Methods, communications devices, and non-terrestrial infrastructure equipment

Abstract

A communications device configures its transceiver circuitry to transmit uplink signals to and / or to receive downlink signals from one or more non-terrestrial network infrastructure equipment forming part of a non-terrestrial network (NTN) and to transmit uplink signal to and / or to receive uplink signals from one or more terrestrial network infrastructure equipment forming part of a terrestrial network (TN). The configuring includes establishing a dual connectivity mode in which the one or more TN infrastructure equipment is a master network and the one or more NTN infrastructure equipment is a secondary network. The communications device transmits data to or receives data from the TN infrastructure equipment via a first wireless access interface provided by the TN as a master network using the configured transceiver circuitry and de-activates the transceiver circuitry configured for transmitting and receiving data via a second wireless access interface provided by the NTN as a secondary network. The communications device detects a likely loss or reduction of a radio coverage of the first wireless access interface provided by the TN, determines a timing required for synchronisation with the NTN, and activates the transceiver circuitry to transmit and to receive data via the second wireless access interface provided by the NTN using the indication of the timing received from the TN for synchronisation with the NTN. By detecting that there is likely to be a loss or reduction of a radio coverage of a wireless access interface provided by the TN, and determining the timing required for synchronisation with the NTN, the communications device can transmit or receive user data with a reduced likelihood of an interruption of communication of the user data when the UE required to transmit and to receive via a wireless access interface provided by the NTN rather than the TN.

Description

[0001] METHODS, COMMUNICATIONS DEVICES, AND NON-TERRESTRIAL INFRASTRUCTURE EQUIPMENT

[0002] BACKGROUND

[0003] Field of Disclosure

[0004] The present disclosure relates generally to Non-Terrestrial Networks, NTNs, and specifically to methods of operating communications devices capable of a dual connection to an NTN and a terrestrial network, TN.

[0005] The present application claims Paris Convention priority from European patent application number EP24192926.4, filed on 5 August 2024, the contents of which are hereby incorporated by reference in their entirety.

[0006] Description of Related Art

[0007] The “background” description provided 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 the 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 disclosure.

[0008] Current and future wireless communications networks are expected routinely and efficiently to support communications with an ever-increasing range of devices associated with a wider range of data traffic profiles and types. For example, wireless communications networks will be expected efficiently to support communications with devices including reduced complexity devices, machine type communication (MTC) devices, high resolution video displays, virtual reality headsets, 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, devices 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 devices 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 considerations 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).

[0009] 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, efficiently to support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles and requirements.

[0010] One example area of current interest in this regard includes so-called “non-terrestrial networks”, or NTN for short. 3GPP has proposed in Release 15 of the 3GPP specifications to develop technologies for providing coverage by means of one or more antennas mounted on airborne or space-borne vehicles [1].

[0011] Non-terrestrial networks may provide service in areas that cannot be covered by terrestrial cellular networks (i.e. those where coverage is provided by means of land-based antennas), such as isolated or remote areas, on board aircraft or vessels) or may provide enhanced service in other areas. The expanded coverage that may be achieved by means of non-terrestrial networks may provide service continuity for machine-to-machine (M2M) or ‘internet of things’ (loT) devices, or for passengers on board moving platforms (e.g. passenger vehicles such as aircraft, ships, high speed trains, or buses). Other benefits may arise from the use of non-terrestrial networks for providing multicast / broadcast resources for data delivery.

[0012] The use of different types of network infrastructure equipment and requirements for coverage enhancement give rise to new challenges for efficiently handling communications in wireless communications systems that need to be addressed.

[0013] SUMMARY OF THE DISCLOSURE

[0014] The present disclosure can help address or mitigate at least some of the issues discussed above.

[0015] Some embodiments of the present technique can provide a method for operating a communications device. The method comprises configuring transceiver circuitry of the communications device for transmitting uplink signals to and / or receiving downlink signals from one or more non-terrestrial network infrastructure equipment forming part of a non-terrestrial network (NTN) and for transmitting uplink signal to and / or for receiving uplink signals from one or more terrestrial network infrastructure equipment forming part of a terrestrial network (TN). The configuring includes establishing a dual connectivity mode in which the one or more TN infrastructure equipment is a master network and the one or more NTN infrastructure equipment is a secondary network. The method comprises transmitting data to or receiving data from the TN infrastructure equipment via a first wireless access interface provided by the TN as a master network using the configured transceiver circuitry and de-activating the transceiver circuitry configured for transmitting and receiving data via a second wireless access interface provided by the NTN as a secondary network. Here the “de-activating” can mean that the transceiver circuitry is not configured to transmit and / or to receive via the NTN or that the transceiver circuitry is configured to transmit and / or to receive via the NTN and powered down so that some circuits such as the radio frequency (RF) transmit and / or receive components or other signal processing components are set into a low power state, that is de-activated. The method comprises detecting a likely loss or reduction of a radio coverage of the first wireless access interface provided by the TN, determining a timing required for synchronisation with the NTN, activating the transceiver circuitry to transmit and to receive data via the second wireless access interface provided by the NTN using the indication of the timing received from the TN for synchronisation with the NTN.

[0016] By detecting that there is likely to be a loss or reduction of a radio coverage of a wireless access interface provided by the TN, and determining the timing required for synchronisation with the NTN, the communications device can transmit or receive user data with a reduced likelihood of an interruption of communication of the user data when the UE required to transmit and to receive via a wireless access interface provided by the NTN rather than the TN. In one example, the communications device transmits an indication that there is likely to be a reduction or loss of radio coverage by the TN and in response TN can transmit a time required for synchronisation with the NTN before radio coverage with the TN lost. Furthermore, in some examples the TN can configure the NTN to provide an indication of communications resources for performing a RACH procedure with the NTN and / or synchronisation information so that the communications device can transmit or receive via the NTN when coverage from the TN is lost.

[0017] Respective aspects and features of the present disclosure are defined in the appended claims. 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.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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:

[0020] Figure 1 schematically represents some aspects of a wireless communications system, such as an LTE- type wireless communication system which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0021] Figure 2 schematically represents some aspects of a new radio or 5G radio access technology (RAT) wireless communications system which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0022] Figure 3 is a schematic block diagram illustrating parts of the wireless communications network shown in Figure 2 in more detail, including a communications device (UE) and an infrastructure equipment (gNB); Figure 4 is an illustrative representation a non-terrestrial network (NTN) including a satellite / aerial forming an infrastructure equipment of the NTN which provides a plurality of spot beams forming cells within which a communications device (UE) can transmit and receive signals;

[0023] Figure 5 is an illustrative representation of an example of a wireless communications system comprising an NTN part and a terrestrial network (TN) part which may be configured to operate in accordance with embodiments of the present disclosure;

[0024] Figure 6 is a message sequence / flow diagram illustrating an example embodiment in which a TN acts as a master network or node and an NTN acts as a secondary network or node for a communications device operating in accordance with dual connectivity according to an example embodiment; and

[0025] Figure 7 is a message sequence / flow diagram illustrating an example embodiment in which an NTN acts as a master network or node and a TN acts as a secondary network or node for a communications device operating in accordance with dual connectivity.

[0026] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] Long Term Evolution Advanced Radio Access Technology (4G)

[0028] Figure 1 provides a schematic diagram illustrating some basic functionality of a wireless communications 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.

[0029] The network 6 includes a plurality of base stations 1 connected to a core network (CN) 2. 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.

[0030] 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. Communications devices may also be referred to as mobile stations, user equipment (UEs), user terminals, mobile radios, mobile terminals, terminal devices, wireless transmit and receive units (WTRUs), 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.

[0031] Base stations, which are an example of network infrastructure equipment, may also be referred to as transceiver stations, nodeBs, e-nodeBs, eNB, g-nodeBs, gNBs 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.

[0032] New Radio Access Technology (5G)

[0033] Systems incorporating NR technology are expected to support different services (or types of services), which may be characterised by different requirements for latency, data rate and / or reliability. For example, Enhanced Mobile Broadband (eMBB) services are characterised by high capacity with a requirement to support up to 20 Gb / s. The requirements for Ultra Reliable and Low Latency Communications (URLLC) services are for one transmission of a 32 byte packet to be transmitted from the radio protocol layer 2 / 3 SDU ingress point to the radio protocol layer 2 / 3 SDU egress point of the radio interface within 1 ms with a reliability of 1 - 10'5(99.999 %) or higher (99.9999%) [2],

[0034] Massive Machine Type Communications (mMTC) is another example of a service which may be supported by NR-based communications networks. In addition, systems may be expected to support further enhancements related to Industrial Internet of Things (IIoT) in order to support services with new requirements of high availability, high reliability, low latency, and in some cases, high-accuracy positioning.

[0035] 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) 40 by a connection interface represented as a dashed line 16. Each of the TRPs 10 is arranged to transmit and receive signals via a wireless access interface within a radio frequency bandwidth available to the wireless communications network. Thus, within a range for performing radio communications via the wireless access interface, each of the TRPs 10, forms a cell of the wireless communications network as represented by a circle 12. As such, wireless communications devices 14, which are within a radio communications range provided by the cells 12, can transmit and receive signals to and from the TRPs 10 via the wireless access interface. Each of the distributed units 40 are connected to a central unit (CU) 44 (which may be referred to as a controlling node) via an interface 46. The central unit 44 is then connected to the core network 20 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 an application function (AF) 25.

[0036] 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.

[0037] The TRPs 10, the DU 40 and CU 44 of Figure 2 may in part have a corresponding functionality to a base station or eNodeB of an UTE 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.

[0038] 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 44 and their associated distributed units 40 / 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 a communication cell 12. This communications device 14 may thus exchange signalling with the central unit 40 via one of the distributed units / TRPs 10 associated with the communication cell 12.

[0039] 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.

[0040] 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 Figs. 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 CU 44, distributed unit 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.

[0041] 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 circuitry 70, a receiver circuitry 72 and a controller or controlling processor 74 which is configured to control the transmitter circuitry 70 and the receiver circuitry 72 to transmit and receive radio signals to one or more UEs 14 within a cell 12 formed by the TRP 10. The transmitter circuitry 70 and the receiver circuitry 72 may be collectively referred to as transceiver circuitry. As shown in Figure 3, an example UE 14 is shown to include a corresponding wireless transmitter circuitry 76, receiver circuitry 78 and controller circuitry or controlling processor 80 which is configured to control the transmitter circuitry 76 and the receiver circuitry 78 to transmit and receive radio signals to the TRP 10. Signals transmitted from the transmitter circuitry 76 to the receiver circuitry 72 may represent uplink data. Signals transmitted from the transmitter circuitry 70 to the receiver circuitry 78 may represent downlink data. These signals are transmitted via the wireless access interface 84 of the TRP 10 referred to as a Uu interface.

[0042] The transmitters 70, 76 and the receivers 72, 78 (as well as other transmitters, receivers and transceivers described in relation to examples and embodiments of the present disclosure) may include radio frequency filters and amplifiers as well as signal processing components and devices in order to transmit and receive radio signals in accordance for example with the 5G / NR standard(s). The controllers 74, 80 (as well as other controllers described in relation to examples and embodiments of the present disclosure) may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc., configured to carry out instructions which are stored on a computer readable medium, such as a non-volatile memory. The processing steps described herein may be carried out by, for example, a microprocessor in conjunction with a random access memory, operating according to instructions stored on a computer readable medium. The transmitters, the receivers and the controllers are schematically shown in Figure 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 computers, 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 their operating functionality.

[0043] As shown in Figure 3, the TRP 10 also includes a communications interface, which connects to the DU 40 via a physical interface 16. The communication interface therefore provides a communication link for data and signalling traffic from the TRP 10 via the DU 40 and the CU 44 to the core network 20.

[0044] The interface 46 between the DU 40 and the CU 44 is known as the F 1 interface which can be a physical or a logical interface formed by communications circuitry forming part of the DU 40. The Fl interface 46 between CU and DU may operate in accordance with specifications 3GPP TS 38.470 and 3GPP TS 38.473, for example, 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 of the TRP 10 to the DU 40 and the Fl interface 46 from the DU 40 to the CU 44. According to the 5G architecture, functions of a gNB 100, which corresponds to the functions performed generally by base station 1 shown in Figure 1, is formed from a combination of one or more TRPs 10, a DU 40 and the CU 44, also shown in Figure 2.

[0045] Although reference has been made above to 4G / LTE and 5G NR, it will be appreciated that the present disclosure is applicable to future generations of wireless communications technology including 6G. In the case of 6G, base station, which are an example of network infrastructure equipment, may also referred to as 6G NB (6G Node B), 6G RAN node, and so forth. In 6G, the core network 20 may be one or more network functions.

[0046] Non-Terrestrial Networks (NTNs)

[0047] As a result of wide service coverage capabilities and reduced vulnerability of space / airbome vehicles to physical attacks and natural disasters, Non-Terrestrial Networks are expected to:

[0048] • foster the roll out of 5G service in un-served areas that cannot be covered by terrestrial 5G network (isolated / remote areas, on board aircrafts or vessels) and underserved areas (e.g. sub- urban / rural areas) to upgrade the performance of limited terrestrial networks in cost effective manner;

[0049] • reinforce the 5G service reliability by providing service continuity for M2M / IoT devices or for passengers on board moving platforms (e.g. passenger vehicle s-aircraft, ships, high speed trains, bus) or ensuring service availability anywhere especially for critical communications, future railway / maritime / aeronautical communications; and to

[0050] • enable 5G network scalability by providing efficient multicast / broadcast resources for data delivery towards the network edges or even user terminal.

[0051] The benefits relate to either Non-Terrestrial Networks operating alone or to integrated terrestrial and NonTerrestrial networks. NTN will impact at least coverage, user bandwidth, system capacity, service reliability or service availability, energy consumption and connection density. A role for Non-Terrestrial Network components in the 5G system is expected for at least the following verticals: transport, Public Safety, Media and Entertainment, eHealth, Energy, Agriculture, Finance and Automotive.

[0052] An NTN can provide an access networking service based on a satellite / aerial with a bent pipe payload, meaning that the same data is sent back down to Earth as is received by the satellite / aerial, with only frequency or amplification changing; i.e. acting like a pipe with a u-bend. In this example NTN, the satellite or the aerial will therefore relay a “satellite friendly” NR signal between a UE and the wireless communications network. In other examples, the satellite or aerial comprises full or part of a gNB to generate or receive a “satellite friendly” NR signal to / from the relay nodes. This requires sufficient onboard processing capabilities to be able to include a gNB or relay node functionality. Relay node (RN) related use cases will play an important role in the commercial deployment of NTN; i.e. relay nodes mounted on high speed trains, relay nodes mounted in cruise ships, relay nodes at home / office and relay nodes mounted on airliners. It should be well understood by those skilled in the art that the proposed solutions of embodiments of the present technique could be equally applied to conventional UEs and RNs.

[0053] Figure 4 schematically shows an example of a wireless communications system, which includes an NTN part. The wireless communications system comprises a core network part 20 (which may be a 4G core network or a 5G core network) in communicative connection with a radio network part. The radio network part comprises a base station 430 connected to a non-terrestrial network part 402. The nonterrestrial network (NTN) part 402 may be an example of infrastructure equipment, compromising a transceiver 404 and a controller 406 mounted on a satellite vehicle or on an airborne vehicle. The NTN part 402 may communicate with a UE 14, located within a cell 416 via a wireless access interface formed by the NTN part 402 as represented by a wireless communications link 417. For example, the cell 416 may correspond to a coverage area of a spot beam generated by the NTN part 402, which may generated other spot beams 418, 420, which form cells of the NTN. The cells formed by the spot beams 416, 418, 420 may or may not overlap. A boundary of the cell 416 may depend on an altitude of the NTN part 402 and a configuration of one or more antennas of the NTN part 402 by which the NTN part 402 transmits and receives signals on the wireless access interface.

[0054] The NTN part 402 may be a satellite in an orbit with respect to the Earth, or may be mounted on such a satellite. For example, the satellite 402 may be in a geo-stationary earth orbit (GEO) such that the NTN part 402 does not move with respect to a fixed point on the Earth’s surface. The geo-stationary earth orbit may be approximately 36,786km above the Earth’s equator. The satellite may alternatively be in a low- earth orbit (LEO), in which the NTN part 402 may complete an orbit of the Earth relatively quickly, thus providing moving cell coverage. Alternatively, the satellite may be in a non-geostationary orbit (NGSO), so that the NTN part 402 moves with respect to a fixed point on the Earth’s surface. The NTN part 402 may be an airborne vehicle such as an aircraft, or may be mounted on such a vehicle. The airborne vehicle (and hence the NTN part 402) may be stationary with respect to the surface of the Earth or may move with respect to the surface of the Earth.

[0055] In Figure 4, an earth station or base station 430 is shown as ground-based, and connected to the NTN part 402 by means of a wireless communications link 432. The earth station 430 is connected to the core network 20 via a communications link 434. The NTN part 402 receives signals representing downlink data transmitted by the base station 430 on the wireless communications link 432 and, based on the received signals, transmits signals representing the downlink data via the wireless communications link 417 providing the wireless access interface for the communications device 14. Similarly, the NTN part 402 receives signals representing uplink data transmitted by the communications device 14 via the wireless access interface comprising the wireless communications link 417 and transmits signals representing the uplink data to the base station 430 on the wireless communications link 432. The wireless communications links 417, 432 may operate at a same frequency, or may operate at different frequencies.

[0056] The extent to which the NTN part 402 processes the received signals may depend upon a processing capability of the NTN part 402. For example, the NTN part 402 may receive signals representing the downlink data on the wireless communication link 432, amplify them and (if needed) re-modulate onto an appropriate carrier frequency for onwards transmission on the wireless access interface provided by the wireless communications link 417. Alternatively, the NTN part 402 may be configured to decode the signals representing the downlink data received on the wireless communication link 432 into un-encoded downlink data, re -encode the downlink data and modulate the encoded downlink data onto the appropriate carrier frequency for onwards transmission on the wireless access interface provided by the wireless communications link 417.

[0057] The NTN part 402 may be configured to perform some of the functionality conventionally carried out by a gNB of a terrestrial network (TN). In particular, latency-sensitive functionality (such as acknowledging a receipt of the uplink data, or responding to a RACH request) may be performed by the NTN part 402 as gNB.

[0058] The earth station or base station 430 may be have components which are co-located with the NTN part 402; for example, both may be mounted on the same satellite vehicle or airborne vehicle, and there may be a physical (e.g. wired, or fibre optic) connection on board the satellite vehicle or airborne vehicle, providing the coupling between the base station 430 and the NTN part 402. In such co-located arrangements, a wireless communications feeder link between the base station 430 and a ground station (not shown) may provide connectivity between the base station 430 and the core network part 20.

[0059] It will be apparent to those skilled in the art that many scenarios can be envisaged in which the combination of the UE 14 and the NTN part 402 can provide enhanced service to end users. For example, the UE 14 may be mounted on a passenger vehicle such as a bus or train which travels through rural areas where coverage by terrestrial base stations may be limited. Terminal devices on the vehicle may obtain service via the UE 14 acting as a relay, which communicates with the NTN part 402.

[0060] There is a need to ensure that connectivity for the UE 14 with the base station 430 can be maintained, in light of the movement of the UE 14, the movement of the NTN part 402 (relative to the Earth’s surface), or both. According to conventional cellular communications techniques, a decision to change a serving cell of the UE 14 may be based on measurements of one or more characteristics of a radio frequency communications channel, such as signal strength measurements or signal quality measurements. In a terrestrial communications network, such measurements may effectively provide an indication that the UE 14 is at, or approaching, an edge of a coverage region of a cell, since, for example, path loss may broadly correlate to a distance from a base station. However, such conventional measurement-based algorithms may be unsuitable for cells generated by means of the transmission of beams from a NTN part, such as a cell generated by the NTN part 402. In particular, path loss may be primarily dependent on an altitude of the NTN part 402 and may vary only to a very limited extent (if at all) at the surface of the Earth, within the coverage region of a cell 416, 418, 420. As a result, the strength of a received signal may be always lower than that from a terrestrial base station, which thus will always be selected when available.

[0061] A further disadvantage of conventional techniques may be the relatively high rate at which cell changes occur for the UE 14 obtaining service from one or more NTN parts. For example, where the NTN part 402 is mounted on a satellite in a low-earth orbit (LEO), the NTN part 402 may complete an orbit of the Earth in around 90 minutes; the coverage of a cell generated by the NTN part 402 will move very rapidly, with respect to a fixed observation point on the surface of the Earth. Similarly, it may be expected that the UE 14 may be mounted on an airborne vehicle itself, having a ground speed of several hundreds of kilometres per hour. Another factor to be considered with NTN communications is a round trip time (RTT) between the UE and the satellite, which can be a contributor to overall delay experienced in an NTN system or deployment. Such a delay may be acceptable for applications such as browsing, but not for conversational or delay sensitive traffic. NTN deployment may foresee supporting services such as video streaming, video calling, and other conversational services. This is because the user may wish to access and enjoy the same services as when connected to a Terrestrial Network (TN), and therefore will expect an NTN to provide the same experience / performance as a TN while connected to an NTN deployment. Another main contributor to latency / delay is a distance between earth stations 430, and for UEs 14 in the overlapping region between two or more earth stations, an additional delay may be added if the feeder link is not reliable (i.e. more retransmissions are required) or if switching between feeder links is required. The distance between earth stations may be in the region of thousands of kilometres. This may cause additional delay if an application server or a MEC is deployed at only one of the earth stations for a UE, and if this UE therefore bounces between the coverage of the two earth stations.

[0062] Dual Connectivity

[0063] Dual connectivity is an arrangement in which a UE can connect and transmit and / or receive data for a communications session contemporaneously via an NTN such as via a satellite as shown in Figure 4 and via a terrestrial network (TN). An arrangement in which a UE 14 is able to support communication using dual connectivity is shown in Figure 5, which corresponds to the NTN network shown in Figure 4. As shown in Figure 5, the UE 14 is able to communicate via a wireless access interface 417 provided by the NTN network via the satellite 402 and the ground station referred to as an earth or base station 430 through the return link 432 as explained above. Also shown in Figure 5 is a terrestrial network (TN) comprising gNBs 500, 502, which provide cells of the TN 504, 506 within a cell boundary 508, 510. As represented by a dashed line 520, the UE 14 is also mobile and travels along a path represented by the dashed line 420. In addition as explained above the spot beams 420, 416, 418 provided by the NTN may also be moving and therefore the UE 14 may be in and out of coverage of the NTN. Similarly, the UE 14 may be in and out of coverage of the TN if it moves to a position where it is between cells 504, 506 of the TN. On the other hand, when the UE 14 is in a coverage area of the cells 504, 506 provided by the gNBs 500, 502 then there are occasions when the UE 14 can transmit and receive data via the TN, and may also be able to transmit and receive via the NTN within the spot being formed by the cell 416. However, when in a position where it is outside the coverage area provided by the TN such as shown in Figure 5, then the UE can communicate via the NTN using the wireless access interface provided by the satellite within a spot beam 416.

[0064] The UE 14 is configured to transmit uplink signals to and / or to receive downlink signals from the NTN infrastructure equipment 402 and to transmit uplink signals to and / or to receive downlink signals from the terrestrial infrastructure equipment 500, 502. In the following description reference to a coverage area being formed by a spot beam provided by a non-terrestrial network infrastructure equipment such as nonterrestrial infrastructure equipment 402 should also be interpreted as being a cell as an alternative because each spot beam may have one or more cell identities, in which case there is cell selection / reselection. In the example communications system shown in Figure 4, the NTN infrastructure equipment 402 may be one of a satellite, an airborne vehicle or an airborne platform.

[0065] Our co-pending European patent application number EP20189031.6 discloses solutions to a problem of how to reduce latency in NTN by utilizing dual connectivity at the UE. In particular, if one of the uplink or downlink traffic is heavier than the other, or transmitted via a longer route than the other, than utilizing a connection to a terrestrial gNB will be more efficient and reduce latency of the NTN or traffic can be switched between TN and NTN where TN has a coverage hole. The content of EP20189031.6 are incorporated herein by reference in its entirety.

[0066] When in a dual connectivity mode, the earth station 430 connected to the satellite 402, which may each separately or in combination be understood as being an NTN infrastructure equipment, may be, in the dual connectivity arrangement, a master gNB (MgNB) or master network or node (MN), while the terrestrial gNB 500, 502 may be a secondary gNB (SgNB) or secondary network or node (SN). Of course, the terrestrial gNB 500, 502 could instead be the MgNB and the non-terrestrial gNB 402, 430 the SgNB.

[0067] Multi-access edge computing (MEC), also referred to as edge computing or as mobile edge computing, is a type of network architecture which allows for cloud computing to be carried out at a mobile network edge. This allows for various functions and processes to be carried out away from the core network and thus much closer to the end user, vastly reducing latency and enabling higher bandwidth and real-time applications. MEC, which is described in further detail in [5], is expected to play a role in a number of applications of current and future 5G systems. One such application for MEC is in V2X communications. An MEC in a base station may collect data from vehicles. After the processing of the data at MEC, the base station sends the information onwards to other vehicles when and where appropriate. For example, vehicles may have sensors and therefore may monitor (and report to a base station) road surface conditions, obstacles, stranded break-down vehicles, traffic situations and so on. A MEC function at the base station collects this data from vehicles and may generate a map including potential risks. Then, the base station may broadcast (or indeed transmit via groupcast / unicast) the information / map to any vehicles in the relevant areas.

[0068] One challenge here is there will be out-of-coverage areas on roads, but the vehicle will always need a connection for the updating of the information and / or the receiving of the latest road status. One possible solution for this is again dual connectivity between NTN and TN. If the NTN is the MgNB and the TN is the SgNB, then the MEC may be migrated to the SgNB or close to SgNB in this example. One problem in this example scenario could be a time required for the MEC to be shifted from the NTN MN gNB to the TN SgNB. If the UE loses its connection to the TN gNB (i.e. the SgNB), the UE still has a connection to MgNB. The UE may then report the SgNB failure to the MgNB in this case.

[0069] NTN-TN dual connectivity can be used for fast switching during TN coverage holes. This is, as shown in Figure 5, in a situation in which the UE travels along the path 520, it can fall between a coverage area 508, 510 504, 506 of a TN. In such cases, an NTN and TN subnetworks can improve coverage by providing a network of networks. An NTN can provide an extension of cellular coverage to under-served areas accessing the TN and NTN cells during mobility of both the UE and the base station (e.g., satellite). Due to the services proposed in 6G, a coverage may be defined in relation to other KPIs such as latency, throughput, or robustness at a certain location. Dual connectivity can be used to enhance user throughput, whereby a UE connects to both Master Node or Network (MN) or Master gNB (MgNB) and Secondary Node or Network (SN) or secondary gNB (SgNB). Due to a long round trip time for NTN radio access [TS38.821], achieving a greater user throughput during NTN-TN dual connectivity may not be feasible. However, the dual connectivity can be used to provide coverage extension allowing a faster switch from TN to NTN, where the TN gNB does not provide good coverage.

[0070] With respect to a role of the NTN and TN infrastructure / gNB / B Ss as either MN or SN, there are two options . The first option is that the UE is connected to the TN as MN and to the NTN BS as SN. In this case, on the UE side, the NTN SN could be in deactivated state, or the NTN RF chain could be switched off for power saving purposes when the UE has a stable connection via the TN BS. If the NTN RF chain is switched off in the UE, then one benefit is that the UE will not perform any NTN measurements but will keep the RRC configuration for NTN. This RRC configuration will be ready for use once the UE moves away from the coverage of TN cell (and reconnects to the NTN). To detect the TN coverage loss and to switch on the NTN RF chain in time to use the NTN when it is available, the TN network may configure UE measurements such that the UE triggers a measurement report when the UE is about to lose TN coverage. This can be achieved by either triggering measurement events earlier or by defining a new measurement event when UE is about to lose TN coverage. Once the UE triggers this measurement report, it may switch on the NTN receiver at the same time. After receiving this measurement report, a TN BS provides a notification to the NTN BS to take the control of the UE and perform uplink / downlink transmissions. While the UE is out of coverage of the TN BS, the NTN cell could either continue to assume the role of SN or switch to the role of MN. 5G networks can support procedures for connection via SN when MN connection has failed, therefore the same procedures and signalling can be reused to establish communication via the SN. Therefore, it is not necessary that the NTN BS always takes the role of MN.

[0071] The second option is that the UE connects to the NTN cell as MN and to the TN cell as SN. In this case, any mobility between the TN cells can be handled as SN change or Primary Secondary Cell (PSCell) change, which are defined procedures in 5G, for example, as disclosed in TS37.340. However, one disadvantage of this approach will be that a UE handover will take place very frequently due to the movement of satellites and not necessarily due to the UE’s mobility. In this case, the UE will suffer user plane interruption due to handover every few seconds. This approach may have detrimental impact on UE power consumption and signalling load. Therefore, the first architectural TN-NTN option may be more beneficial than the second approach, at least in terms of reduced UE power consumption and lower service interruption time. However, selection amongst these two options depends on factors like agreement between NTN and TN mobile network operators (MNO) and a core network connectivity for each cell and the UE.

[0072] Finally, for the TN or NTN cell and MEC or mobile edge resource allocation, it may happen that a service is terminated at the TN edge and edge resources are located in a closer proximity to a TN cell / network infrastructure for service delivery. On the other hand, these resources may be deployed in different geographical locations for NTN edge resources. When the switch happens from the TN to the NTN BS, when the UE is in dual connectivity mode, the compute resources should also be moved accordingly in order to meet service requirements. So, when a UE is about to fall into a TN coverage hole then the compute resources at the edge of the TN BS may be moved from a node closer to the TN BS to a node closer to the NTN base / earth station.

[0073] In order for a UE to transmit in a new cell when its RF chain for that radio access technology (RAT) was switched off, the UE should acquire uplink synchronization first and then acquire an uplink grant.

[0074] Example embodiments can provide additional signalling between UE and the wireless communications network to address inter-working between a TN and an NTN. TN and NTN handover due to a difference in latency and signalling complexity of involving core network between the TN and NTN, which can present particular challenges.

[0075] Example embodiments can provide a method for operating a UE. The method comprises configuring transceiver circuitry of the UE for transmitting to and / or receiving from one or more NTN infrastructure equipment forming part of an NTN and for transmitting signals to and / or receiving signals from one or more TN infrastructure equipment forming part of a TN. The configuring includes establishing a dual connectivity mode in which the one or more TN infrastructure equipment is a master network or node(s) (MN) and the one or more NTN infrastructure equipment is a secondary network or node(s) (SN). The method comprises transmitting data to or receiving data from the TN infrastructure equipment via a first wireless access interface provided by the TN as a MN using the configured transceiver circuitry and deactivating the transceiver circuitry configured for transmitting and receiving data via a second wireless access interface provided by the NTN as a SN. The transceiver circuitry may be configured for the NTN or the transceiver circuitry may be configured for the NTN and powered down, for example the radio frequency (RF) components or other signal processing components. The method comprises detecting a likely loss or reduction of a radio coverage of the first wireless access interface provided by the TN, for example because the MN moves out of a radio coverage area of the TN, and determining a timing required for synchronisation with the NTN. The method may comprise activating the transceiver circuitry to transmit and to receive data via the second wireless access interface provided by the NTN using the indication of the timing received from the TN for synchronisation with the NTN.

[0076] Example embodiments can provide an arrangement in which timing information is established so that both TN or NTN and a UE are synchronised for transmitting or receiving signals for an active connection. If TN-NTN dual connectivity is not used for this particular use case and instead a handover procedure is used then there are certain disadvantages of using a handover procedure, for example, the UE performs RRM measurements continuously for eventual handover, that is in anticipation of a handover, which is also true for LTM (L2 Triggered Mobility) or RACH-less handover. However, for NTN-TN connection scenario, a UE performs measurements for NTN and switches on its NTN RF chain only when a reduction or loss of TN coverage level is detected. Otherwise, UE does not perform any NTN measurements.

[0077] A message sequence for option 1, in which a UE has established a radio bearer via a TN and experiences a loss of TN coverage is shown in Figure 6. As shown in Figure 6, as a first step the terrestrial network (TN) reconfigures or establishes a radio bearer with the UE by transmitting and receiving RRC configuration signals to reconfigure a radio bearer with the TN as the MN and NTN is the SN. The UE then transmits an RRC reconfiguration complete message 602. That is to say that the RRC reconfiguration message 600 configures dual connectivity whereby a master node is a TN infrastructure equipment and the secondary node is an NTN infrastructure equipment. In this case, NTN SN configuration is kept and not activated i.e., the UE is aware of satellite ephemeris information and other parameters, but this configuration is not used / activated. The UE sends the reconfiguration complete 602 and having reconfigured a radio bearer via the TN via an MN infrastructure equipment, the UE transmits the data to the TN 604, and the receives user data from the TN 604, and correspondingly the user data is transmitted to the core network CN and received from the core network arrow 606.

[0078] Subsequently the UE detects that it is losing radio coverage provided by cells of the TN or has lost coverage from the TN and so transmits a loss of TN coverage message 608 TN. The TN then transmits an activate NTN message 610, to the NTN. At process step 612, the UE then activates its NTN transceiver that is powering up components such as the RF part as well as signal processing part in order to transmit and receive signals by the NTN. The TN MN transmits and activate NTN message 614 to trigger a time synchronisation with the NTN. Having established synchronisation with the NTN, and configured its transceiver, the UE can transmit and receive signals via the NTN. The UE can then transmit data to and receive data from the NTN as represented by arrows 616 and the NTN transmits the user data to and receives the user data from the core network (CN) as represented by arrows 618. According to these steps 608, 610, 612, 614, the UE sends TN coverage loss message 608, as described in our co-pending patent application EP20189031.6 the content of which is incorporated by reference in its entirety. In this case, the TN cell will alert NTN cell, and the UE can switch on its NTN receiver when TN coverage loss message 608 is sent and start searching for NTN cell in step 612. At this stage, the UE may not be uplink synchronised with an NTN cell.

[0079] Sometime later, the UE detects that it has moved into an area where there is radio coverage from the TN because it has moved to one of the cells of a radio network part of the wireless communications network via TN or moved back to the coverage of the same cell as it was connected before. Accordingly, the UE transmits a message 620 indicating that it is now in an area radio coverage with the TN. The NTN transmits a message 622 to the TN to activate the TN. The TN then transmits and activates TN message 624 also commands the UE to acquire time synchronisation with the TN. The UE therefore activates its transceiver to transmit and to receive signals from the TN and synchronises its transceiver with the TN. The UE 14 can then transmit and receive data via the TN 626.

[0080] According to example embodiments shown in Figure 6, messages 614, 620 and 622 are messages transmitted in accordance with example embodiments in order to synchronise and activate the UE’s transceiver to communicate via the NTN respectively in accordance with example embodiments.

[0081] According to example embodiments, the UE receives a command 614 from TN, which could be similar to a PDCCH order to trigger a RACH procedure to synchronise with NTN. In response to the activate NTN message 610 sent from the TN to the NTN, the NTN reserves RACH resources from NTN cell in advance as a process step 611. The TN may send the command 610 as a conditional command before the link between the UE and the TN is lost or deteriorates to a level in which it cannot support communication. The condition can be associated with e.g., radio link quality and the UE will initiate a RACH procedure with the NTN once the condition for switching from the TN to the NTN cells have been fulfilled.

[0082] According to another embodiment, the UE can perform a RACH procedure without receiving the activate NTN and timing sync message 614, such as a PDCCH, if it is aware of RACH resources which can already be indicated as part of NTN-TN dual connectivity configuration. The NTN can provide an uplink grant of uplink resources for transmitting and downlink resources for receiving the user data 616, 618 in a random access response (RAR), which may form the activate NTN / timing sync message 614 for uplink transmission and the UE then sends a first uplink message or the user data to NTN 616, 618.

[0083] In some examples the UE acquires synchronisation with the NTN without using a RACH procedure. This can provide an advantage because the RACH procedure can be time consuming. Such a RACH-less procedure in LTM is identified in 3GPP TS38.300 section 9.2.3.5.1 and comprises re-using a timing advance from a current cell under predetermined conditions.

[0084] In another example, an NTN UE can estimate an uplink timing advance to a certain accuracy based on its location, and received ephemeris information of the satellites and may include other parameters, which may be received in the RRC reconfiguration message 600. These parameters may be for example Kmac. As such, the UE may synchronise without a RACH procedure. However, having acquired synchronisation of the NTN the UE informs the TN that it has moved to the NTN network. In one embodiment, the NTN may blindly send a downlink message to this UE along with an uplink grant assuming that the UE has a valid configuration and has already powered up its NTN receiver which includes establishing (switching on) its NTN protocol stack. If the UE is able to receive this blind downlink message then it can also include either a PDCCH order for RACH and / or an uplink grant.

[0085] In another embodiment, the UE can receive an NTN uplink timing advance and uplink grant from the TN network. The TN network can coordinate with the UE to establish these parameters and a transceiver configuration for the NTN network after or during the activate NTN message 614 from the TN network. According to some example embodiments, the UE receives, in the RRC reconfiguration 600, an indication of resources of the NTN in which it can perform a RACH to establish synchronisation with the NTN. According to this example, the UE may send the Loss of TN coverage message 608 after the Activate NTN and timing sync message 614.

[0086] According to some example embodiments, the UE performs regular timing synchronisation with NTN in the background when connected to TN i.e. UE perform NTN measurements and timing synchronisation at regular intervals even when NTN SN status is deactivated.

[0087] While the UE is connected to NTN, the UE can acquire measurement parameters to configure its transceiver for both the NTN and the TN in dual connectivity mode. In general, NTN connectivity could be for a shorter duration, which covers the TN coverage holes only. A technical problem is that the UE’s time in the NTN may not be predictable and may be for shorter or longer time periods.

[0088] If the UE is performing RRM measurements on both NTN and TN frequencies, then existing methods such as for example a conditional PCell / PSCell switching procedure or LTM can be used without any need to change these procedures. PCell / PSCell switching is disclosed in TS 37.340. This is for cases where the uplink timing advance is configured by the TN or NTN, i.e., the same as the source cell, where Ta=0 or the case where the timing advance value is signalled by the TN or NTN or pre-acquired by the UE. In another embodiment, instead of the UE transmitting the Good TN coverage indication message 620, the TN can reserve a periodic resource of the uplink or downlink wireless access interface provided by the TN with the RRC reconfiguration message 600 received from TN so that when coverage returns UE can transmit in the uplink at least to the TN.

[0089] For completeness an example operation of a UE 14 being served in dual connectivity mode from a TN and an NTN according to option 2 which shown in Figure 7. In option 2 the technical issues in respect of establishing synchronisation with the TN after loss of coverage of the TN when the UE is served by the NTN as an MN can be served by existing techniques. This is because if the UE returns to coverage area served by the TN, then the UE can establish synchronisation using conventional techniques. Furthermore, if the TN is acting as an SN, then the UE will continue to handover between cells as primary cells and secondary cells (PCell / PSCell).

[0090] As shown in Figure 7 an RRC reconfiguration message 700 is transmitted by the NTN acting as an MN to the UE 14, which also identifies that the TN is the SN. A reconfiguration complete message 702 is transmitted by the UE to the NTN to complete the RRC configuration. The UE is then operating in a dual connectivity mode in which it is transmitting data to the TN 704, which is then transmitted onto the CN 706. A loss or reduction of TN coverage is then detected by the UE and transmitted to the NTN as the MN 708. Since the NTN is the MN, the UE is in a state where its transceiver is powered up and synchronised with the NTN. Therefore, user data can be transmitted to the NTN 710 which is then transmitted by the NTN to CN 712. Once the UE enters an area where there is good radio coverage, the UE transmits a message 714 indicating that the UE has returned to an area where there is good coverage from the TN. The NTN can then transmit a message 716 to activate the TN, which triggers the TN to transmit an activate the TN and timing sync message 718 which could be a downlink control signal such as PDCCH. The UE then continues to transmit user data 720 to the TN.

[0091] As indicated above, since the TN is the SN, the UE can continue to maintain its transceiver circuitry in an active state to maintain equalisation and switch between primary and secondary cells as explained above. Since the NTN is the MN, the transceiver circuitry is continuously activated and therefore the UE remains within synchronisation of the NTN. In this case, it is not possible for the UE to switch off / de-activate the NTN RF or TN RF circuitry because NTN node is MN and mobility anchor. So, existing procedures like CPAC, LTM and RACH-less HO can be re-used. If there is enough room for TN SN to be put into deactivation state then there is an existing procedure

[0092] As will be appreciated from the above discussion, embodiments address a problem of switching or handing over from a TN to an NTN in a situation where a UE cannot or does not perform measurements of the wireless access interface. By switching off the transceiver for transmitting and receiving signals by the NTN, a significant power saving can be made the situation where it is not always possible for the UE to measure the NTN.

[0093] Those skilled in the art would further appreciate that such infrastructure equipment and / or communications devices as herein defined may be further defined in accordance with the various arrangements and embodiments discussed in the preceding paragraphs. It would be further appreciated by those skilled in the art that such infrastructure equipment and communications devices as herein defined and described may form part of communications systems other than those defined by the present disclosure. The following numbered paragraphs provide further example aspects and features of the present technique:

[0094] Paragraph 1. A method of operating a communications device comprising configuring transceiver circuitry of the communications device for transmitting uplink signals to and / or receiving downlink signals from one or more non-terrestrial network infrastructure equipment forming part of a non-terrestrial network, NTN, and for transmitting uplink signal to and / or for receiving uplink signals from one or more terrestrial network infrastructure equipment forming part of a terrestrial network, TN, the configuring including establishing a dual connectivity mode in which the one or more TN infrastructure equipment is a master network and the one or more NTN infrastructure equipment is a secondary network, transmitting data to or receiving data from the TN infrastructure equipment via a first wireless access interface provided by the TN as a master network using the configured transceiver circuitry, de-activating the transceiver circuitry configured for transmitting and receiving data via a second wireless access interface provided by the NTN as a secondary network, detecting a likely loss or reduction of a radio coverage of the first wireless access interface provided by the TN, determining a timing required for synchronisation with the NTN, activating the transceiver circuitry to transmit and to receive data via the second wireless access interface provided by the NTN using the indication of the timing received from the TN for synchronisation with the NTN.

[0095] Paragraph 2. A method of paragraph 1, wherein the determining a timing required for synchronisation with the NTN comprises receiving an indication of the timing required for synchronisation with the NTN from the TN received via the first wireless access interface before the radio coverage of the first wireless access interface is lost.

[0096] Paragraph 3. A method of paragraph 2, wherein the receiving the indication of the timing required for synchronisation with the NTN comprises transmitting a message indicating that the communications device is likely to have a loss or reduction of the radio coverage of the first wireless access interface, and in response, receiving the indication of the timing required for synchronisation with the NTN from the TN.

[0097] Paragraph 4. A method of paragraph 1, wherein the determining the timing required for synchronisation with the NTN comprises transmitting a message indicating that the communications device is likely to have a loss or reduction of the radio coverage of the first wireless access interface, and in response, receiving a command from the TN to establish the timing required for synchronisation with the NTN.

[0098] Paragraph 5. A method of paragraph 4, wherein the command from the TN to establish the timing required for synchronisation with the NTN is included in a Physical Downlink Control Channel, PDCCH, message.

[0099] Paragraph 6. A method of paragraph 4 or 5, wherein the command is for the communications device to perform a Random Access Channel, RACH, procedure with the NTN to establish the timing required for the synchronisation with the NTN.

[0100] Paragraph 7. A method of paragraph 4, 5 or 6, wherein the command from the TN to establish the timing required for synchronisation with the NTN includes a conditional requirement for the communications device to establish the timing required for synchronisation with the NTN when a determined radio coverage of the first wireless access interface has reduced below a predetermined level. Paragraph 8. A method of paragraph 7, comprising determining a radio link quality of the first wireless access interface provided by the one or more infrastructure equipment of the TN, comparing the radio link quality of the first wireless access interface with a predetermined threshold, and determining that the condition for establishing the timing required for synchronisation with the NTN, if the radio link quality has fallen below the predetermined threshold.

[0101] Paragraph 9. A method of paragraph 1, wherein the determining the timing required for synchronisation with the NTN comprises performing a Random Access Channel, RACH, procedure with the NTN to establish the timing required for the synchronisation with the NTN using preconfigured RACH resources of the NTN. Paragraph 10. A method of paragraph 9, wherein the configuring transceiver circuitry of the communications device for transmitting signals to and / or receiving signals from the NTN comprises receiving a radio resource control, RRC, reconfiguration message, and the RACH resources of the NTN are preconfigured by an indication of the RACH resources provided with the RRC reconfiguration message.

[0102] Paragraph 11. A method of paragraph 1, wherein the determining a timing required for synchronisation with the NTN comprises determining a location of the communications device, calculating the timing required for synchronisation with the NTN based on the location of the communications device and ephemeris information which includes a location of the one or more NTN infrastructure equipment.

[0103] Paragraph 12. A method of any of paragraphs 1 to 11, comprising transmitting data to or receiving data from the NTN infrastructure equipment via a second wireless access interface provided by the NTN as the secondary network using the configured transceiver circuitry, detecting that a likelihood that a radio coverage of the first wireless access interface provided by the TN will be sufficient to support transmitting signals to or receiving signals from the TN, transmitting an indication to the NTN that radio coverage provided by the first wireless communications network can support transmitting signals to and / or receiving signals from the TN, and transmitting signals to and / or receiving signals from the TN.

[0104] Paragraph 13. A method of paragraph 12, comprising receiving from the TN an indication of one or more of an activation of the TN and an indication of a timing for synchronisation with the TN.

[0105] Paragraph 14. A method of paragraphs 1 to 11, wherein the configuring transceiver circuitry of the communications device for transmitting signals to and / or receiving signals from the TN comprises receiving a configuration for configuring the transceiver circuitry of the communications device for transmitting signals to and / or receiving signals from the TN, which includes a configuration of periodic communications resources of the first wireless access interface, transmitting data to or receiving data from the NTN infrastructure equipment via a second wireless access interface provided by the NTN as the secondary network using the configured transceiver circuitry, detecting that a likelihood that a radio coverage of the first wireless access interface provided by the TN will be sufficient to support transmitting signals to or receiving signals from the TN, and transmitting signals to and / or receiving signals from the TN using the configured periodic communications resources.

[0106] Paragraph 15. A method of operating a communications device comprising configuring transceiver circuitry of the communications device for transmitting uplink signals to and / or receiving downlink signals from one or more non-terrestrial network infrastructure equipment forming part of a non-terrestrial network, NTN, and for transmitting uplink signal to and / or for receiving uplink signals from one or more terrestrial network infrastructure equipment forming part of a terrestrial network, TN, the configuring including establishing a dual connectivity mode in which the one or more NTN infrastructure equipment is a master network and the one or more TN infrastructure equipment is a secondary network, transmitting data to or receiving data from the NTN infrastructure equipment via a wireless access interface provided by the NTN as a master network using the configured transceiver circuitry, detecting a likely loss or reduction of a radio coverage of the wireless access interface provided by the NTN, determining a timing required for synchronisation with the TN, activating the transceiver circuitry to transmit and to receive data via a wireless access interface provided by the TN using the determined timing required for the synchronisation with the TN. Paragraph 16. A method of paragraph 15, wherein the determining the timing required for the synchronisation with the TN comprises performing a Primary Cell, Pcell, to Primary Secondary Cell, PSCell, change.

[0107] Paragraph 17. A method of paragraph 15, wherein the determining the timing required for the synchronisation with the TN comprises performing a RACH-less synchronisation determination. Paragraph 18. A method of paragraph 15, wherein the determining the timing required for the synchronisation with the TN comprises performing a Layer 2 Triggered Mobility, LTM.

[0108] Paragraph 19. A method of paragraph 15, wherein the determining the timing required for the synchronisation with the TN comprises performing a conditional handover.

[0109] Paragraph 20. A communications device for communicating via a wireless communications network by transmitting signals to and / or receiving signals from a wireless communications network, the communications device comprising transceiver circuitry configured for transmitting signals via a wireless access interface provided by the wireless communications network, and for receiving signals transmitter from the infrastructure equipment via the wireless access interface, and controller circuitry, the controller circuitry configuring the transceiver circuitry of the communications device to transmit uplink signals to and / or receiving downlink signals from one or more non-terrestrial network infrastructure equipment forming part of a non-terrestrial network, NTN, and to transmit uplink signal to and / or to receive uplink signals from one or more terrestrial network infrastructure equipment forming part of a terrestrial network, TN, the configuring including establishing a dual connectivity mode in which the one or more TN infrastructure equipment is a master network and the one or more NTN infrastructure equipment is a secondary network, and the controller circuitry configuring the transceiver circuitry to transmit data to or to receive data from the TN infrastructure equipment via a first wireless access interface provided by the TN as a master network using the configured transceiver circuitry, to de-activate the transceiver circuitry configured for transmitting and receiving data via a second wireless access interface provided by the NTN as a secondary network, to detect a likely loss or reduction of a radio coverage of the first wireless access interface provided by the TN, to determine a timing required for synchronisation with the NTN, and to activate the transceiver circuitry to transmit and to receive data via the second wireless access interface provided by the NTN using the indication of the timing received from the TN for synchronisation with the NTN.

[0110] Paragraph 21. A communications device for communicating via a wireless communications network by transmitting signals to and / or receiving signals from a wireless communications network, the communications device comprising transceiver circuitry configured for transmitting signals via a wireless access interface provided by the wireless communications network, and for receiving signals transmitter from the infrastructure equipment via the wireless access interface, and controller circuitry, the controller circuitry configuring the transceiver circuitry of the communications device to transmit uplink signals to and / or receiving downlink signals from one or more non-terrestrial network infrastructure equipment forming part of a non-terrestrial network, NTN, and to transmit uplink signal to and / or to receive uplink signals from one or more terrestrial network infrastructure equipment forming part of a terrestrial network, TN, the configuring including establishing a dual connectivity mode in which the one or more TN infrastructure equipment is a master network and the one or more NTN infrastructure equipment is a secondary network, and the controller circuitry configuring the transceiver circuitry to transmit data to or receiving data from the NTN infrastructure equipment via a wireless access interface provided by the NTN as a master network using the configured transceiver circuitry, to detect a likely loss or reduction of a radio coverage of the wireless access interface provided by the NTN, to determine a timing required for synchronisation with the TN, and to activate the transceiver circuitry to transmit and to receive data via a wireless access interface provided by the TN using the determined timing required for the synchronisation with the TN.

[0111] In so far as embodiments of the disclosure have been described as being implemented, at least in part, by software-controlled data processing apparatus, it will be appreciated that a non-transitory machine- readable medium carrying such software, such as an optical disk, a magnetic disk, semiconductor memory or the like, is also considered to represent an embodiment of the present disclosure.

[0112] 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.

[0113] 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.

[0114] 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. References

[0115] [1] TR 38.811, “Study on New Radio (NR) to support non terrestrial networks (Release 15)”, 3rd Generation Partnership Project, December 2017.

[0116] [2] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radio access”, John Wiley and Sons, 2009.

[0117] [3] RP-172834, “Revised WID on New Radio Access Technology,” NTT DOCOMO, RAN#78.

[0118] [4] TR 38.913, “Study on Scenarios and Requirements for Next Generation Access Technologies (Release 14)”, 3rd Generation Partnership Project.

[0119] [5] “Multi-access Edge Computing (MEC)”, European Telecommunications Standards Institute (ETSI), [Online], Available at: https: / / www.etsi.org / technologies / multi-access-edge-computing, accessed July 2020.

[0120] [6] TS 38.321, “NR: Medium Access Control (MAC) Protocol Specification (Release 15, vl5.4.0)”, 3GPP, January 2019.

[0121] [7] “Toward fully connected vehicles: Edge computing for advanced automotive communications”, 5G Automotive Association (5GAA), [Online], Available at: https: / / 5gaa.org / wp- content / uploads / 2017 / 12 / 5GAA_T- 170219-whitepaper-EdgeComputing_5GAA.pdf, accessed July 2020.

Claims

CLAIMSWhat is claimed is:

1. A method of operating a communications device comprising configuring transceiver circuitry of the communications device for transmitting uplink signals to and / or receiving downlink signals from one or more non-terrestrial network infrastructure equipment forming part of a non-terrestrial network, NTN, and for transmitting uplink signal to and / or for receiving uplink signals from one or more terrestrial network infrastructure equipment forming part of a terrestrial network, TN, the configuring including establishing a dual connectivity mode in which the one or more TN infrastructure equipment is a master network and the one or more NTN infrastructure equipment is a secondary network, transmitting data to or receiving data from the TN infrastructure equipment via a first wireless access interface provided by the TN as a master network using the configured transceiver circuitry, de-activating the transceiver circuitry configured for transmitting and receiving data via a second wireless access interface provided by the NTN as a secondary network, detecting a likely loss or reduction of a radio coverage of the first wireless access interface provided by the TN, determining a timing required for synchronisation with the NTN, activating the transceiver circuitry to transmit and to receive data via the second wireless access interface provided by the NTN using the indication of the timing received from the TN for synchronisation with the NTN.

2. A method of claim 1, wherein the determining a timing required for synchronisation with the NTN comprises receiving an indication of the timing required for synchronisation with the NTN from the TN received via the first wireless access interface before the radio coverage of the first wireless access interface is lost.

3. A method of claim 2, wherein the receiving the indication of the timing required for synchronisation with the NTN comprises transmitting a message indicating that the communications device is likely to have a loss or reduction of the radio coverage of the first wireless access interface, and in response, receiving the indication of the timing required for synchronisation with the NTN from the TN.

4. A method of claim 1, wherein the determining the timing required for synchronisation with the NTN comprises transmitting a message indicating that the communications device is likely to have a loss or reduction of the radio coverage of the first wireless access interface, and in response, receiving a command from the TN to establish the timing required for synchronisation with the NTN.

5. A method of claim 4, wherein the command from the TN to establish the timing required for synchronisation with the NTN is included in a Physical Downlink Control Channel, PDCCH, message.

6. A method of claim 4, wherein the command is for the communications device to perform a Random Access Channel, RACH, procedure with the NTN to establish the timing required for the synchronisation with the NTN.

7. A method of claim 4, wherein the command from the TN to establish the timing required for synchronisation with the NTN includes a conditional requirement for the communications device to establish the timing required for synchronisation with the NTN when a determined radio coverage of the first wireless access interface has reduced below a predetermined level.

8. A method of claim 7, comprising determining a radio link quality of the first wireless access interface provided by the one or more infrastructure equipment of the TN, comparing the radio link quality of the first wireless access interface with a predetermined threshold, and determining that the condition for establishing the timing required for synchronisation with the NTN, if the radio link quality has fallen below the predetermined threshold.

9. A method of claim 1, wherein the determining the timing required for synchronisation with the NTN comprises performing a Random Access Channel, RACH, procedure with the NTN to establish the timing required for the synchronisation with the NTN using preconfigured RACH resources of the NTN.

10. A method of claim 9, wherein the configuring transceiver circuitry of the communications device for transmitting signals to and / or receiving signals from the NTN comprises receiving a radio resource control, RRC, reconfiguration message, and the RACH resources of the NTN are preconfigured by an indication of the RACH resources provided with the RRC reconfiguration message.

11. A method of claim 1, wherein the determining a timing required for synchronisation with the NTN comprises determining a location of the communications device, calculating the timing required for synchronisation with the NTN based on the location of the communications device and ephemeris information which includes a location of the one or more NTN infrastructure equipment.

12. A method of claim 1, comprising transmitting data to or receiving data from the NTN infrastructure equipment via a second wireless access interface provided by the NTN as the secondary network using the configured transceiver circuitry, detecting that a likelihood that a radio coverage of the first wireless access interface provided by the TN will be sufficient to support transmitting signals to or receiving signals from the TN, transmitting an indication to the NTN that radio coverage provided by the first wireless communications network can support transmitting signals to and / or receiving signals from the TN, and transmitting signals to and / or receiving signals from the TN.

13. A method of claim 12, comprising receiving from the TN an indication of one or more of an activation of the TN and an indication of a timing for synchronisation with the TN.

14. A method of claim 1, wherein the configuring transceiver circuitry of the communications device for transmitting signals to and / or receiving signals from the TN comprises receiving a configuration for configuring the transceiver circuitry of the communications device for transmitting signals to and / or receiving signals from the TN, which includes a configuration of periodic communications resources of the first wireless access interface,transmiting data to or receiving data from the NTN infrastructure equipment via a second wireless access interface provided by the NTN as the secondary network using the configured transceiver circuitry, detecting that a likelihood that a radio coverage of the first wireless access interface provided by the TN will be sufficient to support transmiting signals to or receiving signals from the TN, and transmiting signals to and / or receiving signals from the TN using the configured periodic communications resources.

15. A method of operating a communications device comprising configuring transceiver circuitry of the communications device for transmiting uplink signals to and / or receiving downlink signals from one or more non-terrestrial network infrastructure equipment forming part of a non-terrestrial network, NTN, and for transmiting uplink signal to and / or for receiving uplink signals from one or more terrestrial network infrastructure equipment forming part of a terrestrial network, TN, the configuring including establishing a dual connectivity mode in which the one or more NTN infrastructure equipment is a master network and the one or more TN infrastructure equipment is a secondary network, transmiting data to or receiving data from the NTN infrastructure equipment via a wireless access interface provided by the NTN as a master network using the configured transceiver circuitry, detecting a likely loss or reduction of a radio coverage of the wireless access interface provided by the NTN, determining a timing required for synchronisation with the TN, activating the transceiver circuitry to transmit and to receive data via a wireless access interface provided by the TN using the determined timing required for the synchronisation with the TN.

16. A method of claim 15, wherein the determining the timing required for the synchronisation with the TN comprises performing a Primary Cell, Pee 11, to Primary Secondary Cell, PSCell, change.

17. A method of claim 15, wherein the determining the timing required for the synchronisation with the TN comprises performing a RACH-less synchronisation determination.

18. A method of claim 15, wherein the determining the timing required for the synchronisation with the TN comprises performing a Layer 2 Triggered Mobility, LTM.

19. A method of claim 15, wherein the determining the timing required for the synchronisation with the TN comprises performing a conditional handover.

20. A communications device for communicating via a wireless communications network by transmiting signals to and / or receiving signals from a wireless communications network, the communications device comprising transceiver circuitry configured for transmiting signals via a wireless access interface provided by the wireless communications network, and for receiving signals transmiter from the infrastructure equipment via the wireless access interface, and controller circuitry, the controller circuitry configuring the transceiver circuitry of the communications device to transmit uplink signals to and / or receiving downlink signals from one or more non-terrestrial network infrastructure equipment forming part of a non-terrestrial network, NTN, and to transmit uplink signal to and / or to receive uplink signals from one or more terrestrial network infrastructure equipment forming part of a terrestrial network, TN, the configuring including establishing a dual connectivity mode in which the one or more TN infrastructure equipment is a master network andthe one or more NTN infrastructure equipment is a secondary network, and the controller circuitry configuring the transceiver circuitry to transmit data to or to receive data from the TN infrastructure equipment via a first wireless access interface provided by the TN as a master network using the configured transceiver circuitry, to de-activate the transceiver circuitry configured for transmitting and receiving data via a second wireless access interface provided by the NTN as a secondary network, to detect a likely loss or reduction of a radio coverage of the first wireless access interface provided by the TN, to determine a timing required for synchronisation with the NTN, and to activate the transceiver circuitry to transmit and to receive data via the second wireless access interface provided by the NTN using the indication of the timing received from the TN for synchronisation with the NTN.

21. A communications device for communicating via a wireless communications network by transmitting signals to and / or receiving signals from a wireless communications network, the communications device comprising transceiver circuitry configured for transmitting signals via a wireless access interface provided by the wireless communications network, and for receiving signals transmitter from the infrastructure equipment via the wireless access interface, and controller circuitry, the controller circuitry configuring the transceiver circuitry of the communications device to transmit uplink signals to and / or receiving downlink signals from one or more non-terrestrial network infrastructure equipment forming part of a non-terrestrial network, NTN, and to transmit uplink signal to and / or to receive uplink signals from one or more terrestrial network infrastructure equipment forming part of a terrestrial network, TN, the configuring including establishing a dual connectivity mode in which the one or more TN infrastructure equipment is a master network and the one or more NTN infrastructure equipment is a secondary network, and the controller circuitry configuring the transceiver circuitry to transmit data to or receiving data from the NTN infrastructure equipment via a wireless access interface provided by the NTN as a master network using the configured transceiver circuitry, to detect a likely loss or reduction of a radio coverage of the wireless access interface provided by the NTN, to determine a timing required for synchronisation with the TN, and to activate the transceiver circuitry to transmit and to receive data via a wireless access interface provided by the TN using the determined timing required for the synchronisation with the TN.

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