Patent Publication Number: US-2022225451-A1

Title: Modes of simultaneous connectivity in integrated access and backhaul

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of and priority to U.S. Provisional Application Ser. No. 63/137,699, entitled “Modes of Simultaneous Connectivity in Integrated Access and Backhaul” and filed on Jan. 14, 2021, which is expressly incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to communication systems, and more particularly, to modes of simultaneous connectivity in an integrated access and backhaul (IAB) network. 
     INTRODUCTION 
     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. 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, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems. 
     These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is 5G New Radio (NR). 5G NR is part of a continuous mobile broadband evolution promulgated by Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with Internet of Things (IoT)), and other requirements. 5G NR includes services associated with enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and ultra-reliable low latency communications (URLLC). Some aspects of 5G NR may be based on the 4G Long Term Evolution (LTE) standard. There exists a need for further improvements in 5G NR technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies. 
     BRIEF SUMMARY 
     The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later. 
     In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be associated with a first base station and configured to establish a first connection with an integrated access and backhaul (IAB) node; transmit, to a second base station, a request for the second base station to establish a second connection with the IAB node; and indicate to the second base station, based on the second connection being established with the IAB node, that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. 
     In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be associated with a second base station and configured to receive, from a first base station having a first connection with an IAB node, a request for the second base station to establish a second connection with the IAB node; receive from the first base station, based on the second connection being established with the IAB node, an indication that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node; and accept or reject the indication received from the first base station that the at least one of the first base station or the second base station is to serve as the IAB donor for the IAB node. 
     In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be associated with an IAB node and configured to establish a first connection with a first base station; establish a second connection with a second base station; and receive an indication, from the first base station, indicating that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. 
     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 
         FIG. 1  is a diagram illustrating an example of a wireless communications system and an access network. 
         FIG. 2A  is a diagram illustrating an example of a first frame, in accordance with various aspects of the present disclosure. 
         FIG. 2B  is a diagram illustrating an example of DL channels within a subframe, in accordance with various aspects of the present disclosure. 
         FIG. 2C  is a diagram illustrating an example of a second frame, in accordance with various aspects of the present disclosure. 
         FIG. 2D  is a diagram illustrating an example of UL channels within a subframe, in accordance with various aspects of the present disclosure. 
         FIG. 3  is a diagram illustrating an example of a base station and user equipment (UE) in an access network. 
         FIG. 4  is a diagram illustrating an integrated access and backhaul (IAB) network. 
         FIG. 5  is a diagram illustrating an IAB network and components thereof. 
         FIG. 6  is a diagram illustrating radio link control (RLC) channels in an IAB network. 
         FIGS. 7A-7B  illustrate diagrams for control-plane/user-plane (CP-UP) separation. 
         FIGS. 8A-8B  illustrate diagrams for inter-donor topological redundancy. 
         FIGS. 9A-9C  illustrate modes of dual connection for an IAB node. 
         FIG. 10  is a call flow diagram illustrating communications between a first base station, a second base station, and an IAB node. 
         FIG. 11  is a flowchart of a method of wireless communication of a first base station. 
         FIG. 12  is a flowchart of a method of wireless communication of a first base station. 
         FIG. 13  is a flowchart of a method of wireless communication of a second base station. 
         FIG. 14  is a flowchart of a method of wireless communication of a second base station. 
         FIG. 15  is a flowchart of a method of wireless communication of an IAB node. 
         FIG. 16  is a flowchart of a method of wireless communication of an IAB node. 
         FIG. 17  is a diagram illustrating an example of a hardware implementation for an example apparatus. 
         FIG. 18  is a diagram illustrating an example of a hardware implementation for an example apparatus. 
         FIG. 19  is a diagram illustrating an example of a hardware implementation for an example apparatus. 
     
    
    
     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 this 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. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can 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 can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer. 
     While aspects and implementations are described in this application by illustration to some examples, those skilled in the art will understand that additional implementations and use cases may come about in many different arrangements and scenarios. Aspects described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, and packaging arrangements. For example, implementations and/or uses may come about via integrated chip implementations and other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, artificial intelligence (AI)-enabled devices, etc.). While some examples may or may not be specifically directed to use cases or applications, a wide assortment of applicability of described aspects may occur. Implementations may range a spectrum from chip-level or modular components to non-modular, non-chip-level implementations and further to aggregate, distributed, or original equipment manufacturer (OEM) devices or systems incorporating one or more aspects of the described aspects. In some practical settings, devices incorporating described aspects and features may also include additional components and features for implementation and practice of claimed and described aspect. For example, transmission and reception of wireless signals necessarily includes a number of components for analog and digital purposes (e.g., hardware components including antenna, RF-chains, power amplifiers, modulators, buffer, processor(s), interleaver, adders/summers, etc.). It is intended that aspects described herein may be practiced in a wide variety of devices, chip-level components, systems, distributed arrangements, aggregated or disaggregated components, end-user devices, etc. of varying sizes, shapes, and constitution. 
       FIG. 1  is a diagram illustrating an example of a wireless communications system and an access network  100 . The wireless communications system (also referred to as a wireless wide area network (WWAN)) includes base stations  102 , UEs  104 , an Evolved Packet Core (EPC)  160 , and another core network  190  (e.g., a 5G Core (5GC)). The base stations  102  may include macrocells (high power cellular base station) and/or small cells (low power cellular base station). The macrocells include base stations. The small cells include femtocells, picocells, and microcells. 
     The base stations  102  configured for 4G LTE (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with the EPC  160  through first backhaul links  132  (e.g., S1 interface). The base stations  102  configured for 5G NR (collectively referred to as Next Generation RAN (NG-RAN)) may interface with core network  190  through second backhaul links  184 . In addition to other 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 directly or indirectly (e.g., through the EPC  160  or core network  190 ) with each other over third backhaul links  134  (e.g., X2 interface). The first backhaul links  132 , the second backhaul links  184 , and the third backhaul links  134  may be wired or wireless. 
     The base stations  102  may wirelessly communicate with the UEs  104 . Each of the base stations  102  may provide communication coverage for a respective geographic coverage area  110 . There may be overlapping geographic coverage areas  110 . For example, the small cell  102 ′ may have a coverage area  110 ′ that overlaps the coverage area  110  of one or more macro base stations  102 . A network that includes both small cell and macrocells may be known as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (eNBs) (HeNBs), which may provide service to a restricted group known as a closed subscriber group (CSG). The communication links  120  between the base stations  102  and the UEs  104  may include uplink (UL) (also referred to as reverse link) transmissions from a UE  104  to a base station  102  and/or downlink (DL) (also referred to as forward link) transmissions from a base station  102  to a UE  104 . The communication links  120  may use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links may be through one or more carriers. The base stations  102 /UEs  104  may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x 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 fewer 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  104  may communicate with each other using device-to-device (D2D) communication link  158 . The D2D communication link  158  may use the DL/UL WWAN spectrum. The D2D communication link  158  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, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, LTE, or NR. 
     The wireless communications system may further include a Wi-Fi access point (AP)  150  in communication with Wi-Fi stations (STAs)  152  via communication links  154 , e.g., in a 5 GHz unlicensed frequency spectrum or the like. When communicating in an unlicensed frequency spectrum, the STAs  152 /AP  150  may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available. 
     The small cell  102 ′ may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell  102 ′ may employ NR and use the same unlicensed frequency spectrum (e.g., 5 GHz, or the like) as used by the Wi-Fi AP  150 . The small cell  102 ′, employing NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. 
     The electromagnetic spectrum is often subdivided, based on frequency/wavelength, into various classes, bands, channels, etc. In 5G NR, two initial operating bands have been identified as frequency range designations FR1 (410 MHz-7.125 GHz) and FR2 (24.25 GHz-52.6 GHz). The frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Although a portion of FR1 is greater than 6 GHz, FR1 is often referred to (interchangeably) as a “sub-6 GHz” band in various documents and articles. A similar nomenclature issue sometimes occurs with regard to FR2, which is often referred to (interchangeably) as a “millimeter wave” band in documents and articles, despite being different from the extremely high frequency (EHF) band (30 GHz-300 GHz) which is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band. 
     With the above aspects in mind, unless specifically stated otherwise, it should be understood that the term “sub-6 GHz” or the like if used herein may broadly represent frequencies that may be less than 6 GHz, may be within FR1, or may include mid-band frequencies. Further, unless specifically stated otherwise, it should be understood that the term “millimeter wave” or the like if used herein may broadly represent frequencies that may include mid-band frequencies, may be within FR2, or may be within the EHF band. 
     A base station  102 , whether a small cell  102 ′ or a large cell (e.g., macro base station), may include and/or be referred to as an eNB, gNodeB (gNB), or another type of base station. Some base stations, such as gNB may operate in a traditional sub 6 GHz spectrum, in millimeter wave frequencies, and/or near millimeter wave frequencies in communication with the UE  104 . When the gNB operates in millimeter wave or near millimeter wave frequencies, the gNB may be referred to as a millimeter wave base station. The millimeter wave base station  180  may utilize beamforming  182  with the UE  104  to compensate for the path loss and short range. The base station  180  and the UE  104  may each include a plurality of antennas, such as antenna elements, antenna panels, and/or antenna arrays to facilitate the beamforming. 
     The base station  180  may transmit a beamformed signal to the UE  104  in one or more transmit directions  182 ′. The UE  104  may receive the beamformed signal from the base station  180  in one or more receive directions  182 ″. The UE  104  may also transmit a beamformed signal to the base station  180  in one or more transmit directions. The base station  180  may receive the beamformed signal from the UE  104  in one or more receive directions. The base station  180 /UE  104  may perform beam training to determine the best receive and transmit directions for each of the base station  180 /UE  104 . The transmit and receive directions for the base station  180  may or may not be the same. The transmit and receive directions for the UE  104  may or may not be the same. 
     The EPC  160  may include a Mobility Management Entity (MME)  162 , other MMEs  164 , a Serving Gateway  166 , a Multimedia Broadcast Multicast Service (MBMS) Gateway  168 , a Broadcast Multicast Service Center (BM-SC)  170 , and a Packet Data Network (PDN) Gateway  172 . The MME  162  may be in communication with a Home Subscriber Server (HSS)  174 . The MME  162  is the control node that processes the signaling between the UEs  104  and the EPC  160 . Generally, the MME  162  provides bearer and connection management. All user Internet protocol (IP) packets are transferred through the Serving Gateway  166 , which itself is connected to the PDN Gateway  172 . The PDN Gateway  172  provides UE IP address allocation as well as other functions. The PDN Gateway  172  and the BM-SC  170  are connected to the IP Services  176 . The IP Services  176  may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service, and/or other IP services. The BM-SC  170  may provide functions for MBMS user service provisioning and delivery. The BM-SC  170  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  168  may be used to distribute MBMS traffic to the base stations  102  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 core network  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  104  and the core network  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 Packet Switch (PS) Streaming (PSS) Service, and/or other IP services. 
     The base station may include and/or be referred to as a gNB, Node B, eNB, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), a transmit reception point (TRP), or some other suitable terminology. The base station  102  provides an access point to the EPC  160  or core network  190  for a UE  104 . Examples of UEs  104  include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), 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 tablet, 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. Some of the UEs  104  may be referred to as IoT devices (e.g., parking meter, gas pump, toaster, vehicles, heart monitor, etc.). The UE  104  may also be referred to as a station, 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. 
     Referring again to  FIG. 1 , in certain aspects, a first base station  102  or  180  may include an integrated access and backhaul (IAB) donor designation component  198  configured to establish a first connection with an IAB node  103 ; transmit, to a second base station, a request for the second base station to establish a second connection with the IAB node  103 ; and indicate to the second base station, based on the second connection being established with the IAB node  103 , that at least one of a first base station or the second base station is to serve as an IAB donor for the IAB node  103 . In certain aspects, a second base station  102  or  180  may include an IAB donor acceptance-rejection component  199  configured to receive, from a first base station  102  or  180  having a first connection with the IAB node  103 , a request for a second base station  102  or  180  to establish a second connection with the IAB node  103 ; receive from the first base station, based on the second connection being established with the IAB node  103 , an indication that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node  103 ; and accept or reject the indication received from the first base station that the at least one of the first base station or the second base station is to serve as the IAB donor for the IAB node  103 . In certain aspects, the IAB node  103  may include an IAB donor determination component  191  configured to establish a first connection with a first base station  102  or  180 ; establish a second connection with a second base station  102  or  180 ; and receive an indication, from the first base station, indicating that at least one of the first base station or the second base station is to serve as an IAB donor for an IAB node  103 . Although the following description may be focused on 5G NR, the concepts described herein may be applicable to other similar areas, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies. 
       FIG. 2A  is a diagram  200  illustrating an example of a first subframe within a 5G NR frame structure.  FIG. 2B  is a diagram  230  illustrating an example of DL channels within a 5G NR subframe.  FIG. 2C  is a diagram  250  illustrating an example of a second subframe within a 5G NR frame structure.  FIG. 2D  is a diagram  280  illustrating an example of UL channels within a 5G NR subframe. The 5G NR frame structure may be frequency division duplexed (FDD) in which for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated for either DL or UL, or may be time division duplexed (TDD) in which for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated for both DL and UL. In the examples provided by  FIGS. 2A, 2C , the 5G NR frame structure is assumed to be TDD, with subframe 4 being configured with slot format 28 (with mostly DL), where D is DL, U is UL, and F is flexible for use between DL/UL, and subframe 3 being configured with slot format 1 (with all UL). While subframes 3, 4 are shown with slot formats 1, 28, respectively, any particular subframe may be configured with any of the various available slot formats 0-61. Slot formats 0, 1 are all DL, UL, respectively. Other slot formats 2-61 include a mix of DL, UL, and flexible symbols. UEs are configured with the slot format (dynamically through DL control information (DCI), or semi-statically/statically through radio resource control (RRC) signaling) through a received slot format indicator (SFI). Note that the description infra applies also to a 5G NR frame structure that is TDD. 
       FIGS. 2A-2D  illustrate a frame structure, and the aspects of the present disclosure may be applicable to other wireless communication technologies, which may have a different frame structure and/or different channels. A frame (10 ms) may be divided into 10 equally sized subframes (1 ms). Each subframe may include one or more time slots. Subframes may also include mini-slots, which may include 7, 4, or 2 symbols. Each slot may include 14 or 12 symbols, depending on whether the cyclic prefix (CP) is normal or extended. For normal CP, each slot may include 14 symbols, and for extended CP, each slot may include 12 symbols. The symbols on DL may be CP orthogonal frequency division multiplexing (OFDM) (CP-OFDM) symbols. The symbols on UL may be CP-OFDM symbols (for high throughput scenarios) or discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (also referred to as single carrier frequency-division multiple access (SC-FDMA) symbols) (for power limited scenarios; limited to a single stream transmission). The number of slots within a subframe is based on the CP and the numerology. The numerology defines the subcarrier spacing (SCS) and, effectively, the symbol length/duration, which is equal to 1/SCS. 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                   
                 SCS 
                   
               
               
                   
                 μ 
                 Δf = 2 μ  · 15[kHz] 
                 Cyclic prefix 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 0 
                 15 
                 Normal 
               
               
                   
                 1 
                 30 
                 Normal 
               
               
                   
                 2 
                 60 
                 Normal, Extended 
               
               
                   
                 3 
                 120 
                 Normal 
               
               
                   
                 4 
                 240 
                 Normal 
               
               
                   
                   
               
            
           
         
       
     
     For normal CP (14 symbols/slot), different numerologies μ 0 to 4 allow for 1, 2, 4, 8, and 16 slots, respectively, per subframe. For extended CP, the numerology 2 allows for 4 slots per subframe. Accordingly, for normal CP and numerology μ, there are 14 symbols/slot and 2 μ  slots/subframe. The subcarrier spacing may be equal to 2 μ *15 kHz, where μ is the numerology 0 to 4. As such, the numerology μ=0 has a subcarrier spacing of 15 kHz and the numerology μ=4 has a subcarrier spacing of 240 kHz. The symbol length/duration is inversely related to the subcarrier spacing.  FIGS. 2A-2D  provide an example of normal CP with 14 symbols per slot and numerology μ=2 with 4 slots per subframe. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is approximately 16.67 μs. Within a set of frames, there may be one or more different bandwidth parts (BWPs) (see  FIG. 2B ) that are frequency division multiplexed. Each BWP may have a particular numerology and CP (normal or extended). 
     A resource grid may be used to represent the frame structure. Each time slot includes a resource block (RB) (also referred to as physical RBs (PRBs)) that extends 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme. 
     As illustrated in  FIG. 2A , some of the REs carry reference (pilot) signals (RS) for the UE. The RS may include demodulation RS (DM-RS) (indicated as R for one particular configuration, but other DM-RS configurations are possible) and channel state information reference signals (CSI-RS) for channel estimation at the UE. The RS may also include beam measurement RS (BRS), beam refinement RS (BRRS), and phase tracking RS (PT-RS). 
       FIG. 2B  illustrates an example of various DL channels within a subframe of a frame. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs) (e.g., 1, 2, 4, 8, or 16 CCEs), each CCE including six RE groups (REGs), each REG including 12 consecutive REs in an OFDM symbol of an RB. A PDCCH within one BWP may be referred to as a control resource set (CORESET). A UE is configured to monitor PDCCH candidates in a PDCCH search space (e.g., common search space, UE-specific search space) during PDCCH monitoring occasions on the CORESET, where the PDCCH candidates have different DCI formats and different aggregation levels. Additional BWPs may be located at greater and/or lower frequencies across the channel bandwidth. A primary synchronization signal (PSS) may be within symbol 2 of particular subframes of a frame. The PSS is used by a UE  104  to determine subframe/symbol timing and a physical layer identity. A secondary synchronization signal (SSS) may be within symbol 4 of particular subframes of a frame. The SSS is used by a UE to determine a physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI). Based on the PCI, the UE can determine the locations of the aforementioned DM-RS. The physical broadcast channel (PBCH), which carries a master information block (MIB), may be logically grouped with the PSS and SSS to form a synchronization signal (SS)/PBCH block (also referred to as SS block (SSB)). The MIB provides a number of RBs in the system bandwidth and a system frame number (SFN). The physical downlink shared channel (PDSCH) carries user data, broadcast system information not transmitted through the PBCH such as system information blocks (SIBs), and paging messages. 
     As illustrated in  FIG. 2C , some of the REs carry DM-RS (indicated as R for one particular configuration, but other DM-RS configurations are possible) for channel estimation at the base station. The UE may transmit DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH). The PUSCH DM-RS may be transmitted in the first one or two symbols of the PUSCH. The PUCCH DM-RS may be transmitted in different configurations depending on whether short or long PUCCHs are transmitted and depending on the particular PUCCH format used. The UE may transmit sounding reference signals (SRS). The SRS may be transmitted in the last symbol of a subframe. The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. The SRS may be used by a base station for channel quality estimation to enable frequency-dependent scheduling on the UL. 
       FIG. 2D  illustrates an example of various UL channels within a subframe of a frame. The PUCCH may be located as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and hybrid automatic repeat request (HARQ) acknowledgment (ACK) (HARQ-ACK) information (ACK/negative ACK (NACK)) feedback. The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), and/or UCI. 
       FIG. 3  is a block diagram of a first wireless device  310  in communication with a second wireless device  350  in an access network. In some examples, the first wireless device may be base station and the second wireless device may be a UE. In other examples, the first wireless device  310  may be a base station and the second wireless device  350  may be a second base station. In some examples, the first wireless device  310  may be a base station and the second wireless device may be an IAB node. In some examples, the first wireless device  310  may be an IAB node and the second wireless device  350  may be a UE. 
     In the DL, IP packets from the EPC  160  may be provided to a controller/processor  375 . The controller/processor  375  implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller/processor  375  provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIBs), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functionality associated with header compression/decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with the transfer of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization. 
     The transmit (TX) processor  316  and the receive (RX) processor  370  implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, may include error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and MIMO antenna processing. The TX processor  316  handles mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator  374  may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the second wireless device  350 . Each spatial stream may then be provided to a different antenna  320  via a separate transmitter  318  TX. Each transmitter  318  TX may modulate an RF carrier with a respective spatial stream for transmission. 
     At the second wireless device  350 , each receiver  354  RX receives a signal through its respective antenna  352 . Each receiver  354  RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor  356 . The TX processor  368  and the RX processor  356  implement layer 1 functionality associated with various signal processing functions. The RX processor  356  may perform spatial processing on the information to recover any spatial streams destined for the second wireless device  350 . If multiple spatial streams are destined for the second wireless device  350 , they may be combined by the RX processor  356  into a single OFDM symbol stream. The RX processor  356  then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the first wireless device  310 . These soft decisions may be based on channel estimates computed by the channel estimator  358 . The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the first wireless device  310  on the physical channel. The data and control signals are then provided to the controller/processor  359 , which implements layer 3 and layer 2 functionality. 
     The controller/processor  359  can be associated with a memory  360  that stores program codes and data. The memory  360  may be referred to as a computer-readable medium. In the UL, the controller/processor  359  provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the EPC  160 . The controller/processor  359  is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations. 
     Similar to the functionality described in connection with the DL transmission by the first wireless device  310 , the controller/processor  359  provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression/decompression, and security (ciphering, deciphering, integrity protection, integrity verification); RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization. 
     Channel estimates derived by a channel estimator  358  from a reference signal or feedback transmitted by the first wireless device  310  may be used by the TX processor  368  to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor  368  may be provided to different antenna  352  via separate transmitters  354 TX. Each transmitter  354 TX may modulate an RF carrier with a respective spatial stream for transmission. 
     The UL transmission is processed at the first wireless device  310  in a manner similar to that described in connection with the receiver function at the second wireless device  350 . Each receiver  318 RX receives a signal through its respective antenna  320 . Each receiver  318 RX recovers information modulated onto an RF carrier and provides the information to a RX processor  370 . 
     The controller/processor  375  can be associated with a memory  376  that stores program codes and data. The memory  376  may be referred to as a computer-readable medium. In the UL, the controller/processor  375  provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from the second wireless device  350 . IP packets from the controller/processor  375  may be provided to the EPC  160 . The controller/processor  375  is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations. 
     At least one of the TX processor  316 , the RX processor  370 , and the controller/processor  375  may be configured to perform aspects in connection with the IAB donor designation component  198  of  FIG. 1 . 
     At least one of the TX processor  316 , the RX processor  370 , and the controller/processor  375  may be configured to perform aspects in connection with the IAB donor acceptance-rejection component  199  of  FIG. 1 . 
     At least one of the TX processor  316 , the RX processor  370 , and the controller/processor  375  may be configured to perform aspects in connection with the IAB donor determination component  191  of  FIG. 1 . 
     Wireless communication systems may be configured to share available system resources and provide various telecommunication services (e.g., telephony, video, data, messaging, broadcasts, etc.) based on multiple-access technologies such as CDMA systems, TDMA systems, FDMA systems, OFDMA systems, SC-FDMA systems, TD-SCDMA systems, etc. that support communication with multiple users. In many cases, common protocols that facilitate communications with wireless devices are adopted in various telecommunication standards. For example, communication methods associated with eMBB, mMTC, and URLLC may be incorporated in the 5G NR telecommunication standard, while other aspects may be incorporated in the 4G LTE standard. As mobile broadband technologies are part of a continuous evolution, further improvements in mobile broadband remain useful to continue the progression of such technologies. 
       FIG. 4  is a diagram illustrating an IAB network  400 . The IAB network provides access network functionality between access nodes (ANs) and other ANs/UEs, and backhaul network functionality between ANs. The ANs include IAB-donors, which have a wireline connection to a core network  490 , and IAB-nodes, which operate wirelessly and relay traffic to/from IAB-donors through one or more AN hops. The IAB ANs share resources between the access and backhaul. That is, the resources used for access communication between the ANs and the ANs/UEs are also used for backhaul communication between the ANs. 
     The IAB network  400  may include an anchor node, which may be referred to herein as an “IAB donor”  410 , and access nodes, which may be referred to herein as “IAB nodes”  420 . The IAB donor  410  may be a base station, such as a gNB or eNB, and may perform functions to control the IAB network  400 . The IAB nodes  420  may comprise L2 relay nodes, etc. Together, the IAB donor  410  and the IAB nodes  420  share resources to provide an access network and a backhaul network to the core network  490 . For example, resources may be shared between access links and backhaul links in the IAB network. 
     UEs  430  interface with the IAB nodes  420  or the IAB donor  410  through access links  470 . The IAB nodes  420  communicate with each other and with the IAB donor  410  through backhaul links  460 . The IAB donor  410  is connected to the core network  490  via a wireline backhaul link  450 . The UEs  430  communicate with the core network  490  by relaying messages through their respective access link  470  to the IAB network  400 , which then may relay the message through backhaul links  460  to the IAB donor  410  to communicate with the core network  490  through the wireline backhaul link  450 . Similarly, the core network  490  may communicate with a UE  430  by sending a message to the IAB donor  410  through the wireline backhaul link  450 . The IAB donor  410  sends the message through the IAB network  400  via backhaul links  460  to the IAB node  420  connected to the UE  430 , and the IAB node  420  sends the message to the UE  430  via the access link  470 . 
     Each IAB node, e.g., including IAB donor  410  and each IAB node  420 , may use a PCI value. The PCI value may serve as an identifier for the IAB donor  410  or the IAB node  420 . The PCI value may be used to determine a scrambling sequence that may be applied to physical signals and/or channels that are transmitted by a particular IAB node. For example, a PSS and/or the SSS transmitted by the respective IAB donor  410  or IAB node  420  may be scrambled using a scrambling sequence that may be based on the PCI used by the respective IAB node. 
       FIG. 5  is a diagram illustrating an IAB network  500  and components thereof. The IAB network  500  includes an IAB donor node  510  and IAB nodes  520   a - 520   b . The IAB nodes  520   a - 520   b , as well as the IAB donor node  510 , may provide wireless access links to UEs  530   a - 530   c.    
     The IAB donor node  510  may be considered a root node of the tree structure of the IAB network  500 . The IAB donor node  510  may be connected to the core network  590  via a wired connection  591 . The wired connection may comprise, e.g., a wireline fiber. The IAB donor node  510  may provide a connection to one or more IAB nodes  520   a . The IAB nodes  520   a  may each be referred to as a child node of the IAB donor node  510 . The IAB donor node  510  may also provide a connection to one or more UE  530   a , which may be referred to as a child UE of the IAB donor node  510 . The IAB donor node  510  may be connected to its child IAB nodes  520   a  via backhaul links  560 , and may be connected to the child UEs  530   a  via access links  570 . The IAB nodes  520   a  that are children nodes of IAB node  510  may also have IAB node(s)  520   b  and/or UE(s)  530   b  as children. For example, IAB nodes  520   b  may further connect to child nodes and/or child UEs.  FIG. 5  illustrates IAB nodes  520   b  providing an access link to UEs  530   c , respectively. 
     The IAB donor node  510  may include a central unit (CU) and a distributed unit (DU). The CU may provide control for the IAB nodes  520   a ,  520   b  in the IAB network  500 . For example, the CU may control the IAB network  500  through configuration. The CU may perform RRC/PDCP layer functions. The IAB donor nodes  510  further include a DU that may perform scheduling. For example, the DU may schedule resources for communication by the child IAB nodes  520   a  and/or UEs  530   a  of the IAB donor node  510 . The DU is associated with radio link control (RLC), media access control (MAC), and physical (PHY) layer functions. 
     The IAB nodes  520   a ,  520   b  may include a mobile termination (MT) and a DU. The IAB node may be an L2 relay node. The MT of IAB node  520   a  may operate as a scheduled node that may be scheduled similar to a UE  530   a  by the DU of the parent node, e.g., IAB donor node  510 . The MT of IAB node  520   b  may operate as a scheduled node of parent node  520   a . The DU may schedule the child IAB nodes  520   b  and UEs  530   b  of the IAB node  520   a . An IAB node may provide a connection to an IAB node that in turn provides another connection for another IAB node. The pattern of a parent IAB node comprising a DU that schedules a child IAB node/child UE may continue to more connections. 
       FIG. 6  is a diagram  600  illustrating RLC channels in an IAB network. As discussed supra, the IAB network provides both access network functionality and backhaul network functionality. The IAB network includes an IAB donor with a CU  602  and a DU  604 . In order to provide access network functionality, IAB nodes  606   a ,  606   b , and  606   c  may communicate with other UEs  608   a  and  608   b  and/or MTs of other IAB ANs through access RLC channels. Thus, the IAB nodes  606   a ,  606   b , and  606   c  operate as access IAB nodes for their child nodes or UEs. In order to provide backhaul network functionality, IAB nodes  606   a ,  606   b , and  606   c  may route traffic to other IAB nodes (e.g.,  606   a ,  606   b , and  606   c ) through backhaul RLC channels (BH RLC CHs). Thus, the IAB nodes  606   a ,  606   b , and  606   c  may operate as intermediate IAB nodes when backhauling traffic for other IAB nodes. Access RLC channels include UE-to-DU/DU-to-UE, carrying PDCP for RRC or data radio bearers (DRBs), and MT-to-DU/DU-to-MT, carrying PDCP for RRC (or DRBs). BH RLC CHs include MT-to-DU/DU-to-MT, carrying backhaul adaptation protocol (BAP) messages for backhauling access traffic. 
       FIGS. 7A-7B  include diagrams  700 - 750  illustrating control-plane/user-plane (CP-UP) separation based on dual connectivity. In the diagram  700 , an F1-control-plane (F1-C) interface between IAB node 2  702   a  and an IAB-donor-CU  708   a  may be based on an access link via a primary RAN node (e.g., non-donor node). The primary RAN node may be referred to as a master-NG-RAN (M-NG-RAN) node  710 . The F1 user-plane (F1-U) interface between the IAB node 2  702   a  and the IAB-donor-CU  708   a  may be based on a backhaul link via IAB node 1  704   a  and IAB-donor-DU  706   a . More specifically, the IAB node 2  702   a  may be dual connected based on connections to the M-NG-RAN  710  and the IAB node 1  704   a . Since an IAB node may have UE-functionality, the IAB node 2  702   a  may be RRC-connected to both the M-NG-RAN node  710  and the IAB-donor-CU  708   a . Dual connectivity may be based on a single physical link or multiple physical links. For example, the IAB node 2  702   a  may be connected to a secondary node (e.g., IAB-donor-CU  708   a ) via the master node (e.g., M-NG-RAN  710 ) without a physical link between the IAB node 2 and the master node, or the IAB node 2  702   a  may be connected to the master node and the secondary node based on physical links between each of the nodes. 
     Different connections between nodes via the F1 interface may provide different levels of coverage robustness for the control-plane (c-plane) or different levels of capacity for the user-plane (u-plane). Robust coverage may be associated with the sub-6 GHz frequency band, as such signals may be less affected by attenuation than signals based on the millimeter wave (mmW) frequency band. For example, the M-NG-RAN node  710  may be a base station that serves one or more child nodes via sub-6 GHz signals, which may have robust coverage that allows the M-NG-RAN node  710  to communicate with a child node in a single hop. In contrast, mmW signals, which may be affected by attenuation, may not be used to communicate over as large of a physical distance as sub-6 GHz signals. Thus, multiple hops may be performed between the IAB node 2  702   a  and the IAB-donor-CU  708   a , e.g., via the IAB node 1  704   a  and the IAB-donor-DU  706   a . However, mmW signals may be associated with large bands of frequencies, which may be utilized to provide increased capacity over sub-6 GHz signals. 
     In configurations, the IAB node 2  702  may be connected to a first base station via sub-6 GHz signaling and connected to a second base station via mmW signaling. For example, F1 signaling may be split at the IAB node 2  702   a  such that an access link may be used for the c-plane and a backhaul link may be used for the u-plane. A difference between a base station (e.g., M-NG-RAN  710 ) and an IAB donor (e.g., IAB-donor-CU  708   a ) may be that the IAB donor is a base station that is configured to support IAB functionality. If the M-NG-RAN node  710  is a base station that does not support/assert IAB functionality, the F1-U connection for the DU of the IAB node 2  702   a  may utilize multiple hops on the backhaul link via mmW signaling, whereas the F1-C connection may utilize an RRC connection of the MT of the IAB node 2  702   a  for transmitting containers to the IAB-donor-CU  708   a  via the M-NG-RAN  710 . 
     In the diagram  750 , the F1-C interface between IAB node 2  702   b  and IAB-donor-CU  708   b  may be based on an access link via a secondary-NG-RAN (S-NG-RAN) node  712  (e.g., non-donor node), and the F1-U interface between the IAB node 2  702   b  and the IAB-donor-CU  708   b  may be based on a backhaul link via IAB node 1  704   b  and IAB-donor-DU  706   b . In examples, the IAB-donor-CU  708   b  may be a master node that may receive a container over the F1-C interface in a single hop via the S-NG-RAN node  712 . The single hop of the F1-C interface may provide robust coverage, whereas the F1-U interface may be associated with multiple hops but may provide increased capacity. 
     Accordingly, in the diagram  700 , the F1-C interface may be based on use of the access link to communicate with the secondary node and the F1-U interface may be based on use of the backhaul link to communicate with the secondary node, where the master node (e.g., M-NG-RAN  710 ) may be a non-donor node and the secondary node (e.g., IAB-donor-CU  708   a ) may be a donor node. Alternatively, in the diagram  750 , the F1-C interface may be based on use of the backhaul link to communicate with the master node and the F1-U interface may be based on use of the access link to communicate with the master node, where the secondary node (e.g., S-NG-RAN  712 ) may be a non-donor node and the master node (e.g., IAB-donor-CU  708   b ) may be a donor node. In either case, the access link and/or the backhaul link may be based on either mmW signaling and/or sub-6 GHz signaling. Further, the access link and/or the backhaul link may be based on single hop or multi-hop configurations. A difference between utilizing an access link and a backhaul link for communication is that access link traffic may be carried on access RLC channels, whereas backhaul link traffic may be carried on a BAP via backhaul RLC channels. In the diagrams  700 - 750 , the F1-C connection is routed over an RRC of an access link, while the F1-U connection is routed over a backhaul BAP/IP layer. 
       FIGS. 8A-8B  include diagrams  800 - 850  illustrating inter-donor topological redundancy. When an IAB node (e.g., IAB3 node  802 - 803 ) is dual connected to two donor nodes (e.g., Donor1-DU  806  and Donor2-DU  812 ), the backhaul link may include a first leg and a second leg. The first leg may include the IAB3 node  802 - 803  having an IAB3-MT  803  and an IAB3-DU  802 , an IAB1 node  804  having an IAB1-MT and an IAB1-DU, a Donor1-DU  806 , and a Donor1-CU  808 . The second leg may include the IAB3 node  802 - 803 , an IAB2 node  810  having an IAB2-MT and an IAB2-DU, a Donor2-DU  812 , and the Donor1-CU  808 . 
     Accordingly, backhaul information may be transmitted over two paths to provide robustness and load balancing. The inter-donor topological redundancy may be based on the IAB-DU  802  having an F1 interface with a single donor-CU. The IAB3-DU  802  may be connected to the Donor1-CU  808  via an F1 interface, which may be split into the F1-C interface and the F1-U interface. Thus, the IAB3-DU  802  may have an F1 interface that includes two parts. For robustness, the F1-C part of the F1 interface between the IAB3-DU  802  and the Donor1-CU  808  may utilize different paths to transmit F1-C traffic in a more reliable manner between the IAB3-DU  802  and the Donor1-CU  808 . For load balancing, the F1-U part of the F1 interface may be utilized to decrease traffic transmitted via a first topology associated with Donor1-CU  808  by sending some of the traffic through a second topology associated with Donor2-CU  814 . For example, if the IAB3 node  802 - 803  that serves a first UE  816   a  and a second UE  818   a  initially overloads the first topology by transmitting all of the traffic for the first UE  816   a  and the second UE  818   a  over the first topology, the IAB3 node  802 - 803  may perform load balancing by transmitting further traffic for the second UE  818   a  over the second topology and continuing to transmit traffic for the first UE  816   a  over the first topology. 
     In the diagram  800 , the IAB3 node  802 - 803  may be an access IAB node that serves the first UE  816   a  and the second UE  818   a . In the diagram  850 , the IAB3 node  802 - 803  may be one or more hops away from a first UE  816   b  and a second UE  818   b , which may be served by an IAB4 node  820 . The IAB4 node  820  may forward traffic for the first UE  816   b  and the second UE  818   b  to the IAB3 node  802 - 803  to perform the load balancing based on topological redundancy. Thus, the first leg and the second leg of the backhaul link may be extended to further include the IAB4 node  820 . Accordingly, a first configuration associated with the diagram  800  may include the IAB3 node  802 - 803  being dual connected with two donor nodes, and a second configuration associated with the diagram  850  may include the IAB3 node  802 - 803  being a parent/ancestor node of the IAB4 node  820  and being dual connected with two donor nodes. Both CP-UP separation and topological redundancy may be performed for a dual connected IAB node and an ancestor/descendant IAB node of the dual connected IAB node. 
     In an example, the F1-C interface may include multiple hops and the F1-U interface may include a single hop. However, neither the access link nor the backhaul link is limited to single hop or multi-hop configurations. For performing CP-UP separation over multiple topologies, the IAB3-MT  803  may connect to Donor1-CU  808  via an access link of the first topology (e.g., communicate F1-C traffic using an access RLC channel of the link between the IAB3-MT  803  and IAB1  804 ), and the IAB3-MT  803  may connect to the Donor2-CU  814  via a backhaul link of the second topology (e.g., communicate F1-U traffic using a backhaul RLC channel of the link between the IAB3-MT  803  and IAB2  810 ). Given that CP-UP separation (e.g., such as described in connection with the diagrams  700 - 750 ) and topological redundancy techniques (e.g., as described in connection with the diagrams  800 - 850 ) may both be performed after the IAB3 node  802 - 803  becomes dual connected, the IAB3 node  802 - 803  may have to determine which technique to utilize. 
       FIGS. 9A-9C  illustrate example modes of multi-connectivity that include a dual connection  900 ,  920 , and  940  for an IAB node  902 . For example, CP-UP separation via a first mode of dual connection  900  for the IAB node  902  may be performed based on a first base station  904  (e.g., primary node) being a non-donor node and a Donor CU2  914  (e.g., secondary node) being a donor node. CP-UP separation via a second mode of dual connection  920  for the IAB node  902  may be performed based on a Donor CU1  912  (e.g., primary node) being a donor node and a second base station  906  (e.g., secondary node) being a non-donor node. Topological redundancy via a third mode of dual connection  940  for the IAB node  902  may be performed based on the Donor CU1  912  (e.g., primary node) and the Donor CU2  914  (e.g., secondary node) both being donor nodes. 
     If a base station is not configured to support IAB functionality, the base station may not be a donor node. If the base station is configured to support IAB functionality, but the base station determines to serve the MT of the IAB node  902  as a base station that does not assert the IAB functionality toward the IAB node  902 , the base station may likewise not be a donor node. However, if the base station asserts the IAB functionality towards the IAB node  902 , the base station may become a donor node. In some configurations, a same base station may be a donor node for a first IAB node and a non-donor node for a second IAB node (e.g., the base station may terminate the RRC connection with the MT of the second IAB node). A backhaul link that includes a BH RLC CH may be based on a single hop or multiple hops. 
     As any of the Donor CU1  912 , the Donor CU2  914 , or both, may be base stations that may assert donor functionality toward the IAB node  902 , CP-UP separation and topological redundancy procedures may have to be coordinated among the nodes. The IAB node  902  may initially connect to one of the second base station  906  or the Donor CU1  912  (e.g., via a Parent DU1  908 ), or may connect to the first base station  904  or the Donor CU2  914  (e.g., via a Parent DU2  910 ) at a first time, and the IAB node  902  may subsequently become connected to the other one of the second base station  906 /the Donor CU1  912  or the first base station  904 /the Donor CU2  914  at a second time to provide a dual connection. A first node that is initially connected to the IAB node  902  may determine whether CP-UP separation or topological redundancy is to be performed for the IAB node  902 . 
     The first base station  904  may determine whether to become a donor node (e.g., Donor CU1  912 ) for the IAB node  902  or whether to operate as a non-donor node (e.g., first base station  904 ). When the IAB node  902  connects via a second link to the second base station  906 /Donor CU2  914 , the first base station  904  may indicate to the second base station  906 /Donor CU2  914  whether the first base station  904  intends to operate as donor node (e.g., Donor CU1  912 ) or a non-donor node (e.g., first base station  904 ). In cases where an initial base station to connect with the IAB node  902  determines not to perform decision-making procedures, the initially-connected base station may handover the determination to another base station (e.g., the second base station  906 ) that may accept the decision-making tasks. Such procedures may occur when both the first base station  904  and the second base station  906  are capable of providing donor functionality for the IAB node  902 . 
     The first base station  904 /Donor CU1  912  may establish a first signaling connection with the IAB node  902  and may subsequently transmit a request for a second base station  906 /Donor CU2  914  to establish a second signaling connection between the IAB node  902  and the second base station  906 /Donor CU2  914 , where the second signaling connection may be maintained simultaneously with the first signaling connection. The second base station  906 /Donor CU2  914  may receive the request from the first base station  904 /Donor CU1  912  that has established the first signaling connection with the IAB node  902  to establish the second signaling connection between the IAB node  902  and the second base station  906 /Donor CU2  914 . Based on the simultaneous connections, the IAB node  902  may be dual connected such that the first base station  904 /Donor CU1  912  and the second base station  906 /Donor CU2  914  may coordinate with each other to determine whether the first base station  904 /Donor CU1  912  and/or the second base station  906 /Donor CU2  914  are to assert donor functionality toward the IAB node  902 . 
     The first signaling connection may be an RRC connection or an F1-C connection. The second signaling connection may also be an RRC connection or an F1-C connection. More specifically, the IAB node  902  may include the MT for the RRC connection and the DU for the F1-C connection. If the IAB node  902  has F1-C connections with both the first base station  904  and the second base station  906 , multiple logical IAB-DUs may be provided at the IAB node  902  in association with the different CUs of the first base station  904  and the second base station  906 . If one of the first base station  904  or the second base station  906  configures a BH RLC CH at the IAB-MT of the IAB node  902 , the one of the first base station  904  or the second base station  906  may be presumed to be an IAB donor for the IAB node  902 . 
     The simultaneous connections of the first base station  904 /Donor CU1  912  and the second base station  906 /Donor CU2  914  with the IAB node  902  may be based on NR-dual connectivity (NR-DC), multi-radio dual connectivity (MR-DC), dual active protocol stack (DAPS), or multi-MT connectivity. The DAPS may be utilized when a UE is handed over from the first base station  904  to another base station to reduce an interruption time for the UE. However, the UE may still continue to receive from both the first base station and the other base station at the same time (e.g., source base station and target base station), such that a master node and a secondary node may not be designated. Multi-MT connectivity may be utilized when the IAB node  902  includes two MTs, which may allow two UEs to independently connect to different locations, as opposed to an IAB node that includes one MT. In aspects, the second signaling connection with the IAB node  902  may be initiated by the IAB node  902 , where the first base station  904  and/or the second base station  906  may serve as an IAB donor (e.g., Donor CU1  912  and/or Donor CU2  914 ). That is, the first base station  904  and the second base station  906  may support IAB functionality and may or may not become an IAB donor, depending on whether the first base station  904  or the second base station  906  asserts the IAB donor functionality towards the IAB node  902 . As described herein, such determinations may be coordinated between the first base station  904  and the second base station  906 . 
     In a first aspect, asserting the IAB donor functionality may include terminating F1 connectivity with the IAB node  902 . In a second aspect, asserting the IAB donor functionality may include establishing a BH RLC CH at the IAB node  902 , as the BH RLC CH may be used for the IAB node  902  to relay traffic between child nodes and parent nodes (e.g., Parent DU1  908  and Parent DU2  910 ). An IAB donor may configure a BH RLC CH toward a parent node at an MT of the IAB node (e.g., based on RRC connectivity between the IAB-MT and the IAB-donor-CU). An IAB donor may also configure a BH RLC CH toward a child node at a DU of the IAB node or at an IAB-donor-DU (e.g., based on F1-C connectivity between the IAB-DU/IAB-donor-DU and the IAB-donor-CU). In a third aspect, asserting the IAB donor functionality may include providing a BAP configuration to the IAB node  902 . When the IAB node  902  is dual connected, quality of service (QoS) support as well as routing functionality for communicating with a donor node via the connections may be associated with a BAP layer. The IAB donor may configure the BAP layer. In a fourth aspect, asserting the IAB donor functionality may include providing a base station-DU cell resource configuration to the IAB node  902 . Because transmission at the DU may cause self-interference at the MT, the CU may provide a cell resource configuration for the IAB node  902  based on a half-duplex (HD) constraint of the IAB node  902 . In a fifth aspect, asserting the IAB donor functionality may include providing an IP configuration to the IAB node  902 , which may include one or more IP addresses or IP prefixes. For the IAB node  902  to be reachable from the IP network, an IP address may be selected so that when the IAB node  902  communicates with the CU via a first donor DU, the IP network may receive an IP address. If the IAB node  902  communicates with the CU via a second donor DU, the IP network may receive a different IP address. 
     In order to coordinate assertion of the IAB donor functionality, the first base station  904 /Donor CU1  912  may indicate to the second base station  906 /Donor CU2  914  whether the second base station  906 /Donor CU2  914  is to assert the IAB donor functionality towards the IAB node  902 . Additionally, or alternatively, the first base station  904 /Donor CU1  912  may indicate to the second base station  906 /Donor CU2  914  whether the first base station  904 /Donor CU1  912  is to assert the IAB donor functionality towards the IAB node  902 . In some configurations, both the first base station  904  station and the second base station  906  may be IAB donors that assert IAB functionality. For example, the first base station  904 /Donor CU1  912  may indicate to the second base station  906 /Donor CU2  914  that both the first base station  904  and the second base station  906  are to assert the IAB donor functionality towards the IAB node  902 . In aspects, the first base station  904 /Donor CU1  912  may indicate to the second base station  906 /Donor CU2  914  that the first base station  904  and/or the second base station  906  is to assert a subset of the IAB donor functionality towards the IAB node  902 . If the IAB node  902  is connected to two donors, a first donor (e.g., Donor CU1  912 ) may be for the HD constraint and a second donor (e.g., Donor CU2  914 ) may be for QoS support. Thus, a first IAB node may provide a resource configuration for all the IAB nodes in the topology, whereas a second IAB node may configure all BH RLC CHs and provide a corresponding BAP configuration. 
     The first base station  904 /Donor CU1  912  may indicate to the second base station  906 /Donor CU2  914  that the second base station  906 /Donor CU2  914  may obtain c-plane or u-plane connectivity with the IAB node  902  via the first base station  904 /Donor CU1  912  for the second base station  906 /Donor CU2  914  to assert the IAB donor functionality towards the IAB node  902 . In further configurations, the first base station  904 /Donor CU1  912  may indicate to the second base station  906 /Donor CU2  914  that the first base station  904 /Donor CU1  912  is to obtain c-plane or u-plane connectivity with the IAB node  902  via the second base station  906 /Donor CU2  914  for the first base station  904 /Donor CU1  912  to assert the IAB donor functionality towards the IAB node  902 . The second base station  906 /Donor CU2  914  may accept or reject the request of the first base station  904 /Donor CU1  912 . 
       FIG. 10  is a communication flow diagram  1000  illustrating communications between a first base station  1002 , a second base station  1004 , and an IAB node  1006 . At  1008 , the first base station  1002  may establish a first connection with the IAB node  1006 . The first connection established, at  1008 , may correspond to a first RRC connection or a first F1-C interface. At  1010 , the first base station  1002  may transmit a request to the second base station  1004  for the second base station  1004  to establish a second connection with the IAB node  1006 . At  1012 , the second base station  1004  may establish the second connection with the IAB node  1006  based on the request received, at  1010 , from the first base station  1002 . The second connection established, at  1012 , may correspond to a second RRC connection or a second F1-C interface. At  1014 , the second base station  1004  may transmit an acknowledgment/acceptance to the first base station  1002  indicating that the second base station  1004  has established the second connection with the IAB node  1006 . 
     At  1016 , the first base station  1002  may transmit an IAB donor status indication to the second base station  1004  indicative of whether the first base station  1002  and/or the second base station  1004  is to serve as an IAB donor for the IAB node  1006 . In aspects, the indication transmitted, at  1016 , may indicate whether the second base station  1004  is to establish a c-plane connection or a u-plane connection with the IAB node  1006 . At  1018 , the second base station  1004  may accept or reject the IAB donor status indication received, at  1016 , from the first base station  1002 . 
     At  1020 , the first base station  1002  may transmit, based on the acceptance or rejection received, at  1018 , from the second base station  1004 , an IAB donor indication to the IAB node  1006  indicative of whether the first base station  1002  and/or the second base station  1004  is to serve as an IAB donor for the IAB node  1006 . At  1022   a , the second base station  1004  may assert IAB donor functionality toward the IAB node  1006  if the second base station  1004  is to serve as the IAB donor for the IAB node  1006 . Additionally, or alternatively, at  1022   b , the first base station  1002  may assert the IAB donor functionality toward the IAB node  1006  if the first base station  1002  is to serve as the IAB donor for the IAB node  1006 . At  1024 , to serve as the IAB donor/assert the IAB donor functionality toward the IAB node  1006 , the first base station  1002  and/or the second base station  1004  may establish a backhaul RLC channel with the IAB node (e.g., based on  1024 ( 1 )), transmit a BAP configuration to the IAB node (e.g., based on  1024 ( 2 )), transmit a cell resource configuration for a DU to the IAB node (e.g., based on  1024 ( 3 )), transmit an IP configuration to the IAB node (e.g., based on  1024 ( 4 )), and/or terminate F1 connectivity with the IAB node (e.g., based on  1024 ( 5 )). 
       FIG. 11  is a flowchart  1100  of a method of wireless communication. The method may be performed by a base station, e.g., the first base station  1002 , which may include the memory  376  and which may be the entire first base station  1002  or a component of the first base station  1002 , such as the TX processor  316 , the RX processor  370 , and/or the controller/processor  375 . The method may enable the base station to coordinate donor functionality for an IAB node with a second base station. 
     At  1102 , the first base station may establish a first connection with an IAB node. For example, referring to  FIG. 10 , the first base station  1002  may establish, at  1008 , a first connection with the IAB node  1006 . The first connection may be established, e.g., by the establishment component  1740  of the apparatus  1702 . 
     At  1104 , the first base station may transmit, to a second base station, a request for the second base station to establish a second connection with the IAB node. For example, referring to  FIG. 10 , the first base station  1002  may transmit, at  1010 , a request for the second base station  1004  to establish a second connection with the IAB node  1006 . The first connection (e.g., established at  1008 ) may be based on at least one of a first RRC connection or a first F1-C interface, and the second connection (e.g., established at  1012 ) may be based on at least one of a second RRC connection or a second F1-C interface. The first connection (e.g., established at  1008 ) and the second connection (e.g., established at  1012 ) may provide DC for the IAB node  1006 . The DC may be associated with at least one of NR-DC, MR-DC, a DAPS, or multi-MT connectivity. The request may be transmitted, e.g., by the transmission component  1734  of the apparatus  1702 . 
     At  1106 , the first base station may indicate to the second base station, based on the second connection being established with the IAB node, that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. For example, referring to  FIG. 10 , the first base station  1002  may receive, at  1014 , an acknowledgement of the second connection established, at  1012 , by the second base station  1004 , and may transmit, at  1016 , to the second base station  1004 , an IAB donor status indication for the first base station  1002  and/or the second base station  1004  based on the received acknowledgement. The second connection may be indicated, e.g., by the indication component  1742  of the apparatus  1702 . 
       FIG. 12  is a flowchart  1200  of a method of wireless communication. The method may be performed by a base station, e.g., the first base station  1002 , which may include the memory  376  and which may be the entire first base station  1002  or a component of the first base station  1002 , such as the TX processor  316 , the RX processor  370 , and/or the controller/processor  375 . The method may enable the base station to coordinate donor functionality for an IAB node with a second base station. 
     At  1202 , the first base station may establish a first connection with an IAB node. For example, referring to  FIG. 10 , the first base station  1002  may establish, at  1008 , a first connection with the IAB node  1006 . The first connection may be established, e.g., by the establishment component  1740  of the apparatus  1702 . 
     At  1204 , the first base station may transmit, to a second base station, a request for the second base station to establish a second connection with the IAB node. For example, referring to  FIG. 10 , the first base station  1002  may transmit, at  1010 , a request for the second base station  1004  to establish a second connection with the IAB node  1006 . The first connection (e.g., established at  1008 ) may be based on at least one of a first RRC connection or a first F1-C interface, and the second connection (e.g., established at  1012 ) may be based on at least one of a second RRC connection or a second F1-C interface. The first connection (e.g., established at  1008 ) and the second connection (e.g., established at  1012 ) may provide DC for the IAB node  1006 . The DC may be associated with at least one of NR-DC, MR-DC, a DAPS, or multi-MT connectivity. The request may be transmitted, e.g., by the transmission component  1734  of the apparatus  1702 . 
     At  1206 , the first base station may indicate, explicitly or implicitly to the second base station, based on the second connection being established with the IAB node, that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. For example, referring to  FIG. 10 , the first base station  1002  may receive, at  1014 , an acknowledgement of the second connection established, at  1012 , by the second base station  1004 , and may transmit, at  1016 , to the second base station  1004 , an IAB donor status indication for the first base station  1002  and/or the second base station  1004  based on the received acknowledgement. The second connection may be indicated, e.g., by the indication component  1742  of the apparatus  1702 . 
     If the first base station (e.g., master node) determines that the second base station (e.g., secondary node) is to be an F1-terminating donor node for the IAB node, the first base station may explicitly signal a corresponding request/indication to the second base station. For example, the first base station may request the second base station to locate IP addresses and establish F1 connectivity with the IAB node. Alternatively, if the first base station determines to become the F1-terminating donor node for the IAB node, the first base station does not have to explicitly signal such information to the second base station. Instead, the first base station may transmit an indication to the second base station for offloading traffic to the second base station (e.g., based on topological redundancy), or for using a communication path between the IAB node and the second base station as an access link (e.g., based on CP-UP separation), where the indication may implicitly indicate to the second base station that the first base station has determined to become the F1-terminating donor node for the IAB node. 
     The first base station  1002  may indicate, at  1016 , to the second base station  1004  that the second base station  1004  is to serve as the IAB donor for the IAB node  1006 . In some configurations, the first base station  1002  may indicate to the second base station  1004  that the second base station  1004  is to provide a subset of IAB donor functionality for the IAB node  1006 . The indication, at  1016 , to the second base station  1004  may further indicate that the second base station  1004  is to establish at least one of a c-plane connection or a u-plane connection with the IAB node  1006  via the first base station  1002  for serving as the IAB donor to the IAB node  1006 , the c-plane connection being established in association with a CP-UP separation procedure, the u-plane connection being established in association with a topological redundancy procedure. Alternatively, the first base station  1002  may indicate, at  1016 , to the second base station  1004  that the first base station  1002  is to serve as the IAB donor for the IAB node  1006 . The indication, at  1016 , to the second base station  1004  may further indicate that the first base station  1002  is to establish at least one of a c-plane connection or a u-plane connection with the IAB node  1006  via the second base station  1004  for serving as the IAB donor to the IAB node  1006 . In further aspects, the first base station  1002  may indicate, at  1016 , to the second base station  1004  that the first base station  1002  and the second base station  1004  are to serve as IAB donors for the IAB node  1006 . 
     At  1208 , the first base station may indicate IAB donor functionality to the IAB node when the first base station indicates to the second base station that the first base station will serve as the IAB donor for the IAB node. For example, referring to  FIG. 10 , the first base station  1002  may indicate, at  1022   b , an IAB donor functionality assertion to the IAB node  1006  when the IAB donor status indication transmitted, at  1016 , indicates that the second base station  1004  is to serve as the IAB donor for the IAB node  1006 . The IAB donor functionality may be indicated, e.g., by the indication component  1742  of the apparatus  1702 . 
     At  1210 , to serve as the IAB donor for the IAB node the first base station may at least one of: establish a backhaul RLC channel with the IAB node, transmit a BAP configuration to the IAB node, transmit a cell resource configuration for a DU to the IAB node, transmit an IP configuration to the IAB node, or terminate F1 connectivity with the IAB node. For example, referring to  FIG. 10 , to indicate the IAB donor functionality/serve as the IAB donor for the IAB node  1006 , the first base station  1002  may, at  1024 , (1) establish a backhaul RLC channel with the IAB node, (2) transmit a BAP configuration to the IAB node, (3) transmit a cell resource configuration for a DU to the IAB node, (4) transmit an IP configuration to the IAB node, and/or (5) terminate F1 connectivity with the IAB node. Serving as the IAB donor may be performed, e.g., by the establishment component  1740 , the termination component  1744 , and/or the transmission component  1734  of the apparatus  1702 . 
     At  1212 , the first base station may receive, from the second base station, a response that indicates whether the at least one of the first base station or the second base station is to serve as the IAB donor for the IAB node. For example, referring to  FIG. 10 , the first base station  1002  may receive, at  1018 , and acceptance or rejection to the IAB donor status indication from the second base station  1004 . The response may be received, e.g., by the reception component  1730  of the apparatus  1702 . 
       FIG. 13  is a flowchart  1300  of a method of wireless communication. The method may be performed by a base station, e.g., the second base station  1004 , which may include the memory  376  and which may be the entire second base station  1004  or a component of the second base station  1004 , such as the TX processor  316 , the RX processor  370 , and/or the controller/processor  375 . The method may enable the base station to coordinate donor functionality for an IAB node with a second base station. 
     At  1302 , the second base station may receive, from a first base station having a first connection with an IAB node, a request for the second base station to establish a second connection with the IAB node. For example, referring to  FIG. 10 , the second base station  1004  may receive, at  1010 , a request from the first base station  1002  including the first connection established, at  1008 , with the IAB node  1006 , the request being for the second base station  1004  to establish a second connection with the IAB node  1006 . The first connection (e.g., established at  1008 ) may be based on at least one of a first RRC connection or a first F1-C interface, and the second connection (e.g., established at  1012 ) may be based on at least one of a second RRC connection or a second F1-C interface. The first connection (e.g., established at  1008 ) and the second connection (e.g., established at  1012 ) may provide DC for the IAB node  1006 , the DC associated with at least one of NR-DC, MR-DC, a DAPS, or multi-MT connectivity. The request may be received, e.g., by the reception component  1830  of the apparatus  1802 . 
     At  1304 , the second base station may receive from the first base station, based on the second connection being established with the IAB node, an indication that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. For example, referring to  FIG. 10 , the second base station  1004  may receive, at  1016 , an IAB donor status indication for the first base station  1002  and/or the second base station  1004  based an acknowledgment of the second connection transmitted, at  1014 , from the second base station  1004  to the first base station  1002 . The indication may be received, e.g., by the reception component  1830  of the apparatus  1802 . 
     At  1306 , the second base station may accept or reject the indication received from the first base station that the at least one of the first base station or the second base station is to serve as the IAB donor for the IAB node. For example, referring to  FIG. 10 , the second base station  1004  may transmit, at  1018 , an acceptance or rejection to the IAB donor status indication received, at  1016 , from the first base station  1002  indicating that the first base station  1002  and/or the second base station  1004  is to serve as the IAB donor for the IAB node  1006 . The indication may be accepted or rejected, e.g., by the acceptance-rejection component  1840  of the apparatus  1802 . 
       FIG. 14  is a flowchart  1400  of a method of wireless communication. The method may be performed by a base station, e.g., the second base station  1004 , which may include the memory  376  and which may be the entire second base station  1004  or a component of the second base station  1004 , such as the TX processor  316 , the RX processor  370 , and/or the controller/processor  375 . The method may enable the base station to coordinate donor functionality for an IAB node with a second base station. 
     At  1402 , the second base station may receive, from a first base station having a first connection with an IAB node, a request for the second base station to establish a second connection with the IAB node. For example, referring to  FIG. 10 , the second base station  1004  may receive, at  1010 , a request from the first base station  1002  including the first connection established, at  1008 , with the IAB node  1006 , the request being for the second base station  1004  to establish a second connection with the IAB node  1006 . The first connection (e.g., established at  1008 ) may be based on at least one of a first RRC connection or a first F1-C interface, and the second connection (e.g., established at  1012 ) may be based on at least one of a second RRC connection or a second F1-C interface. The first connection (e.g., established at  1008 ) and the second connection (e.g., established at  1012 ) may provide DC for the IAB node  1006 , the DC associated with at least one of NR-DC, MR-DC, a DAPS, or multi-MT connectivity. The request may be received, e.g., by the reception component  1830  of the apparatus  1802 . 
     At  1404 , the second base station may receive, explicitly or implicitly from the first base station, based on the second connection being established with the IAB node, an indication that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. For example, referring to  FIG. 10 , the second base station  1004  may receive, at  1016 , an IAB donor status indication for the first base station  1002  and/or the second base station  1004  based an acknowledgment of the second connection transmitted, at  1014 , from the second base station  1004  to the first base station  1002 . The indication may be received, e.g., by the reception component  1830  of the apparatus  1802 . 
     If the first base station (e.g., master node) determines that the second base station (e.g., secondary node) is to be an F1-terminating donor node for the IAB node, the first base station may explicitly signal a corresponding request/indication to the second base station. For example, the first base station may request the second base station to location IP addresses and establish F1 connectivity with the IAB node. Alternatively, if the first base station determines to become the F1-terminating donor node for the IAB node, the first base station does not have to explicitly signal such information to the second base station. Instead, the first base station may transmit an indication to the second base station for offloading traffic to the second base station (e.g., based on topological redundancy), or for using a communication path between the IAB node and the second base station as an access link (e.g., based on CP-UP separation), where the indication may implicitly indicate to the second base station that the first base station has determined to become the F1-terminating donor node for the IAB node. 
     The second base station  1004  may receive, at  1016 , the indication that the second base station  1004  is to serve as the IAB donor for the IAB node  1006 . In some configurations, the indication received, at  1016 , from the first base station  1002  may indicate that the second base station  1004  is to provide a subset of IAB donor functionality for the IAB node  1006 . The indication received, at  1016 , from the first base station  1002  may further indicate to the second base station  1004  that the second base station  1004  is to establish at least one of a c-plane connection or a u-plane connection with the IAB node  1006  via the first base station  1002  for serving as the IAB donor to the IAB node  1006 , the c-plane connection being established in association with a CP-UP separation procedure, the u-plane connection being established in association with a topological redundancy procedure. Alternatively, the second base station  1004  may receive, at  1016 , the indication from the first base station  1002  indicating that the first base station  1002  is to serve as the IAB donor for the IAB node  1006 . The indication received, at  1016 , from the first base station  1002  may further indicate that the first base station  1002  is to establish at least one of a c-plane connection or a u-plane connection with the IAB node  1006  via the second base station  1004  for serving as the IAB donor to the IAB node  1006 . In further aspects, the indication received, at  1016 , from the first base station  1002  may indicate that the first base station  1002  and the second base station  1004  are to serve as IAB donors for the IAB node  1006 . 
     At  1406 , the second base station may indicate IAB donor functionality to the IAB node when the second base station receives the indication that the second base station is to serve as the IAB donor for the IAB node. For example, referring to  FIG. 10 , the second base station  1004  may indicate, at  1022   a , an IAB donor functionality assertion to the IAB node  1006  when the IAB donor status indication received, at  1016 , indicates that the second base station  1004  is to serve as the IAB donor for the IAB node  1006 . The IAB donor functionality may be indicated, e.g., by the indication component  1844  of the apparatus  1802 . 
     At  1408 , to serve as the IAB donor for the IAB node the second base station may at least one of: establish a backhaul RLC channel with the IAB node, transmit a BAP configuration to the IAB node, transmit a cell resource configuration for a DU to the IAB node, transmit an IP configuration to the IAB node, or terminate F1 connectivity with the IAB node. For example, referring to  FIG. 10 , to indicate the IAB donor functionality/serve as the IAB donor for the IAB node  1006 , the second base station  1004  may, at  1024 , (1) establish a backhaul RLC channel with the IAB node, (2) transmit a BAP configuration to the IAB node, (3) transmit a cell resource configuration for a DU to the IAB node, (4) transmit an IP configuration to the IAB node, and/or (5) terminate F1 connectivity with the IAB node. Serving as the IAB donor may be performed, e.g., by the establishment component  1842 , the termination component  1846 , and/or the transmission component  1834  of the apparatus  1802 . 
     At  1410 , the second base station may accept or reject the indication received from the first base station that the at least one of the first base station or the second base station is to serve as the IAB donor for the IAB node. For example, referring to  FIG. 10 , the second base station  1004  may transmit, at  1018 , an acceptance or rejection to the IAB donor status indication received, at  1016 , from the first base station  1002  indicating that the first base station  1002  and/or the second base station  1004  is to serve as the IAB donor for the IAB node  1006 . The indication may be accepted or rejected, e.g., by the acceptance-rejection component  1840  of the apparatus  1802 . 
     At  1412 , to accept or reject the indication, the second base station may, transmit a response to the first base station that indicates whether the second base station will establish at least one of a c-plane connection or a u-plane connection with the IAB node via the first base station for serving as the IAB donor to the IAB node. For example, referring to  FIG. 10 , to accept or reject, at  1018 , the IAB donor status indication received, at  1016 , the second base station  1004  may include in the acceptance/rejection an indication of whether the second base station  1004  will establish the c-plane or u-plane connection with the IAB node  1006 . The response may be transmitted, e.g., by the transmission component  1834  and/or the acceptance-rejection component  1840  of the apparatus  1802 . 
     At  1414 , the second base station may establish, based on the request, the second connection with the IAB node. For example, referring to  FIG. 10 , the second base station  1004  may establish, at  1012 , the second connection with the IAB node  1006  based on the request received, at  1010 , for the second base station  1004  to establish the second connection with the IAB node  1006 . The second connection may be established, e.g., by the establishment component  1842  of the apparatus  1802 . 
       FIG. 15  is a flowchart  1500  of a method of wireless communication. The method may be performed by a base station/IAB node, e.g., the IAB node  1006 , which may include the memory  376  and which may be the entire IAB node  1006  or a component of the IAB node  1006 , such as the TX processor  316 , the RX processor  370 , and/or the controller/processor  375 . The method improves multi-connectivity for the IAB node. 
     At  1502 , the IAB node may establish a first connection with a first base station. For example, referring to  FIG. 10 , the IAB node  1006  may establish, at  1008 , a first connection with the first base station  1002 . The first connection may be established, e.g., by the first connection component  1940  of the apparatus  1902 . 
     At  1504 , the IAB node may establish a second connection with a second base station. For example, referring to  FIG. 10 , the IAB node  1006  may establish, at  1012 , a second connection with the second base station  1004 . The first connection (e.g., established at  1008 ) may be based on at least one of a first RRC connection or a first F1-C interface, and the second connection (e.g., established at  1012 ) may be based on at least one of a second RRC connection or a second F1-C interface. The first connection (e.g., established at  1008 ) and the second connection (e.g., established at  1012 ) may provide DC for the IAB node  1006 , the DC associated with at least one of NR-DC, MR-DC, a DAPS, or multi-MT connectivity. The second connection may be established, e.g., by the second connection component  1942  of the apparatus  1902 . 
     At  1506 , the IAB node may receive an indication, from the first base station or the second base station, indicating that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. For example, referring to  FIG. 10 , the IAB node  1006  may receive, at  1020 , an IAB donor indication for the first base station  1002  and/or the second base station  1004 . In some configurations, the IAB node  1006  may receive, at  1020 , the indication that the second base station  1004  is to provide a subset of IAB donor functionality for the IAB node  1006 . The IAB node  1006  may be served by an IAB donor based on at least one of a backhaul RLC channel established with the IAB node  1006 , a BAP configuration transmitted to the IAB node  1006 , a cell resource configuration for a DU transmitted to the IAB node  1006 , an IP configuration transmitted to the IAB node  1006 , and/or F1 connectivity being terminated with the IAB node  1006 . The IAB node  1006  may receive, at  1020 , the indication that the second base station  1004  is to serve as the IAB donor for the IAB node  1006 . Alternatively, the IAB node  1006  may receive, at  1020 , the indication that the first base station  1002  is to serve as the IAB donor for the IAB node  1006 . In further aspects, the IAB node  1006  may receive, at  1020 , the indication that the first base station  1002  and the second base station  1004  are to serve as IAB donors for the IAB node  1006 . The indication may be received, e.g., by the reception component  1930  and/or the indication component  1944  of the apparatus  1902 . 
       FIG. 16  is a flowchart  1600  of a method of wireless communication. The method may be performed by a base station/IAB node, e.g., the IAB node  1006 , which may include the memory  376  and which may be the entire IAB node  1006  or a component of the IAB node  1006 , such as the TX processor  316 , the RX processor  370 , and/or the controller/processor  375 . The method improves multi-connectivity for the IAB node. 
     At  1602 , the IAB node may establish a first connection with a first base station. For example, referring to  FIG. 10 , the IAB node  1006  may establish, at  1008 , a first connection with the first base station  1002 . The first connection may be established, e.g., by the first connection component  1940  of the apparatus  1902 . 
     At  1604 , the IAB node may establish a second connection with a second base station. For example, referring to  FIG. 10 , the IAB node  1006  may establish, at  1012 , a second connection with the second base station  1004 . The first connection (e.g., established at  1008 ) may be based on at least one of a first RRC connection or a first F1-C interface, and the second connection (e.g., established at  1012 ) may be based on at least one of a second RRC connection or a second F1-C interface. The first connection (e.g., established at  1008 ) and the second connection (e.g., established at  1012 ) may provide DC for the IAB node  1006 , the DC associated with at least one of NR-DC, MR-DC, a DAPS, or multi-MT connectivity. The second connection may be established, e.g., by the second connection component  1942  of the apparatus  1902 . 
     At  1606 , the IAB node may receive an indication, from the first base station or the second base station, that implicitly indicates at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. For example, referring to  FIG. 10 , the IAB node  1006  may receive, at  1020 , an IAB donor indication for the first base station  1002  and/or the second base station  1004 . If the IAB node establishes NR-DC with the first base station (e.g., master node) and the second base station (e.g., secondary node) before F1 connectivity is established with the IAB node, the IAB node may determine whether the first base station or the second base station is serving as the F1-terminating donor node based on which of the first base station or the second base station provides a BAP configuration and/or IP address(es) to the IAB node. That is, receiving the BAP configuration and/or the IP address(es) from a particular base station may implicitly indicate to the IAB node that the particular base station is serving as the F1-terminating donor node. 
     In some configurations, the IAB node  1006  may receive, at  1020 , the indication that the second base station  1004  is to provide a subset of IAB donor functionality for the IAB node  1006 . The IAB node  1006  may be served by an IAB donor based on at least one of a backhaul RLC channel established with the IAB node  1006 , a BAP configuration transmitted to the IAB node  1006 , a cell resource configuration for a DU transmitted to the IAB node  1006 , an IP configuration transmitted to the IAB node  1006 , and/or F1 connectivity being terminated with the IAB node  1006 . The IAB node  1006  may receive, at  1020 , the indication that the second base station  1004  is to serve as the IAB donor for the IAB node  1006 . Alternatively, the IAB node  1006  may receive, at  1020 , the indication that the first base station  1002  is to serve as the IAB donor for the IAB node  1006 . In further aspects, the IAB node  1006  may receive, at  1020 , the indication that the first base station  1002  and the second base station  1004  are to serve as IAB donors for the IAB node  1006 . The indication may be received, e.g., by the reception component  1930  and/or the indication component  1944  of the apparatus  1902 . 
     At  1608 , the IAB node may receive, from the first base station or the second base station, an assertion for at least a subset of IAB donor functionality. For example, referring to  FIG. 10 , the IAB node  1006  may receive, at  1022   a , a first IAB donor functionality assertion from the second base station  1004 , and/or the IAB node  1006  may receive, at  1022   b , a second IAB donor functionality assertion from the first base station  1002 . The assertion may be received, e.g., by the reception component  1930  of the apparatus  1902 . 
       FIG. 17  is a diagram  1700  illustrating an example of a hardware implementation for an apparatus  1702 . The apparatus  1702  is a BS and includes a baseband unit  1704 . The baseband unit  1704  may communicate through a cellular RF transceiver  1722  with the IAB node  103 , a second base station  102 / 180 , and/or UE  104 . The baseband unit  1704  may include a computer-readable medium/memory. The baseband unit  1704  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory. The software, when executed by the baseband unit  1704 , causes the baseband unit  1704  to perform the various functions described supra. The computer-readable medium/memory may also be used for storing data that is manipulated by the baseband unit  1704  when executing software. The baseband unit  1704  further includes a reception component  1730 , a communication manager  1732 , and a transmission component  1734 . The communication manager  1732  includes the one or more illustrated components. The components within the communication manager  1732  may be stored in the computer-readable medium/memory and/or configured as hardware within the baseband unit  1704 . The baseband unit  1704  may be a component of the first wireless device  310  and may include the memory  376  and/or at least one of the TX processor  316 , the RX processor  370 , and the controller/processor  375 . 
     The communication manager  1732  includes an establishment component  1740  that is configured, e.g., as described in connection with  1102 ,  1202 , and  1210 , to establish a first connection with an IAB node  103 ; and to establish a backhaul RLC channel with the IAB node  103 . The communication manager  1732  further includes an indication component  1742  that is configured, e.g., as described in connection with  1106 ,  1206 , and  1208 , to indicate (e.g., explicitly or implicitly) to the second base station  102 / 180 , based on the second connection being established with the IAB node  103 , that at least one of the first base station (e.g., the apparatus  1702 ) or the second base station is to serve as an IAB donor for the IAB node; and to indicate IAB donor functionality to the IAB node when the apparatus  1702  indicates to the second base station that the first base station will serve as the IAB donor for the IAB node. The communication manager  1732  further includes a termination component  1744  that is configured, e.g., as described in connection with  1210 , to terminate F1 connectivity with the IAB node  103 . 
     The reception component  1730  is configured, e.g., as described in connection with  1212 , to receive, from the second base station  102 / 180 , a response that indicates whether the at least one of the first base station (e.g., the apparatus  1702 ) or the second base station is to serve as the IAB donor for the IAB node. The transmission component  1734  may be configured, e.g., as described in connection with  1104 ,  1204 , and  1210 , to transmit, to a second base station, a request for the second base station to establish a second connection with the IAB node; transmit a BAP configuration to the IAB node; transmit a cell resource configuration for a DU to the IAB node; and transmit an IP configuration to the IAB node. 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of  FIGS. 11-12 . As such, each block in the aforementioned flowcharts of  FIGS. 11-12  may be performed by a component and the apparatus may include one or more of those components. The components may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof. 
     In one configuration, the apparatus  1702 , and in particular the baseband unit  1704 , includes means for establishing a first connection with an IAB node; means for transmitting, to a second base station, a request for the second base station to establish a second connection with the IAB node; and means for indicating to the second base station, based on the second connection being established with the IAB node, that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. The apparatus  1702  further includes means for indicating IAB donor functionality to the IAB node. The apparatus  1702  further includes means for establishing a backhaul RLC channel with the IAB node; means for transmitting a BAP configuration to the IAB node; means for transmitting a cell resource configuration for a DU to the IAB node; means for transmitting an IP configuration to the IAB node; and means for terminating F1 connectivity with the IAB node. The apparatus  1702  further includes means for receiving, from the second base station, a response that indicates whether the at least one of the first base station or the second base station is to serve as the IAB donor for the IAB node. The aforementioned means may be one or more of the aforementioned components of the apparatus  1702  configured to perform the functions recited by the aforementioned means. As described supra, the apparatus  1702  may include the TX Processor  316 , the RX Processor  370 , and the controller/processor  375 . As such, in one configuration, the aforementioned means may be the TX Processor  316 , the RX Processor  370 , and the controller/processor  375  configured to perform the functions recited by the aforementioned means. 
       FIG. 18  is a diagram  1800  illustrating an example of a hardware implementation for an apparatus  1802 . The apparatus  1802  is a BS and includes a baseband unit  1804 . The baseband unit  1804  may communicate through a cellular RF transceiver  1822  with the base station  102 / 180 , the IAB node  103 , and/or the UE  104 . The baseband unit  1804  may include a computer-readable medium/memory. The baseband unit  1804  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory. The software, when executed by the baseband unit  1804 , causes the baseband unit  1804  to perform the various functions described supra. The computer-readable medium/memory may also be used for storing data that is manipulated by the baseband unit  1804  when executing software. The baseband unit  1804  further includes a reception component  1830 , a communication manager  1832 , and a transmission component  1834 . The communication manager  1832  includes the one or more illustrated components. The components within the communication manager  1832  may be stored in the computer-readable medium/memory and/or configured as hardware within the baseband unit  1804 . The baseband unit  1804  may be a component of the first wireless device  310  and may include the memory  376  and/or at least one of the TX processor  316 , the RX processor  370 , and the controller/processor  375 . 
     The communication manager  1832  includes an acceptance-rejection component  1840  that is configured, e.g., as described in connection with  1306  and  1410 , to accept or reject the indication received from the first base station that the at least one of the first base station or the second base station (e.g., the apparatus  1802 ) is to serve as the IAB donor for the IAB node  103 . The communication manager  1832  further includes an establishment component  1842  that is configured, e.g., as described in connection with  1414  and  1408 , to establish, based on the request, the second connection with the IAB node  103 ; and to establish a backhaul RLC channel with the IAB node  103 . The communication manager  1832  further includes an indication component  1844  that is configured, e.g., as described in connection with  1406 , to indicate IAB donor functionality to the IAB node when the second base station (e.g., the apparatus  1802 ) receives the indication that the second base station is to serve as the IAB donor for the IAB node. The communication manager  1832  further includes a termination component  1846  that is configured, e.g., as described in connection with  1408 , to terminate F1 connectivity with the IAB node. 
     The reception component  1830  is configured, e.g., as described in connection with  1302 ,  1304 ,  1402  and  1404 , to receive, from a first base station having a first connection with an IAB node, a request for the second base station (e.g., the apparatus  1802 ) to establish a second connection with the IAB node; and to receive (e.g., explicitly or implicitly) from the first base station, based on the second connection being established with the IAB node  103 , an indication that at least one of the first base station or the second base station (e.g., the apparatus  1802 ) is to serve as an IAB donor for the IAB node  103 . The transmission component  1834  is configured, e.g., as described in connection with  1408  and  1412 , to transmit a BAP configuration to the IAB node  103 ; to transmit a cell resource configuration for a DU to the IAB node  103 ; to transmit an IP configuration to the IAB node  103 ; and to transmit a response to the first base station that indicates whether the second base station (e.g., the apparatus  1802 ) will establish at least one of a c-plane connection or a u-plane connection with the IAB node  103  via the first base station for serving as the IAB donor to the IAB node  103 . 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of  FIGS. 13-14 . As such, each block in the aforementioned flowcharts of  FIGS. 13-14  may be performed by a component and the apparatus may include one or more of those components. The components may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof. 
     In one configuration, the apparatus  1802 , and in particular the baseband unit  1804 , includes means for receiving, from a first base station having a first connection with an IAB node, a request for the second base station to establish a second connection with the IAB node; means for receiving from the first base station, based on the second connection being established with the IAB node, an indication that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node; and means for accepting or rejecting the indication received from the first base station that the at least one of the first base station or the second base station is to serve as the IAB donor for the IAB node. The means for accepting or rejecting the indication is further configured to transmit a response to the first base station that indicates whether the second base station will establish at least one of a c-plane connection or a u-plane connection with the IAB node via the first base station for serving as the IAB donor to the IAB node. The apparatus  1802  further includes means for establishing, based on the request, the second connection with the IAB node. The apparatus  1802  further includes means for indicating IAB donor functionality to the IAB node when the second base station is to serve as the IAB donor for the IAB node. The apparatus  1802  further includes means for establishing a backhaul RLC channel with the IAB node; means for transmitting a BAP configuration to the IAB node; means for transmitting a cell resource configuration for a DU to the IAB node; means for transmitting an IP configuration to the IAB node; and means for terminating F1 connectivity with the IAB node. 
     The aforementioned means may be one or more of the aforementioned components of the apparatus  1802  configured to perform the functions recited by the aforementioned means. As described supra, the apparatus  1802  may include the TX Processor  316 , the RX Processor  370 , and the controller/processor  375 . As such, in one configuration, the aforementioned means may be the TX Processor  316 , the RX Processor  370 , and the controller/processor  375  configured to perform the functions recited by the aforementioned means. 
       FIG. 19  is a diagram  1900  illustrating an example of a hardware implementation for an apparatus  1902 . The apparatus  1902  is an IAB node and includes a baseband unit  1904 . The baseband unit  1904  may communicate through a cellular RF transceiver  1922  with a first and second base station  102 / 180 , another IAB node  103 , and/or the UE  104 . The baseband unit  1904  may include a computer-readable medium/memory. The baseband unit  1904  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory. The software, when executed by the baseband unit  1904 , causes the baseband unit  1904  to perform the various functions described supra. The computer-readable medium/memory may also be used for storing data that is manipulated by the baseband unit  1904  when executing software. The baseband unit  1904  further includes a reception component  1930 , a communication manager  1932 , and a transmission component  1934 . The communication manager  1932  includes the one or more illustrated components. The components within the communication manager  1932  may be stored in the computer-readable medium/memory and/or configured as hardware within the baseband unit  1904 . The baseband unit  1904  may be a component of the first wireless device  310  or the second wireless device  350  and may include the memory  360  or  376  and/or at least one of the TX processor  316  or  368 , the RX processor  356  or  370 , and the controller/processor  359  or  375 . 
     The communication manager  1932  includes a first connection component  1940  that is configured, e.g., as described in connection with  1502  and  1602 , to establish a first connection with a first base station; and a second connection component  1942  configured to establish a second connection with a second base station, e.g., as described in connection with  1504  and  1604 . The communication manager  1932  includes an indication component  1944  that is configured, e.g., as described in connection with  1506 ,  1606 , and  1608 , to receive, via the reception component  1930 , an indication, from the first base station or the second base station, indicating (e.g., implicitly) that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node; and to receive, from the first base station or the second base station, an assertion for at least a subset of IAB donor functionality. 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of  FIGS. 15-16 . As such, each block in the aforementioned flowcharts of  FIGS. 15-16  may be performed by a component and the apparatus may include one or more of those components. The components may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof. 
     In one configuration, the apparatus  1902 , and in particular the baseband unit  1904 , includes means for establishing a first connection with a first base station; means for establishing a second connection with a second base station; and means for receiving an indication, from the first base station, indicating that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. The apparatus  1902  further includes means for receiving, from the first base station or the second base station, an assertion for at least a subset of IAB donor functionality. 
     The aforementioned means may be one or more of the aforementioned components of the apparatus  1902  configured to perform the functions recited by the aforementioned means. As described supra, the apparatus  1902  may include the TX Processor  316 , the RX Processor  370 , and the controller/processor  375 . As such, in one configuration, the aforementioned means may be the TX Processor  316 , the RX Processor  370 , and the controller/processor  375  configured to perform the functions recited by the aforementioned means. 
     It is understood that the specific order or hierarchy of blocks in the processes/flowcharts disclosed is an illustration of example approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes/flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not meant to be limited to the specific order or hierarchy presented. 
     The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Terms such as “if,” “when,” and “while” should be interpreted to mean “under the condition that” rather than imply an immediate temporal relationship or reaction. That is, these phrases, e.g., “when,” do not imply an immediate action in response to or during the occurrence of an action, but simply imply that if a condition is met then an action will occur, but without requiring a specific or immediate time constraint for the action to occur. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words “module,” “mechanism,” “element,” “device,” and the like may not be a substitute for the word “means.” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.” 
     The following aspects are illustrative only and may be combined with other aspects or teachings described herein, without limitation. 
     Aspect 1 is a method of wireless communication at a first base station, including: 
     establishing a first connection with an IAB node; transmitting, to a second base station, a request for the second base station to establish a second connection with the IAB node; and indicating to the second base station, based on the second connection being established with the IAB node, that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. 
     Aspect 2 may be combined with aspect 1 and includes that the first connection is based on at least one of a first RRC connection or a first F1-C interface, and the second connection is based on at least one of a second RRC connection or a second F1-C interface. 
     Aspect 3 may be combined with any of aspects 1-2 and includes that the first connection and the second connection provide DC for the IAB node, the DC associated with at least one of NR-DC, MR-DC, a DAPS, or multi-MT connectivity. 
     Aspect 4 may be combined with any of aspects 1-3 and includes that the first base station indicates to the second base station that the first base station will serve as the IAB donor for the IAB node, the aspect further including indicating IAB donor functionality to the IAB node. 
     Aspect 5 may be combined with any of aspects 1-4 and includes that serving as the IAB donor for the IAB node includes at least one of: establishing a backhaul RLC channel with the IAB node, transmitting a BAP configuration to the IAB node, transmitting a cell resource configuration for a DU to the IAB node, transmitting an IP configuration to the IAB node, or terminating F1 connectivity with the IAB node. 
     Aspect 6 may be combined with any of aspects 1-5 and includes that the first base station indicates to the second base station that the second base station is to serve as the IAB donor for the IAB node. 
     Aspect 7 may be combined with any of aspects 1-6 and includes that the indication to the second base station further indicates that the second base station is to establish at least one of a c-plane connection or a u-plane connection with the IAB node via the first base station for serving as the IAB donor to the IAB node. 
     Aspect 8 may be combined with any of aspects 1-5 and includes that the first base station indicates to the second base station that the first base station is to serve as the IAB donor for the IAB node. 
     Aspect 9 may be combined with any of aspects 1-5 or 8 and includes that the indication to the second base station further indicates that the first base station is to establish at least one of a c-plane connection or a u-plane connection with the IAB node via the second base station for serving as the IAB donor to the IAB node, the c-plane connection being established in association with a control-plane-user-plane (CP-UP) separation procedure, the u-plane connection being established in association with a topological redundancy procedure. 
     Aspect 10 may be combined with any of aspects 1-9 and further includes receiving, from the second base station, a response that indicates whether the at least one of the first base station or the second base station is to serve as the IAB donor for the IAB node. 
     Aspect 11 may be combined with any of aspects 1-10 and includes that the first base station indicates to the second base station that the first base station and the second base station are to serve as IAB donors for the IAB node. 
     Aspect 12 may be combined with any of aspects 1-3 or 5-11 and includes that the first base station indicates to the second base station that the second base station is to provide a subset of IAB donor functionality for the IAB node. 
     Aspect 13 is a method of wireless communication at a second base station, including: receiving, from a first base station having a first connection with an IAB node, a request for the second base station to establish a second connection with the IAB node; receiving, from the first base station, based on the second connection being established with the IAB node, an indication that at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node; and accepting or rejecting the indication received from the first base station that the at least one of the first base station or the second base station is to serve as the IAB donor for the IAB node. 
     Aspect 14 may be combined with aspect 13 and further includes establishing, based on the request, the second connection with the IAB node. 
     Aspect 15 may be combined with any of aspects 13-14 and includes that the first connection is based on at least one of a first RRC connection or a first F1-C interface, and the second connection is based on at least one of a second RRC connection or a second F1-C interface. 
     Aspect 16 may be combined with any of aspects 13-15 and includes that the first connection and the second connection provide DC for the IAB node, the DC associated with at least one of NR-DC, MR-DC, a DAPS, or multi-MT connectivity. 
     Aspect 17 may be combined with any of aspects 13-16 and includes that the second base station receives the indication that the second base station is to serve as the IAB donor for the IAB node, the aspect further including: indicating IAB donor functionality to the IAB node when the second base station is to serve as the IAB donor for the IAB node. 
     Aspect 18 may be combined with any of aspects 13-17 and includes that serving as the IAB donor for the IAB node includes at least one of: establishing a backhaul RLC channel with the IAB node, transmitting a BAP configuration to the IAB node, transmitting a cell resource configuration for a DU to the IAB node, transmitting an IP configuration to the IAB node, or terminating F1 connectivity with the IAB node. 
     Aspect 19 may be combined with any of aspects 13-18 and includes that the second base station receives the indication that the second base station is to serve as the IAB donor for the IAB node. 
     Aspect 20 may be combined with any of aspects 13-19 and includes that the indication received from the first base station further indicates to the second base station that the second base station is to establish at least one of a c-plane connection or a u-plane connection with the IAB node via the first base station for serving as the IAB donor to the IAB node. 
     Aspect 21 may be combined with any of aspects 13-18 and includes that the second base station receives the indication from the first base station indicating that the first base station is to serve as the IAB donor for the IAB node. 
     Aspect 22 may be combined with any of aspects 13-18 or 21 and includes that the indication received from the first base station further indicates that the first base station is to establish at least one of a c-plane connection or a u-plane connection with the IAB node via the second base station for serving as the IAB donor to the IAB node, the c-plane connection being established in association with a control-plane-user-plane (CP-UP) separation procedure, the u-plane connection being established in association with a topological redundancy procedure. 
     Aspect 23 may be combined with any of aspects 13-22 and includes that accepting or rejecting the indication further includes transmitting a response to the first base station that indicates whether the second base station will establish at least one of a c-plane connection or a u-plane connection with the IAB node via the first base station for serving as the IAB donor to the IAB node. 
     Aspect 24 may be combined with any of aspects 13-23 and includes that the indication received from the first base station indicates that the first base station and the second base station are to serve as IAB donors for the IAB node. 
     Aspect 25 may be combined with any of aspects 13-16 or 18-24 and includes that the indication received from the first base station indicates that the second base station is to provide a subset of IAB donor functionality for the IAB node. 
     Aspect 26 is a method of wireless communication at an IAB node, including: establishing a first connection with a first base station; establishing a second connection with a second base station; and receiving an indication, from the first base station or the second base station, that indicates at least one of the first base station or the second base station is to serve as an IAB donor for the IAB node. 
     Aspect 27 may be combined with aspect 26 and includes that the first connection is based on at least one of a first RRC connection or a first F1-C interface, and the second connection is based on at least one of a second RRC connection or a second F1-C interface. 
     Aspect 28 may be combined with any of aspects 26-27 and includes that the first connection and the second connection provide DC for the IAB node, the DC associated with at least one of NR-DC, MR-DC, a DAPS, or multi-MT connectivity. 
     Aspect 29 may be combined with any of aspects 26-28 and further includes receiving, from the first base station or the second base station, an assertion for at least a subset of IAB donor functionality. 
     Aspect 30 may be combined with any of aspects 26-29 and includes that serving as the IAB donor for the IAB node includes at least one of: establishing a backhaul RLC channel with the IAB node, transmitting a BAP configuration to the IAB node, transmitting a cell resource configuration for a DU to the IAB node, transmitting an IP configuration to the IAB node, or terminating F1 connectivity with the IAB node. 
     Aspect 31 may be combined with any of aspects 26-30 and includes that the IAB node receives the indication that the second base station is to serve as the IAB donor for the IAB node. 
     Aspect 32 may be combined with any of aspects 26-30 and includes that the IAB node receives the indication that the first base station is to serve as the IAB donor for the IAB node. 
     Aspect 33 may be combined with any of aspects 26-32 and includes that the IAB node receives the indication that the first base station and the second base station are to serve as IAB donors for the IAB node. 
     Aspect 34 may be combined with any of aspects 26-33 and includes that the IAB node receives the indication that the second base station is to provide a subset of IAB donor functionality for the IAB node. 
     Aspect 35 is an apparatus for wireless communication at a first base station including at least one processor coupled to a memory and configured to implement a method as in any of aspects 1-12. 
     Aspect 36 is an apparatus for wireless communication at a second base station including at least one processor coupled to a memory and configured to implement a method as in any of aspects 13-25. 
     Aspect 37 is an apparatus for wireless communication at an IAB node including at least one processor coupled to a memory and configured to implement a method as in any of aspects 26-34. 
     Aspect 38 is an apparatus for wireless communication at a first base station including means for implementing a method as in any of aspects 1-12. 
     Aspect 39 is an apparatus for wireless communication at a second base station including means for implementing a method as in any of aspects 14-25. 
     Aspect 40 is an apparatus for wireless communication at an IAB node including means for implementing a method as in any of aspects 27-34. 
     Aspect 41 is a computer-readable medium storing computer executable code, where the code when executed by a processor causes the processor to implement a method as in any of aspects 1-12. 
     Aspect 42 is a computer-readable medium storing computer executable code, where the code when executed by a processor causes the processor to implement a method as in any of aspects 14-25. 
     Aspect 43 is a computer-readable medium storing computer executable code, where the code when executed by a processor causes the processor to implement a method as in any of aspects 27-34.