Patent Description:
Recent generation mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) architectures, are able to support a wider range of services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. In addition to supporting these kinds of more sophisticated services and devices, it is also proposed for newer generation mobile telecommunication systems to support less complex services and devices which make use of the reliable and wide ranging coverage of newer generation mobile telecommunication systems without necessarily needing to rely on the high data rates available in such systems.

Future wireless communications networks will therefore be expected to routinely and efficiently support communications with a wider range of devices associated with a wider range of data traffic profiles and types than current systems are optimised to support. For example it is expected future wireless communications networks will be expected to efficiently support communications with devices including reduced complexity devices, machine type communication (MTC) devices, high resolution video displays, virtual reality headsets and so on. Some of these different types of devices may be deployed in very large numbers, for example low complexity devices for supporting the "The Internet of Things", and may typically be associated with the transmissions of relatively small amounts of data with relatively high latency tolerance.

In view of this there is expected to be a desire for future wireless communications networks, for example those which may be referred to as <NUM> or new radio (NR) system / new radio access technology (RAT) systems, as well as future iterations / releases of existing systems, to efficiently support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles.

As radio technologies continue to improve, for example with the development of <NUM>, the possibility arises for these technologies to be used not only by infrastructure equipment to provide service to wireless communications devices in a cell, but also for interconnecting infrastructure equipment to provide a wireless backhaul. In view of this there is a need to ensure that a donor infrastructure equipment that is physically connected to the core network does not suffer from a "capacity crunch" when a large amount of data is being transmitted from various communications devices and infrastructure equipment to the core network via the donor infrastructure equipment.

<CIT> relates to relaying of communications by a mobile device in a communication system.

Non-patent document "<NPL>, extends the LTE architecture to enable dynamic relaying, while maintaining backward compatibility with LTE Release <NUM> user equipment, and without limiting the flexibility and reliability expected from relaying.

The present disclosure can help address or mitigate at least some of the issues discussed above as defined in the appended claims.

The network <NUM> includes a plurality of base stations <NUM> connected to a core network <NUM>. Each base station provides a coverage area <NUM> (i.e. a cell) within which data can be communicated to and from communications devices <NUM>.

Although each base station <NUM> is shown in <FIG> as a single entity, the skilled person will appreciate that some of the functions of the base station may be carried out by disparate, interconnected elements, such as antennas (or antennae), remote radio heads, amplifiers, etc. Collectively, one or more base stations may form a radio access network.

Data is transmitted from base stations <NUM> to communications devices <NUM> within their respective coverage areas <NUM> via a radio downlink. Data is transmitted from communications devices <NUM> to the base stations <NUM> via a radio uplink. The core network <NUM> routes data to and from the communications devices <NUM> via the respective base stations <NUM> and provides functions such as authentication, mobility management, charging and so on. Terminal devices may also be referred to as mobile stations, user equipment (UE), user terminal, mobile radio, communications device, and so forth.

Services provided by the core network <NUM> may include connectivity to the internet or to external telephony services. The core network <NUM> may further track the location of the communications devices <NUM> so that it can efficiently contact (i.e. page) the communications devices <NUM> for transmitting downlink data towards the communications devices <NUM>.

Base stations, which are an example of network infrastructure equipment, may also be referred to as transceiver stations, nodeBs, e-nodeBs, eNB, g-nodeBs, gNB and so forth. In this regard different terminology is often associated with different generations of wireless telecommunications systems for elements providing broadly comparable functionality. However, certain embodiments of the disclosure may be equally implemented in different generations of wireless telecommunications systems, and for simplicity certain terminology may be used regardless of the underlying network architecture. That is to say, the use of a specific term in relation to certain example implementations is not intended to indicate these implementations are limited to a certain generation of network that may be most associated with that particular terminology.

An example configuration of a wireless communications network which uses some of the terminology proposed for NR and <NUM> is shown in <FIG>. A 3GPP Study Item (Si) on New Radio Access Technology (NR) has been defined [<NUM>]. In <FIG> a plurality of transmission and reception points (TRPs) <NUM> are connected to distributed control units (DUs) <NUM>, <NUM> by a connection interface represented as a line <NUM>. Each of the TRPs <NUM> is arranged to transmit and receive signals via a wireless access interface within a radio frequency bandwidth available to the wireless communications network. Thus within a range for performing radio communications via the wireless access interface, each of the TRPs <NUM>, forms a cell of the wireless communications network as represented by a circle <NUM>. As such, wireless communications devices <NUM> which are within a radio communications range provided by the cells <NUM> can transmit and receive signals to and from the TRPs <NUM> via the wireless access interface. Each of the distributed units <NUM>, <NUM> are connected to a central unit (CU) <NUM> (which may be referred to as a controlling node) via an interface <NUM>. The central unit <NUM> is then connected to the a core network <NUM> which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network <NUM> may be connected to other networks <NUM>.

The TRPs <NUM> of <FIG> may in part have a corresponding functionality to a base station or eNodeB of an LTE network. Similarly the communications devices <NUM> may have a functionality corresponding to the UE devices <NUM> known for operation with an LTE network. It will be appreciated therefore that operational aspects of a new RAT network (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be different to those known from LTE or other known mobile telecommunications standards. However, it will also be appreciated that each of the core network component, base stations and communications devices of a new RAT network will be functionally similar to, respectively, the core network component, base stations and communications devices of an LTE wireless communications network.

In terms of broad top-level functionality, the core network <NUM> connected to the new RAT telecommunications system represented in <FIG> may be broadly considered to correspond with the core network <NUM> represented in <FIG>, and the respective central units <NUM> and their associated distributed units / TRPs <NUM> may be broadly considered to provide functionality corresponding to the base stations <NUM> of <FIG>. The term network infrastructure equipment / access node may be used to encompass these elements and more conventional base station type elements of wireless telecommunications systems. Depending on the application at hand the responsibility for scheduling transmissions which are scheduled on the radio interface between the respective distributed units and the communications devices may lie with the controlling node / central unit and / or the distributed units / TRPs. A communications device <NUM> is represented in <FIG> within the coverage area of the first communication cell <NUM>. This communications device <NUM> may thus exchange signalling with the first central unit <NUM> in the first communication cell <NUM> via one of the distributed units <NUM> associated with the first communication cell <NUM>.

It will further be appreciated that <FIG> represents merely one example of a proposed architecture for a new RAT based telecommunications system in which approaches in accordance with the principles described herein may be adopted, and the functionality disclosed herein may also be applied in respect of wireless telecommunications systems having different architectures.

Thus certain embodiments of the disclosure as discussed herein may be implemented in wireless telecommunication systems / networks according to various different architectures, such as the example architectures shown in <FIG> and <FIG>. It will thus be appreciated the specific wireless telecommunications architecture in any given implementation is not of primary significance to the principles described herein. In this regard, certain embodiments of the disclosure may be described generally in the context of communications between network infrastructure equipment / access nodes and a communications device, wherein the specific nature of the network infrastructure equipment / access node and the communications device will depend on the network infrastructure for the implementation at hand. For example, in some scenarios the network infrastructure equipment / access node may comprise a base station, such as an LTE-type base station <NUM> as shown in <FIG> which is adapted to provide functionality in accordance with the principles described herein, and in other examples the network infrastructure equipment may comprise a control unit / controlling node <NUM> and / or a TRP <NUM> of the kind shown in <FIG> which is adapted to provide functionality in accordance with the principles described herein.

A more detailed diagram of some of the components of the network shown in <FIG> is provided by <FIG>. In <FIG>, a TRP <NUM> as shown in <FIG> comprises, as a simplified representation, a wireless transmitter <NUM>, a wireless receiver <NUM> and a controller or controlling processor <NUM> which may operate to control the transmitter <NUM> and the wireless receiver <NUM> to transmit and receive radio signals to one or more UEs <NUM> within a cell <NUM> formed by the TRP <NUM>. As shown in <FIG>, an example UE <NUM> is shown to include a corresponding transmitter <NUM>, a receiver <NUM> and a controller <NUM> which is configured to control the transmitter <NUM> and the receiver <NUM> to transmit signals representing uplink data to the wireless communications network via the wireless access interface formed by the TRP <NUM> and to receive downlink data as signals transmitted by the transmitter <NUM> and received by the receiver <NUM> in accordance with the conventional operation.

The transmitters <NUM>, <NUM> and the receivers <NUM>, <NUM> (as well as other transmitters, receivers and transceivers described in relation to examples and embodiments of the present disclosure) may include radio frequency filters and amplifiers as well as signal processing components and devices in order to transmit and receive radio signals in accordance for example with the <NUM>/NR standard. The controllers <NUM>, <NUM> (as well as other controllers described in relation to examples and embodiments of the present disclosure) may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc., configured to carry out instructions which are stored on a computer readable medium, such as a non-volatile memory. The processing steps described herein may be carried out by, for example, a microprocessor in conjunction with a random access memory, operating according to instructions stored on a computer readable medium.

As shown in <FIG>, the TRP <NUM> also includes a network interface <NUM> which connects to the DU <NUM> via a physical interface <NUM>. The network interface <NUM> therefore provides a communication link for data and signalling traffic from the TRP <NUM> via the DU <NUM> and the CU <NUM> to the core network <NUM>.

The interface <NUM> between the DU <NUM> and the CU <NUM> is known as the F1 interface which can be a physical or a logical interface. The F1 interface <NUM> between CU and DU may operate in accordance with specifications 3GPP TS <NUM> and 3GPP TS <NUM>, and may be formed from a fibre optic or other wired high bandwidth connection. In one example the connection <NUM> from the TRP <NUM> to the DU <NUM> is via fibre optic. The connection between a TRP <NUM> and the core network <NUM> can be generally referred to as a backhaul, which comprises the interface <NUM> from the network interface <NUM> of the TRP10 to the DU <NUM> and the F1 interface <NUM> from the DU <NUM> to the CU <NUM>.

Example arrangements of the present technique can be formed from a wireless communications network corresponding to that shown in <FIG> or <FIG>, as shown in <FIG> provides an example in which cells of a wireless communications network are formed from infrastructure equipment which are provided with an Integrated Access and Backhaul (IAB) capability. The wireless communications network <NUM> comprises the core network <NUM> and a first, a second, a third and a fourth communications device (respectively <NUM>, <NUM>, <NUM> and <NUM>) which may broadly correspond to the communications devices <NUM>, <NUM> described above.

The wireless communications network <NUM> comprises a radio access network, comprising a first infrastructure equipment <NUM>, a second infrastructure equipment <NUM>, a third infrastructure equipment <NUM>, and a fourth infrastructure equipment <NUM>. Each of the infrastructure equipment provides a coverage area (i.e. a cell, not shown in <FIG>) within which data can be communicated to and from the communications devices <NUM> to <NUM>. For example, the fourth infrastructure equipment <NUM> provides a cell in which the third and fourth communications devices <NUM> and <NUM> may obtain service. Data is transmitted from the fourth infrastructure equipment <NUM> to the fourth communications device <NUM> within its respective coverage area (not shown) via a radio downlink. Data is transmitted from the fourth communications device <NUM> to the fourth infrastructure equipment <NUM> via a radio uplink.

The infrastructure equipment <NUM> to <NUM> in <FIG> may correspond broadly to the TRPs <NUM> of <FIG> and <FIG>.

The first infrastructure equipment <NUM> in <FIG> is connected to the core network <NUM> by means of one or a series of physical connections. The first infrastructure equipment <NUM> may comprise the TRP <NUM> (having the physical connection <NUM> to the DU <NUM>) in combination with the DU <NUM> (having a physical connection to the CU <NUM> by means of the F1 interface <NUM>) and the CU <NUM> (being connected by means of a physical connection to the core network <NUM>).

However, there is no direct physical connection between any of the second infrastructure equipment <NUM>, the third infrastructure equipment <NUM>, and the fourth infrastructure equipment <NUM> and the core network <NUM>. As such, it may be necessary (or, otherwise determined to be appropriate) for data received from a communications device (i.e. uplink data), or data for transmission to a communications device (i.e. downlink data) to be transmitted to or from the core network <NUM> via other infrastructure equipment (such as the first infrastructure equipment <NUM>) which has a physical connection to the core network <NUM>, even if the communications device is not currently served by the first infrastructure equipment <NUM> but is, for example, in the case of the wireless communications device <NUM>, served by the fourth infrastructure equipment <NUM>.

The second, third and fourth infrastructure equipment <NUM> to <NUM> in <FIG> may each comprise a TRP, broadly similar in functionality to the TRPs <NUM> of <FIG>.

In some arrangements of the present technique, one or more of the second to fourth infrastructure equipment <NUM> to <NUM> in <FIG> may further comprise a DU <NUM>, and in some arrangements of the present technique, one or more of the second to fourth infrastructure equipment <NUM> to <NUM> may comprise a DU and a CU.

In some arrangements of the present technique, the CU <NUM> associated with the first infrastructure equipment <NUM> may perform the function of a CU not only in respect of the first infrastructure equipment <NUM>, but also in respect of one or more of the second, the third and the fourth infrastructure equipment <NUM> to <NUM>.

In order to provide the transmission of the uplink data or the downlink data between a communications device and the core network, a route is determined by any suitable means, with one end of the route being an infrastructure equipment physically connected to a core network and by which uplink and downlink traffic is routed to or from the core network.

In the following, the term 'node' is used to refer to an entity or infrastructure equipment which forms a part of a route for the transmission of the uplink data or the downlink data.

An infrastructure equipment which is physically connected to the core network and operated in accordance with an example arrangement may provide communications resources to other infrastructure equipment and so is referred to as a 'donor node'. An infrastructure equipment which acts as an intermediate node (i.e. one which forms a part of the route but is not acting as a donor node) is referred to as a 'relay node'. It should be noted that although such intermediate node infrastructure equipment act as relay nodes on the backhaul link, they may also provide service to communications devices. The relay node at the end of the route which is the infrastructure equipment controlling the cell in which the communications device is obtaining service is referred to as an 'end node'.

In the wireless network illustrated in <FIG>, each of the first to fourth infrastructure equipment <NUM> to <NUM> may therefore function as nodes. For example, a route for the transmission of uplink data from the fourth communications device <NUM> may consist of the fourth infrastructure equipment <NUM> (acting as the end node), the third infrastructure equipment <NUM> (acting as a relay node), and the first infrastructure equipment <NUM> (acting as the donor node). The first infrastructure <NUM>, being connected to the core network <NUM>, transmits the uplink data to the core network <NUM>.

For clarity and conciseness in the following description, the first infrastructure equipment <NUM> is referred to below as the 'donor node', the second infrastructure equipment <NUM> is referred to below as 'Node <NUM>', the third infrastructure equipment <NUM> is referred to below as 'Node <NUM>' and the fourth infrastructure equipment <NUM> is referred to below as 'Node <NUM>'.

For the purposes of the present disclosure, the term 'upstream node' is used to refer to a node acting as a relay node or a donor node in a route, which is a next hop when used for the transmission of data via that route from a wireless communications device to a core network. Similarly, 'downstream node' is used to refer to a relay node from which uplink data is received for transmission to a core network. For example, if uplink data is transmitted via a route comprising (in order) the Node <NUM><NUM>, the Node <NUM><NUM> and the donor node <NUM>, then the donor node <NUM> is an upstream node with respect to the Node <NUM><NUM>, and the Node <NUM><NUM> is a downstream node with respect to the Node <NUM><NUM>.

More than one route may be used for the transmission of the uplink data from a given communications device; this is referred to herein as 'multi-connectivity'. For example, the uplink data transmitted by the wireless communications device <NUM> may be transmitted either via the Node <NUM><NUM> and the Node <NUM><NUM> to the donor node <NUM>, or via the Node <NUM><NUM> and the Node <NUM><NUM> to the donor node <NUM>.

In the following description, example arrangements are described in which each of the nodes is an infrastructure equipment; the present disclosure is not so limited. A node may comprise at least a transmitter, a receiver and a controller. In some arrangements of the present technique, the functionality of a node (other than the donor node) may be carried out by a communications device, which may be the communications device <NUM> (of <FIG>) or <FIG> (of <FIG>), adapted accordingly. As such, in some arrangements of the present technique, a route may comprise one or more communications devices. In other arrangements, a route may consist of only a plurality of infrastructure equipment.

In some arrangements of the present technique, an infrastructure equipment acting as a node may not provide a wireless access interface for the transmission of data to or by a communications device other than as part of an intermediate transmission along a route.

In some arrangements of the present technique, a route is defined considering a wireless communications device (such as the wireless communications device <NUM>) as the start of a route. In other arrangements a route is considered to start at an infrastructure equipment which provides a wireless access interface for the transmission of the uplink data by a wireless communications device.

Each of the first infrastructure equipment acting as the donor node <NUM> and the second to fourth infrastructure equipment acting as the Nodes <NUM>-<NUM><NUM>-<NUM> may communicate with one or more other nodes by means of an inter-node wireless communications link, which may also be referred to as a wireless backhaul communications links. For example, <FIG> illustrates four inter-node wireless communications links <NUM>, <NUM>, <NUM>, <NUM>.

Each of the inter-node wireless communications links <NUM>, <NUM>, <NUM>, <NUM> may be provided by means of a respective wireless access interface. Alternatively, two or more of the inter-node wireless communications links <NUM>, <NUM>, <NUM>, <NUM> may be provided by means of a common wireless access interface and in particular, in some arrangements of the present technique, all of the inter-node wireless communications links <NUM>, <NUM>, <NUM>, <NUM> are provided by a shared wireless access interface.

A wireless access interface which provides an inter-node wireless communications link may also be used for communications between an infrastructure equipment (which may be a node) and a communications device which is served by the infrastructure equipment. For example, the fourth wireless communications device <NUM> may communicate with the infrastructure equipment Node <NUM><NUM> using the wireless access interface which provides the inter-node wireless communications link <NUM> connecting the Node <NUM><NUM> and the Node <NUM><NUM>.

The wireless access interface(s) providing the inter-node wireless communications links <NUM>, <NUM>, <NUM>, <NUM> may operate according to any appropriate specifications and techniques. In some arrangements of the present technique, a wireless access interface used for the transmission of data from one node to another uses a first technique and a wireless access interface used for the transmission of data between an infrastructure equipment acting as a node and a communications device may use a second technique different from the first. In some arrangements of the present technique, the wireless access interface(s) used for the transmission of data from one node to another and the wireless access interface(s) used for the transmission of data between an infrastructure equipment and a communications device use the same technique.

Examples of wireless access interface standards include the third generation partnership project (3GPP)-specified GPRS/EDGE ("<NUM>"), WCDMA (UMTS) and related standards such as HSPA and HSPA+ ("<NUM>"), LTE and related standards including LTE-A ("<NUM>"), and NR ("<NUM>"). Techniques that may be used to provide a wireless access interface include one or more of TDMA, FDMA, OFDMA, SC-FDMA, CDMA. Duplexing (i.e. the transmission over a wireless link in two directions) may be by means of frequency division duplexing (FDD) or time division duplexing (TDD) or a combination of both.

In some arrangements of the present technique, two or more of the inter-node wireless communications links <NUM>, <NUM>, <NUM>, <NUM> may share communications resources. This may be because two or more of the inter-node wireless communications links <NUM>, <NUM>, <NUM>, <NUM> are provided by means of a single wireless access interface or because two or more of the inter-node wireless communications links <NUM>, <NUM>, <NUM>, <NUM> nevertheless operate simultaneously using a common range of frequencies.

The nature of the inter-node wireless communications links <NUM>, <NUM>, <NUM>, <NUM> may depend on the architecture by which the wireless backhaul functionality is achieved.

A new study item on Integrated Access and Backhaul for NR [<NUM>] has been approved. Several requirements and aspects for the integrated access and wireless backhaul for NR to address are discussed in [<NUM>], which include:.

The stated objective of the study detailed in [<NUM>] is to identify and evaluate potential solutions for topology management for single-hop/multi-hop and redundant connectivity, route selection and optimisation, dynamic resource allocation between the backhaul and access links, and achieving high spectral efficiency while also supporting reliable transmission.

<FIG> shows the scenario presented in [<NUM>], where a backhaul link is provided from cell site A <NUM> to cells B <NUM> and C <NUM> over the air. It is assumed that cells B <NUM> and C <NUM> have no wired backhaul connectivity. Considering the CU/DU split architecture in NR as described above, it can be assumed that all of cells A <NUM>, B <NUM> and C <NUM> have a dedicated DU unit and are controlled by the same CU.

Several architecture requirements for IAB are laid out in [<NUM>]. These include the support for multiple backhaul hops, that topology adaptation for physically fixed relays shall be supported to enable robust operation, minimisation of impact to core network specifications, consideration of impact to core networking signalling load, and Release <NUM> NR specifications should be reused as much as possible in the design of the backhaul link, with enhancements considered.

<FIG> is reproduced from [<NUM>], and shows an example of a wireless communications system comprising a plurality of IAB-enabled nodes, which may for example be TRPs forming part of an NR network. These comprise an IAB donor node <NUM> which has a connection to the core network, two IAB nodes (a first IAB node <NUM> and a second IAB node <NUM>) which have backhaul connections to the IAB donor node <NUM>, and a third IAB node <NUM> (or end IAB node) which has a backhaul connection to each of the first IAB node <NUM> and the second IAB node <NUM>. Each of the first IAB node <NUM> and third IAB node <NUM> have wireless access connections to UEs <NUM> and <NUM> respectively. As shown in <FIG>, originally the third IAB node <NUM> may communicate with the IAB donor node <NUM> via the first IAB node <NUM>. After the second IAB node <NUM> emerges, there are now two candidate routes from the third IAB node <NUM> to the IAB donor node <NUM>; via the first IAB node <NUM> and via the new second IAB node <NUM>. The new candidate route via the second IAB node <NUM> will play an important role when there is a blockage in the first IAB node <NUM> to IAB donor node <NUM> link. Hence, knowing how to manage the candidate routes efficiently and effectively is important to ensure timely data transmission between relay nodes, especially when considering the characteristics of wireless links.

In the case that the link between the first IAB node <NUM> and the third IAB node <NUM> is deteriorating, or the first IAB node <NUM> becomes overloaded, one of the nodes in the system (this could be the donor node <NUM> or the first IAB node <NUM> itself) will need to make a decision to change the route from the third IAB node <NUM> to the IAB donor node <NUM> from that via the first IAB node <NUM> to that via the second IAB node <NUM>.

In <FIG>, only the IAB Donor gNB <NUM> has a fixed line backhaul into the core network. It should be assumed in this case that the traffic from all the UEs <NUM> within the third IAB node's <NUM> coverage is backhauled firstly to the first IAB node <NUM>. This backhaul link must compete for capacity on the component carrier serving the first IAB Node <NUM> with all the UEs <NUM> within the coverage area of the first IAB Node <NUM>. In the relevant art, the first IAB Node <NUM> in such a system as that of <FIG> is called a "hop" - it relays communications between the end (third) IAB node <NUM> and the donor IAB node <NUM>. The backhaul link to the first IAB Node <NUM> requires enough capacity to support the traffic from all the UEs <NUM>, bearing in mind that some of these may have stringent quality of service (QoS) requirements that translate into high traffic intensities.

Various architectures have been proposed in order to provide the IAB functionality. The below described embodiments of the present technique are not restricted to a particular architecture. However, a number of candidate architectures which have been considered in, for example, 3GPP document [<NUM>] are described below.

<FIG> illustrates one possible architecture, sometimes referred to as "Architecture 1a", by which the donor Node <NUM>, the Node <NUM><NUM> and the Node <NUM><NUM> may provide a wireless backhaul to provide connectivity for the UEs <NUM>, <NUM>, <NUM>.

In <FIG>, each of the infrastructure equipment acting as an IAB nodes <NUM>, <NUM> and the donor node <NUM>, includes a distributed unit (DU) <NUM>, <NUM>, <NUM> which communicates with the UEs <NUM>, <NUM>, <NUM> and (in the case of the DUs <NUM>, <NUM> associated with the donor node <NUM> and the Node <NUM><NUM>) with the respective downstream IAB nodes <NUM>, <NUM>. Each of the IAB nodes <NUM>, <NUM> (not including the donor node <NUM>) includes a mobile terminal (MT) <NUM>, <NUM>, which includes a transmitter and receiver (not shown) for transmitting and receiving data to and from the DU of an upstream IAB node and an associated controller (not shown). The inter-node wireless communications links <NUM>, <NUM> may be in the form of new radio (NR) "Uu" wireless interface. The mobile terminals <NUM>, <NUM> may have substantially the same functionality as a UE, at least at the access stratum (AS) layer. Notably, however, an MT may not have an associated subscriber identity module (SIM) application; a UE may be conventionally considered to be the combination of an MT and a SIM application.

The Uu wireless interfaces used by IAB nodes to communicate with each other may also be used by UEs to transmit and receive data to and from the DU of the upstream IAB node. For example, the Uu interface <NUM> which is used by the Node <NUM><NUM> for communication with the donor node <NUM> may also be used by the UE <NUM> to transmit and receive data to and from the donor node <NUM>.

Similarly, an end node (such as the Node <NUM><NUM>) may provide a Uu wireless interface <NUM> for the fourth UE <NUM> to communicate with the DU <NUM> of the Node <NUM><NUM>.

Alternative candidate architectures for the provision of IAB are provided in <FIG>, sometimes referred to as "Architectures 2a and 2b" respectively. In both <FIG>, each IAB node includes a gNB function, providing a wireless access interface for the use of downstream IAB nodes and wireless communications devices.

<FIG> differs from <FIG> in that, in <FIG>, PDU sessions are connected end-on-end to form the wireless backhaul; in <FIG>, PDU sessions are encapsulated so that each IAB node may establish an end-to-end PDU session which terminates at the IAB donor node <NUM>.

Given the vulnerable characteristics of wireless links, and considering multi-hops on the backhaul link, topology adaptation should be considered in the case that blockages or congestion occur in the backhaul link considering a given hop. It is therefore imperative to maximise the spectral efficiency of the backhaul link in order to maximise its capacity. Embodiments of the present technique seek to address the route change procedure; i.e. how, following a decision on a route change procedure, to carry out the route change procedure, hence enabling an efficient topology management.

There are many challenges to overcome and aspects to consider when providing such route change procedure solutions. Firstly, it must be determined how problems with routes are detected and how measurement reports and/or assistance information may be used to decide when routes should be changed with respect to the intermediate nodes. Such problems may include link quality deterioration of the route as a whole or at one or more of the nodes on the route, traffic loads at one or more of the nodes on the route, or capacity issues or a node status at one or more of the nodes on the route, such as a buffer status or a power headroom status. Secondly, the way in which route selection criteria and decision making must be determined. This includes the route selection meeting any QoS requirements, the securing of capacity, reserving of resources, admission control requirements and means by which the route can be adapted or simplified. Thirdly, it must be determined how the selected links or updated routes are indicated to the relevant nodes in the system. For example, an indication of a route change may be provided to all or a part of intermediate nodes on both the old route and the new route.

As described above with respect to <FIG>, different IAB architectures are proposed. Depending on the architecture, the route reselection and change may require different procedures (i.e. message flows). For example, this may depend on whether or not the intermediate nodes have an RRC layer. As described above with relation to <FIG>, one of the nodes in a system will need to make a decision to change a route between two nodes when the link between these nodes is deteriorating, or one of the nodes becomes overloaded. Embodiments of the present technique seek to provide solutions to how the signalling to realise this procedure may be designed.

<FIG> shows a part schematic, part message flow diagram of communications in a wireless communications network <NUM> in accordance with embodiments of the present technique. The wireless communications network <NUM> comprises a plurality of infrastructure equipment <NUM>, <NUM>, <NUM>, <NUM> each being configured to communicate with one or more others of the infrastructure equipment <NUM>, <NUM>, <NUM>, <NUM> via a backhaul communications link <NUM>, one or more of the infrastructure equipment <NUM>, <NUM>, <NUM>, <NUM> each being configured to communicate with one or more communications devices <NUM> via an access link <NUM>.

A first of the infrastructure equipment <NUM> is configured to act as a donor node connected to a core network part <NUM> of the wireless communications network <NUM> and comprises transceiver circuitry 1002a and controller circuitry 1002b configured in combination to receive <NUM>, at the first infrastructure equipment <NUM>, signals representing data from a second of the infrastructure equipment <NUM> over a first communications path via one or more others of the infrastructure equipment acting as relay nodes <NUM>, and to receive <NUM> assistance information (and/or measurement reports) from at least one of the second infrastructure equipment <NUM> and the one or more other infrastructure equipment acting as the relay nodes <NUM>, <NUM>, wherein one of the first infrastructure equipment <NUM> and the one or more other infrastructure equipment acting as the relay nodes <NUM> is configured to determine <NUM>, in the case that the assistance information (and/or measurement reports) satisfies a trigger condition, that the second infrastructure equipment <NUM> should communicate with the first infrastructure equipment <NUM> over a second communications path via one or more other of the infrastructure equipment acting as relay nodes <NUM>, the second communications path being different to the first communications path, and to transmit <NUM> a route change command to the second infrastructure equipment <NUM> indicating that the second infrastructure equipment <NUM> should communicate with the first infrastructure equipment <NUM> over the second communications path instead of the first communications path, wherein the first infrastructure equipment <NUM> is configured to communicate <NUM> with the second infrastructure equipment <NUM> over the second communications path.

The trigger of the route change, for example referring to the example of <FIG>, the route may change from the third IAB node <NUM> - the first IAB node <NUM> - the IAB donor node <NUM> to the third IAB node <NUM> - the second IAB node <NUM> - the IAB donor node <NUM>, could be from a link degradation, or a node blockage etc. So, the data transfer needs to change from the first IAB node <NUM> to the second IAB node <NUM>. In relation to the example wireless communications network <NUM> of <FIG>, the IAB donor node <NUM> is equivalent to the first infrastructure equipment <NUM>, the first IAB node <NUM> is equivalent to the infrastructure equipment acting as the relay node <NUM>, the second IAB node <NUM> is equivalent to the infrastructure equipment acting as the relay node <NUM>, and the third IAB node <NUM> is equivalent to the second infrastructure equipment <NUM>. The route change decision can be made by a central node e.g. the IAB donor node <NUM>.

In architecture 1a, as shown in <FIG>, the RRC layer resides in the IAB donor, so in principle, the RRC signalling will be transmitted via the F1 interface between CU and DU (labelled with reference numerals <NUM> and <NUM> in the example of <FIG>) and will be forwarded hop by hop physically. In other words, the first infrastructure equipment may be configured to transmit the route change command to the second infrastructure equipment using an F1 interface. Furthermore, the first infrastructure equipment may be configured to transmit, subsequent to determining that the second infrastructure equipment should communicate with the first infrastructure equipment over the second communications path, signalling associated with the route change command to each of the infrastructure equipment on the first communications path and to each of the infrastructure equipment on the second communications path.

The trigger of the route change may be one of a number of factors, such as:.

In other words, the trigger condition comprises a determination, based on the assistance information (and/or measurement reports), that a link quality between two of the infrastructure equipment on the first communications path is below a threshold link quality. Alternatively, the trigger condition comprises a determination, based on the assistance information, that at least one quality of service requirement cannot be guaranteed by at least one of the infrastructure equipment on the first communications path. Alternatively, the trigger condition comprises a determination, based on the assistance information, that a load at one of the infrastructure equipment on the first communications path is above a threshold load. Alternatively, the trigger condition comprises a determination, based on the assistance information, that at least one route selection criterion has changed.

Once the route change decision has been made, the route change procedure should be assisted by a central node, i.e. the donor node, and the route change signalling may need to be forwarded layer by layer physically. The route change procedure may be that as shown in <FIG>, which is a message flow diagram illustrating an example of a route change procedure via the F1 interface in accordance with embodiments of the present disclosure.

In <FIG>, the end IAB node <NUM> is that which needs to change the route from one to the other (e.g. the third IAB node <NUM> of <FIG> or second infrastructure equipment <NUM> of <FIG>). The source IAB node <NUM> is that which is on the original route, and needs to be changed (e.g. the first IAB node <NUM> of <FIG> or the infrastructure equipment acting as the relay node <NUM> of <FIG>). The destination IAB node <NUM> is that which is on the destination route, and needs to be changed to (e.g. the second IAB node <NUM> of <FIG> or the infrastructure equipment acting as the relay node <NUM> of <FIG>). The donor node/central lAB node <NUM> is that which made the route change decision and/or assisted the route change procedure (e.g. the IAB donor node <NUM> of <FIG> or first infrastructure equipment <NUM> of <FIG>). The procedure shown in <FIG> is as follows:.

It should be noted that the donor node may need to access the core network for some additional assistance information in order to finish the route change procedure. It should also be noted that the data path and control data path could be different. There could be a special control signalling route to deliver the route change signalling for example, in order to guarantee the signalling reliability.

In terms of the measurement information/assistance information received at the donor node from various other nodes in the system, this information may include indications of:.

The donor node may itself make measurements, which may be taken into account in the route change decision of step <NUM>. These may include:.

The NR backhaul link in future implantations may make use of new wireless technologies like massive MIMO/beamforming and mmWave. In other words, if beamforming is used with respect to embodiments of the present technique, one or more of the plurality of infrastructure equipment are configured to communicate with one or more others of the infrastructure equipment via the backhaul communications link using one or more beams in which power of each of the signals is focussed, each of the one or more beams being separately identifiable and forming a directional bias with respect to the one or more of the plurality of infrastructure equipment. It is worth noting the following characteristics of the NR wireless link:.

In general, multi-hopping relay networks have various links between nodes, and various combinations of routes. As a result, much signalling is likely to be redundant. It is important to keep the volume of signalling at a moderate level, which can be achieved through the strategy of candidate link reduction.

Firstly, the type of backhaul link must be classified. A first type of link is one which is stable with a large capacity, and this is referred to as a "highway link" in this disclosure. A second type of link is one which is more unstable/volatile, and might be a bottleneck in terms of capacity. This is referred to in this disclosure as a "normal link" or a "local link".

Secondly, the strategy of topology is considered, where highway links and local links may be mixed. The number of hops between an end point node and the entrance of a highway link could be minimised. Optionally, although measurement reports are not transmitted, the highway link may be regularly checking the link status (e.g. using a loop back test), and may redirect to alternative routes if necessary.

The highway link should be one of a default link or a high priority link in an IAB network in terms of having a stable link quality, a large capacity and a low latency. <FIG> shows an example of how a highway link may be used. The connection between the UE and the donor gNodeB may be more than one. The left hand side highway route has a shorter path to the entrance of the highway. The UE and any intermediate nodes may narrow down the measurement reports based on the entrance of the highway. In other words, the measurement reports related to the highway could be omissible or could be less frequent.

If a highway link is used with respect to embodiments of the present technique, wherein if the first communications path is either of a default communications path or a high priority default communications path, the first infrastructure equipment is configured to receive less assistance information from the infrastructure equipment on the first communications path than if the first communications path was not either of a default communications path or a high priority communications path.

In architecture 2a, as shown in <FIG>, the RRC layer resides in the gNodeB part of the IAB node, so in principle, an RRC layer on each IAB node will be responsible for the route change procedure. In other words, the one of the one or more other infrastructure equipment acting as the relay nodes may be configured to transmit the route change command to the second infrastructure equipment using radio resource control, RRC, signalling. Furthermore, any of the infrastructure equipment on the first communications path and the infrastructure equipment on the second communications path may be configured to determine that the second infrastructure equipment should communicate with the first infrastructure equipment over the second communications path.

The route change procedure may be that as shown in <FIG>, which is a message flow diagram illustrating an example of a route change procedure using radio resource control (RRC) signalling in accordance with embodiments of the present disclosure. Much of the procedure shown by <FIG> is equivalent to that of <FIG>, so for conciseness, <FIG> should be referred to for the understanding of <FIG>.

However, the major differences between the procedures of <FIG> and <FIG>, aside from the source IAB node managing the procedure rather than the donor IAB node, lie in the steps of acknowledging (by the destination IAB node) the route handover request (step <NUM>) and the path switch process (step <NUM>). These are detailed below.

Step <NUM>: If the destination node accepts the route change request, the user plane function (UPF) in the source node will re-locate to the destination node as per the requirements of architecture 2a. In other words, any of the infrastructure equipment on the first communications path and the infrastructure equipment on the second communications path may be configured to control a user plane function, UPF, to be relocated from one of the infrastructure equipment on the first communications path to one of the infrastructure equipment on the second communications path.

Step <NUM>: This is the interaction with the core network (through the donor node), that creates a new interface between the destination node and the core network instead of the old interface between the source node and the core network. In other words, one of the infrastructure equipment on the second communications path may be configured to create a new access interface between the one of the infrastructure equipment on the second communications path and the core network part of the wireless communications network.

Several different topologies have been proposed for IAB, which are outlined in [<NUM>], which discusses the topologies generally without mentioning contents of measurement reports or assistance information. These topologies include:.

In the context of this disclosure, the definition of a hierarchy refers to a system in which IAB nodes are arranged with one or multiple hops via various other IAB nodes to the donor gNodeB. Embodiments of the present technique are applicable for any of the above topologies.

Multiple routing examples are also proposed for IAB, and shown in [<NUM>]. These include destination address based routing, and forwarding path based routing.

Forwarding path based routing as described in [<NUM>] is similar to the F1 interface based route change procedure as described in the present disclosure in relation to <FIG> above. The routing table may be configured in advance, especially for the uplink. In embodiments of the present technique, the donor gNodeB may collect all the information of links/nodes such as link quality, traffic load, etc. Then, the donor gNodeB will decide upon the route, and update the routing table accordingly. In addition, the gNodeB may indicate the switching time of the path switch, thus ensuring that the service disruption time or packet loss is minimized. In order to reduce the number of measurements reports, embodiments of the present technique introduce the highway link in order to reduce the degree of freedom for link selection.

Destination address based routing as described in [<NUM>] is similar to the RRC based route change procedure as described in the present disclosure in relation to <FIG> above. However, this destination address based routing as defined in [<NUM>] appears to be a connectionless type routing, like IP packet routing. In embodiments of the present disclosure, each intermediate node (or gNodeB) may carefully decide the routing table to meet the required QoS and service level. For example, the donor gNodeB may collect measurements of the candidate link qualities and capacities, and then the link which meets the necessary QoS is selected. Alternatively, intermediate nodes in the link may check the link quality and capacity between themselves and neighbor nodes (e.g. perform a loop back test). Then, the intermediate nodes themselves may decide to change the route to meet the QoS requirements.

<FIG> shows a flow diagram illustrating a process of communications in a communications system in accordance with embodiments of the present technique. The process shown by <FIG> is a method of controlling communications within a wireless communications network comprising a plurality of infrastructure equipment each being configured to communicate with one or more others of the infrastructure equipment via a backhaul communications link, one or more of the infrastructure equipment each being configured to communicate with one or more communications devices via an access link.

The method begins in step S1401. The method comprises, in step S1402, receiving, at a first of the infrastructure equipment acting as a donor node connected to a core network part of the wireless communications network, signals representing data from a second of the infrastructure equipment over a first communications path via one or more others of the infrastructure equipment acting as relay nodes. The process then moves to step S1403, which comprises receiving, at the first infrastructure equipment, assistance information from at least one of the second infrastructure equipment and the one or more other infrastructure equipment acting as the relay nodes. In step S1404, the method comprises one of the first infrastructure equipment and the one or more other infrastructure equipment acting as the relay nodes determines whether or not the assistance information satisfies a trigger condition. If not, then the method moves back to either of steps S1402 and S1403. However, if the assistance information does satisfy the trigger condition, then the method advances to step S1405. In step S1405, the process comprises determining, by the one of the first infrastructure equipment and the one or more other infrastructure equipment acting as the relay nodes in the case that the assistance information satisfies the trigger condition, that the second infrastructure equipment should communicate with the first infrastructure equipment over a second communications path via one or more other of the infrastructure equipment acting as relay nodes, the second communications path being different to the first communications path. The method then moves to step S1406, which comprises transmitting, by the one of the first infrastructure equipment and the one or more other infrastructure equipment acting as the relay nodes which determined that the second infrastructure equipment should communicate with the first infrastructure equipment over the second communications path, a route change command to the second infrastructure equipment indicating that the second infrastructure equipment should communicate with the first infrastructure equipment over the second communications path instead of the first communications path, and in step S1407, communicating, by the first infrastructure equipment, with the second infrastructure equipment over the second communications path. The process ends in step S1408.

Those skilled in the art would appreciate that the method shown by <FIG> may be adapted in accordance with embodiments of the present technique. For example, other intermediate steps may be included in the method, or the steps may be performed in any logical order.

Though embodiments of the present technique have been described largely by way of the example system shown in <FIG>, it would be clear to those skilled in the art that they could be equally applied to other systems, where for example there may be many more nodes or paths to choose from, or more hops between the donor and end nodes.

Those skilled in the art would also appreciate that such infrastructure equipment and/or wireless communications networks as herein defined may be further defined in accordance with the various arrangements and embodiments discussed in the preceding paragraphs. It would be further appreciated by those skilled in the art that such infrastructure equipment and wireless communications networks as herein defined and described may form part of communications systems other than those defined by the present invention.

Claim 1:
A method of controlling communications within a wireless communications network (<NUM>) comprising a plurality of infrastructure equipment (<NUM>, <NUM>, <NUM>, <NUM>) each being configured to communicate with one or more others of the infrastructure equipment via a backhaul communications link (<NUM>), one or more of the infrastructure equipment each being configured to communicate with one or more communications devices (<NUM>) via an access link (<NUM>), the method comprising
receiving (<NUM>), at a first of the infrastructure equipment (<NUM>) acting as a donor node connected to a core network part (<NUM>) of the wireless communications network, signals representing data from a second of the infrastructure equipment (<NUM>) over a first communications path via one or more others of the infrastructure equipment (<NUM>, <NUM>) acting as relay nodes,
receiving (<NUM>) via an F1 interface, at the first infrastructure equipment, assistance information from the second infrastructure equipment via the one or more other infrastructure equipment acting as the relay nodes,
determining (<NUM>), by one of the first infrastructure equipment and the one or more other infrastructure equipment acting as the relay nodes in the case that the assistance information satisfies a trigger condition, that the second infrastructure equipment should communicate with the first infrastructure equipment over a second communications path via one or more other of the infrastructure equipment acting as relay nodes, the second communications path being different to the first communications path,
transmitting (<NUM>) via the F1 interface, by the one of the first infrastructure equipment and the one or more other infrastructure equipment acting as the relay nodes which determined that the second infrastructure equipment should communicate with the first infrastructure equipment over the second communications path, a route change command to the second infrastructure equipment indicating that the second infrastructure equipment should communicate with the first infrastructure equipment over the second communications path instead of the first communications path, and
communicating (<NUM>), by the first infrastructure equipment, with the second infrastructure equipment over the second communications path.