Methods, communications devices, and infrastructure equipment

Abstract

A method of operating a communications device is provided. The method comprises receiving, from a source infrastructure equipment with which the communications device is connected, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the source infrastructure equipment to the target infrastructure equipment. Here, the LTM handover procedure consists of signalling only at a physical layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device.

Description

[0001] METHODS, COMMUNICATIONS DEVICES, AND INFRASTRUCTURE EQUIPMENT

[0002] BACKGROUND

[0003] Field of Disclosure

[0004] The present disclosure relates to communications devices and infrastructure equipment of wireless communications networks and methods of operating such communications devices and infrastructure equipment for the more efficient handling of mobility procedures in such wireless communications networks.

[0005] The present application claims the Paris Convention priority from European patent application number EP24166067.9, filed on 25 March 2024, the contents of which are hereby incorporated by reference.

[0006] Description of Related Art

[0007] 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.

[0008] Previous generation mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) architecture, are able to support a wider range of services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. For example, with the improved radio interface and enhanced data rates provided by LTE systems, a user is able to enjoy high data rate applications such as mobile video streaming and mobile video conferencing that would previously only have been available via a fixed line data connection. The demand to deploy such networks is therefore strong and the coverage area of these networks, i.e. geographic locations where access to the networks is possible, is expected to continue to increase rapidly.

[0009] Current and future wireless communications networks are expected to routinely and efficiently support communications with an ever-increasing range of devices associated with a wider range of data traffic profiles and types than existing systems are optimised to support. For example, it is expected future wireless communications networks will be expected to efficiently support communications with devices including reduced complexity devices, machine type communication (MTC) devices, high resolution video displays, virtual reality headsets, extended Reality (XR) 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).

[0010] In view of this there is expected to be a desire for current wireless communications networks, for example those which may be referred to as 5G or new radio (NR) systems / new radio access technology (RAT) systems, or indeed future 6G wireless communications, as well as future iterations / releases of existing systems, to efficiently support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles and requirements. The desire to support these new use-cases and scenarios gives rise to new challenges for efficiently handling communications in wireless communications systems that need to be addressed.

[0011] SUMMARY OF THE DISCLOSURE

[0012] The present disclosure can help address or mitigate at least some of the issues discussed above.

[0013] Some embodiments of the present technique can provide a method of operating a communications device. The method comprises receiving, from a source infrastructure equipment with which the communications device is connected, one or more conditional lower-layer triggered mobility (LTM) handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the source infrastructure equipment to the target infrastructure equipment. Here, the LTM handover procedure consists of signalling only at a physical layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control (MAC) layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device.

[0014] Such embodiments of the present technique, which, in addition to methods of operating communications devices, relate to methods of operating infrastructure equipment, to communications devices and infrastructure equipment, to circuitry for communications devices and infrastructure equipment, wireless communications systems, computer programs, and computer-readable storage mediums, can allow for the more efficient handling of mobility procedures in such wireless communications networks.

[0015] Respective aspects and features of the present disclosure are defined in the appended claims.

[0016] 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.

[0017] BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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:

[0019] Figure 1 schematically represents some aspects of an LTE-type wireless telecommunication system which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0020] Figure 2 schematically represents some aspects of an NR-type wireless telecommunications system which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0021] Figure 3 is a schematic block diagram of an example infrastructure equipment and communications device which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0022] Figure 4A is a representation of a gNB distributed unit (DU) and a gNB controlling unit (CU) communicating via an Fl interface; Figure 4B is a schematic representation of a protocol stack operated respectively by the gNB DU and gNB CU shown in Figure 4A for communicating control plane data;

[0023] Figure 4C is a schematic representation of a protocol stack operated respectively by the gNB DU and gNB CU shown in Figure 4A for communicating user plane data;

[0024] Figure 5 schematically illustrates a split of gNB functionality between a CU-CP, CU-UP and the DU according to current architecture;

[0025] Figure 6 is a schematic block diagram of an example of a source infrastructure equipment controlling handover of a communications device to a target infrastructure equipment;

[0026] Figure 7 schematically represents a conventional conditional handover procedure;

[0027] Figure 8 illustrates the scope of Uayer 1 / Uayer 2 Triggered Mobility (UTM) in current 3GPP specifications;

[0028] Figure 9 is reproduced from [6], and shows an example message sequence for UTM in accordance with current 3 GPP specifications;

[0029] Figure 10 shows a part schematic, part message flow diagram representation of a wireless communications system comprising a communications device and an infrastructure equipment in accordance with embodiments of the present technique;

[0030] Figure 11 shows a first message flow diagram illustrating how an UTM cell switch command with execution conditions may be signalled in accordance with embodiments of the present technique;

[0031] Figure 12 shows a second message flow diagram illustrating how resources for target cells included in an UTM cell switch command may be allocated, released, or activated in accordance with embodiments of the present technique; and

[0032] Figure 13 shows a third message flow diagram illustrating how a user equipment (UE) may synchronise with a gNB in the downlink and uplink before transmission of an UTM cell switch command in accordance with embodiments of the present technique.

[0033] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Long Term Evolution Advanced Radio Access Technology (4G)

[0035] Figure 1 provides a schematic diagram illustrating some basic functionality of a mobile telecommunications network / system 6 operating generally in accordance with LTE principles, but which may also support other radio access technologies, and which may be adapted to implement embodiments of the disclosure as described herein. Various elements of Figure 1 and certain aspects of their respective modes of operation are well-known and defined in the relevant standards administered by the 3GPP (RTM) body, and also described in many books on the subject, for example, Holma H. and Toskala A [1], It will be appreciated that operational aspects of the telecommunications networks discussed herein which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to the relevant standards and known proposed modifications and additions to the relevant standards.

[0036] The network 6 includes a plurality of base stations 1 connected to a core network 2, which may be for example an Evolved Packet Core (EPC). Each base station provides a coverage area 3 (i.e., a cell) within which data can be communicated to and from communications devices 4. Although each base station 1 is shown in Figure 1 as a single entity, the skilled person will appreciate that some of the functions of the base station may be carried out by disparate, inter-connected elements, such as antennas (or antennae), remote radio heads, amplifiers, etc. Collectively, one or more base stations may form a radio access network.

[0037] Data is transmitted from base stations 1 to communications devices 4 within their respective coverage areas 3 via a radio downlink (DL). Data is transmitted from communications devices 4 to the base stations 1 via a radio uplink (UL). The core network 2 routes data to and from the communications devices 4 via the respective base stations 1 and provides functions such as authentication, mobility management, charging and so on. Terminal devices may also be referred to as mobile stations, user equipment (UE), user terminal, mobile radio, communications device, and so forth. Services provided by the core network 2 may include connectivity to the internet or to external telephony services. The core network 2 may further track the location of the communications devices 4 so that it can efficiently contact (i.e., page) the communications devices 4 for transmitting downlink data towards the communications devices 4.

[0038] Base stations, which are an example of network infrastructure equipment, may also be referred to as transceiver stations, nodeBs, e-nodeBs, eNB, g-nodeBs, gNB and so forth. In this regard different terminology is often associated with different generations of wireless telecommunications systems for elements providing broadly comparable functionality. However, certain embodiments of the disclosure may be equally implemented in different generations of wireless telecommunications systems, and for simplicity certain terminology may be used regardless of the underlying network architecture. That is to say, the use of a specific term in relation to certain example implementations is not intended to indicate these implementations are limited to a certain generation of network that may be most associated with that particular terminology.

[0039] New Radio Access Technology (5G)

[0040] 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 2. In Figure 2 a plurality of transmission and reception points (TRPs) 10 are connected to distributed control units (DUs) 41, 42 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 41, 42 are connected to a central unit (CU) 40 (which may be referred to as a controlling node) via an interface 46. The central unit 40 is then connected to the core network 20 (which may be for example referred to as 5GC) which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network 20 may be connected to other networks 30.

[0041] The elements of the wireless access network shown in Figure 2 may operate in a similar way to corresponding elements of an LTE network as described with regard to the example of Figure 1. It will be appreciated that operational aspects of the telecommunications network represented in Figure 2, and of other networks discussed herein in accordance with embodiments of the disclosure, which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to currently used approaches for implementing such operational aspects of wireless telecommunications systems, e.g. in accordance with the relevant standards.

[0042] The TRPs 10 of Figure 2 may in part have a corresponding functionality to a base station or eNodeB of an LTE network. Similarly, the communications devices 14 may have a functionality corresponding to the UE devices 4 known for operation with an LTE network. It will be appreciated therefore that operational aspects of a new RAT network (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be different to those known from LTE or other known mobile telecommunications standards. However, it will also be appreciated that each of the core network component, base stations and communications devices of a new RAT network will be functionally similar to, respectively, the core network component, base stations and communications devices of an LTE wireless communications network.

[0043] In terms of broad top-level functionality, the core network 20 connected to the new RAT telecommunications system represented in Figure 2 may be broadly considered to correspond with the core network 2 represented in Figure 1, and the respective central units 40 and their associated distributed units / TRPs 10 may be broadly considered to provide functionality corresponding to the base stations 1 of Figure 1. The term network infrastructure equipment / access node may be used to encompass these elements and more conventional base station type elements of wireless telecommunications systems. Depending on the application at hand the responsibility for scheduling transmissions which are scheduled on the radio interface between the respective distributed units and the communications devices may lie with the controlling node / central unit and / or the distributed units / TRPs. A communications device 14 is represented in Figure 2 within the coverage area of the first communication cell 12. This communications device 14 may thus exchange signalling with the first central unit 40 in the first communication cell 12 via one of the distributed units / TRPs 10 associated with the first communication cell 12.

[0044] It will further be appreciated that Figure 2 represents merely one example of a proposed architecture for a new RAT based telecommunications system in which approaches in accordance with the principles described herein may be adopted, and the functionality disclosed herein may also be applied in respect of wireless telecommunications systems having different architectures.

[0045] Thus, certain embodiments of the disclosure as discussed herein may be implemented in wireless telecommunication systems / networks according to various different architectures, such as the example architectures shown in Figures 1 and 2. It will thus be appreciated the specific wireless telecommunications architecture in any given implementation is not of primary significance to the principles described herein. In this regard, certain embodiments of the disclosure may be described generally in the context of communications between network infrastructure equipment / access nodes and a communications device, wherein the specific nature of the network infrastructure equipment / access node and the communications device will depend on the network infrastructure for the implementation at hand. For example, in some scenarios the network infrastructure equipment / access node may comprise a base station, such as an LTE-type base station 1 as shown in Figure 1 which is adapted to provide functionality in accordance with the principles described herein, and in other examples the network infrastructure equipment may comprise a control unit / controlling node 40 and / or a TRP 10 of the kind shown in Figure 2 which is adapted to provide functionality in accordance with the principles described herein.

[0046] A more detailed diagram of some of the components of the network shown in Figure 2 is provided by Figure 3. In Figure 3, a TRP 10 as shown in Figure 2 comprises, as a simplified representation, a wireless transmitter 30, a wireless receiver 32 and a controller or controlling processor 34 which may operate to control the transmitter 30 and the wireless receiver 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 3, an example UE 14 is shown to include a corresponding transmitter 49, a receiver 48 and a controller 44 which is configured to control the transmitter 49 and the receiver 48 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 30 and received by the receiver 48 in accordance with the conventional operation. The transmiters 30, 49 and the receivers 32, 48 (as well as other transmiters, receivers and transceivers described in relation to examples and embodiments of the present disclosure) may include radio frequency fdters 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. The controllers 34, 44 (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 transmiters, the receivers and the controllers are schematically shown in Figure 3 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.

[0047] As shown in Figure 3, the TRP 10 also includes a network interface 50 which connects to the DU 42 via a physical interface 16. The network interface 50 therefore provides a communication link for data and signalling traffic from the TRP 10 via the DU 42 and the CU 40 to the core network 20.

[0048] The interface 46 between the DU 42 and the CU 40 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 3GPP technical specifications [2] and [3], 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 from the network interface 50 of the TRP 10 to the DU 42 and the Fl interface 46 from the DU 42 to the CU 40.

[0049] As will be appreciated by those acquainted with 5G architecture, the CU 40 may be a logical node which hosts Radio Resource Control (RRC) protocols, Service Data Adaptation Protocols (SDAP), and Packet Data Convergence Protocols (PDCP) of a gNB. Alternatively, the CU 40 may be a logical node which hosts RRC and PDCP protocols of an en-gNB (which is a gNB that is able to connect with both EPC and eNBs and can be understood as being, for example, a secondary node (SgNB) used in dual connectivity scenarios). The CU 40 partly controls the operation of one or more DUs 40 and terminates the Fl interface 46 for the DUs that it controls. The DU 42 may be a logical node which hosts Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of a gNB or en-gNB. The operation of the DU 42 is partly controlled by the CU 40 for which the DU 42 terminates the F 1 interface 46.

[0050] Although not shown in Figures 2 or 3, it will be familiar to those acquainted with 5G architecture that the CU 40 may be further split into a CU-CP which performs the control plane functions of the CU 40 and a CU-UP which performs the user plane functions of the CU 40 (see for example, [4]). In more detail, the CU-CP may be 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 42. As will be appreciated, the Fl -C interface carries control plane signalling of the Fl interface 46. The CU-UP may be 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 may be a logical node which hosts a user plane part of the PDCP protocol and an SDAP protocol of the CU 40 for a gNB. The CU-UP terminates an El interface connected with the CU-CP and an Fl-U interface connected with the DU 42. As will be appreciated, the Fl-U interface carries user plane signalling of the Fl interface 46.

[0051] In order to appreciate example embodiments, a protocol stack for forming a conventional F 1 interface shown in Figure 2 and 3 will be explained with reference to Figures 4A, 4B, and 4C. In respect of a protocol stack, Figures 4A, 4B, and 4C provide an illustration of processing performed by the elements shown in Figures 2 and 3 which form the packet data communications path 46 between the gNB-DU 42 and the gNB-CU 40 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.

[0052] As shown in Figure 4A, communication is formed between the gNB DU 42 and a gNB CU 40 for the Fl interface 46. However, the control plane protocol stack to form this interface is shown in Figure 4B, and the user plane protocol stack for communicating the user data between the gNB-CU 40 and gNB-DU 42 is shown in Figure 4C. As shown in Figure 4B, at the radio network layer, the control plane is formed by Fl Application Protocols (FlAPs) 301a in the gNB-CU 40 and by Fl APs 301b in the gNB DU 42. 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 [5], This is shown in Figure 4B 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.

[0053] In the user plane, the radio network layer is formed by REC layer 320a, 320b to form the Fl interface for communicating use plane data 46. The protocol stack in the transport layer comprises a General Packet Ratio Service (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.

[0054] CU-DU Split Functions

[0055] 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 [6] . Such gNB functions include:

[0056] • Functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (scheduling);

[0057] • IP and Ethernet header compression, encryption and integrity protection of data;

[0058] • Selection of an Access and Mobility Management Function (AMF) at UE attachment when no routing to an AMF can be determined from the information provided by the UE;

[0059] • Routing of User Plane data towards User Plane Functions (UPFs);

[0060] • Routing of Control Plane information towards AMF;

[0061] • Connection setup and release;

[0062] • Scheduling and transmission of paging messages; • Scheduling and transmission of system broadcast information (originated from the AMF or 0AM);

[0063] • Measurement and measurement reporting configuration for mobility and scheduling;

[0064] • Transport level packet marking in the uplink;

[0065] • Session Management;

[0066] • Support of Network Slicing;

[0067] • QoS Flow management and mapping to data radio bearers;

[0068] • Support of UEs in RRC INACTIVE state;

[0069] • Distribution function for NAS messages;

[0070] • Radio access network sharing;

[0071] • Dual Connectivity;

[0072] • Tight interworking between NR and E-UTRA; and

[0073] • Maintain security and radio configuration for User Plane Cellular Internet of Things (CIoT) 5GS Optimisation, as defined in [7] (ng-eNB only).

[0074] All functions listed above, except for the final function, can be performed by gNBs and ng-eNBs while the final function relating to the maintenance of security and radio configurations is performed by ng- eNBs only. As those skilled in the art would understand, an ng-eNB is an eNB which connects 5G UEs to the 5G core network using 4G LTE air interface. Furthermore, bandwidth reduced low complexity (BL) UEs or UEs in enhanced coverage are only supported by ng-eNBs (see, for example, [8]). Additionally, NB-IoT UE is only supported by ng-eNBs (see, for example, [8]).

[0075] As will be appreciated, 5G networks are currently deployed in millimetre wave band. However, due to the higher communication bandwidths that can be achieved at higher frequencies, there is an increased demand for wireless communications at higher frequencies in 5G networks. The use of higher frequencies in wireless communications leads to increased path loss and therefore smaller cell sizes than if lower frequencies were used. As a result, in order to achieve suitable coverage, a dense deployment of networks may be required.

[0076] A dense deployment of networks creates a number of technical challenges for the current 5G architecture as explained with reference to Figures 2 and 3. For example, as mentioned previously, the DU 42 and the CU 40 may be connected over a wired connection 46 such as fibre optic. Therefore, a dense deployment of networks may increase the number of required wired connections which may not always be possible. Furthermore, the use of wired connections 46 between the CU 40 and the DU may lead to increased latency due to current topology designs. For example, as will be appreciated from Figure 2, two DUs 41, 42 are connected to the CU 40 via wired connections 46 in a “tree topology”. Therefore, if any direct signalling is required between two cells 12 (for example, one cell provided by DU 41 and one cell provided by DU 42) then such signalling must propagate via the CU 40. This can lead to congestion and increased latency, especially when a large number of cells are deployed in close proximity, such as in dense deployment scenarios.

[0077] Furthermore, as will be explained in more detail with reference to Figure 5, a higher cell density creates technical challenges in providing cell mobility and interference management. Figure 5 illustrates a split of gNB functionality between a CU-CP 40a, CU-UP 40b and the DU 42 according to current 5G architectures. The CU-CP 40a and CU-UP 40b are logical nodes which perform the functions of the CU 40 described with reference to Figures 2, 3, and 4. As shown in Figure 5, the CU-CP 40a is configured to perform radio resource management (RRM) functions 402, Radio Resource Control (RRC) functions 403, Packet Data Convergence Protocol Control Plane (PDCP-CP) functions 404, Security functions 406, Non-Access Stratum (NAS) functions 408, user equipment (UE) context functions 410, and Quality of Service (QoS) functions 412. The CU-UP 40b is configured to perform Packet Data Convergent Protocol User Plane (PDCP-UP) functions 414. The DU 42 is configured to perform REC functions 416, MAC functions 418, PHY functions 420. As will be appreciated, a scheduler in the DU 42 may be implemented based on the guidelines as mentioned in section 10 of [6],

[0078] Conventional Handover (HO)

[0079] A detailed illustration of a wireless communications network in which a handover may be performed is shown in Figure 6. As will be appreciated from Figure 6, a communications device 502 is handed over from a source cell provided by a source infrastructure equipment 504 to a target cell provided by the target infrastructure equipment 506. The source and target cells are not shown in Figure 6 for clarity, although it will be appreciated that the source and target cells may broadly correspond to cells 3, 12 as discussed in relation to Figures 1 and 2 above. The source infrastructure equipment 504 and target infrastructure equipment 506 form part of a radio access network to a core network 508. As will be appreciated the communications device 502 is an example of a communications device such as the MT 4 of Figure 1 or the UE 14 of Figures 2 and 3.

[0080] Before the handover, the communications device 502 transmits signals on an uplink UL and receives signals on a downlink DL from a source infrastructure equipment 504. The source infrastructure equipment 504 and the target infrastructure equipment 506 may each be thought of as a gNB 101 or a combination of a controlling node 221 and TRP 211. Before the handover, the communications device 502 is shown to transmit uplink data to the source infrastructure equipment 504 via uplink resources UL of a wireless access interface as illustrated generally by dashed arrow 574b to the source infrastructure equipment 504. The communications device 502 may similarly be configured to receive downlink data transmitted by the source infrastructure equipment 504 via downlink resources DL as indicated by dashed arrow 588b from the source infrastructure equipment 504 to the communications device 502. After the handover, the communications device 502 is shown to transmit uplink data to the target infrastructure equipment 506 via uplink resources UL of a wireless access interface as illustrated generally by solid arrow 588a to the target infrastructure equipment 506. The communications device 502 may similarly be configured to receive downlink data transmitted by the target infrastructure equipment 506 via downlink resources DL as indicated by solid arrow 574a from the target infrastructure equipment 506 to the communications device 502.

[0081] In Figure 6, the source and target infrastructure equipment 504, 506 are each connected to a core network 508 via interfaces 578, 579 to a controller 504c, 506c of the respective infrastructure equipment 504. The source and target infrastructure equipment 504, 506 each include a receiver 504b, 506b connected to an antenna 504d, 506d and a transmitter 504a, 506a connected to the antenna 504d, 506d. Correspondingly, the communications device 502 includes a controller 502c connected to a receiver 502b which receives signals from an antenna 502d and a transmitter 502a also connected to the antenna 502d.

[0082] The controllers 504c, 506c are configured to control the source and target infrastructure equipment 504, 506 respectively and may comprise processor circuitry which may in turn comprise various sub-units / sub-circuits for providing functionality as explained further herein. These sub-units may be implemented as discrete hardware elements or as appropriately configured functions of the processor circuitry. Thus, the controllers 504c, 506c may comprise circuitry which is suitably configured / programmed to provide the desired functionality using conventional programming / configuration techniques for equipment in wireless telecommunications systems. The transmitters 504a, 506a and the receivers 504b, 506b may comprise signal processing and radio frequency filters, amplifiers and circuitry in accordance with conventional arrangements. The transmitters 504a, 506a the receivers 504b, 506b and the controllers 504c, 506c are schematically shown in Figure 6 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 504 will in general comprise various other elements associated with its operating functionality.

[0083] Correspondingly, the controller 502c of the communications device 502 is configured to control the transmitter 502a and the receiver 502b and may comprise processor circuitry which may in turn comprise various sub-units / sub-circuits for providing functionality as explained further herein. These sub-units may be implemented as discrete hardware elements or as appropriately configured functions of the processor circuitry. Thus the controller 502c may comprise circuitry which is suitably configured / programmed to provide the desired functionality using conventional programming / configuration techniques for equipment in wireless telecommunications systems. Likewise, the transmitter 502a and the receiver 502b may comprise signal processing and radio frequency filters, amplifiers and circuitry in accordance with conventional arrangements. The transmitters 502a, receivers 502b, and controllers 502c are schematically shown in Figure 6 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 communications device 502 will in general comprise various other elements associated with its operating functionality, for example a power source, user interface, and so forth, but these are not shown in Figure 6 in the interests of simplicity.

[0084] The controllers 504c, 502c may be 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.

[0085] Conventional Conditional Handover (CHO)

[0086] Aspects of NR are concerned with mobility enhancements and in particular with increasing mobility robustness for new services which require low latency and high reliability performance (such as URLLC). Situations may arise where a cell currently serving a UE may no longer be suitable or a radio link between the UE and a source gNB providing coverage in the cell is degraded. In such situations, it is generally desirable for the UE to switch to being served by a cell of a target gNB. One way of configuring a handover of a UE from a source gNB to a target gNB is referred to as a “conditional handover”.

[0087] An example of a conditional handover (CHO) is illustrated in Figure 7 which is reproduced from [6], the contents of which are incorporated by reference in their entirety. Figure 7 schematically represents communications in a wireless communications network between the communications device 502, the source infrastructure equipment 504, the target infrastructure equipment 506, other potential target infrastructure equipment 511, an Access Mobility and Mobility Management Function (AMF) 512 and a User Plane Function (UPF) 514. In Figure 7, the source infrastructure equipment 504, the target infrastructure equipment 506, other potential target infrastructure equipment 511 are depicted as “gNBs”, although it will be appreciated that other infrastructure equipment of a wireless communications network could be used (such as eNBs for example). The AMF 512 and UPF 514 are functions in a core network of the wireless communications network (such as core network 508). As shown in Figure 7, before a handover, the communications device 502 communicates user plane data with the AMF 512 and UPF 514 via the source infrastructure equipment 504. In step 0, the AMF 512 provides mobility control information to the source infrastructure equipment 504. In step 1, the communications device 502 reports measurements to the source infrastructure equipment 504. Such measurements may include measurements performed by the communications device 502 such as a Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ) and / or a Signal- to-Interference Ratio (SINR) of reference signals from the source infrastructure equipment 504, the target infrastructure equipment 506 and / or the other potential target infrastructure equipment 511. In step 2, the source infrastructure equipment 504 determines to configure the communications device 502 for a conditional handover. In step 3, the source infrastructure equipment 504 transmits a handover request to the target infrastructure equipment 506 and the other potential target infrastructure equipment 511. In response, in step 4, the target infrastructure equipment 506 and the other potential target infrastructure equipment 511 perform admission control. Then, in step 5, the target infrastructure equipment 506 and the other potential target infrastructure equipment 511 transmit a handover request acknowledgement to the source infrastructure equipment 504.

[0088] In response to receiving the handover request acknowledgement, the source infrastructure equipment 504 transmits, in step 6, a conditional handover configuration message to the communications device 502. The conditional handover configuration message may be a Radio Resource Control (RRC) configuration message. The conditional handover configuration message includes one or more conditions for triggering a handover of the communications device 502 from a source cell provided by the source infrastructure equipment 504. For example, the one or more conditions in the conditional handover configuration message may include one or more conditions to be met for triggering a handover to target cell provided by the target infrastructure equipment 506 and one or more other conditions to be met for triggering a handover to the other target cells provided by other potential target infrastructure equipment 511. The conditions included in the conditional handover configuration message are explained in more detail below. After receiving the conditional handover configuration message, the communications device 502 transmits an RRC reconfiguration complete message to the source infrastructure equipment 504. After receiving the conditional handover configuration message, the communications device 502 may continuously or periodically evaluate the conditions included in the handover configuration message for triggering the handover to determine whether the conditions for triggering the handover have been met.

[0089] When the communications device 502 determines that conditions for triggering the handover have been met, the communications device 502 initiates the handover. For example, the communications device 502 detaches from the source cell provided by the source infrastructure equipment 504 and attaches to the target cell provided by the target infrastructure equipment 506. In the example shown in Figure 7, the communications device 502 determines that the conditions for triggering a handover to the target infrastructure equipment 506 are met. While the communications device 502 is evaluating the conditions, the source infrastructure equipment 604 transmits an early status transfer to the other potential target infrastructure equipment in step 7a, and subsequent user data from the UPF 514 is routed to the other potential target infrastructure equipment 511 via the source infrastructure equipment 504. In step 8, the target infrastructure equipment 506 determines that the handover of the communications device 502 from the source cell provided by the source infrastructure equipment 504 to the target cell provided by the target infrastructure equipment 506 has been successful.

[0090] In response, the target infrastructure equipment 506 transmits a handover success message to the source infrastructure equipment 504 in step 8a. In step 8b, the source infrastructure equipment 504 transmits an SN status transfer message to the target infrastructure equipment 506. Subsequent user data from the UPF 514 to the source infrastructure equipment is routed to the target infrastructure equipment 506. In step 8c, a handover cancel message is transmitted from the source infrastructure equipment 504 to the target infrastructure equipment and the other potential target infrastructure equipment 511.

[0091] As mentioned above in step 6 of Figure 7, the source infrastructure equipment 504 may transmit a conditional handover configuration message to the communications device 502 including one or more conditions for triggering the handover.

[0092] An example of a condition to be met for triggering a handover of the communications device 502 is “event A3” based on Layer 3 (L3) measurement. The condition defined by event A3 is met if a signal quality of a cell provided by a neighbouring infrastructure equipment (for example, the target infrastructure equipment 506 or the other potential target infrastructure equipment 511) becomes a predefined offset higher than the signal quality of a cell provided by the source infrastructure equipment 504. Another example of a condition to be met for triggering a handover of the communications device 502 is “event A4” based on L3 measurement. The condition defined by event A4 is met if the signal quality of the cell provided by the neighbouring infrastructure equipment is greater than an absolute threshold. Another example of a condition to be met for triggering a handover of the communications device 502 is “event A5” based on L3 measurement. The condition defined by event A5 is met if the signal quality of the cell provided by the source infrastructure equipment 504 is less than an absolute threshold and the signal quality of the neighbouring infrastructure equipment is greater than an absolute threshold.

[0093] The “signal quality” mentioned above in respect of the definitions of events A3, A4 and A5 may be measured by the communications device 502 using one or more signal quality parameters such as RSRP, RSRQ and SINR. For example, the communications device 502 may determine that condition outlined in event A3 may be met if a measured RSRP of the cell provided by the neighbouring infrastructure equipment becomes a pre-defined offset higher than the measured RSRP for the cell provided by the source infrastructure equipment 504. In another example, may determine that condition outlined in event A3 is met if a measured RSRP and RSRQ of the cell provided by the neighbouring infrastructure equipment each respectively become a pre-defined offset higher than the measured RSRP and RSRQ for the cell provided by the source infrastructure equipment 504. In Release-16 of standards of the 3GPP group, only one reference signal type and measurements of at most two signal quality parameters are supported in determining whether event A3, A4 and / or A5 are met.

[0094] Each of events A3, A4 and A5 therefore each represent a condition for triggering a handover of the communications device 502 from the source infrastructure equipment 504. In order to trigger the handover, it may be sufficient that only one condition included in the conditional handover configuration message is met, or the triggering of the handover may require more than one or all of the conditions in the conditional handover configuration message to be met. In one example, only event A3 is included as a condition and the handover is triggered if event A3 is met. In another example, both events A3 and A4 are included as conditions and the handover is triggered if either event A3 or A4 is met. In another example, both events A3 and A4 are included as conditions and the handover is triggered if both events A3 or A4 are met.

[0095] Layer 1 / Layer 2 Triggered Mobility (LTM)

[0096] Release 18 of the 3GPP standards specified intra-CU - both intra-DU and inter-DU - Ll / 2 Triggered Mobility (LTM). LTM may alternatively stand for “Lower-layer Triggered Mobility”. The operation of LTM itself will be described in more detail in the paragraphs below, but in simplistic terms, as would be well understood by those skilled in the art, LTM refers to UE mobility which is controlled entirely by layer 1 (i.e. the physical layer) and layer 2 (i.e. the data link layer, or more specifically, MAC layer) of the 5G protocol stack. Both intra-DU and inter-DU LTM (both intra-CU) can be understood with reference to Figure 8. As can be seen in the example of Figure 8, two DUs 82, 83 are connected to a single CU 81. Each DU 82, 83 supports two cells, with DU 82 supporting cells 84 and 85, and DU 83 supporting cells 86 and 87. In intra-CU ETM a UE is handed over between a source and target cell which are both under control (via the same or separate DUs) of the same CU, such as CU 81 of Figure 8. For intra-DU LTM, handover may be triggered and controlled by layers 1 and 2 for a UE between cells 84 and 85 (controlled by the same DU 82) or cells 86 and 87 (controlled by the same DU 83). For inter-DU LTM, handover may be triggered and controlled by layers 1 and 2 for a UE between one of cells 84 and 85 (controlled by DU 82) and one of cells 86 and 87 (controlled by DU 83) - e.g., inter-DU LTM may involve the UE handing over from cell 87 to cell 84. Inter-CU LTM is not yet specified in the 3GPP standards at the priority date of the present disclosure, but is expected to be specified in Release 19 of the 3GPP standards.

[0097] A proposed message sequence for LTM is as shown in Figure 9, which is reproduced from [6] in which it is included as Figure 9.2.3.5.2-1. The detailed procedure for LTM, as shown in Figure 9, is described in [6], and the description of Figure 9 in the paragraph below is based on that description in [6] and included herein for the purpose of aiding a better understanding of LTM.

[0098] In step 1, the UE 91 (while in RRC_CONNECTED mode) sends MeasurementReport message based on L3 measurement to the gNB 92. The gNB 92 decides to use LTM and initiates candidate cell(s) preparation. In step 2, the gNB 92 transmits an RRCReconfiguration message to the UE 91 including the LTM candidate cell configurations of one or multiple candidate cells. In step 3, the UE 91 stores the LTM candidate cell configurations and transmits a RRCReconfigurationComplete message to the gNB 92. In step 4a, the UE 91 may perform DL synchronisation with candidate cell(s) before receiving the cell switch command, and in step 4b, the UE 91 may perform early timing advance (TA) acquisition with candidate cell(s) before receiving the cell switch command. This is done via Contention Free Random Access (CFRA) triggered by a Physical Downlink Control Channel (PDCCH) order from the source cell, following which the UE 91 sends a preamble towards a candidate cell. The information that identifies the allocated CFRA resource can be indicated in the PDCCH order to enable shared preamble resource among multiple UEs 91. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the UE 91 either receives a Random Access Response (RAR) from the source cell instead of the candidate cell or doesn’t receive a RAR at all. Whether a RAR needs to be received is configured by the network and specific per each candidate cell. If RAR is not needed, the TA value of the candidate cell is indicated in the cell switch command.

[0099] In step 5, the UE 91 performs LI measurements on the configured candidate cell(s), and transmits lower- layer measurement reports to the gNB 92. Then, in step 6, the gNB 92 decides to execute cell switch to a target cell, and transmits a MAC control element (CE) triggering cell switch by including the candidate configuration index of the target cell. The UE 91 switches to the configuration of the target cell. In step 7, the UE 91 performs a random -access procedure towards the target cell, if the cell switch needs to include the performance of such a random-access procedure. Finally, in step 8, the UE 91 completes the LTM cell switch procedure by sending an RRCReconfigurationComplete message to the target cell. For random access (RACH)-based LTM, the UE 91 considers that LTM execution procedure is successfully completed when the random-access procedure itself is successfully completed. For RACH-less LTM, the UE 91 considers that LTM execution procedure is successfully completed when the UE 91 determines that the network has successfully received its first UL data. The UE 91 can perform steps 4 to 8 as shown in Figure 9 multiple times for subsequent LTM cell switch based on the configuration provided in step 2.

[0100] In [9], it is noted that some mobility enhancements for LTM should be specified, in respect of which several objectives are described. These objectives are reproduced from [9] below. • Specify support for inter-CU Layer 2 Mobility (LTM) [RAN2, RAN3]: o Prioritise the case when CU is acting as MN when DC is not configured; o As secondary priority, support the case when NR-DC is configured and CU is acting as SN and MCG is unchanged; o As secondary priority, support the case when NR-DC is configured, CU is acting as MN and SCG is unchanged or SCG is released;

[0101] ■ Note: The case that LTM is configured in both MCG and SCG is excluded; o Specify support for subsequent LTM mobility procedures aiming to avoid RRC; configuration between cell switches as per Rel-18 LTM;

[0102] ■ Coordination with SA3 needed with respect to security key handling; o Note: Rel. 18 intra-CU LTM procedure is considered as baseline for adding inter-CU support;

[0103] • Measurements related enhancements for purpose of supporting LTM: [RAN2, RANI]: o Measurement related enhancements are applicable to Intra-CU MCG / SCG LTM and Inter- CU MCG / SCG LTM; o Specify necessary components to support event triggered LI measurement reporting [RAN2, RANI];

[0104] ■ RAN 1 and RAN2 to progress independently on the event triggered measurements objectives of their respective MIMO and Mobility enhancement WIs. Review progress at RAN# 105 to see if any modification of objectives is required to avoid / manage any overlap in the work; o Specify support for CSI-RS measurements for LTM procedures and enable CSI-RS based beam management, and / or other necessary physical layer operations on candidate cells before LTM [RANI];

[0105] • Specify support of conditional LTM [RAN2, RAN3, RANI]; o Specify UE evaluated conditions for triggering LTM; o Aim to support conditional LTM including subsequent LTM; o Prioritise intra-CU LTM; o Checkpoint to review obj ective at RAN# 105. RAN WG work to not start before this checkpoint; and

[0106] • Specify RRM requirements related to the above objectives as necessary [RAN4],

[0107] The common understanding is that in conditional L1 / L2 triggered mobility (LTM), like in conventional conditional handover (CHO), it is up to the network to configure the conditions (e.g., based on LI measurements) for a UE to evaluate. Once these configured condition(s) being evaluated by the UE are met, the LTM will be executed by that UE. However, it is not clear from known solutions what the detailed signalling would be for such conditional LTM. For example, it is currently not known or defined what the conditions should be, or in which signal the configuration of such conditions should be provided, or what the UE’s expected behaviour may be, etc. In addition, resources (e.g., RACH or configured grant) for the target cell are allocated in the RRC reconfiguration message (i.e. step 2 of Figure 9). As these resources are pre-allocated for multiple candidate cells, even if the UE does not ultimately hand over to those candidate cells and hence such resources are not used, there is an issue of resource wastage (i.e., resources which are allocated but not ultimately used).

[0108] Hence, issues to be solved with respect to conditional LTM include how to minimise the resource consumption, as well as how such a conditional LTM command and the conditions thereof should be signalled, and how UEs should be configured to behave in response to receiving a conditional LTM command. Embodiments of the present disclosure seek to provide solutions to such problems. Conditional LTM Command

[0109] Figure 10 shows a part schematic, part message flow diagram representation of a wireless communications system comprising a source infrastructure equipment (e.g. gNB) 110, a target infrastructure equipment (e.g. gNB) 120, and a communications device 100 (e.g. a UE) in accordance with at least some embodiments of the present technique. The communications device 100, source infrastructure equipment 110, and target infrastructure equipment 120, each comprise a transceiver (or transceiver circuitry) 101, 111, 121, and a controller (or controller circuitry) 102, 112, 122. Each of the controllers 102, 112, 122 may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc. The controllers 102, 112, 122 may also each be equipped with a memory unit (which is not shown in Figure 10). The communications device 100 is connected initially to the source infrastructure equipment 110, which operates a serving cell within the coverage region of which the communications device 100 is located. The transceiver circuitry 101 and the controller circuitry 102 of the communications device 100 may therefore be (initially) configured to transmit signals to 131 and / or receive signals from 131 the source infrastructure equipment 110.

[0110] As shown in the example of Figure 10, the transceiver circuitry 101 and the controller circuitry 102 of the communications device 100 are configured in combination to receive 132, from the source infrastructure equipment 110 (with which the communications device 100 is connected) one or more conditional lower- layer triggered mobility (LTM) handover commands, wherein each conditional LTM handover command 132 comprises an indication of at least one target infrastructure equipment (e.g. the target infrastructure equipment 120) and an indication of one or more conditions that, if met, the communications device 100 is to perform an LTM handover procedure to hand over from the source infrastructure equipment 110 to the target infrastructure equipment 120. Here, the LTM handover procedure consists of signalling only at a physical layer at each of the source infrastructure equipment 110, the target infrastructure equipment 120, and the communications device 100 and / or a data link layer (e.g. medium access control (MAC) layer) at each of the source infrastructure equipment 110, the target infrastructure equipment 120, and the communications device 100.

[0111] Later, the transceiver circuitry 101 and the controller circuitry 102 of the communications device 100 may further be configured in combination to determine 133 that the one or more conditions indicated by one of the received conditional LTM handover commands 132 are satisfied, and to perform 134 the LTM handover procedure to hand the communications device 100 over from the source infrastructure equipment 110 to the target infrastructure equipment 120 indicated by the received conditional LTM handover command 132 for which the communications device 100 determines 133 that one or more conditions are satisfied. Following this, the communications device 100 is now connected to the target infrastructure equipment 120, and so the transceiver circuitry 101 and the controller circuitry 102 of the communications device 100 may be configured in combination to transmit signals to 135 and / or receive signals from 135 the target infrastructure equipment 120.

[0112] In arrangements of embodiments of the present technique as exemplified by Figure 9, the communications device 100 may receive one conditional LTM handover command 132, where such a conditional LTM handover command 132 may indicate a single target infrastructure equipment 120 and one (or more) conditional handover conditions associated with that single target infrastructure equipment 120. Alternatively, the one conditional LTM handover command 132 may indicate multiple target infrastructure equipment and one (or more) conditional handover conditions associated with each of those target infrastructure equipment (where the conditions may be different (e.g. different value s / thresholds / offsets or a different number of conditions to be met) for different target infrastructure equipment). Alternatively, the communications device 100 may receive multiple conditional LTM handover commands 132, where each conditional LTM handover command 132 comprises an indication of either one target infrastructure equipment and its associated conditional handover condition(s) or multiple target infrastructure equipment and their associated conditional handover condition(s). Where the communications device 120 receives multiple conditional LTM handover commands 132, each of those conditional LTM handover commands 132 may indicate different numbers of target infrastructure equipment and / or conditions with respect to one another.

[0113] Herein, reference is made interchangeably to “target infrastructure equipment" or “candidate infrastructure equipment" and “target cell” or “candidate cell”. Those skilled in the art would appreciate that such terms may be understood to mean substantially the same thing, or more specifically that a “target / candidate cell” is a cell controlled by a “target / candidate infrastructure equipment” . The same is true in respect of a “source infrastructure equipment” or “serving infrastructure equipment” being used interchangeably with (or in respect of being an infrastructure equipment / gNB that controls a) “source cell” or “serving cell”.

[0114] Essentially, such embodiments of the present technique as exemplified by Figure 10 propose that a UE receives an LTM command (or multiple LTM commands) that contains an indication of conditions that the UE is to evaluate. Here, if (and when) such conditions are satisfied, the UE is then to execute the LTM cell switch command for a particular target cell indicated in the LTM command and associated with those conditions.

[0115] In this case, the UE may receive one or more conditional LTM cell switch commands either in one MAC control element (MAC CE) or separate MAC CEs, for one or more target cells. In other words, the communications device may be configured to receive, from the source infrastructure equipment, a MAC CE, wherein the MAC CE comprises all of the one or more conditional LTM handover commands. Alternatively, the communications device may be configured to receive, from the source infrastructure equipment, one or more MAC CEs, wherein each of the MAC CEs comprises one of the one or more conditional LTM handover commands.

[0116] In some arrangements of embodiments of the present technique, the one or more conditions may comprise event A3, but specifically where measurements performed at the physical layer (i.e. LI measurements) of the target candidate cell become an offset better than the LI measurement of the serving cell. In other words, the one or more conditions may comprise a quality of physical layer signals received from the target infrastructure equipment being greater than a quality of physical layer signals received from the source infrastructure equipment by at least a predefined amount.

[0117] Alternatively, or in addition, in some arrangements of embodiments of the present technique, the one or more conditions may comprise event A4, but specifically where measurements performed at the physical layer (i.e. LI measurements) of the target candidate cell become better than a set threshold amount. In other words, the one or more conditions may comprise a quality of physical layer signals received from the target infrastructure equipment being greater than a predefined threshold.

[0118] Alternatively, or in addition, in some arrangements of embodiments of the present technique, the one or more conditions may comprise event A5, but specifically where measurements performed at the physical layer (i.e. LI measurements) of the target candidate cell become better than a set threshold amount while measurements performed at the physical layer (i.e. LI measurements) of the serving cell become worse than the set threshold amount. In other words, the one or more conditions may comprise a quality of physical layer signals received from the source infrastructure equipment being less than a predefined threshold and a quality of physical layer signals received from the target infrastructure equipment being greater than the predefined threshold. In general, the procedure proposed by arrangements of embodiments of the present technique as disclosed herein is substantially the same as the legacy LTM signalling procedure shown in Figure 9 and described above. However, embodiments of the present technique propose that the procedure of Figure 9 is modified to enable conditional LTM handover to be configured for UEs, and this is achieved by including an indication in the LTM cell switch command of one or more conditions to be satisfied before LTM handover is triggered.

[0119] This is illustrated by the example message flow diagram Figure 11, where the LTM cell switch command in step 6 of the procedure shown by Figure 9 is modified 141 to include some conditions a UE to evaluate before executing the cell switch command. In addition, as noted above, in step 6, a UE can receive one or more LTM commands 141 in one message (MAC CE) or separately (in multiple MAC CEs) to evaluate 142 whether the conditions are satisfied for each of a plurality of target cells. It should be noted here that while the UE is able to evaluate 142 the conditions for each cell, the UE will ultimately only switch to one cell at the end of the LTM handover procedure. The target cell that the UE ultimately switches to may be the first target cell for which the condition(s) associated with that cell is / are met, or may be a target cell - when condition(s) for multiple target cells is / are met - for which the signal quality (e.g. RSRP, RSRQ, SINR) is highest.

[0120] In the current LTM procedure (e.g. as shown in Figure 9), the resources (e.g., RACH, configured grant) for the target cell are allocated in the RRC reconfiguration message (i.e. in step 2 of Figure 9 as described above). For example, in order for a UE to switch to the target cell, the UE should transmit a RACH preamble to the target cell and the RACH resources for transmission of such a preamble can be preallocated for each candidate target cell based on contention-free random-access (CFRA) to determine the timing advance. Otherwise, the UE should apply contention-based RACH transmission to determine the timing advance.

[0121] In addition, for the RACH-less case where the UE knows the timing advance (for example, small cells where TA = 0 or where the UE derives the TA based on timing difference of the serving cell and the target cell), the UE utilises configured grant (CG) resources to transmit the first message (e.g., data) to indicate its arrival at the target cell. In the current LTM procedure, the CG resources are pre-allocated for each target cell in step 2 of Figure 9. However, in this case - as for the RACH case as described above - only the resources for the target cell to which the UE ultimately switches to are used, and the resources configured for all other candidate target cells will be wasted.

[0122] In some arrangements of embodiments of the present technique therefore, as shown in the example flow diagram of Figure 12, in order to minimize the resource consumption, the resources are allocated 143 between steps 5 and 6 (of the existing LTM procedure as shown in Figure 9) only for the target cells that are included in the LTM cell switch command 141 which comprises the conditions for the UE to evaluate 142 in respect of the indicated target cell(s). It should be noted that the resource allocation is exchanged between the serving cell and the target cells before the source cell sends the LTM cell switch command 141 to the UE. In other words, the communications device may be configured to transmit, to the source infrastructure equipment before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and to receive, from the source infrastructure equipment after transmitting the measurement report and before receiving the one or more conditional LTM handover commands, an allocation of radio resources for each of the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands (i.e. for the communications device to transmit an initial signal upon performing the handover procedure).

[0123] In some arrangements of embodiments of the present technique, as shown in Figure 12, rather than the resources being allocated between steps 5 and 6 (of the existing LTM procedure as shown in Figure 9) as defined by the arrangements described in the paragraph above, the resources that are allocated in step 2 (of the existing LTM procedure as shown in Figure 9) are de-allocated 143 (i.e., released) between steps 5 and 6 for the target cells that are not included in the LTM cell switch command 141. In other words, the communications device may be configured to receive from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, a radio resource control, RRC, configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment (i.e. for the communications device to transmit an initial signal upon performing the handover procedure), the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, to transmit, to the source infrastructure equipment after receiving the RRC configuration message and before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and to receive, from the source infrastructure equipment after transmitting the measurement report and before receiving the one or more conditional LTM handover commands (or to receive within one or more of the conditional LTM handover commands), an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are released.

[0124] Additionally (or separately) to indicating the released resources to the UE, the resources may also be released by the source cell in the candidate cells (which are not among the indicated target cells in the LTM command(s)) themselves. In other words, the source infrastructure may be configured to transmit, to the communications device before transmitting the one or more conditional LTM handover commands, a radio resource control, RRC, configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, to receive, from the communications device after transmitting the RRC configuration message and before transmitting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and to transmit to the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, after receiving the measurement report and before transmitting the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are released.

[0125] In some arrangements of embodiments of the present technique, when the target cell allocates the resources, a timer is used to indicate how long the resources will be kept, and if this timer expires the target cell releases the resources. This therefore reduces the amount of resource wastage, but does provide a limit to the time during which a UE may evaluate the handover conditions and execute the handover command when such conditions are met. In other words, the communications device may be configured to receive, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and to determine that the radio resources allocated by the RRC configuration message will be released after a predefined period of time (i.e. as configured by the timer). Here, the predefined period of time (configured by the timer) may start upon receipt by the communications device (or on transmission by the source infrastructure equipment) of at least one of the conditional LTM handover commands.

[0126] Here, the timer value may be included in the LTM cell switch command (i.e. associated with the resources for the target cell indicated in that LTM cell switch command) so that the UE is aware the deadline after which the resources for that target cell will be release. Alternatively, the timer may be configured by an RRC message (i.e. received from the source cell), but started at the UE when it receives the LTM cell switch command. Alternatively, the timer may be configured by either an RRC message or in the LTM switch command, but may start upon receipt by the UE of a physical layer signalling message (e.g. a DCI) from the source cell.

[0127] Multiple timers may be configured, each associated with one of the target cells / target infrastructure equipment. Where multiple timers are configured, these timers may have different lengths / periods from one another, which may for example be based on a priority or current or expected traffic load or some other parameter of the particular target cell for which the timer is configured.

[0128] In some arrangements of embodiments of the present technique, as shown in Figure 12, rather than resources being allocated or released between steps 5 and 6 (of the existing LTM procedure as shown in Figure 9) as defined by the arrangements described in the paragraphs above, when the target cell allocates the resources in step 2 (of the existing LTM procedure as shown in Figure 9), the resources are deactivated by default, and then the resources are activated 143 just before the network sends the LTM cell switch command 141 for a particular target cell. It should be noted here that the activation is exchanged between the serving cell and the target cells before the source cell sends the LTM cell switch command 141 to the UE. In other words, the communications device may be configured to receive, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment (i.e. for the communications device to transmit an initial signal upon performing the handover procedure), the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the allocated radio resources are deactivated, to transmit, to the source infrastructure equipment after receiving the RRC configuration message and before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and to receive, from the source infrastructure equipment after transmitting the measurement report and before receiving the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are activated. Here, the (allocated but deactivated) resources for target cells that are not included in the LTM cell switch command 141 and thus are not activated 143 may be explicitly deallocated or released 143 at (or close to) the time at which the resources for target cells that are included in the LTM cell switch command 141 are activated 143. Here, the indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are activated may be received within the conditional LTM handover command(s) rather than being a separate indication. In other words, the communications device may be configured to receive, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the allocated radio resources are deactivated, to transmit, to the source infrastructure equipment after receiving the RRC configuration message and before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, wherein the one or more conditional LTM handover commands each comprise an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by that conditional LTM handover command are activated. This indication included within the conditional LTM handover command(s) that the resources for the target infrastructure equipment are activated may be an explicit indication that such resources are activated. Alternatively, the activation may be implicit, and the UE can assume that the resources are automatically activated based on the cell IDs of the target cells (for which those resources were allocated in the RRC configuration message) are included in the LTM cell command.

[0129] Here, such an indication may have a setup-release structure. That is, as noted above, the target cell allocates the resources in step 2 (of the existing LTM procedure as shown in Figure 9), and these resources are de-activated by default. For example, resources may be allocated for a configuration of five candidate cells, each of which is associated with an index indicated by the RRC configuration message of step 2. After this, the conditional LTM handover command(s) may indicate the indices of the target cells / resources that are being activated - e.g., it may indicate an index of three of the candidate cells which the UE then understands to be the target cells for the LTM which it needs to evaluate the conditions for. Here, for the other non-indicated indices (e.g. the other two candidate cells in this example), the resources allocated in the RRC configuration message may be either implicitly released, or the conditional LTM handover command (or some other downlink message) may explicitly indicate that these resources are released.

[0130] Currently in Rel-18, the maximum number of target cells that can be configured for LTM is eight, whilst the maximum number of indicated target cells in the LTM command is one. This therefore means that there is only one cell that can be indicated for handover at a given time. As described above, the UE may receive a conditional LTM command indicating multiple target cells, or may receive multiple conditional LTM commands each indicating one or more target cells. As such, having the maximum number of indicated target cells in the LTM command being one is relatively inflexible and provides the UE with only one possible target cell when in reality there may be multiple target cells for which it is likely the conditions for LTM handover may be met, where indicating multiple target cells in the LTM command may increase the chances of the UE determining that the condition(s) for one of the target cells are met and thus performing the LTM handover at an earlier time and thus more efficiently (as the UEs communication session can be continued and resources for other cells that are not required can be released or deallocated earlier). In some arrangements of embodiments of the present technique, the maximum number of indicated target cells in the LTM command(s) to evaluate the conditions can be set to be greater than one (e.g. two, three, four, five, etc.), to provide such flexibility to the UE in determining conditions for multiple potential target UEs, but less than the maximum number of target cells (eight) that can be configured for LTM to reduce the amount of measurement and evaluation that the UE is required to perform and to reduce the amount of resources that need to be allocated or activated or otherwise held for potential use by the UE in respect of the LTM handover. In other words, the communications device may be configured to receive, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an indication of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein a maximum number of target infrastructure equipment that can be indicated by the one or more conditional LTM handover commands is less than a maximum number of candidate infrastructure equipment that can be indicated by the RRC configuration message.

[0131] In some arrangements of embodiments of the present technique, in order to reduce the complexity at the UE for managing the candidate cells, the candidate cells can be significantly reduced if the DL and UL synchronisation is performed (currently performed in steps 4a and 4b of the existing LTM procedure as shown in Eigure 9) after the UE transmits the LI measurement report (in step 5 of the existing LTM procedure as shown in Figure 9). This is because the LI measurement report exhibits the most credible target cells for handover compared to the L3 measurement performed in step 1 of the existing LTM procedure as shown in Figure 9.

[0132] Therefore, in such arrangements of embodiments of the present technique, as shown in the example flow diagram of Figure 13, the downlink synchronisation 144 and uplink synchronisation 145 with the candidate target cells (currently performed in steps 4a and 4b of the existing LTM procedure as shown in Figure 9) should be carried out by the after step 5; i.e. after transmitting the LI measurement report but before receiving the LTM cell switch command 141. In other words, the communications device may be configured to transmit, to the source infrastructure equipment before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and to perform, based on a command received from the source infrastructure equipment after transmitting the measurement report, synchronisation in the downlink and / or the uplink with one or more of the candidate infrastructure equipment. However, those skilled in the art would appreciate that such arrangements of embodiments of the present technique do not mean that the L3 measurement is not needed.

[0133] Those skilled in the art would appreciate that the method flow diagrams shown by Figures 11, 12, and 13, as well as the part schematic, part message flow diagram of Figure 10, may be adapted in accordance with embodiments of the present technique. For example, other intermediate steps may be included in such methods, or the steps may be performed in any logical order. Though embodiments of the present technique have been described largely by way of the example communications system shown in Figure 10, it would be clear to those skilled in the art that they could be equally applied to other systems to those described herein.

[0134] 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.

[0135] The following numbered paragraphs provide further example aspects and features of the present technique:

[0136] Paragraph 1. A method of operating a communications device, the method comprising receiving, from a source infrastructure equipment with which the communications device is connected, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the source infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device.

[0137] Paragraph 2. A method according to Paragraph 1, comprising determining that the one or more conditions indicated by one of the received conditional LTM handover commands are satisfied, and performing the LTM handover procedure to hand over from the source infrastructure equipment to the target infrastructure equipment indicated by the received conditional LTM handover command for which the communications device determines that one or more conditions are satisfied.

[0138] Paragraph 3. A method according to Paragraph 1 or Paragraph 2, wherein the one or more conditions comprise a quality of physical layer signals received from the target infrastructure equipment being greater than a quality of physical layer signals received from the source infrastructure equipment by at least a predefined amount.

[0139] Paragraph 4. A method according to any of Paragraphs 1 to 3, wherein the one or more conditions comprise a quality of physical layer signals received from the target infrastructure equipment being greater than a predefined threshold.

[0140] Paragraph 5. A method according to any of Paragraphs 1 to 4, wherein the one or more conditions comprise a quality of physical layer signals received from the source infrastructure equipment being less than a predefined threshold and a quality of physical layer signals received from the target infrastructure equipment being greater than the predefined threshold.

[0141] Paragraph 6. A method according to any of Paragraphs 1 to 5, comprising receiving, from the source infrastructure equipment, a MAC control element, CE, wherein the MAC CE comprises all of the one or more conditional LTM handover commands.

[0142] Paragraph 7. A method according to any of Paragraphs 1 to 6, comprising receiving, from the source infrastructure equipment, one or more MAC CEs, wherein each of the MAC CEs comprises one of the one or more conditional LTM handover commands.

[0143] Paragraph 8. A method according to any of Paragraphs 1 to 7, comprising transmitting, to the source infrastructure equipment before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and receiving, from the source infrastructure equipment after transmitting the measurement report and before receiving the one or more conditional LTM handover commands, an allocation of radio resources for each of the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands. Paragraph 9. A method according to any of Paragraphs 1 to 8, comprising receiving, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, a radio resource control, RRC, configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, transmitting, to the source infrastructure equipment after receiving the RRC configuration message and before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and receiving, from the source infrastructure equipment after transmitting the measurement report and before receiving the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are released.

[0144] Paragraph 10. A method according to any of Paragraphs 1 to 9, comprising receiving, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, determining that the radio resources allocated by the RRC configuration message will be released after a predefined period of time.

[0145] Paragraph 11. A method according to Paragraph 10, wherein the predefined period of time starts upon receipt by the communications device of at least one of the conditional LTM handover commands.

[0146] Paragraph 12. A method according to Paragraph 10 or Paragraph 11, wherein the predefined period of time starts upon receipt by the communications device of a physical layer signalling message from the source infrastructure equipment.

[0147] Paragraph 13. A method according to any of Paragraphs 10 to 12, wherein the predefined period of time is indicated in at least one of the conditional LTM handover commands.

[0148] Paragraph 14. A method according to any of Paragraphs 10 to 13, comprising receiving, from the source infrastructure equipment, an RRC message comprising an indication of the predefined period of time.

[0149] Paragraph 15. A method according to any of Paragraphs 1 to 14, comprising receiving, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the allocated radio resources are deactivated, transmitting, to the source infrastructure equipment after receiving the RRC configuration message and before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and receiving, from the source infrastructure equipment after transmitting the measurement report and before receiving the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are activated.

[0150] Paragraph 16. A method according to any of Paragraphs 1 to 15, comprising receiving, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the allocated radio resources are deactivated, transmitting, to the source infrastructure equipment after receiving the RRC configuration message and before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, wherein the one or more conditional LTM handover commands each comprise an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by that conditional LTM handover command are activated.

[0151] Paragraph 17. A method according to any of Paragraphs 1 to 16, comprising receiving, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an indication of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein a maximum number of target infrastructure equipment that can be indicated by the one or more conditional LTM handover commands is less than a maximum number of candidate infrastructure equipment that can be indicated by the RRC configuration message.

[0152] Paragraph 18. A method according to any of Paragraphs 1 to 17, comprising transmitting, to the source infrastructure equipment before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and performing, based on a command received from the source infrastructure equipment after transmitting the measurement report, synchronisation in the downlink and / or the uplink with one or more of the candidate infrastructure equipment.

[0153] Paragraph 19. A communications device comprising transceiver circuitry configured to transmit signals to and / or to receive signals, and controller circuitry configured in combination with the transceiver circuitry to receive, from a source infrastructure equipment with which the communications device is connected, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the source infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device.

[0154] Paragraph 20. Circuitry for a communications device, the circuitry comprising transceiver circuitry configured to transmit signals to and / or to receive signals, and controller circuitry configured in combination with the transceiver circuitry to receive, from a source infrastructure equipment with which the communications device is connected, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the source infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device.

[0155] Paragraph 21. A method of operating am infrastructure equipment of a wireless communications network, the infrastructure equipment being a source infrastructure equipment with which a communications device is connected, the method comprising transmitting, to the communications device, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device.

[0156] Paragraph 22. A method according to Paragraph 21, wherein the one or more conditions comprise a quality of physical layer signals received at the communications device from the target infrastructure equipment being greater than a quality of physical layer signals transmitted to the communications device by the infrastructure equipment by at least a predefined amount.

[0157] Paragraph 23. A method according to Paragraph 21 or Paragraph 22, wherein the one or more conditions comprise a quality of physical layer signals received at the communications device from the target infrastructure equipment being greater than a predefined threshold.

[0158] Paragraph 24. A method according to any of Paragraphs 21 to 23, wherein the one or more conditions comprise a quality of physical layer signals transmitted to the communications device by the infrastructure equipment being less than a predefined threshold and a quality of physical layer signals received at the communications device from the target infrastructure equipment being greater than the predefined threshold.

[0159] Paragraph 25. A method according to any of Paragraphs 21 to 24, comprising transmitting, to the communications device, a medium access control, MAC, control element, CE, wherein the MAC CE comprises all of the one or more conditional LTM handover commands.

[0160] Paragraph 26. A method according to any of Paragraphs 21 to 25, comprising transmitting, to the communications device, one or more MAC CEs, wherein each of the MAC CEs comprises one of the one or more conditional LTM handover commands.

[0161] Paragraph 27. A method according to any of Paragraphs 21 to 26, comprising receiving, from the communications device before transmitting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and transmitting, to the communications device after receiving the measurement report and before transmitting the one or more conditional LTM handover commands, an allocation of radio resources for each of the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands.

[0162] Paragraph 28. A method according to any of Paragraphs 21 to 27, comprising transmitting, to the communications device before transmitting the one or more conditional LTM handover commands, a radio resource control, RRC, configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, receiving, from the communications device after transmitting the RRC configuration message and before transmitting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and transmitting, to the communications device after receiving the measurement report and before transmitting the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are released.

[0163] Paragraph 29. A method according to any of Paragraphs 21 to 28, comprising transmitting, to the communications device before transmitting the one or more conditional LTM handover commands, a radio resource control, RRC, configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, receiving, from the communications device after transmitting the RRC configuration message and before transmitting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and transmitting to the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, after receiving the measurement report and before transmitting the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are released. Paragraph 30. A method according to any of Paragraphs 21 to 29, comprising transmitting, to the communications device before transmitting the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the radio resources allocated by the RRC configuration message will be released after a predefined period of time.

[0164] Paragraph 31. A method according to Paragraph 30, wherein the predefined period of time starts upon receipt by the communications device of at least one of the conditional LTM handover commands. Paragraph 32. A method according to Paragraph 30 or Paragraph 31, wherein the predefined period of time starts upon receipt by the communications device of a physical layer signalling message from the infrastructure equipment.

[0165] Paragraph 33. A method according to any of Paragraphs 30 to 32, wherein the predefined period of time is indicated in at least one of the conditional LTM handover commands.

[0166] Paragraph 34. A method according to any of Paragraphs 30 to 33, comprising transmiting, to the communications device, an RRC message comprising an indication of the predefined period of time.

[0167] Paragraph 35. A method according to any of Paragraphs 21 to 34, comprising transmiting, to the communications device before transmiting the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the allocated radio resources are deactivated, receiving, from the communications device after transmiting the RRC configuration message and before transmiting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and transmiting, to the communications device after receiving the measurement report and before transmiting the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are activated.

[0168] Paragraph 36. A method according to any of Paragraphs 21 to 35, comprising transmiting, to the communications device before transmiting the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the allocated radio resources are deactivated, receiving, from the communications device after transmiting the RRC configuration message and before transmiting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, wherein the one or more conditional LTM handover commands each comprise an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by that conditional LTM handover command are activated.

[0169] Paragraph 37. A method according to any of Paragraphs 21 to 36, comprising transmiting, to the communications device before transmiting the one or more conditional LTM handover commands, an RRC configuration message comprising an indication of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein a maximum number of target infrastructure equipment that can be indicated by the one or more conditional LTM handover commands is less than a maximum number of candidate infrastructure equipment that can be indicated by the RRC configuration message.

[0170] Paragraph 38. A method according to any of Paragraphs 21 to 37, comprising receiving, from the communications device before transmiting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and transmiting, to the communications device after receiving the measurement report, a command to perform synchronisation in the downlink and / or the uplink with one or more of the candidate infrastructure equipment. Paragraph 39. An infrastructure equipment of a wireless communications network, the infrastructure equipment being a source infrastructure equipment with which a communications device is connected, the infrastructure equipment comprising transceiver circuitry configured to transmit signals to and / or to receive signals, and controller circuitry configured in combination with the transceiver circuitry to transmit, to the communications device, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device.

[0171] Paragraph 40. Circuitry for an infrastructure equipment of a wireless communications network, the infrastructure equipment being a source infrastructure equipment with which a communications device is connected, the circuitry comprising transceiver circuitry configured to transmit signals to and / or to receive signals, and controller circuitry configured in combination with the transceiver circuitry to transmit, to the communications device, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device.

[0172] Paragraph 41. A wireless communications system comprising a communications device according to Paragraph 19, and a source infrastructure equipment according to Paragraph 39.

[0173] Paragraph 42. A computer program comprising instructions which, when loaded onto a computer, cause the computer to perform a method according to any of Paragraphs 1 to 18 or Paragraphs 21 to 38.

[0174] Paragraph 43. A non-transitory computer-readable storage medium storing a computer program according to Paragraph 42.

[0175] It will be appreciated that the above description for clarity has described embodiments with reference to different functional units, circuitry and / or processors. However, it will be apparent that any suitable distribution of functionality between different functional units, circuitry and / or processors may be used without detracting from the embodiments.

[0176] Described embodiments may be implemented in any suitable form including hardware, software, firmware or any combination of these. Described embodiments may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. The elements and components of any embodiment may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the disclosed embodiments may be implemented in a single unit or may be physically and functionally distributed between different units, circuitry and / or processors. 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.

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[0184] [7] TS 23.501, “3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; System architecture for the 5G System (5GS); Stage 2 (Release 18)”, 3GPP, VI 8.2.0, June 2023.

[0185] [8] TS 36.300, “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (Release 17)”, 3GPP, V17.4.0, March 2023.

[0186] [9] RP -234036 , “New WID: NR mobility enhancements Phase 4,” Intel, 3GPP TSG RAN Meeting #102, December 2023.

Claims

CLAIMSWhat is claimed is:

1. A method of operating a communications device, the method comprising receiving, from a source infrastructure equipment with which the communications device is connected, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the source infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device.

2. A method according to Claim 1, comprising determining that the one or more conditions indicated by one of the received conditional LTM handover commands are satisfied, and performing the LTM handover procedure to hand over from the source infrastructure equipment to the target infrastructure equipment indicated by the received conditional LTM handover command for which the communications device determines that one or more conditions are satisfied.

3. A method according to Claim 1, wherein the one or more conditions comprise a quality of physical layer signals received from the target infrastructure equipment being greater than a quality of physical layer signals received from the source infrastructure equipment by at least a predefined amount.

4. A method according to Claim 1, wherein the one or more conditions comprise a quality of physical layer signals received from the target infrastructure equipment being greater than a predefined threshold.

5. A method according to Claim 1, wherein the one or more conditions comprise a quality of physical layer signals received from the source infrastructure equipment being less than a predefined threshold and a quality of physical layer signals received from the target infrastructure equipment being greater than the predefined threshold.

6. A method according to Claim 1, comprising receiving, from the source infrastructure equipment, a MAC control element, CE, wherein the MAC CE comprises all of the one or more conditional LTM handover commands.

7. A method according to Claim 1, comprising receiving, from the source infrastructure equipment, one or more MAC CEs, wherein each of the MAC CEs comprises one of the one or more conditional LTM handover commands.

8. A method according to Claim 1, comprising transmitting, to the source infrastructure equipment before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the atleast one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and receiving, from the source infrastructure equipment after transmitting the measurement report and before receiving the one or more conditional LTM handover commands, an allocation of radio resources for each of the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands.

9. A method according to Claim 1, comprising receiving, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, a radio resource control, RRC, configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, transmitting, to the source infrastructure equipment after receiving the RRC configuration message and before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and receiving, from the source infrastructure equipment after transmitting the measurement report and before receiving the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are released.

10. A method according to Claim 1, comprising receiving, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, determining that the radio resources allocated by the RRC configuration message will be released after a predefined period of time.

11. A method according to Claim 10, wherein the predefined period of time starts upon receipt by the communications device of at least one of the conditional LTM handover commands.

12. A method according to Claim 10, wherein the predefined period of time starts upon receipt by the communications device of a physical layer signalling message from the source infrastructure equipment.

13. A method according to Claim 10, wherein the predefined period of time is indicated in at least one of the conditional LTM handover commands.

14. A method according to Claim 10, comprising receiving, from the source infrastructure equipment, an RRC message comprising an indication of the predefined period of time.

15. A method according to Claim 1, comprising receiving, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructureequipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the allocated radio resources are deactivated, transmitting, to the source infrastructure equipment after receiving the RRC configuration message and before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and receiving, from the source infrastructure equipment after transmitting the measurement report and before receiving the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are activated.

16. A method according to Claim 1, comprising receiving, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the allocated radio resources are deactivated, transmitting, to the source infrastructure equipment after receiving the RRC configuration message and before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, wherein the one or more conditional LTM handover commands each comprise an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by that conditional LTM handover command are activated.

17. A method according to Claim 1, comprising receiving, from the source infrastructure equipment before receiving the one or more conditional LTM handover commands, an RRC configuration message comprising an indication of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein a maximum number of target infrastructure equipment that can be indicated by the one or more conditional LTM handover commands is less than a maximum number of candidate infrastructure equipment that can be indicated by the RRC configuration message.

18. A method according to Claim 1, comprising transmitting, to the source infrastructure equipment before receiving the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and performing, based on a command received from the source infrastructure equipment after transmitting the measurement report, synchronisation in the downlink and / or the uplink with one or more of the candidate infrastructure equipment.

19. A communications device comprisingtransceiver circuitry configured to transmit signals to and / or to receive signals, and controller circuitry configured in combination with the transceiver circuitry to receive, from a source infrastructure equipment with which the communications device is connected, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the source infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device.

20. Circuitry for a communications device, the circuitry comprising transceiver circuitry configured to transmit signals to and / or to receive signals, and controller circuitry configured in combination with the transceiver circuitry to receive, from a source infrastructure equipment with which the communications device is connected, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the source infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the source infrastructure equipment, the target infrastructure equipment, and the communications device.

21. A method of operating am infrastructure equipment of a wireless communications network, the infrastructure equipment being a source infrastructure equipment with which a communications device is connected, the method comprising transmitting, to the communications device, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device.

22. A method according to Claim 21, wherein the one or more conditions comprise a quality of physical layer signals received at the communications device from the target infrastructure equipment being greater than a quality of physical layer signals transmitted to the communications device by the infrastructure equipment by at least a predefined amount.

23. A method according to Claim 21, wherein the one or more conditions comprise a quality of physical layer signals received at the communications device from the target infrastructure equipment being greater than a predefined threshold.

24. A method according to Claim 21, wherein the one or more conditions comprise a quality of physical layer signals transmitted to the communications device by the infrastructure equipment being less than a predefined threshold and a quality of physical layer signals received at the communications device from the target infrastructure equipment being greater than the predefined threshold.

25. A method according to Claim 21 , comprising transmitting, to the communications device, a medium access control, MAC, control element, CE, wherein the MAC CE comprises all of the one or more conditional LTM handover commands.

26. A method according to Claim 21, comprising transmitting, to the communications device, one or more MAC CEs, wherein each of the MAC CEs comprises one of the one or more conditional LTM handover commands.

27. A method according to Claim 21, comprising receiving, from the communications device before transmitting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and transmitting, to the communications device after receiving the measurement report and before transmitting the one or more conditional LTM handover commands, an allocation of radio resources for each of the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands.

28. A method according to Claim 21, comprising transmitting, to the communications device before transmitting the one or more conditional LTM handover commands, a radio resource control, RRC, configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, receiving, from the communications device after transmitting the RRC configuration message and before transmitting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and transmitting, to the communications device after receiving the measurement report and before transmitting the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are released.

29. A method according to Claim 21, comprising transmitting, to the communications device before transmitting the one or more conditional LTM handover commands, a radio resource control, RRC, configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, receiving, from the communications device after transmitting the RRC configuration message and before transmitting the one or more conditional LTM handover commands, a measurement reportcomprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and transmitting to the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, after receiving the measurement report and before transmitting the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are not among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are released.

30. A method according to Claim 21, comprising transmitting, to the communications device before transmitting the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the radio resources allocated by the RRC configuration message will be released after a predefined period of time.

31. A method according to Claim 30, wherein the predefined period of time starts upon receipt by the communications device of at least one of the conditional LTM handover commands.

32. A method according to Claim 30, wherein the predefined period of time starts upon receipt by the communications device of a physical layer signalling message from the infrastructure equipment.

33. A method according to Claim 30, wherein the predefined period of time is indicated in at least one of the conditional LTM handover commands.

34. A method according to Claim 30, comprising transmitting, to the communications device, an RRC message comprising an indication of the predefined period of time.

35. A method according to Claim 21 , comprising transmitting, to the communications device before transmitting the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the allocated radio resources are deactivated, receiving, from the communications device after transmitting the RRC configuration message and before transmitting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, and transmitting, to the communications device after receiving the measurement report and before transmitting the one or more conditional LTM handover commands, an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands are activated.

36. A method according to Claim 21, comprisingtransmiting, to the communications device before transmiting the one or more conditional LTM handover commands, an RRC configuration message comprising an allocation of radio resources for each of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein the allocated radio resources are deactivated, receiving, from the communications device after transmiting the RRC configuration message and before transmiting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from the one or more candidate infrastructure equipment, wherein the one or more conditional LTM handover commands each comprise an indication that the radio resources allocated by the RRC configuration message for the candidate infrastructure equipment which are among the at least one target infrastructure equipment indicated by that conditional LTM handover command are activated.

37. A method according to Claim 21, comprising transmiting, to the communications device before transmiting the one or more conditional LTM handover commands, an RRC configuration message comprising an indication of one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, wherein a maximum number of target infrastructure equipment that can be indicated by the one or more conditional LTM handover commands is less than a maximum number of candidate infrastructure equipment that can be indicated by the RRC configuration message.

38. A method according to Claim 21, comprising receiving, from the communications device before transmiting the one or more conditional LTM handover commands, a measurement report comprising an indication of measurements performed by the communications device on physical layer signals received from one or more candidate infrastructure equipment, the one or more candidate infrastructure equipment being candidates for the at least one target infrastructure equipment indicated by each of the one or more conditional LTM handover commands, and transmiting, to the communications device after receiving the measurement report, a command to perform synchronisation in the downlink and / or the uplink with one or more of the candidate infrastructure equipment.

39. An infrastructure equipment of a wireless communications network, the infrastructure equipment being a source infrastructure equipment with which a communications device is connected, the infrastructure equipment comprising transceiver circuitry configured to transmit signals to and / or to receive signals, and controller circuitry configured in combination with the transceiver circuitry to transmit, to the communications device, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device.

40. Circuitry for an infrastructure equipment of a wireless communications network, the infrastructure equipment being a source infrastructure equipment with which a communications device is connected, the circuitry comprising transceiver circuitry configured to transmit signals to and / or to receive signals, and controller circuitry configured in combination with the transceiver circuitry to transmit, to the communications device, one or more conditional lower-layer triggered mobility, LTM, handover commands, wherein each conditional LTM handover command comprises an indication of at least one target infrastructure equipment and an indication of one or more conditions that, if met, the communications device is to perform an LTM handover procedure to hand over from the infrastructure equipment to the target infrastructure equipment, wherein the LTM handover procedure consists of signalling only at a physical layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device and / or a medium access control, MAC, layer at each of the infrastructure equipment, the target infrastructure equipment, and the communications device.

41. A wireless communications system comprising a communications device according to Claim 19, and a source infrastructure equipment according to Claim 39.

42. A computer program comprising instructions which, when loaded onto a computer, cause the computer to perform a method according to Claim 1 or Claim 21.

43. A non-transitory computer-readable storage medium storing a computer program according to Claim 42.

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