a sidelink UE information procedure for at least one of following purpose:
         to inform a base station that the UE is interested or no longer interested to receive a sidelink data (e.g. for sidelink communication or sidelink discovery, or V2X sidelink communication);   to request assignment or release of transmission resources for a sidelink (e.g. sidelink communication, discovery announcements or V2X sidelink communication or sidelink discovery gaps);   to report parameters related to a sidelink (e.g. sidelink discovery from system information of inter-frequency/PLMN cells); or   to report the synchronization reference used by the UE for a sidelink (e.g. V2X sidelink communication).       

     A UE capable of a sidelink (e.g. sidelink communication or V2X sidelink communication or sidelink discovery) in RRC connected state may initiate a sidelink UE information procedure to indicate the UE is interested in receiving sidelink data (e.g. sidelink communication or V2X sidelink communication or sidelink discovery) in several cases including upon successful connection establishment, upon change of interest, or upon change to a PCell broadcasting a sidelink SIB. 
     A UE capable of a sidelink (e.g. sidelink communication or V2X sidelink communication or sidelink discovery) may initiate a sidelink UE procedure to request assignment of dedicated resources for the concerned (desired or required) sidelink communication transmission or discovery announcements or V2X sidelink communication transmission, or to request sidelink discovery gaps for sidelink discovery transmission or sidelink discovery reception. 
     A UE capable of inter-frequency/PLMN sidelink discovery parameter reporting may initiate a sidelink UE information procedure to report parameters related to a sidelink discovery from system information of inter-frequency/PLMN cells. 
     A UE in RRC idle state that is configured to transmit a sidelink data (e.g. for sidelink communication/V2X sidelink communication/sidelink discovery announcements), may initiate an procedure to establish an RRC connection when one or more sidelink SIBs does not include resources for transmission. 
     A UE may send a sidelink UE information message to a base station via an uplink dedicated control channel (UL-DCCH) message when performing a sidelink UE information procedure. The sidelink UE information may comprise information elements (e.g. resource or frequency) per type of a sidelink service (e.g. sidelink discovery, sidelink communication or V2X communication) or UE type (e.g. pedestrian or vehicle). The information elements may comprise at least one of:
         one or more interested frequencies for a reception via a sidelink;   one or more resource request for a transmission via a sidelink wherein the resource request may comprise at least one of one or more frequencies or one or more destination identies;   one or more frequencies to report;   QoS information for a sidelink to transmit (e.g. Reliability); or   synchronization reference type.       

     An base station may provide a dedicated configuration for a sidelink when a UE is in RRC connected state. The dedicated configuration for a sidelink may comprise at least one of: 
     mode selection information; 
     configuration for a scheduled mode; 
     configuration for UE selected mode: 
     inter-frequency list information; 
     synchronization reference type; 
     threshold for sidelink tx prioritization; 
     transmission paprameters and Channel Busy Ratio (CBR) configuration; 
     packet duplication configuration; or 
     synchronization information (e.g. frequency list). 
     A configuration for a scheduled mode may comprise at least one of: 
     slidelink radio network temporary identifier (RNTI); 
     MAC configuration for a sidelink; 
     scheduling pool information for measurements; 
     modulation coding scheme (MCS); or 
     logical channel group info list. 
     A configuration for UE selected mode may comprise at least one of: 
     dedicated resource pools; 
     sensing configuration; 
     carrier selection configuration; 
       FIG. 21  shows an example procedure for a UE to acquire a sidelink radio resource in RRC connected state from a base station. The UE may request the sidelink radio resource by sending a sidelink UE information message to the base station after an RRC connection is established between the UE and the base station. The base station may provide a dedicated configuration for the sidelink service to the UE based on the sidelink UE information message. The dedicated configuration may comprise at least one of a configuration for scheduled mode or a configuration for UE selected mode. The configuration for UE selection mode may comprise at least one of dedicated resource configuration (e.g. resource pools). 
     In NR, system information (SI) may comprise a MIB and a number of SIBs. The SIBs are divided into minimum SI and other SI. The minimum SI may comprise basic system information required for initial access and information for acquiring other SI. The minimum SI may comprise the MIB and SIB1. Other SIBs may be either periodically broadcast on the DL-SCH, broadcast on-demand on DL-SCH (e.g., upon request from UEs in RRC idle state or RRC inactive state), or sent in a dedicated manner on DL-SCH to UEs in RRC connected state. SIB1 may include information on the availability and scheduling (e.g., mapping of SIBs to SI messages, periodicity, and SI-window size) of the other SIBs with an indication on whether one or more SIBs are provided on-demand and, in such a case, the configuration needed by the UE to perform the SI request. 
       FIG. 22  shows an example procedure performed by a UE to acquire SIB, other than SIB1, in RRC idle or RRC inactive state. The UE may not have valid version of SI of the other SIB in stored SIBs. A base station may provide SI broadcast status information in SIB1 indicating whether the other SIB is broadcast. The UE in RRC idle or RRC inactive state may perform a SI request procedure (e.g., either a 2-step or 4-step SI request procedure) to acquire the SI when the SI broadcast status in the SIB1 is set to ‘not broadcasting’. The UE in RRC in RRC idle or RRC inactive state may acquire the SI message comprising the other SIB. 
       FIG. 23  shows an example procedure performed by a UE to select between a 2-step and 4-step SI request procedure for acquiring an SIB other than SIB1. SIB1 may include an SI request configuration. The SI request configuration may comprise a PRACH preamble and PRACH resource corresponding to an SI message. The UE in RRC idle state or RRC inactive state may perform a 2-step SI request procedure when SIB1 includes an SI request configuration corresponding to the SIB the UE desires to acquire. Otherwise, the UE in RRC idle state or RRC inactive state may perform a 4-step SI request procedure to acquire the SIB the UE desires to acquire. 
       FIG. 24  shows an example SI request signal flow for a 2-step SI request procedure (signal flow A) and for a 4-step SI request procedure (signal flow B). For the 2 step SI request procedure, the UE may determine a PRACH preamble and PRACH resource corresponding to a desired SIB in SI request configuration received via SIB1. The UE may initiate a random access procedure using the PRACH preamble and PRACH resource. Upon receiving the PRACH preamble, the base station may broadcast the desired SIB on the DL-SCH and send an acknowledgement (Ack) for the SI request to the UE. Upon receiving the acknowledgement, the UE in RRC idle state or RRC inactive state may acquire the broadcasted SIB on the DL-SCH. For the 4 step SI request procedure, the UE may initiate transmission of an RRC system info request message. The RRC system info request message may comprise a list of one or more SIBs the UE desires to acquire. The UE may send the RRC system info request message after a random access procedure is successfully completed as shown in  FIG. 24 . Upon receiving the RRC system info request message, the base station may send the one or more SIBs and an acknowledgement (Ack) for the SI request to the UE. Upon receiving the acknowledgement, the UE in RRC idle state or RRC inactive state may acquire the requested SIB. 
       FIG. 25  shows two example procedures for a UE to acquire one or more SIBs in RRC connected state. In the first example procedure (Option 1), the UE in RRC connected state may receive the one or more SIBs in dedicated signaling (e.g., via an RRC reconfiguration message) from the base station. In the second example procedure (Option 2), the UE in RRC connected state may send an SI request message for the one or more SIBs to base station. The base station may send the one or more SIBs to the UE in an RRC message based on the SI request message. 
     In existing technologies, a base station may provide a sidelink SIB. In an example, the sidelink SIB may indicate radio resources (e.g., a resource pool) for sidelink transmission on a frequency. In an example, the sidelink SIB may not indicate radio resources for sidelink transmission. A UE may send a request for configuration parameters of a sidelink when the sidelink SIB does not indicate radio resources (e.g., a resource pool) for sidelink transmission on a frequency of the UE (or a desired or required frequency of the UE). The UE in RRC idle or RRC inactive state may need an RRC connection to send the request and perform a procedure to establish the RRC connection as shown in  FIG. 20  discussed above. In existing technologies, the UE in an RRC connected state may send a sidelink UE information message to request configuration parameters of the sidelink as shown in  FIG. 21  discussed above. Based on the sidelink UE information message, the base station may provide the configuration parameters of the sidelink via a dedicated signaling (e.g., RRC reconfiguration message). When the UE is in RRC inactive or RRC idle state, the procedure to receive the configuration parameters for the sidelink may unnecessarily increase latency for initiating the sidelink service, signaling overhead, and power consumption of the UE. In existing technologies, sidelink transmission experiences increased delay for example when the UE initiates sidelink communications when the sidelink SIB does not indicate radio resources for sidelink transmission the UE intend to use. Example embodiments reduces communications latency for sidelink communications. Example embodiment enables sidelink communications of a UE in RRC idle state or RRC inactive state with lower sidelink communications delay. For example, the delay from a time from a UE being RRC idle state or RRC inactive state until the UE receives sidelink configuration parameters and/or communicates sidelink packets is reduced when sidelink SIB does not indicate radio resources for sidelink transmission the UE intend to use. Example embodiments enables a UE in RRC inactive or RRC idle state to receive sidelink configuration parameters without establishing or resuming an RRC connection when the sidelink SIB does not indicate radio resources for sidelink transmission the UE intend to use. 
     In an example embodiment, a UE may transmit a first request for RRC connection and a second request for configuration parameters of the sidelink in a Msg3. This reduces the delay for a UE to indicate to the base station that the UE needs configuration parameters of a sidelink. For a UE in RRC idle state, a base station may transmit to the UE an RRC setup request message that comprises sidelink configuration parameters. For a UE in RRC inactive state, a base station may transmit to the UE an RRC resume request message that comprises sidelink configuration parameters. This reduces the latency for receiving configuration parameters from a base station compared with existing technologies. Example embodiments may increase the size of initial Msg 3 and/or Msg 4 message sizes and initial signaling overhead, however example embodiments reduces sidelink configuration delay and sidelink packet transmission delay for a UE in RRC idle state or RRC inactive state, for example, when a sidelink SIB does not indicate radio resources for sidelink transmission the UE intend to use. An example, the request may be one bit indication to use configuration parameters for a sidelink stored in UE (inactive) context of the UE. The one bit indication may be an establishment cause. A base station may store configuration parameters for a sidelink of a UE in UE (inactive) context when the UE is in an RRC idle state or an RRC inactive state. Example embodiments reduces size of Msg 3 based on the one bit indication and the configuration parameters stored in the UE context. In an example, the request may comprise sidelink UE information or sidelink bearer information. A UE may indicate particular radio resource or particular radio bearer for a sidelink based on the request. Based on the request, a base station may provide configuration parameters for the particular ratio resource. Example embodiments avoid to waste radio resource for a sidelink based the sidelink UE information. 
     In an example embodiment, to reduce the latency for acquiring configuration parameters for a sidelink service, a UE may determine to send the request for configuration parameters of the sidelink via MSG 3 or MSG 5 when sending an RRC request message or an RRC complete message. The request may comprise at least one of radio resource request information for the sidelink, quality of service (QoS) information for the sidelink, or UE type information (e.g., vehicle UE or pedestrian UE). The request may be a sidelink UE information message specified in above. The RRC request message may be an RRC setup request message, an RRC resume request message, or an RRC re-establishment request message. The RRC complete message may be an RRC setup complete message, an RRC resume complete message, or an RRC re-establishment complete message. Uplink common control channel (UL-CCCH) message may comprise at least one of the RRC request message or the request where the UL-CCCH message sends via signaling radio bearer 0 (SRB0). 
     In this disclosure, a sidelink UE information message may be sidelink UE information. 
     A UE may need additional uplink grant to send a request for configuration parameters of a sidelink as well as an RRC request message in MSG 3. The UE may send MSG 1 comprising a random access preamble in to the base station. The random access preamble may be dedicated to a sidelink and configured by the base station for the UE. Based on the random access preamble, the base station may send MSG 2 to the UE, comprising a response to the random access preamble where the response may comprise an uplink grant. Based on the the random access preamble, the base station may provide additional uplink grant to accommodate a request for configuration parameters of a sidelink as well as an RRC request message in MSG 3. Based on the response, the UE may send MSG 3 comprising an RRC request message and/or a request for configuration parameters of a sidelink. The RRC request message may comprise the request for configuration parameter of the sidelink. Based on the uplink grant in the response, the UE may determine which message or information MSG 3 comprises. For example, the UE may determine to use the uplink grant to send the RRC request message. Based on the remaining grant, the UE may determine to send the request in MSG 3. The RRC request message may comprise UE identity where an RRC setup request message may comprise serving temporary mobile subscriber identity (S-TMSI) and an RRC resume request message may comprise resume identity. 
     Based on a request for configuration parameters of a sidelink, a base station may provide configuration parameters of the sidelink via an RRC response message in MSG 4 or an RRC reconfiguration message to a UE. The configuration parameters of the sidelink may comprise at least one of radio resources for the sidelink, or a configuration to request the radio resource for the sidelink to the base station. Based on the configuration parameters of the sidelink, the UE may communicate via the sidelink. The RRC response message may be an RRC setup message, an RRC resume message or an RRC reestablishment message. 
     In existing technologies, a base station may receive sidelink authorization information of a UE from an AMF when the UE is in RRC connected state.  FIG. 26  illustrates an example of a procedure to receive sidelink authorization information by a base station from an AMF. Based on receiving MSG 4 comprising a response to an RRC request message, the UE may enter into RRC connected state. The UE may send MSG 5 comprising an RRC complete message which may comprise a NAS message where the RRC complete message may be an RRC setup complete or an RRC resume complete message, and the NAS message may be a registration request message or service request message. The NAS message may comprise sidelink capability of the UE. Based on the NAS message in MSG 5, the base station may send an initial UE message comprising the NAS message to an AMF. Based on the NAS message, the AMF may send an initial context setup request comprising sidelink authorization information element (IE) to the base station. The sidelink authorization information may comprise sidelink authorization for one or more service types (e.g., vehicle UE, Pedestrian UE and/or ProSe service). Based on receiving the sidelink authorization information, the base station may store the sidelink authorization information in a UE context of the UE. The base station may need the NAS message sent by the UE to trigger that the AMF provides sidelink authorization information to the base station. In existing technologies, the procedure to receive sidelink authorization information may increase latency. Example embodiments reduces latency to receive sidelink authorization information from an AMF. Example embodiments reduces latency for initiating the sidelink communication and/or receiving configuration parameters for the sidelink in a UE based on the reduced latency to receive the sidelink authorization information. 
     In an example embodiment, a base station may receive Msg 3 from a UE where the Msg 3 comprising the first request for an radio resource control (RRC) connection and the second request for configuration parameters of a sidelink. The base station may send sidelink authorization request to an AMF based on not having sidelink authorization information the UE. This reduces the delay for the base station to indicate to the AMF that the base station needs sidelink authorization information of the UE. Based on the sidelink authorization request, the AMF may provide the sidelink authorization information to the base station. Based on the sidelink authorization information, the base station may provide Msg 4 to the UE where the Msg 4 comprises configuration parameters for a sidelink. This residues latency for receiving configuration parameters and initiating sidelink communication in the UE. 
       FIG. 27  is an example illustration of an enhanced procedure to acquire configuration parameters of a sidelink in accordance with embodiments of the present disclosure. A base station may broadcast a sidelink SIB. The sidelink SIB may not not include radio resources (e.g., a resource pool) for sidelink transmission on a concerned frequency of the UE (or desired or required frequency of the UE). Based on the sidelink SIB, the UE may perform a procedure to establish an RRC connection when the UE is in RRC idle or RRC inactive state. The UE may send an RRC request message to the base station. Based on the RRC request message in RRC inactive state (an RRC resume request message), the base station may perform the retrieve UE context procedure via an Xn interface to get the UE context from a last serving base station of the UE. The base station may have sidelink authorization information of the UE in a UE context. The sidelink authorization information may comprise sidelink authorization for one or more service types. Based on the sidelink authorization information and the request for configuration parameters of the sidelink, the base station may provide configuration parameters of the sidelink via an RRC response message in MSG 4. Based on the configuration parameters of the sidelink, the UE may communicate via the sidelink. 
     In an example of  FIG. 27 , a base station may not have sidelink authorization information of the UE in a UE context of the UE when receiving the RRC request message and the request for configuration parameters. For example, the base station may not have the UE context when the UE is in RRC idle state. The base station may not have sidelink authorization information of the UE in the UE context of the UE when the UE is in RRC inactive state. Based on the RRC request message in RRC inactive state (an RRC resume request message), the base station may perform the retrieve UE context procedure via an Xn interface to get the UE context from the last serving base station. The base station may not have sidelink authorization information of the UE in a UE context of the UE after getting the UE context. Based on that the base station does not have sidelink service authorization information of the UE, the base station may perform a sidelink authorization request procedure by sending a sidelink authorization request for the UE to an AMF. The sidelink authorization request may comprise at least one of a UE identity or one or more sidelink service types to request the sidelink authorization. An NG application (NGAP) message may comprise the sidelink authorization request. For example, the NGAP message may comprise an indication to request service authorization. The base station may store a UE identity in UE context where the UE identity may be S-TMSI. The AMF may use the UE identity to identify the UE. The sidelink authorization request message may comprise NGAP protocol identity (ID) instead of the UE identity. The sidelink service type may indicate at least one of UE type (e.g., vehicle UE or pedestrian UE), cast type (e.g., unicast, groupcast or broadcast), service type (e.g., communication, discovery, V2X or ProSe). Based on the sidelink authorization request message, the AMF may send a sidelink authorization response comprising sidelink authorization information of the UE, to the base station. The sidelink authorization information may comprise sidelink authorization for one or more service types. Based on the sidelink authorization information and the request for configuration parameters, the base station may provide configuration parameters of the sidelink via an RRC response message in MSG 4 where the RRC response message may be an RRC setup message or an RRC resume message. The configuration parameters of the sidelink may comprise at least one of radio resources for the sidelink, or a configuration to request the radio resource for the sidelink to the base station. Based on the configuration parameters of the sidelink, the UE may communicate via the sidelink. 
     In an example embodiment, a UE may not transmit the second request for configuration parameters of a sidelink in Msg 3. For example, a UE may not transmit the second request for configuration parameters of a sidelink in Msg 3 based on not enough uplink grant for the Msg. The UE may transmit Msg 5 comprising the second request. This reduces the delay for a UE to indicate to the base station that the UE needs configuration parameters of a sidelink. A base station may transmit to the UE an RRC response message which is one of: an RRC setup message; or an RRC resume message. Based on the RRC response message, the UE may transmit to the base station an RRC complete message comprising the second request which the RRC complete message is one of: an RRC setup complete message; or an RRC resume complete message. The base station may transmit an RRC complete response message comprising configuration parameters of a sidelink where the RRC complete response message is one of: an RRC reconfiguration message; or an RRC release message. Example embodiments may increase the size of Msg 5 and/or an RRC complete response message sizes and initial signaling overhead, however example embodiments reduces sidelink configuration delay and sidelink packet transmission delay for a UE in RRC idle state or RRC inactive state, for example, when a sidelink SIB does not indicate radio resources for sidelink transmission the UE intend to use. 
     In an example embodiment, a UE may send Msg 3 comprising an indication to request more uplink grant for Msg 5 transmission. Based on the indication, a base station may send more uplink grant to the UE. Based on the more uplink grant, the UE to transmit Msg 5 comprising the second request for configuration parameters of a sidelink. The base station may provide the configuration parameter to the UE. Example embodiment enables sidelink communications of a UE with lower sidelink communications delay as compared with existing technologies. 
       FIG. 28  is an example illustration of an enhanced procedure to acquire configuration parameters of a sidelink in accordance with embodiments of the present disclosure. The UE may perform a procedure to establish an RRC connection when the UE is in RRC idle or RRC inactive state. The UE may send MSG 1 comprising a random access preamble to the base station. Based on the random access preamble, the base station may send MSG 2 to the UE, comprising a response to the random access preamble where the response may comprise an uplink grant. Based on the response, the UE may send MSG 3 comprising an indication that the UE has sidelink data. The indication may be an establishment cause and included in the RRC request message. Based on MSG 3, the base station may send MSG 4. Based on the indication, the base station may provide additional uplink grant to accommodate a request for configuration parameters of a sidelink as well as an RRC complete message in MSG 5. Based on the response, the UE may send MSG 5 comprising an RRC complete message and/or a request for configuration parameters of a sidelink. The RRC complete message may comprise the request for configuration parameter of the sidelink. Based on the uplink grant in the response, the UE may determine which message or information MSG 5 comprises. For example, the UE may determine to use the uplink grant to send the RRC complete message. Based on the remaining grant, the UE may determine to send the request in MSG 5. The base station may have sidelink authorization information of the UE in the UE context or receive the sidelink authorization information of the UE from an AMF described above with respect to  FIG. 26 . The RRC complete message may comprise a NAS message. The sidelink authorization information may comprise sidelink authorization for one or more service types. Based on the sidelink authorization information and the request for configuration parameters of the sidelink, the base station may provide configuration parameters of the sidelink via the first RRC reconfiguration message. The configuration parameters of the sidelink may comprise at least one of radio resources for the sidelink, or a configuration to request the radio resource for the sidelink to the base station. Based on the configuration parameters of the sidelink, the UE may communicate via the sidelink. 
     If a UE has a random access preamble dedicated for a sidelink, the UE may perform a procedure described above with respect to  FIG. 27 . Otherwise, the UE may perform a procedure described above with respect to  FIG. 28 . 
       FIG. 29  is an example a procedure to transition an RRC state of a UE between RRC connected state and RRC inactive state. A base station may perform an RRC release procedure to transition an RRC state of a UE from RRC connected state to RRC inactive state. The base station may store configuration parameters for a uplink (and a downlink) in a UE context (or a UE inactive context), which is used in RRC connected state and suspend signaling or data radio bearers for an uplink (and a downlink) of the UE. The base station may send an RRC release message comprising suspend configuration (or RRC inactive configuration) to transition the RRC state of the UE from RRC connected state to RRC inactive state. The suspend configuration may comprise at least one of a resume identity, ran notification area (RNA) configuration or security parameter (e.g., next hop chaining count (NCC)). Based on the RRC release message comprising the suspend configuration, a UE in RRC connected state may store UE parameters state in the UE context (or the UE inactive context), which is used in RRC connected state and suspend signalling or data radio bearers for a uplink. The UE may enter into RRC inactive state. The UE in RRC inactive state may perform an procedure to establish/resume an RRC connection described above with respect to the procedure B in  FIG. 20 . Based on an RRC resume request message, the base station may perform may trigger the retrieve UE context procedure via an Xn interface to get the UE context from the last serving base station. Based on the UE context, the base station may send an RRC resume message comprising the configuration parameters for a uplink. Based on the RRC resume message, the UE may restore the UE parameters in the UE context and resume the suspended all bearers for the uplink. 
     In existing technologies, a base station needs sidelink UE information from a UE to provide the configuration parameters of the sidelink to the UE. Data volume of the sidelink UE information may be large. A UE in an RRC inactive state needs an RRC connection to send the sidelink UE information having large data volume to the base station. In existing technologies, a base station and a UE may not have mechanism to mange and efficiently use configuration parameters of a sidelink (e.g., sidelink bearer configuration) in an RRC inactive state while the base station and the UE may use efficiently an uplink (or a downlink) configuration by suspending and resuming/restoring bearers or bearer configuration for the uplink (and/or downlink). This inefficient procedure may unnecessarily increase latency for initiating a sidelink service by increasing latency to provide the configuration parameters of a sidelink (a sidelink bearer configuration) to a UE. Example embodiment reduces latency to provide the configuration parameters of the sidelink to the UE. Example embodiment reduces communications latency for sidelink communications. Example embodiment enables sidelink communications of a UE in RRC inactive state with lower sidelink communications delay. For example, the delay from a time from a UE being RRC idle state or RRC inactive state until the UE receives sidelink configuration parameters and/or communicates sidelink packets is reduced when sidelink SIB does not indicate radio resources for sidelink transmission the UE intend to use. 
     In an example embodiment, a base station and a UE may store configuration parameters of a sidelink of a UE in UE (inactive) context when suspending an RRC connection of the UE (e.g., transitioning the UE to an RRC inactive state). This reduces signaling overheads for a request for configuration parameters of a sidelink. The base station may restore the stored configuration parameters of the sidelink in UE context when receiving an RRC resume request message from the UE. The UE may restore the configuration parameters in the UE context. This reduces signaling overheads for a request for configuration parameters of a sidelink compared with existing technologies. Example embodiment enables the UE to indicate uses of one or more configuration parameters stored in the UE context. The UE in an RRC inactive state may send an RRC resume request message comprising an indication for the configuration ammeters stored in the UE context. The indication may indicate one or more configuration parameters stored in the UE context. The base station may restore the one or more configuration parameters. This reduces signaling overheads to indicate configuration parameters the UE intend to use, and reduces signaling overheads due to unnecessary configuration parameters. 
       FIG. 30  is an example illustration of an enhanced procedure for storing sidelink bearer configuration in RRC inactive state in accordance with embodiments of the present disclosure. A base station may provide a sidelink bearer configuration for a UE in RRC connected state. Based on the sidelink bearer configuration, the UE may communicate (transmit or receive sidelink data) via a sidelink. The sidelink bearer configuration may comprise at least one of signaling or data radio bearer identity for a sidelink, QoS information for a sidelink bearer, or radio resource for the sidelink bearer. The radio resource may comprise at least one of a resource pool, configured grant type 1, or configured grant type 2. The base station may perform an RRC release procedure to transition an RRC state of the UE from RRC connected state to RRC inactive state. The base station may store UE parameters for an uplink in a UE context (or a UE inactive context), which is used in RRC connected state, and suspend signaling or data radio bearers for the uplink of the UE. The base station may determine to store sidelink bearer configuration in the UE context and/or suspend sidelink bearers. Based on the determining, the base station may store UE parameters for the sidelink (e.g., sidelink bearer configuration) in the UE context (or UE inactive context). Based on the determining, the base station may indicate in the RRC release message that sidelink bearer configuration is stored in the UE context and/or one or more sidelink bearers are suspended. The base station may comprise one or more sidelink bearer identities in the RRC release message to indicate sidelink bearers suspended or stored in the UE context. Based on the RRC release message, the UE may store the UE parameters for the sidelink (e.g., the sidelink bearer configuration) in the UE context (or the UE inactive context), which is used in RRC connected state. Based on the sidelink bearer configuration, the UE may communicate via the sidelink. 
       FIG. 31  is an example illustration of an enhanced procedure to restore/resume sidelink bearer configuration in RRC inactive state in accordance with embodiments of the present disclosure. A base station and a UE may store a sidelink bearer configuration in a UE context as described above with respect to  FIG. 30 . The UE may perform a procedure to establish an RRC connection as described above with respect to procedure B of  FIG. 20 . The UE may send a request for configuration parameters for a sidelink in MSG 3. The request for configuration parameters may be sidelink bearer information. The MSG 3 or an RRC resume request message in MSG 3 may comprise the request for configuration parameters for the sidelink. The sidelink bearer information may comprise an indication to use the sidelink bearers configured in the UE context for the UE. The UE may use the indication per sidelink bearer. For example, the indication may comprise one or more sidelink bearer identities to indicate one or more sidelink bearers configured in the UE context, the UE intend to restore/resume/modify. For example, the UE may use the indication to request the base station to restore/resume/modify sidelink bearer configuration of one or more sidelink bearers configured in the UE context. The UE may use the indication for all sidelink bearers configured in the UE context. For example, the UE may use the indication to request the base station restore/resume/modify sidelink bearer configuration of all sidelink bearers configured in the UE context. For modification, the indication may comprise at least one of one or more sidelink bearer identities, which the UE intend to modify, and/or requested QoS information for sidelink bearers associated to the sidelink bearer identities. Based on the RRC resume request message, the base station may trigger the retrieve UE context procedure via an Xn interface to get the UE context from the last serving base station. Based on the sidelink bearer information in the MSG 3, the base station may check the UE context and the sidelink bearer configuration configured in the UE context. Based on the sidelink bearer information and/or the UE context, the base station may determine to provide a sidelink bearer configuration to the UE. The sidelink bearer configuration may comprise at least one of signalling or data radio bearer identity for a sidelink, QoS information for a sidelink bearer, or radio resource for the sidelink bearer. The base station may update the sidelink bearer configuration and indicate the update to the UE (e.g., by providing mapping information from old bearer configuration to update bearer configuration). The sidelink bearer configuration may further comprise at least one of QoS information for sidelink bearer, or an indication to restore and/or resume a configuration for one or more sidelink bearers. For example, the indication to restore and/or resume may comprise sidelink bearer identities the base station intends to restore and/or resume. Based on the indication to restore and/or resume, the UE may restore and/or resume sidelink bearers corresponding to the sidelink identities. For example, the indication may be one bit. Based on the indication, the UE may restore and/or resume the sidelink bearer configuration for the sidelink (or sidelink bearers) configured in the UE context. Based on the sidelink bearer configuration, the UE may communicate via the sidelink. 
       FIG. 32  is an example illustration of an enhanced procedure to acquire configuration parameters of a sidelink in RRC inactive state by combining procedures discussed with respect to  FIG. 27  and  FIG. 31  in accordance with embodiments of the present disclosure. A base station and a UE may store a sidelink bearer configuration in a UE context as described above with respect to  FIG. 30 . The UE may perform a procedure to establish an RRC connection as described above with respect to procedure B of  FIG. 20 . The UE may send a request for configuration parameters for a sidelink in MSG 3. The request may comprise at least one of sidelink bearer information and/or a sidelink UE information message. The sidelink UE information message may comprise the sidelink bearer information. Based on the sidelink bearer configuration in the UE context and sidelink data the UE has, the UE may determine which parameters are included in the request. For example, the UE may include the sidelink bearer information to request restoring/resuming/modifying one or more sidelink bearers of the sidelink bearer configuration configured in the UE context, to the base station. The UE may include the sidelink UE information message in the request to request radio resource for sidelink data, to the base station, which is not associated to the sidelink bearer configuration in the UE context. The sidelink bearer information may comprise an indication to use the sidelink bearers configured in the UE context for the UE. For example, the indication may be information for whether sidelink data the UE has is associated to sidelink bearers configured in the UE context for the UE. The UE may comprise the indication based on that all of sidelink data the UE has is associated to the sidelink bearers configured in the UE context for the UE. The indication may comprise one or more sidelink bearer identities, the UE intend to resume/restore, in the sidelink bearers configured in the UE context for the UE. Based on an RRC resume request message, the base station may perform may trigger the retrieve UE context procedure via an Xn interface to get the UE context from the last serving base station. Based on the sidelink bearer information in the MSG 3, the base station may check the UE context and the sidelink bearer configuration configured in the UE context. Based on the sidelink UE information, sidelink bearer information and/or the UE context, the base station may determine to provide a sidelink bearer configuration to the UE. Based on the request for configuration parameters of the sidelink, the base station may determine which parameters is comprised in the sidelink bearer configuration. Based on the sidelink bearer information and/or the UE context, the base station may determine to restore/resume which parameters or sidelink bearers in the sidelink bearer configuration configured in the UE context of the UE. Based on the sidelink UE information message, the base station may determine to configure which parameters or sidelink bearers for sidelink data that is not associated to the sidelink bearer configuration configured in the UE context of the UE. The sidelink bearer configuration may comprise at least one of signalling or data radio bearer identity for a sidelink, QoS information for a sidelink bearer, or radio resource for the sidelink bearer. The base station may update the sidelink bearer configuration and indicate the update to the UE (e.g. by providing mapping information from old bearer configuration to update bearer configuration). The sidelink bearer configuration may further comprise at least one of quality of service information for sidelink bearer, or an indication to restore and/or resume one or more sidelink bearers. The indication to restore and/or resume may comprise sidelink bearer identities the base station intends to restore and/or resume. Based on the sidelink bearer configuration, the UE may communicate via the sidelink. 
     In existing technologies, a UE may perform sidelink communication using preconfigured radio resources or radio resource pool. The UE may perform the RRC re-establishment procedure to reestablish an RRC connection (e.g., based on radio link failure). The UE may perform a cell selection procedure and select a cell based on the cell selection procedure. A base station of the cell may broadcast a sidelink SIB but the sidelink SIB may not indicate radio resources for sidelink transmission the UE intend to use. The UE may send sidelink UE information after reestablishing an RRC connection when sidelink SIB does not indicate radio resources for sidelink transmission the UE intend to use. This inefficient procedure may unnecessarily increase latency for initiating a sidelink service by increasing latency to provide the configuration parameters of a sidelink (a sidelink bearer configuration) to a UE. Example embodiment reduces latency to provide the configuration parameters of the sidelink to the UE. Example embodiment reduces communications latency for sidelink communications. Example embodiment enables sidelink communications of a UE in RRC connected state with lower sidelink communications delay. 
     In an example embodiment, a UE may determine to send a request for configuration parameters of a sidelink when sending an RRC reestablishment request message. The request may comprise at least one of radio resource request information for the sidelink, QoS information for the sidelink, or UE type information (e.g., vehicle UE or pedestrian UE). The request may be a sidelink UE information message as specified in the above. This reduces the latency for receiving configuration parameters from a base station compared with existing technologies. Example embodiments may increase the size of initial Msg 3 and/or Msg 4 message sizes and initial signaling overhead, however example embodiments reduces sidelink configuration delay and sidelink packet transmission delay for a UE in RRC connected state, for example, when a sidelink SIB does not indicate radio resources for sidelink transmission the UE intend to use. 
       FIG. 33  is an example illustration of an enhanced procedure to acquire configuration parameters of a sidelink in RRC connected state in accordance with embodiments of the present disclosure. A base station and a UE may store a sidelink bearer configuration in a UE context similar to those described above with respect to  FIG. 30 . The UE may perform an RRC reestablishment procedure (e.g., due to radio link failure). The UE may send MSG 1 comprising a random access preamble to the base station. The random access preamble may be dedicated to a sidelink and configured by the base station for the UE. Based on the random access preamble, the base station may send MSG 2 to the UE, comprising a response to the random access preamble where the response may comprise uplink grant. Based on the the random access preamble, the base station may provide additional uplink grant to accommodate a request for configuration parameters of a sidelink as well as an RRC reestablishment request message in MSG 3. Based on the response, the UE may send MSG 3 comprising an RRC reestablishment request message and/or the request for configuration parameters of the sidelink. The RRC reestablishment request message may comprise the request for configuration parameter of the sidelink. Based on the uplink grant in the response, the UE may determine which message or information MSG 3 comprises. For example, the UE may determine to use the uplink grant to send the RRC reestablishment request message. Based on the remaining grant, the UE may determine to send the request in MSG 3. The RRC reestablishment request message may comprise a UE identity. The request for configuration parameters may comprise at least one of sidelink bearer information and/or a sidelink UE information message. The UE may determine which parameters of the sidelink bearer configuration and the sidelink UE information message the request comprises. For the determining, the UE may perform a procedure similar to those described above with respect to  FIG. 32 . Based on the RRC reestablishment request message, the base station may perform the retrieve UE context procedure via an Xn interface to get the UE context from the last serving base station. The base station may have sidelink authorization information of the UE in a UE context. The sidelink authorization information may comprise sidelink authorization for one or more service types. Based on the sidelink authorization information and the request for configuration parameters of the sidelink, the base station may provide configuration parameters of the sidelink via an RRC reestablishment message in MSG 4. The configuration parameters of the sidelink may comprise at least one of radio resources for the sidelink, or a configuration to request the radio resource for the sidelink to the base station. Based on the configuration parameters of the sidelink, the UE may communicate via the sidelink. 
     In existing technologies, a UE may perform sidelink communication using preconfigured radio resources or radio resource pool. The UE may perform the RRC re-establishment procedure to reestablish an RRC connection (e.g., based on radio link failure). The UE may perform a cell selection procedure and select a cell based on the cell selection procedure. A base station of the cell may broadcast a sidelink SIB but the sidelink SIB may not indicate radio resources for sidelink transmission the UE intend to use. The UE may send sidelink UE information after reestablishing an RRC connection when sidelink SIB does not indicate radio resources for sidelink transmission the UE intend to use. The base station may not have sidelink authorization information of a UE in a UE context of the UE when receiving an RRC reestablishment request message and a request for configuration parameters. For example, the base station may not have sidelink authorization information of the UE while having the UE context of the UE when the UE is in RRC connected state. In existing technologies, the base station may need to wait Msg 5 comprising NAS message. Based on the NAS message in MSG 5, the base station may send an initial UE message comprising the NAS message to an AMF. Based on the NAS message, the AMF may send an initial context setup request comprising sidelink authorization information element (IE) to the base station. The sidelink authorization information may comprise sidelink authorization for one or more service types (e.g., vehicle UE, Pedestrian UE and/or ProSe service). Based on receiving the sidelink authorization information, the base station may store the sidelink authorization information in a UE context of the UE. The base station may need the NAS message sent by the UE to trigger that the AMF provides sidelink authorization information to the base station. In existing technologies, the procedure to receive sidelink authorization information may increase latency. Example embodiment reduces latency to receive sidelink authorization information from an AMF. Example embodiment reduces latency for initiating the sidelink communication and/or receiving configuration parameters for the sidelink in a UE based on the reduced latency to receive the sidelink authorization information. 
     In an example embodiment, a base station may receive Msg 3 from a UE where the Msg 3 comprising the first request for an radio resource control (RRC) connection reestablishment and the second request for configuration parameters of a sidelink. The base station may send sidelink authorization request to an AMF based on not having sidelink authorization information the UE. This reduces the delay for the base station to indicate to the AMF that the base station needs sidelink authorization information of the UE. Based on the sidelink authorization request, the AMF may provide the sidelink authorization information to the base station. Based on the sidelink authorization information, the base station may provide Msg 4 to the UE where the Msg 4 comprises configuration parameters for a sidelink. This residues latency for receiving configuration parameters and initiating sidelink communication in the UE. 
     In  FIG. 33 , a base station may not have sidelink authorization information of a UE in a UE context of the UE when receiving an RRC reestablishment request message and a request for configuration parameters. For example, the base station may not have sidelink authorization information of the UE while having the UE context of the UE when the UE is in RRC connected state. The base station may perform a sidelink authorization request procedure by sending a sidelink authorization request for the UE to an AMF. The sidelink authorization request may comprise at least one of a UE identity or one or more sidelink service types to request the sidelink authorization. An NG application (NGAP) message may comprise the sidelink authorization request. For example, the NGAP message may comprise an indication to request service authorization. The base station may store a UE identity in UE context where the UE identity may be S-TMSI. The AMF may use the UE identity to identify the UE. The sidelink authorization request message may comprise NGAP protocol identity (ID) instead of the UE identity. The sidelink service type may indicate at least one of UE type (e.g., vehicle UE or pedestrian UE), cast type (e.g., unicast, groupcast or broadcast), service type (e.g., communication, discovery, V2X or ProSe). Based on the sidelink authorization request message, the AMF may send a sidelink authorization response comprising sidelink authorization information of the UE, to the base station. The sidelink authorization information may comprise sidelink authorization for one or more service types. Based on the sidelink authorization information and the request for configuration parameters, the base station may provide configuration parameters of the sidelink via an RRC reestablishment message in MSG 4. The configuration parameters of the sidelink may comprise at least one of radio resources for the sidelink, or a configuration to request the radio resource for the sidelink to the base station. Based on the configuration parameters of the sidelink, the UE may communicate via the sidelink. 
       FIG. 34  is an example illustration of an enhanced procedure to acquire configuration parameters of a sidelink in RRC connected state in accordance with embodiments of the present disclosure. A base station and a UE may store a sidelink bearer configuration in a UE context similar to those described above with respect to  FIG. 30 . The UE may perform an RRC reestablishment procedure (e.g., due to radio link failure). The UE may send MSG 1 comprising a random access preamble to the base station. Based on the random access preamble, the base station may send MSG 2 to the UE, comprising a response to the random access preamble where the response may comprise uplink grant. Based on the response, the UE may send MSG 3 comprising an indication that the UE has sidelink data. The indication may be an establishment cause and included in the RRC reestablishment request message. The request for configuration parameters may comprise at least one of sidelink bearer information and/or a sidelink UE information message. The UE may determine which parameters of the sidelink bearer configuration and the sidelink UE information message the request comprises. For the determining, the UE may perform a procedure similar to those described above with respect to  FIG. 32 . Based on the RRC reestablishment request message, the base station may perform may trigger the retrieve UE context procedure via an Xn interface to get the UE context from the last serving base station. Based on the MSG 3, the base station may send MSG 4. Based on the indication, the base station may provide more uplink grant to accommodate a request for configuration parameters of a sidelink as well as an RRC reestablishment complete message in MSG 5. Based on the response, the UE may send MSG 5 comprising an RRC reestablishment complete message and/or a request for configuration parameters of a sidelink. The RRC reestablishment complete message may comprise the request for configuration parameter of the sidelink. Based on the uplink grant in the response, the UE may determine which message or information MSG 5 comprises. For example, the UE may determine to use the uplink grant to send the RRC reestablishment complete message. Based on the remaining grant, the UE may determine to send the request in MSG 5. The base station may have sidelink authorization information of the UE in the UE context or receive the sidelink authorization information of the UE from an AMF described above with respect to  FIG. 26 . The RRC reestablishment complete message may comprise a NAS message. The sidelink authorization information may comprise sidelink authorization for one or more service types. Based on the sidelink authorization information and the request for configuration parameters of the sidelink, the base station may provide configuration parameters of the sidelink via the first RRC reconfiguration message. The configuration parameters of the sidelink may comprise at least one of radio resources for the sidelink, or a configuration to request the radio resource for the sidelink to the base station. Based on the configuration parameters of the sidelink, the UE may communicate via the sidelink. 
     If a UE has a random access preamble dedicated for a sidelink, the UE may perform a procedure as described above with respect to  FIG. 33 . Otherwise, the UE may perform a procedure as described above with respect to  FIG. 34 . 
     The examples of  FIGS. 33 and 34  may apply to a handover procedure. A UE may perform a procedure to establish an RRC connection with a target base station. The UE may send a request of configuration parameters of a sidelink to the target base station. MSG3 of the RRC connection procedure or an RRC reconfiguration complete message may comprise the request. The target base station may identify the UE. Based on the identifying the UE, the target base station may provide more uplink grant to accommodate the request. For example, based on receiving the normal random access preamble in response to the PDCCH order, the base station may identify the UE. The base station may identify the UE may need configuration parameters of a sidelink based on a UE context. Based on the UE context, the base station may determine to send the configuration parameters of the sidelink to the UE. 
     In existing technologies, a UE in RRC connected state may receive one or more SIBs via dedicated signaling from the base station. The UE in RRC idle or RRC inactive state may receive the one or more SIBs after establishing an RRC connection. The UE in RRC idle or RRC inactive state may need to wait for an RRC connection to be established to receive the one or more SIBs. This may increase the latency for initiating a sidelink service.  FIG. 35  shows an example of the latency for acquiring radio resources for a sidelink service. As shown in  FIG. 35 , a UE may perform a procedure to establish an RRC connection. After security is activated by performing a security mode command procedure, a base station may provide one or more SIBs to the UE in an RRC reconfiguration message. The UE may send an SI request message to the base station to signal to the base station to provide the one or more SIBs to the UE. Example embodiment reduces latency to receive the one or more SIB (e.g., sidelink SIB). 
     In an example embodiment, a UE may determine to send the request for configuration parameters of the sidelink via MSG 3 or MSG 5 when sending an RRC request message or an RRC complete message. The request may comprise a sidelink UE information message specified in above. The request may comprise information to request the sidelink SIB. The information to request the sidelink SIB may be an RRC system info request message or an indication. The indication may be an establishment cause. For example, the establishment cause may be one of sidelink, sidelink request, or sidelink SIB request. This reduces the latency for acquiring a sidelink SIB compared with existing technologies. 
     In an example embodiment, a UE may need more radio resources for a uplink (uplink grant) for the MSG 3. The UE may send a dedicated random access preamble in MSG 1 of the RRC connection procedure to request a grant for additional radio resources to accommodate the RRC request message and the request. The base station may configure the dedicated random access preamble for the sidelink service via broadcast signaling or dedicated signaling. Example embodiment enables the UE to transmit a request of configuration parameters of a sidelink in MSG 3 of the RRC connection procedure 
     In an example embodiment, a UE may need more radio resources for a uplink (uplink grant) for the MSG 5. The UE may send an indication in MSG 3 of the RRC connection procedure that the UE has sidelink data to transmit. The indication may be an establishment cause. For example, the establishment cause may be one of sidelink, sidelink request, or sidelink SIB request. Example embodiment enables the UE to transmit a request of configuration parameters of a sidelink in MSG 5 of the RRC connection procedure 
     Based on the request, a base station may provide configuration parameters of the sidelink via an RRC response message in MSG 4 of the RRC connection procedure or an RRC reconfiguration message. The configuration parameters of the sidelink may comprise the sidelink SIB. The base station may provide the sidelink SIB via a physical message or a MAC PDU. The base station may provide the sidelink SIB via the other message after the RRC connection is established, where the other message may be an RRC reconfiguration message or other type of RRC message. For example, the base station may send the RRC response message together with the configuration parameters of the sidelink. For example, the base station may include the configuration parameters of the sidelink in the RRC response message. The base station may provide the sidelink SIB via a separate message from the RRC response message. The separate message may be a physical message, a MAC message (e.g., a MAC PDU). The UE in an RRC idle or an RRC inactive state may stay in the same RRC state after receiving the sidelink SIB via the physical message or the MAC message without RRC state change. The UE in an RRC idle or an RRC inactive state may enter into or stay in an RRC idle or an RRC inactive state after receiving the RRC release message. 
       FIG. 36  shows an example of enhanced UE behavior for requesting a sidelink SIB in accordance with embodiments of the present disclosure. A UE in an RRC idle or an RRC inactive state may send MSG 3 of the RRC connection procedure to a base station. The MSG 3 may comprise at least one of an RRC request message or a request of configuration parameters of a sidelink. The request of configuration parameters of a sidelink may comprise information to request a sidelink SIB. Based on the MSG 3, the base station may provide configuration parameter of a sidelink. The configuration parameter may comprise the sidelink SIB. 
     In existing technologies, a UE may have sidelink data to transmit while not having uplink data to transmit. Based on the sidelink data, the UE may perform a procedure to establish an RRC connection described above with respect to  FIG. 20 . Based on the sidelink data, the UE in RRC connected state may send a sidelink UE information message to the base station. Based on the sidelink UE information message, the base station may provide configuration parameters for a sidelink to the UE where the configuration parameters may comprise resource pool. The base station may provide resource pool for the sidelink transmission on all concerned frequencies of the UE (or all desired or required frequencies of the UE). During or after the procedure, the base station may not know which data to transmit (e.g., uplink data or sidelink data), which the UE has. The base station may unnecessarily establish or maintain the RRC connection while the UE has sidelink data not uplink data. The procedure may increase signaling overhead, and power consumption to establish/maintain unnecessarily the RRC connection. Example embodiment reduces signaling overheads and power consumption to maintain unnecessarily the RRC connection. 
     In an example embodiment, a UE may send data information to a base station. The data information may indicates that the UE does not have uplink data to transmit. A request of configuration parameters of a sidelink or an RRC message may comprise the data information where the RRC message may be an RRC request message or an RRC complete message. For example, a sidelink UE information message may comprise the data information. Based on the request comprising the data information, the base station may determine not to establish an RRC connection or to release the RRC connection. This avoid to establish/maintain unnecessarily an RRC connection. 
     A UE in RRC connected state may send the data information to a base station. Based on the data information, the base station may determine to release an RRC connection and send an RRC release message to the UE. 
     data information may indicate at least one of: 
     the UE does not have any data to transmit (e.g. uplink data or sidelink data); 
     the UE completes sidelink data transmission; or 
     the UE does not need radio resource for a sidelink. 
       FIG. 37  shows an example of enhanced procedure to manage RRC connection in accordance with embodiments of the present disclosure. A UE may send MSG 3 comprising an RRC request message and an request of configuration parameters of a sidelink. Based on the request, the base station may determine to provide radio resources for a sidelink which is allowed to use in RRC idle or RRC inactive to the UE. The radio resources for the sidelink may comprise at least one of resource pool, configured grant type 1 or configured type 2. Based on the determining, the data information and the base station does not have downlink data for the UE, the base station may determine not to establish the RRC connection and send an RRC release message to the UE. The RRC release message may comprising configuration parameters for a sidelink. The configuration parameters for the sidelink may comprise the radio resource for the sidelink. Based on the RRC release message, the UE may enter into RRC idle or RRC inactive state. Based on the configuration parameter, the UE in RRC idle or RRC inactive may communicate via the sidelink. 
       FIG. 38  shows an example of enhanced procedure to manage RRC connection in accordance with embodiments of the present disclosure. A UE may send MSG 5 comprising an RRC complete message and an request of configuration parameters of a sidelink. Based on the request, the base station may determine to provide radio resources for a sidelink which is allowed to use in RRC idle or RRC inactive to the UE. The radio resources for the sidelink may comprise at least one of resource pool, configured grant type 1 or configured type 2. Based on the determining, the data information and the base station does not have downlink data for the UE, the base station may determine to release the RRC connection and send an RRC release message to the UE. The RRC release message may comprising configuration parameters for a sidelink. The configuration parameters for the sidelink may comprise the radio resource for the sidelink. Based on the RRC release message, the UE may enter into RRC idle or RRC inactive state. Based on the configuration parameter, the UE in RRC idle or RRC inactive may communicate via the sidelink. 
     The example of enhanced procedure to manage RRC connection in  FIG. 37  may apply to enhanced UE behavior for requesting a sidelink SIB described above with respect to  FIG. 36 .  FIG. 39  shows an example of enhanced procedure to manage RRC connection for a sidelink SIB. A UE in an RRC idle or an RRC inactive state may send MSG 3 of the RRC connection procedure to a base station. The MSG 3 may comprise at least one of an RRC request message or a request of configuration parameters of a sidelink. The request of configuration parameters of a sidelink may comprise at least one of information to request a sidelink SIB specified above or a sidelink UE information message specified in above. The request may comprise data information specified in above. Based on the MSG 3, the base station may provide configuration parameter of a sidelink. The configuration parameter may comprise the sidelink SIB. The base station may provide may provide the sidelink SIB specified above. Based on the MSG 3, the base station may determine not to establish an RRC connection and send an RRC release message similar to those described above with respect to  FIG. 37 . For example, the base station may determine to provide resource pool on concerned frequencies of the UE in the sidelink SIB. Based on the determining, the base station may not to establish the RRC connection and send the RRC release message. Based on the RRC release message, the UE may enter into RRC idle or RRC inactive state. Based on the sidelink SIB, the UE in RRC idle or RRC inactive may communicate via the sidelink. 
     The example of enhanced procedure to manage RRC connection in  FIG. 39  may apply to enhanced UE behavior for requesting a sidelink SIB described above.  FIG. 41  shows an example of enhanced procedure to manage RRC connection for a sidelink SIB. A UE in an RRC connected state may send MSG 5 of the RRC connection procedure to a base station. The MSG 5 may comprise at least one of an RRC complete message or a request of configuration parameters of a sidelink. The request of configuration parameters of a sidelink may comprise at least one of information to request a sidelink SIB specified above or a sidelink UE information message specified in above. The request may comprise data information specified in above. Based on the MSG 5, the base station may provide configuration parameter of a sidelink. The configuration parameter may comprise the sidelink SIB. The base station may provide may provide the sidelink SIB specified above. Based on the MSG 5, the base station may determine to release an RRC connection and send an RRC release message similar to those described above with respect to  FIG. 38 . For example, the base station may determine to provide resource pool on concerned frequencies of the UE in the sidelink SIB. Based on the determining, the base station may determine to release an RRC connection and send an RRC release message. Based on the RRC release message, the UE may enter into RRC idle or RRC inactive state. Based on the sidelink SIB, the UE in RRC idle or RRC inactive may communicate via the sidelink. 
     In existing technologies, a base station may provide configuration parameters for a sidelink to a UE in RRC connected state. The configuration parameters for the sidelink may comprise at least one of radio resource for a sidelink or sidelink bearer configuration. Based on an RRC release message by the base station or radio link failure, the UE may enter into RRC idle or RRC inactive state. The UE in RRC idle or RRC inactive state may not determine whether the configuration parameters to use. The uncertainty may cause a procedure to send sidelink UE information requesting configuration parameters of sidelink. This causes the UE to establish or resume an RRC connection. Example embodiment reduces signaling overheads to send the sidelink UE information and to establish or resume the RRC connection. 
     In an example embodiment, a base station may provide one or more conditions to verify a validity of radio resource for a sidelink or sidelink bearer configuration in the configuration parameters. The radio resource may comprise at least one of a resource pool, configured grant type 1, or configured grant type 2. The configuration parameters may comprise the conditions. The conditions may comprise at least one of one or more service types of a sidelink, one or more frequencies, a time duration, or one or more RRC states. The condition may be associated to one or more radio resource, or one or more sidelink bearers. For example, the sidelink service type may indicate at least one of UE type (e.g., vehicle UE or pedestrian UE), cast type (e.g., unicast, groupcast or broadcast), service type (e.g., communication, discovery, V2X or ProSe). The RRC state may be RRC idle, RRC inactive or RRC connected state. This avoid the uncertainty for configuration parameters of a sidelink. Example embodiment enables the UE to determine to recuse the configuration parameters in the UE context. For example, based on the configuration parameters, the UE may determine to transmit sidelink data via the radio resource for the sidelink in the configuration parameters. For example, based on the conditions associated to radio resource, the UE may determine to transmit sidelink data via the radio resource. Based on the conditions, the UE may determine which radio resources in the configuration parameters to use for sidelink transmission. The UE may store the configuration parameters in a UE context. Based on the conditions, the UE may determine remove radio resource or sidelink bearer configuration of the configuration parameters in the UE context. For example, based on the conditions not being met, the UE may remove radio resource or sidelink bearer configuration of the configuration parameters in the UE context. The base station may provide separate conditions to remove. Based on the conditions to remove being met, the UE may remove the radio resource or the sidelink bearer configuration of the configuration parameters in the UE context. The UE may remove the radio resource or the sidelink bearer configuration corresponding the condition. 
     A UE may send an RRC request message, to establish an RRC connection and a request for configuration parameters of a sidelink, to a base station. In response to the RRC request message and the request, the UE may receive an RRC response message comprising the configuration parameters of the sidelink. The UE may communicate via the sidelink based on the configuration parameters. The RRC request message may be an RRC setup request message, an RRC resume request message, or an RRC re-establishment request message. Uplink common control channel message may comprise at least one of the RRC request message or the request. The request for the configuration parameters of the sidelink may comprise at least one of sidelink UE information or sidelink bearer information. The sidelink UE information may comprise at least one of radio resource request information for the sidelink, quality of service (QoS) information for the sidelink, UE type information. The sidelink bearer information may comprise an indication to use sidelink bearers configured in a UE context for the UE. The indication may be an establishment cause for a sidelink. The UE may send a random access preamble dedicated for the sidelink to establish the RRC connection. The UE may determine to send the request, or the RRC request message based on receiving a response to the random access preamble from the base station. The configuration parameters of the sidelink may indicate at least one of a radio resource for the sidelink, a configuration to request the radio resource for the sidelink to the base station, or a sidelink bearer configuration. The sidelink bearer configuration may comprise a least one of quality of service information for a bearer or an indication to restore and/or resume one or more sidelink bearers. The configuration parameters may indicate at least of a resource pool, a configured grant type 1, or a configured grant type 2. The UE may store the configuration parameters of the sidelink in a UE context. The UE may communicate via the sidelink based on the configuration parameter stored in the UE context. The configuration parameters may comprise one or more conditions to verify a validity of a radio resource for the sidelink. The UE may determine to transmit sidelink data via the radio resource based on one or more conditions. One or more conditions may comprise at least one of a service type of the sidelink, a frequency, a time duration, or an RRC state. The UE may remove the configuration parameters of the sidelink in a UE context based on the one or more conditions not being met. The RRC response message may be an RRC setup message, an RRC resume message, an RRC release message, or an RRC reestablishment message. The request for the configuration parameters or the RRC request message may indicate the UE does not have uplink data to transmit to the base station where the RRC response message may an RRC release message. The request for the configuration parameters or the RRC request message may comprise a request for system information of the sidelink. The configuration parameters of the sidelink may comprise the system information of the sidelink. 
     A base station may receive an RRC request message, to establish an RRC connection and a request for configuration parameters of a sidelink, from a UE. In response to the RRC request message and the request, the base station may send an RRC response message comprising the configuration parameters of the sidelink. The RRC request message may be an RRC setup request message, an RRC resume request message, or an RRC re-establishment request message. Uplink common control channel message may comprise the RRC request message and the request. The RRC response message may be an RRC setup message, an RRC resume message, an RRC release message, or an RRC reestablishment message. The request for the configuration parameters of the sidelink comprises at least one of sidelink UE information or sidelink bearer information. The sidelink UE information may comprise at least one of radio resource request information for the sidelink, quality of service (QoS) information for the sidelink or UE type information. The sidelink bearer information may comprise an indication to use sidelink bearers configured in a UE context for the UE. The indication may be an establishment cause for a sidelink. The base station may receive a random access preamble dedicated for the sidelink to establish the RRC connection. The base station may send a response to a random access preamble wherein the response may comprise radio resource/grant to accommodate the RRC request message and the request. The configuration parameters of the sidelink may indicate at least one of a radio resource for the sidelink, a configuration to request the radio resource for the sidelink to the base station or a sidelink bearer configuration. The sidelink bearer configuration may comprise a least one of quality of service information for a bearer or an indication to restore and/or resume one or more sidelink bearers. The configuration parameters may indicate at least of a resource pool, a configured grant type 1 or a configured grant type 2. The base station may store the configuration parameters of the sidelink in a UE context. The configuration parameters may comprise one or more conditions to verify a validity of a radio resource for the sidelink. One or more conditions may comprise at least one of a service type of the sidelink, a frequency, a time duration or an RRC state. The request for the configuration parameters or the RRC request message may indicate the UE does not have uplink data to transmit to the base station. Based on the indicating, the base station may determine to send an RRC release message to the UE. The request for the configuration parameters or the RRC request message may comprise a request for system information of the sidelink. The configuration parameters of the sidelink may comprise the system information of the sidelink. Based on the request, the base station may send a sidelink authorization request for the UE to access and mobility management function (AMF). The sidelink authorization request may comprise at least one of an UE identity, an indication to request authorization for a sidelink or one or more sidelink service types to request the sidelink authorization. The base station may receive a sidelink authorization response wherein the sidelink authorization response may comprise sidelink authorization information of the UE. Based on the sidelink authorization information, the base station may send the configuration parameters to the UE. 
     A UE may send an RRC complete message and a request for configuration parameters of a sidelink, to a base station. In response to the RRC complete message and the request, the UE may receive an RRC message comprising the configuration parameters of the sidelink. The UE may communicate via the sidelink based on the configuration parameters. The RRC complete message may be an RRC setup complete message, an RRC resume complete message, or an RRC re-establishment complete message. The RRC message may be an RRC reconfiguration message or an RRC release message. The request for the configuration parameters of the sidelink may comprise at least one of sidelink UE information or sidelink bearer information. The sidelink UE information may comprise at least one of radio resource request information for the sidelink, quality of service (QoS) information for the sidelink or UE type information. The sidelink bearer information may comprise an indication to use sidelink bearers configured in a UE context for the UE. The UE may send an RRC request message to the base station. The RRC request message may be an RRC setup request message, an RRC resume request message, or an RRC re-establishment request message. The RRC request message may indicate that the UE has sidelink data where the indicating may be an establishment cause for a sidelink. The UE may determine to send the request or the RRC complete message based on receiving a response to the RRC request message from the base station. The response may be an RRC setup message, an RRC resume message, an RRC release message, or an RRC reestablishment message. The configuration parameters of the sidelink may indicate at least one of a radio resource for the sidelink, a configuration to request the radio resource for the sidelink to the base station or a sidelink bearer configuration. The sidelink bearer configuration may comprise a least one of quality of service information for a bearer or an indication to restore and/or resume one or more sidelink bearers. The configuration parameters may indicate at least of a resource pool, a configured grant type 1 or a configured grant type 2. The UE may store the configuration parameters of the sidelink in a UE context. The UE may communicate via the sidelink based on the configuration parameter stored in the UE context. The configuration parameters may comprise one or more conditions to verify a validity of a radio resource for the sidelink. The UE may determine to transmit sidelink data via the radio resource based on one or more conditions. One or more conditions may comprise at least one of a service type of the sidelink, a frequency, a time duration or an RRC state. The UE may remove the configuration parameters of the sidelink in a UE context based on the one or more conditions not being met. The request for the configuration parameters or the RRC complete message may indicate the UE does not have uplink data to transmit to the base station where the RRC message may be an RRC release message. The request for the configuration parameters or the RRC complete message may comprise a request for system information of the sidelink. The configuration parameters of the sidelink may comprise the system information of the sidelink. 
     A base station may receive an RRC complete message and a request for configuration parameters of a sidelink, to a UE. In response to the RRC complete message and the request, the base station may send an RRC message comprising the configuration parameters of the sidelink. The RRC complete message may be an RRC setup complete message, an RRC resume complete message, or an RRC re-establishment complete message. The RRC message may be an RRC reconfiguration message or an RRC release message. The request for the configuration parameters of the sidelink may comprise at least one of sidelink UE information or sidelink bearer information. The sidelink UE information may comprise at least one of radio resource request information for the sidelink, quality of service (QoS) information for the sidelink or UE type information. The sidelink bearer information may comprise an indication to use sidelink bearers configured in a UE context for the UE. The base station may receive an RRC request message to the base station. The RRC request message may be an RRC setup request message, an RRC resume request message, or an RRC re-establishment request message. The RRC request message may indicate that the UE has sidelink data where the indicating may be an establishment cause for a sidelink. The base station may send a response to an RRC request message wherein the response may comprise radio resource/grant to accommodate the RRC complete message and the request where the response may be an RRC setup message, an RRC resume message, an RRC release message, or an RRC reestablishment message. The configuration parameters of the sidelink may indicate at least one of a radio resource for the sidelink, a configuration to request the radio resource for the sidelink to the base station or a sidelink bearer configuration. The sidelink bearer configuration may comprise a least one of quality of service information for a bearer or an indication to restore and/or resume one or more sidelink bearers. The configuration parameters may indicate at least of a resource pool, a configured grant type 1 or a configured grant type 2. The base station may store the configuration parameters of the sidelink in a UE context. The configuration parameters may comprise one or more conditions to verify a validity of a radio resource for the sidelink. One or more conditions may comprise at least one of a service type of the sidelink, a frequency, a time duration or an RRC state. The request for the configuration parameters or the RRC complete message may indicate the UE does not have uplink data to transmit to the base station. Based on the indicating, the base station may determine to send an RRC release message to the UE. The request for the configuration parameters or the RRC complete message may comprise a request for system information of the sidelink. The configuration parameters of the sidelink may comprise the system information of the sidelink. Based on sidelink authorization information, the base station may send the configuration parameters to the UE. 
       FIG. 41  is a flow diagram of an aspect of an example embodiment of the present disclosure. At  4110 , a wireless device transmits, to a base station, a message. The message comprises: a first request for an radio resource control (RRC) connection; and a second request for configuration parameters of a sidelink of the wireless device. At  4120 , the configuration parameters of the sidelink are received. At  4130 , the wireless device communicates, via the sidelink, based on the configuration parameters. 
       FIG. 42  is a flow diagram of an aspect of an example embodiment of the present disclosure. At  4210 , a base station receives, from a wireless device, a message. The message comprises: a first request for an radio resource control (RRC) connection; and a second request for configuration parameters of a sidelink of the wireless device. At  4220 , the configuration parameters of the sidelink are transmitted.