Patent Publication Number: US-2023137891-A1

Title: Quality of experience measurement reporting and multi-rat handover

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 USC § 119(e) from U.S. Provisional Patent Application No. 63/275,757, filed on Nov. 4, 2021 (“the provisional application”); the content of the provisional patent application is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to 5G, which is the 5 th  generation mobile network. It is a new global wireless standard after 1G, 2G, 3G, and 4G networks. 5G enables networks designed to connect machines, objects and devices. 
     The invention includes providing various capabilities for measuring and/or creating Quality of Experience (QoE) measurement reports when a user equipment (UE) is connected to radio access networks (RANs) associated with one of a plurality of radio access technologies (RATs) (e.g., NR, LTE, etc.). The invention can enhance existing inter-RAT handover processes to enable continuity in QoE measurement/reporting when the RAT associated with a serving gNB changes during the handover. 
     SUMMARY OF THE INVENTION 
     In an embodiment, the invention provides a method of quality of experience (QoE) measurement and reporting in a multi-radio access technology (RAT) handover includes receiving, by a user equipment (UE) from a first base station (BS) of a first RAT, first QoE configuration parameters, performing, by the UE, first QoE measurements and second QoE measurements, based on the first QoE configuration parameters, transmitting, to the first BS, one or more first QoE reports based on the first QoE measurements and based on a first format, receiving a handover command, from the first BS, indicating handover from the first BS to a second BS of a second RAT and transmitting, to the second BS, one or more second QoE reports based on the second QoE measurements and based on a second format. 
     The first format may be based on one or more first quality of experience (QoE) metrics and the second format is based on one or more second QoE metrics. The handover command may comprise second quality of experience (QoE) configuration parameters and the second format may be based on the second QoE configuration parameters. The handover command may indicate handover from a first cell of the first base station (BS) to a second cell of the second BS and may comprise configuration parameters, of the second cell, including the second quality of experience (QoE) configuration parameters. For that matter, the handover command may indicate handover from a first cell of the first base station (BS) to a second cell of the second BS. The first format may be based on the first quality of experience (QoE) configuration parameters. 
     The first radio access technology (RAT) may be new radio (NR) and alternatively, may be long term evolution (LTE). The second radio access technology (RAT) may be new radio (NR) and alternatively, may be long term evolution (LTE). The invention provides for transmitting a handover request message from the first base station (BS) to the second BS. A handover acknowledge message may be transmitted from the second base station (BS) to the first BS. Receiving the handover command can occur in response to the first base station (BS) receiving the handover acknowledge message from the second BS. 
     The invention may also include receiving cell measurement configuration parameters of a plurality of cells comprising the second cell. The cell measurement configuration parameters may comprise reference signal configuration parameters and measurement reporting configuration parameters. The invention can include performing, based on the cell configuration parameters, radio resource management (RRM) measurements for the plurality of cells comprising the second cell and transmitting RRM measurement reports, based on the RRM measurements, to the first base station. A handover request message can be transmitted by the first base station (BS) to the second BS based on the radio resource management (RRM) measurement reports. A quality of experience (QoE) measurement report can be created for transmission via one or more radio resource control (RRC) messages. 
     The quality of experience (QoE) measurement report can be associated with a QoE-related signaling radio bearer (SRB). The quality of experience (QoE)-related signaling radio bearer (SRB) may be SRB4. The quality of experience (QoE)-related signaling radio bearer (SRB) can have a priority that is lower than a second SRB associated with an uplink common control channel logical channel. The one or more resource control (RRC) messages may comprise a measurement report application layer information element (MeasReportappLayer IE) comprising the QoE measurement report. For that matter, the quality of experience (QoE) measurement report may comprise an identifier associated with the QoE configuration. 
     In an embodiment, the invention provides A method of quality of experience (QoE) measurement and reporting in a multi-radio access technology (RAT) handover. The method includes receiving, by a user equipment (UE) from a first base station (BS) of a first RAT, QoE configuration parameters, performing, by the UE, first QoE measurements and second QoE measurements, based on the QoE configuration parameters, transmitting, to the first BS, one or more first QoE reports based on the first QoE measurements, receiving a handover command, from the first BS, indicating a handover from the first BS to a second BS of a second RAT and discarding the second measurements in response to the handover. 
     The discarding of the second measurements may be based on the handover being a multi-radio access technology (RAT) handover. The handover command may indicate the handover from a first cell of the first base station (BS) to a second cell of the second BS. For that matter, the first radio access technology (RAT) may be new radio (NR). The first radio access technology (RAT) may be long term evolution (LTE). The second radio access technology (RAT) may be new radio (NR). The second radio access technology (RAT) may be long term evolution (LTE). A handover request message may be transmitted from the first base station (BS) to the second BS. 
     A handover acknowledge message may be transmitted from the second base station (BS) to the first BS. Receiving the handover command may be based on the first base station (BS) receiving the handover acknowledge message from the second BS. The invention can include receiving cell measurement configuration parameters of a plurality of cells comprising the second cell. The cell measurement configuration parameters may comprise reference signal configuration parameters and measurement reporting configuration parameters. In one form the invention can include, based on the cell configuration parameters, radio resource management (RRM) measurements for the plurality of cells and transmitting the RRM measurement reports to the first base station. 
     A handover request message may be transmitted by the first base station (BS) to the second BS based on the radio resource management (RRM) measurement reports. A quality of experience (QoE) measurement report may be created for transmission via one or more radio resource control (RRC) messages. The quality of experience (QoE) measurement report may be associated with a QoE-related signaling radio bearer (SRB). The QoE-related signaling radio bearer (SRB) may be SRB4. A quality of experience (QoE)-related signaling radio bearer (SRB) may have a priority that is lower than a second SRB associated with an uplink common control channel logical channel. One or more resource control (RRC) messages may comprise a measurement report application layer information element (MeasReportappLayer IE) comprising the QoE measurement report. For that matter, the quality of experience (QoE) measurement report may comprise an identifier associated with the QoE configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows an example of a system of mobile communications according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  2 A  and  FIG.  2 B  show examples of radio protocol stacks for user plane and control plane, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  3 A ,  FIG.  3 B  and  FIG.  3 C  show example mappings between logical channels and transport channels in downlink, uplink and sidelink, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  4 A ,  FIG.  4 B  and  FIG.  4 C  show example mappings between transport channels and physical channels in downlink, uplink and sidelink, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  5 A ,  FIG.  5 B ,  FIG.  5 C  and  FIG.  5 D  show examples of radio protocol stacks for NR sidelink communication according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  6    shows example physical signals in downlink, uplink and sidelink according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  7    shows examples of Radio Resource Control (RRC) states and transitioning between different RRC states according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  8    shows example frame structure and physical resources according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  9    shows example component carrier configurations in different carrier aggregation scenarios according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  10    shows example bandwidth part configuration and switching according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  11    shows example four-step contention-based and contention-free random access processes according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  12    shows example two-step contention-based and contention-free random access processes according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  13    shows example time and frequency structure of Synchronization Signal and Physical Broadcast Channel (PBCH) Block (SSB) according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  14    shows example SSB burst transmissions according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  15    shows example components of a user equipment and a base station for transmission and/or reception according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  16    shows an example inter-RAT handover according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  17 A  shows an example mobility from NR with successful operation according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  17 B  shows an example mobility from NR with failure according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  18    shows an example process according to some aspects of some of various exemplary embodiments of the present disclosure. 
         FIG.  19    shows an example process according to some aspects of some of various exemplary embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows an example of a system of mobile communications  100  according to some aspects of some of various exemplary embodiments of the present disclosure. The system of mobile communication  100  may be operated by a wireless communications system operator such as a Mobile Network Operator (MNO), a private network operator, a Multiple System Operator (MSO), an Internet of Things (IOT) network operator, etc., and may offer services such as voice, data (e.g., wireless Internet access), messaging, vehicular communications services such as Vehicle to Everything (V2X) communications services, safety services, mission critical service, services in residential, commercial or industrial settings such as IoT, industrial IOT (IIOT), etc. 
     The system of mobile communications  100  may enable various types of applications with different requirements in terms of latency, reliability, throughput, etc. Example supported applications include enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine Type Communications (mMTC). eMBB may support stable connections with high peak data rates, as well as moderate rates for cell-edge users. URLLC may support application with strict requirements in terms of latency and reliability and moderate requirements in terms of data rate. Example mMTC application includes a network of a massive number of IoT devices, which are only sporadically active and send small data payloads. 
     The system of mobile communications  100  may include a Radio Access Network (RAN) portion and a core network portion. The example shown in  FIG.  1    illustrates a Next Generation RAN (NG-RAN)  105  and a 5G Core Network (5GC)  110  as examples of the RAN and core network, respectively. Other examples of RAN and core network may be implemented without departing from the scope of this disclosure. Other examples of RAN include Evolved Universal Terrestrial Radio Access Network (EUTRAN), Universal Terrestrial Radio Access Network (UTRAN), etc. Other examples of core network include Evolved Packet Core (EPC), UMTS Core Network (UCN), etc. The RAN implements a Radio Access Technology (RAT) and resides between User Equipments (UEs)  125  and the core network. Examples of such RATs include New Radio (NR), Long Term Evolution (LTE) also known as Evolved Universal Terrestrial Radio Access (EUTRA), Universal Mobile Telecommunication System (UMTS), etc. The RAT of the example system of mobile communications  100  may be NR. The core network resides between the RAN and one or more external networks (e.g., data networks) and is responsible for functions such as mobility management, authentication, session management, setting up bearers and application of different Quality of Services (QoSs). The functional layer between the UE  125  and the RAN (e.g., the NG-RAN  105 ) may be referred to as Access Stratum (AS) and the functional layer between the UE  125  and the core network (e.g., the 5GC  110 ) may be referred to as Non-access Stratum (NAS). 
     The UEs  125  may include wireless transmission and reception means for communications with one or more nodes in the RAN, one or more relay nodes, or one or more other UEs, etc. Example of UEs include, but are not limited to, smartphones, tablets, laptops, computers, wireless transmission and/or reception units in a vehicle, V2X or Vehicle to Vehicle (V2V) devices, wireless sensors, IoT devices, IIOT devices, etc. Other names may be used for UEs such as a Mobile Station (MS), terminal equipment, terminal node, client device, mobile device, etc. 
     The RAN may include nodes (e.g., base stations) for communications with the UEs. For example, the NG-RAN  105  of the system of mobile communications  100  may comprise nodes for communications with the UEs  125 . Different names for the RAN nodes may be used, for example depending on the RAT used for the RAN. A RAN node may be referred to as Node B (NB) in a RAN that uses the UMTS RAT. A RAN node may be referred to as an evolved Node B (eNB) in a RAN that uses LTE/EUTRA RAT. For the illustrative example of the system of mobile communications  100  in  FIG.  1   , the nodes of an NG-RAN  105  may be either a next generation Node B (gNB)  115  or a next generation evolved Node B (ng-eNB)  120 . In this specification, the terms base station, RAN node, gNB and ng-eNB may be used interchangeably. The gNB  115  may provide NR user plane and control plane protocol terminations towards the UE  125 . The ng-eNB  120  may provide E-UTRA user plane and control plane protocol terminations towards the UE  125 . An interface between the gNB  115  and the UE  125  or between the ng-eNB  120  and the UE  125  may be referred to as a Uu interface. The Uu interface may be established with a user plane protocol stack and a control plane protocol stack. For a Uu interface, the direction from the base station (e.g., the gNB  115  or the ng-eNB  120 ) to the UE  125  may be referred to as downlink and the direction from the UE  125  to the base station (e.g., gNB  115  or ng-eNB  120 ) may be referred to as uplink. 
     The gNBs  115  and ng-eNBs  120  may be interconnected with each other by means of an Xn interface. The Xn interface may comprise an Xn User plane (Xn-U) interface and an Xn Control plane (Xn-C) interface. The transport network layer of the Xn-U interface may be built on Internet Protocol (IP) transport and GPRS Tunneling Protocol (GTP) may be used on top of User Datagram Protocol (UDP)/IP to carry the user plane protocol data units (PDUs). Xn-U may provide non-guaranteed delivery of user plane PDUs and may support data forwarding and flow control. The transport network layer of the Xn-C interface may be built on Stream Control Transport Protocol (SCTP) on top of IP. The application layer signaling protocol may be referred to as XnAP (Xn Application Protocol). The SCTP layer may provide the guaranteed delivery of application layer messages. In the transport IP layer, point-to-point transmission may be used to deliver the signaling PDUs. The Xn-C interface may support Xn interface management, UE mobility management, including context transfer and RAN paging, and dual connectivity. 
     The gNBs  115  and ng-eNBs  120  may also be connected to the 5GC  110  by means of the NG interfaces, more specifically to an Access and Mobility Management Function (AMF)  130  of the 5GC  110  by means of the NG-C interface and to a User Plane Function (UPF)  135  of the 5GC  110  by means of the NG-U interface. The transport network layer of the NG-U interface may be built on IP transport and GTP protocol may be used on top of UDP/IP to carry the user plane PDUs between the NG-RAN node (e.g., gNB  115  or ng-eNB  120 ) and the UPF  135 . NG-U may provide non-guaranteed delivery of user plane PDUs between the NG-RAN node and the UPF. The transport network layer of the NG-C interface may be built on IP transport. For the reliable transport of signaling messages, SCTP may be added on top of IP. The application layer signaling protocol may be referred to as NGAP (NG Application Protocol). The SCTP layer may provide guaranteed delivery of application layer messages. In the transport, IP layer point-to-point transmission may be used to deliver the signaling PDUs. The NG-C interface may provide the following functions: NG interface management; UE context management; UE mobility management; transport of NAS messages; paging; PDU Session Management; configuration transfer; and warning message transmission. 
     The gNB  115  or the ng-eNB  120  may host one or more of the following functions: Radio Resource Management functions such as Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (e.g., scheduling); IP and Ethernet header compression, encryption and integrity protection of data; Selection of an AMF at UE attachment when no routing to an AMF can be determined from the information provided by the UE; Routing of User Plane data towards UPF(s); Routing of Control Plane information towards AMF; Connection setup and release; Scheduling and transmission of paging messages; Scheduling and transmission of system broadcast information (e.g., originated from the AMF); Measurement and measurement reporting configuration for mobility and scheduling; Transport level packet marking in the uplink; Session Management; Support of Network Slicing; QoS Flow management and mapping to data radio bearers; Support of UEs in RRC Inactive state; Distribution function for NAS messages; Radio access network sharing; Dual Connectivity; Tight interworking between NR and E-UTRA; and Maintaining security and radio configuration for User Plane 5G system (5GS) Cellular IoT (CIoT) Optimization. 
     The AMF  130  may host one or more of the following functions: NAS signaling termination; NAS signaling security; AS Security control; Inter CN node signaling for mobility between 3GPP access networks; Idle mode UE Reachability (including control and execution of paging retransmission); Registration Area management; Support of intra-system and inter-system mobility; Access Authentication; Access Authorization including check of roaming rights; Mobility management control (subscription and policies); Support of Network Slicing; Session Management Function (SMF) selection; Selection of 5GS CIoT optimizations. 
     The UPF  135  may host one or more of the following functions: Anchor point for Intra-/Inter-RAT mobility (when applicable); External PDU session point of interconnect to Data Network; Packet routing &amp; forwarding; Packet inspection and User plane part of Policy rule enforcement; Traffic usage reporting; Uplink classifier to support routing traffic flows to a data network; Branching point to support multi-homed PDU session; QoS handling for user plane, e.g. packet filtering, gating, UL/DL rate enforcement; Uplink Traffic verification (Service Data Flow (SDF) to QoS flow mapping); Downlink packet buffering and downlink data notification triggering. 
     As shown in  FIG.  1   , the NG-RAN  105  may support the PC5 interface between two UEs  125  (e.g., UE  125 A and UE 125 B). In the PC5 interface, the direction of communications between two UEs (e.g., from UE  125 A to UE  125 B or vice versa) may be referred to as sidelink. Sidelink transmission and reception over the PC5 interface may be supported when the UE  125  is inside NG-RAN  105  coverage, irrespective of which RRC state the UE is in, and when the UE  125  is outside NG-RAN  105  coverage. Support of V2X services via the PC5 interface may be provided by NR sidelink communication and/or V2X sidelink communication. 
     PC5-S signaling may be used for unicast link establishment with Direct Communication Request/Accept message. A UE may self-assign its source Layer-2 ID for the PC5 unicast link for example based on the V2X service type. During unicast link establishment procedure, the UE may send its source Layer-2 ID for the PC5 unicast link to the peer UE, e.g., the UE for which a destination ID has been received from the upper layers. A pair of source Layer-2 ID and destination Layer-2 ID may uniquely identify a unicast link. The receiving UE may verify that the said destination ID belongs to it and may accept the Unicast link establishment request from the source UE. During the PC5 unicast link establishment procedure, a PC5-RRC procedure on the Access Stratum may be invoked for the purpose of UE sidelink context establishment as well as for AS layer configurations, capability exchange etc. PC5-RRC signaling may enable exchanging UE capabilities and AS layer configurations such as Sidelink Radio Bearer configurations between pair of UEs for which a PC5 unicast link is established. 
     NR sidelink communication may support one of three types of transmission modes (e.g., Unicast transmission, Groupcast transmission, and Broadcast transmission) for a pair of a Source Layer-2 ID and a Destination Layer-2 ID in the AS. The Unicast transmission mode may be characterized by: Support of one PC5-RRC connection between peer UEs for the pair; Transmission and reception of control information and user traffic between peer UEs in sidelink; Support of sidelink HARQ feedback; Support of sidelink transmit power control; Support of RLC Acknowledged Mode (AM); and Detection of radio link failure for the PC5-RRC connection. The Groupcast transmission may be characterized by: Transmission and reception of user traffic among UEs belonging to a group in sidelink; and Support of sidelink HARQ feedback. The Broadcast transmission may be characterized by: Transmission and reception of user traffic among UEs in sidelink. 
     A Source Layer-2 ID, a Destination Layer-2 ID and a PC5 Link Identifier may be used for NR sidelink communication. The Source Layer-2 ID may be a link-layer identity that identifies a device or a group of devices that are recipients of sidelink communication frames. The Destination Layer-2 ID may be a link-layer identity that identifies a device that originates sidelink communication frames. In some examples, the Source Layer-2 ID and the Destination Layer-2 ID may be assigned by a management function in the Core Network. The Source Layer-2 ID may identify the sender of the data in NR sidelink communication. The Source Layer-2 ID may be 24 bits long and may be split in the MAC layer into two bit strings: One bit string may be the LSB part (8 bits) of Source Layer-2 ID and forwarded to physical layer of the sender. This may identify the source of the intended data in sidelink control information and may be used for filtering of packets at the physical layer of the receiver; and the Second bit string may be the MSB part (16 bits) of the Source Layer-2 ID and may be carried within the Medium Access Control (MAC) header. This may be used for filtering of packets at the MAC layer of the receiver. The Destination Layer-2 ID may identify the target of the data in NR sidelink communication. For NR sidelink communication, the Destination Layer-2 ID may be 24 bits long and may be split in the MAC layer into two bit strings: One bit string may be the LSB part (16 bits) of Destination Layer-2 ID and forwarded to physical layer of the sender. This may identify the target of the intended data in sidelink control information and may be used for filtering of packets at the physical layer of the receiver; and the Second bit string may be the MSB part (8 bits) of the Destination Layer-2 ID and may be carried within the MAC header. This may be used for filtering of packets at the MAC layer of the receiver. The PC5 Link Identifier may uniquely identify the PC5 unicast link in a UE for the lifetime of the PC5 unicast link. The PC5 Link Identifier may be used to indicate the PC5 unicast link whose sidelink Radio Link failure (RLF) declaration was made and PC5-RRC connection was released. 
       FIG.  2 A  and  FIG.  2 B  show examples of radio protocol stacks for user plane and control plane, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure. As shown in  FIG.  2 A , the protocol stack for the user plane of the Uu interface (between the UE  125  and the gNB  115 ) includes Service Data Adaptation Protocol (SDAP)  201  and SDAP  211 , Packet Data Convergence Protocol (PDCP)  202  and PDCP  212 , Radio Link Control (RLC)  203  and RLC  213 , MAC  204  and MAC  214  sublayers of layer 2 and Physical (PHY)  205  and PHY  215  layer (layer 1 also referred to as L1). 
     The PHY  205  and PHY  215  offer transport channels  244  to the MAC  204  and MAC  214  sublayer. The MAC  204  and MAC  214  sublayer offer logical channels  243  to the RLC  203  and RLC  213  sublayer. The RLC  203  and RLC  213  sublayer offer RLC channels  242  to the PDCP  202  and PCP  212  sublayer. The PDCP  202  and PDCP  212  sublayer offer radio bearers  241  to the SDAP  201  and SDAP  211  sublayer. Radio bearers may be categorized into two groups: Data Radio Bearers (DRBs) for user plane data and Signaling Radio Bearers (SRBs) for control plane data. The SDAP  201  and SDAP  211  sublayer offers QoS flows  240  to 5GC. 
     The main services and functions of the MAC  204  or MAC  214  sublayer include: mapping between logical channels and transport channels; Multiplexing/demultiplexing of MAC Service Data Units (SDUs) belonging to one or different logical channels into/from Transport Blocks (TB) delivered to/from the physical layer on transport channels; Scheduling information reporting; Error correction through Hybrid Automatic Repeat Request (HARQ) (one HARQ entity per cell in case of carrier aggregation (CA)); Priority handling between UEs by means of dynamic scheduling; Priority handling between logical channels of one UE by means of Logical Channel Prioritization (LCP); Priority handling between overlapping resources of one UE; and Padding. A single MAC entity may support multiple numerologies, transmission timings and cells. Mapping restrictions in logical channel prioritization control which numerology(ies), cell(s), and transmission timing(s) a logical channel may use. 
     The HARQ functionality may ensure delivery between peer entities at Layer 1. A single HARQ process may support one TB when the physical layer is not configured for downlink/uplink spatial multiplexing, and when the physical layer is configured for downlink/uplink spatial multiplexing, a single HARQ process may support one or multiple TBs. 
     The RLC  203  or RLC  213  sublayer may support three transmission modes: Transparent Mode (TM); Unacknowledged Mode (UM); and Acknowledged Mode (AM). The RLC configuration may be per logical channel with no dependency on numerologies and/or transmission durations, and Automatic Repeat Request (ARQ) may operate on any of the numerologies and/or transmission durations the logical channel is configured with. 
     The main services and functions of the RLC  203  or RLC  213  sublayer depend on the transmission mode (e.g., TM, UM or AM) and may include: Transfer of upper layer PDUs; Sequence numbering independent of the one in PDCP (UM and AM); Error Correction through ARQ (AM only); Segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs; Reassembly of SDU (AM and UM); Duplicate Detection (AM only); RLC SDU discard (AM and UM); RLC re-establishment; and Protocol error detection (AM only). 
     The automatic repeat request within the RLC  203  or RLC  213  sublayer may have the following characteristics: ARQ retransmits RLC SDUs or RLC SDU segments based on RLC status reports; Polling for RLC status report may be used when needed by RLC; RLC receiver may also trigger RLC status report after detecting a missing RLC SDU or RLC SDU segment. 
     The main services and functions of the PDCP  202  or PDCP  212  sublayer may include: Transfer of data (user plane or control plane); Maintenance of PDCP Sequence Numbers (SNs); Header compression and decompression using the Robust Header Compression (ROHC) protocol; Header compression and decompression using EHC protocol; Ciphering and deciphering; Integrity protection and integrity verification; Timer based SDU discard; Routing for split bearers; Duplication; Reordering and in-order delivery; Out-of-order delivery; and Duplicate discarding. 
     The main services and functions of SDAP  201  or SDAP  211  include: Mapping between a QoS flow and a data radio bearer; and Marking QoS Flow ID (QFI) in both downlink and uplink packets. A single protocol entity of SDAP may be configured for each individual PDU session. 
     As shown in  FIG.  2 B , the protocol stack of the control plane of the 
     Uu interface (between the UE  125  and the gNB  115 ) includes PHY layer (layer 1), and MAC, RLC and PDCP sublayers of layer 2 as described above and in addition, the RRC  206  sublayer and RRC  216  sublayer. The main services and functions of the RRC  206  sublayer and the RRC  216  sublayer over the Uu interface include: Broadcast of System Information related to AS and NAS; Paging initiated by 5GC or NG-RAN; Establishment, maintenance and release of an RRC connection between the UE and NG-RAN (including Addition, modification and release of carrier aggregation; and Addition, modification and release of Dual Connectivity in NR or between E-UTRA and NR); Security functions including key management; Establishment, configuration, maintenance and release of SRBs and DRBs; Mobility functions (including Handover and context transfer; UE cell selection and reselection and control of cell selection and reselection; and Inter-RAT mobility); QoS management functions; UE measurement reporting and control of the reporting; Detection of and recovery from radio link failure; and NAS message transfer to/from NAS from/to UE. The NAS  207  and NAS  227  layer is a control protocol (terminated in AMF on the network side) that performs the functions such as authentication, mobility management, security control, etc. 
     The sidelink specific services and functions of the RRC sublayer over the Uu interface include: Configuration of sidelink resource allocation via system information or dedicated signaling; Reporting of UE sidelink information; Measurement configuration and reporting related to sidelink; and Reporting of UE assistance information for SL traffic pattern(s). 
       FIG.  3 A ,  FIG.  3 B  and  FIG.  3 C  show example mappings between logical channels and transport channels in downlink, uplink and sidelink, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure. Different kinds of data transfer services may be offered by MAC. Each logical channel type may be defined by what type of information is transferred. Logical channels may be classified into two groups: Control Channels and Traffic Channels. Control channels may be used for the transfer of control plane information only. The Broadcast Control Channel (BCCH) is a downlink channel for broadcasting system control information. The Paging Control Channel (PCCH) is a downlink channel that carries paging messages. The Common Control Channel (CCCH) is channel for transmitting control information between UEs and network. This channel may be used for UEs having no RRC connection with the network. The Dedicated Control Channel (DCCH) is a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network and may be used by UEs having an RRC connection. Traffic channels may be used for the transfer of user plane information only. The Dedicated Traffic Channel (DTCH) is a point-to-point channel, dedicated to one UE, for the transfer of user information. A DTCH may exist in both uplink and downlink. Sidelink Control Channel (SCCH) is a sidelink channel for transmitting control information (e.g., PC5-RRC and PC5-S messages) from one UE to other UE(s). Sidelink Traffic Channel (STCH) is a sidelink channel for transmitting user information from one UE to other UE(s). Sidelink Broadcast Control Channel (SBCCH) is a sidelink channel for broadcasting sidelink system information from one UE to other UE(s). 
     The downlink transport channel types include Broadcast Channel (BCH), Downlink Shared Channel (DL-SCH), and Paging Channel (PCH). The BCH may be characterized by: fixed, pre-defined transport format; and requirement to be broadcast in the entire coverage area of the cell, either as a single message or by beamforming different BCH instances. The DL-SCH may be characterized by: support for HARQ; support for dynamic link adaptation by varying the modulation, coding and transmit power; possibility to be broadcast in the entire cell; possibility to use beamforming; support for both dynamic and semi-static resource allocation; and the support for UE Discontinuous Reception (DRX) to enable UE power saving. The DL-SCH may be characterized by: support for HARQ; support for dynamic link adaptation by varying the modulation, coding and transmit power; possibility to be broadcast in the entire cell; possibility to use beamforming; support for both dynamic and semi-static resource allocation; support for UE discontinuous reception (DRX) to enable UE power saving. The PCH may be characterized by: support for UE discontinuous reception (DRX) to enable UE power saving (DRX cycle is indicated by the network to the UE); requirement to be broadcast in the entire coverage area of the cell, either as a single message or by beamforming different BCH instances; mapped to physical resources which can be used dynamically also for traffic/other control channels. 
     In downlink, the following connections between logical channels and transport channels may exist: BCCH may be mapped to BCH; BCCH may be mapped to DL-SCH; PCCH may be mapped to PCH; CCCH may be mapped to DL-SCH; DCCH may be mapped to DL-SCH; and DTCH may be mapped to DL-SCH. 
     The uplink transport channel types include Uplink Shared Channel (UL-SCH) and Random Access Channel(s) (RACH). The UL-SCH may be characterized by possibility to use beamforming; support for dynamic link adaptation by varying the transmit power and potentially modulation and coding; support for HARQ; support for both dynamic and semi-static resource allocation. The RACH may be characterized by limited control information; and collision risk. 
     In Uplink, the following connections between logical channels and transport channels may exist: CCCH may be mapped to UL-SCH; DCCH may be mapped to UL-SCH; and DTCH may be mapped to UL-SCH. 
     The sidelink transport channel types include: Sidelink broadcast channel (SL-BCH) and Sidelink shared channel (SL-SCH). The SL-BCH may be characterized by pre-defined transport format. The SL-SCH may be characterized by support for unicast transmission, groupcast transmission and broadcast transmission; support for both UE autonomous resource selection and scheduled resource allocation by NG-RAN; support for both dynamic and semi-static resource allocation when UE is allocated resources by the NG-RAN; support for HARQ; and support for dynamic link adaptation by varying the transmit power, modulation and coding. 
     In the sidelink, the following connections between logical channels and transport channels may exist: SCCH may be mapped to SL-SCH; STCH may be mapped to SL-SCH; and SBCCH may be mapped to SL-BCH. 
       FIG.  4 A ,  FIG.  4 B  and  FIG.  4 C  show example mappings between transport channels and physical channels in downlink, uplink and sidelink, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure. The physical channels in downlink include Physical Downlink Shared Channel (PDSCH), Physical Downlink Control Channel (PDCCH) and Physical Broadcast Channel (PBCH). The PCH and DL-SCH transport channels are mapped to the PDSCH. The BCH transport channel is mapped to the PBCH. A transport channel is not mapped to the PDCCH but Downlink Control Information (DCI) is transmitted via the PDCCH. 
     The physical channels in the uplink include Physical Uplink Shared Channel (PUSCH), Physical Uplink Control Channel (PUCCH) and Physical Random Access Channel (PRACH). The UL-SCH transport channel may be mapped to the PUSCH and the RACH transport channel may be mapped to the PRACH. A transport channel is not mapped to the PUCCH but Uplink Control Information (UCI) is transmitted via the PUCCH. 
     The physical channels in the sidelink include Physical Sidelink Shared Channel (PSSCH), Physical Sidelink Control Channel (PSCCH), Physical Sidelink Feedback Channel (PSFCH) and Physical Sidelink Broadcast Channel (PSBCH). The Physical Sidelink Control Channel (PSCCH) may indicate resource and other transmission parameters used by a UE for PSSCH. The Physical Sidelink Shared Channel (PSSCH) may transmit the TBs of data themselves, and control information for HARQ procedures and CSI feedback triggers, etc. At least 6 OFDM symbols within a slot may be used for PSSCH transmission. Physical Sidelink Feedback Channel (PSFCH) may carry the HARQ feedback over the sidelink from a UE which is an intended recipient of a PSSCH transmission to the UE which performed the transmission. PSFCH sequence may be transmitted in one PRB repeated over two OFDM symbols near the end of the sidelink resource in a slot. The SL-SCH transport channel may be mapped to the PSSCH. The SL-BCH may be mapped to PSBCH. No transport channel is mapped to the PSFCH but Sidelink Feedback Control Information (SFCI) may be mapped to the PSFCH. No transport channel is mapped to PSCCH but Sidelink Control Information (SCI) may mapped to the PSCCH. 
       FIG.  5 A ,  FIG.  5 B ,  FIG.  5 C  and  FIG.  5 D  show examples of radio protocol stacks for NR sidelink communication according to some aspects of some of various exemplary embodiments of the present disclosure. The AS protocol stack for user plane in the PC5 interface (i.e., for STCH) may consist of SDAP, PDCP, RLC and MAC sublayers, and the physical layer. The protocol stack of user plane is shown in  FIG.  5 A . The AS protocol stack for SBCCH in the PC5 interface may consist of RRC, RLC, MAC sublayers, and the physical layer as shown below in  FIG.  5 B . For support of PC5-S protocol, PC5-S is located on top of PDCP, RLC and MAC sublayers, and the physical layer in the control plane protocol stack for SCCH for PC5-S, as shown in  FIG.  5 C . The AS protocol stack for the control plane for SCCH for RRC in the PC5 interface consists of RRC, PDCP, RLC and MAC sublayers, and the physical layer. The protocol stack of control plane for SCCH for RRC is shown in  FIG.  5 D . 
     The Sidelink Radio Bearers (SLRBs) may be categorized into two groups: Sidelink Data Radio Bearers (SL DRB) for user plane data and Sidelink Signaling Radio Bearers (SL SRB) for control plane data. Separate SL SRBs using different SCCHs may be configured for PC5-RRC and PC5-S signaling, respectively. 
     The MAC sublayer may provide the following services and functions over the PC5 interface: Radio resource selection; Packet filtering; Priority handling between uplink and sidelink transmissions for a given UE; and Sidelink CSI reporting. With logical channel prioritization restrictions in MAC, only sidelink logical channels belonging to the same destination may be multiplexed into a MAC PDU for every unicast, groupcast and broadcast transmission which may be associated to the destination. For packet filtering, a SL-SCH MAC header including portions of both Source Layer-2 ID and a Destination Layer-2 ID may be added to a MAC PDU. The Logical Channel Identifier (LCID) included within a MAC subheader may uniquely identify a logical channel within the scope of the Source Layer-2 ID and Destination Layer-2 ID combination. 
     The services and functions of the RLC sublayer may be supported for sidelink. Both RLC Unacknowledged Mode (UM) and Acknowledged Mode (AM) may be used in unicast transmission while only UM may be used in groupcast or broadcast transmission. For UM, only unidirectional transmission may be supported for groupcast and broadcast. 
     The services and functions of the PDCP sublayer for the Uu interface may be supported for sidelink with some restrictions: Out-of-order delivery may be supported only for unicast transmission; and Duplication may not be supported over the PC5 interface. 
     The SDAP sublayer may provide the following service and function over the PC5 interface: Mapping between a QoS flow and a sidelink data radio bearer. There may be one SDAP entity per destination for one of unicast, groupcast and broadcast which is associated to the destination. 
     The RRC sublayer may provide the following services and functions over the PC5 interface: Transfer of a PC5-RRC message between peer UEs; Maintenance and release of a PC5-RRC connection between two UEs; and Detection of sidelink radio link failure for a PC5-RRC connection based on indication from MAC or RLC. A PC5-RRC connection may be a logical connection between two UEs for a pair of Source and Destination Layer-2 IDs which may be considered to be established after a corresponding PC5 unicast link is established. There may be one-to-one correspondence between the PC5-RRC connection and the PC5 unicast link. A UE may have multiple PC5-RRC connections with one or more UEs for different pairs of Source and Destination Layer-2 IDs. Separate PC5-RRC procedures and messages may be used for a UE to transfer UE capability and sidelink configuration including SL-DRB configuration to the peer UE. Both peer UEs may exchange their own UE capability and sidelink configuration using separate bi-directional procedures in both sidelink directions. 
       FIG.  6    shows example physical signals in downlink, uplink and sidelink according to some aspects of some of various exemplary embodiments of the present disclosure. The Demodulation Reference Signal (DM-RS) may be used in downlink, uplink and sidelink and may be used for channel estimation. DM-RS is a UE-specific reference signal and may be transmitted together with a physical channel in downlink, uplink or sidelink and may be used for channel estimation and coherent detection of the physical channel. The Phase Tracking Reference Signal (PT-RS) may be used in downlink, uplink and sidelink and may be used for tracking the phase and mitigating the performance loss due to phase noise. The PT-RS may be used mainly to estimate and minimize the effect of Common Phase Error (CPE) on system performance. Due to the phase noise properties, PT-RS signal may have a low density in the frequency domain and a high density in the time domain. PT-RS may occur in combination with DM-RS and when the network has configured PT-RS to be present. The Positioning Reference Signal (PRS) may be used in downlink for positioning using different positioning techniques. PRS may be used to measure the delays of the downlink transmissions by correlating the received signal from the base station with a local replica in the receiver. The Channel State Information Reference Signal (CSI-RS) may be used in downlink and sidelink. CSI-RS may be used for channel state estimation, Reference Signal Received Power (RSRP) measurement for mobility and beam management, time/frequency tracking for demodulation among other uses. CSI-RS may be configured UE-specifically but multiple users may share the same CSI-RS resource. The UE may determine CSI reports and transit them in the uplink to the base station using PUCCH or PUSCH. The CSI report may be carried in a sidelink MAC CE. The Primary Synchronization Signal (PSS) and the Secondary Synchronization Signal (SSS) may be used for radio fame synchronization. The PSS and SSS may be used for the cell search procedure during the initial attach or for mobility purposes. The Sounding Reference Signal (SRS) may be used in uplink for uplink channel estimation. Similar to CSI-RS, the SRS may serve as QCL reference for other physical channels such that they can be configured and transmitted quasi-collocated with SRS. The Sidelink PSS (S-PSS) and Sidelink SSS (S-SSS) may be used in sidelink for sidelink synchronization. 
       FIG.  7    shows examples of Radio Resource Control (RRC) states and transitioning between different RRC states according to some aspects of some of various exemplary embodiments of the present disclosure. A UE may be in one of three RRC states: RRC Connected State  710 , RRC Idle State  720  and RRC Inactive state  730 . After power up, the UE may be in RRC Idle state  720  and the UE may establish connection with the network using initial access and via an RRC connection establishment procedure to perform data transfer and/or to make/receive voice calls. Once RRC connection is established, the UE may be in RRC Connected State  710 . The UE may transition from the RRC Idle state  720  to the RRC connected state  710  or from the RRC Connected State  710  to the RRC Idle state  720  using the RRC connection Establishment/Release procedures  740 . 
     To reduce the signaling load and the latency resulting from frequent transitioning from the RRC Connected State  710  to the RRC Idle State  720  when the UE transmits frequent small data, the RRC Inactive State  730  may be used. In the RRC Inactive State  730 , the AS context may be stored by both UE and gNB. This may result in faster state transition from the RRC Inactive State  730  to RRC Connected State  710 . The UE may transition from the RRC Inactive State  730  to the RRC Connected State  710  or from the RRC Connected State  710  to the RRC Inactive State  730  using the RRC Connection Resume/Inactivation procedures  760 . The UE may transition from the RRC Inactive State  730  to RRC Idle State  720  using an RRC Connection Release procedure  750 . 
       FIG.  8    shows example frame structure and physical resources according to some aspects of some of various exemplary embodiments of the present disclosure. The downlink or uplink or sidelink transmissions may be organized into frames with 10 ms duration, consisting of ten 1 ms subframes. Each subframe may consist of 1, 2, 4, . . . slots, wherein the number of slots per subframe may depend on the subcarrier spacing of the carrier on which the transmission takes place. The slot duration may be 14 symbols with Normal Cyclic Prefix (CP) and 12 symbols with Extended CP and may scale in time as a function of the used sub-carrier spacing so that there is an integer number of slots in a subframe.  FIG.  8    shows a resource grid in time and frequency domain. Each element of the resource grid, comprising one symbol in time and one subcarrier in frequency, is referred to as a Resource Element (RE). A Resource Block (RB) may be defined as 12 consecutive subcarriers in the frequency domain. 
     In some examples and with non-slot-based scheduling, the transmission of a packet may occur over a portion of a slot, for example during 2, 4 or 7 OFDM symbols which may also be referred to as mini-slots. The mini-slots may be used for low latency applications such as URLLC and operation in unlicensed bands. In some embodiments, the mini-slots may also be used for fast flexible scheduling of services (e.g., pre-emption of URLLC over eMBB). 
       FIG.  9    shows example component carrier configurations in different carrier aggregation scenarios according to some aspects of some of various exemplary embodiments of the present disclosure. In Carrier Aggregation (CA), two or more Component Carriers (CCs) may be aggregated. A UE may simultaneously receive or transmit on one or multiple CCs depending on its capabilities. CA may be supported for both contiguous and non-contiguous CCs in the same band or on different bands as shown in  FIG.  9   . A gNB and the UE may communicate using a serving cell. A serving cell may be associated at least with one downlink CC (e.g., may be associated only with one downlink CC or may be associated with a downlink CC and an uplink CC). A serving cell may be a Primary Cell (PCell) or a Secondary cCell (SCell). 
     A UE may adjust the timing of its uplink transmissions using an uplink timing control procedure. A Timing Advance (TA) may be used to adjust the uplink frame timing relative to the downlink frame timing. The gNB may determine the desired Timing Advance setting and provides that to the UE. The UE may use the provided TA to determine its uplink transmit timing relative to the UE&#39;s observed downlink receive timing. 
     In the RRC Connected state, the gNB may be responsible for maintaining the timing advance to keep the L1 synchronized. Serving cells having uplink to which the same timing advance applies and using the same timing reference cell are grouped in a Timing Advance Group (TAG). A TAG may contain at least one serving cell with configured uplink. The mapping of a serving cell to a TAG may be configured by RRC. For the primary TAG, the UE may use the PCell as timing reference cell, except with shared spectrum channel access where an SCell may also be used as timing reference cell in certain cases. In a secondary TAG, the UE may use any of the activated SCells of this TAG as a timing reference cell and may not change it unless necessary. 
     Timing advance updates may be signaled by the gNB to the UE via MAC CE commands. Such commands may restart a TAG-specific timer which may indicate whether the L1 can be synchronized or not: when the timer is running, the L1 may be considered synchronized, otherwise, the L1 may be considered non-synchronized (in which case uplink transmission may only take place on PRACH). 
     A UE with single timing advance capability for CA may simultaneously receive and/or transmit on multiple CCs corresponding to multiple serving cells sharing the same timing advance (multiple serving cells grouped in one TAG). A UE with multiple timing advance capability for CA may simultaneously receive and/or transmit on multiple CCs corresponding to multiple serving cells with different timing advances (multiple serving cells grouped in multiple TAGs). The NG-RAN may ensure that each TAG contains at least one serving cell. A non-CA capable UE may receive on a single CC and may transmit on a single CC corresponding to one serving cell only (one serving cell in one TAG). 
     The multi-carrier nature of the physical layer in case of CA may be exposed to the MAC layer and one HARQ entity may be required per serving cell. When CA is configured, the UE may have one RRC connection with the network. At RRC connection establishment/re-establishment/handover, one serving cell (e.g., the PCell) may provide the NAS mobility information. Depending on UE capabilities, SCells may be configured to form together with the PCell a set of serving cells. The configured set of serving cells for a UE may consist of one PCell and one or more SCells. The reconfiguration, addition and removal of SCells may be performed by RRC. 
     In a dual connectivity scenario, a UE may be configured with a plurality of cells comprising a Master Cell Group (MCG) for communications with a master base station, a Secondary Cell Group (SCG) for communications with a secondary base station, and two MAC entities: one MAC entity and for the MCG for communications with the master base station and one MAC entity for the SCG for communications with the secondary base station. 
       FIG.  10    shows example bandwidth part configuration and switching according to some aspects of some of various exemplary embodiments of the present disclosure. The UE may be configured with one or more Bandwidth Parts (BWPs)  1010  on a given component carrier. In some examples, one of the one or more bandwidth parts may be active at a time. The active bandwidth part may define the UE&#39;s operating bandwidth within the cell&#39;s operating bandwidth. For initial access, and until the UE&#39;s configuration in a cell is received, initial bandwidth part  1020  determined from system information may be used. With Bandwidth Adaptation (BA), for example through BWP switching  1040 , the receive and transmit bandwidth of a UE may not be as large as the bandwidth of the cell and may be adjusted. For example, the width may be ordered to change (e.g. to shrink during period of low activity to save power); the location may move in the frequency domain (e.g. to increase scheduling flexibility); and the subcarrier spacing may be ordered to change (e.g. to allow different services). The first active BWP  1020  may be the active BWP upon RRC (re-)configuration for a PCell or activation of an SCell. 
     For a downlink BWP or uplink BWP in a set of downlink BWPs or uplink BWPs, respectively, the UE may be provided the following configuration parameters: a Subcarrier Spacing (SCS); a cyclic prefix; a common RB and a number of contiguous RBs; an index in the set of downlink BWPs or uplink BWPs by respective BWP-Id; a set of BWP-common and a set of BWP-dedicated parameters. A BWP may be associated with an OFDM numerology according to the configured subcarrier spacing and cyclic prefix for the BWP. For a serving cell, a UE may be provided by a default downlink BWP among the configured downlink BWPs. If a UE is not provided a default downlink BWP, the default downlink BWP may be the initial downlink BWP. 
     A downlink BWP may be associated with a BWP inactivity timer. If the BWP inactivity timer associated with the active downlink BWP expires and if the default downlink BWP is configured, the UE may perform BWP switching to the default BWP. If the BWP inactivity timer associated with the active downlink BWP expires and if the default downlink BWP is not configured, the UE may perform BWP switching to the initial downlink BWP. 
       FIG.  11    shows example four-step contention-based and contention-free random access processes according to some aspects of some of various exemplary embodiments of the present disclosure.  FIG.  12    shows example two-step contention-based and contention-free random access processes according to some aspects of some of various exemplary embodiments of the present disclosure. The random access procedure may be triggered by a number of events, for example: Initial access from RRC Idle State; RRC Connection Re-establishment procedure; downlink or uplink data arrival during RRC Connected State when uplink synchronization status is “non-synchronized”; uplink data arrival during RRC Connected State when there are no PUCCH resources for Scheduling Request (SR) available; SR failure; Request by RRC upon synchronous reconfiguration (e.g. handover); Transition from RRC Inactive State; to establish time alignment for a secondary TAG; Request for Other System Information (SI); Beam Failure Recovery (BFR); Consistent uplink Listen-Before-Talk (LBT) failure on PCell. 
     Two types of Random Access (RA) procedure may be supported: 4-step RA type with MSG1 and 2-step RA type with MSGA. Both types of RA procedure may support Contention-Based Random Access (CBRA) and Contention-Free Random Access (CFRA) as shown in  FIG.  11    and  FIG.  12   . 
     The UE may select the type of random access at initiation of the random access procedure based on network configuration. When CFRA resources are not configured, a RSRP threshold may be used by the UE to select between 2-step RA type and 4-step RA type. When CFRA resources for 4-step RA type are configured, UE may perform random access with 4-step RA type. When CFRA resources for 2-step RA type are configured, UE may perform random access with 2-step RA type. 
     The MSG 1  of the 4-step RA type may consist of a preamble on PRACH. After MSG1 transmission, the UE may monitor for a response from the network within a configured window. For CFRA, dedicated preamble for MSG1 transmission may be assigned by the network and upon receiving Random Access Response (RAR) from the network, the UE may end the random access procedure as shown in  FIG.  11   . For CBRA, upon reception of the random access response, the UE may send MSG3 using the uplink grant scheduled in the random access response and may monitor contention resolution as shown in  FIG.  11   . If contention resolution is not successful after MSG3 (re)transmission(s), the UE may go back to MSG1 transmission. 
     The MSGA of the 2-step RA type may include a preamble on PRACH and a payload on PUSCH. After MSGA transmission, the UE may monitor for a response from the network within a configured window. For CFRA, dedicated preamble and PUSCH resource may be configured for MSGA transmission and upon receiving the network response, the UE may end the random access procedure as shown in  FIG.  12   . For CBRA, if contention resolution is successful upon receiving the network response, the UE may end the random access procedure as shown in  FIG.  12   ; while if fallback indication is received in MSGB, the UE may perform MSG3 transmission using the uplink grant scheduled in the fallback indication and may monitor contention resolution. If contention resolution is not successful after MSG3 (re)transmission(s), the UE may go back to MSGA transmission. 
       FIG.  13    shows example time and frequency structure of Synchronization Signal and Physical Broadcast Channel (PBCH) Block (SSB) according to some aspects of some of various exemplary embodiments of the present disclosure. The SS/PBCH Block (SSB) may consist of Primary and Secondary Synchronization Signals (PSS, SSS), each occupying 1 symbol and 127 subcarriers (e.g., subcarrier numbers 56 to 182 in  FIG.  13   ), and PBCH spanning across 3 OFDM symbols and 240 subcarriers, but on one symbol leaving an unused part in the middle for SSS as show in  FIG.  13   . The possible time locations of SSBs within a half-frame may be determined by sub-carrier spacing and the periodicity of the half-frames, where SSBs are transmitted, may be configured by the network. During a half-frame, different SSBs may be transmitted in different spatial directions (i.e., using different beams, spanning the coverage area of a cell). 
     The PBCH may be used to carry Master Information Block (MIB) used by a UE during cell search and initial access procedures. The UE may first decode PBCH/MIB to receive other system information. The MIB may provide the UE with parameters required to acquire System Information Block 1 (SIB1), more specifically, information required for monitoring of PDCCH for scheduling PDSCH that carries SIB1. In addition, MIB may indicate cell barred status information. The MIB and SIB1 may be collectively referred to as the minimum system information (SI) and SIB1 may be referred to as remaining minimum system information (RMSI). The other system information blocks (SIBs) (e.g., SIB2, SIB3, . . . , SIB10 and SIBpos) may be referred to as Other SI. The Other SI may be periodically broadcast on DL-SCH, broadcast on-demand on DL-SCH (e.g., upon request from UEs in RRC Idle State, RRC Inactive State, or RRC connected State), or sent in a dedicated manner on DL-SCH to UEs in RRC Connected State (e.g., upon request, if configured by the network, from UEs in RRC Connected State or when the UE has an active BWP with no common search space configured). 
       FIG.  14    shows example SSB burst transmissions according to some aspects of some of various exemplary embodiments of the present disclosure. An SSB burst may include N SSBs and each SSB of the N SSBs may correspond to a beam. The SSB bursts may be transmitted according to a periodicity (e.g., SSB burst period). During a contention-based random access process, a UE may perform a random access resource selection process, wherein the UE first selects an SSB before selecting a RA preamble. The UE may select an SSB with an RSRP above a configured threshold value. In some embodiments, the UE may select any SSB if no SSB with RSRP above the configured threshold is available. A set of random access preambles may be associated with an SSB. After selecting an SSB, the UE may select a random access preamble from the set of random access preambles associated with the SSB and may transmit the selected random access preamble to start the random access process. 
     In some embodiments, a beam of the N beams may be associated with a CSI-RS resource. A UE may measure CSI-RS resources and may select a CSI-RS with RSRP above a configured threshold value. The UE may select a random access preamble corresponding to the selected CSI-RS and may transmit the selected random access process to start the random access process. If there is no random access preamble associated with the selected CSI-RS, the UE may select a random access preamble corresponding to an SSB which is Quasi-Collocated with the selected CSI-RS. 
     In some embodiments, based on the UE measurements of the CSI-RS resources and the UE CSI reporting, the base station may determine a Transmission Configuration Indication (TCI) state and may indicate the TCI state to the UE, wherein the UE may use the indicated TCI state for reception of downlink control information (e.g., via PDCCH) or data (e.g., via PDSCH). The UE may use the indicated TCI state for using the appropriate beam for reception of data or control information. The indication of the TCI states may be using RRC configuration or in combination of RRC signaling and dynamic signaling (e.g., via a MAC Control element (MAC CE) and/or based on a value of field in the downlink control information that schedules the downlink transmission). The TCI state may indicate a Quasi-Colocation (QCL) relationship between a downlink reference signal such as CSI-RS and the DM-RS associated with the downlink control or data channels (e.g., PDCCH or PDSCH, respectively). 
     In some embodiments, the UE may be configured with a list of up to M TCI-State configurations, using Physical Downlink Shared Channel (PDSCH) configuration parameters, to decode PDSCH according to a detected PDCCH with DCI intended for the UE and the given serving cell, where M may depends on the UE capability. Each TCI-State may contain parameters for configuring a QCL relationship between one or two downlink reference signals and the DM-RS ports of the PDSCH, the DM-RS port of PDCCH or the CSI-RS port(s) of a CSI-RS resource. The quasi co-location relationship may be configured by one or more RRC parameters. The quasi co-location types corresponding to each DL RS may take one of the following values: ‘QCL-TypeA’: {Doppler shift, Doppler spread, average delay, delay spread}; ‘QCL-TypeB’: {Doppler shift, Doppler spread}; ‘QCL-TypeC’: {Doppler shift, average delay}; ‘QCL-TypeD’: {Spatial Rx parameter}. The UE may receive an activation command (e.g., a MAC CE), used to map TCI states to the codepoints of a DCI field. 
       FIG.  15    shows example components of a user equipment and a base station for transmission and/or reception according to some aspects of some of various exemplary embodiments of the present disclosure. All or a subset of blocks and functions in  FIG.  15    may be in the base station  1505  and the user equipment  1500  and may be performed by the user equipment  1500  and by the base station  1505 . The Antenna  1510  may be used for transmission or reception of electromagnetic signals. The Antenna  1510  may comprise one or more antenna elements and may enable different input-output antenna configurations including Multiple-Input Multiple Output (MIMO) configuration, Multiple-Input Single-Output (MISO) configuration and Single-Input Multiple-Output (SIMO) configuration. In some embodiments, the Antenna  150  may enable a massive MIMO configuration with tens or hundreds of antenna elements. The Antenna  1510  may enable other multi-antenna techniques such as beamforming. In some examples and depending on the UE  1500  capabilities or the type of UE  1500  (e.g., a low-complexity UE), the UE  1500  may support a single antenna only. 
     The transceiver  1520  may communicate bi-directionally, via the Antenna  1510 , wireless links as described herein. For example, the transceiver  1520  may represent a wireless transceiver at the UE and may communicate bi-directionally with the wireless transceiver at the base station or vice versa. The transceiver  1520  may include a modem to modulate the packets and provide the modulated packets to the Antennas  1510  for transmission, and to demodulate packets received from the Antennas  1510 . 
     The memory  1530  may include RAM and ROM. The memory  1530  may store computer-readable, computer-executable code  1535  including instructions that, when executed, cause the processor to perform various functions described herein. In some examples, the memory  1530  may contain, among other things, a Basic Input/output System (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices. 
     The processor  1540  may include a hardware device with processing capability (e.g., a general purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some examples, the processor  1540  may be configured to operate a memory using a memory controller. In other examples, a memory controller may be integrated into the processor  1540 . The processor  1540  may be configured to execute computer-readable instructions stored in a memory (e.g., the memory  1530 ) to cause the UE  1500  or the base station  1505  to perform various functions. 
     The Central Processing Unit (CPU)  1550  may perform basic arithmetic, logic, controlling, and Input/output (I/O) operations specified by the computer instructions in the Memory  1530 . The user equipment  1500  and/or the base station  1505  may include additional peripheral components such as a graphics processing unit (GPU)  1560  and a Global Positioning System (GPS)  1570 . The GPU  1560  is a specialized circuitry for rapid manipulation and altering of the Memory  1530  for accelerating the processing performance of the user equipment  1500  and/or the base station  1505 . The GPS  1570  may be used for enabling location-based services or other services for example based on geographical position of the user equipment  1500 . 
     Example embodiments may enable quality of experience (QoE) measurement collection for different services including streaming services. Example QoE management may collect the experience parameters of streaming services as well as augmented reality/virtual reality (AR/VR) and URLLC. 
     In some example embodiments, QoE measurement may enable collecting the user KPI information, e.g., end-to-end (E2E) reliability statistic indicator, etc. 
     In some examples, different types of UEs may have different QoE requirements. In some examples, QoE parameters may be defined as UE-specific, and service related. In some examples, QoE may be used as criteria to evaluate network quality. In the past, it was normally used the metrics such as throughput, capacity and coverage for performance evaluations for network solutions. Example embodiments may enable mechanisms of trigger, configuration and reporting for QoE measurement collection, including relevant entities (e.g., UE, network entities). 
     In some examples, signaling-based and management-based mechanisms may be used for QoE related signaling. In some examples, application layer measurement configuration received from OAM or CN may be encapsulated in a transparent container, which may be forwarded to UE in a downlink RRC message. Application layer measurements received from UE&#39;s higher layer may be encapsulated in a transparent container and sent to network in an uplink RRC message. 
     In some examples, RAN may release an ongoing QoE measurements/reporting configuration, e.g., if handing over to a network that does not support this. 
     In some examples, an area may be defined and/or configured for QoE measurement and/or reporting. In some examples, for the Area Handling the network may keep track of whether the UE is inside or outside the area and may configure/release configuration accordingly. In some examples, the network may keep track of whether the UE is inside or outside the area, and the UE may manage start stop of QoE accordingly. In some examples, the UE may perform area checking (UE may have the area configuration) and to manage start stop of QoE accordingly. 
     In some examples, QoE measurements in RRC INACTIVE state may be supported, for MBS. In some examples, QoE measurements in RRC IDLE state may be supported, for MBS. 
     In some examples, management-based QoE configuration may not override signaling based QoE configuration. 
     In some examples, QoE reports may be sent via a separate SRB (separate from current SRBs) in NR, as this reporting may be lower priority than other SRB transmissions. 
     In some examples, configuration and reporting for multiple simultaneous QoE measurements for a UE may be supported. 
     In some examples, RRC signaling may be used by the gNB to indicate the UE to pause or resume the QoE reporting. 
     In some examples, the pause/resume may be for all QoE reports or may be per QoE configuration. 
     In some examples, QoE measurements may be configured in an RRCReconfiguration message. 
     In some examples, configuration of QoE measurements may be in a OtherConfig information element in an RRCReconfiguration message. 
     In some examples, the configuration of QoE measurements may be by means of a list (e.g., an RRC list parameter) to enable configuration of multiple simultaneous measurements. 
     In some examples, for RRC an ID may be used to identify a measurement. In some examples, this ID may be the QoE reference ID. 
     In some examples, SRB4 may be used for transmission of QoE reports in NR. 
     In some examples, an RRC message MeasReportAppLayer may be used for the transmission of QoE reports in NR. 
     In some examples, QoE support for NR may include: activation by Trace Function, both signaling and management-based configuration and RRC procedures supporting AppLayer config and report. 
     In some examples, the UE may follow gNB commands and, NG-RAN may release by RRC the application layer measurement configuration towards the UE at any time, e.g., if required due to load or other reasons. 
     In some examples, the UE Inactive access stratum (AS) context may include the UE AS configuration for the QoE (for examples, it may not be released when UE goes to Inactive). 
     In some examples, “QoE pause” indication from the network may be used to temporarily stop QoE reports from being sent from the UE to the network. 
     In some examples, for QoE report handling during RAN overload via “QoE report pause indication”: application layer may be responsible for storing QoE reports when the UE receives QoE pause indication. 
     In some examples, for QoE report handling during RAN overload via “QoE report pause indication”: AS layer may be responsible for storing QoE reports when the UE receives QoE pause indication. 
     In some examples, for QoE report handling during RAN overload via “QoE report pause indication”: the QoE container received from application layer may be discarded during pause. 
     In some examples, application layer measurement collection function may enable collection of application layer measurements from the UE. Example supported service types may be QoE measurement collection for services such as streaming services, etc. Both signaling based and management-based initiation cases may be used. For the signaling-based case, the Application Layer Measurement Collection may be initiated towards a specific UE from CN nodes; for the management-based case, the Application Layer Measurement Collection may be initiated from OAM targeting an area (e.g., without targeting a specific UE). 
     Application layer measurement configuration received from OAM or CN may be encapsulated in a transparent container, which may be forwarded to UE in a downlink RRC message. Application layer measurements received from UE&#39;s higher layer may be encapsulated in a transparent container and sent to network in an uplink RRC message. The network may release the application layer measurement configuration towards the UE at any time. 
     In some examples, for URLLC service, E2E delay may be critical, and operators may monitor and guarantee the delay measurement. 
     In some examples, the QoE management framework may exist in two flavors: Signaling-based QoE, and Management-based QoE. In the signaling based QoE, the QoE measurement configuration (QMC) may be delivered to the RAN node. The QMC may specify the area scope for the measurement, where the area scope may be defined via a list or cells/TAs/TAIs/PLMNs. In the Management-based QoE, the OAM may deliver the QMC to the RAN node. 
     In some examples, a threshold-based mechanism to trigger the start and stop of QoE measurement collection may be used. In some examples, a time-based event may be used for activation of QoE measurement to enable the flexibility of QoE measurement activation within a certain period of predefined time. 
     In some examples, upon receiving a “pause” indication from the network, the UE may stop QoE reporting, but may continue QoE measurements. 
     In some examples, “QoE pause” indication from the network may be used to temporarily stop QoE reports from being sent to the network, but it may not affect the QoE measurements collection at the UE. For example, the UE may continue ongoing QoE measurements and may trigger new ones at the application layer (e.g., as per QoE configurations stored at the UE). 
     In some examples, in case of overload in RAN, the base station may temporarily stop the reporting from the UE by sending an RRC message (e.g., an RRCConnectionReconfiguration message) to relevant UEs. The RRCConnectionReconfiguration message may include measConfigAppLayer set to temporarily stop application layer measurement reporting in otherConfig. In some examples, the Access stratum may send a command to the application with the temporary stop request. The application may stop the reporting and may stop recording further information when the data in the reporting container is used. Then the recorded data may be kept until it is reported or when the UE request session is ended. 
     In some examples, when the overload situation in RAN is ended the base station may restart the reporting from the UE by sending an RRC message (e.g., the RRCConnectionReconfiguration message) to relevant UEs. The RRCConnectionReconfiguration message may include measConfigAppLayer set to restart application layer measurement reporting in otherConfig. The Access stratum may send a command to the application with the restart request. The application may restart the reporting and recording if it was stopped. 
     In some examples, RAN may release an existing QoE measurement configuration when the session for which the QoE measurements are reported is completed or when the UE is handing over to a network that does not support the QoE measurement. An NG-RAN node may issue a release of QoE measurement configuration for UEs previously configured for QoE measurement reporting, provided that the session for which the QoE measurements are reported is completed. In some examples, RAN may need to release an ongoing QoE measurement configuration or QoE reporting configuration, e.g., if handing over to a network that does not support this. 
     In some examples, RAN may release existing QoE measurement configuration in case of RAN overload. In some examples, in case of RAN overload in standalone connectivity, RAN may stop new QoE measurement configurations, release existing QoE measurement configurations and pause QoE measurement reporting. In some examples, RRC signaling may be used by the gNB to indicate the UE to pause or resume the QoE reporting. In some examples, pause/resume may be for all QoE reports or pause/resume may be per QoE configuration. In some examples, the UE may store the reports (e.g., for a predetermined or configurable time period). In some examples, there may be a limit for stored reports size. 
     In some examples, RAN may be allowed to release a QoE configuration from a UE at any time including the time when the related QoE measurement session is ongoing. In some examples, when RAN orders the UE to release a QoE configuration, a UE may release the QoE configuration and may stop reporting for this QoE configuration (including any available and non-sent reports). 
     In some examples, RAN may stop new QoE measurement configurations, release existing QoE measurement configurations and pause QoE measurement reporting in the case of RAN overload. In some examples, in case the UE is configured with multiple QoE configurations, the network may pause reporting for only some of the configurations. In some examples, in order to temporarily pause QoE reporting from a UE, e.g., during RAN overload, RAN may send the QoE reporting pause command to the UE (e.g., using a MAC CE or in the DL RRC message), which may indicate QoE configurations (one or more) for which the reporting to be paused. In some examples, when the UE pauses the QoE report, the UE may continue the measurement collection. The UE may continue to generate the QoE measurement results. 
     In some examples, pause and resume commands for a QoE configuration may be forwarded by the UE to application layer. After receiving a pause indication from the UE, application layer may stop sending reports to RRC layer and may continue to do so after receiving resume indication from the UE. 
     In some examples, network controlled inter-RAT mobility may be supported. In some examples, the inter-RAT mobility may be between NR and E-UTRA, where E-UTRA may be connected to either EPC or 5GC. 
     An example of inter-RAT handover to a RAN based on NR is shown in  FIG.  16   . The purpose of this procedure may be to, under the control of the network, transfer a connection between the UE and another Radio Access Network (e.g., E-UTRAN) to NR. 
     The handover to NR procedure may apply when SRBs, possibly in combination with DRBs, may be established in another RAT. Handover from E-UTRA to NR may apply after integrity has been activated in E-UTRA. 
     In some examples, the RAN using another RAT may initiate the handover to NR procedure, in accordance with the specifications applicable for the other RAT, by sending the RRCReconfiguration message via the radio access technology from which the inter-RAT handover is performed. 
     In some examples, the network may apply the procedure as follows: to activate ciphering, possibly using NULL algorithm, if not yet activated in the other RAT; to re-establish SRBs and one or more DRBs. 
     In some examples, the UE may: apply the default L1 parameter values as specified in corresponding physical layer specifications except for the parameters for which values are provided in SIB1; may apply the default MAC Cell Group configuration; and may perform RRC reconfiguration procedure. 
     In some examples, if the UE is connected to 5GC of the source E-UTRA cell, the delta configuration for PDCP and SDAP may be used for intra-system inter-RAT handover. For other cases, source RAT configuration may not be considered when the UE applies the reconfiguration message of target RAT. 
     In some examples, for mobility from NR, the purpose of this procedure may be to move a UE in RRC_CONNECTED to a cell using other RAT, e.g., E-UTRA, UTRA-FDD. Example mobility from NR with successful operation and failure are shown in  FIG.  17 A  and  FIG.  17 B , respectively. The mobility from NR procedure may cover the following type of mobility: handover, i.e., the MobilityFromNRCommand message may include radio resources that have been allocated for the UE in the target cell. 
     In some examples, the network may initiate the mobility from NR procedure to a UE in RRC_CONNECTED, possibly in response to a MeasurementReport or an MCGFailureInformation message, by sending a MobilityFromNRCommand message. The network may apply the procedure as follows: the procedure may be initiated when AS security has been activated, and SRB2 with at least one DRB may be setup and not suspended; the procedure may not be initiated if any DAPS bearer is configured. 
     In some examples, upon successfully completing the handover, at the source side the UE may: reset MAC; stop all timers that are running except T325, T330 and T400; release ran-NotificationAreaInfo, if stored; release the AS security context including the KRRCenc key, the KRRCint key, the KUPint key and the KUPenc key, if stored; release all radio resources, including release of the RLC entity and the MAC configuration; release the associated PDCP entity and SDAP entity for all established RBs; if the targetRAT-Type is set to eutra and the nas-SecurityParamFromNR is included: or if the targetRAT-Type is set to utra-fdd: indicate the release of the RRC connection to upper layers together with the release cause ‘other’. 
     In some examples, a handover may be based on NR-E-UTRA mobility and may be intra 5GC. 
     In some examples, the Source RAT may configure Target RAT measurement and reporting. 
     In some examples, the source RAT may decide on the preparation initiation and may provide the necessary information to the target RAT in the format required by the target RAT: for handover preparation from E-UTRA to NR, the source RAT may issue a handover preparation request message to the target RAT passing a transparent RRC container with necessary information to prepare the handover at the target side. The information for the target RAT may include the current QoS flow to DRB mapping applied to the UE and RRM configuration. The RRM configuration may include beam measurement information for the listed cells if the measurements are available. 
     In some examples, radio resources may be prepared in the target RAT before the handover. 
     In some examples, the RRC reconfiguration message from the target RAT may be delivered to the source RAT via a transparent container and may be passed to the UE by the source RAT in the handover command: The inter-RAT handover command message may carry the information required to access the target cell. 
     In some examples, the in-sequence and lossless handover may be supported for the handover between gNB and ng-eNB. 
     In some examples, both Xn and NG based inter-RAT handover between NG-RAN nodes may be supported. Whether the handover is over Xn or CN may be transparent to the UE. 
     In some examples, in order to keep the SDAP and PDCP configurations for in-sequence and lossless inter-RAT handover, delta-configuration for the radio bearer configuration may be used. 
     In some examples, inter RAT measurements in NR for this use case may be limited to E-UTRA. 
     In some examples, for a UE configured with E-UTRA Inter RAT measurements, a measurement gap configuration may be provided when: the UE only supports per-UE measurement gaps; or when the UE supports per-FR measurement gaps and at least one of the NR serving cells is in FR1. 
     In some examples, a handover may be based on NR-E-UTRA mobility and may be from 5GC to EPC. 
     In some examples, the source NG-RAN node may decide between handover or redirection to EPS based on radio criteria and availability of the N26 interface. 
     In some examples, information about the availability of the N26 interface may be configured by OAM at the NG-RAN. 
     In some examples, inter RAT handover is characterized by the following: The Source RAT may configure Target RAT measurement and reporting; the source RAT may decide on the preparation initiation and may provide the necessary information to the target RAT in the format required by the target RAT; the radio resources may be prepared in the target RAT before the handover; the RRC reconfiguration message from the target RAT may be delivered to the source RAT via a transparent container, and may be passed to the UE by the source RAT in the handover command; in-sequence and lossless handovers may not supported; and security procedures for handover to E-UTRA/EPC may follow E-UTRA handover procedures. 
     In some examples, inter RAT measurements in NR for this use case may be limited to E-UTRA. 
     In some examples, for a UE configured with E-UTRA Inter RAT measurements, a measurement gap configuration may be provided when: the UE only supports per-UE measurement gaps; or when the UE supports per-FR measurement gaps and at least one of the NR serving cells is in FR1. 
     In some examples, control plane handling for inter-System data forwarding from 5GS to EPS may follow the following principles: only forwarding of downlink data may be supported, PDU session information at the serving NG-RAN node may contain mapping information per QoS Flow to a corresponding E-RAB; at handover preparation, the source NG-RAN node may decide which mapped E-RABs are proposed to be subject to data forwarding and may provide this information in the source-to-target container to the target eNB. Based on availability of direct data forwarding path the source NG-RAN node may request to apply direct data forwarding by indicating direct data forwarding path availability to the 5GC; the target eNB may assign forwarding TEID/TNL address(es) for the E-RAB(s) for which it accepts data forwarding; in case of indirect data forwarding, a single data forwarding tunnel may be established between the source NG-RAN node and UPF per PDU session for which at least data for a single QoS Flow is subject to data forwarding; in case of direct data forwarding, the source NG-RAN node may receive a TEID/TNL address for each E-RAB accepted for data forwarding as assigned by the target eNB. 
     In some examples, in case of indirect data forwarding, user plane handling for inter-System data forwarding from 5GS to EPS may follow the following key principles: for the QoS flows accepted for data forwarding, the NG-RAN node may initiate data forwarding to the UPF by the corresponding PDU session data forwarding tunnel(s); the UPF may map forwarded data received from the per PDU session data forwarding tunnel(s) to the mapped EPS bearer(s) removing the QFI. Handling of end marker packets: the source NG-RAN node may receive one or several end marker packets per PDU session from the UPF. When there are no more data packets to be forwarded for QoS flows mapped to an E-RAB, the source NG-RAN node may send one or several end markers including one QFI of those QoS flows mapped to that E-RAB and may send the end marker packets to the UPF over the PDU session tunnel. From the included QFI in the end markers and its mapping to an EPS bearer ID, the UPF may know which EPS bearer tunnel it needs to forward the end-markers to the SGW. The QFI may be removed in the end marker packets sent to the SGW. 
     In some examples, in case of direct data forwarding, user plane handling for inter-System data forwarding from 5GS to EPS may follow the following key principles: for the QoS flows accepted for data forwarding, the source NG-RAN node may map data received from the NG-U PDU session tunnel to the respective E-RAB data forwarding tunnel and may forward each user packet as PDCP SDU without PDCP SN and QFI information. The source NG-RAN node may receive one or several GTP-U end marker packets per PDU session from the UPF and may replicate the end marker packets into each E-RAB data forwarding tunnel when no more user data packets are to be forwarded over that tunnel. 
     In some examples, a handover may be based on NR-E-UTRA mobility and may be from EPC to 5GC. 
     In some examples, control plane handling for inter-System data forwarding from EPS to 5GS may follows the following principles. In some examples, only forwarding of downlink data may be supported. The target NG-RAN node may receive in the Handover Request message the mapping between E-RAB ID(s) and QoS Flow ID(s). It may decide whether to accept the data forwarding for E-RAB IDs proposed for forwarding within the Source NG-RAN Node to Target NG-RAN Node Transparent Container. Based on availability of direct data forwarding path the source eNB may request to apply direct data forwarding by indicating direct data forwarding availability to the CN. 
     In some examples, in case of data forwarding in case of indirect data forwarding: the target NG-RAN node may assign a TEID/TNL address for each PDU session for which at least one QoS flow is involved in the accepted data forwarding. The target NG-RAN node may send the Handover Request Acknowledge message in which it indicates the list of PDU sessions and QoS flows for which it has accepted the data forwarding. A single data forwarding tunnel may be established between the UPF and the target NG-RAN node per PDU session for which at least data for a single QoS Flow is subject to data forwarding. The source eNB may receive in the Handover Command message the list of E-RAB IDs for which the target NG-RAN node has accepted data forwarding of corresponding PDU sessions and QoS flows. 
     In some examples, in case of direct data forwarding: the source eNB may indicate direct path availability to the CN. The source eNB&#39;s decision may be indicated by the CN to the target NG-RAN node. The target NG-RAN node may assign a TEID/TNL address for each E-RAB it accepted for data forwarding. The source eNB may receive in the Handover Command message the list of E-RAB IDs for which the target NG-RAN node has accepted data forwarding. 
     In some examples, in case of indirect data forwarding, user plane handling for inter-System data forwarding from EPS to 5GS may follow the following key principles: for each E-RAB accepted for data forwarding, the source eNB may forward data to the SGW in the corresponding E-RAB tunnel and the SGW may forward the received data to the UPF in the E-RAB tunnel. 
     In some examples, the UPF may map the forwarded data received from an E-RAB tunnel to the corresponding mapped PDU session tunnel, adding a QFI value (by means of the PDU Session User Plane protocol). 
     In some examples, the target NG-RAN node may map a forwarded packet to the corresponding DRB based on the received QFI value. It may prioritize the forwarded packets over the fresh packets for those QoS flows. 
     In some examples, for handling of end marker packets: The 
     UPF/PGW-U may send one or several end marker packets to the SGW per EPS bearer. The SGW may forwards the received end markers per EPS bearer to the source eNB. When there are no more data packets to be forwarded for an E-RAB, the source eNB may forward the received end markers in the EPS bearer tunnel to the SGW and the SGW may forward them to the UPF. The UPF may add one QFI (by means of the PDU Session User Plane protocol) among the QoS flows mapped to that E-RAB to the end markers and may send those end markers to the target NG-RAN node in the per PDU session tunnel. When the target NG-RAN node may receive an end marker with a QFI added, the target NG-RAN node may start to transmit the data packets of all QoS flows mapped to the corresponding E-RAB received from the core network towards the UE. 
     In some examples, in case of direct data forwarding, user plane handling for inter-System data forwarding from EPS to 5GS may follow the following key principles: for each E-RAB accepted for data forwarding, the source eNB may forward data to the target NG-RAN node in the corresponding E-RAB data forwarding tunnel. Until a GTP-U end marker packet is received, the target NG-RAN node may prioritize the forwarded packets over the fresh packets for those QoS flows which are involved in the accepted data forwarding. 
     In some examples, the target NG-RAN node may remove the forwarded PDCP SNs if received in the forwarded GTP-U packets and may deliver the forwarded PDCP SDUs to the UE. 
     In some examples, in case of NR-UTRA mobility, the source NR node may decide to handover the UE with ongoing IMS voice from NR to UTRAN according the following principles: the source NR node may determine that the UE supports UTRA and may request the UE to send its UTRA radio access capabilities to the NG-RAN; the source NR node may configure target RAT measurement and reporting; the source NR node may determine based on the radio conditions and the indication that SRVCC operation is possible that handover to UTRAN should be initiated; the source NR node may initiate the handover preparation only for the ongoing IMS voice and may provide the indication to AMF that the handover is towards UTRAN together with the target UTRAN Node ID. The source NR node may provide an indication to the target UTRAN that the incoming handover originates from 5G. The source NR node may ensure that the size of the source-to-target container may not exceed the limits that can be handled by the interfaces involved in the handover; radio resources may be prepared in the target RAT before the handover; the RRC reconfiguration message from the target RAT may be delivered to the source NR node via a transparent container and may be passed to the UE by the source NR node in the handover command; in-sequence and lossless handovers may not be supported; only voice bearer may be handed over to target RAT. 
     Quality of Experience (QoE) measurement and reporting is an important functionality for various services and applications including streaming, virtual/augmented reality (VR/AR) and URLLC applications. The QoE measurement and reporting may be required when a UE is connected to radio access networks (RANs) associated with one of a plurality of radio access technologies (RATs) (e.g., NR, LTE, etc.). For continuity in QoE measurement and reporting in an inter-RAT handover process, existing handover mechanisms may lead to disruption in QoE measurement/reporting. There is a need to enhance the exiting inter-RAT handover processes to enable continuity in QoE measurement/reporting when the RAT associated with a serving gNB changes during the handover. Example embodiments enhance the exiting inter-RAT handover processes to enable continuity in QoE measurement/reporting when the RAT associated with a serving gNB changes during the handover. 
     In example embodiment, a UE may communicate with a first RAN (e.g., a first gNB in the first RAN). The first RAN may be associated with a first radio access technology (RAT). In some examples, the first RAT may be new radio (NR). In some examples, the first RAT may be long term evolution (LTE). The UE may receive one or more messages (e.g., one or more RRC messages), from the first gNB, comprising configuration parameters. The configuration parameters may comprise first configuration parameters of one or more cells comprising a first cell. The configuration parameters may comprise measurement configuration parameters used for measurements (e.g., RRM measurement) for example to be used in a handover process. The measurement configuration parameters may be used in intra-RAT handover (e.g., handover between RANs that are associated with the same type of RAT) and/or inter-RAT handover (e.g., handover between RANs that are associated with the different types of RATs). The UE may perform RRM measurements based on the measurement configuration parameters and may transmit the RRM measurement reports to the first gNB. The configuration parameters may further comprise first QoE configuration parameters. The UE may perform QoE measurements based on the first QoE configuration parameters. The QoE measurements may comprise first QoE measurements and second QoE measurements. The UE may create first QoE measurement reports based on the first QoE measurements and may transmit the one or more first QoE measurement reports to the first gNB. The transmission of the one or more first QoE measurement reports may be based on the first QoE configuration parameters. The UE may transmit the one or more first QoE measurement reports to the first gNB wherein the one or more first QoE measurement reports may be based on a first format. The first format, used in transmission of the first QoE measurement reports, may be based on the first RAT. In some examples, the first format, used in transmission of the one or more first QoE measurement reports, may be based on the first QoE configuration parameters. 
     The UE may create RRM measurement information and may transmit, to the first gNB, the RRM measurement information based on the RRM measurement configuration parameters. The RRM measurement information may comprise inter-RAT measurement information (e.g., measurement information associated with cells provided by base stations of a different RAT). Based on the RRM measurement information, the first gNB may determine to handover the UE from the first cell of the first gNB to a second cell of a second gNB, wherein the second gNB may be of a different RAT from the first gNB, e.g., the second gNB may be of a second RAT. The first gNB may transmit a handover request message to the second gNB. The second gNB may transmit a handover acknowledge message to the first gNB. The UE may receive a handover command from the first gNB. The UE may receive the handover command in response to the reception, by the first gNB, of the handover acknowledge message from the second gNB. In some examples, the handover command (e.g., an RRC reconfiguration message of the handover command) may comprise second QoE configuration parameters. In some examples, the handover command (e.g., an RRC reconfiguration message of the handover command) may comprise configuration parameters of the second cell comprising the second QoE configuration parameters. 
     In an example embodiment as shown in  FIG.  18   , in response to reception of the handover command (e.g., in response to completion of a random access process to the second cell of the second gNB as part of the handover process) the UE may transmit one or more second QoE measurement reports to the second gNB based on a second format. The UE may create the one or more second QoE measurement reports and may transmit the one or more second QoE measurement reports to the second gNB. The transmission of the one or more second QoE measurement reports may be based on second QoE configuration parameters (e.g., associated with the second cell, e.g., indicated by the handover command). The UE may transmit the one or more second QoE measurement reports to the second gNB wherein the one or more second QoE measurement reports based on a second format. The second format, used in transmission of the one or more second QoE measurement reports, may be based on the second RAT. In some examples, the second format, used in transmission of the one or more second QoE measurement reports, may be based on the second QoE configuration parameters. 
     In some examples, the first format, used in transmission of the one or more first QoE measurement reports, may be based on values of one or more first metrics. The second format, used in transmission of the one or more second QoE measurement reports, may be based on values of one or more second metrics. In some examples, the one or more first metrics may be based on the first gNB being associated with the first format and the one or more second metrics may be based on the second gNB being associated with the second format. In some examples, the second format may be based on the second QoE configuration parameters indicated by/included in the handover command. 
     In some examples, a quality of experience (QoE) measurement report may be created for transmission via one or more radio resource control (RRC) messages. In some examples, the quality of experience (QoE) measurement report may be associated with a QoE-related signaling radio bearer (SRB). In some examples, the QoE-related signaling radio bearer (SRB) may be SRB 4 . In some examples, the quality of experience (QoE)-related signaling radio bearer (SRB) may have a priority that is lower than a second SRB associated with an uplink common control channel logical channel. In some examples, the one or more resource control (RRC) messages may comprise a measurement report application layer information element (MeasReportappLayer IE) comprising the QoE measurement report. In some examples, the quality of experience (QoE) measurement report may comprise an identifier associated with a QoE configuration. In some examples, the UE may store one or more quality of experience (QoE) measurement reports while in the radio resource control (RRC) idle sate or the RRC inactive state. 
     In an example embodiment as shown in  FIG.  19   , in response to reception of the handover command, the UE may discard the second measurements (e.g., the second measurement results collected prior to receiving the handover command). In some examples, the UE may discard the second measurements in response to the handover being an inter-RAT handover. 
     In some examples, a quality of experience (QoE) measurement report may be created for transmission via one or more radio resource control (RRC) messages. In some examples, the quality of experience (QoE) measurement report may be associated with a QoE-related signaling radio bearer (SRB). In some examples, the QoE-related signaling radio bearer (SRB) may be SRB 4 . In some examples, the quality of experience (QoE)-related signaling radio bearer (SRB) may have a priority that is lower than a second SRB associated with an uplink common control channel logical channel. In some examples, the one or more resource control (RRC) messages may comprise a measurement report application layer information element (MeasReportappLayer IE) comprising the QoE measurement report. In some examples, the quality of experience (QoE) measurement report may comprise an identifier associated with a QoE configuration. In some examples, the UE may store one or more quality of experience (QoE) measurement reports while in the radio resource control (RRC) idle sate or the RRC inactive state. 
     In an example embodiment, a user equipment (UE) may receive, from a first base station (BS) of a first radio access technology (RAT), first quality of experience (QoE) configuration parameters. The UE may perform, based on the first QoE configuration parameters. first QoE measurements and second QoE measurements. The UE may transmit, to the first BS, one or more first QoE reports based on the first QoE measurements and based on a first format. The UE may receive a command, from the first BS, indicating handover from the first BS to a second BS of a second RAT. The UE may transmit, to the second BS, one or more second QoE reports based on the second QoE measurements and based on a second format. 
     In some examples, the first format may be based on one or more first quality of experience (QoE) metrics. The second format may be based on one or more second QoE metrics. 
     In some examples, the handover command may comprise second quality of experience (QoE) configuration parameters. The second format may be based on the second QoE configuration parameters. In some examples, the handover command may indicate handover from a first cell of the first base station (BS) to a second cell of the second BS. The handover command may comprise configuration parameters, of the second cell, comprising the second quality of experience (QoE) configuration parameters. 
     In some examples, the handover command may indicate handover from a first cell of the first base station (BS) to a second cell of the second BS. 
     In some examples, the first format may be based on the first quality of experience (QoE) configuration parameters. 
     In some examples, the first radio access technology (RAT) may be new radio (NR). 
     In some examples, the first radio access technology (RAT) may be long term evolution (LTE). 
     In some examples, the second radio access technology (RAT) may be new radio (NR). 
     In some examples, the second radio access technology (RAT) may be long term evolution (LTE). 
     In some examples, a handover request message may be transmitted from the first base station (BS) to the second BS. In some examples, a handover acknowledge message may be transmitted from the second base station (BS) to the first BS. In some examples, the receiving the command may be based on the first base station (BS) receiving the handover acknowledge message from the second BS. 
     In some examples, the UE may receive cell measurement configuration parameters of a plurality of cells comprising the second cell. In some examples, the cell measurement configuration parameters may comprise reference signal configuration parameters and measurement reporting configuration parameters. In some examples, the UE may perform, based on the cell configuration parameters, radio resource management (RRM) measurements for the plurality of cells. The UE may transmit the RRM measurement reports to the first base station. In some examples, a handover request message may be transmitted by the first base station (BS) to the second BS based on the radio resource management (RRM) measurement reports. 
     In some examples, a quality of experience (QoE) measurement report may be created for transmission via one or more radio resource control (RRC) messages. In some examples, the quality of experience (QoE) measurement report may be associated with a QoE-related signaling radio bearer (SRB). In some examples, the QoE-related signaling radio bearer (SRB) may be SRB4. In some examples, the quality of experience (QoE)-related signaling radio bearer (SRB) may have a priority that is lower than a second SRB associated with an uplink common control channel logical channel. In some examples, the one or more resource control (RRC) messages may comprise a measurement report application layer information element (MeasReportappLayer IE) comprising the QoE measurement report. In some examples, the quality of experience (QoE) measurement report may comprise an identifier associated with the QoE configuration. 
     In an example embodiment, a user equipment (UE) may receive, from a first base station (BS) of a first RAT, QoE configuration parameters. The UE may perform first QoE measurements and second QoE measurements, based on the QoE configuration parameters. The UE may transmit, to the first BS, one or more first QoE reports based on the first QoE measurements. The UE may receive a command, from the first BS, indicating handover from the first BS to a second BS of a second RAT. The UE may discard the second measurements in response to the handover. 
     In some examples, the discarding the second measurements may be based on the handover being a multi-radio access technology (RAT) handover. 
     In some examples, the handover command may indicate handover from a first cell of the first base station (BS) to a second cell of the second BS. 
     In some examples, the first radio access technology (RAT) may be new radio (NR). 
     In some examples, the first radio access technology (RAT) may be long term evolution (LTE). 
     In some examples, the second radio access technology (RAT) may be new radio (NR). 
     In some examples, the second radio access technology (RAT) may be long term evolution (LTE). 
     In some examples, a handover request message may be transmitted from the first base station (BS) to the second BS. In some examples, a handover acknowledge message may be transmitted from the second base station (BS) to the first BS. In some examples, the receiving the command may be based on the first base station (BS) receiving the handover acknowledge message from the second BS. 
     In some examples, the UE may receive cell measurement configuration parameters of a plurality of cells comprising the second cell. In some examples, the cell measurement configuration parameters may comprise reference signal configuration parameters and measurement reporting configuration parameters. In some examples, the UE may perform, based on the cell configuration parameters, radio resource management (RRM) measurements for the plurality of cells. The UE may transmit the RRM measurement reports to the first base station. In some examples, a handover request message may be transmitted by the first base station (BS) to the second BS based on the radio resource management (RRM) measurement reports. 
     In some examples, a quality of experience (QoE) measurement report may be created for transmission via one or more radio resource control (RRC) messages. In some examples, the quality of experience (QoE) measurement report may be associated with a QoE-related signaling radio bearer (SRB). In some examples, the QoE-related signaling radio bearer (SRB) may be SRB4. In some examples, the quality of experience (QoE)-related signaling radio bearer (SRB) may have a priority that is lower than a second SRB associated with an uplink common control channel logical channel. In some examples, the one or more resource control (RRC) messages may comprise a measurement report application layer information element (MeasReportappLayer IE) comprising the QoE measurement report. In some examples, the quality of experience (QoE) measurement report may comprise an identifier associated with the QoE configuration. 
     The exemplary blocks and modules described in this disclosure with respect to the various example embodiments may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. Examples of the general-purpose processor include but are not limited to a microprocessor, any conventional processor, a controller, a microcontroller, or a state machine. In some examples, a processor may be implemented using a combination of devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). 
     The functions described in this disclosure may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. Instructions or code may be stored or transmitted on a computer-readable medium for implementation of the functions. Other examples for implementation of the functions disclosed herein are also within the scope of this disclosure. Implementation of the functions may be via physically co-located or distributed elements (e.g., at various positions), including being distributed such that portions of functions are implemented at different physical locations. 
     Computer-readable media includes but is not limited to non-transitory computer storage media. A non-transitory storage medium may be accessed by a general purpose or special purpose computer. Examples of non-transitory storage media include, but are not limited to, random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, etc. A non-transitory medium may be used to carry or store desired program code means (e.g., instructions and/or data structures) and may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. In some examples, the software/program code may be transmitted from a remote source (e.g., a website, a server, etc.) using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave. In such examples, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are within the scope of the definition of medium. Combinations of the above examples are also within the scope of computer-readable media. 
     As used in this disclosure, use of the term “or” in a list of items indicates an inclusive list. The list of items may be prefaced by a phrase such as “at least one of” or “one or more of”. For example, a list of at least one of A, B, or C includes A or B or C or AB (i.e., A and B) or AC or BC or ABC (i.e., A and B and C). Also, as used in this disclosure, prefacing a list of conditions with the phrase “based on” shall not be construed as “based only on” the set of conditions and rather shall be construed as “based at least in part on” the set of conditions. For example, an outcome described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of this disclosure. 
     In this specification the terms “comprise”, “include” or “contain” may be used interchangeably and have the same meaning and are to be construed as inclusive and open-ending. The terms “comprise”, “include” or “contain” may be used before a list of elements and indicate that at least all of the listed elements within the list exist but other elements that are not in the list may also be present. For example, if A comprises B and C, both {B, C} and {B, C, D} are within the scope of A. 
     The present disclosure, in connection with the accompanied drawings, describes example configurations that are not representative of all the examples that may be implemented or all configurations that are within the scope of this disclosure. The term “exemplary” should not be construed as “preferred” or “advantageous compared to other examples” but rather “an illustration, an instance or an example.” By reading this disclosure, including the description of the embodiments and the drawings, it will be appreciated by a person of ordinary skills in the art that the technology disclosed herein may be implemented using alternative embodiments. The person of ordinary skill in the art would appreciate that the embodiments, or certain features of the embodiments described herein, may be combined to arrive at yet other embodiments for practicing the technology described in the present disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.