WO2019245547A1

WO2019245547A1 - A method to support topology discovery for integrated access and backhaul topology management and routing

Info

Publication number: WO2019245547A1
Application number: PCT/US2018/038523
Authority: WO
Inventors: Colin Kahn; Thomas Theimer
Original assignee: Nokia Technologies Oy; Nokia USA Inc
Current assignee: Nokia Technologies Oy; Nokia USA Inc
Priority date: 2018-06-20
Filing date: 2018-06-20
Publication date: 2019-12-26
Anticipated expiration: 2020-12-20

Abstract

A method includes obtaining, by at least one integrated access and backhaul node, at least one cell identifier of at least one radio function at the at least one integrated access and backhaul node. The method includes obtaining, by the at least one integrated access and backhaul node, at least one cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service, and associating, by the at least one integrated access and backhaul node, the at least one cell identifier of at least one upstream cell with at least one cell identifier of at least one integrated access and backhaul node to form at least one cell identifier pair. The method further includes sending the at least one cell identifier pair and any additional cell identifier pairs received from subtending integrated access and backhaul node to at least one donor or upstream integrated access and backhaul node.

Description

A METHOD TO SUPPORT TOPOLOGY DISCOVERY FOR INTEGRATED ACCESS AND BACKHAUL TOPOLOGY MANAGEMENTAND ROUTING

TECHNICAL FIELD:

[0001] The teachings in accordance with the exemplary embodiments of this invention relate generally to integrated access and backhaul networks. More specifically, teachings in accordance with the exemplary embodiments relate to node discovery, routing and topology management in an integrated access and backhaul system.

BACKGROUND:

[0002] Integrated access and backhaul (IAB) is a study item for 3GPP Release 15 and was further scheduled to be a work item for Release 16. RAN 2 and RAN 3 included tasks directed to providing support for a multi-hop self-backhaul network whereby 5G may be used to transport packets between IAB nodes and a (for example, IAB) donor with a fiber connection to the network core (for example, a next generation core (NGC)). Each IAB node may consist logically of a least a mobile terminal (MT) that communicates with upstream nodes, and a RAN component (for example, gNB DU) that communicates with downstream IAB nodes or subscriber UEs.

[0003] A subscriber UE or IAB node may support multi-connectivity with an upstream node, resulting in multiple paths between the core network and the UE. IAB nodes may also handover to other upstream IAB nodes or different donors when the wireless signal strength or connection quality on the current node deteriorates. The ability to change connectivity is particularly important as the main use case envisioned for IAB is small cells at mm or cm wavelengths, where capacity is high but propagation is variable and connectivity easily obstructed.

[0004] Certain abbreviations that may be found in the description and/or in the Figures are herewith defined as follows:

AMF Access and Mobility Management Function

CU Central Unit (of RAN)

DC Dual Connectivity

DU Distributed Unit

gNB 5G Enhanced Node B (Base station)

GTP GPRS Tunnelling Protocol

IAB: Integrated Access and Backhaul

IAB MT (IAB node UE): MT function in an IAB node

IAB DU (IAB node DU): gNB DU function in a IAB node

HO Handover

LTE long term evolution

MEC multi-access edge computing

MME mobility management entity

MT Mobile Terminal

NCE network control element

NG-AP Next generation application protocol

NGC Next generation core

NR New radio

NR-PDCCH New radio Physical Downlink Control Channel

N/W Network

OSPF Open Shortest Path First

PCI Physical Cell ID

PCRF Policy and Charging Rules Function

PDU Protocol Data Unit

RAN Radio Access Network

RLC Radio Link Control

RRC Radio Resource Control

RRM Radio Resource Management SMF Session Management Function

TM Topology Management

UDP User Datagram Protocol

UE User Equipment

UPF User Plane Function

5G Fifth generation mobile communication system

BRIEF SUMMARY

[0005] The following summary includes examples and is merely intended to be exemplary. The summary is not intended to limit the scope of the claims.

[0006] In accordance with one aspect, an example method comprises obtaining, by at least one integrated access and backhaul node , at least one cell identifier of at least one radio function at the at least one integrated access and backhaul node; obtaining, by the at least one integrated access and backhaul node function, at least one cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service; associating, by the at least one integrated access and backhaul node function, the at least one cell identifier of at least one upstream cell with at least one cell identifier of at least one integrated access and backhaul node to form at least one cell identifier pair; and sending the at least one cell identifier pair and any additional cell identifier pairs received from subtending integrated access and backhaul node to at least one donor or upstream integrated access and backhaul node.

[0007] In accordance with another aspect, an example apparatus comprises means for obtaining, by at least one integrated access and backhaul node, at least one cell identifier of at least one radio function at the at least one integrated access and backhaul node; means for obtaining, by the at least one integrated access and backhaul node, at least one distributed unit cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service; means for associating, by the at least one integrated access and backhaul node, the at least one cell identifier of at least one upstream cell with at least one cell identifier of at least one integrated access and backhaul node to form at least one cell identifier pair; and means for sending the at least one cell identifier pair and any additional cell identifier pairs received from subtending integrated access and backhaul node to at least one donor or upstream integrated access and backhaul node.

[0008] In accordance with another aspect, an example apparatus comprises at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to obtain, by at least one integrated access and backhaul node, at least one cell identifier of at least one radio function at least one integrated access and backhaul node; obtain, by the at least one integrated access and backhaul node, at least one cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service; associate, by the at least one integrated access and backhaul node, the at least one cell identifier of at least one upstream cell with at least one cell identifier of at least one integrated access and backhaul node to form at least one cell identifier pair; and send the at least one cell identifier pair and any additional cell identifier pairs received from subtending integrated access and backhaul node to at least one donor or upstream integrated access and backhaul node.

[0009] In accordance with another aspect, an example apparatus comprises a non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: obtaining, by at least one integrated access and backhaul node, at least one cell identifier of at least one radio function at least one integrated access and backhaul node; obtaining, by the at least one integrated access and backhaul node, at least one cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service; associating, by the at least one integrated access and backhaul node, the at least one cell identifier of at least one upstream cell with at least one cell identifier of at least one integrated access and backhaul node to form at least one cell identifier pair; and sending the at least one cell identifier pair and any additional cell identifier pairs received from subtending integrated access and backhaul node to at least one donor or upstream integrated access and backhaul node.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0010] The foregoing and other aspects of embodiments of this invention are made more evident in the following Detailed Description, when read in conjunction with the attached Drawing Figures, wherein:

[0011] Fig. l is block diagram of one possible and non-limiting example system in which the example embodiments may be practiced;

[0012] Fig. 2 shows an example illustration of a two hop IAB node configuration;

[0013] Fig. 3 shows an example illustration of an IAB node topology; [0014] Fig. 4 is an example illustration of an IAB Node Control Plane;

[0015] Fig. 5 is an example illustration of IAB Node Association;

[0016] Fig. 6 is an example illustration of topology discovery for Layer 2 and connectivity service IAB;

[0017] Fig. 7 is an example illustration of donors in a same area exchange the topology of their subtending IAB nodes; and

[0018] Fig. 8 shows a method in accordance with example embodiments which maybe performed by an apparatus.

DETAILED DESCRIPTION:

[0019] In the example embodiments as described herein a method and apparatus that provides downlink and uplink channel control procedures.

[0020] Turning to Fig. 1, this figure shows a block diagram of one possible and non-limiting example system in which the example embodiments may be practiced. In Fig. 1, the Mobile Terminal (MT) 110 is in wireless communication with the wireless network 100. The MT is awireless, typically mobile, device that can access the wireless network. The MT 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected through one or more buses 127. Each of the one or more transceivers 130 includes a receiver (Rx) 132 and a transmitter (Tx) 133. The one or more buses 127 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. The one or more memories 125 and the computer program code 123 may be configured to, with the one or more processors 120, cause the user equipment 110 to perform one or more of the operations as described herein. The MT 110 communicates with the apparatus 170 via a wireless link 111. 170 may be any one of the IAB donor 20 or the IAB nodes 12 for example. In this example the base station 170 has features or components of a gNB. A wireless attached IAB node, a Donor IAB node and a conventional gNB may be implemented on identical hardware or may include different hardware, but some of the core components such as processor(s), memory(ies), receiver(s) and transmitter(s) are present in each. Fig. 1 is merely intended to show a simplified version of some of the components of a IAB node, a Donor IAB node and a conventional gNB, but it is understood that there is a differentiation between a wireless IAB node and a Donor IAB node/gNB.

[0021] The gNB 170 is a base station (for example, for 5G/LTE) that provides access by wireless devices such as the MT 110 to the wireless network 100. The gNB 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N/W l/F(s)) 161, and one or more transceivers 160 interconnected through one or more buses 157. Each of the one or more transceivers 160 includes a receiver (Rx) 162 and a transmitter (Tx) 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. The one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 152, cause the gNB 170 to perform one or more of the operations as described herein. The one or more network interfaces 161 communicate over a network such as via the links 176 and 131. Two or more gNBs 170 communicate using, for example, link 176. The link 176 may be wired or wireless or both and may implement, for example, an X2 or Xn interface.

[0022] The one or more buses 157 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like. For example, the one or more transceivers 160 may be implemented as a remote radio head (RRH) 195, with the other elements of the gNB 170 being physically in a different location from the RRH, and the one or more buses 157 could be implemented in part as fiber optic cable to connect the other elements of the gNB 170 to the RRH 195.

[0023] It is noted that description herein indicates that“cells” perform functions, but it should be clear that the gNB that forms the cell will perform the functions. The cell makes up part of an gNB. That is, there can be multiple cells per gNB. For instance, there could be three cells for a single gNB carrier frequency and associated bandwidth, each cell covering one-third of a 360 degree area so that the single gNB’s coverage area covers an approximate oval or circle. Furthermore, each cell can correspond to a single carrier and an gNB may use multiple carriers. So if there are three 120 degree cells per carrier and two carriers, then the gNB has a total of 6 cells. [0024] The wireless network 100 may include one or more network elements 190. For example, with a EPC the network elements 190 may include MME (Mobility Management Entity) and/or SGW (Serving Gateway) functionality. As another example, with a 5G core network (5GCN) the network elements may include Access and Mobility Management Function (AMF), SMF (Session Management Function) and/or UPF (User Plane Gateway) functionality. Connectivity with a further network may be provided, such as a telephone network and/or a data network (for example, the Internet). The gNB/eNB 170 is coupled via a link 131 to the network element 190. The link 131 may be implemented as, for example, an SI or NG interface. The network element 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N/W I/F(s)) 180, interconnected through one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to, with the one or more processors 175, cause the network element 190 to perform one or more operations.

[0025] Those skilled in the art will appreciate that the various network element and network element components shown in Fig. 1 may be implemented differently in future wireless networks, and are not limited to 4G, LTE or 5G wireless networks (for instance, MT and gNB/DU are components of the LAB node). For example, the terms PCRF, MME, and SGW are terms generally used for the core elements in a LTE network. In contrast to LTE, future wireless networks may carry out network functions (NFs) by a plurality of cooperating devices. The different NFs, may include for example, Access and Mobility Management Function (AMF), Session Management Function (SMF), Policy Control Function (PCF), Application Function (AF), Authentication Server Function (AUSF), User Plane Function (UPF), and User Data Management (UDM). These NFs may be a virtualized function instantiated on an appropriate platform, such as a cloud infrastructure. For example, certain protocols (such as non real-time protocols for example) may be performed by one or more centralized units (CUs) in a cloud infrastructure, while one or more distributed units (DUs) operate the remaining protocols (e.g. real-time protocols) of the 5G radio interface ln this way, the various NFs may be split between CUs and DUs. Together a CU, underlying DUs, and RRHs may be considered as forming a logical base station (which maybe represented by gNB 170 in Fig. 1 for example).

[0026] The wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Network virtualization involves platform virtualization, often combined with resource virtualization. Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities that result from the network virtualization are still implemented, at some level, using hardware such as processors 152 or 175 and memories 155 and 171, and also such virtualized entities create technical effects. 5G may use edge cloud and local cloud architecture.

[0027] The computer readable memories 125, 155, and 171 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The computer readable memories 125, 155, and 171 may be means for performing storage functions. The processors 120, 152, and 175 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples. The processors 120, 152, and 175 may be means for performing functions, such as controlling the MT 1 10, eNB/gNB 170, and other functions as described herein.

[0028] Embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., an application specific integrated circuit), or a combination of software and hardware. In an example of an embodiment, the software (e.g., application logic, an instruction set) is maintained on anyone of various conventional computer-readable media. In the context of this document, a“computer-readable medium” may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, with one example of a computer described and depicted, e.g., in Fig. 1. A computer-readable medium may comprise a computer-readable storage medium or other device that may be any media or means that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

[0029] Having thus introduced one suitable but non-limiting technical context for the practice of the example embodiments of this invention, the example embodiments will now be described with greater specificity. [0030] Referring to Fig. 2, an example illustration of a two hop IAB node configuration 200. Donor 220 may be connected to MT function 240 via IAB node 1 and IAB node 2.

[0031] For IAB, each IAB node (for example, IAB node 1 210-1, IAB node2210-2) consists logicallyof at least a MT function (IAB MT 240-1, 240-2) that communicates with upstream nodes, and a RAN component, such as a gNB Distributed Unit (DU) (shown as 230-1, 230-2) for example, that communicates with downstream IAB nodes (210) and/or subscriber MTs 110. A given IAB node may have directly connected MTs 110, and serve downstream IAB nodes.

[0032] A central unit (CU) is a logical node which may include the functions (for example, gNB functions) such as transfer of user data, mobility control, radio access network sharing, positioning, session management etc., except those functions allocated exclusively to the DU. A CU may control the operation of DUs over a front-haul (Fs) interface. A Distributed Unit (DU) is a logical node which may include a subset of the functions (for example, gNB functions), depending on the functional split option. The operation of the DU may be controlled by the CU. The DU or gNB function IAB nodes with a CU-DU split are a particular implementation of a radio function in an IAB node environment with which the example embodiments may be implemented.

[0033] In 3GPP networks user plane packets may be tunneled using GTP/UDP/IP between the core network and the MT serving base station (for example, gNB or eNB). In the absence of self-backhaul, standard routing or forwarding may be used to send IP packet between the tunnel endpoints. If the MT 110 moves (for example, does a handover), the GTP tunnel endpoint may be updated, and a new IP address may be used by the core network to send packets to the new gNB/eNB).

[0034] Multi-connectivity and changing topology may result in a tree/mesh/graph IAB topology in which connectivity and routing must be managed. The example embodiments described herein may manage connectivity and routing in two sections or approaches. These include topology management and routing/forwarding. Topology management may determine the tree/mesh/graph structure by altering connectivity between IAB Nodes MTs 110 and upstream radios. Routing/forwarding may determine the path or route through the IAB tree/mesh/graph over which packets may be forwarded.

[0035] Topology management may be required to have the following characteristics. Topology management may change the topology at any time by triggering an IAB node handover, establishing new IAB node connectivity (for example, IAB node dual connectivity (DC)), or by admitting a new IAB node or donor to the network. Topology changes may be based on aggregate IAB node considerations such as IAB node and donor congestion, IAB node link quality with upstream nodes, and IAB node hop distance from a donor. Changes may not be based on per-subscriber MT considerations as there may be many subscriber MTss served either directly by an IAB node or in the topology structure beneath an IAB node. This is because it would be impractical to alter IAB node connectivity based on a request or conditions encountered by just one of these MTs 1 10.

[0036] Topology management may provide one or more connectivity options to connect an IAB node with the network. All IAB nodes may have a view of the complete topology, so that each IAB node can take routing decisions based on their topology view. In contrast to 3 GPP protocols that only provide direct neighbor discovery, but not a complete topology view across multiple IAB nodes, the IAB nodes may determine/learn/receive a complete topology view across multiple nodes.

[0037] Routing/forwarding may have the following characteristics. Routing/forwarding may determine the path used to forward a flow. The granularity may be as low as per-subscriber MT Flow. Paths may be between the MT-serving IAB node and a network end-point (for example, UPF). Topology may be a constraint on the choice of possible routes, and at a given point in time there may be only one route available. When there is a topology change, routes may require updating to ensure that packets are forwarded on the correct path between the MT serving IAB node and the network.

[0038] In certain embodiments, for example as shown in Fig. 2, an IAB node, may include a MT part which is similar to MT 110 for communication with the donor node or a parent IAB node’s RAN part, in a multi-hop embodiment, and a RAN/DU part which may be similar to a network entity/gNB 170 for communication with access MTs or a next hop IAB node MT part. In certain embodiments, therefore, a single IAB node may include at least two processors, at least two transceivers, at least two memories, and at least two antennas. In other embodiments the processors, transceivers, memories and/or antennas may be shared between the MT part and the RAN part of the IAB node.

[0039] Referring now to Fig. 3, an example illustration of an IAB node topology 300 is shown.

I I [0040] When a gNB (or DU part of a gNB) has a wired connection to the network, there is no need for link state discovery beyond that used by normal switches / routers at the transport layer in the backhaul network. Well known routing protocols (for example, IS-IS, OSPF) may be used to find the best path for routing packets between the core network (or CU part of a gNB) and the MT Serving gNB (or DU). The gNB ΪR address may be provided and kept current by the 3GPP control plane (NG-AP in 5G, S l-AP in 4G). 3GPP radio protocols are then used to deliver packets directly between the RAN and subscriber UEs.

[0041] With LAB, additional routing may be necessary between the donor and the MT serving IAB node. A subscriber MT 1 10 or an IAB node in the chain may be multi-connected to upstream nodes (for example, using 3GPP dual connectivity), or an IAB node in the path may change its connectivity creating a new topology configuration. Links may come and go depending on changing RF propagation or because of IAB node mobility. To support route calculation through this dynamic topology, the example embodiments provide a method to discover and maintain a map of connected nodes, and convey link associations to a control function. The example embodiments contrast with conventional routing protocols that run between routers and require neighbor discovery and broadcast of information such as Link State Advertisements (LSAs). It is not efficient to directly apply these conventional protocols on 3GPP wireless links of IAB nodes. For IAB, the example embodiments allow link state to be discovered and tracked by extending 3GPP protocols,

[0042] The example embodiments may be applied to situations such as shown in Fig. 3, which shows two donors 220 with subtend ing IAB nodes (IAB 1 210- 1 to IAB 8 210-8). IAB2210-2 and IAB 5 2l0-5 may have dual connectivity to upstream nodes. Other IAB nodes may have one upstream connection. The example embodiments may use knowledge of the topology as follows to affect both routing and topology management,

[0043] With regard to routing. Donor<->IAB2 (1 hop) may be preferred over the dual connectivity link through IAB 3 (3 hops). IAB4<->IAB5 (2 hops) may be preferred over the dual connectivity link through IAB6 (3 hops). If IAB7 were to HO to IAB 5, routing tables in IAB4 must be updated to forward packets to IAB5 rather than IAB6. A similar routing update may be needed whenever there is a topology change. The example embodiments may determine the topology, including the number of hops from an IAB node to the donor. The hop count is part of the topology information. Knowing the topology (including the number of hops) is important for routing. [0044] With regard to topology management. IAB6 may decide to HO IAB7 to IAB2 if the signal strength of IAB2 becomes comparable to IAB6 (thereby reducing the maximum hop count by 1 , If there is an HO decision to be made, then hop count may be a factor. If the HO is required (in other words, there is no other option), then the topology information may be of lesser importance For example, IAB6 may determine that a signal strength of at least one non-serving integrated access and backhaul node or the donor is comparable to or better than its own signal strength , and a minimum hop count of the at least one nonserving integrated access and backhaul node is lower than the minimum hop count of the serving integrated access and backhaul node; and perform a hand over to the at least one non-serving integrated access and backhaul node (IAB2). The serving IAB node (or more generally the serving gNB 170) decides when to handover the IAB Node MT . If there is more than one path from the IAB node to the donor, the serving IAB node may select the one with the minimum hop count. In another example, IAB6 may determine that a signal strength of at least one non-serving integrated access and backhaul node or the donor is significantly greater than its own signal strength, and the hop count of the at least one non-serving integrated access and backhaul node is only one greater than the current hop count; and perform a hand over to the at least one non-serving integrated access and backhaul node.

[0045] In another topology management example, a new IAB node should never be allowed to connect to IAB8 since it would exceed the maximum allowed hop count (equal to 4 in this example).

[0046] The example embodiments herein provide a mechanism to discover the 1AB node topology to support both topology management and routing.

[0047] Fig.4 is an example illustration of an IAB node control plane 400. As shown inFig.4, IAB node control plane 400 includes an IAB node CP (in IAB node or donor) 420 that receives measurements and controls connectivity 410 for IAB nodes 210 (shown therein as IAB node-1 210-1 and IAB node-2210-2).

[0048] The example embodiments provide a mechanism to discover the IAB node topology in a (for example, 5G) multi-hop self-backhaul network. The discovered topology may be used to further manage topology by controlling IAB node connectivity and to determine routes for forwarding packets between an MT serving IAB node and the core network. The example embodiments may be implemented based on (and may support) an IAB framework such as that provided/described in 3GPP RAN3, RAN2, etc. [0049] The IAB node 210 may consist of at least a radio function (for example, component) and a MT function (for example, component) 430. The radio function may be a DU 440 or a full gNB (for example, a DU component 440 and a CU component 450 (DU+CU)). There may be additional components such as a UPF to act as a PDU session anchor.

[0050] The MT component may support both user and control plane connectivity with an upstream node. The upstream node may be another IAB node 210, or a donor 420 (with a wired connection to the network).

[0051] The radio component may support a control plane protocol (RRC) with a downstream IAB node MT and/or subscriber MT 1 10. RRC is a control plane protocol layer between the MT 110 (or IAB Node MT 240) and the CU part of the gNB 170.

[0052] According to example embodiments, in a similar manner as with 5 G subscriber MTs 110, use of radio resources by the IAB node MT (240) function is expected to be determined by a radio resource management (RRM) function 455 inthe CU component of the upstream gNB (in an IAB node 210 or donor 420). Procedures and Signaling to convey radio measurements (for example, signal strength), and to control connectivity, including establishing connections and supporting handover, will be supported by the radio resource control (RRC) 450, a protocol layer that resides in the control plane between the MT (RRC 430) and the gNB (RRC) 450 as shown in Fig. 4.

[0053] RRC may support establishment, configuration, maintenance and release of radio bearers; MT measurement reporting and control of the reporting to support mobility; handover signalling, MT cell selection and similar functions.

[0054] Fig. 5 is an example illustration of IAB node association 500 used to construct topology information. As shown, CU or gNB RRM of IAB- 1 210-1 may broadcast cell ID (PCI) 510 of IAB-l 210-1 via RRC to IAB-2210-2. IAB-210-1 may correlate the received identifier with the cell ID of its own DU(s). IAB-2 210-2 may send a link state 530 consisting ofthe matched cell IDs to LAB-l 210-1. The link state 530 may be conveyed by a message sent from the IAB-2 210-2. In some example embodiments that message may be an RRC message. In other embodiments it may be sent in a message between the DU part of IAB-210-2 and the CU. In other words, the source ofthe message conveying the Link State 530 may be any component in IAB-2 210-2.

[0055] The example embodiments provide topology discovery for IAB so that every CU controlling an IAB node can determine (for example, learn) the subtending tree/graph structure (for example, in a manner similar to a link state protocol). Each IAB node 210 may determine the one-tier hierarchy, linking the IAB node MT and DU. One-tier hierarchy is the association between IAB Nodes (or IAB node and donor) that are one hop apart in the topology. The association indicates connectivity (a link) between the two nodes.

[0056] Internally, each LAB node may obtain the DU Cell IDs 520 (for example, the physical cell ID (PhysCellld/PCI)) as shown in LAB-2 210-2 of Fig. 5, NR Cell Global Identifier (NCGI) or similar cell/radio ID of the IAB node 210-2. An IAB node 210 may be composed of a MT part and a Radio (DU) part. The example embodiments provide for communication between these“parts”, which are in other instances independent functions that do not communicate (except over 5G air-interface which is not relevant in this step). For example, an LAB Node MT 240 may obtain the DU Cell IDs using messaging over a wired interface that is designed/implemented for this purpose. According to example embodiments, more than one DU may be supported if an IAB node 210 is to support more than one cell.

[0057] The IAB node MT 240 may also obtain the DU Cell ID(s) of the upstream cell(s) (PCI-2 540) from the upstream cell(s). The MT 1 10 may obtain these IDs through cell broadcast information. To form the equivalent of a neighbor association, the LAB node 210-2 may associates it’s serving DU Cell IDs (of upstream nodes) 540 with cell IDs of the IAB Node DUs (downstream) 550. The cell ED Pairs, and any additional Pairs that are received from subtending LAB nodes 210, may then be sent from the IAB nodeMT to the CU or gNB, using RRC messages, Fl messages, or other types of messages, which may emulate link state advertisements in routed networks.

[0058] When this process is repeated at each LAB node 210, the result is a topology table containing link- states as further described with respect to Fig. 6. The link states/topology may then be used by a function in the CUs to choose a forwarding path for the subscriber MT 110 and to manage the topology as previously discussed.

[0059] Fig. 6 is an example illustration of topology discovery 600 for layer 2 610 and connectivity service LAB 620. [0060] Two main architecture groups for IAB may be implemented by 3GPP as shown in Fig. 6. In the “Layer 2 Approach” 610, transport channels (RLC layer) may be relayed over multiple DU hops (IAB-1 210-1 and LAB-2 210-2) to a donor 650 that hosts RRM for all subtending DUs. In this instance the individual node associations may be sent by subtending IAB nodes 210 to the CU / donor 650 which may create a topology table 630 containing all link associations (for example, upstream node 640 PCI to downstream node 645 PCI). According to example embodiments, the architecture for the L2 approach may include an“adaptation” layer above RLC to control routing of packets through the LAB tree/graph. The discovered node associations may be used by RRM (donor 650) to control adaptation layer routing.

[0061] In the“Connectivity Service” approach 620, each self-backhaul hop may be an end-to-end connectivity service between an IAB Node MT 240 and an IAB node-embedded UPF 670 with minimal functionality. Donors 660 may include gNB RRM. In a multi-hop topology, RRM is distributed in the IAB nodes 210 as shown in Fig, 6. Each IAB node may learn (for example, using the method described in the above example whereby upstream and downstream node cell IDs are associated) the subtending topology of that particular IAB node and may make uplink and downlink routing decisions accordingly. For example, if in Fig. 6 (connectivity service approach 620) a downlink packet is being sent through a GTP tunnel to IAB-3 210-3, IAB-1 will determine from the first and last lines in its topology table 625 to forward the packet to IAB-2.

[0062] In both architectures (610, 620) donors may have a special role. The donors may perform as the border between the wired backhaul network where topology management is not applicable and routing uses standard wireline protocols, and the IAB tree where wireless (for example, 3GPP wireless) protocols apply. The donors may receive a complete picture of the topology of underlying IAB nodes 210, and may distribute that complete topology picture to IAB nodes 210 or other donors.

[0063] A combination of both approaches may be implemented in instances in which some IAB hops are Layer 2 610 and other use a Connectivity Service 620. In this case the individual node associations may be sent by subtending IAB nodes 210 to the CU / donor according to the connectivity approach at each hop.

[0064] Fig. 7 is an example illustration 700 of donors in a same area exchanging the topology of their subtending IAB nodes. [0065] When there is more than one gNB designated as a donor in a region where IAB nodes are deployed, as was the case in the example shown in Fig. 3, the donors may exchange topology information via the Xn interface (a logical interface which may interconnect RAN nodes, for example, gNB to gNB and eLTE eNB to gNB and vice versa) as illustrated in Fig. 7. Each donor may then make topology and routing decisions based on a full knowledge of IAB node connectivity. For example, if in the Fig. 7, IAB-l 210-1 provided adequate signal strength to serve LAB-7210-7, TM in donor 2 would have information because of the exchange of topology tables to make a determination to trigger a HO request to donor 1 as a HO would reduce the hop count from 3 to 2. After the HO is complete, the process described above may then be implemented to update the Topology tables in each CU/donor to reflect that IAB-l 210-1 is the upstream node of IAB-7 210-7, and packets for LAB-7 210-7 may be routed accordingly,

[0066] According to example embodiments, routing/forwarding packets over established connections and topology management may be implemented using the topology tables 630 (and 625) disclosed herein. The topology table according to the example embodiments may contain important information that may be used for both functions. According to another example embodiment of TM, if a new IAB node 210 were deployed in Fig. 6 herein above, the IAB node 210 may measure comparable signal strength from LAB-1 210-1 and IAB-3 210-3. Because of the topology table, RRM/RRC will be able to determine that connectivity directly at IAB-l 210-1 would entail two hops to the donor while at IAB-3 210-3 there would be 4 hops, enabling RRM/RRC to provide direction accordingly,

[0067] Fig. 8 is an example flow diagram 800 illustrating a method in accordance with example embodiments which may be performed by an apparatus.

[0068] At block 810, each IAB Node (for example, the LAB Node MT (function/component) 240) may internally obtain the DU Cell IDs of the IAB node 210. Note that more than one DU may be supported and there may be more than one Cell ID per DU. According to example embodiments, either the MT or the RAN part of the IAB node 210 may make the topology association and formulate the message sent to the upstream node by the MT. For example the DU could formulate an Fl-AP message.

[0069] At block 820, the IAB node 210 may also obtain the DU Cell ID(s) of the upstream cell(s) providing it with service. The MT 110 may obtain these IDs through cell broadcast information. [0070] At block 830, the LAB node 210 may associate it’s serving DU Cell IDs (of upstream nodes) with cell IDs of the LAB Node DUs to form (for example, the equivalent of) neighbor associations.

[0071] At block 840, the LAB node 210 may then send the cell ID Pairs, and any additional pairs that are received from subtending LAB nodes to the CU or gNB, using RRC messages, Fl messages or other messages thereby emulating link state advertisements in routed networks. For example, the IAB node 210 may send cell identifier pairs using 3GPP RRC, Fl or Xn interface messages. In other words, the IAB node 210 may send cell identifier pairs using MT, DU or gNB messages.

[0072] At block 850, steps 810-840 may be repeated at each LAB node resulting in a topology table containing link-states.

[0073] Without in any way limiting the scope, interpretation, or application of the claims appearing below, a technical effect of one or more of the example embodiments disclosed herein is to provide support for self-backhaul in radio networks.

[0074] An example embodiment may provide a method comprising obtaining, by at least one integrated access and backhaul node, at least one cell identifier of at least one radio function at least one integrated access and backhaul node; obtaining, by the at least one integrated access and backhaul node, at least one cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service; associating, by the at least one integrated access and backhaul node, the at least one cell identifier of at least one upstream cell with at least one cell identifier of at least one integrated access and backhaul node to form at least one cell identifier pair; and sending the at least one cell identifier pair and any additional ceil identifier pairs received from subtending integrated access and backhaul node to at least one donor or upstream integrated access and backhaul node.

[0075] In accordance with the example embodiments as described in the paragraphs above, performing each step of the preceding paragraph at each of a plurality of integrated access and backhaul nodes resulting in a topology table containing link-states.

[0076] In accordance with the example embodiments as described in the paragraphs above, wherein the at least one integrated access and backhaul node comprises at least a radio and a mobile termination function.

[0077] In accordance with the example embodiments as described in the paragraphs above, determining routes for forwarding packets between at least one user equipment serving integrated access and backhaul node and a core network or radio access network central unit.

[0078] In accordance with the example embodiments as described in the paragraphs above, determining that a topology change has occurred; and performing a routing update based on the topology change.

[0079] In accordance with the example embodiments as described in the paragraphs above, performing topology management based on controlling integrated access and backhaul node connectivity.

[0080] In accordance with the example embodiments as described in the paragraphs above, determining that a signal strength of at least one non-serving integrated access and backhaul node is comparable to a signal strength of a serving integrated access and backhaul node, wherein a minimum hop count of the at least one non-serving integrated access and backhaul node is lower than the minimum hop count of the serving integrated access and backhaul node; and performing hand over to the at least one non-serving integrated access and backhaul node.

[0081] In accordance with the example embodiments as described in the paragraphs above, performing topology discovery for integrated access and backhaul to allow at least one central unit controlling at least one integrated access and backhaul node to determine a subtending topology structure.

[0082] In accordance with the example embodiments as described in the paragraphs above, applying a layer 2 approach to integrated access and backhaul; relaying at least one transport channel over multiple distributed unit hops to at least one donor that hosts the central unit for all subtending distributed units; and creating a topology table containing all link associations.

[0083] In accordance with the example embodiments as described in the paragraphs above, applying a connectivity service approach to integrated access and backhaul; sending packets over self-backhaul hops that each constitute an end-to-end connectivity service between an integrated access and backhaul node mobile termination function and an integrated access and backhaul node-embedded user plane function.

[0084] In accordance with the example embodiments as described in the paragraphs above, wherein a topology is distributed to at least one additional donor.

[0085] In accordance with the example embodiments as described in the paragraphs above, sending cell identifier pairs using at least one of 3GPP RRC, FI or Xn interface messages

[0086] An example embodiment may provide an apparatus comprising, means for obtaining, by at least one integrated access and backhaul node, at least one cell identifier of at least one distributed unit or gNB function at least one integrated access and backhaul node; means for obtaining, by the at least one integrated access and backhaul node, at least one distributed unit cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service; means for associating, by the at least one integrated access and backhaul node, the at least one cell identifier of at least one upstream cell with at least one cell identifier of at least one integrated access and backhaul node to form at least one cell identifier pair; and means for sending the at least one cell identifier pair and any additional cell identifier pairs received from subtending integrated access and backhaul node to at least one donor or upstream integrated access and backhaul node.

[0087] In accordance with the example embodiments as described in the paragraphs above, means for performing each step performed by the apparatus of the preceding paragraph at each of a plurality of integrated access and backhaul nodes resulting in a topology table containing link-states.

[0088] In accordance with the example embodiments as described in the paragraphs above, wherein the at least one integrated access and backhaul node comprises at least a radio and a mobile termination function.

[0089] In accordance with the example embodiments as described in the paragraphs above, means for determining routes for forwarding packets between at least one user equipment serving integrated access and backhaul node and a core network or radio access network central unit.

[0090] In accordance with the example embodiments as described in the paragraphs above, means for determining that a topology change has occurred; and means for performing a routing update based on the topology change. [0091] In accordance with the example embodiments as described in the paragraphs above, means for performing topology management based on controlling integrated access and backhaul node connectivity.

[0092] In accordance with the example embodiments as described in the paragraphs above, means for determining that a signal strength of at least one non-serving integrated access and backhaul node is comparable to a signal strength of a serving integrated access and backhaul node, wherein the minimum hop count of the at least one non-serving integrated access and backhaul node is lower than the minimum hop count of the serving integrated access and backhaul node; and means for performing hand over to the at least one non-serving integrated access and backhaul node.

[0093] In accordance with the example embodiments as described in the paragraphs above, means for performing topology discovery for integrated access and backhaul to allow at least one central unit controlling at least one integrated access and backhaul node to determine a subtending topology structure.

[0094] In accordance with the example embodiments as described in the paragraphs above, means for applying a layer 2 approach to integrated access and backhaul; means for relaying at least one transport channel over multiple distributed unit hops to at least one donor that hosts the CU for all subtending distributed units; and means for creating a topology table containing all link associations.

[0095] An example embodiment may be provided in an apparatus comprising at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to: obtain, by at least one integrated access and backhaul node, at least one cell identifier of at least one radio function at least one integrated access and backhaul node; obtain, by the at least one integrated access and backhaul node, at least one cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service; associating, by the at least one integrated access and backhaul node, the at least one cell identifier of at least one upstream cell with at least one cell identifier of at least one integrated access and backhaul node to form at least one cell identifier pair; and send the at least one cell identifier pair and any additional cell identifier pairs received from subtending integrated access and backhaul node to at least one donor or upstream integrated access and backhaul nod.

[0096] In accordance with the example embodiments as described in the paragraphs above, perform each step of the preceding paragraph at each of a plurality of integrated access and backhaul nodes resulting in a topology table containing link-states.

[0097] In accordance with the example embodiments as described in the paragraphs above, wherein the at least one integrated access and backhaul node comprises at least a radio and a mobile termination function.

[0098] In accordance with the example embodiments as described in the paragraphs above, determine routes for forwarding packets between at least one user equipment serving integrated access and backhaul node and a core network or radio access network central unit.

[0099] In accordance with the example embodiments as described in the paragraphs above, the at least one processor is further configured to deter ine that a to ology change has occurred; and perform a routing update based on the topology change.

[00100] In accordance with the example embodiments as described in the paragraphs above, the at least one processor is further configured to perform topology management based on controlling integrated access and backhaul node connectivity.

[00101] In accordance with the example embodiments as described in the paragraphs above, the at least one processor is further configured to determine that a signal strength of at least one non-serving integrated access and backhaul node is comparable to a signal strength of a serving integrated access and backhaul node, wherein a minimum hop count of the at least one non-serving integrated access and backhaul node is lower than the minimum hop count of the serving integrated access and backhaul node; and perform hand over to the at least one non-serving integrated access and backhaul node.

[00102] In accordance with the example embodiments as described in the paragraphs above, the at least one processor is further configured to perform topology discovery for integrated access and backhaul to allow at least one central unit controlling at least one integrated access and backhaul node to determine a subtending topology structure.

[00103] Embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., an application specific integrated circuit), or a combination of software and hardware. In an example embodiment, the software (e.g., application logic, an instruction set) is maintained on any one of various conventional computer-readable media. In the context of this document, a“computer-readable medium” may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, with one example of a computer described and depicted, e.g., in Fig. 1. A computer-readable medium may comprise a computer-readable storage medium (e.g., memories 125, 155, 171 or other device) that may be any media or means that can contain, store, and/or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. A computer- readable storage medium does not comprise propagating signals.

[00104] If desired, the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined.

[00105] Although various aspects are set out above, other aspects comprise other combinations of features from the described embodiments, and not solely the combinations described above.

[00106] It is also noted herein that while the above describes example embodiments, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention.

[00107] Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

[00108] It is also noted herein that while the above describes example embodiments, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.

[00109] In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[00110] Embodiments may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[00111] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this Detailed Description are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims.

[00112] The foregoing description has provided byway of example and non-limiting examples a full and informative description of the best method and apparatus presently contemplated by the inventors for carrying out the invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention.

[00113] It should be noted that the terms "connected," "coupled," or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are "connected" or "coupled" together. The coupling or connection between the elements can be physical, logical, or a combination thereof. As employed herein two elements may be considered to be "connected" or "coupled" together by the use of one or more wires, cables and/or printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as several non-limiting and non- exhaustive examples.

[00114] Furthermore, some of the features of the preferred embodiments of this invention could be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles of the invention, and not in limitation thereof.

Claims

CLAIMS What is claimed is:

1. A method, comprising:

obtaining, by at least one integrated access and backhaul node, at least one cell identifier of at least one radio function at the at least one integrated access and backhaul node;

obtaining, by the at least one integrated access and backhaul node, at least one cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service;

associating, by the at least one integrated access and backhaul node, the at least one cell identifier of at least one upstream cell with at least one cell identifier of at least one integrated access and backhaul node to form at least one cell identifier pair; and

sending the at least one cell identifier pair and any additional cell identifier pairs received from at least one subtending integrated access and backhaul node to at least one donor or upstream integrated access and backhaul node.

2. The method of claim 1, further comprising:

performing each step of claim 1 at each of a plurality of integrated access and backhaul nodes resulting in a topology table containing link-states.

3. The method according to any of claims 1 to 2, wherein the at least one integrated access and backhaul node comprises at least a radio and a mobile termination function.

4. The method according to any of claims 1 to 3, further comprising:

determining routes for forwarding packets between at least one user equipment serving integrated access and backhaul node and a core network or radio access network central unit.

5. The method according to any of claims 1 to 4, further comprising:

determining that a topology change has occurred; and

performing a routing update based on the topology change.

6. The method according to any of claims 1 to 5, further comprising:

performing topology management based on controlling integrated access and backhaul node connectivity.

7. The method according to any of claims 1 to 6, further comprising:

determining that a signal strength of at least one non-serving integrated access and backhaul node is comparable to a signal strength of a serving integrated access and backhaul node, wherein a minimum hop count of the at least one non-serving integrated access and backhaul node is lower than the minimum hop count of the serving integrated access and backhaul node; and

performing hand over to the at least one non-serving integrated access and backhaul node.

8. The method according to any of claims 1 to 7, further comprising:

performing topology discovery for integrated access and backhaul to allow at least one central unit controlling at least one integrated access and backhaul node to determine a subtending topology structure.

9. The method according to any of claims 1 to 7, further comprising:

applying a layer 2 approach to integrated access and backhaul;

relaying at least one transport channel over multiple distributed unit hops to at least one donor that hosts the central unit for all subtending distributed units; and

creating a topology table containing all link associations.

10. The method according to any of claims 1 to 8, further comprising:

applying a connectivity service approach to integrated access and backhaul;

sending packets over self-backhaul hops that each constitute an end-to-end connectivity service between an integrated access and backhaul node mobile termination function and an integrated access and backhaul node-embedded user plane function.

11. The method according to any of claims 1 to 10, wherein a topology is distributed to at least one additional donor.

12. The method according to any of claims 1 to 11, further comprising:

sending cell identifier pairs using at least one of 3GPP R C, Fl or Xn interface messages.

13. An apparatus, comprising:

means for obtaining, by at least one integrated access and backhaul node function, at least one cell identifier of at least one radio function at the at least one integrated access and backhaul node

means for obtaining, by the at least one integrated access and backhaul node function, at least one distributed unit cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service;

means for associating, by the at least one integrated access and backhaul node function, the at least one cell identifier of at least one upstream cell with at least one cell identifier of at least one integrated access and backhaul node to form at least one cell identifier pair; and

means for sending the at least one cell identifier pair and any additional cell identifier pairs received from at least one subtending integrated access and backhaul node to at least one donor or upstream integrated access and backhaul node.

14. The apparatus of claim 13, further comprising:

means for performing each step performed by the apparatus of claim 11 at each of a plurality of integrated access and backhaul nodes resulting in a topology table containing link-states.

15. The apparatus according to any of claims 13 to 14, wherein the at least one integrated access and backhaul node comprises at least a radio and a mobile termination function.

16. The apparatus according to any of claims 13 to 15, further comprising:

means for determining routes for forwarding packets between at least one user equipment serving integrated access and backhaul node and a core network or radio access network central unit.

17. The apparatus according to any of claims 13 to 16, further comprising:

means for determining that a topology change has occurred; and

means for performing a routing update based on the topology change.

18. The apparatus according to any of claims 13 to 17, further comprising:

means for performing topology management based on controlling integrated access and backhaul node connectivity.

19. The apparatus according to any of claims 13 to 18, further comprising:

means for performing topology discovery for integrated access and backhaul to allow at least one central unit controlling at least one integrated access and backhaul node to determine a subtending topology structure.

20. A non-transitory computer readable medium encoded with instructions that, when executed by a computer, cause performance of a method comprising:

obtaining, by at least one integrated access and backhaul node function, at least one cell identifier of at least one radio function at the at least one integrated access and backhaul node;

obtaining, by the at least one integrated access and backhaul node function, at least one distributed unit cell identifier of at least one upstream cell that provides the at least one integrated access and backhaul node mobile termination function with service;

associating, by the at least one integrated access and backhaul node function, the at least one cell identifier of at least one upstream cell with at least one cell identifier of the at least one radio function at the at least one integrated access and backhaul node to form at least one cell identifier pair; and

sending the at least one cell identifier pair and any additional cell identifier pairs received from at least one subtending integrated access and backhaul node to at least one donor.