Infrastructure equipment, communications devices and methods

A method for operating an infrastructure equipment forming part of a wireless communications network, which includes a base station and a non-terrestrial network part, the non-terrestrial network part transmitting a plurality of spot beams to provide a wireless access interface for transmitting signals to and receiving signals representing data from a communications device within a coverage region formed by a first of the spot beams. The method comprises receiving assistance information from the communications device, identifying, based on the received assistance information, that a backup configuration should be updated to indicate one or more others of the spot beams, the one or more others of the spot beams being backups to the first spot beam in case of beam failure of the first spot beam, and transmitting a backup beam reconfiguration message to the communications device, the backup beam configuration message comprising an indication of the updated backup configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on PCT filing PCT/EP2019/084403, filed Dec. 10, 2019, which claims priority to EP 18214932.8, filed Dec. 20, 2018, the entire contents of each are incorporated herein by reference.

BACKGROUND

Field of Disclosure

The present disclosure relates generally to communications devices, infrastructure equipment and methods of operating communications devices and infrastructure equipment and specifically to methods of performing beam failure recovery in non-terrestrial networks.

Description of Related Art

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

In view of this there is expected to be a desire for future wireless communications networks, for example those which may be referred to as 5G or new radio (NR) system/new radio access technology (RAT) systems, as well as future iterations/releases of existing systems, to efficiently support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles.

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 an airborne or space-borne vehicle [1].

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’ (IoT) 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.

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.

SUMMARY OF THE DISCLOSURE

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

Embodiments of the present technique can provide a method for operating an infrastructure equipment forming part of a wireless communications network. The wireless communications network comprises a base station and a non-terrestrial network part, the non-terrestrial network part transmitting a plurality of spot beams to provide a wireless access interface for transmitting signals to and receiving signals representing data from a communications device within a coverage region formed by a first of the spot beams forming a cell. The method comprises receiving assistance information from the communications device, identifying, based on the received assistance information, that a backup configuration should be updated to indicate one or more others of the spot beams, the one or more others of the spot beams being backups to the first spot beam in case of beam failure of the first spot beam, and transmitting a backup beam reconfiguration message to the communications device, the backup beam configuration message comprising an indication of the updated backup configuration

Embodiments of the present technique, which further relate to methods of operating communications devices, communications devices, infrastructure equipment and circuitry for communications devices and infrastructure equipment, allow for performance and enhancement of beam failure recovery processes in non-terrestrial networks. Such enhanced beam failure recovery processes allow for legacy beam failure recovery procedures to be accelerated.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Long Term Evolution Advanced Radio Access Technology (4G)

The network10includes a plurality of base stations11connected to a core network12. Each base station provides a coverage area13(i.e. a cell) within which data can be communicated to and from terminal devices14. Data is transmitted from base stations11to terminal devices14within their respective coverage areas13via a radio downlink (DL). Data is transmitted from terminal devices14to the base stations11via a radio uplink (UL). The core network12routes data to and from the terminal devices14via the respective base stations11and provides functions such as authentication, mobility management, charging and so on. Terminal devices may also be referred to as mobile stations, user equipment (UE), user terminal, mobile radio, communications device, and so forth. Base stations, which are an example of network infrastructure equipment/network access node, may also be referred to as transceiver stations/nodeBs/e-nodeBs/eNBs/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.

New Radio Access Technology (5G)

As mentioned above, the embodiments of the present disclosure can also find application with advanced wireless communications systems such as those referred to as 5G or New Radio (NR) Access Technology. The use cases that are considered for NR include:Enhanced Mobile Broadband (eMBB)Massive Machine Type Communications (mMTC)Ultra Reliable & Low Latency Communications (URLLC) [3]

eMBB services are characterised by high capacity with a requirement to support up to 20 Gb/s. The requirement for URLLC is a reliability of 1-10−5(99.999%) for one transmission of a relatively short packet such as 32 bytes with a user plane latency of 1 ms [4].

The elements of the wireless access network shown inFIG.1may be equally applied to a 5G new RAT configuration, except that a change in terminology may be applied as mentioned above.

FIG.2is a schematic diagram illustrating a network architecture for a new RAT wireless mobile telecommunications network/system30based on previously proposed approaches which may also be adapted to provide functionality in accordance with embodiments of the disclosure described herein. The new RAT network30represented inFIG.2comprises a first communication cell20and a second communication cell21. Each communication cell20,21, comprises a controlling node (centralised unit)26,28in communication with a core network component31over a respective wired or wireless link36,38. The respective controlling nodes26,28are also each in communication with a plurality of distributed units (radio access nodes/remote transmission and reception points (TRPs))22,24in their respective cells. Again, these communications may be over respective wired or wireless links. The distributed units22,24are responsible for providing the radio access interface for terminal devices connected to the network. Each distributed unit22,24has a coverage area (radio access footprint)32,34which together define the coverage of the respective communication cells20,21. Each distributed unit22,24includes transceiver circuitry22a,24afor transmission and reception of wireless signals and processor circuitry22b,24bconfigured to control the respective distributed units22,24.

In terms of broad top-level functionality, the core network component31of the new RAT telecommunications system represented inFIG.2may be broadly considered to correspond with the core network12represented inFIG.1, and the respective controlling nodes26,28and their associated distributed units/TRPs22,24may be broadly considered to provide functionality corresponding to base stations ofFIG.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 terminal devices may lie with the controlling node/centralised unit and/or the distributed units/TRPs.

A terminal device40is represented inFIG.2within the coverage area of the first communication cell20. This terminal device40may thus exchange signalling with the first controlling node26in the first communication cell via one of the distributed units22associated with the first communication cell20. In some cases communications for a given terminal device are routed through only one of the distributed units, but it will be appreciated in some other implementations communications associated with a given terminal device may be routed through more than one distributed unit, for example in a soft handover scenario and other scenarios.

The particular distributed unit(s) through which a terminal device is currently connected through to the associated controlling node may be referred to as active distributed units for the terminal device. Thus the active subset of distributed units for a terminal device may comprise one or more than one distributed unit (TRP). The controlling node26is responsible for determining which of the distributed units22spanning the first communication cell20is responsible for radio communications with the terminal device40at any given time (i.e. which of the distributed units are currently active distributed units for the terminal device). Typically this will be based on measurements of radio channel conditions between the terminal device40and respective ones of the distributed units22. In this regard, it will be appreciated the subset of the distributed units in a cell which are currently active for a terminal device will depend, at least in part, on the location of the terminal device within the cell (since this contributes significantly to the radio channel conditions that exist between the terminal device and respective ones of the distributed units).

In at least some implementations the involvement of the distributed units in routing communications from the terminal device to a controlling node (controlling unit) is transparent to the terminal device40. That is to say, in some cases the terminal device may not be aware of which distributed unit is responsible for routing communications between the terminal device40and the controlling node26of the communication cell20in which the terminal device is currently operating, or even if any distributed units22are connected to the controlling node26and involved in the routing of communications at all. In such cases, as far as the terminal device is concerned, it simply transmits uplink data to the controlling node26and receives downlink data from the controlling node26and the terminal device has no awareness of the involvement of the distributed units22, though may be aware of radio configurations transmitted by distributed units22. However, in other embodiments, a terminal device may be aware of which distributed unit(s) are involved in its communications. Switching and scheduling of the one or more distributed units may be done at the network controlling node based on measurements by the distributed units of the terminal device uplink signal or measurements taken by the terminal device and reported to the controlling node via one or more distributed units.

In the example ofFIG.2, two communication cells20,21and one terminal device40are shown for simplicity, but it will of course be appreciated that in practice the system may comprise a larger number of communication cells (each supported by a respective controlling node and plurality of distributed units) serving a larger number of terminal devices.

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

Thus certain embodiments of the disclosure as discussed herein may be implemented in wireless telecommunication systems/networks according to various different architectures, such as the example architectures shown inFIGS.1and2.

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 terminal device, wherein the specific nature of the network infrastructure equipment/access node and the terminal 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 station11as shown inFIG.1which is adapted to provide functionality in accordance with the principles described herein, and in other examples the network infrastructure equipment may comprise a control unit/controlling node26,28and/or a TRP22,24of the kind shown inFIG.2which is adapted to provide functionality in accordance with the principles described herein.

According to some radio access technologies, including the NR radio access technologies under development by 3GPP, a cell may be formed (or, in other words, ‘generated’) by a plurality of directional beams. Each beam may be characterised by a variance in gain with respect to a direction from the antenna; a beam may be considered ‘wide’, where the gain is consistently relatively high over a broad range of directions, or ‘narrow’, where relatively high gain is only achieved over a narrow range of directions. Depending on the direction of the communications device with respect to the infrastructure equipment, the gain of a particular beam may be sufficiently high (and the resulting coupling loss sufficiently low) to permit communications between the communications device and the infrastructure equipment via the beam. Beams may be formed for transmitting or receiving at the infrastructure equipment using phased antenna arrays, directional antennas, a combination of both, or other known techniques. Generally, a beam is named as a Transmission Configuration Indication (TCI) state in NR.

An overview of NR-NTN can be found in [1], and much of the following wording, along withFIGS.3and4, has been reproduced from that document as a way of background.

As a result of the wide service coverage capabilities and reduced vulnerability of space/airborne vehicles to physical attacks and natural disasters, Non-Terrestrial Networks are expected to: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,reinforce the 5G service reliability by providing service continuity for M2M/IoT devices or for passengers on board moving platforms (e.g. passenger vehicles-aircraft, ships, high speed trains, bus) or ensuring service availability anywhere especially for critical communications, future railway/maritime/aeronautical communications, and toenable 5G network scalability by providing efficient multicast/broadcast resources for data delivery towards the network edges or even user terminal.

The benefits relate to either Non-Terrestrial networks operating alone or to integrated terrestrial and Non-Terrestrial networks. They 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.

FIG.3illustrates a first example of an NTN featuring an access networking service relay nodes and based on a satellite/aerial with a bent pipe payload. In this example NTN, the satellite or the aerial will relay a “satellite friendly” NR signal between the gNodeB and the relay nodes in a transparent manner.

FIG.4illustrates a second example of an NTN featuring an access networking service relay nodes and based on a satellite/aerial coupled with a gNodeB. In this example NTN, the satellite or aerial embarks full or part of a gNodeB to generate or receive a “satellite friendly” NR signal to/form the relay nodes.

This requires sufficient on-board processing capabilities to be able to include a gNodeB or relay node functionality.

Relay node (RN) related use cases such as those shown inFIGS.3and4will 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, in addition to such RNs, proposed solutions of embodiments of the present technique could be equally applied to conventional RNs/UEs.

FIG.5schematically shows an example of a wireless communications system200which may be configured to operate in accordance with embodiments of the present disclosure. The wireless communications system200in this example is based broadly around an LTE-type or 5G-type architecture. Many aspects of the operation of the wireless communications system/network200are known and understood and are not described here in detail in the interest of brevity. Operational aspects of the wireless communications system200which are not specifically described herein may be implemented in accordance with any known techniques, for example according to the current LTE-standards or the proposed 5G standards.

The wireless communications system200comprises a core network part102(which may be a 5G core network or a NG core network) coupled to a radio network part. The radio network part comprises a base station (g-node B)101coupled to a non-terrestrial network part308. The non-terrestrial network part308may be an example of infrastructure equipment. Alternatively, or in addition, the non-terrestrial network part308may be mounted on a satellite vehicle or on an airborne vehicle.

The non-terrestrial network part308is further coupled to a communications device208, located within a cell202, by means of a wireless access interface provided by a wireless communications link206. For example, the cell202may correspond to the coverage area of a spot beam generated by the non-terrestrial network part308. The boundary of the cell202may depend on an altitude of the non-terrestrial network part308and a configuration of one or more antennas of the non-terrestrial network part308by which the non-terrestrial network part308transmits and receives signals on the wireless access interface.

The non-terrestrial network part308may be a satellite in an orbit with respect to the Earth, or may be mounted on such a satellite. For example, the satellite may be in a geo-stationary earth orbit (GEO) such that the non-terrestrial network part308does not move with respect to a fixed point on the Earth's surface. The geo-stationary earth orbit may be approximately 36,000 km above the Earth's equator. Alternatively, the satellite may be in a non-geostationary orbit (NGSO), so that the non-terrestrial network part308moves with respect to a fixed point on the Earth's surface. The non-terrestrial network part308may be an airborne vehicle such as an aircraft, or may be mounted on such a vehicle. The airborne vehicle (and hence the non-terrestrial network part308) may be stationary with respect to the surface of the Earth or may move with respect to the surface of the Earth.

InFIG.5, the base station101is shown as ground-based, and coupled to the non-terrestrial network part308by means of a wireless communications link204. The non-terrestrial network part308receives signals representing downlink data transmitted by the base station101on the wireless communications link204and, based on the received signals, transmits signals representing the downlink data via the wireless communications link206providing the wireless access interface for the communications device206. Similarly, the non-terrestrial network part308receives signals representing uplink data transmitted by the communications device206via the wireless access interface comprising the wireless communications link206and transmits signals representing the uplink data to the base station101on the wireless communications link204. The wireless communications links204,206may operate at a same frequency, or may operate at different frequencies.

The extent to which the non-terrestrial network part308processes the received signals may depend upon a processing capability of the non-terrestrial network part308. For example, the non-terrestrial network part308may receive signals representing the downlink data on the wireless communication link204, 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 link206. Alternatively, the non-terrestrial network part308may be configured to decode the signals representing the downlink data received on the wireless communication link204into 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 link206.

The non-terrestrial network part308may be configured to perform some of the functionality conventionally carried out by the base station101. In particular, latency-sensitive functionality (such as acknowledging a receipt of the uplink data, or responding to a Random Access (RACH) request, which would be well known to those skilled in the art) may be performed by the non-terrestrial network part308instead of by the base station101.

The base station101may be co-located with the non-terrestrial network part308; 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 station101and the non-terrestrial network part308. In such co-located arrangements, a wireless communications link between the base station101and a ground station (not shown) may provide connectivity between the base station101and the core network part102.

The communications device208shown inFIG.5may be configured to act as a relay node. That is, it may provide connectivity to one or more terminal devices such as the terminal device104. When acting as a relay node, the communications device208transmits and receives data to and from the terminal device104, and relays it, via the non-terrestrial network part308to the base station101. The communications device208, acting as a relay node, may thus provide connectivity to the core network part102for terminal devices which are within a transmission range of the communications device208.

It will be apparent to those skilled in the art that many scenarios can be envisaged in which the combination of the communications device208and the non-terrestrial network part308can provide enhanced service to end users. For example, the communications device208may 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 communications device208acting as a relay, which is coupled to the non-terrestrial network part308.

There is a need to ensure that connectivity for the communications device208with the base station101can be maintained, in light of the movement of the communications device208, the movement of the non-terrestrial network part308(relative to the Earth's surface), or both. According to conventional cellular communications techniques, a decision to change a serving cell of the communications device208may 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 communications device208is 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 non-terrestrial network part, such as the cell202generated by the non-terrestrial network part308. In particular, path loss may be primarily dependent on an altitude of the non-terrestrial network part308and may vary only to a very limited extent (if at all) at the surface of the Earth, within the coverage region of the cell202.

A further disadvantage of conventional techniques may be the relatively high rate at which cell changes occur for the communications device208obtaining service from one or more non-terrestrial network parts. For example, where the non-terrestrial network part308is mounted on a satellite in a low-earth orbit (LEO), the non-terrestrial network part308may complete an orbit of the Earth in around 90 minutes; the coverage of a cell generated by the non-terrestrial network part308will move very rapidly, with respect to a fixed observation point on the surface of the earth. Similarly, it may be expected that the communications device208may be mounted on an airborne vehicle itself, having a ground speed of several hundreds of kilometres per hour.

Unlike camping on a terrestrial cell, a RN/UE camps on a spot beam of a satellite which, in the case of (non-geo-stationary earth orbit (NGSEO) satellites, does move. This means that a RN/UE will camp on different spot beams (cells) and/or different satellites over time, regardless of whether or not the RN/UE itself is moving. As a result, it is foreseen that handover will likely be carried out much more frequently than in conventional terrestrial-based wireless networks, especially for LEO NTNs. For GEO NTNs, the spot beam coverage does not move, but handover will still be needed if the RN/UE is moving between the coverage of different spot beams. Handover procedure should be optimised in order to reduce the signalling overhead.

Beam Failure Recovery (BFR) in NR

Provided at least one activated beam (or TCI state) remains available for communication, then beam management processes can update and adapt the set of activated beams in response to one or more beams becoming unsuitable. Such beam management as used herein refers collectively to processes and techniques such as the measurement of signals transmitted on one or more beams, an assessment as to whether one or more beams satisfy respective beam failure conditions, indications transmitted by the communications device to the infrastructure equipment to indicate whether or not one or more beams satisfy respective beam failure conditions, a determination that the configuration or activated set of beams are modified, and transmissions indicating control information relating to the beams sent using an activated beam which has not satisfied the beam failure conditions. However, should all beams satisfy the beam failure conditions based on measurements from pre-configured reference signals, then it is necessary to initiate a procedure to recover from this situation. This procedure is referred to as beam failure recovery.

In more detail for NR, the beam failure recovery (BFR) procedure is introduced in [5]. As described in [5], for beam failure detection, the gNodeB configures the UE with beam failure detection reference signals and the UE declares beam failure when the number of beam failure instance indications from the physical layer reaches a configured threshold within a configured period. After beam failure is detected, the UE:triggers beam failure recovery by initiating a Random Access procedure on the PCell;selects a suitable beam to perform beam failure recovery (if the gNodeB has provided dedicated Random Access resources for certain beams, those will be prioritised by the UE);Receives gNodeB responses (i.e. DCI) on a preconfigured search space named as “recoverySearchSpaceId”.

Upon completion of the Random Access procedure, beam failure recovery is considered complete.

In an example beam failure recovery procedure initiated in response to a determination that activated beams satisfy the respective beam failure conditions, the communications device performs measurements of the signal strength (e.g. reference signal received power, RSRP) of the channel state information reference signals (CSI-RS) or synchronisation signal blocks associated with one or more beams which are configured but not activated. The measurements may be compared against a predetermined threshold, such as an RSRP threshold. If the communications device determines that the measurements associated with the one or more beams which are configured but not activated exceed the predetermined threshold, then the communications device transmits a beam failure recovery request message (which is an example of a beam failure indication) as a random access message using a physical random access channel (PRACH) of the new identified beam. Communications resources on the PRACH may have been previously indicated as suitable for non-contention based random access transmissions, in which case the beam failure recovery request message may be transmitted in a contention-free manner using those resources. Otherwise, the beam failure recovery request message may be transmitted in a contention based manner if dedicated resources are not configured.

After transmitting the beam failure recovery request message, the communications device monitors downlink communications resources associated with the new identified beam. More specifically, the communications device may monitor a configured recovery search space, which may be a ‘recoverySearchSpace’ as described above with relation to [5], having as an identity a ‘recoverySearchSpaceId’, for downlink control information (DCI). If the communications device receives downlink control information in the configured communications resources, which indicates that communications resources on a shared downlink channel (such as the physical downlink shared channel, PDSCH) are scheduled to be used for the transmission by the infrastructure equipment of a response to the beam failure recovery request message, then the communications device determines that the beam failure recovery is successful. In response to receiving the downlink control information, the communications device sets the new identified beam as an activated beam. The new (activated) beam can be used for subsequent communications between the infrastructure equipment and the communications device, including the transmission of control information to indication one or more beams which are to be activated for the communications device. The communications device may decode and process data transmitted using the scheduled communications resources on the shared downlink channel, for example in a conventional manner.

As described above, in NTN, the cell change/beam change procedure due to the satellite beam's movement is regarded as a handover/beam management procedure. One of the characteristics of such handover/beam management in NTN is that the target cell/satellite beam is somewhat predictable given the knowledge of satellite ephemeris (i.e. the position of the satellite in the sky at given times), the beam and satellite constellation, the UE's location and velocity information.

While, as in NR, a UE may still encounter beam failure in NTN, this may be in one of a number of ways, depending on the arrangement of the satellite beams as demonstrated byFIG.6. In Option a) ofFIG.6, a single Physical Cell Identifier (PCI) may be shared between a number of satellite beams, essentially between them forming a single cell (shown by the dotted lines), and each satellite beam of that cell may be formed of one (or several) Synchronisation Signal Blocks (SSBs). In Option b) ofFIG.6on the other hand, each satellite beam may be associated with a unique PCI, thus in effect each forming a separate cell.

The UE may detect a beam failure if, for example, an airplane flying within the beam between the UE and the satellite shadows the UE sufficiently to cause a break in its signal. One of the characteristics of NR beam failure is that the target beam is not predictable. However, in NTN, there is some predictability on the target beam, implying that certain enhancements can be applied in NTN for a smoother beam failure recovery. Furthermore, in NR, the beam failure recovery will trigger a contention-less random access procedure. Due to the long propagation delay issue, beam failure recovery should be enhanced in NTN. Embodiments of the present technique seek to provide enhancements to beam failure recovery processes in the context of NTN.

BFR Enhancement in NTN

FIG.7shows a part schematic, part message flow diagram representation of a wireless communications network comprising an infrastructure equipment701and a communications device702in accordance with embodiments of the present technique. The wireless communications network comprises a base station and a non-terrestrial network part, the non-terrestrial network part transmitting a plurality of spot beams to provide a wireless access interface for transmitting signals to and receiving signals representing data from the communications device702within a coverage region formed by a first of the spot beams.

The infrastructure equipment701and the communications device702each comprise a transceiver (or transceiver circuitry)701.1,702.1, and a controller (or controller circuitry)701.2,702.2. Each of the controllers701.2,702.2may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc.

The transceiver circuitry701.1and the controller circuitry701.2of the infrastructure equipment701are configured in combination to receive710assistance information from the communications device702, to identify720, based on the received assistance information, that a backup configuration should be updated to indicate one or more others of the spot beams, the one or more others of the spot beams being backups to the first spot beam in case of beam failure of the first spot beam, and to transmit730a backup beam reconfiguration message to the communications device702, the backup beam configuration message comprising an indication of the updated backup configuration. In some arrangements of embodiments of the present technique, the assistance information may comprise a location report, the location report indicating a geographical area in which the communications device is located. In other arrangements of embodiments of the present technique, the assistance information may comprise measurement information relating to measurements performed by the communications device, or to reference signals transmitted by the communications device.

In NR BFR, the UE is configured via RRC with RACH resources and candidate beams in the BeamFailureRecoveryConfig Information Element (IE) for beam failure recovery in case of beam failure detection. Since UE location reporting is to be introduced in NTN, every time the network receives such location information of the UE, it is able to evaluate whether or not the BeamFailureRecoveryConfig IE needs to be re-configured according to the UE's current location, or according to the satellite ephemeris, satellite constellation or beam distribution of the non-terrestrial network part. In other words, the identifying that the backup configuration should be updated is further based on one or more of ephemeris information of the non-terrestrial network part, a satellite constellation comprising the non-terrestrial network part, and a beam distribution of one or more of the plurality of spot beams transmitted by the non-terrestrial network part. Such a timely reconfiguration could accelerate beam failure recovery procedures once beam failure happens, thus allowing for more efficient systems where there are lower latencies and wasted transmissions on account of beam failures. An example of such a process is shown byFIG.8.

The RACH procedure is used to set up uplink synchronisation of the UE with the network, and in the context of legacy beam recovery procedures, the RACH procedure is also used to tell the network which candidate beam is being selected for recovery. However in NTN, uplink synchronisation should not be a problem if the UE knows the satellite ephemeris and hence could calculate timing advances to any satellite cell/beam. However, in addition to performing this, the UE will need to notify the network which candidate beam is being selected as the new serving beam. In other words, the communications device is configured to detect, on the first spot beam satisfying a beam failure condition, beam failure of the first spot beam, to select one of the one or more others of the spot beams to use for transmitting signals to and receiving signals from the one of the base station and the non-terrestrial network part, to provide an indication to the one of the base station and the non-terrestrial network part of the selected one of the one or more others of the spot beams, and to transmit signals to the one of the base station and the non-terrestrial network part in using the selected one of the one or more others of the spot beams.

In some arrangements of embodiments of the present technique, the network will reserve a set of resources (time, frequency or e.g. configured grant, PUCCH/PUSCH resources) for the UE to employ during the beam failure recovery procedure. Each set of resources will be associated with a specific beam (e.g. backup beam). This means that from the resources, the network can identify which beam is being used. In other words, each of the spot beams is associated with a reserved set of radio resources of the wireless access interface, the reserved set of radio resources associated with each of the spot beams being unique to that spot beam. The infrastructure equipment may be configured to transmit an indication of the reserved set of radio resources associated with each of the one or more others of the spot beams to the communications device. The infrastructure equipment is configured to receive signals (e.g. representing data) from the communications device in the reserved set of radio resources of one of the one or more others of the spot beams instead of the first spot beam, to determine, based on the reserved set of radio resources in which the signals are received, that the communications device has detected beam failure of the first spot beam, and to transmit an acknowledgement to the communications device, the acknowledgement indicating that the signals have been successfully received by the infrastructure equipment via the one of the one or more others of the spot beams Here, the communications device is configured to detect, on the first spot beam satisfying a beam failure condition, beam failure of the first spot beam, to select one of the one or more others of the spot beams to use for transmitting signals to and receiving signals from the one of the base station and the non-terrestrial network part, wherein each of the one or more others of the spot beams is associated with a reserved set of resources of the wireless access interface, the reserved set of radio resources associated with each of the one or more others of the spot beams being unique to that spot beam, and to transmit signals (e.g. representing data) to the one of the base station and the non-terrestrial network part in the reserved set of resources of the selected one of the one or more others of the spot beams. The infrastructure equipment is then able to receive and decode these signals (which may represent data) and on doing so, identify the backup beam selected by the communications device. Such a procedure is shown byFIG.9. The beam failure condition may comprise a determination by the communications device that a measured characteristic of signals received using the first spot beam falls below a predetermined threshold. The measured characteristic may be at least one of a relative quality of the signals, a power with which the signals are received, and an error rate of the received signals.

This association will be either broadcast in system information or transmitted via dedicated signalling for a group of UEs or single UE. In other words, the indication of the reserved set of radio resources associated with each of the one or more others of the spot beams may be in system information broadcasted by the infrastructure equipment, or alternatively, the indication of the reserved set of radio resources associated with each of the one or more others of the spot beams may be transmitted to the communications device by the infrastructure equipment via dedicated signalling. If transmitted via broadcasting, the resources will be shared by all the UEs in the network. On the other hand, if transmitted via dedicated signalling, the resources could be shared among a specific group of UEs or a single UE, depending on network configurations.

When beam failure is detected, the UE will first find the best beam (for example, the beam with the strongest RSRP amongst its backup beams) and select the resources associated with that beam to transmit data (i.e. the signals) to network. In other words, the selected one of the one or more others of the spot beams is selected based on the selected spot beam having a highest reference signal received power from among the one or more others of the spot beams. After the network receives the data from that UE, it can figure out that beam failure has occurred and the beam through which it receives data is the selected beam for recovery. The network can then send the re-configuration message if necessary or send downlink data if there is any to send to the UE afterwards. After the UE receives the reconfiguration message or a DCI, the beam failure recovery procedure is considered complete.

It may be the case that the UE sends data but doesn't receive the acknowledgement from the network, as for example, a collision may happen on the sending of either the data or the acknowledgement. Based on the network configurations, which may for example be a pre-defined timer or a predetermined maximum collision number, the UE can fall-back to legacy BFR, e.g. that RACH based BFR procedure as described above. In other words, the communications device is configured to determine whether an acknowledgement has been received from the one of the base station and the non-terrestrial network part after the communications device has transmitted the signals to the one of the base station and the non-terrestrial network part in the reserved set of resources of the selected one of the one or more others of the spot beams, the acknowledgement indicating that the signals have been successfully received by the one of the base station and the non-terrestrial network part via the one of the one or more others of the spot beams, and to perform, if the communications device determines that the acknowledgement has not been received, a legacy beam failure recovery process.

It should be appreciated by those skilled in the art that the UE may not always have knowledge of the spot beams explicitly, or the spot beams themselves may not actually be directly visible to the UE. Thus, in embodiments of the present technique, wherever reference is made to a spot beam or spot beams from the point of view of communications devices, this should be understood to cover both the spot beam(s) themselves, or radio resources of the wireless access interface covered by or associated with the spot beam(s).

In some arrangements of embodiments of the present technique, the coverage region of the spot beam varies over time in accordance with a motion of the non-terrestrial network part with respect to the surface of the Earth. Alternatively, in some arrangements of embodiments of the present technique, a trajectory of the non-terrestrial network part is such that the coverage region of the spot beam is substantially constant over a time period.

In some arrangements of embodiments of the present technique, the infrastructure equipment is the non-terrestrial network part. Alternatively, the infrastructure equipment may be the base station. The non-terrestrial network part may comprise a satellite, an airborne vehicle or an airborne platform. The airborne platform may for example be a High Altitude Pseudo Satellite (HAPS), also termed High Altitude Platform Station, which are positioned typically in the stratosphere at an altitude of above 20 km. An example of a HAPS may be a station tethered to an aircraft or a balloon.

In some arrangements of embodiments of the present technique, the communications device is a user equipment. Alternatively, the communications device may act as a relay node for one or more user equipment, each of the one or more user equipment being in one of an RRC connected mode, an RRC idle state or an RRC inactive state.

As described above, each of the spot beams is (or alternatively, may be referred to as) a different one of a set of Transmission Configuration Indication (TCI) states.

Flow Chart Representation

FIG.10shows a flow diagram illustrating a method of operating an infrastructure equipment forming part of a wireless communications network according to embodiments of the present technique. The wireless communications network comprises a base station and a non-terrestrial network part, the non-terrestrial network part transmitting a plurality of spot beams to provide a wireless access interface for transmitting signals to and receiving signals representing data from a communications device within a coverage region formed by a first of the spot beams.

The method begins in step S101. The method comprises, in step S102, receiving assistance information from the communications device. In step S103, the process comprises identifying, based on the received assistance information, that a backup configuration should be updated to indicate one or more others of the spot beams, the one or more others of the spot beams being backups to the first spot beam in case of beam failure of the first spot beam. The method then advances to step S104, which comprises transmitting a backup beam reconfiguration message to the communications device, the backup beam configuration message comprising an indication of the updated backup configuration. The process ends in step S105.

Those skilled in the art would appreciate that the method shown byFIG.10may be adapted in accordance with embodiments of the present technique. For example, other intermediate steps may be included in the method, or the steps may be performed in any logical order.

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:

Paragraph 1. A method for operating an infrastructure equipment forming part of a wireless communications network, the wireless communications network comprising a base station and a non-terrestrial network part, the non-terrestrial network part transmitting a plurality of spot beams to provide a wireless access interface for transmitting signals to and receiving signals representing data from a communications device within a coverage region formed by a first of the spot beams, the method comprisingreceiving assistance information from the communications device,identifying, based on the received assistance information, that a backup configuration should be updated to indicate one or more others of the spot beams, the one or more others of the spot beams being backups to the first spot beam in case of beam failure of the first spot beam, andtransmitting a backup beam reconfiguration message to the communications device, the backup beam configuration message comprising an indication of the updated backup configuration.

Paragraph 2. A method according to Paragraph 1, wherein the assistance information comprises a location report, the location report indicating a geographical area in which the communications device is located.

Paragraph 3. A method according to Paragraph 2, wherein the identifying that the backup configuration should be updated is further based on one or more of ephemeris information of the non-terrestrial network part, a satellite constellation comprising the non-terrestrial network part, and a beam distribution of one or more of the plurality of spot beams transmitted by the non-terrestrial network part.

Paragraph 4. A method according to any of Paragraphs 1 to 3, wherein each of the spot beams is associated with a reserved set of radio resources of the wireless access interface, the reserved set of radio resources associated with each of the spot beams being unique to that spot beam.

Paragraph 5. A method according to Paragraph 4, comprisingtransmitting an indication of the reserved set of radio resources associated with each of the one or more others of the spot beams to the communications device.

Paragraph 6. A method according to Paragraph 5, wherein the indication of the reserved set of radio resources associated with each of the one or more others of the spot beams is in system information broadcasted by the infrastructure equipment.

Paragraph 7. A method according to Paragraph 5 or Paragraph 6, wherein the indication of the reserved set of radio resources associated with each of the one or more others of the spot beams is transmitted to the communications device by the infrastructure equipment via dedicated signalling.

Paragraph 8. A method according to any of Paragraphs 5 to 7, comprisingreceiving signals from the communications device in the reserved set of radio resources associated with one of the one or more others of the spot beams instead of the first spot beam,determining, based on the reserved set of radio resources in which the signals are received, that the communications device has detected beam failure of the first spot beam, andtransmitting an acknowledgement to the communications device, the acknowledgement indicating that the signals have been successfully received by the infrastructure equipment via the one of the one or more others of the spot beams.

Paragraph 9. A method according to any of Paragraphs 1 to 8, wherein the coverage region formed by the first spot beam varies over time in accordance with a motion of the non-terrestrial network part with respect to the surface of the Earth.

Paragraph 10. A method according to any of Paragraphs 1 to 9, whereina trajectory of the non-terrestrial network part is such that the coverage region formed by the first spot beam is substantially constant over a time period.

Paragraph 11. A method according to any of Paragraphs 1 to 10, wherein the infrastructure equipment is the non-terrestrial network part.

Paragraph 12. A method according to any of Paragraphs 1 to 11, wherein the infrastructure equipment is the base station.

Paragraph 13. A method according to any of Paragraphs 1 to 12, wherein the non-terrestrial network part comprises a satellite, an airborne vehicle or an airborne platform.

Paragraph 14. A method according to any of Paragraphs 1 to 13, wherein the communications device is a user equipment.

Paragraph 15. A method according to any of Paragraphs 1 to 14, wherein the communications device is acting as a relay node for one or more user equipment, each of the one or more user equipment being in one of an RRC connected mode, an RRC idle state or an RRC inactive state.

Paragraph 16. A method according to any of Paragraphs 1 to 15, wherein each of the spot beams is a different one of a set of Transmission Configuration Indication, TCI, states.

Paragraph 17. A method for operating a communications device in a wireless communications network, the wireless communications network comprising a base station and a non-terrestrial network part, the non-terrestrial network part transmitting a plurality of spot beams to provide a wireless access interface for transmitting signals to and receiving signals representing data from a communications device within a coverage region formed by a first of the spot beams, the method comprisingtransmitting assistance information to one of the base station and the non-terrestrial network part, andreceiving a backup beam reconfiguration message from the one of the base station and the non-terrestrial network part, the backup beam configuration message comprising an indication of a backup configuration that has been updated by the one of the base station and the non-terrestrial network part based on the transmitted assistance information to indicate one or more others of the spot beams, the one or more others of the spot beams being backups to the first spot beam in case of beam failure of the first spot beam.

Paragraph 18. A method according to Paragraph 17, wherein the assistance information comprises a location report, the location report indicating a geographical area in which the communications device is located.

Paragraph 19. A method according to Paragraph 17 or Paragraph 18, comprisingdetecting, on the first spot beam satisfying a beam failure condition, beam failure of the first spot beam,selecting one of the one or more others of the spot beams to use for transmitting signals to and receiving signals from the one of the base station and the non-terrestrial network part,providing an indication to the one of the base station and the non-terrestrial network part of the selected one of the one or more others of the spot beams, andtransmitting signals to the one of the base station and the non-terrestrial network part in using the selected one of the one or more others of the spot beams.

Paragraph 20. A method according to any of Paragraphs 17 to 19, comprisingdetecting, on the first spot beam satisfying a beam failure condition, beam failure of the first spot beam,selecting one of the one or more others of the spot beams to use for transmitting signals to and receiving signals from the one of the base station and the non-terrestrial network part, wherein each of the one or more others of the spot beams is associated with a reserved set of resources of the wireless access interface, the reserved set of radio resources associated with each of the one or more others of the spot beams being unique to that spot beam, andtransmitting signals to the one of the base station and the non-terrestrial network part in the reserved set of resources associated with the selected one of the one or more others of the spot beams.

Paragraph 21. A method according to Paragraph 20, where an indication of the reserved set of radio resources associated with each of the one or more others of the spot beams is received by the communications device in system information broadcasted by the one of the base station and the non-terrestrial network part.

Paragraph 22. A method according to Paragraph 20 or Paragraph 21, wherein an indication of the reserved set of radio resources associated with each of the one or more others of the spot beams is received by the communications device via dedicated signalling from the one of the base station and the non-terrestrial network part.

Paragraph 23. A method according to any of Paragraphs 19 to 22, wherein the beam failure condition comprises a determination by the communications device that a measured characteristic of signals received using the first spot beam falls below a predetermined threshold.

Paragraph 24. A method according to Paragraph 23, wherein the measured characteristic is at least one of a relative quality of the signals, a power with which the signals are received, and an error rate of the received signals.

Paragraph 25. A method according to any of Paragraphs 19 to 24, wherein the selected one of the one or more others of the spot beams is selected based on the selected spot beam having a highest reference signal received power from among the one or more others of the spot beams.

Paragraph 26. A method according to any of Paragraphs 19 to 25, comprisingdetermining whether an acknowledgement has been received from the one of the base station and the non-terrestrial network part after the communications device has transmitted the signals to the one of the base station and the non-terrestrial network part using the selected one of the one or more others of the spot beams, the acknowledgement indicating that the signals have been successfully received by the one of the base station and the non-terrestrial network part via the one of the one or more others of the spot beams, andperforming, if the communications device determines that the acknowledgement has not been received, a legacy beam failure recovery process.

Paragraph 27. An infrastructure equipment forming part of a wireless communications network, the wireless communications network comprising a base station and a non-terrestrial network part, the non-terrestrial network part transmitting a plurality of spot beams to provide a wireless access interface for transmitting signals to and receiving signals representing data from a communications device within a coverage region formed by a first of the spot beams, wherein the infrastructure equipment comprises transceiver circuitry and controller circuitry configured in combinationto receive assistance information from the communications device,to identify, based on the received assistance information, that a backup configuration should be updated to indicate one or more others of the spot beams, the one or more others of the spot beams being backups to the first spot beam in case of beam failure of the first spot beam, andto transmit a backup beam reconfiguration message to the communications device, the backup beam configuration message comprising an indication of the updated backup configuration.

Paragraph 28. Circuitry for an infrastructure equipment forming part of a wireless communications network, the wireless communications network comprising a base station and a non-terrestrial network part, the non-terrestrial network part transmitting a plurality of spot beams to provide a wireless access interface for transmitting signals to and receiving signals representing data from a communications device within a coverage region formed by a first of the spot beams, wherein the infrastructure equipment comprises transceiver circuitry and controller circuitry configured in combinationto receive assistance information from the communications device,to identify, based on the received assistance information, that a backup configuration should be updated to indicate one or more others of the spot beams, the one or more others of the spot beams being backups to the first spot beam in case of beam failure of the first spot beam, andto transmit a backup beam reconfiguration message to the communications device, the backup beam configuration message comprising an indication of the updated backup configuration.

Paragraph 29. A communications device configured to operate in a wireless communications network, the wireless communications network comprising a base station and a non-terrestrial network part, the non-terrestrial network part transmitting a plurality of spot beams to provide a wireless access interface for transmitting signals to and receiving signals representing data from a communications device within a coverage region formed by a first of the spot beams, wherein the communications device comprises transceiver circuitry and controller circuitry configured in combinationto transmit assistance information to one of the base station and the non-terrestrial network part, andto receive a backup beam reconfiguration message from the one of the base station and the non-terrestrial network part, the backup beam configuration message comprising an indication of a backup configuration that has been updated by the one of the base station and the non-terrestrial network part based on the transmitted assistance information to indicate one or more others of the spot beams, the one or more others of the spot beams being backups to the first spot beam in case of beam failure of the first spot beam.

Paragraph 30. Circuitry for a communications device configured to operate in a wireless communications network, the wireless communications network comprising a base station and a non-terrestrial network part, the non-terrestrial network part transmitting a plurality of spot beams to provide a wireless access interface for transmitting signals to and receiving signals representing data from a communications device within a coverage region formed by a first of the spot beams, wherein the communications device comprises transceiver circuitry and controller circuitry configured in combinationto transmit assistance information to one of the base station and the non-terrestrial network part, andto receive a backup beam reconfiguration message from the one of the base station and the non-terrestrial network part, the backup beam configuration message comprising an indication of a backup configuration that has been updated by the one of the base station and the non-terrestrial network part based on the transmitted assistance information to indicate one or more others of the spot beams, the one or more others of the spot beams being backups to the first spot beam in case of beam failure of the first spot beam.

REFERENCES