Patent Description:
The present disclosure relates to wireless communication and more particularly, to techniques for inter-gNB migration of a distributed units.

Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single-carrier frequency division multiple access (SC-FDMA) systems.

For example, a fifth generation (<NUM>) wireless communications technology (which can be referred to as new radio (NR)) is envisaged to expand and support diverse usage scenarios and applications with respect to current mobile network generations. In an aspect, <NUM> communications technology can include: enhanced mobile broadband addressing human-centric use cases for access to multimedia content, services and data; ultra-reliable-low latency communications (URLLC) with certain specifications for latency and reliability; and massive machine type communications, which can allow a very large number of connected devices and transmission of a relatively low volume of non-delay-sensitive information. As the demand for mobile broadband access continues to increase, however, further improvements in NR communications technology and beyond may be desired.

<NPL> mentions that IAB-MT and IAB-DU require different procedures for inter-CU migration and warns about the fact that performing the migration of IAB-MT, IAB-DU and UE according to several procedures is not possible without creating a deadlock scenario.

RAN3 <NPL> recommend taking the leaf IAB-node migration as starting point when discuss the inter-donor migration, and then extend to the intermediate IAB node migration case; assuming that group based migration procedure should be supported, e.g. migrating node and all/parts its child nodes migrate together as a group; discussing group-based handover preparation procedure to allow performing the HO request and HO command feedback per migration group; from signaling aspects, the context of each member in the migration group, and the network topology information about the migration group should be transferred from the source IAB-donor to the target IAB-donor in HO preparation phase; before the migrating IAB-node receives its own HO command from the target IAB-donor, the F1AP messages which include the HO command for its child nodes generated by the target IAB-donor should be sent to the migrating IAB-node via the source IAB-donor; and discussing how to perform the F1 connection migration for the IAB-nodes in the migration group, from the source IAB-donor to the target IAB-donor.

<NPL> discusses a few enhancements that specifically apply to inter-donor parent-node change and RLF recovery, such as simultaneous connectivity of F1-C to source and target IAB-donor. This can be achieved by having independent F1-C connections by the IAB-DU to each IAB-donor, or by having one of the IAB-donor-CU's become an F1-C proxy for the other. It allows signaling to occur preemptively and thereby reduces the overall interruption time.

Aspects of the present disclosure provide techniques for migrating integrated access and backhaul (IAB) nodes, and more particularly the IAB-mobile terminal (IAB-MT), IAB distributed units (IAB-DUs), and/or user equipments (UEs) connected to the IAB node, from the source centralized unit (CU) to a target IAB-donor-CU of a base station. Features of the present disclosure achieve such migration by configuring the IAB-DU to establish F1-connection (F1-C) with the target IAB-donor-CU via the source path before the UE context transfer occurs. To this end, the source IAB-donor-CU may initiate an F1-C establishment between IAB-node DU and target IAB-donor-CU. The source IAB-donor-CU may do so by acting or presenting as an IAB-node-DU proxy to the target IAB-donor-CU. At the same time, the source IAB-donor-CU may act or present as a target-IAB-donor-CU proxy to the IAB-node-DU. Thus, in some cases, the source IAB-donor-CU may present as both the IAB-node-DU proxy (to the target IAB-donor-CU) and as a target-IAB-donor-CU proxy (to the IAB-node-DU). By establishing F1-C with the target IAB-donor-CU via the source path, the IAB-node-DU may establish a new transport network layer association (TNLA) with the target IAB-donor-CU that it uses for its F1-C signalling.

In one example, a method for wireless communication is disclosed. The method may include establishing a first signaling connection between a source IAB-donor- CU with at least one IAB-DU. The method may also include establishing a second signaling connection between the source IAB-donor CU and a target IAB-donor CU. The method may also include configuring the source IAB-donor CU to function as a first proxy for the at least one IAB-DU in order to transmit state information associated with the at least one IAB-DU to the target IAB-donor CU. The method may include receiving, at the IAB-donor CU, a state update information from the target IAB-donor CU. The method may also include configuring the source IAB-donor CU to function as a second proxy for the target IAB-donor CU in transmitting the state update information to the at least one IAB-DU.

In another example, an apparatus for wireless communications. The apparatus may include a memory having instructions and a processor configured to execute the instructions to establish a first signaling connection between a source IAB-donor CU with at least one IAB-DU. The processor may further be configured to execute the instructions to establish a second signaling connection between the source IAB-donor CU and a target IAB-donor CU. The processor may further be configured to execute the instructions to configure the source IAB-donor CU to function as a first proxy for the at least one IAB-DU in order to transmit state information associated with the at least one IAB-DU to the target IAB-donor CU. The processor may further be configured to execute the instructions to receive, at the IAB-donor CU, a state update information from the target IAB-donor CU. The processor may further be configured to execute the instructions to configure the source IAB-donor CU to function as a second proxy for the target IAB-donor CU in transmitting the state update information to the at least one IAB-DU.

In some aspects, a non-transitory computer readable medium includes instructions stored therein that, when executed by a processor, cause the processor to perform the steps of establishing a first signaling connection between a source IAB-donor- CU with at least one IAB-DU. The processor may further perform the steps of establishing a second signaling connection between the source IAB-donor CU and a target IAB-donor CU. The processor may further perform the steps of configuring the source IAB-donor CU to function as a first proxy for the at least one IAB-DU in order to transmit state information associated with the at least one IAB-DU to the target IAB-donor CU. The processor may further perform the steps of receiving, at the IAB-donor CU, a state update information from the target IAB-donor CU. The processor may further perform the steps of configuring the source IAB-donor CU to function as a second proxy for the target IAB-donor CU in transmitting the state update information to the at least one IAB-DU.

In certain aspects, another apparatus for wireless communication is disclosed. The apparatus may include means for establishing a first signaling connection between a source IAB-donor- CU with at least one IAB-DU. The apparatus may further include means for establishing a second signaling connection between the source IAB-donor CU and a target IAB-donor CU. The apparatus may further include means for configuring the source IAB-donor CU to function as a first proxy for the at least one IAB-DU in order to transmit state information associated with the at least one IAB-DU to the target IAB-donor CU. The apparatus may further include means for receiving, at the IAB-donor CU, a state update information from the target IAB-donor CU. The apparatus may further include means for configuring the source IAB-donor CU to function as a second proxy for the target IAB-donor CU in transmitting the state update information to the at least one IAB-DU.

One aspect of the <NUM> NR communications technology includes the use of highfrequency spectrum bands, such as those above <NUM>, which may be referred to as millimeter wave (mmW) bands. The use of these bands enables extremely high data rates and significant increases in data processing capacity. However, compared to LTE, mmW bands are susceptible to rapid channel variations and suffer from severe free-space path loss and atmospheric absorption. In addition, mmW bands are highly vulnerable to blockage (e.g. hand, head, body, foliage, building penetration). Particularly, at mmW frequencies, even small variations in the environment, such as the turn of the head, movement of the hand, or a passing car, may change the channel conditions between the base station (BS) and the user equipment (UE), and thus impact communication performance.

Current mmW <NUM> NR systems leverage the small wavelengths of mmW at the higher frequencies to make use of multiple input multiple output (MIMO) antenna arrays to create highly directional beams that focus transmitted radio frequency (RF) energy in order to attempt to overcome the propagation and path loss challenges in both the uplink and downlink links. The isotropic path loss and the propagation characteristics of the mmWave environment, however, demands a dense next generation node base station (gNBs) (i.e., base stations in NR technology) deployment to guarantee line-of-sight links at any given time and to decrease the outage probability. In such deployments, equipping each gNB with a wired backhaul link (e.g., fiber) may not be feasible due to the high expense involved. As such, network operators have considered using wireless backhaul as a more cost-effective alternative solution for high-density deployment scenarios.

Facilitating wireless backhaul communication may include utilizing integrated access and backhaul (IAB) nodes (which may include "relay nodes") that may have both a base station (gNB)-type and a user equipment (UE)-type functionality. The IAB nodes provide the wireless communications system flexibility such that only a fraction of gNBs may be equipped with a traditional wired backhaul capabilities (e.g., using cable or optical fiber), while the rest of the gNBs (or IAB nodes) may have direct or indirect (e.g., via relay nodes) wireless connections to the wired backhaul, e.g., possibly through multiple hops via one or more relay nodes.

Thus, the IAB nodes may include the gNB-type functionality that allows for transmission and reception of signals to and from child nodes (e.g., a UE or another IAB node) through an access link. Additionally, the IAB nodes may also include the UE-type functionality that allows for transmission and reception of signals to and from a parent node (e.g., a gNB or another IAB node) through backhaul links. By utilizing an IAB node, a common architecture, common waveforms, and common procedures may be shared for access links and backhaul links, thereby reducing the system complexity. For example, the IAB nodes may share the same wireless resources (e.g., via TDM or FDM) between the access links and backhaul links.

In IAB network architecture, one or more base stations may include a centralized unit (CU) and a distributed unit (DU), and may be referred to as donor base stations (e.g., or IAB donors). One or more DUs associated with a donor base station may be partially controlled by one or more CUs associated with the donor base station. A base station CU may be a component of a database, data center, core network, or network cloud. A network node associated with a radio access technology (RAT) may communicate with a donor base station CU via a backhaul link (e.g., wireline backhaul or wireless backhaul). The one or more donor base stations (e.g., IAB donors) may also be in communication with one or more additional base stations (e.g., IAB nodes or relay nodes) and user equipment (UEs). IAB nodes may support mobile terminal (MT) functionality controlled and scheduled by an IAB donor and/or parent IAB nodes relative to the MT supported IAB nodes, as well as DU operability relative to additional entities (e.g., IAB nodes, UEs, etc.) within the relay chain or configuration of the access network (e.g., downstream). For example, an IAB network architecture may include a chain of connected wireless devices (e.g., starting with a donor base station and ending with a user equipment (UE), with any number of IAB relay nodes in between) via link resources that support NR access and backhaul capabilities (e.g., a wireline backhaul or wireless backhaul).

In some aspects, a relay node may refer to an intermediary node in a relay (e.g., an IAB relay) chain. For example, a relay node may relay communications between a parent node (e.g., an IAB donor, or an IAB node upstream or higher on the relay chain) and a child node (e.g., an IAB node downstream or lower on the relay chain). In some cases, the relay node may refer to the DU or access node function (AN-F) of an intermediary IAB node. A child node may refer to an IAB-Node (e.g., the CU/MT of the IAB-Node), or a child node may refer to a UE that is the child of another IAB-Node (e.g., such as the relay node) or an IAB-donor (e.g., the DU/ANF of the IAB-Node or IAB-Donor). A parent node in communication with the relay node may refer to an upstream IAB-Node or an IAB-donor (e.g., the DU/ANF of the IAB-Node or IAB-Donor). In some cases, a parent node may be referred to as a control node (e.g., a control node may refer to a parent node or a DU of a parent node in communication with an MT of a relay node or other intermediary IAB node).

Thus, as noted above, access nodes or base stations can be split into DUs and CU. The interface between DU and CU can be referred to as the F1 interface. Specifically, an F1-connection (F1-C) may be established between the IAB-donor CU and each of the IAB-donor DUs and IAB-node DUs. The F1-AP/SCTP connection may be used to exchange control plane (CP) messages. During the F1 setup procedure, a gNB-DU may send an F1 SETUP REQUEST message to the gNB-CU that includes a list of cells that are configured and ready to be activated. In turn, the gNB-CU may send an F1 SETUP RESPONSE message to the gNB-DU that optionally includes a list of cells to be activated. Each served cell on the gNB-DU may be identified by NR cell global identity (NR CGI) and/or NR physical cell ID (NR PCI) pair. In some aspects, F1AP services may be divided into non-UE associated services and UE-associated services.

In IAB network systems, when a mobile terminal (MT) of an IAB-node performs a handover from a source CU (e.g., CU-a) to a target CU (e.g., CU-b), the DUs associated with the IAB node should also migrate to the target CU (e.g., CU-b) and the IAB node may need to establish F1-C with the target CU. However, in order to perform such handover, the IAB-DU may require target path availability to the target CU. Similarly, the UEs connected to the IAB-node may need to perform handover to the target CU-b when the MT switches over source CU (e.g., CU-a) to a target CU (e.g., CU-b). However, in order to conduct such handover, the handover command delivery may require the source path availability. Thus, in current systems, attempting to migrate IAB-MT, IAB-DU-, and UE from the source CU to the target IAB-donor-CU may lead to deadlock scenario.

Aspects of the present disclosure provide techniques to overcome such deadlock. Specifically, in some aspects, the IAB-DU may establish F1-C with the target IAB-donor-CU via the source path before the UE <NUM> context transfer occurs. To this end, the source IAB-donor-CU may initiate an F1-C establishment between IAB-node DU and target IAB-donor-CU. The source IAB-donor-CU may do so by acting or presenting as an IAB-node-DU proxy to the target IAB-donor-CU. At the same time, the source IAB-donor-CU may act or present as a target-IAB-donor-CU proxy to the IAB-node-DU. Thus, in some cases, the source IAB-donor-CU may present as both the IAB-node-DU proxy (to the target IAB-donor-CU) and as a target-IAB-donor-CU proxy (to the IAB-node-DU). By establishing F1-C with the target IAB-donor-CU via the source path, the IAB-node-DU may establish a new transport network layer association (TNLA) with the target IAB-donor-CU that it uses for its F1-C signalling. The claimed invention corresponds to <FIG> and to the related text in the description, the other figures and the remaining text of the description are only intended to better explain the claimed invention.

Various aspects are now described in more detail with reference to the <FIG>. Additionally, the term "component" as used herein may be one of the parts that make up a system, may be hardware, firmware, and/or software stored on a computer-readable medium, and may be divided into other components.

The wireless communications system (also referred to as a wireless wide area network (WWAN)) can include base stations <NUM>, UEs <NUM>, an Evolved Packet Core (EPC) <NUM>, and/or a <NUM> Core (5GC) <NUM>. The macro cells can include base stations. The small cells can include femtocells, picocells, and microcells. In an example, the base stations <NUM> may also include gNBs <NUM>, as described further herein.

In one example, the base station <NUM> may be an IAB node (either IAB-donor node or IAB node) that includes a centralized unit (CU), a distributed unit (DU), and/or IAB-mobile terminal (MT). The base station <NUM> may have a modem <NUM> and a communication management module <NUM> (see <FIG>) for to implement techniques for migrating integrated access and backhaul (IAB) nodes, and more particularly the IAB-mobile terminal (IAB-MT), IAB distributed units (IAB-DUs), and/or user equipments (UEs) connected to the IAB node, from the source centralized unit (CU) to a target IAB-donor-CU of a base station. Features of the present disclosure achieve such migration by configuring the IAB-DU to establish F1-connection (F1-C) with the target IAB-donor-CU via the source path before the UE context transfer occurs. To this end, the source IAB-donor-CU may initiate an F1-C establishment between IAB-node DU and target IAB-donor-CU. The source IAB-donor-CU may do so by acting or presenting as an IAB-node-DU proxy to the target IAB-donor-CU. At the same time, the source IAB-donor-CU may act or present as a target-IAB-donor-CU proxy to the IAB-node-DU. Thus, in some cases, the source IAB-donor-CU may present as both the IAB-node-DU proxy (to the target IAB-donor-CU) and as a target-IAB-donor-CU proxy (to the IAB-node-DU). By establishing F1-C with the target IAB-donor-CU via the source path, the IAB-node-DU may establish a new transport network layer association (TNLA) with the target IAB-donor-CU that it uses for its F1-C signalling.

The base stations <NUM> may also be configured for <NUM> LTE (which can collectively be referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with the EPC <NUM> through backhaul links <NUM> (e.g., using an S1 interface). The base stations <NUM> configured for <NUM> NR (which can collectively be referred to as Next Generation RAN (NG-RAN)) may interface with 5GC <NUM> through backhaul links <NUM>. The base stations <NUM> may communicate directly or indirectly (e.g., through the EPC <NUM> or 5GC <NUM>) with each other over backhaul links <NUM> (e.g., using an X2 interface).

The base stations <NUM> may wirelessly communicate with one or more UEs <NUM>. A network that includes both small cell and macro cells may be referred to as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (eNBs) (HeNBs), which may provide service to a restricted group, which can be referred to as a closed subscriber group (CSG). The base stations <NUM> / UEs <NUM> may use spectrum up to Y MHz (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (e.g., for x component carriers) used for transmission in the DL and/or the UL direction. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL).

In another example, certain UEs <NUM> may communicate with each other using device-to-device (D2D) communication link <NUM>.

A base station <NUM>, whether a small cell <NUM>' or a large cell (e.g., macro base station), may include an eNB, gNodeB (gNB), or other type of base station. Some base stations, such as gNB <NUM> may operate one or more frequency bands within the electromagnetic spectrum. The electromagnetic spectrum is often subdivided, based on frequency/wavelength, into various classes, bands, channels, etc. In <NUM> NR two initial operating bands have been identified as frequency range designations FR1 (<NUM> - <NUM>) and FR2 (<NUM> - <NUM>). Although a portion of FR1 is greater than <NUM>, FR1 is often referred to (interchangeably) as a "Sub-<NUM>" 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" (mmW) band in documents and articles, despite being different from the extremely high frequency (EHF) band (<NUM> - <NUM>) which is identified by the International Telecommunications Union (ITU) as a "millimeter wave" band.

Communications using the mmW radio frequency band have extremely high path loss and a short range. The mmW base station <NUM> may utilize beamforming <NUM> with the UE <NUM> to compensate for the path loss and short range.

The 5GC <NUM> may include a Access and Mobility Management Function (AMF) <NUM>, other AMFs <NUM>, a Session Management Function (SMF) <NUM>, and a User Plane Function (UPF) <NUM>. The AMF <NUM> can be a control node that processes the signaling between the UEs <NUM> and the 5GC <NUM>. Generally, the AMF <NUM> can provide QoS flow and session management. User Internet protocol (IP) packets (e.g., from one or more UEs <NUM>) can be transferred through the UPF <NUM>. The UPF <NUM> can provide UE IP address allocation for one or more UEs, as well as other functions.

The base station <NUM> provides an access point to the EPC <NUM> or 5GC <NUM> for a UE <NUM>. IoT UEs may include machine type communication (MTC)/enhanced MTC (eMTC, also referred to as category (CAT)-M, Cat M1) UEs, NB-IoT (also referred to as CAT NB <NUM>) UEs, as well as other types of UEs. In the present disclosure, eMTC and NB-IoT may refer to future technologies that may evolve from or may be based on these technologies. For example, eMTC may include FeMTC (further eMTC), eFeMTC (enhanced further eMTC), mMTC (massive MTC), etc., and NB-IoT may include eNB-IoT (enhanced NB-IoT), FeNB-IoT (further enhanced NB-IoT), etc. The UE <NUM> 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.

<FIG> is a timing diagram <NUM> of an example of F1-connection that may be established between an IAB-donor CU <NUM> and IAB-donor DUs and IAB-node DUs. As noted above, in IAB network architecture, one or more base stations may include a centralized unit (CU) <NUM> and a distributed unit (DU) <NUM>, and may be referred to as donor base stations (e.g., or IAB donors). One or more DUs <NUM> associated with a donor base station may be partially controlled by one or more CUs <NUM> associated with the donor base station. A base station CU <NUM> may be a component of a database, data center, core network, or network cloud. The one or more donor base stations (e.g., IAB donors) may be in communication with one or more additional base stations (e.g., IAB nodes or relay nodes) and UEs.

The interface between DU <NUM> and CU <NUM> is generally referred to as the F1 interface. Specifically, an F1 interface or F1-connection (F1-C) may be established between the IAB-donor CU <NUM> and each of the IAB-donor DUs <NUM> and IAB-node DUs <NUM>. The F1-AP/SCTP connection may be used to exchange control plane (CP) messages. During the F1 setup procedure, a gNB-DU <NUM> may send an F1 SETUP REQUEST message <NUM> to the gNB-CU <NUM> that includes a list of cells that are configured and ready to be activated. In turn, the gNB-CU <NUM> may send an F1 SETUP RESPONSE message <NUM> to the gNB-DU <NUM> that optionally includes a list of cells to be activated. Each served cell on the gNB-DU <NUM> may be identified by NR cell global identity (NR CGI) and/or NR physical cell ID (NR PCI) pair. In some aspects, F1AP services may be divided into non-UE associated services and UE-associated services.

In some aspects, stream control transmission protocol (SCTP) may be supported as the transport layer for F1-C signaling bearer. In such cases, the gNB-DU and gNB-CU may support a configuration with a single SCTP association per gNB-DU/gNB-CU pair. Configurations with multiple SCTP endpoints per gNB-DU/gNB-CU pair may also be supported. When configurations with multiple SCTP associations are supported, the gNB-CU/gNB-DU may request to dynamically add/remove SCTP associations between the gNB-DU/gNB-CU pair. Transport network redundancy may be achieved by SCTP multi-homing between two end-points, of which one or both is assigned with multiple IP addresses. SCTP end-points may also support a multi-homed remote SCTP end-point.

<FIG> is a schematic diagram <NUM> of an IAB inter-donor topology adaptation. Specifically, in IAB network systems, when a mobile terminal (MT) <NUM> of an IAB-node <NUM> performs a handover from a source CU <NUM> (e.g., CU-a) to a target CU <NUM> (e.g., CUb), a DU <NUM> associated with the IAB node <NUM> may have to migrate to the target CU <NUM> (e.g., CU-b). In some examples, a first DU <NUM>-a may be associated with a source CU <NUM> and second DU <NUM>-b may be associated with a target CU <NUM>. The second DU <NUM>-b may refer to the migrated DU of the IAB node <NUM> and the IAB node <NUM> may need to establish F1-C with the target CU. However, in order to perform such handover, the IAB-DU <NUM> may require target path availability to the target CU <NUM> that may only be available to DU <NUM> after the IAB-MT <NUM> switches to parent Dub <NUM>. Similarly, the UEs <NUM> connected to the IAB-node <NUM> may also need to perform handover to the target CU-b <NUM> when the MT <NUM> switches over from source CU <NUM> (e.g., CU-a) to a target CU <NUM> (e.g., CU-b). However, in order to conduct such handover, the handover command delivery requires the source path availability that may only be available to the UE before the IAB-MT <NUM> switches to parent Dub <NUM>. Thus, in current systems, attempting to migrate IAB-MT <NUM>, IAB-DU <NUM>, and UE <NUM> from the source CU <NUM> to the target IAB-donor-CU <NUM> may lead to deadlock scenario.

Aspects of the present disclosure provide techniques to overcome such deadlock. Specifically, in some aspects, the IAB-DU <NUM> may establish F1-C with the target IAB-donor-CU <NUM> via the source path <NUM> before the parent switch of the IAB-MT <NUM> occurs such that a handover command to the UE <NUM> can still be forwarded along the source path. To this end, the source IAB-donor-CU <NUM> may initiate an F1-C establishment between IAB-node DU <NUM> and target IAB-donor-CU <NUM>. The source IAB-donor-CU <NUM> may do so by acting or presenting as an IAB-node-DU proxy to the target IAB-donor-CU <NUM>. At the same time, the source IAB-donor-CU <NUM> may act or present as a target-IAB-donor-CU proxy to the IAB-node-DU <NUM>. Thus, in some cases, the source IAB-donor-CU <NUM> may present as both the IAB-node-DU proxy (to the target IAB-donor-CU) and as a target-IAB-donor-CU proxy (to the IAB-node-DU). By establishing F1-C with the target IAB-donor-CU <NUM> via the source path, the IAB-node-DU <NUM> may then establish a new TNLA with the target IAB-donor-CU <NUM> that it uses for the F1-C signalling.

<FIG> is a schematic diagram <NUM> of an example IAB-DU migration that reflects the techniques of migrating IAB-DU from the source-CU <NUM> to the target CU <NUM>. The IAB-donor-CU, either source-CU <NUM> and/or target CU <NUM>, may be a gNB-CU. In some examples, a first IAB-donor-CU <NUM> (or a "source CU") may establish a first signaling connection <NUM> to an IAB-node <NUM> (as illustrated with the IAB-DU <NUM>). In some aspects, the DU <NUM> may be either an IAB-donor-DU or a gNB-DU. In some aspects, the first signaling connection may be F1-C or radio resource control (RRC) connection.

The first IAB-donor-CU <NUM> may then setup a second connection <NUM> a second IAB-donor-CU <NUM> (or a "target CU"). In such instance, the second connection <NUM> may be a F-1C signaling. Once the first IAB-donor-CU <NUM> has established the second signaling connection <NUM> with the second IAB-CU <NUM>, the first IAB-donor-CU <NUM> may act as a proxy <NUM> for a distributed unit of the IAB-node <NUM> and forward the state of the IAB-node-DU <NUM> to the second IAB-donor-CU <NUM>.

In some examples, forwarding the IAB-node-DU's state to the second IAB-donor-CU may include forwarding of a configuration sent by IAB-node-DU <NUM> to the first IAB-donor-CU <NUM> and/or forwarding of a configuration sent by first IAB-donor-CU <NUM> to the IAB-node-DU <NUM>. In some aspects, the first IAB-donor-CU <NUM> may further forward a second state update between the IAB-node-DU <NUM> and the second IAB-donor-CU <NUM>. The forwarding a state/state update to the second IAB-donor-CU <NUM> may also use an F1 Setup Request message or gNB-DU configuration update message or gNB-CU configuration update acknowledge message. Furthermore, forwarding a state update to the IAB-node-DU <NUM> may utilize one or more of F1 Setup Response message, gNB-DU configuration update acknowledge message, or gNB-CU Configuration Update message.

In some aspects, the IAB-node-DU state information that is forwarded by the first IAB-donor-CU <NUM> to the second IAB-donor-CU <NUM> may include one or more of a configuration of a cell served by the IAB-node-DU, transport layer information for an SCTP connection that carries UE-associated and/or non-UE associated F1-C signaling, transport layer info for an F1-U GTP-U tunnel for a child connected to the IAB-node-DU, or a context of a child connected to the IAB-node-DU, an identifier that is associated with the connection between the IAB-DU and the IAB-donor-CU, gNB-CU, a tunnel endpoint identifier between gNB-DU and gNB-CU, a stream between gNB-DU and gNB-CU, or child connected to the IAB-node-DU.

In some examples, the first IAB-donor-CU <NUM> may also indicate the same gNB-DU-ID as that of the IAB-node-DU <NUM> upon establishing the second signaling connection <NUM>. In some examples, the first IAB-donor-CU <NUM> may indicate to the IAB-DU <NUM> a TNL endpoint for the second IAB-donor-CU <NUM>. CU <NUM> may achieve this by providing an additional TNL endpoint to be used by the IAB-DU <NUM> to establish a new TNLA for the first signaling connection of IAB-DU. This may be possible in accordance with aspects of the present disclosure because the CU <NUM> may have multiple TNL endpoints for the first signaling connection that the CU <NUM> can select from. However, since the newly indicated TNL endpoint by CU-a <NUM> to the IAB-DU is configured that of Cub <NUM> instead of being an additional CU-a TNL endpoint for the first signaling connection, aspects of the present disclosure allow a direct TNLA to be established between a second CU <NUM> and the IAB DU <NUM>. The additional TNL endpoint <NUM> configured on second IAB-donor-CU <NUM> may comprise internet protocol (IP) address information for the second IAB-donor-CU <NUM>. The first IAB-donor-CU <NUM> may also indicate the TNLA <NUM> to be added using a gNB-CU configuration update message. In some aspects, the gNB-CU configuration update message may be sent using the TNLA <NUM>. In some aspects, the first IAB-donor-CU <NUM> may request the IAB-node <NUM> to acknowledge (ACK) the TNLA setup using IP address of second IAB-donor-CU <NUM> on the TNLA-b <NUM>.

In some aspects, the IAB-node-DU <NUM> may establish a second TNLA <NUM> (e.g. SCTP association) with the second IAB-donor-CU <NUM> based on the addition of the TNL Endpoint <NUM> for the second IAB-donor-CU <NUM> by the first IAB-donor-CU <NUM>. In such instance, the first IAB-donor-CU <NUM> may indicate to the IAB-node-DU <NUM> to use the second TNLA <NUM> for the first signaling connection. After the second TNLA <NUM> is established, the first IAB-donor-CU may instruct the IAB-node-DU <NUM> to remove a first TNLA <NUM> for the first signaling connection. The IAB-node-DU <NUM> may then include the gNB-DU ID in F1-C signaling that uses the second TNLA <NUM>. The IAB-node-DU <NUM> may also transmit a gNB-CU configuration update acknowledge message or gNB-DU configuration update message to the second IAB-donor-CU <NUM> after the second TNLA <NUM> becomes operational.

In some aspects, the first IAB-donor-CU <NUM> may indicate to the IAB-node <NUM> that the first IAB-donor-CU <NUM> is acting as a proxy for the second IAB-donor-CU <NUM>. The first IAB-donor-CU <NUM> may also provide an identifier of the second-IAB-donor-CU <NUM> to the IAB-node <NUM>. In some examples, the first IAB-donor-CU <NUM> may request the IAB-node-DU <NUM> to include the gNB-DU ID in F1-C signaling that uses the new TNLA.

In some examples, the first IAB-donor-CU <NUM> may then indicate to the second IAB-donor-CU <NUM> that the first IAB-donor-CU <NUM> is acting as a proxy for the IAB-node-DU <NUM>. The first IAB-donor-CU <NUM> may then transfer context for or indicate the corresponding IAB-node-MT <NUM> to the second IAB-donor-CU <NUM>. The first IAB-donor-CU <NUM> may indicate to the second IAB-donor-CU <NUM> that a second TNLA <NUM> will be established to be used by the IAB-node <NUM> for the second signaling connection. To this end, the second IAB-donor-CU <NUM> may request that the first IAB-donor-CU <NUM> remove a third TNLA for the second signaling connection after the IAB-node establishes the second TNLA <NUM>. As such, the first IAB-donor-CU <NUM> may remove the third TNLA used for the second signaling connection after indicating to the IAB-node <NUM> to establish the second TNLA <NUM> and/or after receiving an indication from the IAB-node <NUM> or the second IAB-donor-CU <NUM> that the second TNLA <NUM> has become operational.

In some cases, the second IAB-donor-CU <NUM> may provide the first IAB-donor-CU <NUM> with a new gNB-CU identifier that the first IAB-donor-CU <NUM> may send an update to the IAB-node <NUM>. The gNB-CU identifier may be a gNB-CU name. The gNB-CU identifier may be a gNB-ID based on which the first IAB-donor-CU reconfigures a cell ID for a cell served by the IAB-node-DU. The first IAB-donor-CU <NUM> may request the new gNB-CU identifier from the second IAB-donor-CU <NUM>.

In some examples, the second IAB-donor-CU <NUM> may provide the IAB-node <NUM> with a new gNB-CU identifier after the IAB-node <NUM> establishes a TNLA <NUM> with the second IAB-donor-CU <NUM>. Additionally or alternatively, the first IAB-donor-CU <NUM> may indicate to the second IAB-donor-CU <NUM> to provide a new gNB-CU identifier to the IAB-node after the second TNLA <NUM> becomes operational. The first IAB-donor-CU <NUM> may request the second IAB-donor-CU <NUM> to use the old gNB-CU identifier for the second signaling connection.

<FIG> illustrates a hardware components and subcomponents of a device that may be a base station <NUM> for implementing one or more methods (e.g., method <NUM>) described herein in accordance with various aspects of the present disclosure. For example, one example of an implementation of the base station <NUM> may include a variety of components, some of which have already been described above, but including components such as one or more processors <NUM>, memory <NUM> and transceiver <NUM> in communication via one or more buses <NUM>, which may operate in conjunction with the communication management component <NUM> to perform functions described herein related to including one or more methods (e.g., <NUM>) of the present disclosure. In some examples, the base station <NUM> may be an IAB node (either IAB-donor node or IAB node) that includes a centralized unit (CU), a distributed unit (DU), and/or IAB-mobile terminal (MT).

Particularly, communication management component <NUM> may implement techniques for migrating integrated access and backhaul (IAB) nodes, and more particularly the IAB-mobile terminal (IAB-MT), IAB distributed units (IAB-DUs), and/or user equipments (UEs) connected to the IAB node, from the source centralized unit (CU) to a target IAB-donor-CU of a base station. Features of the present disclosure achieve such migration by configuring the IAB-DU to establish F1-connection (F1-C) with the target IAB-donor-CU via the source path before the UE context transfer occurs. To this end, the source IAB-donor-CU may initiate an F1-C establishment between IAB-node DU and target IAB-donor-CU. The source IAB-donor-CU may do so by acting or presenting as an IAB-node-DU proxy to the target IAB-donor-CU. At the same time, the source IAB-donor-CU may act or present as a target-IAB-donor-CU proxy to the IAB-node-DU. Thus, in some cases, the source IAB-donor-CU may present as both the IAB-node-DU proxy (to the target IAB-donor-CU) and as a target-IAB-donor-CU proxy (to the IAB-node-DU). By establishing F1-C with the target IAB-donor-CU via the source path, the IAB-node-DU may establish a new transport network layer association (TNLA) with the target IAB-donor-CU that it uses for its F1-C signalling.

The one or more processors <NUM>, modem <NUM>, memory <NUM>, transceiver <NUM>, RF front end <NUM> and one or more antennas <NUM>, may be configured to support voice and/or data calls (simultaneously or non-simultaneously) in one or more radio access technologies. In an aspect, the one or more processors <NUM> can include a modem <NUM> that uses one or more modem processors. The various functions related to communication management component <NUM> may be included in modem <NUM> and/or processors <NUM> and, in an aspect, can be executed by a single processor, while in other aspects, different ones of the functions may be executed by a combination of two or more different processors. For example, in an aspect, the one or more processors <NUM> may include any one or any combination of a modem processor, or a baseband processor, or a digital signal processor, or a transmit processor, or a receiver processor, or a transceiver processor associated with transceiver <NUM>. In other aspects, some of the features of the one or more processors <NUM> and/or modem <NUM> associated with initial access module <NUM> may be performed by transceiver <NUM>.

The memory <NUM> may be configured to store data used herein and/or local versions of application(s) <NUM> or communication management component <NUM> and/or one or more of its subcomponents being executed by at least one processor <NUM>. The memory <NUM> can include any type of computer-readable medium usable by a computer or at least one processor <NUM>, such as random access memory (RAM), read only memory (ROM), tapes, magnetic discs, optical discs, volatile memory, non-volatile memory, and any combination thereof. In an aspect, for example, the memory <NUM> may be a non-transitory computer-readable storage medium that stores one or more computer-executable codes defining communication management component <NUM> and/or one or more of its subcomponents, and/or data associated therewith, when the base station <NUM> is operating at least one processor <NUM> to execute communication management component <NUM> and/or one or more of its subcomponents.

The transceiver <NUM> may include at least one receiver <NUM> and at least one transmitter <NUM>. The receiver <NUM> may include hardware, firmware, and/or software code executable by a processor for receiving data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium). The receiver <NUM> may be, for example, a radio frequency (RF) receiver. In an aspect, the receiver <NUM> may receive signals transmitted by at least one UE <NUM>. Additionally, receiver <NUM> may process such received signals, and also may obtain measurements of the signals, such as, but not limited to, Ec/Io, SNR, RSRP, RSSI, etc. The transmitter <NUM> may include hardware, firmware, and/or software code executable by a processor for transmitting data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium). A suitable example of the transmitter <NUM> may including, but is not limited to, an RF transmitter.

Moreover, in an aspect, transmitting device may include the RF front end <NUM>, which may operate in communication with one or more antennas <NUM> and transceiver <NUM> for receiving and transmitting radio transmissions, for example, wireless communications transmitted by at least one base station <NUM> or wireless transmissions transmitted by UE <NUM>. The RF front end <NUM> may be connected to one or more antennas <NUM> and can include one or more low-noise amplifiers (LNAs) <NUM>, one or more switches <NUM>, one or more power amplifiers (PAs) <NUM>, and one or more filters <NUM> for transmitting and receiving RF signals.

In an aspect, the LNA <NUM> can amplify a received signal at a desired output level. In an aspect, the RF front end <NUM> may use one or more switches <NUM> to select a particular LNA <NUM> and its specified gain value based on a desired gain value for a particular application.

Further, for example, one or more PA(s) <NUM> may be used by the RF front end <NUM> to amplify a signal for an RF output at a desired output power level. In an aspect, the RF front end <NUM> may use one or more switches <NUM> to select a particular PA <NUM> and its specified gain value based on a desired gain value for a particular application.

Also, for example, one or more filters <NUM> can be used by the RF front end <NUM> to filter a received signal to obtain an input RF signal. In an aspect, the RF front end <NUM> can use one or more switches <NUM> to select a transmit or receive path using a specified filter <NUM>, LNA <NUM>, and/or PA <NUM>, based on a configuration as specified by the transceiver <NUM> and/or processor <NUM>.

As such, the transceiver <NUM> may be configured to transmit and receive wireless signals through one or more antennas <NUM> via the RF front end <NUM>. In an aspect, the transceiver <NUM> may be tuned to operate at specified frequencies such that transmitting device can communicate with, for example, one or more UEs <NUM>. In an aspect, for example, the modem <NUM> can configure the transceiver <NUM> to operate at a specified frequency and power level based on the configuration of the transmitting device and the communication protocol used by the modem <NUM>.

In an aspect, the modem <NUM> can be a multiband-multimode modem, which can process digital data and communicate with the transceiver <NUM> such that the digital data is sent and received using the transceiver <NUM>. In an aspect, the modem <NUM> can be multiband and be configured to support multiple frequency bands for a specific communications protocol. In an aspect, the modem <NUM> can be multimode and be configured to support multiple operating networks and communications protocols. In an aspect, the modem <NUM> can control one or more components of transmitting device (e.g., RF front end <NUM>, transceiver <NUM>) to enable transmission and/or reception of signals from the network based on a specified modem configuration. In an aspect, the modem configuration can be based on the mode of the modem <NUM> and the frequency band in use. In another aspect, the modem configuration can be based on UE configuration information associated with transmitting device as provided by the network during cell selection and/or cell reselection.

Referring to <FIG>, an example method <NUM> for wireless communications in accordance with aspects of the present disclosure may be performed by one or more base stations <NUM> discussed with reference to <FIG>. Although the method <NUM> is described below with respect to the elements of the base station <NUM>, other components may be used to implement one or more of the steps described herein.

At block <NUM>, the method <NUM> includes establishing a first signaling connection between a source IAB-donor- CU with at least one IAB-DU. In some examples, the first signaling connection between the source IAB-donor-CU and the at least one IAB-DU may be one of F1-connection (F1-C) or radio resource control (RRC) connection. The at least one IAB-DU may be one of an IAB-donor-DU or an IAB-node-DU. Aspects of block <NUM> may be performed by the transceiver <NUM>, modem <NUM>, and communication management component <NUM> as described with reference to <FIG>. Thus, communication management component <NUM>, modem <NUM>, processor <NUM>, transceiver <NUM>, and/or the base station or one of its subcomponents may define the means for establishing a first signaling connection between a source IAB-donor- CU of a base station with at least one IAB-DU.

At block <NUM>, the method <NUM> includes establishing a second signaling connection between the source IAB-donor CU and a target IAB-donor CU. In some examples, the second signaling connection between the source IAB-donor-CU and the target IAB-donor-CU may be the F1-connection. In some examples, the IAB-donor-CU may be a base station CU. Aspects of block <NUM> may be performed by the transceiver <NUM>, modem <NUM>, and communication management component <NUM> as described with reference to <FIG>. Thus, communication management component <NUM>, modem <NUM>, processor <NUM>, transceiver <NUM>, and/or the base station or one of its subcomponents may define the means for establishing a second signaling connection between the source IAB-donor CU and a target IAB-donor CU.

At block <NUM>, the method <NUM> includes configuring the source IAB-donor CU to function as a first proxy for the at least one IAB-DU in order to transmit state information associated with the at least one IAB-DU to the target IAB-donor CU. In some aspects the state information associated with the at least one IAB-DU may include one or more of: a configuration of a cell served by the at least one IAB-DU, a context of a child connected to the at least one IAB-DU, a transport layer information for a stream Control Transmission Protocol (SCTP) connection that carries associated F1-connection signaling, a transport layer information for a child connected to the IAB-DU, or an identifier of one of a base station-DU, base station-CU, connection between the base station-DU and the base station-CU, a stream between the base station-DU and the base station-CU, or a child connected to the at least one IAB-DU. The state information may include transport layer information for a connection between the IAB-donor-CU and the at least one IAB-DU, an identifier of a connection between the IAB-donor-CU and the at least one IAB-DU, and an identifier of one or more of the at least one IAB-DU, the IAB-donor-CU or a child connected to the at least one IAB-DU used on a connection between the IAB-donor-CU and the at least one IAB-DU.

The state information associated with the at least one IAB-DU that is transmitted from the IAB-donor CU to the target IAB-donor CU may also comprise forwarding a configuration information associated with the at least one IAB-DU to the target IAB-donor CU that the source IAB-donor CU had previously transmitted to the at least one IAB-DU. The state information associated with the at least one IAB-DU that is transmitted from the IAB-donor CU to the target IAB-donor CU may also comprise forwarding a configuration information of the at least one IAB-DU that is received from the at least one IAB-DU at the source IAB-donor CU.

Configuring the source IAB-donor CU to function as the first proxy for the at least one IAB-DU includes determining an identifier of an IAB-mobile terminal (IAB-MT) associated with the at least one IAB-DU, and transmitting the identifier of the IAB-MT to the target IAB-donor CU in order to proxy for the at least one IAB-DU. In other examples, configuring the source IAB-donor CU to function as the first proxy for the at least one IAB-DU may comprise determining an identifier associated with at least one IAB-DU and representing the source IAB-donor CU as the at least one IAB-DU to the target IAB-donor-CU by adopting the identifier of the at least one IAB-DU for communications with the target IAB-donor-CU.

Aspects of block <NUM> may be performed by the transceiver <NUM>, modem <NUM>, and communication management component <NUM> as described with reference to <FIG>. Thus, communication management component <NUM>, modem <NUM>, processor <NUM>, transceiver <NUM>, and/or the base station or one of its subcomponents may define the means for configuring the source IAB-donor CU to function as a first proxy for the at least one IAB-DU in order to transmit state information associated with the at least one IAB-DU to the target IAB-donor CU.

At block <NUM>, the method <NUM> includes receiving, at the IAB-donor CU, a state update information from the target IAB-donor CU. In some examples, receiving the state update information from the target IAB-donor CU may comprise receiving, at the source IAB-CU, an updated base station-CU identifier from the target IAB-CU and reconfiguring, at the source IAB-CU, a cell identity (ID) for a cell served by the at least one IAB-DU based in part on the updated base station-CU identifier received from the target IAB-CU. The method may also include generating the state update information associated based in part on the cell-ID. Aspects of block <NUM> may be performed by the transceiver <NUM>, modem <NUM>, and communication management component <NUM> as described with reference to <FIG>. Thus, communication management component <NUM>, modem <NUM>, processor <NUM>, transceiver <NUM>, and/or the base station or one of its subcomponents may define the means for receiving, at the IAB-donor CU, a state update information from the target IAB-donor CU.

At block <NUM>, the method <NUM> includes configuring the source IAB-donor CU to function as a second proxy for the target IAB-donor CU in transmitting the state update information to the at least one IAB-DU. In some examples, the target IAB-donor CU and the at least one IAB-DU may use one or both of the state information or the state update information in order to establish a TNLA directly between the target IAB-donor-CU and the at least one IAB-DU. In other examples, the source IAB-donor-CU may indicate to the at least one IAB-DU a transport network layer (TNL) endpoint for the target IAB-donor-CU to enable the at least one IAB-DU to establish a transport network layer association (TNLA) TNLA between the target IAB-donor-CU and the at least one IAB-DU.

In some aspects, configuring the source IAB-donor CU to function as a second proxy for the target IAB-donor CU may include determining an identifier associated with the target IAB-donor CU, and representing the source IAB-donor CU as the target IAB-donor CU to the at least one IAB DU by adopting the identifier of the target IAB-donor CU for communications with the at least one IAB-DU.

Aspects of block <NUM> may be performed by the transceiver <NUM>, modem <NUM>, and communication management component <NUM> as described with reference to <FIG>. Thus, communication management component <NUM>, modem <NUM>, processor <NUM>, transceiver <NUM>, and/or the base station or one of its subcomponents may define the means for configuring the source IAB-donor CU to function as a second proxy for the target IAB-donor CU in transmitting the state update information to the at least one IAB-DU.

For example, due to the nature of software, functions described above may be implemented using software executed by a specially programmed processor, hardware, firmware, hardwiring, or combinations of any of these.

A storage medium may be any available medium that may be accessed by a general purpose or special purpose computer. By way of example, and not limitation, computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

The detailed description set forth above 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.

Several aspects of telecommunication systems are also presented with reference to various apparatus and methods. These apparatus and methods are described in the detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as "elements").

Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on a chip (SoC), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout the disclosure.

It should be noted that the techniques described herein may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and other systems. The terms "system" and "network" are often used interchangeably. IS-<NUM> Releases <NUM> and A are commonly referred to as CDMA2000 1X, 1X, etc. IS-<NUM> (TIA-<NUM>) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), IEEE <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, Flash-OFDM™, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies, including cellular (e.g., LTE) communications over a shared radio frequency spectrum band. The description below, however, describes an LTE/LTE-A and/or <NUM> New Radio (NR) system for purposes of example, and LTE or <NUM> NR terminology is used in much of the description below, although the techniques are applicable beyond LTE/LTE-A and <NUM> NR applications, e.g., to other next generation communication systems).

Claim 1:
A method (<NUM>) for wireless communications, comprising:
establishing (<NUM>) a first signaling connection between a source integrated access and backhaul, IAB, donor centralized unit, CU, with at least one IAB distributed unit, DU;
establishing (<NUM>) a second signaling connection between the source IAB-donor CU and a target IAB-donor CU;
configuring (<NUM>) the source IAB-donor CU to function as a first proxy for the at least one IAB-DU in order to transmit state information associated with the at least one IAB-DU to the target IAB-donor CU, wherein configuring the source IAB-donor CU to function as the first proxy for the at least one IAB-DU comprises:
determining an identifier of an IAB-mobile terminal, IAB-MT, associated with the at least one IAB-DU; and
transmitting the identifier of the IAB-MT to the target IAB-donor CU in order to proxy for the at least one IAB-DU;
receiving (<NUM>), at the source IAB-donor CU, a state update information from the target IAB-donor CU; and
configuring (<NUM>) the source IAB-donor CU to function as a second proxy for the target IAB-donor CU in transmitting the state update information to the at least one IAB-DU.