Patent Description:
The present disclosure claims the Paris Convention priority to <CIT>.

Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.

Third and fourth generation mobile telecommunication systems, such as those based on the third generation partnership project (3GPP) defined UMTS and Long Term Evolution (LTE) architectures, are able to support more sophisticated services than simple voice and messaging services offered by previous generations of mobile telecommunication systems.

Future wireless communications networks will therefore be expected to routinely and efficiently support communications with a wider range of devices associated with a wider range of data traffic profiles and types than current systems are optimised to support. For example, it is expected that future wireless communications networks will 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 "Internet of Things" (IoT), and may typically be associated with the transmission of relatively small amounts of data with relatively high latency tolerance.

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

One example area of current interest in this regard includes so-called "non-terrestrial networks", or NTN for short. The 3GPP has proposed in Release <NUM> 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 <MAT>.

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.

Although NTN networks can provide improved coverage for communications devices, particularly in remote areas, a nature of communications resulting from, for example, a decrease in an amount of time which communications devices spend in a coverage area of an NTN infrastructure equipment can create new challenges that need to be addressed.

<CIT>, discusses slot offset determination for non-terrestrial networks.

According to one aspect, there is described a method of operating a communications device to transmit or to receive via a wireless communications network including non-terrestrial, NTN, infrastructure equipment. The communications device identifies a first in-coverage period during which the communications device can transmit signals to or receive signals from a first NTN infrastructure equipment, the first NTN infrastructure equipment being either carried by a first aerial vehicle or relayed via the first aerial vehicle to or from the first NTN infrastructure equipment as the aerial vehicle passes over the communications device. The communications device identifies a second in-coverage period during which the communications device can transmit signals to or receive signals from either the first NTN infrastructure equipment or a second NTN infrastructure equipment, the second NTN infrastructure equipment being either carried by a second aerial vehicle or the transmitted or the received signal are relayed via the second aerial vehicle to or from the second NTN infrastructure equipment as the second aerial vehicle passes over the communications device. The communications device transmits uplink data to the wireless communications network by adapting a transmission of the uplink data to include at least part of the second in-coverage period, based on a length of time required to transmit the uplink data and a start time at which the uplink data can be transmitted in the first in-coverage period with respect to an end of the first in-coverage period, or alternatively, the communications device receives downlink data from the wireless communications network by adapting a reception of the downlink data to include at least part of the second in-coverage period, having been transmitted at least partly in the second in-coverage period, based on a length of time required to receive the downlink data and a start time at which the downlink data can be received in the first in-coverage period with respect to an end of the first in-coverage period.

Example embodiments can provide a communications device, which is identifies that an uplink transmission or a downlink reception has a time duration which will exceed a time for which the communications device remains in a current in-coverage period but can be continued in a subsequent in-coverage period provided by either the same NTN infrastructure equipment or another NTN infrastructure equipment. Example embodiments can find application with repeated transmission/received of the same transport block to improve a likelihood of correct communication, which can exceed a remaining duration of an in-coverage period in which the transmission/reception is scheduled.

The network <NUM> includes a plurality of base stations <NUM> connected to a core network part <NUM>. Each base station provides a coverage area <NUM> (e.g. a cell) within which data can be communicated to and from communications devices <NUM>. Data is transmitted from the base stations <NUM> to the communications devices <NUM> within their respective coverage areas <NUM> via a radio downlink. Data is transmitted from the communications devices <NUM> to the base stations <NUM> via a radio uplink. The core network part <NUM> routes data to and from the communications devices <NUM> via the respective base stations <NUM> and provides functions such as authentication, mobility management, charging and so on. Communications devices may also be referred to as mobile stations, user equipment (UE), user terminals, mobile radios, terminal devices, and so forth. Base stations, which are an example of network infrastructure equipment / network access nodes, may also be referred to as transceiver stations / nodeBs / e-nodeBs (eNB), g-nodeBs (gNB) and so forth. In this regard, different terminology is often associated with different generations of wireless telecommunications systems for elements providing broadly comparable functionality. However, example embodiments of the disclosure may be equally implemented in different generations of wireless telecommunications systems such as <NUM> or new radio as explained below, 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.

<FIG> is a schematic diagram illustrating a network architecture for a new RAT wireless communications network / system <NUM> based on previously proposed approaches which may also be adapted to provide functionality in accordance with embodiments of the disclosure described herein. The new RAT network <NUM> represented in <FIG> comprises a first communication cell <NUM> and a second communication cell <NUM>. Each communication cell <NUM>, <NUM>, comprises a controlling node (centralised unit) <NUM>, <NUM> in communication with a core network component <NUM> over a respective wired or wireless link <NUM>, <NUM>. The respective controlling nodes <NUM>, <NUM> are also each in communication with a plurality of distributed units (radio access nodes / remote transmission and reception points (TRPs)) <NUM>, <NUM> in their respective cells. Again, these communications may be over respective wired or wireless links. The distributed units (DUs) <NUM>, <NUM> are responsible for providing the radio access interface for communications devices connected to the network. Each distributed unit <NUM>, <NUM> has a coverage area (radio access footprint) <NUM>, <NUM> where the sum of the coverage areas of the distributed units under the control of a controlling node together define the coverage of the respective communication cells <NUM>, <NUM>. Each distributed unit <NUM>, <NUM> includes transceiver circuitry for transmission and reception of wireless signals and processor circuitry configured to control the respective distributed units <NUM>, <NUM>.

A communications device or UE <NUM> is represented in <FIG> within the coverage area of the first communication cell <NUM>. This communications device <NUM> may thus exchange signalling with the first controlling node <NUM> in the first communication cell via one of the distributed units <NUM> associated with the first communication cell <NUM>. In some cases communications for a given communications device are routed through only one of the distributed units, but it will be appreciated in some other implementations communications associated with a given communications device may be routed through more than one distributed unit, for example in a soft handover scenario and other scenarios.

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

A more detailed illustration of a communications device <NUM> and an example network infrastructure equipment <NUM>, which may be thought of as an eNB or a gNB <NUM> or a combination of a controlling node <NUM> and TRP <NUM>, is presented in <FIG>. As shown in <FIG>, the communications device <NUM> is shown to transmit uplink data to the infrastructure equipment <NUM> of a wireless access interface as illustrated generally by an arrow <NUM>. The UE <NUM> is shown to receive downlink data transmitted by the infrastructure equipment <NUM> via resources of the wireless access interface as illustrated generally by an arrow <NUM>. As with <FIG> and <FIG>, the infrastructure equipment <NUM> is connected to a core network <NUM> (which may correspond to the core network <NUM> of <FIG> or the core network <NUM> of <FIG>) via an interface <NUM> to a controller <NUM> of the infrastructure equipment <NUM>. The infrastructure equipment <NUM> may additionally be connected to other similar infrastructure equipment by means of an inter-radio access network node interface, not shown on <FIG>.

The infrastructure equipment <NUM> includes a receiver <NUM> connected to an antenna <NUM> and a transmitter <NUM> connected to the antenna <NUM>. Correspondingly, the communications device <NUM> includes a controller <NUM> connected to a receiver <NUM> which receives signals from an antenna <NUM> and a transmitter <NUM> also connected to the antenna <NUM>.

The controller <NUM> is configured to control the infrastructure equipment <NUM> and may comprise processor circuitry which may in turn comprise various sub-units / sub-circuits for providing functionality as explained further herein. These sub-units may be implemented as discrete hardware elements or as appropriately configured functions of the processor circuitry. Thus the controller <NUM> may comprise circuitry which is suitably configured / programmed to provide the desired functionality using conventional programming / configuration techniques for equipment in wireless telecommunications systems. The transmitter <NUM> and the receiver <NUM> may comprise signal processing and radio frequency filters, amplifiers and circuitry in accordance with conventional arrangements. The transmitter <NUM>, the receiver <NUM> and the controller <NUM> are schematically shown in <FIG> as separate elements for ease of representation. However, it will be appreciated that the functionality of these elements can be provided in various different ways, for example using one or more suitably programmed programmable computer(s), or one or more suitably configured application-specific integrated circuit(s) / circuitry / chip(s) / chipset(s). As will be appreciated the infrastructure equipment <NUM> will in general comprise various other elements associated with its operating functionality.

Correspondingly, the controller <NUM> of the communications device <NUM> is configured to control the transmitter <NUM> and the receiver <NUM> and may comprise processor circuitry which may in turn comprise various sub-units / sub-circuits for providing functionality as explained further herein. These sub-units may be implemented as discrete hardware elements or as appropriately configured functions of the processor circuitry. Thus the controller <NUM> may comprise circuitry which is suitably configured / programmed to provide the desired functionality using conventional programming / configuration techniques for equipment in wireless telecommunications systems. Likewise, the transmitter <NUM> and the receiver <NUM> may comprise signal processing and radio frequency filters, amplifiers and circuitry in accordance with conventional arrangements. The transmitter <NUM>, receiver <NUM> and controller <NUM> are schematically shown in <FIG> as separate elements for ease of representation. However, it will be appreciated that the functionality of these elements can be provided in various different ways, for example using one or more suitably programmed programmable computer(s), or one or more suitably configured application-specific integrated circuit(s) / circuitry / chip(s) / chipset(s). As will be appreciated the communications device <NUM> will in general comprise various other elements associated with its operating functionality, for example a power source, user interface, and so forth, but these are not shown in <FIG> in the interests of simplicity.

The controllers <NUM>, <NUM> may be configured to carry out instructions which are stored on a computer readable medium, such as a non-volatile memory. The processing steps described herein may be carried out by, for example, a microprocessor in conjunction with a random access memory, which may be non-volatile memory, operating according to instructions stored on a computer readable medium.

An overview of NR-NTN can be found in [<NUM>], and much of the following wording, along with <FIG>, has been reproduced from that document as a way of background.

In an NTN, an aerial vehicle (such as a satellite or aerial platform) may allow a connection of a communications device and a ground station (which may be referred to herein as an NTN gateway). In the present disclosure, the term aerial vehicle is used to refer to a space vehicle, aerial platform, or satellite, or any other entity which moves relative to a communications device and is configured to communicate with the communications device. In particular, an aerial vehicle may be in some embodiments a low earth orbit (LEO) satellite, a medium earth orbit (MEO) satellite, a high altitude platform system (HAPS), a balloon or a drone for example. As will be explained below, the aerial vehicle is configured to communicate with the communications device and the ground station of a terrestrial network by means of non-communications circuitry of the aerial vehicle.

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:.

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 <NUM> system is expected for at least the following verticals: transport, Public Safety, Media and Entertainment, eHealth, Energy, Agriculture, Finance and Automotive. It should also be noted that the same NTN benefits apply to <NUM> and/or LTE technologies and that while NR is sometimes referred to in the present disclosure, the teachings and techniques presented herein are equally applicable to <NUM> and/or LTE.

<FIG> schematically shows an example of a wireless communications system <NUM> which may be configured to operate in accordance with embodiments of the present disclosure. The wireless communications system <NUM> in this example is based broadly around an LTE-type or NR-type architecture.

Many aspects of the operation of the wireless communications system / network <NUM> are known and understood and are not described here in detail in the interest of brevity. Operational aspects of the wireless communications system <NUM> which 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 NR standards.

The wireless communications system <NUM> comprises a core network part <NUM> (which may be a <NUM> core network or a <NUM> core network) in communicative connection with a radio network part. The radio network part <NUM> comprises a base station <NUM> connected to a ground station (or NTN gateway) <NUM>. The radio network part <NUM> may perform the functions of a base station <NUM> of <FIG>, or may perform the functions of a controlling node and TRP of <FIG>. In some embodiments, the base station <NUM> is an example of a non-terrestrial infrastructure equipment as explained below.

An aerial vehicle <NUM> includes communications circuitry <NUM>. In some embodiments, the communications circuitry <NUM> may be non-terrestrial infrastructure equipment which is mounted on, and/or within the aerial vehicle <NUM> as explained below. The communications circuitry <NUM> communicates via the ground station <NUM> with the base station <NUM> via a wireless communications link <NUM>.

The communications circuitry <NUM> may communicate with a communications device <NUM>, located within a cell <NUM>, by means of a wireless access interface provided by a wireless communications link <NUM>. For example, the cell <NUM> may correspond to the coverage area of a spot beam generated by the communications circuitry <NUM>. The boundary of the cell <NUM> may depend on an altitude of the aerial vehicle <NUM> and a configuration of one or more antennas of the communications circuitry <NUM> by which the aerial vehicle transmits and receives signals on the wireless access interface. The spot beam may be an "earth fixed beam" which illuminates a geographic area on a surface of the earth for a pre-defined period of time. After the pre-defined period of time, the earth fixed beam may switch to serving a different geographic area on the surface of the earth. In such cases, the communications device <NUM> may be made aware of when the pre-defined period of time ends. In this way, the communications device <NUM> may determine to switch from being served by the aerial vehicle <NUM> to being served by another, different aerial vehicle (not shown) at the end of the pre-determined time period. Alternatively, the spot beam may be an "earth moving beam" which illuminates a constantly changing geographic area on the surface of the earth. In this case, the communications device <NUM> may determine to switch from being served by the aerial vehicle <NUM> to being served by the other aerial vehicle based on decision criteria. For example, the communications device <NUM> may determine to switch from being served by the aerial vehicle <NUM> to being served by the other aerial vehicle by determining that a distance between the communications device <NUM> and the aerial vehicle <NUM> is greater than a pre-defined distance. Alternatively, the communications device <NUM> may determine to switch from being served by the aerial vehicle <NUM> to being served by the other aerial vehicle by determining that the distance between the communications device <NUM> and the aerial vehicle <NUM> is greater than a distance between the communications device <NUM> and the other aerial vehicle.

The aerial vehicle <NUM> may be a satellite in an orbit with respect to the Earth. According to example embodiments, the satellite may be in a non-geostationary orbit (NGSO), so that the aerial vehicle <NUM> moves with respect to a fixed point on the Earth's surface. An example of an NGSO is an LEO, in which the satellite may complete an orbit of the Earth relatively quickly, thus providing moving cell coverage.

In <FIG>, the ground station <NUM> is connected to the communications circuitry <NUM> by means of a wireless communications link <NUM>. The communications circuitry <NUM> receives signals representing downlink data transmitted by the radio access network <NUM> on the wireless communications link <NUM> and, based on the received signals, transmits signals representing the downlink data via the wireless communications link <NUM> providing the wireless access interface for the communications device <NUM>. Similarly, the communications circuitry <NUM> receives signals representing uplink data transmitted by the communications device <NUM> via the wireless access interface comprising the wireless communications link <NUM> and transmits signals representing the uplink data to the ground station <NUM> on the wireless communications link <NUM>. The wireless communications links <NUM>, <NUM> may operate at a same frequency, or may operate at different frequencies.

The extent to which the communications circuitry <NUM> processes the received signals may depend upon a processing capability of the communications circuitry <NUM>. For example, the communications circuitry <NUM> may receive signals representing the downlink data on the wireless communication link <NUM>, 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 <NUM>.

<FIG> illustrates an example of an NTN architecture based on communications circuitry of an aerial vehicle operating in a transparent manner, meaning that a signal received from the communications device at the aerial vehicle is forwarded (to the communications device, to a ground station on Earth or to another aerial vehicle) with only frequency conversion and/or amplification. A wireless access interface (such as a <NUM> Uu interface) may be generated at a base station located on the Earth, and connects the base station (gNB, in the example of <FIG>) and the communications device (UE). In such embodiments, the base station may be regarded as a non-terrestrial infrastructure equipment, and communications are relayed between the non-terrestrial infrastructure equipment and the communications device <NUM>.

Alternatively, the communications circuitry <NUM> of the aerial vehicle <NUM> may be configured to decode the signals representing the downlink data received on the wireless communication link <NUM> 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 <NUM>.

The communications circuitry <NUM> may be configured to perform some of the functionality conventionally carried out by a base station (e.g. a gNodeB or an eNode B), such as base station <NUM> of <FIG>. 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 communications circuitry <NUM> partially implementing some of the functions of a base station. In such embodiments, the communications circuitry <NUM> of the aerial vehicle <NUM> may be regarded as a non-terrestrial infrastructure equipment.

In such arrangements, there may be a physical (e.g. wired, or fibre optic) connection on board the aerial vehicle <NUM> which provides the coupling between the circuitry of the communications circuitry <NUM> which implements base station functionality and a transceiver of the communications circuitry <NUM> which is configured communicate with the communications device <NUM> and the ground station <NUM>. In such arrangements, a wireless communications feeder link between the communications circuitry <NUM> and the ground station <NUM> may provide connectivity between the communications circuitry <NUM> and the core network part <NUM>. In such arrangements, the base station <NUM> may not be present.

<FIG> illustrates an example of an NTN architecture based on communications circuitry equipment of an aerial vehicle implementing at least some base station functionality. In this example NTN, the communications circuitry <NUM> is an example of non-terrestrial infrastructure equipment. The communications circuitry <NUM> generates the wireless access interface (e.g. the Uu interface) which connects the aerial vehicle and the communications device. For example, the communications circuitry may decode a received signal, and encode and generate a transmitted signal. As such, the non-communications circuitry may include some or all of the functionality of a base station (such as a gNodeB or eNodeB). A further connection between the communications circuitry <NUM> and a ground station (such as an NTN gateway) may be by means of a separate wireless access interface, and may form part of a connection between the communications circuitry <NUM> and a core network.

In some cases, the communications device <NUM> shown in <FIG> may be configured to act as a relay node. That is, it may provide connectivity to one or more terminal devices such as the terminal device <NUM>. When acting as a relay node, the communications device <NUM> transmits and receives data to and from the terminal device <NUM>, and relays it, via the aerial vehicle <NUM> to the ground station <NUM>. The communications device <NUM>, acting as a relay node, may thus provide connectivity to the core network part <NUM> for terminal devices which are within a transmission range of the communications device <NUM>.

It will be apparent to those skilled in the art that many scenarios can be envisaged in which the combination of the communications device <NUM> and the aerial vehicle <NUM> can provide enhanced service to end users. For example, the communications device <NUM> 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 communications device <NUM> acting as a relay, which communicates with the communications circuitry <NUM>.

In some cases, as shown in <FIG>, the communications circuitry <NUM> of the aerial vehicle <NUM> may comprise a plurality of antennae configured to generate a corresponding plurality of spot beams. Each of the plurality of spot beams may illuminate a different area of the Earth's surface to provide a plurality of cells <NUM>, 348a each corresponding to a coverage area of one of the plurality of spot beams. The aerial vehicle <NUM> may communicate with a communications device (such as communications device <NUM>) located in any one of the plurality of cells <NUM>, 348a provided by the plurality of spot beams by means of a wireless access interface provided by a wireless communications link (such as wireless communications link <NUM>) to the communications device. The boundary of each of the plurality of cells may depend on an altitude of the aerial vehicle <NUM> and a configuration of the plurality of antennae of the aerial vehicle <NUM> by which the aerial vehicle <NUM> transmits and receives signals on the wireless access interface. As shown in <FIG>, the communications device <NUM> may move from the coverage area <NUM> of a first beam generated by the communications circuitry <NUM> carried by the aerial vehicle <NUM> to the coverage area 348a of a second beam generated by the communications circuitry <NUM> carried by the aerial vehicle <NUM>. In other words, the communications device <NUM> may be handed over from the coverage area <NUM> of the first beam to the coverage area 348a of the second beam.

In some cases, as shown in <FIG>, the communications device <NUM> may be configured to receive coverage from a plurality of aerial vehicles <NUM>, <NUM> each including respective communications circuitry <NUM>, <NUM>. The communications circuitry <NUM> of a first <NUM> of the plurality of aerial vehicles may generate a first beam defining a coverage area <NUM>. The communications circuitry of a second <NUM> of the plurality of aerial vehicles may generate a second beam defining a coverage area 348b. As shown in <FIG>, the communications device <NUM> may move from the coverage area <NUM> of the first beam generated by the first aerial vehicle <NUM> to the coverage area 348b of the second beam generated by the second aerial vehicle <NUM>. In other words, the communications device <NUM> may be handed over from the coverage area <NUM> of the first beam to the coverage area 348b of the second beam.

It will be appreciated that references to the term "beam" may be taken to mean "cell".

In such configurations, the communications device <NUM> may be handed over because the communications device <NUM> leaves the coverage area <NUM> of the first beam and enters the coverage area <NUM> of the second beam as a result of motion of the aerial vehicle (as shown in <FIG> and <FIG>) and/or as a result of motion of the communications device <NUM> itself.

In the present disclosure, the reference numeral "<NUM>" is to be taken to mean either coverage area 348a or coverage area 348b and the phrase "second beam" is to be taken as referring to either the second beam as explained with respect to <FIG> or <FIG>. An "in-coverage period of the first beam" and an "in-coverage period of the second beam" are taken to mean a time period which a communications device spends in the coverage area <NUM> defined by the first beam and the coverage area <NUM> defined by the second beam respectively.

In such configurations, each of the plurality of cells has a different Physical Cell Identity (PCI). Accordingly, reference signals and scrambling codes used may be different for each of the plurality of cells, and each of the plurality of cells may be scheduled independently of each other. A handover of the communications device <NUM> from the coverage area <NUM> of the first beam to the coverage area <NUM> of the second beam may consist of a connected mode handover, a cell selection procedure or a cell reselection procedure. The handover procedure may be controlled by measurements made by the communications device and communicated to the base station, controlled by measurements made by the base station, controlled by declaration of radio link failure by the communications device or by other means.

There is a need to ensure that connectivity for the communications device <NUM> with the ground station <NUM> can be maintained, in light of the movement of the communications device <NUM>, the movement of the aerial vehicle <NUM> (relative to the Earth's surface), or both. According to conventional cellular communications techniques, a decision to change a serving cell of the communications device <NUM> 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 communications device <NUM> 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 communications circuitry <NUM> of an aerial vehicle, such as the cell <NUM> generated by the aerial vehicle <NUM>.

A further challenge of conventional techniques may be the relatively high rate at which cell changes occur for the communications device <NUM> obtaining service from one or more aerial vehicles. For example, where the aerial vehicle <NUM> is an LEO satellite, the aerial vehicle <NUM> may complete an orbit of the Earth in around <NUM> minutes; the coverage of a cell generated by the aerial vehicle <NUM> will move very rapidly, with respect to a fixed observation point on the surface of the Earth (in one example, an LEO may move at <NUM>/s as explained above). Similarly, it may be expected that the communications device <NUM> may be mounted on an airborne vehicle itself, typically having a ground speed of several hundreds of kilometres per hour. However, it will be appreciated that a speed of the aerial vehicle <NUM> relative to a fixed point on the Earth is generally much larger than typical speeds of airborne vehicles configured to mount the communications device <NUM>.

One particular difficulty associated with NTNs is the large distances and relative speeds between a UE (such as communications device <NUM>) and an eNB (such as base station <NUM> or a base station implemented in the communications circuitry <NUM>) compared to terrestrial networks. For example, for an LEO, the distance between the satellite and the UE may be between <NUM> to <NUM>. Hence, the propagation delay between the UE (hereinafter the term UE is used to refer to any communications device configured to communicate with a non-terrestrial infrastructure equipment of an NTN) and the eNB is significantly larger than for terrestrial networks, particularly in a 'transparent' arrangement such as that shown in <FIG>. For example, for an NTN using a transparent LEO satellite in a <NUM> high orbit, the Round Trip Time (RTT) between the UE and the eNB may be between approximately <NUM> to approximately <NUM> [<NUM>].

In order to take into account this large propagation delay, uplink transmissions would need to apply a large Timing Advance (TA) and the eNB would need to take this into account for scheduling of uplink data. The timing advance that needs to be applied depends on the location of the UE within the cell footprint of the satellite. Since the cell footprint can be large, there can be a large variation of the timing advance that needs to be applied, depending on the UE location within the cell footprint.

In addition to the increased RTT between the UE and the eNB, the NTN system also needs to take into account the movement of the satellite. For example, a LEO satellite can be travelling at <NUM>/second (<NUM>,<NUM>/h) relative to the UE, which would cause significant Doppler shift that the UE needs to compensate for. In order to factor in the Doppler shift, i.e. in order to apply a pre-compensation for the frequency of the uplink transmissions, the UE needs to know its own geo-location and the motion (e.g. position and velocity) of the satellite. The geo-location of the UE can, for example, be obtained from a Global Navigation Satellite System (GNSS) or from any other suitable means.

The position and velocity of the satellite can be derived from the satellite ephemeris information, that is the satellite orbital trajectory, which can be periodically broadcast to the UE, e.g. via System Information Blocks (SIBs). However, broadcasting ephemeris information, e.g. every <NUM>, can lead to high signaling overhead.

Furthermore, signaling ephemeris information does not take into account perturbations in the satellite orbit and hence may not provide sufficient accuracy to determine the required timing advance and frequency compensation. In particular, satellites in LEO do not exist in a perfect vacuum and thus experience a number of factors such as varying drag coefficients or gravitational forces which perturb the orbit of the satellite. As such, as the time since a UE last received a periodic broadcast of the satellite ephemeris information increases, the accuracy with which the UE can accurately determine the position and velocity of the satellite decreases.

One possibility is that instead of sending ephemeris information, the eNB or an NTN Gateway can derive the satellite position and velocity and broadcast it via the SIBs. The satellite position and velocity may be determined by the eNB or NTN Gateway, for example, via GNSS or other suitable means. The eNB or NTN Gateway may determine the satellite position and velocity via communications on the network itself, or the eNB or NTN Gateway may determine the satellite position and velocity by other means, separate from the network. For example, the eNB or NTN Gateway may derive the satellite position and velocity, e.g. via a telemetry link to the satellite, and the eNB may transmit that information in the SIBs. The eNB/NTN Gateway may estimate satellite position and velocity at the System Frame Number (SFN) in which the SIB is broadcasted, thereby providing real time position and velocity information. Hereinafter, the term 'eNB' is used to refer to any of a base station, agNB, an eNB or an NTN gateway, unless explicitly stated otherwise.

As explained above, the large distances and relative speeds between the UE and the eNB for NTNs compared to terrestrial networks lead to technical challenges. Another associated difficulty for NTNs compared to terrestrial networks is that the UE spends a relatively short time in a coverage area of the cell compared to terrestrial networks. The time which a UE spends in the coverage area of a cell for NTNs depends on a distance between the UE and a satellite (which may or may not be co-located with the eNB as explained above), a speed of the UE relative to the satellite and a width of a spot beam generated by the satellite which provides the coverage area.

In one example, an LEO orbiting the Earth at an altitude of <NUM> and generating a spot beam operating at a carrier frequency of <NUM> may have an 3dB angular beamwidth of <NUM> degrees (corresponding to a <NUM> beamwidth when the LEO is at its zenith) [<NUM>]. For a LEO moving at <NUM>/sec, the UE will be in the coverage area of the spot beam for only <NUM> seconds.

An example of difficulties which may arise from the relatively short time period which a communications device spends in a coverage area of a satellite is explained with reference to <FIG> is a simplified representation of examples of scheduled communications resources in time and frequency space for transmitting uplink data from the communications device <NUM> to the aerial vehicle <NUM> while the communications device <NUM> is in the coverage area <NUM> of a beam generated by the aerial vehicle <NUM>. As shown in <FIG>, the communications device <NUM> is in the coverage area <NUM> of the beam generated by the aerial vehicle <NUM> for an in-coverage period <NUM> of <NUM> seconds. Accordingly, a base station (which may be implemented in the aerial vehicle <NUM> or may be on the ground as explained above) may schedule the communications device <NUM> to transmit signals representing uplink data during the in-coverage period <NUM>. In some examples, the base station may schedule the communications device <NUM> to transmit signals representing uplink data during the in-coverage period <NUM> in the form of a Physical Uplink Shared Channel (PUSCH) transmission with an associated transmission period. The transmission period of a PUSCH transmission is the time taken for a complete PUSCH transmission. In NB-IoT, the transmission period for a PUSCH transmission can be up to <NUM> seconds, where the maximum transmission period of the PUSCH can be determined by the eNB scheduler up to a maximum value supported in the NB-IoT specifications. If the transmission period for a PUSCH transmission is less than the in-coverage period <NUM>, then the PUSCH transmission may be completely transmitted if it is scheduled to begin at any time during a scheduling window <NUM> of the in-coverage period <NUM>. In <FIG>, an early PUSCH transmission <NUM> and a late PUSCH transmission <NUM> are the earliest and latest respective PUSCH transmissions which can be completely transmitted in the in-coverage period <NUM>. A start point <NUM> of the in-coverage period <NUM> coincides with a start point of the scheduling window <NUM> and a start point of the early PUSCH transmission <NUM>. An end point <NUM> of the in-coverage period coincides with an end point of the late PUSCH transmission <NUM>. An end point <NUM> of the scheduling window <NUM> coincides with a start point of the late PUSCH transmission <NUM>. It will be appreciated that, in the example provided in <FIG>, a length of the scheduling window is provided by a difference between a length of the in-coverage period <NUM> (<NUM> seconds) and the transmission period (<NUM> seconds). Accordingly, in the example provided in <FIG>, the length of the scheduling window <NUM> is approximately two seconds.

Accordingly, for the example provided in <FIG>, a PUSCH transmission must be scheduled to begin within the approximately two second scheduling window <NUM> in order to ensure complete PUSCH transmission. If a PUSCH transmission is scheduled to begin later than the scheduling window <NUM> then the PUSCH transmission may not be able to be completely transmitted within the in-coverage period <NUM>.

As indicated above, <FIG> is a simplified representation of examples of scheduled communications resources in time and frequency space for transmitting uplink data from the communications device <NUM> to the aerial vehicle <NUM> while the communications device <NUM> is in the coverage area <NUM> of a beam generated by the aerial vehicle <NUM>. <FIG> is based on <FIG> and additionally accounts for transition times for the communications device <NUM> to enter and leave the coverage area <NUM> of the beam. As the communications device <NUM> leaves the coverage area <NUM> of the beam, which is a first beam, it may enter a coverage area of another, second beam (such as coverage area <NUM>). The second beam may be generated by an antenna of the aerial vehicle <NUM> which provides the first beam or, alternatively, by an antenna of another aerial vehicle (such as aerial vehicle <NUM>). As will be appreciated, a portion of the in-coverage period <NUM> may be occupied by a time taken for the communications device to transition into the coverage area <NUM> of the first beam (referred to as "entering period <NUM>") and a time taken for the communications device <NUM> to transition out of the coverage area <NUM> of the first beam (referred to as "leaving period <NUM>").

Communications resources in the entering period <NUM> may be reserved for various communications processes as the communications device <NUM> enters the coverage area <NUM> of the first beam. For example, during the entering period <NUM>, the communications device <NUM> may:.

Similarly, communications resources in the leaving period <NUM> may be reserved for various communications processes as the communications device <NUM> moves out of the coverage area of the first beam. For example, during the leaving period <NUM>, the communications device <NUM> may:.

Since communications resources are reserved during the entering period <NUM> and the leaving period <NUM>, it may not be possible to schedule signals representing uplink or downlink data to be transmitted to or from the communications device <NUM> respectively in the entering period <NUM> or the leaving period <NUM>. For example, <FIG> shows an early PUSCH transmission <NUM> and a late PUSCH transmission <NUM> which are the earliest and latest respective PUSCH transmissions which can be completely transmitted in the in-coverage period <NUM> when the entering period <NUM> and the leaving period <NUM> are accounted for. In <FIG>, a PUSCH transmission may be completely transmitted if it is scheduled to begin at any time during a scheduling window <NUM> of the in-coverage period <NUM>. A start point <NUM> of the scheduling window <NUM> coincides with a start point of the early PUSCH transmission <NUM>. An end point <NUM> of the scheduling window <NUM> coincides with a start point of the late PUSCH transmission <NUM>. A start point of the leaving period <NUM> coincides with an end point of the late PUSCH transmission <NUM>.

It will be appreciated that, in the example provided in <FIG>, a length of the scheduling window is provided by a difference between a length of the in-coverage period <NUM> (<NUM> seconds) and the transmission period (<NUM> seconds), less the entering period <NUM> and the leaving period <NUM>. Accordingly, in the example provided in <FIG>, the length of the scheduling window <NUM> is less than the scheduling window <NUM> in <FIG>.

Accordingly, for the example provided in <FIG>, a PUSCH transmission must be scheduled to begin within the less than two second scheduling window <NUM> in order to ensure complete PUSCH transmission. If a PUSCH transmission is scheduled to begin later than the scheduling window <NUM> then the PUSCH transmission may not be able to be completely transmitted.

An NB-IoT transmission spanning <NUM> seconds is referred to in the present disclosure as consisting of <NUM> repetitions. It will be appreciated that references to "repetitions" may consist of a mixture of resource units and actual repetitions. Although the present disclosure refers to eMTC transmissions of <NUM> seconds duration or of <NUM> repetitions, it will be appreciated by one skilled in the art that this is merely an example and other durations/number of repetitions may be used. While the maximum number of eMTC transmissions in a current standard is <NUM> repetitions, it will be appreciated that the following description refers to eMTC transmissions of <NUM> second duration as this acts to highlight the nature of the problem to be solved. It will further be appreciated that embodiments discussed below with respect to eMTC may be applied to NB-IoT. In NB-IoT, transmissions of duration <NUM> seconds are possible according to the current standards.

In view of the above-mentioned technical challenges, there is provided a method of operating a communications device to transmit or to receive via a wireless communications network including non-terrestrial, NTN, infrastructure equipment. The communications device identifies a first in-coverage period during which the communications device can transmit signals to or receive signals from a first NTN infrastructure equipment, the first NTN infrastructure equipment being either carried by a first aerial vehicle or relayed via the first aerial vehicle to or from the first NTN infrastructure equipment as the aerial vehicle passes over the communications device. The communications device identifies a second in-coverage period during which the communications device can transmit signals to or receive signals from either the first NTN infrastructure equipment or a second NTN infrastructure equipment, the second NTN infrastructure equipment being either carried by a second aerial vehicle or the transmitted or the received signal are relayed via the second aerial vehicle to or from the second NTN infrastructure equipment as the second aerial vehicle passes over the communications device. The communications device transmits uplink data to the wireless communications network by adapting a transmission of the uplink data to include at least part of the second in-coverage period, based on a length of time required to transmit the uplink data and a start time at which the uplink data can be transmitted in the first in-coverage period with respect to an end of the first in-coverage period, or alternatively, the communications device receives downlink data from the wireless communications network by adapting a reception of the downlink data to include at least part of the second in-coverage period, having been transmitted at least partly in the second in-coverage period, based on a length of time required to receive the downlink data and a start time at which the downlink data can be received in the first in-coverage period with respect to an end of the first in-coverage period.

<FIG> illustrates an example of the communications device <NUM> deferring an uplink transmission according to example embodiments. The communications device <NUM> receives an MTC PDCCH (MPDCCH) transmission <NUM> while in the coverage period <NUM> of the first beam. The MPDCCH transmission <NUM> informs the communications device <NUM> that it has been scheduled to transmit a PUSCH transmission <NUM>. As shown in <FIG>, the scheduled PUSCH transmission <NUM> cannot be completely transmitted before the communications device <NUM> moves out of the coverage area <NUM> of the first beam. In other words, an available time period <NUM> for transmission is less than a transmission time period for the scheduled PUSCH transmission <NUM>. As shown in <FIG>, a start point <NUM> of the available time period <NUM> coincides with a start point of the scheduled PUSCH transmission <NUM> and an end point <NUM> of the available time period <NUM> coincides with a start point of the leaving period <NUM> for the first beam. Since the available time period <NUM> is shorter than the transmission time period <NUM> for the scheduled PUSCH <NUM>, the scheduled PUSCH cannot be completely transmitted in the in-coverage period <NUM> of the first beam.

The communications device <NUM> may determine that the scheduled PUSCH <NUM> cannot be completely transmitted in the in-coverage period <NUM> of the first beam. In response, the communications device <NUM> may determine to defer transmission of the scheduled PUSCH <NUM> until the communications device <NUM> is in the coverage area <NUM> of the second beam. In example embodiments, the communications device <NUM> may defer the transmission of the scheduled PUSCH <NUM> to begin at an end point <NUM> of an entering period <NUM> for the second beam, as shown by the deferred PUSCH <NUM> in <FIG>. During the entering period <NUM> for the second beam, the communications device <NUM> may prepare for transition into the coverage area <NUM> of the second beam by performing a synchronisation process, performing measurements and/or executing a Random Access Channel (RACH) process in the second beam for example.

In such embodiments, a length of the entering period <NUM> for the second beam may be known by both the communications device <NUM> and the base station which schedules the communications device <NUM>. For example, the length of the entering period <NUM> may be represented as a number of subframes (Ntrans) after a start point of the in-coverage period <NUM> of the second beam (which coincides with the end point of the in-coverage period <NUM> of the first beam in <FIG>). The value of Ntrans may be defined in specifications, signalled explicitly to the communications device <NUM> by the base station in Downlink Control Information (DCI) or signalled by other means. In some cases, the value of Ntrans may be a function of a coverage level of the communications device <NUM> in which case the communications device <NUM> may be aware of a mapping between the coverage level and Ntrans, and use the mapping to determine the value of Ntrans based on a measured coverage level.

Such embodiments allow the communications device <NUM> to prepare for transmissions when it is in the coverage area <NUM> of the second beam and can arrange for the deferred PUSCH <NUM> to be transmitted as early as possible after the communications device <NUM> has entered the coverage area <NUM> of the second beam. In some embodiments, as shown in <FIG>, the communications device <NUM> may use the same frequency resources to transmit the deferred PUSCH <NUM> which were intended to be used by the scheduled PUSCH <NUM> (an offset in frequency space is shown between the scheduled PUSCH <NUM> and the deferred PUSCH <NUM> to improve the clarity of <FIG>, but it will be appreciated that the frequency offset is approximately zero for such embodiments).

In some embodiments, a Physical Uplink Control Channel (PUCCH) transmission may be providing HARQ-ACK feedback for a Physical Downlink Shared Channel (PDSCH) transmission when the communications device <NUM> is in the coverage area <NUM> of the first beam. In such embodiments, the communications device <NUM> may determine that it cannot completely transmit the scheduled PUCCH in the in-coverage period <NUM> of the first beam and defers transmission of the PUCCH until the in-coverage period <NUM> of the second beam.

In some embodiments, communications device <NUM> may be configured to operate with pre-configured uplink resources (PUR). In such embodiments, the communications device <NUM> may determine that it cannot completely transmit a PUR transmission when the communications device <NUM> is in the in-coverage period <NUM> of the first beam and defers transmission of the PUR until the in-coverage period <NUM> of the second beam.

It will be appreciated that embodiments discussed with reference to <FIG> are not limited to uplink transmissions and may be applied to downlink transmissions.

In example embodiments, as illustrated in <FIG>, the base station may explicitly signal to the communications device <NUM> an indication of which communications resources (time and frequency resources) it should use for a PUSCH transmission <NUM> in the in-coverage period <NUM> of the second beam. For example, as illustrated in <FIG>, the base station may include a DCI in the MPDCCH transmission <NUM> with a bit <NUM> indicating which communications resources in the in-coverage period <NUM> of the second beam that the communications device can use to transmit the PUSCH <NUM> scheduled by the MPDCCH transmission <NUM>.

In some embodiments, the bit <NUM> in the DCI signals a time delay after the MPDCCH transmission <NUM> at which the PUSCH <NUM> should begin to be transmitted. If the time delay is greater than a remaining time during which the communications device <NUM> is located in the coverage area of the first beam, then the communications device <NUM> transmits the PUSCH <NUM> during the in-coverage period <NUM> of the second beam.

In some embodiments, the base station may determine that there is insufficient time remaining in the in-coverage period <NUM> of the first beam for the communications device <NUM> to completely transmit signals representing data scheduled by the base station to the base station. In such embodiments, the base station may determine not to schedule the communications device <NUM> to transmit the signals representing the data in the in-coverage period <NUM> of the first beam. In such embodiments, if the same base station is configured to schedule transmissions for the communications device <NUM> in both the in-coverage period <NUM> of the first beam and the in-coverage period <NUM> of the second beam, then the base station may prepare for the signals representing the data to be transmitted in the in-coverage period <NUM> of the second beam. In other words, the base station defers the scheduling of the signals representing the data to be transmitted in the in-coverage period <NUM> of the second beam.

<FIG> illustrates an example of a base station deferring uplink transmission according to example embodiments. As shown by arrow <NUM>, uplink data arrives in a buffer of the communications device <NUM>. The communications device <NUM> then transmits, to the base station, an indication that it has uplink data to transmit to the base station. The indication that the communication device <NUM> has uplink data to transmit to the base station may take the form of a scheduling request or buffer status report for example. In response to receiving the indication that the communications device <NUM> has uplink data to transmit to the base station, the base station determines that there is insufficient time remaining in the in-coverage period <NUM> of the first beam for the communications device <NUM> to completely transmit signals representing the uplink data in the in-coverage period <NUM> of the first beam. In the example shown in <FIG>, the signals representing the uplink data are specifically transmitted in a PUSCH transmission. As shown by arrow <NUM>, the base station then defers scheduling the PUSCH transmission until the in-coverage period <NUM> of the second beam. In the example shown in <FIG>, the base station defers transmitting an MPDCCH <NUM> until the in-coverage period <NUM> of the second beam. The MPDCCH <NUM> schedules a PUSCH transmission <NUM> for the communications device <NUM> in the in-coverage period <NUM> of the second beam. In some embodiments, as shown in <FIG>, the MPDCCH <NUM> is transmitted at a time which coincides with an end point <NUM> of the entering period <NUM> for the second beam to ensure the PUSCH transmission <NUM> is transmitted immediately after the communications device <NUM> enters the coverage area <NUM> of the second beam.

The communications device <NUM> may receive a downlink transmission containing signals representing downlink data from the base station. In some embodiments, the communications device <NUM> may determine that there is insufficient time remaining in the in-coverage period <NUM> of the first beam for the communications device <NUM> to completely receive the downlink transmission. In such embodiments, the communications device <NUM> may store Log-Likelihood Ratios (LLRs) related to the part of the downlink transmission which was not received. For example, the communications device <NUM> may determine that a downlink transmission (such as a PDSCH or MPDCCH) is not received correctly if a full set of scheduled repetitions is not received at the communications device <NUM> when the communications device <NUM> moves from the coverage area <NUM> of the first beam to the coverage area <NUM> of the second beam. In response, the communications device <NUM> stores LLRs related to the parts of the downlink transmission which were not received correctly. By storing the LLRs related to the parts of the downlink transmission which were not received correctly, the communications device <NUM> is configured to receive a retransmission of the parts of the downlink transmission which were not received correctly during the in-coverage period <NUM> of the second beam. In a particular example, the communications device <NUM> may be scheduled with <NUM> repetitions of PDSCH when it is in the coverage area <NUM> of the first beam. However, only <NUM> repetitions of the PDSCH may have been received by the communications device <NUM> before the end point <NUM> of the in-coverage period <NUM> of the first beam. The communications device <NUM> may then store the LLRs relating to the remaining <NUM> repetitions of the PDSCH to be retransmitted in the in-coverage period <NUM> of the second beam.

In some embodiments, the communications device <NUM> may determine parameters (such as a number of repetitions) for transmitting the remaining parts of the downlink transmission based on parameters of the part of the downlink transmission which was received by the communications device <NUM>. Such embodiments do not require an MPDCCH to be transmitted in the in-coverage period <NUM> of the second beam. For example, if a PDSCH transmission with <NUM> repetitions was scheduled during the in-coverage period <NUM> of the first beam and only <NUM> repetitions were received by the communications device <NUM>, the communications device <NUM> determines that the part of the downlink transmission to be retransmitted consists of <NUM> repetitions. In example embodiments, the number of repetitions for the re-transmission may take into account changes in a quality of a radio link connecting the communications device <NUM> and the aerial vehicle <NUM> between the in-coverage period <NUM> of the first beam and the in-coverage period <NUM> of the second beam. For example, if the pathloss during the in-coverage period <NUM> of the first beam is different to the pathloss during the in-coverage period <NUM> of the second beam (for example, where the first and second beams are generated by different satellites on different orbital trajectories), the number of repetitions may be scaled by the pathloss difference.

<FIG> illustrates an example of a communications device receiving re-transmitted parts of a downlink transmission which were not correctly received according to example embodiments. As shown in <FIG>, the base station transmits an MPDDCH <NUM> which schedules a PDSCH transmission <NUM> for the communications device <NUM>. As will be appreciated from <FIG>, the scheduled PDSCH transmission <NUM> cannot be completely transmitted in the in-coverage period <NUM> of the first beam. The communications device may determine that the PDSCH transmission <NUM> cannot be completely transmitted in the in-coverage period <NUM> of the first beam and, in response, stores LLRs related to parts <NUM> of the PDSCH which were received by the communications device <NUM> but did not in themselves enable successful decoding of the PDSCH. The communications device <NUM> may use parameters of parts <NUM> of the PDSCH which were correctly received, but in themselves did not enable successful decoding of the PDSCH, by the communications device <NUM> to determine parameters for receiving the re-transmission of the parts <NUM> of the PDSCH which were not correctly received by the communications device <NUM>. For example, the communications device <NUM> may determine that the scheduled PDSCH <NUM> consists of <NUM> repetitions and that the parts <NUM> of the PDSCH which were correctly received consist of <NUM> repetitions to determine that the parts <NUM> of the PDSCH which were not correctly received are to be received according to a re-transmission with <NUM> repetitions. Accordingly, it is not necessary for the base station to transmit another MPDCCH to schedule the re-transmission.

Although the above embodiments have been described with respect to the downlink transmission, it will be appreciated that such embodiments are equally applicable to uplink transmission. For example, the base station may store LLRs related to parts of an uplink transmission which was not correctly received at the base station during the in-coverage period <NUM> of the first beam, and use the stored LLRs in combination with the LLRs received from the retransmitted parts of the uplink transmission that are received during the in-coverage period <NUM> of the second beam in order to fully decode the uplink transmission.

In some embodiments, the parts <NUM> of the scheduled PDSCH which were not correctly received by the communications device <NUM> may be re-scheduled by another MPDCCH to be transmitted in the in-coverage period <NUM> of the second beam. Specifically, the base station may transmit another MDPCCH during the coverage period <NUM> of the second beam to inform the communications device <NUM> to receive the parts <NUM> of the scheduled PDSCH which were not correctly received during the coverage period <NUM> of the second beam. Such embodiments are particularly advantageous when the interrupted transmission (which is described as PDSCH in this example) is an uplink transmission (for example, PUSCH). This is because the base station may terminate the PUSCH early, as it may able to decode the PUSCH without the re-scheduled parts.

In some embodiments, the parts <NUM> of the scheduled PDSCH which were not correctly received by the communications device <NUM> may be re-scheduled by another MPDCCH containing DCI to be transmitted in the in-coverage period <NUM> of the second beam. Specifically, the base station may transmit another MDPCCH during the coverage period <NUM> of the second beam to inform the communications device <NUM> to receive a transmission of the parts <NUM> of the scheduled PDSCH which were not correctly received during the coverage period <NUM> of the second beam. The DCI may inform the communications device <NUM> to continue reception during the in-coverage period <NUM> of the second beam which was started during the in-coverage period <NUM> of the first beam. In some embodiments, the DCI may indicate that the reception during the in-coverage period <NUM> of the second beam should continue with different parameters than were used for the reception during the in-coverage period <NUM> of the first beam. For example, the DCI may indicate that a redundancy version (RV) and/or frequency resources for the reception in the in-coverage period <NUM> of the second beam have changed relative to an RV and/or frequency resources for the reception in the in-coverage period <NUM> of the first beam. Such embodiments can improve scheduling flexibility during the in-coverage period <NUM> of the second beam.

In some embodiments, the communications device <NUM> ensures that its HARQ buffers are not flushed when the communications device <NUM> is handed over from the first beam to the second beam. If the HARQ buffers are not flushed, then the communication device is able to combine transmissions which occur during the in-coverage period <NUM> of the first beam and transmissions which occur during the in-coverage period <NUM> of the second beam. In some embodiments, identical transport blocks are used for the transmission in the in-coverage period <NUM> of the first beam and for the re-transmission in the in-coverage period <NUM> of the second beam. In such embodiments, the same Medium Access Control (MAC) control elements are transmitted in both the in-coverage period <NUM> of the first beam and in the in-coverage period <NUM> of the second beam. It will be appreciated that MAC control elements contribute to bits that are transmitted in the transport block. Since the MAC control elements control some cell functionality (for example timing advance and power headroom reporting), the MAC control elements that were transmitted during the in-coverage period <NUM> of the first beam may not be applicable for the in-coverage period <NUM> of the second beam.

In some embodiments, the communications device <NUM> or base station receives the MAC control elements during the in-coverage period <NUM> of the second beam and determines that the received MAC control elements apply for the in-coverage period <NUM> of the first beam.

In some embodiments, the communications device <NUM> or base station may determine that some of the contents of the received MAC control elements apply for the in-coverage period <NUM> of the second beam. For example, MAC control elements such as timing advance (TA) may be applicable for both the in-coverage period <NUM> of the first beam and the in-coverage period of the second beam if the first and second beams are generated by the same satellite. As will be appreciated, the TA depends on a distance between the communication device <NUM> and the serving satellite, and the distance from the base station to the satellite which does not change if the communications device <NUM> switches from being served by the first and second beams if they are generated by the same satellite.

In some embodiments, a transport block encoded by the communications device <NUM> for uplink transmission is not flushed when the communication device <NUM> is handed over from the first beam to the second beam if the uplink transmission is not completely transmitted during the in-coverage period <NUM> of the first beam. Such embodiments allow the communications device <NUM> to use the encoded transport block to continue with the remaining part of the uplink transmission during the in-coverage period <NUM> of the second beam.

In some embodiments, the base station may transmit DCI signals to the communication device <NUM> to instruct the communications to perform one of the following procedures:.

As explained above, in some embodiments, there may be insufficient time for all of the repetitions of an uplink/downlink transmission to be completely transmitted in the in-coverage period <NUM> of the first beam. The repetitions which were not transmitted in the in-coverage period <NUM> of the first beam may be re-transmitted in the in-coverage period of the second beam. In some embodiments, the re-transmitted repetitions may be transmitted in the in-coverage period <NUM> of the second beam with the same characteristics which were used for the transmission in the in-coverage period <NUM> of the first beam. Such "characteristics" may include one or more of a scrambling code, a Demodulation Reference Signal (DMRS) sequence and Koffset. In conventional systems, the scrambling code and DMRS sequence generator are functions of cell ID and Koffset is a timing offset that is applied in NTN systems to extend a timeline in LTE / NR timing relationships (for example, to extend the time between MPDCCH transmission and PDSCH reception).

According to example embodiments, if the number of repetitions of a downlink transmission (for example, PDSCH) is too large for the downlink transmission to be completely transmitted during the in-coverage period <NUM> of the first beam then the communications device <NUM> may receive the repetitions, which were not successfully received at the communications device <NUM>, during the in-coverage period <NUM> of the second beam with the same characteristics that were used to receive the downlink transmission during the in-coverage period <NUM> of the first beam. In such embodiments, the base station transmits the re-transmitted repetitions during the in-coverage period <NUM> of the second beam with the same characteristics that were used to transmit the downlink transmission during the in-coverage period <NUM> of the first beam.

According to example embodiments, if the number of repetitions of an uplink transmission (for example, PUSCH) is too large for the uplink transmission to be completely transmitted during the in-coverage period <NUM> of the first beam then the communications device <NUM> may transmit the repetitions which were not successfully transmitted at the communications device <NUM> during the in-coverage period <NUM> of the second beam with the same characteristics that were used to transmit the uplink transmission during the in-coverage period <NUM> of the first beam. In such embodiments, the base station receives the re-transmitted repetitions during the in-coverage period <NUM> of the second beam with the same characteristics that were used to receive the uplink transmission during the in-coverage period <NUM> of the first beam.

In such embodiments, after the re-transmitted repetitions have been successfully transmitted, the base station may convert a new cell corresponding to the coverage area <NUM> of the second beam to operate in accordance with transmissions for the new cell. For example, the base station may reconfigure the satellite to operate in accordance with a new TA (timing advance) and/or Koffset.

In some embodiments, the re-transmitted repetitions may be transmitted in the in-coverage period <NUM> of the second beam with different characteristics which were used for the transmission in the in-coverage period <NUM> of the first beam.

In some embodiments, repetitions which span the leaving period <NUM> for the first beam and the entering period <NUM> for the second beam may be dropped.

In some embodiments, the re-transmitted repetitions are delayed during the leaving period <NUM> for the first beam and the entering period <NUM> for the second beam.

<FIG> illustrates re-transmitted repetitions being transmitted in the in-coverage period <NUM> of the second beam with the same characteristics which were used for the transmission in the in-coverage period <NUM> of the first beam according to example embodiments. As shown in <FIG>, a first MDPCCH <NUM> is transmitted by the base station to the communications device <NUM> which schedules a PUSCH transmission <NUM> spanning <NUM> repetitions. In the embodiment shown in <FIG>, the repetitions which span the leaving period <NUM> for the first beam and the entering period <NUM> for the second beam are dropped. The communications device re-transmits a part <NUM> of the scheduled PUSCH transmission <NUM> which was not transmitted during the in-coverage period <NUM> of the first beam using the same scrambling code and DMRS sequence as was used for a part <NUM> of the scheduled PUSCH transmission <NUM> which was transmitted during the in-coverage period <NUM> of the first beam. After the re-transmission <NUM> is complete, the communications device <NUM> switches from using the scrambling code and DMRS which was used for the part <NUM> of the scheduled PUSCH transmission <NUM> which was transmitted during the in-coverage period <NUM> of the first beam to using a scrambling code and DMRS sequence for the new cell corresponding to the coverage area <NUM> of the second beam. The communications device <NUM> may then receive and decode a second MPDCCH <NUM> which schedules another PUSCH <NUM> which the communications device <NUM> transmits using the scrambling code and DMRS sequence for the new cell corresponding to the coverage area <NUM> of the second beam.

In the conventional systems, an RV and scrambling code are maintained for every <NUM> repetitions. For example if there are <NUM> repetitions, the 1st to 4th repetition may use one RV and scrambling code, the 5th to 8th repetitions may use another RV and another scrambling code. Such arrangements facilitate symbol combining at a receiver and cross subframe channel estimation for every batch of <NUM> repetitions. If the repetition is cut off during a batch (rather than at a batch boundary), a benefit of symbol combining and cross subframe channel estimation is reduced. Benefits of symbol combining can include improving a signal to noise (SNR) ratio and simplifying receiver design. Benefits of cross channel estimation can include improved robustness and/or channel estimation accuracy.

An example of a repetition being cut off during a batch is shown in <FIG> shows three batches of four repetitions, namely, Batch n-<NUM>, Batch n and Batch n+<NUM>. Each batch contains four repetitions which each share the same RV and scrambling code. The communications device <NUM> hands over from a first cell (which may correspond to coverage area <NUM> as explained above) to a second cell (which may correspond to coverage area <NUM> as explained above) between repetition 4n and repetition 4n+<NUM>. In other words, a repetition is cut off during the Batch n, thereby reducing the benefit of symbol combining and cross subframe channel estimation for the 4n and 4n+<NUM> repetitions in Batch n. As the repetition is cut off during the Batch n, the Batch n may be referred to as a "cut-off batch".

In example embodiments, the "cut off" batch may be postponed. In other words, the repetition may be cut-off at a batch boundary rather than during a batch. For example, if the communications device <NUM> determines that a repetition is going to be cut off during a batch, the communications device <NUM> may delay transmission so that a new batch may be started in a new cell. For example, <FIG> illustrates the communications device <NUM> delaying a transmission to avoid a repetition being cut off during a batch. As explained with reference to <FIG>, the batch n would be cut off after repetition 4n according to conventional systems. However, Figure 14B shows that the communications device <NUM> delays the transmission so that the repetition 4n starts after it has handed over to the second cell <NUM>. The cut therefore occurs at a batch boundary between Batch n-<NUM> and Batch n.

In example embodiments, the "cut off" batch may be restarted in a new cell. In other words, the communications device <NUM> may continue to transmit (or receive) a batch that is cut off but restarts the transmission (or reception) of the cut off batch in the new cell. <FIG> illustrates an example of the communications device <NUM> restarting a cut-off batch in a new cell. As shown in <FIG>, batch n is due to be cut off after repetition 4n as a result of a handover of the communications device <NUM> from the first cell <NUM> to the second cell <NUM>. In example embodiments, the communications device <NUM> still transmits the 4n repetition in the first cell <NUM> but re-transmits the 4n repetition along with the remaining repetitions of the batch n when the communications device <NUM> enters the second cell <NUM>.

In example embodiments, the cut off batch is dropped. An example of a cut off batch being dropped is shown in <FIG>. As shown in <FIG>, batch n is due to be cut off after repetition 4n as a result of a handover of the communications device <NUM> from the first cell <NUM> to the second cell <NUM>. In example embodiments, the communications device drops the batch n in response to determining that the batch n is due to be a cut off batch. Such embodiments are particularly advantageous if an end time of a transmission needs to be maintained.

The functionality of cutting off a batch may be implemented at either the communications device or the base station. For example, considering downlink transmissions, if a batch is cut-off by the base station, the base station refrains from transmitting repetitions from that batch. In this case, the communications device would not store LLRs in its buffers relating to repetitions falling within the cut-off batch. In contrast, if the batch is cut-off at the communications device, the communications device refrains from receiving repetitions from the cut-off batch. In this case, the base station scheduler may choose a number of repetitions accounting for the fact that the communications device would not receive some of the repetitions.

In accordance with example embodiments, when a scheduled PUSCH transmission spans the in-coverage period <NUM> of the first beam and the in-coverage period <NUM> of the second beam, then System Information Block (SIB)/ Master Information Block (MIB) signalling may be used during the in-coverage period <NUM> of the second beam to indicate whether PUSCH transmissions in the in-coverage period <NUM> of the first beam are to be continued during the in-coverage period of the second beam. In some embodiments, DCI or RRC signalling may indicate that communications device <NUM> stops PUSCH transmission and continues the PUSCH transmission during the in-coverage period <NUM> of the second beam. In some embodiments, DCI or RRC signalling may indicate that communications device <NUM> stops PUSCH transmission when it changes cell (for example, at the end point <NUM> of the in-coverage period <NUM> of the first beam).

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.

Claim 1:
A method of operating a communications device (<NUM>) to transmit or to receive via a wireless communications network, which includes non-terrestrial, NTN, infrastructure equipment, the method comprising:
identifying, by the communications device, a first in-coverage period during which the communications device can transmit signals to or receive signals from a first NTN infrastructure equipment, the first NTN infrastructure equipment being either carried by a first aerial vehicle (<NUM>) or the transmitted or the received signals are relayed via the first aerial vehicle to or from the first NTN infrastructure equipment, as the first aerial vehicle passes over the communications device,
identifying, by the communications device, a second in-coverage period during which the communications device can transmit signals to or receive signals from either the first NTN infrastructure equipment or a second NTN infrastructure equipment, the second NTN infrastructure equipment being either carried by a second aerial vehicle (<NUM>) or the transmitted or the received signals are relayed via the second aerial vehicle to or from the second NTN infrastructure equipment as the second aerial vehicle passes over the communications device, and either
transmitting uplink data to the wireless communications network by adapting a transmission of the uplink data to include at least part of the second in-coverage period, based on a length of time required to transmit the uplink data and a start time at which the uplink data can be transmitted in the first in-coverage period with respect to an end of the first in-coverage period, or
receiving downlink data from the wireless communications network by adapting a reception of the downlink data to include at least part of the second in-coverage period, having been transmitted at least partly in the second in-coverage period, based on a length of time required to receive the downlink data and a start time at which the downlink data can be received in the first in-coverage period with respect to an end of the first in-coverage period.