Radio nodes for radio access networks and methods

Abstract

A second radio node is controlled by a first radio node, which in combination with the second radio node forms a wireless access interface for a cell of a radio access network part of a wireless communications network. The first radio node may have functionality corresponding to a combination of a CU and a DU according a 5G architecture and the second radio node may correspond to a TRP or Radio Unit, so that the combination of the first and the second radio nodes provides corresponding functionality a base station or gNB. The method comprises transmitting radio signals via the wireless access interface to one or more communications devices in the cell or to receive radio signals transmitted via the wireless access interface from the one or more communications devices, and receiving configuration information from the first radio node to form a wireless over-the-air, OTA, interface between the second radio node and another second radio node. The wireless OTA interface comprises an outward link for transmitting control information from the second radio node to the other second radio node and a reverse link for receiving control information by the second radio node from the other second radio node, the control information for supporting the transmission and / or reception of the radio signals via the wireless access interface by the one or more communications devices.

Description

[0001] RADIO NODES FOR RADIO ACCESS NETWORKS AND METHODS BACKGROUND

[0002] Field of Disclosure

[0003] The present disclosure relates to methods of operating second radio nodes (RUs, TRPs, RRHs) controlled by a first radio node (CU / DU) which in combination with the second radio node forms a wireless access interface for a cell of a radio access network part of a wireless communications network. The present disclosure also relates to radio access nodes and radio access networks. The present disclosure claims the Paris convention priority to European patent application EP25152640.6, filed 17 January 2025, the contents of which are incorporated herein by reference in their entirety.

[0004] Description of Related Art

[0005] The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.

[0006] Wireless communications networks can be generally thought of as a core network part and a radio network part. The radio network part includes radio access nodes which are generally referred to as base stations. As different applications and services evolve to support an ever-increasing range of devices associated with a wider range of data traffic profiles and types than existing systems, there is a need to involve correspondingly radio access networks to service this evolution. For example, it is expected future wireless communications networks will be expected efficiently to 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. Other types of device, for example supporting high-definition video streaming, may be associated with transmissions of relatively large amounts of data with relatively low latency tolerance. Other types of device, for example used for autonomous vehicle communications and for other critical applications, may be characterised by data that should be transmitted through the network with low latency and high reliability. A single device type might also be associated with different traffic profiles / characteristics depending on the application(s) it is running. For example, different consideration may apply for efficiently supporting data exchange with a smartphone when it is running a video streaming application (high downlink data) as compared to when it is running an Internet browsing application (sporadic uplink and downlink data) or being used for voice communications by an emergency responder in an emergency scenario (data subject to stringent reliability and latency requirements).

[0007] In view of this there is expected to be a desire for future wireless communications networks to have a radio network part comprising radio access nodes such as base stations with improved capabilities in order to meet the requirements of future services and devices such as that which evolves from a 5G or new radio (NR) systems / new radio access technology (RAT) systems.

[0008] SUMMARY OF THE DISCEOSURE

[0009] The present disclosure can help address or mitigate at least some of the issues discussed above.

[0010] Embodiments of the present technique can provide a method of operating a second radio node controlled by a first radio node which in combination with the second radio node forms a wireless access interfacefor a cell of a radio access network part of a wireless communications network. The first radio node may have functionality corresponding to a combination of a CU and a DU according a 5G architecture and the second radio node may correspond to a TRP or Radio Unit, so that the combination of the first and the second radio nodes provides corresponding functionality a base station or gNB. The method comprises transmitting radio signals via the wireless access interface to one or more communications devices in the cell or to receive radio signals transmitted via the wireless access interface from the one or more communications devices, and receiving configuration information from the first radio node to form a wireless over-the-air, OTA, interface between the second radio node and another second radio node. The wireless OTA interface comprises an outward link for transmitting control information from the second radio node to the other second radio node and a reverse link for receiving control information by the second radio node from the other second radio node, the control information for supporting the transmission and / or reception of the radio signals via the wireless access interface by the one or more communications devices.

[0011] Embodiments of the present technique can provide techniques for establishing a wireless OTA interface between second radio nodes or RUs which may form neighbouring cells to exchange control information for supporting wireless communications and radio control functions provided by the wireless communications network.

[0012] It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the present technology. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein like reference numerals designate identical or corresponding parts throughout the several views, and wherein:

[0015] Figure 1 schematically represents a wireless communications network illustrating architectural components which a radio access network part according new radio access technology (RAT) or 5G; Figure 2 is a schematic block diagram of parts forming a communications system of the wireless communications network of Figure 1 and which may also for part of certain embodiments of the present disclosure;

[0016] Figure 3A is a representation of a gNB DU and a gNB CU communicating via an Fl interface; Figure 3B is a schematic representation of a protocol stack operated respectively by the gNB DU and gNB CU shown in Figure 3A for communicating control plane data; and Figure 3C is a schematic representation of a protocol stack operated respectively by the gNB DU and gNB CU shown in Figure 3A for communicating user plane data;

[0017] Figure 4a schematically represents elements of a wireless communications system according to NR / 5G which are used to form a radio bearer for a communications device / UE, which include a virtual CU, a shared DU connected via a TRP, which forms a wireless access interface with the communications device / UE; and

[0018] Figure 4b schematically represents functions of a protocol stack for each of the elements shown in Figure 4a and which includes an additional security measure to encrypt data at certain protocol layers according to a technique disclosed in EP21155607.1;

[0019] Figure 5 schematically represents functions forming part of protocol stack for a control plane within a control unit (CU-CP) and a user plane within a control unit (CU-UP) and a distributed unit (DU) whencommunicating with two communications devices / UEs, in which an adaptation is made to distribute some protocol functions between the CU and the DU;

[0020] Figure 6a schematically represents elements of a wireless communications system which are used to form a radio bearer for a communications device / UE according to example embodiments of the present technique, which include a combined CU and DU connected to a radio unit, which forms a wireless access interface with the communications device / UE; and

[0021] Figure 6b schematically represents functions of a protocol stack for each of the elements shown in Figure 6a according to example embodiments;

[0022] Figure 7 is a schematic representation of a wireless communications network which includes a radio network part formed from radio network infrastructure equipment which include first radio nodes which include functions of a CU and DU of the wireless communications networks of Figures 1 to 5, and the second radio nodes which transmit and receive radio signals according to a wireless access interface provided by the radio access network according to example embodiments;

[0023] Figure 8 is a schematic representation of a parts of the wireless communications network shown in Figure 7 which illustrate a wireless interface forming an over-the-air (OTA) communications facility between second radio nodes, and an interface (Xninterface or similar, point to point wired or wireless) between the first radio nodes according to first embodiments in which the wireless OTA is formed from dedicated frequency resources;

[0024] Figure 9 is a schematic representation of a parts of the wireless communications network corresponding to that shown in Figure 7 which illustrate a wireless interface forming an over-the-air (OTA) communications facility between second radio nodes formed by a communications device / UE acting as a relay node according to second embodiments in which the wireless OTA is formed by the relay node; and Figure 10 is a schematic representation of a parts of the wireless communications network corresponding to that shown in Figure 7 which illustrate a wireless interface forming an over-the-air (OTA) communications facility between second radio nodes formed by one of the second radio nodes acting as a communications device / UE according to third embodiments in which the wireless OTA forms part of the wireless access interface of the radio access network.

[0025] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] As explained above, embodiments of the present technique can provide arrangements in which functionality of a gNB or base station are improved in order to support wireless communications between communications devices more efficiently. More particularly, embodiments provide enhancement to a 5G architecture, which may find application with other generations of a radio access network part of a mobile wireless communications system such as 6G. In order to get a better appreciation of advantages and aspects of the present technology, a more detailed description will be provided of current techniques using 5G technology.

[0027] New Radio Access Technology (5G)

[0028] An example configuration of a wireless communications network which uses some of the terminology proposed for and used in NR and 5G is shown in Figure 1. In Figure 1 a plurality of transmission and reception points (TRPs) 10 are connected to distributed control units (DUs) 40 by a connection interface represented as a line 16. Each of the TRPs 10 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 10, forms a cell of the wireless communications network as represented by a circle 12. As such, wireless communications devices 14, which are within a radio communications range provided by the cells 12 can transmit and receive signals to and from the TRPs 10 via the wireless access interface. Each of the distributed units 40 are connected to a central unit (CU) 44 (which may be referred to as acontrolling node) via an interface 46. The central unit 44 is then connected to the core network 20 via a connection interface 60, which may contain all other functions required to transmit data for communicating to and from the wireless communications devices or user equipment 14 and the core network 20 may be connected to other networks.

[0029] As will be appreciated by those acquainted with the wireless communications network according to 5G standard shown in Figure 1, the CU 44, DU 40 and TRPs 10 collectively perform functions which are conventionally performed by a network base station or, in accordance with 5G terminology, a gNB. According to the 5G architecture and a split of functions between the CU 44 and the DU 40, the terms CU and DU may be respectively referred to as a “gNB-CU” and a “gNB-DU” when it is appropriate to emphasise that the CU and the DU form part of a gNB. Similarly, the TRPs 10 of Figure 1 may in part have a corresponding functionality to a base station or eNodeB of an UTE network.

[0030] Also shown in Figure 1 and pertinent to the present technology is an interface 64 between CU’s 44. This interface 64 is known as the Xninterface and was introduced as part of 4G / ETE for gNB used to communicate with each other for example to exchange signalling information in respect of handover between UEs because typically the gNB’s using the Xninterface will be neighbouring cells. The present technology envisages the presence of an Xninterface between gNB functionality for future networks. The communications devices 14 may be referred to mobile terminals, terminals or user equipment (UE), which encompasses chip sets and have a functionality corresponding to the UE devices 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, 5G or other known variations and releases of these mobile telecommunications standards.

[0031] As explained in more detail below, depending on the application, the responsibility for scheduling transmissions on the radio interface between the respective DUs 44 and the communications devices 14 may lie with the controlling node / central unit (CU) and / or the distributed units (DU) / TRPs. A communications device 14 is represented in Figure 1 within the coverage area of the first communication cell 12. This communications device 14 may thus exchange signalling with a CU 44 in one cell 12 via one of the distributed units 40 / TRPs 10 associated with the cell 12.

[0032] Figure 2 provides detail of some of the components of the network shown in Figure 1. In Figure 2, a TRP 10 as shown in Figure 1 comprises, as a simplified representation, a wireless transmitter circuitry 30, a wireless receiver circuitry 72 and a controller or controlling processor 74 which may operate to control the transmitter circuitry 30 and the wireless receiver circuitry 32 to transmit and receive radio signals to one or more UEs 14 within a cell 12 formed by the TRP 10. As shown in Figure 2, an example communications device 14 (such as a UE) is shown to include a corresponding transmitter circuitry 76, a receiver circuitry 78 and a controller circuitry 80 which is configured to control the transmitter circuitry 76 and the receiver circuitry 78 to transmit signals representing uplink data to the wireless communications network via the wireless access interface formed by the TRP 10 and to receive downlink data as signals transmitted by the transmitter circuitry 70 and received by the receiver circuitry 72 in accordance with the conventional operation.

[0033] The transmitter circuitry 70, 76 and the receiver circuitry 72, 78 (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 5G / NR standard. Thecontroller processor / circuitry 74, 80 (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. The transmitters, the receivers and the controllers are schematically shown in Figure 2 as separate elements for ease of representation. However, it will be appreciated that the functionality of these elements can be provided in various different ways, for example using one or more suitably programmed programmable computer(s), or one or more suitably configured application-specific integrated circuit(s) / circuitry / chip(s) / chipset(s). As will be appreciated the infrastructure equipment / TRP / base station as well as the UE / communications device will in general comprise various other elements associated with its operating functionality.

[0034] As shown in Figure 2, the TRP 10 also includes a network interface, which connects to the DU 42 via a physical interface 16 to provide a communication link for data and signalling traffic from the TRP 10 via the DU 42 and the CU 44 to the core network 20.

[0035] The interface 46 between the DU 40 and the CU 44 is known as the F 1 interface which can be a physical or a logical interface. The Fl interface 46 between CU and DU may operate in accordance with specifications [1] and [2], and may be formed from a fibre optic or other wired or wireless high bandwidth connection. In one example the connection 16 from the TRP 10 to the DU 42 is via fibre optic. The connection between a TRP 10 and the core network 20 can be generally referred to as a backhaul, which comprises the interface 16 and the connection between the interface of the TRP 10 to the DU 40 and the Fl interface 46 from the DU 40 to the CU 44.

[0036] As will be appreciated by those acquainted with 5G architecture, the CU 44 is a logical node which hosts Radio Resource Control (RRC) protocols, Service Data Adaptation Protocols (SDAP) and Packet Data Convergence Protocols (PDCP) of a gNB. The CU 44 partly controls the operation of one or more DUs 40 and terminates the Fl interface 46 for the DUs that it controls. The DU 40 is a logical node which hosts Radio Eink Control (RLC), Medium Access Control (MAC) and Physical (PHY) layers of a gNB or en-gNB. The operation of the DU 40 is partly controlled by the CU 44 for which the DU 40 terminates the Fl interface 46.

[0037] Although not shown in Figures 1 or 2, it will be familiar to those acquainted with 5G architecture that the CU 44 may be further split into a CU-CP which performs the control plane functions of the CU 44 and a CU-UP which performs the user plane functions of the CU 44 (see for example, [3]). In more detail, the CU-CP is a logical node hosting an RRC protocol and a control plane part of a PDCP protocol of the CU 40 for the gNB or en-gNB. The CU-CP terminates an El interface connected with the CU-UP and an Fl-C interface connected with the DU 40. As will be appreciated, the Fl-C interface carries control plane signalling of the Fl interface 46.

[0038] The CU-UP is a logical node, which hosts a user plane part of a PDCP protocol of the CU 40 for an en-gNB. Alternatively, the CU-UP is a logical node, which hosts a user plane part of the PDCP protocol and an SDAP protocol of the CU 44 for a gNB. The CU-UP terminates an El interface connected with the CU-CP and an Fl-U interface connected with the DU 40. As will be appreciated, the Fl-U interface carries user plane signalling of the Fl interface 46.

[0039] In order to appreciate example embodiments, a protocol stack for forming a conventional Fl interface shown in Figure 1 and 2 will be explained with reference to Figure 3.In respect of a protocol stack, Figures 3a, 3b and 3c provide an illustration of processing performed by the elements shown in Figures 1 and 2 which form the packet data communications path 46 between the gNB-DU 40 and the gNB-CU 44 via the Fl interface 46. Control plane communications are considered separately to user plane data although in practice they form the same interface and are processed and transmitted by the same hardware equipment. As shown in Figure 3A communication is formed between the gNB DU 40 and a gNB CU 44 for the Fl interface 46. However, the control plane protocol stack to form this interface is shown in Figure 3B, and the user plane protocol stack for communicating the user data between the gNB-CU 44 and gNB-DU 40 is shown in Figure 3C. As shown in Figure 3B at the radio network layer, the control plane is formed by Fl Application Protocols (APs) 301a in the gNB-CU 44 and by Fl APs 301b in the gNB DU 40. As will be understood by those acquainted with the 5G Architecture, communication between a gNB-CU and a gNB DU is by IPv6 or IPv4 Internet protocols as specified in [4], This is shown in Figure 3B as an IP layer 302a in the gNB-CU 40 and an IP layer 302b in the gNB-DU 42 forming an IP communication interface 302c. A Stream Control Transmission Protocol (SCTP) layer of the protocol stack 304a, 304b, 304c controls end to end communication via the IP layer 302 including flow control and quality of service. The IP data is communicated between the gNB DU and gNB CU via logical data link layer 306a, 306b, 306c and the physical layer 308a, 308b, 308c.

[0040] In the user plane, the radio network layer is formed by RLC layer 320a, 320b to form the Fl interface for communicating use plane data 46. The protocol stack in the transport layer comprises a GPRS Tunnelling Protocol for user plane data (GTP-U) 322a, 322b, 322c, which controls communication of user plane data for roaming and home subscribers via a UDP layer 324a, 324b, 324c which controls communication of user plane data via an IP layer 326a, 326b, 326c. As with the control plane, the IP data is communicated between the gNB DU and gNB CU via logical data link layer 328a, 328b, 328c and the physical layer 330a, 330b, 330c.

[0041] Functionally respective layers in the CU and the DU for both the control plane and the user plane may be collectively referred to as a transport network layer 350a, 350b and radio network layer 352a, 352b respectively, which are typically represented together.

[0042] CU-DU Split Functions

[0043] As indicated above, the CU 40 and DU 42 are configured to execute gNB functionality. The allocation or splitting of gNB functions between the CU 40 and the DU 42 is discussed in [5], [6] and [7], Further Developments of Radio Network Architecture

[0044] As indicated above, the present technology concerns enhancement of the radio network architecture of a wireless communications network such as those which may be deployed in a 6G or further generations of wireless communications networks. As observed in our co-pending European patent application number EP21155607.1 a CU may be deployed with a plurality of DUs, (as shown in Figure 1), which may be operating to serve separate networks and may be deployed from different operators. That is to say, a mobile network operator (MNO) may wish to procure services from different entities which may themselves acquire network components from different sources / operators / implementers.

[0045] One proposal for a new architecture is to remove the CU - DU split. This may be achieved by not specifying the interface between CUs and DUs as it is currently specified to form the Fl interface, although the CU and DU functionality may be the same or similar to that which is currently proposed for 5G. This is because there are some issues with splitting the architecture of the functionality performed by the CU and DU and standardising the interface between the CU and the DU, which may have some disadvantages. For example, as identified in our co-pending European patent application numberEP21155607.1 filed 5 February 2021, the contents of which are incorporated herein by reference, a vertical stack which requires a split of the DU may create some security problems. It was envisaged that the CU and DU splits may result in the virtualised CU and DU being hosted physically by different service providers and hence our co-pending European patent application EP21155607.1 provided a new security in that if there is a DU, which is hosted separately for a common CU, then some proprietary protocol aspects such as radio resource management performed by the CU may be open to an operator of a different mobile network or infrastructure equipment, and therefore security may be compromised. According to this example, security is introduced for MAC and physical layer signalling at the DU as illustrated by the diagram of Figures 4a and 4b. This technology is explained in more detail in EP21155607.1. However, to appreciate advantages and improvements provided by example embodiments of the present technique, a brief explanation is provided below.

[0046] Figure 4a represents some components of a radio access network, which are configured to form a connection with a communications device / UE. That is to say that these components operate to support a radio bearer across the radio access network to the UE. As shown in Figure 4a, a virtual CU 44 is connected to a shared DU, which is connected to a TRP 10. The TRP 10 forms provides a wireless access interface for transmitting and receiving data to a UE 14. Figure 4b shows these components in more detail in respect of the functions of a protocol stack as these are implemented in each of these components.

[0047] As shown in Figure 4b, a scheduler 462 along with algorithms which provide a function for Radio Resource Management (RRM) can be considered as the “brain” of a base station or radio network access node. The scheduler 462 is normally one of the main distinguishing factors between the offerings from different network vendors and operators. However, if the scheduler or RRM algorithms of a base station are shared with another operator or service provider then the operators may lose their competitive advantage. In respect of a protocol stack, Figure 4b provides an illustration of processing performed by the elements shown in Figures 3b and 3c which form the packet data communications path (radio bearer) 400 to and from the UE 14. As will be understood by those acquainted with the 5G Architecture, PDCP is a sublayer 402a, 402b in the protocol stack for communicating data between entities which receives / transmits network layer traffic (TCP / IP traffic). A Data Radio Bearer (DRB) is a logical connection used inside a 5G protocol stack to carry data packet data units (PDUs). A Service Data Adaptation Protocol (SDAP) 404a, 404b, maps a quality of service (QoS) flow to and from a DRB at the PDCP sublayer 402a, 402b, in both downlink and uplink directions. As shown in Figure 4 therefore SDAP entities 404a, 404b in the UE 14 and the CU 44 respectively form an SDAP layer supported PDCP entities 402a, 402b forming the PDCP layer. Both the SDAP and the PDCP layers 404, 402 communicate data at these layers between the UE 14 and the CU 44. These layers 404, 402 are supported by operations of the TRP 10 and the DU 40. A transport layer 350a, 350b is formed by transport processors between the Shared DU 40 and the CU 44.

[0048] A radio link control (RLC) layer 406a, 406b controls communication via the radio link 406 between the shared DU 40 and the UE 14, which is supported by a MAC sub-layer 408a, 408b. Data is communicated using the RLC and MAC sub-layers 406, 408 via a physical (PHY) layer 410a, 410b, 410c and a transport layer 412a, 412b formed in the shared DU 40 and the TRP 10 as a wired connection 415 and between the TRP 10 and the UE 14 as a radio connection 410 according to established techniques of for example a 5G radio access network.

[0049] As will be appreciated the TRP 10 includes a RRH as mentioned above and therefore includes antennas forming a part of the PHY layer 410 to transmit / receive RF signals and the rest of PHY layer including baseband processing, resource allocation etc. will be implemented in the DU 40. Transport between theTRP 10 and the shared DU 40 could be based on traditional interfaces like CPRI or e-CPRI or Ethernet or similar. The RLC sub-layer 406, MAC sub-layer 408, and part of the PHY layer 410, the scheduler, and the RRM algorithms therefore virtually reside in the DU 40. The PDCP 404 and the SDAP 402 entities reside in the CU 44 and the UE 14.

[0050] In order to obviate a security problem for proprietary information associated with RRM messages produced by the scheduler 462 caused by the CU - DU split the technique disclosed in EP proposes that the baseband processing forming the elements of the protocol stack in the shared DU 40, which form a gNB with the TRP 10 are encrypted as represented by a shaded box 460. That is to say that all of the processing / processors forming the RLC sublayer 406b, the MAC sublayer 408b and the PHY layer 412b are encrypted, although note that the transport layer 412b may have its own encryption and 3GPP does not define transport. Correspondingly in the TRP 10, the PHY layer de-crypt messages and data received from the PHY layer 412a, 412b and the transport layer 415, and between the physical layer 410a, 410b as represented by a shaded box 470. Optionally therefore PDUs communicated between the TRP 10 may be encrypted according to a security tunnel 470, which may be implemented for example using IPSec. Furthermore, encryption or ciphering may be performed at the PHY layer 410 between the TRP 10 and the UE 14 as represented by a security tunnel 470.

[0051] According to the example illustrated by Figures 4a and 4b, encryption of the functions shown serves to secure sensitive information whilst allowing processes according to a protocol stack which may be used to implement functions of a gNB to be hosted on another operator’s or networks infrastructure equipment such as a DU. However, the need to encrypt these functions results from a split of the CU DU architecture. More generally an infrastructure equipment of a radio access network may be shared between network operators. Processors or processing which provides functions of a scheduler of RRM algorithms may be hosted on a shared infrastructure equipment. Accordingly, the encryption of the physical and transport layer 470 is required because of the split of the architecture between the DU and the CU for a radio access base station of the radio access network.

[0052] A similar technique, which mitigates a problem of the CU - DU split is disclosed in European patent application number EP22165697.8 filed on 30 March 2022, the contents of which are incorporated herein by reference in their entirety. The technique disclosed in EP22165697.8, also addresses a technical disadvantage of a CU-DU split. According to this arrangement communication between neighbouring TRPs is proposed in order to coordinate radio resource management and interference mitigation in a radio access network. Figure 5 provides an example illustration of this technique with more detail found in EP22165697.8.

[0053] Figure 5 schematically illustrates a proposed allocation of gNB functions in a CU and a DU for a plurality of UEs showing corresponding functions to those of Figure 5. As shown in Figure 5, a CU-CP 514 is configured to perform a set of functions including RRM-1 functions 502, RRC-1 functions 503, PDCP-CP functions 504, Security- 1 functions 506, NAS functions 508, UE context functions 510 and QoS functions 512. A CU-UP 518 is configured to perform PDCP-UP functions 516. A DU is configured to perform a set of functions RRM-2 functions 520, RRC-2 functions 522, Security-2 functions 524, RLC functions 526, MAC functions 528 and PHY functions 530. The RRM-1 functions 502 and the RRM-2 functions 520 may each represent a sub-set of the RRM functions 402 in CU-CP 40a. In other words, the RRM functions 502 are split into RRM-1 functions 502 and the RRM-2 functions 520, with the RRM-1 functions 502 being performed by the CU-CP 514 and the RRM-2 functions 520 being performed by the DU 532. Similarly, the RRC-1 functions 503 and the RRC-2 functions 522 may each represent a sub-set of the RRC functions 403 in CU-CP 40a. In other words, the RRC functions 403 are split into RRC-1 functions 503 and the RRC-2 functions 522, with the RRC-1 functions 503 being performed by the CU-CP 514 and the RRC-2 functions 522 being performed by the DU 532. Similarly, the Security- 1 functions 506 and the Security-2 functions 524 may each represent a sub-set of the Security functions in the CU-CP 44a. In other words, the Security functions are split into the Security- 1 functions 506 and the Security-2 functions 524, with the Security-1 functions 506 being performed by the CU-CP 514 and the Security-2 functions 524 being performed by the DU 532.

[0054] The splitting of RRM functions between the CU-CP 514 and the DU 532 can enable a more efficient management of communications resources. The splitting of RRC functions CU-CP 514 and the DU 532 may enable reduced latency communications by reducing message exchanges between the CU-CP 514 and the DU 532. The splitting of security functions between the CU-CP 514 and the DU 532 can provide improved security communications between the CU-CP 514 and the DU 532, or between two DUs over an air interface.

[0055] The NAS functions 508, the UE context functions 510 and the QoS functions 512 performed by the CU-CP-514 may broadly correspond to the NAS functions 408, the UE context functions 410 and the QoS functions 412 performed by the CU-CP 40a. The PDCP-UP functions 516 in the CU-UP 518 may broadly correspond to the PDCP functions-UP 414 in the CU-UP 40b. The RLC functions 526, the MAC functions 528 and the PHY functions 530 performed by the DU 532 may broadly correspond to the RLC functions 416, the MAC functions 418 and the PHY functions 420 performed by the DU 42.

[0056] As will be appreciated, the above allocation of gNB functions among the CU-CP 514 and the DU 532 provides a delegation of at least some CU functionality to a DU. The delegation of RRC functions to a DU may reduce the number of exchanges between a CU and a DU required to control communications with a communications device such as when a configuration change is required.

[0057] Although the above has been described for the transmission of a downlink control message from the CU-CP 514 to a UE, example embodiments can be applied to an uplink control message transmitted from the UE to the CU-CP 514. For example, the DU 532 may receive a control message from the UE for transmission to the CU-CP 514. In one example, the control message may include an RRC message such as a measurement report. The DU 532 may execute the RRC-2 functions 522 based on the RRC message to extract a part of the RRC message. Based on the extracted part of the RRC message, the DU 532 may determine that it can respond to the UE directly. For example, the DU 532 may prepare a configuration (such as a measurement configuration) based on the control message and transmit the configuration to the UE or use this information in RRM-2 522 or exchange this information with another DU 542. The DU 532 may determine that the control message should be forwarded to the CU for the CU to extract a remaining part of the RRC message. In some embodiments, the DU 532 may transmit the configuration to the UE and forward the control message to the CU. Upon receiving the control message, the CU may extract a remaining part of the RRC message from the control message. Based on the extracted remaining part of the RRC message, the CU may decide to change a configuration (such as a measurement configuration) of the UE based on the extracted remaining part of the message. When the CU changes a configuration of the UE, the process may follow the same steps as explained above for the transmission of the control message from the CU to the UE.

[0058] Figure 5 illustrates a set of functions for a first communications device 540 in the CU-CP 514, the CU-UP 518 and a first DU 532a. Furthermore, Figure 5 illustrates a set of functions for a second communications device 542 in the CU-CP 514, the CU-UP 518 and a second DU 532b.

[0059] The first DU 540 and the second DU 542 may be physically separate nodes. As such, there is provided between the first DU 532a and the second DU 532b an air interface 550 configured for the exchange ofinformation for interference management. The air interface may utilise communications resources of the physical layer. In other words, communications resources are shared between the first communications device 540, the second communications device 542, the first DU 532a and the second DU 532b. The first communications device 540 may be located in a cell provided by the first DU 532a and the second communications device is located in a cell provided by the second DU 532b. In other words, the first DU 532a is configured to control the first communications device 540 and the second DU 532b is configured to control the second communications device 542b. Therefore, if any communications resource management is required to manage inter-cell interference between the cell containing the first communications device 540 and the cell containing the second communications device 542, such information can be exchanged over the air interface 550 between the first DU 532a and the second DU 532b. In the example shown in Figure 5, the first DU 532a and the second DU 532a are physically separate nodes. Therefore, the air interface 550 may be referred to as a “physical DU-DU interface”. Alternatively, due to the presence of the RRM-2 functions 520, the RRC-2 functions 522 and the Security functions 524 in the first DU 532a and the second DU 532b, the air interface 550 may be referred to as a “logical CU-CU interface”. In other words, the air interface 550 may be regarded as a logical CU-CU interface due to the presence of CU functions in the first DU 532a and the second DU 532b.

[0060] The configuration described in Figure 5 can improve interference management, particularly in the context of dense cell deployment. For example, the RRM-2 functions 522 may include measurement and reporting functions. Accordingly, the first DU 532a and the second DU 532b may utilise the RRM-2 functions 520 to respectively collect a measurement report from the first communications device 540 and the second communications device 542 respectively. Then, by exchanging information about the measurement reports over the air interface 550, the first DU 532a and the second DU 532b can determine whether additional measurement configurations are required for interference management and in addition if any action is required based on received measurement reports. Therefore, the provision of a RRC functions in a DU can reduce latency in communications for controlling a communications device compared with conventional architectures as explained above. Furthermore, the CU-CP 514 may execute the RRM-1 functions 502 and the DU 532 may execute the RRM-2 functions 520. The execution of the RRM functions 502, 520 may impact the contents of the RRC message based on, for example, an interference management / communications resource management decision. Furthermore, the CU-CP 514 may execute the Security-1 functions 506 and the DU 532 may execute the Security-2 functions 524 to provide for a secure transmission of the RRC message.

[0061] Improved Radio Network Architecture

[0062] With the above-mentioned disadvantages of the CU-DU split, it has been proposed for future radio access networks that there should not be a CU-DU standardised interface (Fl). Instead, it has been proposed that there should be a split between remote radio head (RRH) or Radio Unit (RU) and the rest of the gNB functionality, so that mobile network operators will still require multi-vendor deployments. Here, the RRH or RU can be a component of a device which has a functionality of the TRP(s). The RRH or RU disclosed herein can be also denoted as Remote Radio Unit (RRU), Remote Unit (RU), Edge Unit (EU). Figures 6a and 6b illustrate an example of functions with examples of a 5G / NR architecture explained above reference to Figures 1 to 5 adapted to remove a split CU-DU architecture to a new architecture where CU-DU split is not specified.

[0063] Figures 6a and 6b provides a corresponding presentation of radio network architectural components to the example shown in Figures 4a and 4b and so the same parts have corresponding numerical designations. As shown in Figure 4b, gNB functionality is formed as from a CU, a DU and a TRP which may include an RRH. In contrast, in Figure 6b, the gNB functionality without radio communication transmission and reception functions is formed as a unit 602, in which there is no split between the DU 604 and the CU 606within this unit 602. Although functionality of a CU and a DU is still present in the gNB, the interface between the CU 606 and the DU 604 is not specified and therefore may vary between implementations. As shown in Figure 6b, the CU 606 and the DU 604 represent respective functionalities of a CU and a DU. However, these are contained within the unit 602 which forms functional processing of a gNB but does not include transmission and / or reception of radio signals via a wireless access interface. Transmission and reception of radio signals forming a wireless access interface provided by the radio access network are made by physical components in a RRH or Radio Unit (RU) 600.

[0064] In the following explanation, the term first radio node is used to refer to functionality contained within a protocol stack and processing elements shown in Figures 6a and 6b which form the CU 606 and DU 604 functionality. The unit 602 is therefore referred to as a first radio node 602 whereas the RRH or RU 600 will be referred to as a second radio node. As will be appreciated, terminology used in respect of infrastructure equipment forming a radio access networks has varied between generations of wireless communications technologies so that the term base station was used for 2G, a NodeB was used for 3G, whereas an eNodeB was used in a 4G, which became a gNB for 5G. The infrastructure equipment forming a radio access networks in 6G can be denoted as 6G Node B or 6G RAN node. Hence in the following description radio network infrastructure equipment comprising functionality associated with the physical layer and above for the protocol stack associated with the functionality of scheduling and security of the combined CU and DU will be referred to as a first radio node whereas the radio network transmission and reception at the physical layer forming a wireless access interface for transmitting and receiving data to communications devices / UEs will be referred to as the RU or second radio node.

[0065] As shown in Figures 6a and 6b, the first radio node 602 has functionality associated both the CU 606 and the DU 604 corresponding to the functionality of the CU and DU of the gNB shown in Figures 4a and 4b. However, these functions may be adapted in accordance with a rationalisation and simplification resulting from removal of a formalised split between the CU and the DU. For example, transport processing may be formed by transport processes 605b and 605a, although in practice these may be the same unit. Correspondingly, the physical layer and transport layer functionality 612b may be formed and may be adapted with respect to the DU functionality shown in Figure 4, although there may be some adaptation in accordance with the merged functionality within the first radio node 602. Corresponding to the example shown in Figure 4, the SDAP 402b and PDCP 404b and the REC 406b and MAC 408b will be largely unchanged because these communicate with corresponding components within the UE 14. Likewise, in the radio unit or second radio node 600, the physical layer components 410b will be the same as that shown in Figure 4b although there may be some adaptation of the physical layer and transport functions 610c, 612a. Correspondingly, the interfaces between the physical and transport functions with the second radio node and the first radio node 614, 615 may be adapted in accordance with a change in the architecture shown in Figures 6a and 6b to remove the DU-CU split. However, in other examples this functionality may be the same as that shown in Figures 4a and 4b.

[0066] As will be appreciated, one of the advantages of removing a CU-DU split is to obviate requirements to provide a second or separate security level by encrypting of different layers shown in Figure 4b, which would normally be performed by the DU, which would otherwise be required as explained above for European patent application EP21155607.1. This is because according to the architecture illustrated by Figure 6, with no formalised split between the DU and a CU, components forming corresponding file functionality of a CU and DU would be hosted or implemented by the same operator and produced by the same vendor. Similarly, a more complicated arrangement for controlling mobility as disclosed in EP22165697.8, requiring a split in some functionality between the CU and the DU is as a result of the CU-DU split.The interface 610 between the RU or second radio node 600 and the physical layer 410a of the UE 14 corresponds to and will be the same as the CPRI interface.

[0067] According to the arrangement shown in Figure 6. an interface between CU 606 and DU 604 functionality is open in the sense that this is not specified. That is to say, the interface between the CU and the DU functionality is not specified and standardised. 5G standards provide a CU-CU interface for coordination between gNB vendors. That is to say, that is a specified interface between CUs which can be used to provide cooperation between different gNB vendors. This can be seen to correspond to an inter gNB interface like Xninterface for coordination between multi-vendor deployments in 6G. However, for a 6G architecture, gNB functions may spread across different geographical areas. Therefore, both higher layer (i.e., Xninterface) and lower layer coordination may be necessary between second radio nodes / RUs. Here the term of the inter 6G base station interface is not limited to "Xn interface". A new term for the inter 6G base station interface can be defined. In other words, the term "Xn interface" disclosed herein can be replaced to other inter base station interface (including inter 6G base station interface).

[0068] Two split options are possibilities, which may be used according to example embodiments:

[0069] • Upper MAC in CU-DU - lower MAC in Radio Unit (RU) (Remote Radio Head (RRH) / TxRx Point (TRP))

[0070] • Upper PHY in CU-DU - lower PHY in RU (RRH / TRP)

[0071] Figure 7 provides a schematic representation of a wireless communications network configured with a radio access network part which is adapted according to the present technique to remove a split between the CU and the DU which is illustrated in Figures 1 to 5. As shown in Figure 7, first radio nodes 602 are connected to respective second radio nodes 600 via an interface 615, which corresponds to the interface 16 between the DU and the TRP which may have similar or the same functionality. As shown in Figure 7, each of the second radio nodes / RUs 600 forms a cell 12 of the radio access network which corresponds to the arrangement shown in Figure 1. As shown in Figure 7, there is an interface 764 between the first radio nodes 602.1, 602.2 which is the Xninterface 764 and corresponds to the arrangement shown in Figure 1. Therefore Figure 7 illustrates an adapted arrangement for the wireless communications network illustrated in Figure 1 to remove a split between the CU and the DU so that the first radio nodes 602.1, 602.2 form functionality performed by the CU and the DU as illustrated in Figure 6.

[0072] Embodiments of the present technique can provide a method of operating a second radio node or a second radio node controlled by a first radio node which in combination with the second radio node forms a wireless access interface for a cell of a radio access network part of a wireless communications network. The method comprises transmitting radio signals via the wireless access interface to one or more communications devices / UEs in the cell or receiving radio signals transmitted via the wireless access interface from the one or more communications devices / UEs. The method comprises receiving configuration information from the first radio node to form a wireless over-the-air, OTA, interface between the second radio node and another second radio node. The wireless OTA interface comprises an outward link for transmitting control information from the second radio node to the other second radio node and a reverse link for receiving control information by the second radio node from the other second radio node, the control information for supporting the transmission and / or reception of the radio signals via the wireless access interface by the one or more communications devices / UEs.

[0073] According to example embodiments of the present technique, a wireless interface is provided between respective second radio nodes / RUs 600.1, 600.2 in addition to the interface between the first radio nodes 602.1, 602.2, which is the Xninterface 764. This arrangement is illustrated in Figure 8, which provides a simplified representation of Figure 7, to support an explanation of a wireless interface between respectivesecond radio nodes 600.1, 600.2, shown in Figure 8, comprising an outward part 810 and a return part 812. For clarity, to distinguish this interface 810, 812 from the wireless access interface formed by the second radio nodes 600.1, 600.2 for communicating with UEs 14, the wireless interface between respective second radio nodes 600.1, 600.2 will be referred to as over-the-air (OTA) communication. The second radio nodes 600.1, 600.2 are controlled by different first radio nodes 602.1, 602.2. The second radio nodes 600.1, 600.2 form respective cells 12 to support and to provide a wireless access interface for the UEs 14.1, 14.2. According to this arrangement, an assumption is that the interface Xn764 between the first radio nodes 602.1, 602.2, may be used to exchange an initial configuration and delay agnostic configuration updates between base stations / gNBs belonging to different vendors. However, for delay critical information, over the air (OTA) updates between the second radio nodes 600.1, 600.2 can be defined via the wireless interface 810, 812. This delay critical information cannot be exchanged or preferably should not be exchanged over Xninterface due to its latency.

[0074] Coordination of Resource Between Second Radio Nodes / RUs

[0075] As explained above, coordination between neighbouring TRPs, the Xn based interface will be used to exchange the initial configuration and delay agnostic configuration updates between gNBs belonging to different vendors. But for delay critical information, over-the-air (OTA) updates between TRPs will be defined. This critical information cannot be exchanged over Xn interface due to latency.

[0076] For the coordination between the neighbouring second radio nodes 600.1, 600.2, physical communication resources for the wireless OTA interface should be configured and scheduled between them. Example embodiments can provide arrangements for configuring and scheduling physical communication resources between the neighbouring second radio nodes 600.1, 600.2.

[0077] Embodiments of the present technique can provide a configuration of neighbouring second radio nodes / RUs for that they can communicate over the air where physical communication resources are configured as one or more of the following options:

[0078] Option 1: Dedicated frequency resources.

[0079] Option 2: A UE passes information from one TRP to another TRP.

[0080] Option 3: TRP as UE for another TRP.

[0081] The radio communication resources may comprise carrier frequency, bandwidth part and time-frequency physical resources, for example as allocated time slots and number of PRBs. In some example, embodiments may also include an earlier step where initial set-up of communications and authorization are done on Xninterface between gNBs.

[0082] Details of the Physical Communication Resources

[0083] Option 1: Dedicated frequency resources can be configured in a reserved part of the wireless access interface which is provided for transmitting and receiving radio signals with one or more UEs of a cell formed by the first and second radio nodes. These are referred to as predefined OTA communications resources. In some examples, the OTA communications resources can be configured via a backhaul communications link or interface, for example the Xn interface. As part of this configuration frequency bands are specified for the OTA communications. For example, for FDD one band is configured for the uplink and one band is configured for the downlink, and for TDD only a single band is specified for both the uplink and downlink. An example embodiment is illustrated below in Figure 8, in which a wireless communications interface is provide by respective second radio nodes / RUs 600.1, 600.2 for transmitting and receiving radio signals to UEs 14.1, 14.2, 14.3, 14.4 as represented by double headed arrows 800. As shown in Figure 8, a first of the second radio nodes / RU 600.1 communicates with a second of the second radio nodes / RUs 600.2 via a wireless OTA interface which comprises an outward link 810 and a returnlink 812 with respect to the first of the second radio nodes / RU 600.1 the using dedicated resources. The dedicated resources for the outward link and return links 810, 812 may be identified during an initial configuration of the second radio nodes / RUs 600.1, 600.2, by the first radio nodes exchanging configuration information via the Xn interface 764 between the first radio nodes 602.1, 602.2.

[0084] Alternatively, the dedicated resources for the outward link and return links 810, 812 may be configured by one of the second radio nodes / RUs configuring another of the second radio nodes. The dedicated resources can be configured dynamically by scheduling the resources using existing access procedures for the operation of the wireless access interface 800 by one of the second radio nodes / RUs 600.1 to another of the second radio nodes / RUs 600.2. The communication resources can be either a) Dynamically scheduled via DCI, or b) Semi-statically allocated via downlink semi-persistent signalling (DU SPS) and uplink configured grant (UU CG).

[0085] Option 2: According to this example embodiment, which is illustrated in Figure 9, one or more communications devices / UEs performs a relay function between second radio nodes / RUs 600.1, 600.2. Although only one communications device / UE is shown in Figure 9, in other examples a plurality of communications devices / UEs may perform the relay functions, each acting as a relay node to relay information between each other between the second radio nodes / RUs 600.1, 600.2. As shown in Figure 9, the UE acting as a relay node is an intermediate device that receives information from a first of the second radio nodes / RU 600.1 on a first part of an outward link 910a and relays the information on a second part of the outward link 910b to the second of the radio nodes / RU 600.2. Correspondingly, the return link from the second of the second radio nodes / RU 600.1 to the first of the second radio nodes / RU 600.2 is formed from a first part 912a from the second of the second radio nodes / RU 600.2 to the UE 14.5 acting as a relay node and a second part 912b from the UE 14.5 to the first of the second radio nodes / RU 600.1. The first part of the outward link 910a, may be considered as a downlink since this forms part of the wireless access interface formed by the first of the second radio nodes / RU 600.1, whereas the second part of the outward link 910b may be considered as an uplink of the wireless access interface formed by the second of the second radio nodes / RU 600.1. Correspondingly, the first part of the return link 912a, may be considered as a downlink since this forms part of the wireless access interface formed by the second of the second radio nodes / RU 600.2, whereas the second part of the return link 912b may be considered as an uplink of the wireless access interface formed by the first of the second radio nodes / RU 600.1.

[0086] According to example embodiments, the UE 14.5 acting as a relay node is connected contemporaneously to both of the second radio nodes / RUs 600.1, 600.2. This may be achieved for example by Carrier Aggregation, Dual-connectivity or with dual active protocol stack (DAPS)) where it can receive and transmit to both second radio nodes / RUs 600.1, 600.2. at the same time. For example, delay critical information can be communicated from one of the second radio nodes / RUs 600.1, 600.2, to another of the second radio nodes / RUs 600.1, 600.2 in a RRC message or MAC CE.

[0087] This option has a limitation that if no UE is available that is connected to both second radio nodes / RUs 600.1, 600.2 then the outward and return link 910, 912 cannot be formed to communicate the information between the second radio nodes / RUs 600.1, 600.2. According to example embodiments, the UE applies physical communication resources that is being scheduled by the corresponding second radio node / RU 600.1, 600.2. The communication resources can be a) Dynamically scheduled via DCI b) Semi-statically allocated via DL SPS and UL CG.

[0088] Option 3: According to another example embodiment, communication between second radio nodes / RUs 600.1, 600.2 is formed as part of the wireless access interface provided by one of the second radionodes / RUs 600.1, 600.2, which acts as a UE for the other of the second radio nodes / RUs 600.1, 600.2. As shown in Figure 10, a first of the second radio nodes / RUs 600.1 acts as a UE for a second of the second radio nodes / RUs 600.2 so that the outward link 1000 is formed as an uplink communications channel of the wireless access interface and a return link 1002 is formed by a downlink communications channel by the second of the second radio nodes / RUs 600.2.

[0089] In one example in which the first of the second radio nodes / RUs 600.1 and the second of the second radio nodes / RUs 600.2 are using the same or a different carrier, the communication resources can be allocated within a system bandwidth of the wireless access interface provided by the wireless communications network. According to this example embodiment, the first of the second radio nodes / RUs 600.1 becomes a UE for the second of the second radio nodes / RUs 600.2, so that the second 600.2 can schedule to first of the second radio nodes / RUs 600.1 (UE) in the downlink as the reverse link 1002, whereas the first of the second radio nodes / RUs 600.1 (UE) can transmit in the uplink, as shown on Figure 10. The initial configuration of the first of the second radio nodes / RUs 600.1, 600.2, becoming and behaving as a UE can be configured by higher layers and / or configured by exchanging information over Xninterface 764. The communication resources can be either a) Dynamically scheduled using a DCI, or b) Semi-statically allocated via DL SPS and UL CG.

[0090] According to this example embodiment in which the first of the second radio nodes / RUs 600.1 acts as a UE, the outward link 1000 is an uplink transmission by the second radio node 600.1, whereas a conventional second radio node / RU only transmits in the downlink, without an implementation of the wireless OTA interface. As such, the uplink transmission as the outward link 1000 may also cause Cross Link Interference at the second radio nodes / RUs 600.1, 600.2 receiver between a reception of an uplink from a UE whilst transmitting to the second of the second radio nodes / RUs 600.2. For example, as shown on Figure 10, the first of the second radio nodes / RUs 600.1 may be receiving in the uplink from a first of the UEs 14.1 whilst transmitting using the uplink band (or uplink slot) to the second of the second radio nodes / RUs 600.2. One technique to alleviate this cross-link interference is to use different antenna panels for the outward link transmission 1000 from the first of the second radio nodes / RUs 600.1 to the second of the second radio nodes / RUs 600.2 and receiving uplink transmissions from the first UE 14.1. Different antenna panels may provide spatial isolation between the transmitter and the receiver.

[0091] In another embodiment, for TDD operations, sub-band frequency division (SBFD) may be configured for several OFDM symbols or a slot, where in these OFDM symbols or slot, one of the second radio nodes / RUs 600.1, 600.2 may transmit to another second radio nodes / RUs 600.1, 600.2 whilst also transmitting in the downlink to another UE. For example, in Figure 10, the first of the second radio nodes / RUs 600.1, 600.2 may be configured with SBFD in one of the slots, and here it transmits using an uplink sub-band to the second of the second radio nodes / RUs 600.1, 600.2 whilst also transmitting in the downlink sub-band to the first of the UEs 14.1. At a second of the second radio nodes / RUs 600.1, 600.2, the same slot will be configured as an uplink or SBFD where the uplink sub-band at least partially overlaps with the uplink subband of the first of the second radio nodes / RUs 600.1, so that it can receive signalling from a first of the second radio nodes / RUs 600.1.

[0092] The outward or return communication links 1000, 1002, between the first of the second radio nodes / RUs 600.1, 600.2 and the second of the second radio nodes / RUs 600.1, 600.2 may become unstable at times due to a change in the radio conditions. If the first of the second radio nodes / RUs 600.1 is not reachable from the second of the second radio nodes / RUs 600.1, 600.2, for example by radio link failure, then a notification can be exchanged via Xninterface. The other direction may or may not have similar radio conditions. Therefore, a notification of the radio link failure could be sent per direction only i.e. from the first to the second of the second radio nodes / RUs 600.1, 600.2 in this case. In this case, the second of the second radionodes / RUs 600.2 may increase a power of its transmissions or pick up an intermediate node or second radio nodes / RUs 600.1, 600.2 to relay communications between the second 600.2 and the first 600.1 ofthe second radio nodes / RUs. An addressing scheme of messages over these links should be able to clearly identify the source and the target node / second radio nodes / RUs 600.1, 600.2 so that an intermediate node is able to forward messages to the correct node. This configuration can be performed via Xn interface.

[0093] Those skilled in the art would further appreciate that such infrastructure equipment and / or communications devices 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 communications devices as herein defined and described may form part of communications systems other than those defined by the present disclosure.

[0094] The following numbered paragraphs provide further example aspects and features of the present technique:

[0095] Paragraph 1. A method of operating a second radio node (600.1, 600.2) controlled by a first radio node (602.1, 602.2) which in combination with the second radio node (602.1, 602.2) forms a wireless access interface for a cell of a radio access network part of a wireless communications network, the method comprising

[0096] transmitting radio signals via the wireless access interface to one or more communications devices in the cell or to receive radio signals transmitted via the wireless access interface from the one or more communications devices, and

[0097] receiving configuration information from the first radio node to form a wireless over-the-air, OTA, interface (700, 712) between the second radio node (600.1, 600.2) and another second radio node (600.1, 600.2), the wireless OTA interface comprising an outward link for transmitting control information from the second radio node (600.1, 600.2) to the other second radio node (600.1, 600.2) and a reverse link for receiving control information by the second radio node (600.1, 600.1) from the other second radio node (600.1, 600.2), the control information for supporting the transmission and / or reception of the radio signals via the wireless access interface by the one or more communications devices.

[0098] Paragraph 2. A method of paragraph 1, wherein the configuration information for configuring the wireless OTA interface received from the first radio node (602.1, 602.2) is exchanged between the first radio node (602.1) and a first radio node (602.2) controlling the other second radio node (600.2).

[0099] Paragraph 3. A method of paragraphs 1 or 2, wherein the configuration information identifies communications resources of a dedicated frequency band for establishing the wireless OTA interface. Paragraph 4. A method of paragraph 3, wherein the configuration information identifying communications resources of the dedicated frequency band for establishing the wireless OTA interface are identified as part of an initial configuration of the second radio nodes (600.1, 600.2) by exchanging configuration information between the first radio node and the other first radio node controlling the other second radio node.

[0100] Paragraph 5. A method of paragraphs 3, 4 and 5, wherein the dedicated resources for the outward link and return links are configured by the second radio node receiving the configuration information from the other second radio node.

[0101] Paragraph 6. A method of paragraph 5, wherein the configuration information identifying communications resources of the dedicated frequency band for establishing the wireless OTA interface are dynamically scheduled using a downlink control information received from the other second radio node.

[0102] Paragraph 7. A method of paragraph 5, wherein the configuration information identifying communications resources of the dedicated frequency band for establishing the wireless OTA interface are semi-statically allocated via downlink semi-persistent signal and an uplink configured grant.Paragraph 8. A method of paragraphs 1 or 2, wherein the outward link and the return link are formed with at least one communications device providing a relay function.

[0103] Paragraph 9. A method of paragraph 8, wherein the outward link and the return link are formed by a plurality of communications devices forming a communication chain providing a relay function between the second radio node and the other second radio node, each of the plurality of communications devices communicating with at least one of a neighbouring communications device, the second radio node and the other second radio node to form the communication chain.

[0104] Paragraph 10. A method of paragraph 8 or 9, wherein the configuration information includes downlink control information, DCI, defining communications resources of the wireless access interface to establish a first part of the outward link via a downlink channel of the wireless access interface to the at least one communications device acting as a relay node providing the relay function and a first part of the return link via an uplink channel of the wireless access interface from the relay node to the second radio node (600.1), a second part of the outward link and a second part of the return link being established with the other second radio node.

[0105] Paragraph 11. A method of paragraph 9 or 10, wherein the DCI dynamically schedules the uplink channel for the first part of the return link and the downlink channel for the second part of the outward link.

[0106] Paragraph 12. A method of paragraph 9 or 10, wherein the DCI schedules the uplink channel for the first part of the return link as a configured grant of uplink resources and the downlink channel for the second part of the outward link as a semi-persistent signalling, SPS, allocation of downlink resources. Paragraph 13. A method of paragraph 1 or 2, wherein the outward link from the second radio node (600.1) to the other second radio node (600.2) is formed as an uplink channel via the wireless access interface as if the second radio node were one of the one or more communications devices, and the return link to the second radio node (600.2) is formed as a downlink channel via the wireless access interface. Paragraph 14. A method of paragraph 13, wherein sub-band frequency division is used to form the outward link and the return link, the outward link and the return link being transmitted and received on different sub-bands to a sub-band used for the uplink and a sub-band used for the downlink of the wireless access interface.

[0107] Paragraph 15. A method of paragraph 14, wherein the second radio node (600.1) is configured with a plurality of antenna panels each providing at least directional isolation for transmitting radio signals and receiving radio signals, and the sub-band frequency division forms the outward link and the return link by selecting one of the antenna panels to transmit radio signals to the second radio node (600.2) on the uplink of the wireless access interface forming the outward link, the selected antenna panel being different to an antenna panel used to transmit on the downlink to the one or more communications devices, and

[0108] selecting one of the antenna panels to receive radio signals from the second radio node (600.2) on the downlink of the wireless access interface forming the return link, the selected antenna panel being different to an antenna panel used to receive on the uplink from the one or more communications devices. Paragraph 16. A method of any of paragraphs 1 to 15, wherein the other first radio node in combination with the other second radio node forms a wireless access interface for a cell of the radio access network part of the wireless communications network, the first radio node and the other radio node being connected via an interface.

[0109] Paragraph 17. A method of paragraph 16, wherein the interface connecting the first radio node to the other first radio node is an Xninterface.

[0110] Paragraph 18. A method of paragraph 15 or 16, comprising

[0111] monitoring a quality of communication via the outward link and the return link to determine a quality measure,

[0112] based on the quality measure, determining a radio link failure of one or both of the outward link and the return link,communicating the radio link failure to the first radio node, and

[0113] receiving new configuration information to re-establish the outward link and the return link with the other second radio node.

[0114] Paragraph 19. A method of paragraph 18, wherein the new configuration information received from the first radio node is generated in combination with the other first radio node by exchanging information between the first radio node and the other first radio node.

[0115] Paragraph 20. A second radio node (600.1, 600.2) which in combination with a first radio node (602.1, 602.2) provides a wireless access interface for a cell of a radio access network part of a wireless communications network, the second radio node comprising

[0116] transceiver circuitry for transmitting, under control of the first radio node (602.1), radio signals via the wireless access interface to one or more communications devices and for receiving radio signals transmitted via the wireless access interface from the one or more communications devices, and receiving configuration information from the first radio node to form a wireless over-the-air, OTA, interface (700, 712) between the second radio node (600.1, 600.2) and another second radio node (600.1, 600.2), the wireless OTA interface comprising an outward link for transmitting control information from the second radio node (600.1, 600.2) to the other second radio node (600.1, 600.2) and a reverse link for receiving control information by the second radio node (600.1, 600.1) from the other second radio node (600.1, 600.2), the control information for supporting the transmission and / or reception of the radio signals via the wireless access interface by the one or more communications devices.

[0117] Paragraph 21. A method of operating a communications device to act as a relay node, the method comprising

[0118] receiving radio signals via a wireless access interface of a cell formed by a second radio node as a first part of an outward link via a downlink channel of the wireless access interface and transmitting the radio signals via a wireless access interface of a neighbouring cell formed by another second radio node as a second part of an outward link via an uplink channel of the wireless access interface, and receiving radio signals via the wireless access interface of the neighbouring cell formed by the other second radio node as a first part of a return link via a downlink channel of the wireless access interface and transmitting the radio signals via the wireless access interface of the cell formed by the second radio node as a second part of the return link via an uplink channel of the wireless access interface,

[0119] monitoring a quality of communication via the outward link and the return link to determine a quality measure,

[0120] based on the quality measure, determining a radio link failure of one or both of the outward link and the return link, and

[0121] transmitting the radio link failure to one or both of the second radio node and the other second radio node.

[0122] Paragraph 22. A method of paragraph 21, comprising

[0123] receiving new configuration information to re-establish the outward link and the return link from either the second radio node or the other second radio node.

[0124] Paragraph 23. A method on paragraph 21 or 22, wherein the communications device acting as the relay node is configured with carrier aggregation, the carrier aggregation comprising an arrangement in which the first part of the outward link and the second part of the return link are formed using a first carrier providing the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link are formed using a second carrier providing the wireless access interface of the neighbouring cell formed by the other second radio node.

[0125] Paragraph 24. A method of paragraphs 21 or 22, wherein the communications device acting as the relay node is configured with dual connectivity, the dual connectivity providing the first part of the outward link and the second part of the return link via the wireless access interface of the cell formed by thesecond radio node and the second part of the outward link and the first part of the return link via the wireless access interface of the neighbouring cell formed by the other second radio node.

[0126] Paragraph 25. A method of any of paragraphs 21 to 24, wherein the communications device acting as the relay node is configured with a dual active protocol stack, which provides the first part of the outward link and the second part of the return link via the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link via the wireless access interface of the neighbouring cell formed by the other second radio node.

[0127] Paragraph 26. A communications device operating to act as a relay node in a wireless communications network, the communications device comprising

[0128] transceiver circuitry configured to transmit and to receive radio signals via a wireless access interface provided by the wireless communications network, and

[0129] controller circuitry configured with the transceiver circuitry

[0130] to receive radio signals via a wireless access interface of a cell formed by a second radio node as a first part of an outward link via a downlink channel of the wireless access interface and to transmit the radio signals via a wireless access interface of a neighbouring cell formed by another second radio node as a second part of an outward link via an uplink channel of the wireless access interface, and

[0131] to receive radio signals via the wireless access interface of the neighbouring cell formed by the other second radio node as a first part of a return link via a downlink channel of the wireless access interface and to transmit the radio signals via the wireless access interface of the cell formed by the second radio node as a second part of the return link via an uplink channel of the wireless access interface,

[0132] to monitor a quality of communication via the outward link and the return link to determine a quality measure,

[0133] based on the quality measure, to determine a radio link failure of one or both of the outward link and the return link, and

[0134] to transmit the radio link failure to one or both of the second radio node and the other second radio node.

[0135] Paragraph 27. A communications device of paragraph 26, wherein the controller circuitry is configured with the transceiver circuitry

[0136] to receive new configuration information to re-establish the outward link and the return link from either the second radio node or the other second radio node.

[0137] Paragraph 28. A communications device of paragraph 26 or 27, wherein the controller circuitry and configured the transceiver circuitry are configured with carrier aggregation, the carrier aggregation comprising an arrangement in which the first part of the outward link and the second part of the return link are formed using a first carrier providing the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link are formed using a second carrier providing the wireless access interface of the neighbouring cell formed by the other second radio node.

[0138] Paragraph 29. A communications device of paragraphs 26 or 27, wherein the controller circuitry and the transceiver circuitry are configured with dual connectivity, the dual connectivity providing the first part of the outward link and the second part of the return link via the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link via the wireless access interface of the neighbouring cell formed by the other second radio node.

[0139] Paragraph 30. A communications device of any of paragraphs 26 to 29, wherein the controller circuitry and the transceiver circuitry are configured with a dual active protocol stack, which provides the first part of the outward link and the second part of the return link via the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link via the wireless access interface of the neighbouring cell formed by the other second radio node.Paragraph 31. Circuitry for a communications device operating to act as a relay node in a wireless communications network, the circuitry comprising

[0140] transceiver circuitry configured to transmit and to receive radio signals via a wireless access interface provided by the wireless communications network, and

[0141] controller circuitry configured with the transceiver circuitry

[0142] to receive radio signals via a wireless access interface of a cell formed by a second radio node as a first part of an outward link via a downlink channel of the wireless access interface and to transmit the radio signals via a wireless access interface of a neighbouring cell formed by another second radio node as a second part of an outward link via an uplink channel of the wireless access interface, and

[0143] to receive radio signals via the wireless access interface of the neighbouring cell formed by the other second radio node as a first part of a return link via a downlink channel of the wireless access interface and to transmit the radio signals via the wireless access interface of the cell formed by the second radio node as a second part of the return link via an uplink channel of the wireless access interface,

[0144] to monitor a quality of communication via the outward link and the return link to determine a quality measure,

[0145] based on the quality measure, to determine a radio link failure of one or both of the outward link and the return link, and

[0146] to transmit the radio link failure to one or both of the second radio node and the other second radio node.

[0147] Paragraph 32. Circuitry for a second radio node (600.1, 600.2) which in combination with a first radio node (602.1, 602.2) provides a wireless access interface for a cell of a radio access network part of a wireless communications network, the circuitry comprising

[0148] transceiver circuitry for transmitting, under control of the first radio node (602.1), radio signals via the wireless access interface to one or more communications devices and for receiving radio signals transmitted via the wireless access interface from the one or more communications devices, and receiving configuration information from the first radio node to form a wireless over-the-air, OTA, interface (700, 712) between the second radio node (600.1, 600.2) and another second radio node (600.1, 600.2), the wireless OTA interface comprising an outward link for transmitting control information from the second radio node (600.1, 600.2) to the other second radio node (600.1, 600.2) and a reverse link for receiving control information by the second radio node (600.1, 600.1) from the other second radio node (600.1, 600.2), the control information for supporting the transmission and / or reception of the radio signals via the wireless access interface by the one or more communications devices.

[0149] Paragraph 33. A non-transitory computer-readable storage medium storing a computer program according to any of paragraphs 1 to 19 and 21 to 25.

[0150] Although the present disclosure has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognise that various features of the described embodiments may be combined in any manner suitable to implement the technique.

[0151] References

[0152] [1] 3GPP document, TS 38.470.

[0153] [2] 3GPP document TS 38.473.

[0154] [3] 3GPP document TS 38.401.

[0155] [4] 3GPP document TS 138472 - V15.2.0.

[0156] [5] 3GPP document TS 38.300.

[0157] [6] 3GPP document TS 23.501.[7] 3GPP document TS 36.300.

[0158] [8] European patent application number EP21155607.1

[0159] [9] European patent application number EP22165697.8

[0160]

[0010] TS 38.423 Xninterface specification

[0161]

[0011] TR 38.843 - TR for AIML PHY Rel-18

[0162]

[0012] O-RAN specification: https: / / specifications.o-ran.org / specifications 0-RAN Control, User and Synchronization Plane Specification 16.01

Claims

CLAIMS1. A method of operating a second radio node (600.1, 600.2) controlled by a first radio node (602.1, 602.2) which in combination with the second radio node (602.1, 602.2) forms a wireless access interface for a cell of a radio access network part of a wireless communications network, the method comprising transmitting radio signals via the wireless access interface to one or more communications devices in the cell or to receive radio signals transmitted via the wireless access interface from the one or more communications devices, andreceiving configuration information from the first radio node to form a wireless over-the-air, OTA, interface (700, 712) between the second radio node (600.1, 600.2) and another second radio node (600.1, 600.2), the wireless OTA interface comprising an outward link for transmitting control information from the second radio node (600.1, 600.2) to the other second radio node (600.1, 600.2) and a reverse link for receiving control information by the second radio node (600.1, 600.1) from the other second radio node (600.1, 600.2), the control information for supporting the transmission and / or reception of the radio signals via the wireless access interface by the one or more communications devices.

2. A method of claim 1, wherein the configuration information for configuring the wireless OTA interface received from the first radio node (602.1, 602.2) is exchanged between the first radio node (602.1) and a first radio node (602.2) controlling the other second radio node (600.2).

3. A method of claims 1, wherein the configuration information identifies communications resources of a dedicated frequency band for establishing the wireless OTA interface.

4. A method of claim 3, wherein the configuration information identifying communications resources of the dedicated frequency band for establishing the wireless OTA interface are identified as part of an initial configuration of the second radio nodes (600.1, 600.2) by exchanging configuration information between the first radio node and the other first radio node controlling the other second radio node.

5. A method of claims 3, wherein the dedicated resources for the outward link and return links are configured by the second radio node receiving the configuration information from the other second radio node.

6. A method of claim 5, wherein the configuration information identifying communications resources of the dedicated frequency band for establishing the wireless OTA interface are dynamically scheduled using a downlink control information received from the other second radio node.

7. A method of claim 5, wherein the configuration information identifying communications resources of the dedicated frequency band for establishing the wireless OTA interface are semi-statically allocated via downlink semi-persistent signal and an uplink configured grant.

8. A method of claims 1, wherein the outward link and the return link are formed with at least one communications device providing a relay function.

9. A method of claim 8, wherein the outward link and the return link are formed by a plurality of communications devices forming a communication chain providing a relay function between the second radio node and the other second radio node, each of the plurality of communications devices communicating with at least one of a neighbouring communications device, the second radio node and the other second radio node to form the communication chain.

10. A method of claim 8, wherein the configuration information includes downlink control information, DCI, defining communications resources of the wireless access interface to establish a first part of the outward link via a downlink channel of the wireless access interface to the at least one communications device acting as a relay node providing the relay function and a first part of the return link via an uplink channel of the wireless access interface from the relay node to the second radio node (600.1), a second part of the outward link and a second part of the return link being established with the other second radio node.

11. A method of claim 9, wherein the DCI dynamically schedules the uplink channel for the first part of the return link and the downlink channel for the second part of the outward link.

12. A method of claim 9, wherein the DCI schedules the uplink channel for the first part of the return link as a configured grant of uplink resources and the downlink channel for the second part of the outward link as a semi-persistent signalling, SPS, allocation of downlink resources.

13. A method of claim 1, wherein the outward link from the second radio node (600.1) to the other second radio node (600.2) is formed as an uplink channel via the wireless access interface as if the second radio node were one of the one or more communications devices, and the return link to the second radio node (600.2) is formed as a downlink channel via the wireless access interface.

14. A method of claim 13, wherein sub-band frequency division is used to form the outward link and the return link, the outward link and the return link being transmitted and received on different sub-bands to a sub-band used for the uplink and a sub-band used for the downlink of the wireless access interface.

15. A method of claim 14, wherein the second radio node (600.1) is configured with a plurality of antenna panels each providing at least directional isolation for transmitting radio signals and receiving radio signals, and the sub-band frequency division forms the outward link and the return link by selecting one of the antenna panels to transmit radio signals to the second radio node (600.2) on the uplink of the wireless access interface forming the outward link, the selected antenna panel being different to an antenna panel used to transmit on the downlink to the one or more communications devices, andselecting one of the antenna panels to receive radio signals from the second radio node (600.2) on the downlink of the wireless access interface forming the return link, the selected antenna panel being different to an antenna panel used to receive on the uplink from the one or more communications devices.

16. A method of claim 1, wherein the other first radio node in combination with the other second radio node forms a wireless access interface for a cell of the radio access network part of the wireless communications network, the first radio node and the other radio node being connected via an interface.

17. A method of claim 16, wherein the interface connecting the first radio node to the other first radio node is an Xninterface.

18. A method of claim 15, comprisingmonitoring a quality of communication via the outward link and the return link to determine a quality measure,based on the quality measure, determining a radio link failure of one or both of the outward link and the return link,communicating the radio link failure to the first radio node, andreceiving new configuration information to re-establish the outward link and the return link with the other second radio node.

19. A method of claim 18, wherein the new configuration information received from the first radio node is generated in combination with the other first radio node by exchanging information between the first radio node and the other first radio node.

20. A second radio node (600.1, 600.2) which in combination with a first radio node (602.1, 602.2) provides a wireless access interface for a cell of a radio access network part of a wireless communications network, the second radio node comprisingtransceiver circuitry for transmitting, under control of the first radio node (602.1), radio signals via the wireless access interface to one or more communications devices and for receiving radio signals transmitted via the wireless access interface from the one or more communications devices, and receiving configuration information from the first radio node to form a wireless over-the-air, OTA, interface (700, 712) between the second radio node (600.1, 600.2) and another second radio node (600.1, 600.2), the wireless OTA interface comprising an outward link for transmitting control information from the second radio node (600.1, 600.2) to the other second radio node (600.1, 600.2) and a reverse link for receiving control information by the second radio node (600.1, 600.1) from the other second radio node (600.1, 600.2), the control information for supporting the transmission and / or reception of the radio signals via the wireless access interface by the one or more communications devices.

21. A method of operating a communications device to act as a relay node, the method comprising receiving radio signals via a wireless access interface of a cell formed by a second radio node as a first part of an outward link via a downlink channel of the wireless access interface and transmitting the radio signals via a wireless access interface of a neighbouring cell formed by another second radio node as a second part of an outward link via an uplink channel of the wireless access interface, and receiving radio signals via the wireless access interface of the neighbouring cell formed by the other second radio node as a first part of a return link via a downlink channel of the wireless access interface and transmitting the radio signals via the wireless access interface of the cell formed by the second radio node as a second part of the return link via an uplink channel of the wireless access interface,monitoring a quality of communication via the outward link and the return link to determine a quality measure,based on the quality measure, determining a radio link failure of one or both of the outward link and the return link, andtransmitting the radio link failure to one or both of the second radio node and the other second radio node.

22. A method of claim 21, comprisingreceiving new configuration information to re-establish the outward link and the return link from either the second radio node or the other second radio node.

23. A method on claim 21, wherein the communications device acting as the relay node is configured with carrier aggregation, the carrier aggregation comprising an arrangement in which the first part of the outward link and the second part of the return link are formed using a first carrier providing the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link are formed using a second carrier providing the wireless access interface of the neighbouring cell formed by the other second radio node.

24. A method of claim 21, wherein the communications device acting as the relay node is configured with dual connectivity, the dual connectivity providing the first part of the outward link and the second part of the return link via the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link via the wireless access interface of the neighbouring cell formed by the other second radio node.

25. A method of claim 21, wherein the communications device acting as the relay node is configured with a dual active protocol stack, which provides the first part of the outward link and the second part of the return link via the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link via the wireless access interface of the neighbouring cell formed by the other second radio node.

26. A communications device operating to act as a relay node in a wireless communications network, the communications device comprisingtransceiver circuitry configured to transmit and to receive radio signals via a wireless access interface provided by the wireless communications network, andcontroller circuitry configured with the transceiver circuitryto receive radio signals via a wireless access interface of a cell formed by a second radio node as a first part of an outward link via a downlink channel of the wireless access interface and to transmit the radio signals via a wireless access interface of a neighbouring cell formed by another second radio node as a second part of an outward link via an uplink channel of the wireless access interface, andto receive radio signals via the wireless access interface of the neighbouring cell formed by the other second radio node as a first part of a return link via a downlink channel of the wireless access interface and to transmit the radio signals via the wireless access interface of the cell formed by the second radio node as a second part of the return link via an uplink channel of the wireless access interface,to monitor a quality of communication via the outward link and the return link to determine a quality measure,based on the quality measure, to determine a radio link failure of one or both of the outward link and the return link, andto transmit the radio link failure to one or both of the second radio node and the other second radio node.

27. A communications device of claim 26, wherein the controller circuitry is configured with the transceiver circuitryto receive new configuration information to re-establish the outward link and the return link from either the second radio node or the other second radio node.

28. A communications device of claim 26, wherein the controller circuitry and configured the transceiver circuitry are configured with carrier aggregation, the carrier aggregation comprising an arrangement in which the first part of the outward link and the second part of the return link are formed using a first carrier providing the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link are formed using a second carrier providing the wireless access interface of the neighbouring cell formed by the other second radio node.

29. A communications device of claims 26, wherein the controller circuitry and the transceiver circuitry are configured with dual connectivity, the dual connectivity providing the first part of theoutward link and the second part of the return link via the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link via the wireless access interface of the neighbouring cell formed by the other second radio node.

30. A communications device of claim 26, wherein the controller circuitry and the transceiver circuitry are configured with a dual active protocol stack, which provides the first part of the outward link and the second part of the return link via the wireless access interface of the cell formed by the second radio node and the second part of the outward link and the first part of the return link via the wireless access interface of the neighbouring cell formed by the other second radio node.

31. Circuitry for a communications device operating to act as a relay node in a wireless communications network, the circuitry comprisingtransceiver circuitry configured to transmit and to receive radio signals via a wireless access interface provided by the wireless communications network, andcontroller circuitry configured with the transceiver circuitryto receive radio signals via a wireless access interface of a cell formed by a second radio node as a first part of an outward link via a downlink channel of the wireless access interface and to transmit the radio signals via a wireless access interface of a neighbouring cell formed by another second radio node as a second part of an outward link via an uplink channel of the wireless access interface, andto receive radio signals via the wireless access interface of the neighbouring cell formed by the other second radio node as a first part of a return link via a downlink channel of the wireless access interface and to transmit the radio signals via the wireless access interface of the cell formed by the second radio node as a second part of the return link via an uplink channel of the wireless access interface,to monitor a quality of communication via the outward link and the return link to determine a quality measure,based on the quality measure, to determine a radio link failure of one or both of the outward link and the return link, andto transmit the radio link failure to one or both of the second radio node and the other second radio node.

32. Circuitry for a second radio node (600.1, 600.2) which in combination with a first radio node (602.1, 602.2) provides a wireless access interface for a cell of a radio access network part of a wireless communications network, the circuitry comprisingtransceiver circuitry for transmitting, under control of the first radio node (602.1), radio signals via the wireless access interface to one or more communications devices and for receiving radio signals transmitted via the wireless access interface from the one or more communications devices, and receiving configuration information from the first radio node to form a wireless over-the-air, OTA, interface (700, 712) between the second radio node (600.1, 600.2) and another second radio node (600.1, 600.2), the wireless OTA interface comprising an outward link for transmitting control information from the second radio node (600.1, 600.2) to the other second radio node (600.1, 600.2) and a reverse link for receiving control information by the second radio node (600.1, 600.1) from the other second radio node (600.1, 600.2), the control information for supporting the transmission and / or reception of the radio signals via the wireless access interface by the one or more communications devices.

33. A non-transitory computer-readable storage medium storing a computer program, which when executed by a processor, performs the method according to claim 1 or 21.

34. A computer program, which when executed by a processor, performs the method according to claim 1 or 21.

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