Patent Publication Number: US-2023156635-A1

Title: Dynamic timing adjustment for new radio integrated access and backhaul node

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a Continuation of U.S. Non-Provisional application Ser. No. 16/538,403, filed on Aug. 12, 2019, entitled “Dynamic Timing Adjustment For New Radio Integrated Access And Backhaul Node” which claims priority to U.S. Provisional Application No. 62/719,385, filed on Aug. 17, 2018, entitled “Dynamic Timing Adjustment For New Radio Integrated Access And Backhaul Node,” the contents of both of which are incorporated by reference in their entireties. 
    
    
     BACKGROUND 
     The present disclosure relates to wireless communication systems, and more particularly, dynamically adjusting timing for new radio integrated access and backhaul (IAB) node in wireless communication systems. 
     Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single-carrier frequency division multiple access (SC-FDMA) systems. 
     However, mobile networks are facing soaring demands for mobile data as consumers increasingly utilize mobile devices to share and consume high-definition multi-media. In addition, as the capabilities of mobile devices continue to grow with advancements such as higher-resolution cameras, 4K video, always-connected cloud computing, and virtual/augmented reality, so does the ever-increasing demand for faster and improved connectivity. Enhancing mobile broadband services is one of the driving forces behind a fifth generation (5G) wireless communications technology (which may be referred to as new radio (NR)) that is envisaged to expand and support diverse usage scenarios and applications with respect to current mobile network generations. 
     One aspect of the 5G NR communications technology includes the use of high-frequency spectrum bands above 24 GHz, which may be referred to as millimeter wave (mmW), that is emerging as a 5G technology. The use of these bands is compelling as the large bandwidths available at these high frequencies enable extremely high data rates and significant increases in capacity. There may be some limitations in the usage of mmW bands, such as lack of robustness for mobile broadband applications due to increased propagation loss and susceptibility to blockage (e.g., hand, head, body, foliage, buildings or other structures). As such, compared to lower frequency communication systems, distance between base stations in a mmW communication system may be very short (e.g., 150-200 meters), which may require deployment of a large number of base stations in close proximity. Such base stations having relatively smaller coverage areas, as compared to the coverage area of typical cellular base stations (e.g., having higher transmit power and/or utilizing lower frequency transmissions), may be referred to as small cell base stations or small cells. 
     Due to the high density deployment of small cells needed to support 5G technology, equipping each such mmW small cell with a wireline backhaul link may not be practical. As such, network operators have considered using wireless backhaul as a more cost-effective alternative solution for high-density deployment scenarios. However, utilization of wireless backhaul communication introduces additional implementation challenges. 
     Thus, as the demand for mobile broadband access continues to increase, further improvements in NR communications technology and beyond may be desired. 
     SUMMARY 
     Aspects of the present disclosure provide techniques for dynamically adjusting the access link timing alignment at the IAB node. Specifically, features of the present disclosure provide techniques for signaling to one or more child nodes the timing advance and timing offset values associated with each operational mode of the IAB node that may impact the access link timing for the child node (for uplink and/or downlink transmissions). Additionally or alternatively, aspects of the present disclosure identify whether a gap period may be included in order to ensure that the child node has sufficient time to transition between states during the transition period (e.g., from downlink to uplink) when the IAB node dynamically adjusts the access link timing. 
     In one example, a method for wireless communication includes determining, at an integrated access and backhaul node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing. The method may further include identifying a timing offset value from a base reference time that is associated with the second operational mode. The method may further include transmitting a dynamic timing indication to a child node that identifies the timing offset value. 
     In another example, an apparatus may include a memory having instructions and a processor configured to execute the instructions to perform the steps of determining, at an integrated access and backhaul node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, identifying a timing offset value from a base reference time that is associated with the second operational mode, and transmitting a dynamic timing indication to a child node that identifies the timing offset value. 
     In some aspects, a non-transitory computer readable medium includes instructions stored therein that, when executed by a processor, cause the processor to perform the steps of determining, at an integrated access and backhaul node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, identifying a timing offset value from a base reference time that is associated with the second operational mode, and transmitting a dynamic timing indication to a child node that identifies the timing offset value. 
     In certain aspects, an apparatus includes means for determining, at an integrated access and backhaul node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, means for identifying a timing offset value from a base reference time that is associated with the second operational mode, and means for transmitting a dynamic timing indication to a child node that identifies the timing offset value. 
     To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosed aspects will hereinafter be described in conjunction with the appended drawings, provided to illustrate and not to limit the disclosed aspects, wherein like designations denote like elements, and in which: 
         FIG.  1    is a schematic diagram of an example of a wireless communications system in accordance with aspects of the present disclosure; 
         FIG.  2    is an example of a spectrum diagram that illustrates aspects of the frequency range in which some of the communications described herein are performed in accordance with aspects of the present disclosure; 
         FIG.  3    is an example of a schematic diagram of beamforming in accordance with aspects of the present disclosure; 
         FIGS.  4 A and  4 B  are a schematic diagram of an example wireless communication system for coordinating between one or more IAB nodes and parent and child nodes in accordance with aspects of the present disclosure; 
         FIG.  5 A  is an example of a timing diagram of the first operational mode of the IAB node in accordance with aspects of the present disclosure; 
         FIG.  5 B  is an example of a timing diagram of the second operational mode of the IAB node in accordance with aspects of the present disclosure; 
         FIG.  5 C  is an example of a timing diagram of the third operational mode of the IAB node in accordance with aspects of the present disclosure; 
         FIG.  6    is an example of a configurable table that includes a set number of different timing offset values that may be configured by the IAB node in accordance with aspects of the present disclosure; 
         FIG.  7    is an example of a timing diagram of inclusion of guard periods by an IAB node for the child node, when the IAB node elects to dynamically switch its operational modes that affect the timing alignment of the child node; 
         FIG.  8    is a schematic diagram of an example implementation of various components of an IAB node in accordance with various aspects of the present disclosure; 
         FIG.  9    is a flow diagram of an example of a method of wireless communication implemented by the IAB node in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts. 
     Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. 
     By way of example, an element, or any portion of an element, or any combination of elements may be implemented as a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on a chip (SoC), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout the disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 
     Accordingly, in one or more example embodiments, the functions described may be implemented in hardware, software, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium, such as a computer storage media. Storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such computer-readable media may comprise a random-access memory (RAM), a read-only memory (ROM), an electrically erasable programmable ROM (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that may be used to store computer executable code in the form of instructions or data structures that may be accessed by a computer. 
     It should be noted that the techniques described herein may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and other systems. The terms “system” and “network” are often used interchangeably. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and A are commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), IEEE 902.11 (Wi-Fi), IEEE 902.16 (WiMAX), IEEE 902.20, Flash-OFDM™, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies, including cellular (e.g., LTE) communications over a shared radio frequency spectrum band. The description below, however, describes an LTE/LTE-A and/or 5G New Radio (NR) system for purposes of example, and LTE or 5G NR terminology is used in much of the description below, although the techniques are applicable beyond LTE/LTE-A and 5G NR applications, e.g., to other next generation communication systems). 
     As discussed above, one aspect of the 5G NR communications technology includes the use of high-frequency spectrum bands above 24 GHz, which may be referred to as mmW. The use of these bands enable extremely high data rates and significant increases in data processing capacity. However, compared to LTE, mmW bands are susceptible to rapid channel variations and suffer from severe free-space path loss and atmospheric absorption. In addition, mmW bands are highly vulnerable to blockage (e.g. hand, head, body, foliage, building penetration). Particularly, at mmW frequencies, even small variations in the environment, such as the turn of the head, movement of the hand, or a passing car, may change the channel conditions between the base station (BS) and the user equipment (UE), and thus impact communication performance. 
     Current mmW 5G NR systems leverage the small wavelengths of mmW at the higher frequencies to make use of multiple input multiple output (MIMO) antenna arrays to create highly directional beams that focus transmitted radio frequency (RF) energy in order to attempt to overcome the propagation and path loss challenges in both the uplink and downlink links. The isotropic path loss and the propagation characteristics of the mmWave environment, however, demands a dense next generation node base station (gNBs) (i.e., base stations in NR technology) deployment to guarantee line-of-sight links at any given time and to decrease the outage probability. In such deployments, equipping each such gNBs with a wired backhaul link (e.g., fiber) may not be feasible due to the high expense involved. As such, network operators have considered using wireless backhaul as a more cost-effective alternative solution for high-density deployment scenarios. However, utilization of wireless backhaul communication introduces additional implementation challenges, including interference management. 
     Facilitating wireless backhaul communication may include utilizing IAB nodes (which may include “relay nodes”) that may have both a base station (gNB)-type and user equipment (UE)-type functionalities. The IAB nodes provide the wireless communications system flexibility such that only a fraction of gNBs may be equipped with a traditional wired backhaul capabilities (e.g., using cable or optical fiber), while the rest of the gNBs (or IAB nodes) may have direct or indirect (e.g., via relay nodes) wireless connections to the wired backhaul, e.g., possibly through multiple hops via one or more relay nodes. According to the 3GPP agreements, NR cellular networks with IAB functionalities may be characterized by (i) the possibility of using the mmWave spectrum; (ii) the integration of the access and backhaul technologies (i.e., using the same spectral resources and infrastructures to serve both mobile terminals in access as well as the NR gNBs in backhaul); and, (iii) the possibility of deploying plug-and-play IAB nodes capable of self-configuring and self-optimizing themselves. 
     To this end, the IAB nodes may include the gNB-type functionality that allows for transmission and reception of signals to and from child nodes (e.g., UE or another IAB node) through an access link. Additionally, the IAB nodes may also include the UE-type functionality that allows for transmission and reception of signals to and from parent node (e.g., gNB or another IAB node) through backhaul links. By utilizing an IAB nodes, a common architecture, waveforms, and procedures may be shared for access links and backhaul links, thereby reducing the system complexity. For example, the IAB nodes may share the same wireless resources (e.g., via TDM or FDM) between the access links and backhaul links. 
     In some examples, IAB nodes may allow concurrent transmission or reception for higher resource efficiency. Concurrent transmission or reception may refer to transmission and/or reception that may occur for at least a portion of overlapping time, but not necessarily mean identical periods of time. For example, in concurrent transmission, the IAB node may concurrently transmit to both the parent node and the child node. In concurrent reception, both the parent node and the child node may transmit concurrently to the IAB nodes. However, concurrent transmissions may incur interference at the receiving end. For example, concurrent Tx from IAB node to a parent node and a child node may result in interference that is experienced at both the parent and child nodes. Similarly, concurrent Rx from the parent and child nodes to the IAB node may result in interference at the IAB node. 
     In some aspects, the IAB node may dynamically adjust the access link timing based on a selected operational mode (e.g., for facilitating non-current Tx/Rx, concurrent Tx, or concurrent Rx). Current systems fail to address the dynamic timing adaptation that is provided by features of the present disclosure. Specifically, in some examples, the IAB node may be configured to operate in one or more operational modes based on the type of scheduled communication at the IAB, and thus adjusts the access link timing to adjust for the selected mode. For example, in a first operational mode (e.g., “baseline mode”), the IAB node may align access link timing (slot boundaries) based on the network reference time that may be known or shared by all nodes in the wireless communication system. The first operational mode may be used for non-concurrent Tx/Rx scenarios, where the transmission or reception for backhaul and access link may be configured by time division multiplexing (TDM). Additionally, in a second operational mode, the IAB node may align the access link timing with the backhaul uplink Tx timing. The second operational mode may be used for concurrent Tx scenarios for the IAB node in order to maximize the benefit of interference coordination. Further, in a third operational mode, the IAB node may align access link timing with backhaul downlink Rx timing. The third operational mode may be used for concurrent Rx scenarios. 
     Thus, in accordance with aspects of the present disclosure, the IAB node may dynamically adjust the timing for access link (e.g., symbol or slot granularity) based on the IAB node operational mode. Features of the present disclosure provide techniques for signaling to one or more child nodes the decision by the IAB node of mode selection (e.g., when the IAB node may change the operational mode), in addition to the timing advance value associated with each operational mode. Specifically, a scheduling entity (e.g., IAB node) may indicate the Tx timing to the scheduled entity (e.g., child node) through timing-advance (TA) command in media access control (MAC) control element (MAC-CE). In turn, starting with an open loop timing estimate, the scheduled entity (e.g., child node) may advance or retard its Tx timing based on the timing-advance command (close-loop time control). Ideally, the timing advance value at the child node may be represented by Equation 1 below: 
         T   TA =2· T   p_ACC   Equation 1
 
     In the above example, the T TA  may be a timing advance value, while T p_ACC  may be time associated with the access propagation delay (e.g., time for data to travel from the IAB node to the child node and back). However, due to the capabilities of the IAB node to dynamically adjust the timing for access link in accordance with aspects of the present disclosure, the IAB node may further provide a timing offset value (T offset ) that may affect the T TA  value. Specifically, in some examples, upon dynamically adjusting the timing, the IAB node may notify the child node of the updated timing advance based on the value calculated by Equation 2: 
         T   TA   =T   TA_Base   +T   offset   Equation 2
 
     In Equation 2, the T TA_Base  may be baseline timing (e.g., MAC-CE based timing) maintained by a TA scheme and the T offset  may be either a negative, positive, or zero offset value based off of the T TA_Base  based on the timing adjustments performed by the IAB node. In some examples, a set number of different T offset  values may be configured (e.g., by radio resource control (RRC) signaling) for the child node where different values may correspond to different IAB operational modes (e.g., first operational mode, second operational mode, or third operational mode). Although the examples here are illustrated with three operational modes, it should be appreciated that any number greater or less than three operational modes may be configured for the IAB node. 
     For the configured table that includes the set number of different T offset  values, a specific value may be indicated to the child node with a scheduling grant (e.g., physical downlink control channel (PDCCH)) for downlink (e.g., physical downlink shared channel (PDSCH)) or uplink (e.g., physical uplink shared channel (PUSCH)) with a field for the dynamic timing indication. In other cases, a slot-by-slot sequence or pattern of T offset  values may be assigned to the child nodes, and the child node may change the timing according to the sequence. Thus, the sequence/pattern may be configured (e.g., by RRC signaling) and triggered by MAC-CE or downlink control information (DCI). 
     Various aspects are now described in more detail with reference to the  FIGS.  1 - 9   . In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects. It may be evident, however, that such aspect(s) may be practiced without these specific details. Additionally, the term “component” as used herein may be one of the parts that make up a system, may be hardware, firmware, and/or software stored on a computer-readable medium, and may be divided into other components. 
     The following description provides examples, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in other examples. 
       FIG.  1    is a diagram illustrating an example of a wireless communications system and an access network  100  for access link timing management at an IAB node  150 . The wireless communications system  100  may include one or more base stations  102 , one or more UEs  104 , and a core network, such as an Evolved Packet Core (EPC)  180  and/or a 5G core (5GC)  190 . The one or more base stations  102  and/or UEs  104  may operate according to millimeter wave (mmW or mmWave) technology. For example, mmW technology includes transmissions in mmW frequencies and/or near mmW frequencies. Specifically, extremely high frequency (EHF) is part of the radio frequency (RF) in the electromagnetic spectrum where the EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in this band may be referred to as a millimeter wave. Near mmW may extend down to a frequency of 3 GHz with a wavelength of 100 millimeters. For example, the super high frequency (SHF) band extends between 3 GHz and 30 GHz, and may also be referred to as centimeter wave. 
     As noted above, communications using the mmW and/or near mmW radio frequency band have extremely high path loss and a short range. Thus, the propagation characteristics of the mmWave environment demands deployment of dense gNBs  102  (i.e., base stations  102  in NR technology) to guarantee line-of-sight links at any given time and decrease the probability of outage. However, providing each such gNBs  102  with a wired backhaul link  132  may not be economically feasible. Thus, an alternative wireless backhaul  164  has been considered that utilizes IAB nodes  150  for facilitating 5G communications. 
     In some examples, the IAB nodes  150  may include both gNB-type functionality and the UE-type functionality. The IAB nodes  150  afford the wireless communications system  100  flexibility such that only a fraction of gNBs (e.g., base stations  102 - a ,  102 - b ) may be equipped with a traditional fiber-like wired  132  backhaul capabilities, while the rest of the gNBs (e.g., IAB nodes  150 ) may act as relays that are connected to the fiber infrastructures wirelessly  164 , possibly through multiple hops. In some examples, the one or more IAB nodes  150  may include a timing management component  850  (see  FIG.  8   ) for dynamically adjusting the access link timing at the IAB node  150  based on the operational modes of the IAB node  150  and signaling the timing advance value, including timing offset values to the one or more child nodes to synchronize communication between the IAB node  150  and the one or more child nodes. 
     The EPC  180  and/or the 5GC  190  may provide user authentication, access authorization, tracking, internet protocol (JP) connectivity, and other access, routing, or mobility functions. The base stations  102  may perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment trace, RAN information management (RIM), paging, positioning, and delivery of warning messages. The base stations  102  may communicate with each other directly or indirectly (e.g., through the EPC  180  or the 5GC  190 ), with one another over backhaul links  132 ,  134  (e.g., Xn, X1, or X2 interfaces) which may be wired or wireless communication links. 
     The base stations  102  may wirelessly communicate with the UEs  104  via one or more base station antennas. Each of the base stations  102  may provide communication coverage for a respective geographic coverage area  110 . In some examples, base stations  102  may be referred to as a base transceiver station, a radio base station, an access point, an access node, a radio transceiver, a NodeB, eNodeB (eNB), gNB, Home NodeB, a Home eNodeB, gNodeB (gNB), a relay, a transceiver function, a basic service set (BSS), an extended service set (ESS), a transmit reception point (TRP), or some other suitable terminology. The geographic coverage area  110  for a base station  102  may be divided into sectors or cells making up only a portion of the coverage area (not shown). The wireless communication network  100  may include base stations  102  of different types (e.g., macro base stations  102  or small cell base stations  180 , described below). 
     In some examples, the wireless communication network  100  may be or include one or any combination of communication technologies, including a NR or 5G technology, a Long Term Evolution (LTE) or LTE-Advanced (LTE-A) or MuLTEfire technology, a Wi-Fi technology, a Bluetooth technology, or any other long or short range wireless communication technology. The wireless communication network  100  may be a heterogeneous technology network in which different types of base stations provide coverage for various geographical regions. For example, each base station  102  may provide communication coverage for a macro cell, a small cell, or other types of cell. The term “cell” is a 3GPP term that may be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on context. 
     A macro cell may generally cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs  104  with service subscriptions with the network provider. A small cell may include a relative lower transmit-powered base station, as compared with a macro cell, that may operate in the same or different frequency bands (e.g., licensed, unlicensed, etc.) as macro cells. Small cells may include pico cells, femto cells, and micro cells according to various examples. A pico cell, for example, may cover a small geographic area and may allow unrestricted access by UEs  104  with service subscriptions with the network provider. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access and/or unrestricted access by UEs  104  having an association with the femto cell (e.g., in the restricted access case, UEs  104  in a closed subscriber group (CSG) of the base station  102 , which may include UEs  104  for users in the home, and the like). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells (e.g., component carriers). 
     The communication networks that may accommodate some of the various disclosed examples may be packet-based networks that operate according to a layered protocol stack and data in the user plane may be based on the IP. A user plane protocol stack (e.g., packet data convergence protocol (PDCP), radio link control (RLC), MAC, etc.), may perform packet segmentation and reassembly to communicate over logical channels. For example, a MAC layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat/request (HARD) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the RRC protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE  110  and the base stations  105 . The RRC protocol layer may also be used for core network  115  support of radio bearers for the user plane data. At the physical (PHY) layer, the transport channels may be mapped to physical channels. 
     The UEs  104  may be dispersed throughout the wireless communication network  100 , and each UE  104  may be stationary or mobile. A UE  104  may also include or be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE  104  may be a cellular phone, a smart phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a smart watch, a wireless local loop (WLL) station, an entertainment device, a vehicular component, a customer premises equipment (CPE), or any device capable of communicating in wireless communication network  100 . Some non-limiting examples of UEs  104  may include a session initiation protocol (SIP) phone, a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a healthcare device, an implant, a sensor/actuator, a display, or any other similar functioning device. Additionally, a UE  104  may be Internet of Things (IoT) and/or machine-to-machine (M2M) type of device, e.g., a low power, low data rate (relative to a wireless phone, for example) type of device, that may in some aspects communicate infrequently with wireless communication network  100  or other UEs. A UE  104  may be able to communicate with various types of base stations  102  and network equipment including macro eNBs, small cell eNBs, macro gNBs, small cell gNBs, gNB, relay base stations, and the like. 
     UE  104  may be configured to establish one or more wireless communication links  120  with one or more base stations  102 . The wireless communication links  120  shown in wireless communication network  100  may carry uplink (UL) transmissions from a UE  104  to a base station  102 , or downlink (DL) transmissions, from a base station  102  to a UE  104 . Each wireless communication link  120  may include one or more carriers, where each carrier may be a signal made up of multiple sub-carriers (e.g., waveform signals of different frequencies) modulated according to the various radio technologies described above. Each modulated signal may be sent on a different sub-carrier and may carry control information (e.g., reference signals, control channels, etc.), overhead information, user data, etc. In an aspect, the wireless communication links  120  may transmit bidirectional communications using frequency division duplex (FDD) (e.g., using paired spectrum resources) or time division duplex (TDD) operation (e.g., using unpaired spectrum resources). Frame structures may be defined for FDD (e.g., frame structure type 1) and TDD (e.g., frame structure type 2). Moreover, in some aspects, the wireless communication links  120  may represent one or more broadcast channels. 
     In some aspects of the wireless communication network  100 , base stations  102  or UEs  104  may include multiple antennas for employing antenna diversity schemes to improve communication quality and reliability between base stations  102  and UEs  104 . Additionally or alternatively, base stations  102  or UEs  104  may employ multiple input multiple output (MIMO) techniques that may take advantage of multi-path environments to transmit multiple spatial layers carrying the same or different coded data. 
     Wireless communication network  100  may also support operation on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multi-carrier operation. A carrier may also be referred to as a component carrier (CC), a layer, a channel, etc. The terms “carrier,” “component carrier,” “cell,” and “channel” may be used interchangeably herein. A UE  104  may be configured with multiple downlink CCs and one or more uplink CCs for carrier aggregation. Carrier aggregation may be used with both FDD and TDD component carriers. The communication links  120  may use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The base stations  105  and/or UEs  110  may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 30, 50, 100, 200, 400, etc., MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x=number of component carriers) used for transmission in each direction. The carriers may or may not be adjacent to each other. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL). The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell). 
     Certain UEs  110  may communicate with each other using device-to-device (D2D) communication link  138 . The D2D communication link  138  may use the DL/UL WWAN spectrum. The D2D communication link  138  may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). D2D communication may be through a variety of wireless D2D communications systems, such as for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR. 
     The wireless communication network  100  may further include base stations  102  operating according to Wi-Fi technology, e.g., Wi-Fi access points, in communication with UEs  110  operating according to Wi-Fi technology, e.g., Wi-Fi stations (STAs) via communication links in an unlicensed frequency spectrum (e.g., 5 GHz). When communicating in an unlicensed frequency spectrum, the STAs and AP may perform a clear channel assessment (CCA) or listen before talk (LBT) procedure prior to communicating in order to determine whether the channel is available. 
     The small cell may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell may employ NR and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP. The small cell, employing NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. 
     In a non-limiting example, the EPC  180  may include a Mobility Management Entity (MME)  181 , other MMES  182 , a Serving Gateway  183 , a Multimedia Broadcast Multicast Service (MBMS) Gateway  184 , a Broadcast Multicast Service Center (BM-SC)  185 , and a Packet Data Network (PDN) Gateway  186 . The MME  181  may be in communication with a Home Subscriber Server (HSS)  187 . The MIME  181  is the control node that processes the signaling between the UEs  110  and the EPC  180 . Generally, the MME  181  provides bearer and connection management. All user Internet protocol (IP) packets are transferred through the Serving Gateway  183 , which itself is connected to the PDN Gateway  186 . The PDN Gateway  186  provides UE IP address allocation as well as other functions. The PDN Gateway  186  and the BM-SC  185  are connected to the IP Services  188 . The IP Services  188  may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service, and/or other IP services. The BM-SC  185  may provide functions for MBMS user service provisioning and delivery. The BM-SC  185  may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a public land mobile network (PLMN), and may be used to schedule MBMS transmissions. The MBMS Gateway  184  may be used to distribute MBMS traffic to the base stations  105  belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information. 
     The 5GC  190  may include a Access and Mobility Management Function (AMF)  192 , other AMFs  193 , a Session Management Function (SMF)  194 , and a User Plane Function (UPF)  195 . The AMF  192  may be in communication with a Unified Data Management (UDM)  196 . The AMF  192  is the control node that processes the signaling between the UEs  110  and the 5GC  190 . Generally, the AMF  192  provides QoS flow and session management. All user Internet protocol (IP) packets are transferred through the UPF  195 . The UPF  195  provides UE IP address allocation as well as other functions. The UPF  195  is connected to the IP Services  197 . The IP Services  197  may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service, and/or other IP services. 
       FIG.  2    illustrates a spectrum diagram  200  that illustrates aspects of the frequency range in which some of the communications described herein are performed in accordance with aspects of the present disclosure. Spectrum diagram  200  may include the following components: electromagnetic spectrum  205  and environment  270 . 
     In some examples, electromagnetic spectrum  205  may include the following components: ultra-violet (UV) radiation  210 , visible light  215 , infrared radiation  220 , and radio waves  225 . The mmW (or extremely high frequency (EHF)) portion  230  of the electromagnetic spectrum corresponds to electromagnetic radiation with a frequency of 30-300 GHz and a wavelength between 1 mm and 1 cm. Near MMW may extend down to a frequency of 3 GHz with a wavelength of 100 millimeters. 
     In some examples, radio waves  225  may include the following components: EHF band  230 , super high frequency (SHF) band  235 , ultra-high frequency (UHF) band  240 , very high frequency (VHF) band  245 , high frequency (HF) band  250 , medium frequency (MF) band  255 , low frequency (LF) band  260 , and very low frequency (VLF) band  265 . The EHF band  230  lies between the SHF band  235  and the far infrared band  220 . The SHF band  235  may also be referred to as the centimeter wave band. In some examples, environment  270  may include the following components: mmW radiation  275 , atmosphere  280 , precipitation  285 , obstacle  290  (such as a building), and foliage  295 . 
     In some examples, the wireless communication system  100  may be a mmW communication system. The mmW communication systems may include transmissions in mmW frequencies and/or near mmW frequencies. In mmW communication systems (e.g., access network  100 ), a line of sight (LOS) may be needed between a transmitting device (e.g., base station  102 ) and a receiving device (e.g., UE  104 ), or between two UEs  104 . Frequency is very high in mmW communication systems which means that beam widths are very small, as the beam widths are inversely proportional to the frequency of the waves or carriers transmitted by an antenna of the transmitting device. Beam widths used in mmW communications are often termed as “pencil beams.” The small wavelengths may result in many objects or materials acting as obstacles including even oxygen molecules. Therefore, LOS between the transmitter and receiver may be required unless a reflected path is strong enough to transmit data. 
     Thus, while the use of the mmW bands is compelling as the large bandwidths available at these high frequencies enable extremely high data rates and significant increases in capacity, mmW bands are highly susceptible to rapid channel variations and suffer from severe free-space path loss and atmospheric absorption. In other words, at mmW frequencies, even small variations in the environment, such as the turn of the head, movement of the hand, or a passing car may change the channel conditions between the base station and the UE, and thus impact performance. 
     As such, base stations  102  and/or UEs  104  operating according to the mmW technology may utilize beamforming (see  FIG.  3 A ) in their transmissions to compensate for the extremely high path loss and short range. Particularly, the 5G NR systems may leverage the massive MIMO antenna arrays to create highly directional beams of small wavelengths that focus transmitted RF energy in order to attempt to overcome the propagation and path loss challenges in both the uplink and downlink. In some aspects of the wireless communication network  100 , base stations  102  or UEs  104  may include multiple antennas for employing antenna diversity schemes to improve communication quality and reliability between base stations  102  and UEs  104 . Thus, the base stations  102  or UEs  104  may employ MIMO techniques that may take advantage of multi-path environments to transmit multiple spatial layers carrying the same or different coded data. 
       FIG.  3    illustrates a schematic diagram  300  that supports beamforming in accordance with aspects of the present disclosure. Specifically, beamforming is a technique for directional signal transmission and reception. Schematic diagram  300  illustrates an example of beamforming operations, and may include a base station  102 , beamforming array  310 , and UE  104 . 
     In some examples, the beamforming array  310  of the base station  102  may include one or more antennas  315  for employing MIMO techniques that may take advantage of multi-path environments to transmit multiple spatial layers carrying the same or different coded data. Beamforming at a transmitter (e.g., base station  102  or UE  104 ) may involve phase-shifting the signal produced at different antennas  315  in an array to focus a transmission in a particular direction. The phase-shifted signals may interact to produce constructive interference in certain directions and destructive interference in other directions. By focusing the signal power, a transmitter may improve communication throughput while reducing interference with neighboring transmitters. 
     Similarly, beamforming at a receiver may involve phase-shifting a signal received from different antennas  315 . When combining the phase shifted signals, the receiver may amplify a signal from certain directions and reduce the signal from other directions. In some cases, receivers and transmitters may utilize beamforming techniques independently of each other. In other cases, a transmitter and receiver may coordinate to select a beam direction. The use of beamforming may depend on factors such as the type of signal being transmitted and the channel conditions. For example, directional transmissions may not be useful when transmitting to multiple receivers, or when the location of the receiver is unknown. Thus, beamforming may be appropriate for unicast transmissions, but may not be useful for broadcast transmissions. Also, beamforming may be appropriate when transmitting in a high frequency radio band, such as in the mmW band. 
     Since the beamforming array  310  size is proportional to the signal wavelength, smaller devices (e.g., UEs) may also be capable of beamforming in high frequency bands. Also, the increased receive power may compensate for the increased path loss at these frequencies. In some examples, beamforming pattern  320  may include one or more beams  325 , which may be identified by individual beam IDs (e.g., first beam  325 - a , second beam  325 - b , third beam  325 - c , etc.). 
     Referring to  FIGS.  4 A and  4 B , schematic diagrams  400  and  450  include examples of wireless communication systems that employ mmW communication in accordance with aspects of the present disclosure. The diagram  400  illustrates one or more of base stations  102  that may include traditional wired (e.g., via cable or optical fiber) backhaul capabilities  132  in addition to one or more IAB nodes, such as IAB node  150 - a  and IAB node  150 - c , which may not have the wired backhaul capability  132  and thus utilize wireless communication  164  with base station  102  to define a wireless backhaul capability. Also, base station  102  and/or IAB nodes  150  and  150  may serve one or more UEs  104  via respective wireless communication links  154 . In this case, IAB node  150 - a  may be referred to as a relay node based on IAB node  150 - a  wirelessly connecting IAB node  150 - b  to the wired backhaul capability  132  of base station  102 . In addition, referring specifically to  FIG.  4 B , the diagram  450  includes one or more IAB nodes  150  that may provide both the UE-type functionality  405  and gNB-type functionality  410 , as is discussed here contemporaneously with discussion on  FIG.  4 A . 
     The UE-type functionality  405  of the IAB node  150  may allow for transmission and reception of signals to and from parent node  415  (e.g., gNB  102  or another IAB node  150 ) through backhaul links. Conversely, the gNB-type functionality  410  of the IAB node  150  may allow for transmission and reception of signals to and from child nodes  420  (e.g., UE  104  or another IAB node  150 ) through an access link. As noted above, the IAB functionalities of the IAB node  150  may be characterized by (i) the utilization of the mmWave spectrum; (ii) the integration of the access and backhaul technologies (i.e., using the same spectral resources and infrastructures to serve both mobile terminals in access as well as the NR gNBs in backhaul); (iii) the possibility of deploying plug-and-play TAB nodes capable of self-configuring and self-optimizing themselves. 
     In some examples, IAB nodes  150  may allow concurrent transmission or reception for higher resource efficiency. For example, in concurrent transmission (see  FIG.  4 B , “Concurrent UL and DL Tx”), the TAB node  150  may concurrently transmit to both the parent node  415  and the child node  420 . In concurrent reception (see  FIG.  4 B , “Concurrent DL and UL Rx”), both the parent node  415  and the child node  520  may transmit concurrently to the TAB nodes  150 . However, concurrent transmissions may incur interference  425  at the receiving end. For example, concurrent Tx from TAB node  150  to a parent node  415  and a child node  420  may result in interference  425  that is experienced at both the parent node  415  and child nodes  420 . Similarly, concurrent Rx from the parent node  415  and child nodes  420  to the TAB node  150  may result in interference  425  at the IAB node  150 . 
     Features of the present disclosure implement techniques for interference management for concurrent downlink and uplink Tx/Rx at an TAB node  150 . In accordance with one example, the transmit power or beam direction for downlink and uplink Tx/Rx may be dynamically adjusted to account for the experienced interference. In other examples, aspects of the present disclosure provide techniques for coordinated management of resources (e.g., reference signal resources such as DMRS) to be shared between concurrent downlink and uplink Tx/Rx in an orthogonal manner. However, in some examples, coordinating resources alone may not be sufficient to mitigate the interference. 
     Thus, in accordance with aspects of the present disclosure, the TAB node  150  may dynamically adjust the timing for an access link (e.g., on symbol or slot basis) based on the operational mode of the TAB node  150 . Features of the present disclosure provide techniques for the TAB node  150  signaling to one or more child nodes  420  the mode selection (e.g., when the TAB node  150  may change the operating mode), in addition to the timing advance value associated with each mode. Specifically, the TAB node  150  may provide a timing offset value (T offset ) that may affect the T TA  value for the child node  420  based on the adjustment of operational mode at the IAB node  150 . 
       FIG.  5 A- 5 C  are timing diagrams of three operational modes in accordance with aspects of the present disclosure whereby the IAB node  150  may align the access link timing based on the operational mode. The timing diagrams may indicate the time for the parent node  415 , the IAB node  150 , and/or the child node  420  to transmit or receive signals. Different operational modes are associated with different gap values (T GAP ) separating the Access DL Tx from the BH DL Rx. For example, in  FIG.  5 A , the parent node  415  may transmit and receive data during the same slot timing (i.e., starting at the network reference time  505 ). The IAB node  150  may transmit uplink data to the parent node  415  at a time that is T p_BH  before the network reference time  505 . The IAB node  150  may receive downlink data from the parent node  415  at a time that is T p_BH  after the network reference time  505 . 
     In some implementations, for the backhaul links shown in  FIG.  5 A , the IAB node  150  may transmit the BH UL Tx at T p_BH  before the network reference time  505 . The BH UL Tx may arrive at the parent node  415  at the network reference time  505  as BH UL Rx. The parent node  415  may transmit the BH DL Tx at the network reference time  505 . The BH DL Tx may arrive at the IAB node  150  at T p_BH  after the network reference time  505  as BH DL Rx. The duration T p_BH  may be the propagation delay between the parent node  415  and the IAB node  150 . 
     In some implementations, for the access links shown in  FIG.  5 A , the child node  420  may transmit the Access UL Tx at T p_ACC  before the network reference time  505 . The Access UL Tx may arrive at the IAB node  150  at the network reference time  505  as Access UL Rx. The IAB node  150  may transmit the Access DL Tx at the network reference time  505 . The Access DL Tx may arrive at the child node  420  at T p_ACC  after the network reference time  505  as Access DL Rx. The BH DL Tx, BH UL Rx, BH DL Rx, BH UL Tx, Access DL Tx, Access UL Rx, Access DL Rx, and Access UL Tx may last a slot duration. The duration T p_ACC  may be the propagation delay between the child node  420  and the IAB node  150 . 
     In some implementations, for the access links shown in  FIG.  5 B , the child node  420  may transmit the Access UL Tx at a time earlier than T p_ACC  before the network reference time  505 . The Access UL Tx may arrive at the IAB node  150  after T p_ACC  and before the network reference time  505  as Access UL Rx. The IAB node  150  may transmit the Access DL Tx before the network reference time  505 . The Access DL Tx may arrive at the child node  420  after T p_ACC  as Access DL Rx. 
     In certain implementations, for the access links shown in  FIG.  5 C , the child node  420  may transmit the Access UL Tx before the network reference time  505 . The Access UL Tx may arrive at the IAB node  150  after T p_ACC  and after the network reference time  505  as Access UL Rx. The IAB node  150  may transmit the Access DL Tx after the network reference time  505 . The Access DL Tx may arrive at the child node  420  after T p_ACC  as Access DL Rx. 
     For example,  FIG.  5 A  is a timing diagram  500  of the first operational mode of the IAB node  150  that may align access link timing  510  (slot boundaries) based on the network reference time  505  that may be known or shared by all nodes in the wireless communication system. The first operational mode may be used by the IAB node  150  for non-concurrent Tx/Rx scenarios, where the transmission or reception for backhaul and access link may be configured by TDM. 
       FIG.  5 B  is a timing diagram  525  of the second operational mode of the IAB node  150  to align the access link timing  510  with the backhaul uplink Tx timing  515 . The second operational mode may be used for concurrent Tx scenarios for the IAB node  150  in order to maximize interference management.  FIG.  5 C  is a timing diagram  550  of the third operational mode of the IAB node  150  to align the access link timing  510  with backhaul downlink Rx timing  520 . The third operational mode may be used for concurrent Rx scenarios. 
     Thus, in accordance with aspects of the present disclosure, the IAB node  150  may be configured to dynamically adjust the access link timing based on a selected operational mode (e.g., for facilitating non-current Tx/Rx, concurrent Tx, or concurrent Rx). Specifically, in some examples, the IAB node may be configured to operate in one or more operational modes based on the type of scheduled communication at the IAB node  150 , and thus adjust the access link timing to adjust for the selected mode. 
       FIG.  6    is a configurable table  600  that includes a set number of different T offset  values that may be configured by the IAB node  150  (e.g., by RRC signaling) for the child node where different values may correspond to different IAB operational modes (e.g., first operational mode, second operational mode, or third operational mode). For the configured table  600  that includes the set number of different T offset  values, a specific value, or the index in the table, may be indicated to the child node with a scheduling grant (e.g., PDCCH) for downlink (e.g., PDSCH) or uplink (e.g., PUSCH) with a field for the dynamic timing indication. In an non-limiting example, the IAB node  150  may transmit one or more T offset  values, as indicated by the indices, to the child node  420  to indicate the different timing adjustments to be implemented by the child node  420 . 
     For some physical signals (e.g., aperiodic CSI-RS or SRS), the triggering DCI may include the dynamic timing indication. Additionally or alternatively, for some physical channels or bandwidth part (BWP), the RRC signaling or MAC-CE may be used to assign a set of timing offset values to the child node. For control channel (e.g., PDCCH), the RRC configuration for control resource set (CORESET) may include a parameter for timing offset. In other cases, a slot-by-slot sequence or pattern of T offset  values may be assigned to the child nodes, and each child node may change the timing according to the sequence. Thus, the sequence/pattern may be configured (e.g., by RRC signaling) and triggered by MAC-CE or DCI. 
     Thus, while the MAC-CE based TA scheme may adjust the T TA_base  value, the T offset  values may be adjusted separately by the IAB node. In some examples, adjustment for the T offset  values may not be needed as frequently as the adjustment for the T TA_base  because the mobility of IAB nodes may be limited (e.g., constant propagation delay between parent and IAB nodes). As such, RRC reconfiguration or MAC-CE signaling may be used to adjust the T offset  values when the IAB node adjusts its operational mode or environment. 
     Additionally or alternatively, as illustrated in the configurable table  600 , the set of N T offset  values may be grouped into multiple subsets of at least one element (or overlapping elements) such that an offset adjustment command may include a group index that the command will be applied. 
     To this end, the child node may indicate its capabilities for dynamic timing adjustment to the IAB node such that IAB node may modify the operational mode transitions accordingly (i.e., the IAB node may determine which operational mode to utilize based on the capabilities of the child node). For example, the child node may transmit information such as maximum supported number of T offset  values of the child nodes and the range of each offset value, the radio frequency (RF)/intermediate frequency (IF) retuning latency or downlink-uplink switching latency of the child node. The capabilities may be included in the UE capability report or in the RRC signaling/MAC-CE that may be transmitted from the child node to the IAB node. In some examples, the child node may also report the estimated propagation delay from the IAB node. Thus, based on the RF/IF retuning latency and the propagation delay, the IAB node may determine the length of a guard period to include between the two time alignments when switching between different operational modes. 
       FIG.  7    is a timing diagram  700  of inclusion of guard periods by an IAB node for the child node during transitions from operational modes that affect the timing alignment of the child node. In order to minimize data loss during transition between downlink and uplink (or vice versa), the downlink-uplink (DL-UL) transition gap  710  for the access link at the IAB node  150  should ideally be larger than or equal to the round-trip propagation delay plus the RF/IF retuning latency  715  of the child node  420 , as illustrated in scenario  705 . However, if the IAB node  150  dynamically adjusts the access link timing such that the access uplink Rx occurs earlier than previously scheduled (e.g., Δ time), as in scenario  720 , the downlink-uplink transition gap—Δ  725  time may be reduced to be less than the RF/IF retuning latency  715  of the child node  420 . Such transition may generally cause loss of data because the transceiver of the child node  420  may not switch from downlink to uplink transition in sufficient time, thereby missing portion of the transmission opportunity. 
     Thus, to address this problem, features of the present disclosure provide techniques for determining a guard period  730  between two zones (e.g., downlink and uplink) that may be included in the access link timing in order to ensure that the child node  420  has sufficient time to make transition between the timings 
       FIG.  8    illustrates a hardware components and subcomponents of a device that may be IAB node  150  for implementing one or more methods (e.g., method  900 ) described herein in accordance with various aspects of the present disclosure. For example, one example of an implementation of the IAB node  150  may include a variety of components, some of which have already been described above, but including components such as one or more processors  812 , memory  816  and transceiver  802  in communication via one or more buses  844 , which may operate in conjunction with the timing management component  850  to perform functions described herein related to including one or more methods (e.g.,  900 ) of the present disclosure. 
     In some examples, the timing management component  850  may include an operational mode component  855  for dynamically adjusting the access link timing based on a selected operational mode (e.g., for facilitating non-current Tx/Rx, concurrent Tx, or concurrent Rx). Specifically, in some examples, the IAB node  150  may be configured to operate in one or more operational modes based on the type of scheduled communication at the IAB  150 , and thus adjust the access link timing to adjust for the selected mode. For example, in a first operational mode (e.g., “baseline mode”), the IAB node may align access link timing (slot boundaries) based on the network reference time that may be known or shared by all nodes in the wireless communication system. The first operational mode may be used for non-concurrent Tx/Rx scenarios, where the transmission or reception for backhaul and access link may be configured by time division multiplexing (TDM). Additionally, in a second operational mode, the IAB node may align the access link timing with the backhaul uplink Tx timing. The second operational mode may be used for concurrent Tx scenarios for the IAB node in order to maximize interference management. Further, in a third operational mode, the IAB node may align access link timing with backhaul downlink Rx timing. The third operational mode may be used for concurrent Rx scenarios. The timing management component  850  may further include a guard period component  860  for determining length of guard period that ensures that downlink-uplink transition gap at the IAB node  150  exceeds the RF/IF retuning latency of the child node  420 . 
     The one or more processors  812 , modem  814 , memory  816 , transceiver  802 , RF front end  888  and one or more antennas  865 , may be configured to support voice and/or data calls (simultaneously or non-simultaneously) in one or more radio access technologies. In an aspect, the one or more processors  812  may include a modem  814  that uses one or more modem processors. The various functions related to timing management component  850  may be included in modem  814  and/or processors  812  and, in an aspect, may be executed by a single processor, while in other aspects, different ones of the functions may be executed by a combination of two or more different processors. For example, in an aspect, the one or more processors  812  may include any one or any combination of a modem processor, or a baseband processor, or a digital signal processor, or a transmit processor, or a receiver processor, or a transceiver processor associated with transceiver  802 . In other aspects, some of the features of the one or more processors  812  and/or modem  814  associated with timing management component  850  may be performed by transceiver  802 . The one or more antennas  865  may include stand-alone antennas and/or antenna arrays. 
     The memory  816  may be configured to store data used herein and/or local versions of application(s)  875  or timing management component  850  and/or one or more of its subcomponents being executed by at least one processor  812 . The memory  816  may include any type of computer-readable medium usable by a computer or at least one processor  812 , such as random access memory (RAM), read only memory (ROM), tapes, magnetic discs, optical discs, volatile memory, non-volatile memory, and any combination thereof. In an aspect, for example, the memory  816  may be a non-transitory computer-readable storage medium that stores one or more computer-executable codes defining timing management component  850  and/or one or more of its subcomponents, and/or data associated therewith, when the IAB node  150  is operating at least one processor  812  to execute timing management component  850  and/or one or more of its subcomponents. 
     The transceiver  802  may include at least one receiver  806  and at least one transmitter  808 . The receiver  806  may include hardware, firmware, and/or software code executable by a processor for receiving data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium). The receiver  806  may be, for example, a radio frequency (RF) receiver. In an aspect, the receiver  806  may receive signals transmitted by at least one UE  104 . Additionally, receiver  806  may process such received signals, and also may obtain measurements of the signals, such as, but not limited to, Ec/Io, SNR, RSRP, RSSI, etc. The transmitter  808  may include hardware, firmware, and/or software code executable by a processor for transmitting data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium). A suitable example of the transmitter  808  may including, but is not limited to, an RF transmitter. 
     Moreover, in an aspect, transmitting device may include the RF front end  888 , which may operate in communication with one or more antennas  865  and transceiver  802  for receiving and transmitting radio transmissions, for example, wireless communications transmitted by at least one base station  102 , other IAB nodes  150  or wireless transmissions transmitted to and by UE  104 . The RF front end  888  may be connected to one or more antennas  865  and may include one or more low-noise amplifiers (LNAs)  890 , one or more switches  892 , one or more power amplifiers (PAs)  898 , and one or more filters  896  for transmitting and receiving RF signals. 
     In an aspect, the LNA  890  may amplify a received signal at a desired output level. In an aspect, each LNA  890  may have a specified minimum and maximum gain values. In an aspect, the RF front end  888  may use one or more switches  892  to select a particular LNA  890  and its specified gain value based on a desired gain value for a particular application. 
     Further, for example, one or more PA(s)  898  may be used by the RF front end  888  to amplify a signal for an RF output at a desired output power level. In an aspect, each PA  898  may have specified minimum and maximum gain values. In an aspect, the RF front end  888  may use one or more switches  892  to select a particular PA  898  and its specified gain value based on a desired gain value for a particular application. 
     Also, for example, one or more filters  896  may be used by the RF front end  888  to filter a received signal to obtain an input RF signal. Similarly, in an aspect, for example, a respective filter  896  may be used to filter an output from a respective PA  898  to produce an output signal for transmission. In an aspect, each filter  896  may be connected to a specific LNA  890  and/or PA  898 . In an aspect, the RF front end  888  may use one or more switches  892  to select a transmit or receive path using a specified filter  796 , LNA  790 , and/or PA  898 , based on a configuration as specified by the transceiver  702  and/or processor  812 . 
     As such, the transceiver  802  may be configured to transmit and receive wireless signals through one or more antennas  865  via the RF front end  888 . In an aspect, the transceiver  802  may be tuned to operate at specified frequencies such that transmitting device may communicate with, for example, one or more base stations  102  or one or more cells associated with one or more base stations  102 . In an aspect, for example, the modem  814  may configure the transceiver  802  to operate at a specified frequency and power level based on the configuration of the transmitting device and the communication protocol used by the modem  814 . 
     In an aspect, the modem  814  may be a multiband-multimode modem, which may process digital data and communicate with the transceiver  802  such that the digital data is sent and received using the transceiver  802 . In an aspect, the modem  814  may be multiband and be configured to support multiple frequency bands for a specific communications protocol. In an aspect, the modem  814  may be multimode and be configured to support multiple operating networks and communications protocols. In an aspect, the modem  814  may control one or more components of transmitting device (e.g., RF front end  888 , transceiver  802 ) to enable transmission and/or reception of signals from the network based on a specified modem configuration. In an aspect, the modem configuration may be based on the mode of the modem  814  and the frequency band in use. In another aspect, the modem configuration may be based on UE configuration information associated with transmitting device as provided by the network during cell selection and/or cell reselection. 
       FIG.  9    is a flowchart of an example method  900  for wireless communications in accordance with aspects of the present disclosure. The method  900  may be performed using the IAB node  150 . Although the method  900  is described below with respect to the elements of the IAB node  150 , other components may be used to implement one or more of the steps described herein. The IAB node  150  may include both a base station type functionality that allows for transmission and reception to and from the child node and a UE-type functionality that allows for transmission and reception to and from a parent node. 
     At block  905 , the method  900  may optionally include receiving, from the child node, dynamic timing adjustment capabilities of the child node. The one child node may be a user equipment (UE) or a second IAB node. In some examples, the dynamic timing adjustment capabilities includes at least one or more of radio frequency (RF)-intermediate frequency (IF) retuning latency, downlink-to-uplink switching latency of the child node, or an estimated propagation delay between the IAB node and the child node. Additionally or alternatively, the dynamic timing adjustment capabilities of the child node may further include one or more of maximum supported number of offset values and range of each offset value supported by the child node. Aspects of block  905  may be performed by transceiver  802  described with reference to  FIG.  8   . For example, the one or more antennas  865  of the IAB node  150  may receive electro-magnetic signals associated with the dynamic timing adjustment capabilities of the child node. The RF front end  888  of the IAB node  150  may filter, amplify, and/or extract electrical signals carried by the electro-magnetic signals. The transceiver  802  or the receiver  806  of the IAB node  150  may digitize and convert the electrical signals into data, such as the dynamic timing adjustment capabilities of the child node, and send to the modem  850  of the IAB node  150 . Thus, the modem  850 , the transceiver  802 , the transmitter  808 , the RF front end  888 , the one or more antennas  865 , the one or more processors  812 , and/or the IAB node  150  or one of its subcomponents may define the means for receiving the dynamic timing adjustment capabilities of the child node. 
     At block  910 , the method  900  may include determining, at an integrated access and backhaul (IAB) node, to transition from a first operational mode to a second operational mode. In some examples, the first operational mode may be associated with a first access link timing and the second operational mode may be associated with a second access link timing. Aspects of block  910  may be performed by timing management component  850  in collaboration with the operational mode component  855  described with reference to  FIG.  8   . Thus, the modem  850 , the one or more processors  812 , and/or the IAB node  150  or one of its subcomponents may define the means for determining, at an integrated access and backhaul (IAB) node, to transition from a first operational mode to a second operational mode. 
     At block  915 , the method  900  may include identifying a timing offset value from a base reference time that is associated with the second operational mode. Specifically, each operational mode of the IAB node (e.g., first operational mode, second operational mode, third operational mode, etc.) may have a respective timing offset value from a network reference time (E.g., T TA_Base ). For instance, the first operational mode may have a first timing offset value based off of the network reference time, and the second operational mode may have a second timing offset value based off of the network reference time. The first timing offset value and the second timing offset value may be different. The timing offset value may also include a set of different timing offset values configured for the child node, each of the different timing offset values of the set corresponds to a different IAB operational modes. In some examples, the timing offset value(s) may be adjusted by the IAB node. The adjusted timing offset value may be signaled to the child node via RRC configuration or MAC-CE signaling. Additionally or alternatively, the set of different timing offset values may be grouped into multiple subset such that an offset adjustment command from the IAB node may include a group index corresponding to one or more timing offset values in the set that are to be adjusted. Aspects of block  915  may be performed by the timing management component  855  and/or operational mode component  855  described with reference to  FIG.  8   . Thus, the modem  850 , the one or more processors  812 , and/or the IAB node  150  or one of its subcomponents may define the means for identifying a timing offset value from a base reference time that is associated with the second operational mode. 
     At block  920 , the method  900  may optionally include determining, at the IAB node, a length of guard period required for transition gap based on one or more of the RF-IF retuning latency, the downlink-to-uplink switching latency of the child node, or an estimated propagation delay between the IAB node and the child node. In some examples, the method may further include inserting a guard time based on the length of guard period during the transition from the first operational mode to the second operational mode. Aspects of block  920  may be performed by the guard period component  860  described with reference to  FIG.  8   . Thus, the modem  850 , the one or more processors  812 , and/or the IAB node  150  or one of its subcomponents may define the means for determining, at the IAB node, a length of guard period required for transition gap based on one or more of the RF-IF retuning latency, the downlink-to-uplink switching latency of the child node, or an estimated propagation delay between the IAB node and the child node. 
     At block  925 , the method  900  may include transmitting a dynamic timing indication to a child node that identifies the timing offset value. Aspects of block  925  may be performed by transceiver  802  described with reference to  FIG.  8   . The modem  850  of the IAB node  150  may send the dynamic timing indication to the transceiver  802  or the transmitter  808  of the IAB node  150 . The transceiver  802  or the transmitter  808  may convert the data into electrical signals. The RF front end  888  may filter and/or amplify the electrical signals into the electro-magnetic signals. The one or more antennas  865  of the IAB node  150  may transmit the electro-magnetic signals associated with the dynamic timing indication. Thus, the modem  850 , the transceiver  802 , the transmitter  808 , the RF front end  888 , the one or more antennas  865 , the one or more processors  812 , and/or the IAB node  150  or one of its subcomponents may define the means for transmitting the RRC information. Thus, the modem  850 , the transceiver  802 , the transmitter  808 , the RF front end  888 , the one or more antennas  865 , the one or more processors  812 , and/or the IAB node  150  or one of its subcomponents may define the means for transmitting a dynamic timing indication to a child node that identifies the timing offset value. 
     In a non-limiting example of a method for wireless communications in accordance with aspects of the present disclosure, the modem  850  of the IAB node  150  may receive a timing offset value (T offset ) from the parent node  415 . In certain examples, the parent node  415  may be a gNB, such as the base station  102 . The timing offset value, T offset , may account for the uplink-to-downlink or downlink-to-uplink switching latency of the parent node  415  and/or any hardware impairment. Thus, the modem  850 , the transceiver  802 , the transmitter  808 , the RF front end  888 , the one or more antennas  865 , the one or more processors  812 , and/or the IAB node  150  or one of its subcomponents may define the means for receiving the timing offset value (T offset ). 
     In some implementations, the operational mode component  855  and/or the timing management component  855  of the IAB node  150  may determine, at an integrated access and backhaul (IAB) node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing. For example, the timing management component  850  in collaboration with the operational mode component  855  described with reference to  FIG.  8    may determine to transition from a first operational mode to a second operational mode. The second access link timing may include at least one of the Access DL Tx or the Access UL Rx as shown in  FIG.  5 B , for example. The at least one of the Access DL Tx or the Access UL Rx may be temporally ahead of the BH DL Rx. In other words, the at least one of the Access DL Tx or the Access UL Rx may be a gap value (T G AP) in front of the BH DL Rx. 
     In some implementations, the timing management component  855  of the IAB node  150  may identify a gap value T GAP  separating the Access DL Tx from the BH DL Rx. The gap value T GAP  may be a function of the timing advance T TA  of the Access Link and/or the timing offset value T offset . In a non-limiting example, the timing advance T TA  may be a function of the T P_BH , which is the timing associated with the propagation delay between the BH UL Tx and the BH DL Rx (i.e., propagation time required for data to be transmitted from the IAB node  150  to the parent node  415  or from the parent node  415  to the IAB node  150 ). Similar to Equation 1 above, the T TA  (at the IAB node  150 ) may be described as T TA =2·T P_BH . In another example, the gap value T GAP  between the Access DL Tx and the BH DL Rx may be a function of the dynamic timing offset value T offset  from the parent node  415 . Thus, the modem  850 , the one or more processors  812 , and/or the IAB node  150  or one of its subcomponents may define the means for determining, at an integrated access and backhaul (IAB) node, to transition from a first operational mode to a second operational mode. Thus, the modem  850 , the one or more processors  812 , and/or the IAB node  150  or one of its subcomponents may define the means for identifying a timing offset value from a base reference time that is associated with the second operational mode. 
     In an aspect of the present disclosure, the gap value T GAP  between the Access DL Tx and the BH DL Rx may be T TA /2, as shown in  FIG.  5 A . In another example, the gap value T GAP  may be T TA , as shown in  FIG.  5 B . In yet another example, the gap value T GAP  may be 0, as shown in  FIG.  5 C . In other aspects of the present disclosure, the gap value T GAP  may be T TA /2+T offset . In some aspects, the gap value T GAP  may be T TA +T offset . 
     In one aspect of the present disclosure, the modem  850  of the transceiver  802  of the IAB node  150  may transmit a dynamic timing indication to a child node that identifies the gap value T GAP . Thus, the modem  850 , the transceiver  802 , the transmitter  808 , the RF front end  888 , the one or more antennas  865 , the one or more processors  812 , and/or the IAB node  150  or one of its subcomponents may define the means for transmitting a dynamic timing indication to a child node that identifies the timing offset value. 
     Some Further Example Embodiments 
     An aspect of the present disclosure includes a method for receiving a timing offset value from a parent node, determining, at an integrated access and backhaul (IAB) node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, identifying a gap value associated with the second operational mode, wherein the gap value is determined based on the timing offset value, and transmitting, to a child node, a dynamic timing indication identifying the gap value. 
     Some aspects of the present disclosure includes a method for receiving a timing offset value from a parent node, determining, at an integrated access and backhaul (IAB) node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, identifying a gap value associated with the second operational mode, wherein the gap value is determined based on the timing offset value, and transmitting, to a child node, a dynamic timing indication identifying the gap value. 
     Any of the above example methods, wherein identifying the gap value further includes determining the gap value based on a timing advance value associated with a propagation delay between the IAB node and the parent node and the timing offset value. 
     Any of the above example methods, wherein the timing advance value is a first sum of a first propagation time for first data to be transmitted from the IAB node to the parent node and a second propagation time for second data to be transmitted from the parent node to the IAB node. 
     Any of the above example methods, wherein the gap value is a second sum of the timing offset value and one-half of the timing advance value. 
     Any of the above example methods, wherein the timing offset value is associated with at least one of an uplink-to-downlink switching latency of the parent node, a downlink-to-uplink switching latency of the parent node, or a hardware impairment of the parent node. 
     Any of the above example methods, wherein receiving the timing offset value further comprises receiving the timing offset value from the parent node via radio resource control (RRC) configuration or media access control (MAC) control element (MAC-CE) signaling. 
     Any of the above example methods, wherein the gap value indicates a time between an access downlink transmission and a backhaul downlink reception. 
     Any of the above example methods, wherein the IAB node includes both a base station type functionality that allows for transmission and reception to and from the child node and a UE-type functionality that allows for transmission and reception to and from the parent node. 
     Any of the above example methods, wherein the child node is a user equipment (UE) or another IAB node. 
     An aspect of the present disclosure may include an apparatus having a memory having instructions and a processor configured to execute the instructions to perform the steps of determining, at an integrated access and backhaul node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, identifying a timing offset value from a base reference time that is associated with the second operational mode, and transmitting a dynamic timing indication to a child node that identifies the timing offset value. 
     Some aspects of the present disclosure may include an apparatus having a memory having instructions and a processor configured to execute the instructions to perform the steps of receiving a timing offset value from a parent node, determining, at an integrated access and backhaul (IAB) node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, identifying a gap value associated with the second operational mode, wherein the gap value is determined based on the timing offset value, and transmitting, to a child node, a dynamic timing indication identifying the gap value. 
     Any of the above example apparatuses, wherein identifying the gap value further includes determining the gap value based on a timing advance value associated with a propagation delay between the TAB node and the parent node and the timing offset value. 
     Any of the above example apparatuses, wherein the timing advance value is a first sum of a first propagation time for first data to be transmitted from the TAB node to the parent node and a second propagation time for second data to be transmitted from the parent node to the TAB node. 
     Any of the above example apparatuses, wherein the gap value is a second sum of the timing offset value and one-half of the timing advance value. 
     Any of the above example methods, wherein the timing offset value is associated with at least one of an uplink-to-downlink switching latency of the parent node, a downlink-to-uplink switching latency of the parent node, or a hardware impairment of the parent node. 
     Any of the above example apparatuses, wherein receiving the timing offset value further comprises receiving the timing offset value from the parent node via radio resource control (RRC) configuration or media access control (MAC) control element (MAC-CE) signaling. 
     Any of the above example apparatuses, wherein the gap value indicates a time between an access downlink transmission and a backhaul downlink reception. 
     Any of the above example apparatuses, wherein the IAB node includes both a base station type functionality that allows for transmission and reception to and from the child node and a UE-type functionality that allows for transmission and reception to and from the parent node. 
     Any of the above example apparatuses, wherein the child node is a user equipment (UE) or another IAB node. 
     An aspect of the present disclosure may include a non-transitory computer readable medium includes instructions stored therein that, when executed by a processor, cause the processor to perform the steps of determining, at an integrated access and backhaul node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, identifying a timing offset value from a base reference time that is associated with the second operational mode, and transmitting a dynamic timing indication to a child node that identifies the timing offset value. 
     Some aspects of the present disclosure may include a non-transitory computer readable medium includes instructions stored therein that, when executed by a processor, cause the processor to perform the steps of receiving a timing offset value from a parent node, determining, at an integrated access and backhaul (IAB) node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, identifying a gap value associated with the second operational mode, wherein the gap value is determined based on the timing offset value, and transmitting, to a child node, a dynamic timing indication identifying the gap value. 
     Any of the above example non-transitory computer readable media, wherein the instructions for identifying the gap value further includes instructions for determining the gap value based on a timing advance value associated with a propagation delay between the IAB node and the parent node and the timing offset value. 
     Any of the above example non-transitory computer readable media, wherein the timing advance value is a first sum of a first propagation time for first data to be transmitted from the IAB node to the parent node and a second propagation time for second data to be transmitted from the parent node to the IAB node. 
     Any of the above example non-transitory computer readable media, wherein the gap value is a second sum of the timing offset value and one-half of the timing advance value. 
     Any of the above example non-transitory computer readable media, wherein the timing offset value is associated with at least one of an uplink-to-downlink switching latency of the parent node, a downlink-to-uplink switching latency of the parent node, or a hardware impairment of the parent node. 
     Any of the above example non-transitory computer readable media, wherein the instructions for receiving the timing offset value further comprises instructions for receiving the timing offset value from the parent node via radio resource control (RRC) configuration or media access control (MAC) control element (MAC-CE) signaling. 
     Any of the above example non-transitory computer readable media, wherein the gap value indicates a time between an access downlink transmission and a backhaul downlink reception. 
     Any of the above example non-transitory computer readable media, wherein the IAB node includes both a base station type functionality that allows for transmission and reception to and from the child node and a UE-type functionality that allows for transmission and reception to and from the parent node. 
     Any of the above example non-transitory computer readable media, wherein the child node is a user equipment (UE) or another IAB node. 
     An aspect of the present disclosure may include an apparatus including means for determining, at an integrated access and backhaul node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, means for identifying a timing offset value from a base reference time that is associated with the second operational mode, and means for transmitting a dynamic timing indication to a child node that identifies the timing offset value. 
     Some aspects of the present disclosure may include an apparatus including means for receiving a timing offset value from a parent node, means for determining, at an integrated access and backhaul (IAB) node, to transition from a first operational mode to a second operational mode, wherein the first operational mode is associated with a first access link timing and the second operational mode is associated with a second access link timing, means for identifying a gap value associated with the second operational mode, wherein the gap value is determined based on the timing offset value, and means for transmitting, to a child node, a dynamic timing indication identifying the gap value. 
     Any of the above example apparatuses, wherein the means for identifying the gap value further includes means for determining the gap value based on a timing advance value associated with a propagation delay between the TAB node and the parent node and the timing offset value. 
     Any of the above example apparatuses, wherein the timing advance value is a first sum of a first propagation time for first data to be transmitted from the TAB node to the parent node and a second propagation time for second data to be transmitted from the parent node to the TAB node. 
     Any of the above example apparatuses, wherein the gap value is a second sum of the timing offset value and one-half of the timing advance value. 
     Any of the above example methods, wherein the timing offset value is associated with at least one of an uplink-to-downlink switching latency of the parent node, a downlink-to-uplink switching latency of the parent node, or a hardware impairment of the parent node. 
     Any of the above example apparatuses, wherein the means for receiving the timing offset value further comprises means for receiving the timing offset value from the parent node via radio resource control (RRC) configuration or media access control (MAC) control element (MAC-CE) signaling. 
     Any of the above example apparatuses, wherein the gap value indicates a time between an access downlink transmission and a backhaul downlink reception. 
     Any of the above example apparatuses, wherein the TAB node includes both a base station type functionality that allows for transmission and reception to and from the child node and a UE-type functionality that allows for transmission and reception to and from the parent node. 
     Any of the above example apparatuses, wherein the child node is a user equipment (UE) or another TAB node. 
     The above detailed description set forth above in connection with the appended drawings describes examples and does not represent the only examples that may be implemented or that are within the scope of the claims. The term “example,” when used in this description, means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, well-known structures and apparatuses are shown in block diagram form in order to avoid obscuring the concepts of the described examples. 
     Information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, computer-executable code or instructions stored on a computer-readable medium, or any combination thereof. 
     The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a specially-programmed device, such as but not limited to a processor, a digital signal processor (DSP), an ASIC, a FPGA or other programmable logic device, a discrete gate or transistor logic, a discrete hardware component, or any combination thereof designed to perform the functions described herein. A specially-programmed processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A specially-programmed processor may also be implemented as a combination of computing 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 herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a non-transitory computer-readable medium. Other examples and implementations are within the scope and spirit of the disclosure and appended claims. For example, due to the nature of software, functions described above may be implemented using software executed by a specially programmed processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. Also, as used herein, including in the claims, “or” as used in a list of items prefaced by “at least one of” indicates a disjunctive list such that, for example, a list of “at least one of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). 
     Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage medium may be any available medium that may be accessed by a general purpose or special purpose computer. By way of example, and not limitation, computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media. 
     It should be noted that the techniques described above may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and other systems. The terms “system” and “network” are often used interchangeably. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and A are commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM™, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies, including cellular (e.g., LTE) communications over a shared radio frequency spectrum band. The description below, however, describes an LTE/LTE-A system for purposes of example, and LTE terminology is used in much of the description below, although the techniques are applicable beyond LTE/LTE-A applications (e.g., to 5G networks or other next generation communication systems). 
     The previous description of the disclosure is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the common principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Furthermore, although elements of the described aspects and/or embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or embodiment may be utilized with all or a portion of any other aspect and/or embodiment, unless stated otherwise. Thus, the disclosure is not to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.