Methods, non-terrestrial networks and communictions devices

Abstract

Communicating by a Non-Terrestrial Network (NTN) part of a wireless communications network with a plurality of communications devices comprises transmitting, from the NTN part, such as a satellite, radio signals for reception on the downlink by a first communications device and a second communications device multiplexed in co-scheduled communications resources using a plurality of antennas mounted on the satellite according to an MU-MIMO scheme, and / or receiving radio signals transmitted on the uplink by the first and the second communications devices multiplexed in co-scheduled communications resources using the plurality of antennas according to the MU-MIMO scheme. The radio signals are transmitted or received using the plurality of antennas according to the MU-MIMO scheme using precoding vectors of coefficients for each of the first and the second communications devices for the plurality of antennas when the first and second communications devices have sufficiently uncorrelated radio channel impulse responses. By using ancillary information such as a location of the communications devices (UEs) within a spot beam forming a cell of the NTN part, the wireless communications network / NTN part can determine a likelihood that a radio channel impulse response for respective pairs of UEs are uncorrelated and therefore an MU-MIMO scheme can be used to transmit and / or receive radio signals to each of the pairs of UEs in co-scheduled communications resources, such as for example a PDSCH of the cell.

Description

[0001] METHODS, NON-TERRESTRIAL NETWORKS AND COMMUNICATIONS DEVICES BACKGROUND

[0002] Field of Disclosure

[0003] The present disclosure relates generally to Non-Terrestrial Networks, NTNs, and specifically to methods of communicating with communications devices using an NTN part of a wireless communications network, NTN infrastructure equipment and communications devices. The present disclosure claims the Paris Convention priority of European patent application EP25166491.8, the content of which is incorporated by reference in its entirety.

[0004] Description of Related Art

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

[0006] Current and future wireless communications networks are expected routinely and efficiently to support communications with an ever-increasing range of devices associated with a wider range of data traffic profiles and types. For example, wireless communications networks will be expected efficiently to support communications with devices including reduced complexity devices, machine type communication (MTC) devices, high resolution video displays, virtual reality headsets, extended Reality (XR) and so on. Some of these different types of devices may be deployed in very large numbers, for example low complexity devices for supporting the “The Internet of Things”, and may typically be associated with the transmissions of relatively small amounts of data with relatively high latency tolerance. Other types of device, for example, devices supporting high-definition video streaming, may be associated with transmissions of relatively large amounts of data with relatively low latency tolerance. Other types of device, for example devices used for autonomous vehicle communications and for other critical applications, may be characterised by data that should be transmitted through the network with low latency and high reliability. A single device type might also be associated with different traffic profiles / characteristics depending on the application(s) it is running. For example, different considerations may apply for efficiently supporting data exchange with a smartphone when it is running a video streaming application (high downlink data) as compared to when it is running an Internet browsing application (sporadic uplink and downlink data) or being used for voice communications by an emergency responder in an emergency scenario (data subject to stringent reliability and latency requirements).

[0007] In view of this there is expected to be a desire for current wireless communications networks, for example those which may be referred to as 5G or new radio (NR) systems / new radio access technology (RAT) systems, or indeed future 6G wireless communications, as well as future iterations / releases of existing systems, efficiently to support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles and requirements.

[0008] One example area of current interest in this regard includes so-called “non-terrestrial networks”, or NTN for short. 3GPP has proposed in Release 15 of the 3GPP specifications to develop technologies for providing coverage by means of one or more antennas mounted on airborne or space-borne vehicles [1]. 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 formachine-to-machine (M2M) or ‘internet of things’ (loT) devices, or for passengers on board moving platforms (e.g. passenger vehicles such as aircraft, ships, high speed trains, or buses). Other benefits may arise from the use of non-terrestrial networks for providing multicast / broadcast resources for data delivery.

[0009] 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.

[0010] SUMMARY OF THE DISCLOSURE

[0011] The present disclosure can help address or mitigate at least some of the issues discussed above.

[0012] Some embodiments of the present technique can provide a method of communicating by a NonTerrestrial Network (NTN) part of a wireless communications network with a plurality of communications devices. The method comprises transmitting, from the NTN part, such as a satellite, radio signals for reception on the downlink by a first communications device and a second communications device multiplexed in co-scheduled communications resources using a plurality of antennas mounted on the satellite according to an MU-MIMO scheme, and / or receiving radio signals transmitted on the uplink by the first and the second communications devices multiplexed in co-scheduled communications resources using the plurality of antennas according to the MU-MIMO scheme. The radio signals are transmitted or received using the plurality of antennas according to the MU-MIMO scheme using precoding vectors of coefficients for each of the first and the second communications devices for the plurality of antennas when the first and second communications devices have sufficiently uncorrelated radio channel impulse responses. By using ancillary information such as a location of the communications devices (UEs) within a spot beam forming a cell of the NTN part, the wireless communications network / NTN part can determine a likelihood that a radio channel impulse response for respective pairs of UEs are uncorrelated and therefore an MU-MIMO scheme can be used to transmit and / or receive radio signals to each of the pairs of UEs in co-scheduled communications resources, such as for example a PDSCH of the cell. That is to say, transmission and reception occurs contemporaneously on the same communications resources for each of the pairs of UEs using precoding coefficients of the MIMO scheme assuming that the radio channel impulse response for each of the UEs in the pair will be uncorrelated based on for example a relative separation of the UEs on the Earth. In some examples, a distance between the UEs which exceeds a predetermined threshold and / or a difference in azimuth or angle of arrival of radio signals at the NTN part exceeding a threshold can be used to determine that there is a sufficient likelihood that the radio channels are uncorrelated and so the communications devices can be paired.

[0013] Respective aspects and features of the present disclosure are defined in the appended claims.

[0014] It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the present technology. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein like reference numerals designate identical or corresponding parts throughout the several views, and wherein:Figure 1 schematically represents some aspects of a wireless communications network, which includes a non-terrestrial network part, which provides a wireless access interface for communicating with communications devices (UEs) according to example embodiments of the present disclosure;

[0017] Figure 2 schematically represents a satellite which forms part of an NTN part of the wireless communications network transmitting radio signals on the downlink to a pair of communications devices (UEs) using a Multi-User Multiple Input Multiple Output (MU-MIMO) scheme in accordance with certain embodiments of the present disclosure;

[0018] Figure 3a schematically represents a radio channel impulse response profde illustrating a Ricean channel; Figure 3b schematically represents a radio channel impulse response profde illustrating one example in which a subset of a total number of resolved paths in multipath reflections of a typical radio channel impulse response are identified to represent the multipath components of a radio channel impulse response according to example embodiments; and Figure 3c schematically represents another example in which a single component path is used to represent multipath reflections of a radio channel impulse response according to example embodiments; and

[0019] Figure 4 is an illustrative flow diagram representing example operations of an NTN part of a wireless communications network in accordance with embodiments of the present disclosure.

[0020] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Non-Terrestrial Networks (NTNs)

[0022] As a result of wide service coverage capabilities and reduced vulnerability of space / airbome vehicles to physical attacks and natural disasters, Non-Terrestrial Networks are expected to:

[0023] • Extend coverage of 5G and 6G service in un-served areas that cannot be covered by terrestrial 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;

[0024] • reinforce 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 to

[0025] • enable network scalability by providing efficient multicast / broadcast resources for data delivery towards the network edges or even user terminal.

[0026] The benefits relate to either Non-Terrestrial Networks operating alone or to integrated terrestrial and NonTerrestrial networks. NTN will impact at least coverage, user bandwidth, system capacity, service reliability or service availability, energy consumption and connection density (see [5]). A role for NonTerrestrial Network components is expected for at least the following verticals: transport, Public Safety, Media and Entertainment, eHealth, Energy, Agriculture, Finance and Automotive.

[0027] An NTN can provide an access networking service based on a satellite / aerial platform with a bent pipe payload, meaning that the same data may be sent back down to Earth as is received by the satellite / aerial, with only frequency or amplification changing; i.e. acting like a pipe with a u-bend. In this example NTN, the satellite or the aerial platform will therefore relay a “satellite friendly” NR signal between a UE and the wireless communications network. In other examples, the satellite or aerial platform comprises full or part of a gNB to generate or receive a “satellite friendly” NR signal to / from UEs or relay nodes. This requires sufficient on-board processing capabilities to be able to include a gNB or relay node functionality. Relay node (RN) related use cases will play an important role in the commercial deployment of NTN; i.e. relay nodes mounted on high speed trains, relay nodes mounted in cruise ships,relay nodes at home / office and relay nodes mounted on airliners. It should be well understood by those skilled in the art that the proposed solutions of embodiments of the present technique could be equally applied to conventional UEs and RNs. TR 36.763 outlines a study carried out in 3GPP to adapt Rel-16 NB-IoT and eMTC for operation over NTN. The benefits of ubiquitous coverage are key for wide area services for many applications such as loT.

[0028] Figure 1 schematically shows an example of a wireless communications network, which includes an NTN part. The wireless communications network comprises a core network part 10 (which may be a 4G, 5G or 6G core network) in communicative connection with a terrestrial radio network part formed from base stations or gNBs 12 connected to the core network via interfaces 13. In a conventional manner, each of the gNBs 12 of the terrestrial radio network part forms one or more cells, shown with a representative boundary as a dashed line 14, within which the communications devices or user equipment (UE) 16 can transmit and receive signals 18 via a wireless access interface formed by each of the gNBs 12. The wireless communications network also comprises a ground station 20, which in combination with a satellite 22 forms a non-terrestrial network (NTN) part of the wireless communications system. The NTN part is formed from the ground station 20 in combination with the satellite 22, which forms a spot beam on the Earth represented by coverage area shown with a dashed line 24. Within the spot beam with the coverage area 24, UEs 16 can transmit radio signals to and receive radio signals from the satellite 22 via a non-terrestrial radio communications link represented by double-headed arrows 26. The satellite may be a non-terrestrial space vehicle or an airborne platform. The ground station 20 relays signals transmitted to or received from the UEs 16 via a separate backhaul channel link 28. The ground station 20 is connected to the core network part of the radio communications network via an interface 30. The satellite 22 in combination with the ground station 20 may form equivalent functionality in respect of protocol stack and physical layer processors to an infrastructure equipment. As shown in Figure 1, the satellite 22 may compromise a transceiver 32 and a controller 34 mounted on the satellite 22, as shown within expansion bubble represented by dashed line 36. As shown in Figure 1, the satellite 22 may also include a plurality of antennas 38, which are configured as part of the transceiver to transmit and to receive radio signals as part of a multiple input multiple output (MIMO) scheme as will be explained in more detail.

[0029] The satellite 22 in combination with the ground station 20, will be referred to an NTN part of the wireless access network. Essentially the NTN part is configured to communicate with the UEs 16, located within a cell formed within the spot beam 24 via a wireless access interface formed by the NTN part as represented by the wireless communications links 26. For example, the cell 24 may correspond to a coverage area of a spot beam generated by the NTN part, which may generate other spot beams which form cells of the NTN. The cells formed by the spot beams may or may not overlap. A boundary of the cell 24 may depend on an altitude of the NTN part and a configuration of the antennas 38 which transmit and receive radio signals on the NTN wireless access interface 26.

[0030] The satellite 22 may be in a geo-stationary earth orbit (GEO) such that it does not move with respect to a fixed point on the Earth’s surface. The geo-stationary earth orbit may be approximately 36,786 km above the Earth’s equator. The satellite may alternatively be in a low-earth orbit (LEO), in which it may complete an orbit of the Earth relatively quickly, thus providing moving cell coverage. Alternatively, the satellite may be in a non-geostationary orbit (NGSO), so that it moves with respect to a fixed point on the Earth’s surface. The satellite 22 may be an airborne platform such as an aircraft, or may be mounted on such a vehicle. The airborne platform may be stationary with respect to the surface of the Earth or may move with respect to the surface of the Earth.

[0031] In Figure 1, the earth or ground station 20 is shown as ground-based on the surface of the earth, and connected to the satellite 22 by means of the wireless communications link 28. The NTN part receivessignals representing downlink data transmitted by the ground station 20 on the communications link 28 and, based on the received signals, transmits signals representing the downlink data via the wireless communications links 26 providing the wireless access interface for the UEs 16. Similarly, the NTN part receives signals representing uplink data transmitted by the UEs 16 via the wireless access interface comprising the wireless communications links 26 and transmits signals representing the uplink data to the ground station 20 on the wireless communications link 28. The uplink and downlink communications link 28 may operate at a same frequency, or may operate at different frequencies.

[0032] A footprint of each beam forming the spot cell 24 of the satellite 22 is much wider than that from a terrestrial cell 14 with exact dimensions dependent on the height of the orbit of the satellite. Footprints can be hundreds of square kilometers wide within which there could be many UEs 16. Where a large number of UEs 16 fall within the footprint of a single beam 24, a wireless communications network needs to support a high connection density for all the UEs to be served. With limited bandwidth per component carrier, there is a possibility that the network may not be able to meet the connection densities required to support a large number of UEs 16 within the footprint of a satellite beam 24. One way to alleviate this is to increase the number of supported component carriers per beam but the extent of this solution is also limited by the scarcity of spectrum. Very high connection densities are needed for example to support the Internet of Things (loT) in which many objects of daily use will need a connection to NTN networks.

[0033] One means of improving connection densities is to support multi-user MIMO (MU-MIMO) . In MU-MIMO, the limited transmission resources of the access link (resource elements or resource blocks) are shared by more than one UE 16. As each UE 16 uses the same transmission resources to communicate with the network, a network that uses MU-MIMO can thereby increase its connection density - number of UEs simultaneously connected to the network per unit service area.

[0034] An environment within which a base station (gNB) and the UE are located in a terrestrial network (TN) is typically full of objects such as buildings, trees, mountains etc. that reflect and scatter the signals between the base station and the UE. This results in multipath propagation towards the receiver that is beneficial to traditional spatial multiplexing. The sharing of a given set of transmission resources between UEs using MU-MIMO exploits the spatial multiplexing gains that arise from the rich scattering environment present in such terrestrial networks. This multiplexing gain arises because the patterns (locations, distance from the UE, size and texture) of scatterers on the propagation paths between the base station and each individual UE are typically different from UE to UE. The differences in scattering patterns can cause different reflections of the signal between the base station and the UEs and these produce different multipath propagation profiles for the different links. The differences between two multipath propagation profiles can be quantified by assessing the degree of correlation between the profiles. If multipath propagation profiles between the base station and any two UEs are sufficiently uncorrelated, such UEs can be multiplexed on the same transmission resources using MU-MIMO.

[0035] In MIMO, prior to transmission, precoding is applied to the signals in each stream (one steam per antenna and transmitter / receiver chain) and these are then distributed to multiple antennas for emission. Effective spatial multiplexing is achieved when the precoding takes into account the characteristics of each of the channels the stream will traverse to arrive at the receiver. As those acquainted with MIMO will appreciate, each antenna has a vector of coefficients and with multiple antenna the vectors form a matrix.

[0036] In terrestrial networks (TN) such as 5G NR, the base station (gNB) transmits known Channel State Information - Reference Signals (CSI-RS) that each UE can measure and use to estimate the characteristics of the propagation channel from the gNB to the UE. The UE then uses the estimated channel characteristics to determine a suitable precoding matrix which it informs the gNB about via the precoding matrix indicator(PMI) parameter of its CSI report to the gNB. The PMI received from the UE by the gNB is only a suggestion of a suitable precoder that the gNB may or may not use in practice. In 5G NR, the gNB assesses such precoding matrix suggestions and decides which UEs can be multiplexed together in MU-MIMO. After this determination, the gNB decides on a suitable precoder for each of the UEs. When the gNB transmits for example, a PDSCHto the UE, it uses the selected precoder on the data resources. The PDSCH transmissions also include DM-RS which are also pre-coded with the same precoder to forestall the need to inform the UE of the choice of precoder made by the gNB in 5G NR. The UE uses the DM-RS to estimate the channel characteristics which are used to equalize the received payload symbols. As the transmitted DM-RS are also pre-coded, the UE does not have to know the precoding used for the payload symbols as the effect of the precoder would be included in the channel estimate derived from the pre-coded DM-RS. This means that the gNB does not have to inform the UE of the specific pre-coder it has used on the data and DM-RS.

[0037] The PMI is therefore used to feedback to the gNB a compressed channel description which the gNB can use to decide pairs of UEs to spatially multiplex in MU-MIMO and the precoding to use for each UE. Though compressed when compared to the channel matrix, sending the PMI from the UE to gNB still uses up a lot of signaling bits. If the dominant characteristic of the channel is known by both the UE and gNB, the amount of signaling can be reduced significantly.

[0038] In NTN, the access channel from the satellite to any ground-based UE in service is typically line of sight otherwise, the UE would not be in consistent service. Furthermore, as much of the long propagation path is through relatively free space, such propagation profiles are characterized by a Ricean distribution. This entails a relatively strong direct path component and a few reflections in the channel impulse response arising from ground-based scatterers relatively close to the UE. An example of a Ricean channel is shown in Figure 3a and discussed in more detail below. There is therefore significant correlation between reception channels between any two antennas on the same satellite to the same UE. This means that spatial multiplexing via single user MIMO (SU-MIMO) is very unlikely to increase UE throughput. However, the direct component of the Ricean channel that characterizes the satellite to UE’s line of sight channels is influenced by such channel propagation characteristics as rain, cloud and particulate absorption, ionospheric reflections etc. These characteristics are likely to be different between geographical locations that are far enough apart on the surface of the earth [4] . Given that each satellite beam footprint on earth can cover 100s of kilometers square, there would likely be many UEs covered by the same satellite beam footprint with significantly different Ricean factors and different local scatterers. For any two such UEs, the channel characteristics at the receiver are therefore expected to be significantly different (uncorrelated). There are therefore spatial multiplexing gains to be exploited by multiplexing such UEs onto the same transmission resources for example using MU-MIMO [5], By sharing access channel transmission resources between more than one UE, connection densities can increase. Connection density is the number of UEs that can be served simultaneously within each satellite beam footprint.

[0039] This scenario raises the following question:

[0040] • In terrestrial networks (TN), UEs can measure and feedback CSI to the network via which the network can, through computing the correlation between channels to pairs of UEs, decide which two UEs can be multiplexed on the same transmission resources using MU-MIMO. In NTN, because of the long propagation delays between the UE and the base station, such measurements and reporting can take so long that the level of channel correlation between the two UEs can change significantly between measurement and reporting. This is particularly acute in LEO and VLEO based systems in which the satellite orbital speed is very high. Limiting the signaling information in the feedback would help to shorten the feedback time (e.g. in the sense that, assuming a fixed data rate, shorter messages take less time to transmit). How can this be done?• In legacy NR, reciprocity-based MIMO operation has been introduced. In reciprocity-based MIMO, a UE sends SRS (sounding reference signal) instead of PMI feedback. The gNB estimates the UL channel using the received SRS. Channel reciprocity is the assumption that the DL channel can be inferred from the UL channel when DL and UL use the same frequency band for example in TDD. However, when NTN operates in TDD, channel reciprocity is not generally available and so it would be difficult to carry out reciprocity-based MIMO operations.

[0041] These issues are addressed in this disclosure. Embodiments of the present technique can provide a method of communicating by an NTN part of a wireless communications network with a plurality of communications devices. The method comprises transmitting, from a satellite of the NTN part radio signals for reception on the downlink by a first communications device and a second communications device multiplexed in co-scheduled communications resources using a plurality of antennas mounted on the satellite according to a MU-MIMO scheme, and / or receiving radio signals transmitted on the uplink by the first and the second communications devices multiplexed in co-scheduled up-link communications resources using the plurality of antennas according to the MU-MIMO scheme. The radio signals are transmitted or received using the plurality of antennas according to the MU-MIMO scheme using precoding vectors of coefficients for each of the first and the second communications devices for the plurality of antennas when the first and second communications devices have sufficiently uncorrelated radio channel impulse responses.

[0042] Model of MU-MIMO Transmission and Reception

[0043] Eigure 2 shows a model of MU-MIMO transmission on the downlink (DL), corresponding to the example embodiment shown in Figure 1 with two antennas 38.1, 38.2 on the satellite 22 and two UEs 16.1, 16.2 multiplexed together. This represents a 2x2 MU-MIMO set up, which is only an example. In general, it can be an MxQ set up where M is the number of transmit antennas at the gNB or satellite 22 and Q is the number of antennas at the UEs multiplexed together on the same transmission resources and M > Q. The model of this 2x2 MU-MIMO transmission is:

[0044] Y = HX + N

[0045] where each ofY, H, X and N are matrices. For the 2x2 model of Figure 2, the dimensions are as follows:

[0046] • Y the received vector (considering both UEs) is a (2x1),

[0047] • H the channel matrix is a 2x2

[0048] • X the input vector is a 2x1

[0049] • N the noise vector is a 2x1

[0050] The matrix H - is of the form:

[0051]

[0052] Note that because in this example, each UE is to receive only one stream, each UE can potentially have only one antenna, but the UE can have more than one antenna. In classical MIMO, the best precoder vector P to use at the transmitter, which in this case is the satellite, is one that maximises the capacity such that:

[0053] P = argmax \

[0054]

[0055] Where H is the estimate for H computed from reference signals (e.g. CSI-RS) that are orthogonal between transmit antennas, P is the candidate precoder vector, IF is a vector of the receiving antenna weights and equal to 1 if the number of receiving antennas is 1, and o2is the noise variance. W depends on the SINR with respect to each UE and can be computed for each UE from its CQI report to the gNB. In legacy systems, there is a codebook of precoders P, the entries of which can be used each in turn to calculate Equation (1). The process culminates with the choice of the codebook entry P that maximises the capacity in Equation (1). The precoding vector P may also be determined through calculation by using the channel matrix H when a good estimate H is known at the gNB. For example, if a Zero Forcing (ZF) receiver processing function at the UE is assumed, then the gNB can calculate the precoding vector using Equation (2):

[0056] P = HH(HHHy (2)

[0057] In this case, the need for a precoding vector codebook can be forestalled.

[0058] For an example in which the channel impulse response of the channel is Ricean (as illustrated in Figure 3a) then, according to [6], when the channels are Ricean, the matrix H can be determined as in Equation (3):

[0059]

[0060] Where HLis the specular (direct) path of the channel, Hwis derived from the scattered components of the channel impulse response and K is the Rice factor being the ratio between \HL|2and

[0061]

[0062] I2. This suggests that a good estimate for H can be computed if K, HLand Hware known.

[0063] MU-MIMO Based on a Separation Between UEs

[0064] UEs That Are Far Apart Enough Can Be Multiplexed

[0065] The channel from the satellite to a UE in service is mainly LoS (line of sight) and Ricean as illustrated in Figure 3a. This means that there is hardly any or at least reduced multipath propagation to each UE and so if two UEs are far enough apart, the fading of the respective specular components is likely to be uncorrelated. According to [5] such UEs with uncorrelated fading can be spatially multiplexed. According to example embodiments, to assess whether two UEs can be multiplexed together in MU-MIMO, the network computes the spatial distance between the two UEs from their respective locations and may also compute their respective azimuth angles from the satellite. The azimuth is taken into account because UEs at the same or similar azimuth to the satellite may indeed be subject to the same atmospheric conditions (for example, the paths to each of the UEs may pass through the same rain cloud). Depending on the extent of the spatial distance between the UEs and the difference in the azimuths to the satellite, the network can determine that the channels to the UEs are not correlated and so the UEs can be multiplexed together, otherwise they are not. Note that MU-MIMO for such UEs would then be applicable to both downlink and uplink transmissions. Note further that UEs at a similar azimuth to the satellite may experience more correlated channels and so are not amenable to spatial multiplexing.

[0066] From the UE point of view, it is not necessary for a UE (a first UE) to recognize or identify another UE (a second UE) which is decided as a paired UE for MU-MIMO (although the first UE can do that). For example, the spatial distance between the two UEs is decided based on the UE location report sent from each UE. In this case, the network may transmit, respectively to two UEs, configuration information used for the UE location report, the configuration information may comprise at least one of: reference point information, or threshold value. The UE (each of first UE and second UE) may calculate a distanceinformation between the reference point and its own location and may report the calculated distance information to the network. The network may calculate the spatial distance between the two UEs based on the reported location information of the first UE and the second UE. For the respective azimuth angles from the satellite, a similar mechanism may be applied. For example, each of the first UE and the second UE may report its own azimuth angle from the satellite to the network. And then, the network may calculate their respective azimuth angles from the satellite.

[0067] Disabling Some Feedback Information (PMI, CRE SSB Index)

[0068] According to some embodiments, a UE is configured, when communicating via the NTN part, not to feedback some of the customary information from CSI measurement, such as PMI (Precoding Matrix Indicator) and / or CRI (CSI-RS Resource Indicator). This is because such feedback information may not be useful due to the long delay and the high orbital speed in NTN. For this example, the UE is configured to feedback CQI and / or L1 / L2 -position related information (described below), or not to feedback any CSI report, i.e., a higher layer parameter reportQuantity in CSI-ReportConfig is set to ‘CQI’, ‘position’, or ‘none’. By not feeding back all of the traditional CSI information, a UE can reduce CSI signalling load and the limited remaining information can be fed back much faster.

[0069] In another embodiment, in place of the omitted CSI feedback information, a UE sends instead an indication of the main specular and the diffused components of its Ricean channel - HLand Hwin Equation (3) for each transmit antenna. The gNB can use the location, azimuth of the UEs and this information for example in Equation (3) to derive the channel matrix H and then employ Equation (1) or Equation (2) to determine a suitable precoding matrix for each UE.

[0070] In the above embodiment, there are NTX complex values of HLand NTX sets of Hw(one each per transmit antenna or transmission layer), where NTX is the number of transmit antennas or layers from the gNB. In some further embodiments, the UE processes this data to minimise the number of bits needed for its transmission.

[0071] Figures 4a, 4b, and 4c show example channel impulse responses consisting of the specular component HL and the set of scattered components H. for one of the NTXtransmit antennas.

[0072] According to the embodiment of Figure 3, a UE compresses a representation of the channel impulse response (Ricean channel) into a compressed form, where example compressed forms are shown in Figure 3b and Figure 3c. Compression is applied to each of the diffuse channel components Hwto form an Hwwith compressed channel coefficients for the diffused components. Example compression techniques include:

[0073] Hwcontains a limited number of paths (e.g. three paths) and the UE chooses which three paths to apply (e.g. compresses a five tap channel into three taps), as shown in Figure 3b. As an example, the UE chooses only the three most prominent diffuse paths in the impulse response.

[0074] Hwis formed from a single tap that is closest to the actual set of dispersed paths (e.g. the reported tap is a weighted mean or sum of the actual measured channel impulse response), as shown in Figure 3c.

[0075] Hwis reported from a codebook. The codebook consists of N entries and the UE reports the codebook entry that is most similar to the measured channel.Hwis reported from a codebook. The UE reports the codebook entry that will maximise some metric (e.g. channel capacity, system throughput etc). This can therefore provide compression of the communicated representation of the channel impulse response.

[0076] In an embodiment containing codebooks, the codebooks combine an HL component and an Hwcomponent.

[0077] In an embodiment, the HL component is compressed:

[0078] If the two transmit antennas are close on the satellite, the UE sends a single channel coefficient (since the channels from each antenna to the UE are likely to be similar), otherwise the UE sends HL channel coefficients related to each transmit antenna.

[0079] o The “closeness” can be defined by some threshold (e.g. if antennas are closer than x then send one value for HL, otherwise send two values).

[0080] o Note that the transmit antennas can be on different satellites in order to increase the separation between two transmit antennas. For example, one satellite can follow another satellite in orbit with an inter-satellite link (ISL) between satellites. The two satellites can then be considered to operate as a single virtual satellite with antennas that are separated by the distance of the ISL.

[0081] Location Reporting at Trigger Event that Location of the UE is Changed

[0082] In one embodiment, in order that gNB determines UE pairs for MU-MIMO, UEs send their own location information which is slow changing information. To reduce reporting overhead, UEs send it for this purpose only when requested by the network. In another embodiment, the UE can be configured to report its location when a triggering event such as a significant change in its location occurs. The event is defined as a distance from a reference location (e.g. the reference location is a previous location when the UE previously reported its location) to the UE’s current location exceeding a threshold configured to the UE by the network. Pre-pair multiplexable UEs

[0083] In one embodiment, the network regularly pre-pairs all UEs in RRC-CONNECTED or RRC -INACTIVE mode within the beam footprint into multiplexable pairs by assessing their spatial separation and azimuths to the satellite from their current locations and that of the satellite from its ephemeris information and determining whether the UEs can be multiplexed together when co-scheduled. In this embodiment, UE pairings for each pair are reassessed whenever a member of the pair changes location beyond a certain threshold or after a set time has elapsed.

[0084] In an example embodiment, UEs are pre-paired based on the success of previous MU-MIMO transmissions. For example, if UE1 and UE2 were paired previously and they successfully received PDSCH, those UEs are eligible for pairing in the future. This may be subject to a condition that they have not moved significantly since that successful PDSCH reception. However, if a previous pairing of UE1 and UE3 led to errored PDSCH previously, those UEs are not paired in the future unless the positions of one or both changes significantly.

[0085] This technique according to example embodiments can be extended to making pairing decisions based on the success of previous pairings and the precoder vectors used for those previous pairings. For example, if in a previous pairing of UE1 and UE3, precoder vectors Pl and P2 were used and this combination led to failure, this pairing and associated set of precoder vectors is not used in future. However, UE1 and UE3could be paired in the future if use of precoder vectors P3 and P4 had previously led to successful PDSCH decoding.

[0086] From UE point of view, it is not necessary for a UE (a first UE) to recognize or identify another UE (a second UE) which is decided as a paired UE for MU-MIMO.

[0087] Assess UEs’ Multiplexability Only When They are Co-scheduled

[0088] In other embodiments, the network only assesses pairing for particular UEs when two or more UEs in the set are to be co-scheduled. To assess whether or not two UEs can be multiplexed together, the network requests a location report from each candidate UE. The location report may be requested if the network either does not yet know the UE’s location or a set amount of time has elapsed since the location was last reported. The network uses the reported or known locations of the UEs and the current location of the satellite from its ephemeris information to compute the spatial distance between the two UEs and their respective azimuths to the satellite. If the separation distance and azimuth difference are sufficient, it is considered that the UEs can be multiplexed together.

[0089] From UE point of view, it is not necessary for a UE (a first UE) to recognize or identify another UE (a second UE) with which it is multiplexed.

[0090] Determining “apart enough”

[0091] In one embodiment, the network compares the spatial distance and azimuth difference calculated against set thresholds and if the calculated spatial distance and azimuth differences are each greater than their respective thresholds, then the two UEs are spatially multiplexable using MU-MIMO with an expectation that the UEs are so far apart that their channels are not correlated otherwise they are not multiplexed together.

[0092] In one embodiment, the network may use angle of arrival (AoA) of the UL transmissions to estimate the difference of direction or azimuth of the UEs that are being considered for pairing.

[0093] What to Consider in Setting the “apart enough” Threshold

[0094] According to example embodiments, the threshold for spatial separation is set considering the average diameter of local rainfall, clouds or other atmospheric precipitation. In other words, if UEs are separated by a distance that is larger than the diameter of typical rain clouds in the locality, then it is highly likely that the propagation channels to the two UEs are uncorrelated.

[0095] Transmission of Occasional PMI Feedback

[0096] Although full PMI feedback may not be useful due to the long delay in the feedback, since the propagation radio channel is likely to be Ricean with a strong K-factor (direct component), then it may not deviate much. Occasional PMI feedback can provide information to the gNB, to determine if the distance separation between the initial paired UEs provides sufficient spatial separation for MU-MIMO.

[0097] Fallback If Precoding Fails

[0098] Once UEs are paired, the network monitors link quality via HARQ and other measurements such as AoA, SRS, occasional CSI-RS measurements for example, and can act if the pairing is resulting in link quality degradation. If link quality degradation beyond a set threshold is determined (for example the link quality can be measured using the number of NACKs within a set period), or any explicitly fed back PMI issignificantly different from the calculated precoder in use, the network can either change precoders or discontinue the multiplexing between these particular paired UEs and assesses other UEs to pair.

[0099] L1 / L2 -position information feedback

[0100] In one embodiment, a UE may send information of its own position. Based on the position, the network can appropriately update the UE’s position and decide whether UEs are far apart enough to schedule MU-MIMO. In conventional arrangements, UE position information could be sent via L3 layer. In this embodiment, UE position related information is sent via L1 / L2 layer e.g., using UCI or MAC CE so that their positions can be updated in a more-timely manner.

[0101] In some embodiments, L1 / L2 -position information are latitude, longitude, and altitude in a global coordinate system.

[0102] In some embodiments, L1 / L2 -position information is a difference of position compared to a second position. In an example, the second position is the previous position that the UE had communicated to the network. In another example, the second position is a reference location, where the reference location may for example be the centre of a beam and that reference location may be signalled to UEs. To send difference information only, feedback overhead can be compressed.

[0103] Summary of Operation

[0104] A summary of operation of the NTN system according to example embodiments is presented in Figure 4. The operation of the NTN part may be performed in the satellite 22, the ground station or ground station 20, or indeed may be performed on an infrastructure equipment of the wireless communications network. For simplicity, this will be referred to as just the NTN part although it may not be limited to the satellite 22 and ground / earth station 20. As shown in Figure 4, as a first step SI, the NTN part determines a location of each of the UEs within a coverage area of the spot beam forming a cell of the NTN. The location may be determined for example using the GNSS system and may be updated by the wireless communications network as a background task. The UEs monitor and report their respective locations which are reported to the wireless communications network. The UEs may continuously monitor their location so that if there is a change in a location of any of the UEs, the location of the UEs can be updated. Once the NTN part has the location of the UEs within the NTN cell, in step S2, the NTN part forms the UEs into pairs based on their respective locations with the effect that the channel impulse response of each pair of respective UEs are sufficiently decorrelated so that the pair can be spatially multiplexed in co-scheduled communications resources such as a PDSCH transmission resource. Once the UEs are paired, then precoder coefficients can be calculated for respective uplink and downlink transmissions for each respective UE. Therefore, for example in step S3, the NTN part / satellite is configured to transmit radio signals on the downlink for each of the UEs in the co-scheduled communications resources using a plurality of antennas according to an MU-MIMO scheme. Correspondingly in step S4, for the uplink, the NTN part calculates precoder coefficients for the plurality of antennas and then uses the receiver chains to receive signals transmitted from each of the UEs of the pair according to an MU-MIMO scheme. As explained above, by pairing the UEs based on their relative location, there is a greater likelihood that the radio channels will be uncorrelated between the respective pair so that these can use the same communications resources thereby improving communications efficiency and connection densities within the cell. In step S5, the NTN part monitors an error rate of data communicated by respective uplink and downlink channels to and from the UEs for each of the UE pairs. If the channel deteriorates then transmission / reception parameters for each UE can be updated in respect of pairing the UEs, recalculating the precoder coefficients or falling back to a Single Input Single Output, SISO.Base stations, which are an example of network infrastructure equipment, may also be referred to as transceiver stations, nodeBs, e-nodeBs, eNB, g-nodeBs, gNBs and so forth. In this regard different terminology is often associated with different generations of wireless telecommunications systems for elements providing broadly comparable functionality. However, certain embodiments of the disclosure may be equally implemented in different generations of wireless telecommunications systems, and for simplicity certain terminology may be used regardless of the underlying network architecture. That is to say, the use of a specific term in relation to certain example implementations is not intended to indicate these implementations are limited to a certain generation of network that may be most associated with that particular terminology. Systems incorporating 5G / NR and 6G technology are expected to support different services (or types of services), which may be characterised by different requirements for latency, data rate and / or reliability. For example, Enhanced Mobile Broadband (eMBB) services are characterised by high capacity with a requirement to support up to 20 Gb / s. The requirements for Ultra Reliable and Low Latency Communications (URLLC) services are for one transmission of a 32 byte packet to be transmitted from the radio protocol layer 2 / 3 SDU ingress point to the radio protocol layer 2 / 3 SDU egress point of the radio interface within 1 ms with a reliability of 1 - 10'5(99.999 %) or higher (99.9999%). Massive Machine Type Communications (mMTC) is another example of a service which may be supported by NR-based communications networks. In addition, systems may be expected to support further enhancements related to Industrial Internet of Things (IIoT) in order to support services with new requirements of high availability, high reliability, low latency, and in some cases, high-accuracy positioning.

[0105] An example configuration of a wireless communications network typically includes a plurality of transmission and reception points (TRPs) connected to distributed control units (DUs) by a connection interface. Each of the TRPs is arranged to transmit and receive signals via a wireless access interface within a radio frequency bandwidth available to the wireless communications network. Thus, within a range for performing radio communications via the wireless access interface, each of the TRPs, forms a cell of the wireless communications network. As such, wireless communications devices 16, which are within a radio communications range provided by the cells, can transmit and receive signals to and from the TRPs via the wireless access interface. Each of the distributed units are connected to a central unit (CU) (which may be referred to as a controlling node) via an interface. The central unit is then connected to the core network 10 which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network. The TRPs, the DU and CU may in part have a corresponding functionality to a base station or eNodeB of an LTE network or a gNB for 5G. It will be appreciated therefore that operational aspects of a new RAT network (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be different to those known from LTE or other known mobile telecommunications standards. However, it will also be appreciated that each of the core network component, base stations and communications devices of anew RAT network will be functionally similar to, respectively, the core network component, base stations and communications devices of a wireless communications network. The term network infrastructure equipment / access node may be used to encompass these elements and more conventional base station type elements of wireless telecommunications systems. Depending on the application at hand the responsibility for scheduling transmissions which are scheduled on the radio interface between the respective distributed units and the communications devices may he with the controlling node / central unit and / or the distributed units / TRPs. A communications device within the coverage area of a communication cell may thus exchange signalling with the central unit via one of the distributed units / TRPs associated with the communication cell.

[0106] Although reference has been made above to 4G / LTE and 5G NR, it will be appreciated that the present disclosure is applicable to future generations of wireless communications technology including 6G. In the case of 6G, a base station, which is an example of network infrastructure equipment, may also referred toas 6G NB (6G Node B), 6G RAN node, and so forth. In 6G, the core network 10 may be one or more network functions.

[0107] Although reference has been made above to NTN, it will be appreciated that the present disclosure is applicable to another network including the terrestrial network. For example, but not limited to, if the another network has long delay between the network and the UE(s) which is similar to the NTN disclosed herein, the present disclosure is applicable to the another network which is not NTN.

[0108] 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:

[0109] Paragraph 1. A method of communicating by a Non-Terrestrial Network, NTN, part of a wireless communications network with a plurality communications devices, comprising one or both of transmitting, from an air borne or space borne satellite of the NTN part, radio signals for reception on the downlink by a first communications device and a second communications device multiplexed in co-scheduled communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, or receiving radio signals transmitted on the uplink by the first and the second communications devices multiplexed in co-scheduled communications resources using the plurality of antennas according to the MU-MIMO scheme, wherein the radio signals are transmitted or received using the plurality of antennas according to the MU-MIMO scheme using precoding vectors of coefficients for each of the first and the second communications device for the plurality of antennas when the first and second communications devices have sufficiently uncorrelated radio channel impulse responses.

[0110] Paragraph 2. A method of paragraph 1, wherein the first and second communications devices have sufficiently uncorrelated radio channel impulse responses when a difference between the relative location of the first communications device (UEs, 16, 16.1, 16.2) with respect to the second communications device (UEs, 16, 16.1, 16.2) is sufficiently large that the first and the second communications devices can be spatially multiplexed in co-scheduled communications resources.

[0111] Paragraph 3. A method of paragraph 2, wherein the first and second communications devices have sufficiently uncorrelated radio channel impulse responses when one or both of

[0112] a distance which separates the first and the second communications devices exceeds a predetermined threshold, and

[0113] an azimuth angle of transmission of radio signals from the first and the second communications devices to the satellite or reception of radio signals at the first and the second communications devices from the satellite differs by a predetermined amount.

[0114] Paragraph 4. A method of paragraph 3, wherein the predetermined threshold of the distance of separation of the first and the second communications devices is determined from prevailing atmospheric conditions or weather patterns.

[0115] Paragraph 5. A method of paragraph 3 or 4, wherein the predetermined amount by which the azimuth angles differ for the first and the second communications devices is determined from prevailing atmospheric conditions or weather patterns.

[0116] Paragraph 6. A method of any of paragraphs 1 to 5, comprising

[0117] determining, based on a relative location of the first communications device (UEs, 16, 16.1, 16.2) with respect to the second communications device (UEs, 16, 16.1, 16.2), that the first and the second communications devices have sufficiently uncorrelated radio channel impulse responses and can be spatially multiplexed in co-scheduled communications resources.

[0118] Paragraph 7. A method of paragraph 6, comprising

[0119] receiving a location of the first communications device from the first communications device, receiving a location of the second communications device from the second communications device, and

[0120] based on the relative difference in location of the first and the second communications devices determining that the first and the second communications devices have sufficiently uncorrelated radio channel impulse responses and can be spatially multiplexed in co-scheduled communications resources. Paragraph 8. A method of paragraph 5, comprising

[0121] configuring transceiver circuitry of the satellite of the NTN part for one or both oftransmiting the radio signals to be received on the downlink by the first and the second communications devices in the co-scheduled communications resources using the plurality of antennas mounted on the satellite according to the MU-MIMO scheme, or

[0122] receiving the radio signals transmited on the uplink by the first and the second communications devices in the co-scheduled communications resources using the plurality of antennas according to the MU-MIMO scheme,

[0123] wherein the configuring the transceiver circuitry includes calculating precoder vectors of coefficients for the MIMO scheme for each of the first and the second communications devices for the plurality of antennas.

[0124] Paragraph 9. A method of paragraph 8, comprising

[0125] receiving an updated location of the first communications device from the first communications device,

[0126] receiving an updated location of the second communications device from the second communications device,

[0127] determining that one or both of the location of the first and the second communications devices has changed, and

[0128] based on the change of the relative location of the first and the second communications devices, recalculating the precoder vectors of coefficients for the MIMO scheme for each of the first and the second communications devices for the plurality of antennas.

[0129] Paragraph 10. A method of any of paragraphs 1 to 9, wherein the transmiting the radio signals multiplexed in the co-scheduled communications resources for the first communications device comprises precoding with a first vector of coefficients for transmission via the plurality of antennas of the transmited radio signals forming a first multiplexed layer, and the transmiting the radio signals multiplexed in the co-scheduled communications resources to the second communications device comprises precoding with a second vector of coefficients for transmission via the plurality of antennas of the transmited radio signals forming a second multiplexed layer.

[0130] Paragraph 11. A method of any of paragraphs 1 to 9, wherein the receiving the radio signals multiplexed in the co-scheduled communications resources from the first communications device comprises precoding with a first vector of coefficients for reception via the plurality of antennas of the received radio signals forming a first multiplexed layer, and the receiving of the radio signals multiplexed in the co-scheduled communications resources from the second communications device comprises precoding with a second vector of coefficients for reception via the plurality of antennas of the received radio signals forming a second multiplexed layer.

[0131] Paragraph 12. A method of paragraph 10 or 11, comprising

[0132] receiving first channel feedback information from the first communications device, the first channel feedback information representing a channel impulse response of the radio channel between the first communications device and the satellite,

[0133] receiving second channel feedback information from the second communications device, the second channel feedback information representing a channel impulse response of the radio channel between the second communications device and the satellite, and

[0134] calculating the first and second precoder vectors of coefficients for the first and second communications devices based on the first channel feedback information and the second channel feedback information.

[0135] Paragraph 13. A method of paragraph 12, wherein the first and the second channel feedback information representing the channel impulse response for the first and the second communications devices comprise a representation of a main path corresponding to a Ricean profile and one or more paths corresponding to reflected paths which are less than a total number of reflected paths of the channel impulse response.Paragraph 14. A method of paragraph 12 or 13, wherein the first and second channel feedback information comprise a compressed representation of the channel impulse response represented as a codebook entry.

[0136] Paragraph 15. A method of any of paragraphs 8 to 14, comprising

[0137] determining a performance of data transmission to the first communications device and data reception from the first communications device,

[0138] determining a performance of data transmission to the second communications device and data reception from the second communications device, and

[0139] based on the determined performance re-calculating the first and the second precoding vectors of coefficients for the first and second communications devices from the one or both of the performance of the data transmission and the data reception of the first and the second communications devices.

[0140] Paragraph 16. A method of any of paragraphs 1 to 14, comprising

[0141] determining a performance of data transmission to the first communications device and data reception from the first communications device,

[0142] determining a performance of data transmission to the second communications device and data reception from the second communications device, and

[0143] based on the determined performance, transmitting radio signals for reception on the downlink by the first communications device and the second communications device in separate scheduled communications resources using the plurality of antennas according to a Single Input Single Output, SISO scheme, or

[0144] receiving radio signals transmitted on the uplink by the first and the second communications devices in separately scheduled communications resources using the plurality of antennas according to the SISO scheme.

[0145] Paragraph 17. A method of any of paragraphs 8 to 16, wherein the first and second precoding vectors of coefficients for the first and second communications devices are calculated by an infrastructure equipment of the wireless communications network.

[0146] Paragraph 18. A method of paragraph 17, wherein the infrastructure equipment is part of the NTN. Paragraph 19. A method of paragraph 17, wherein the first and second vectors of coefficients for the first and second communications devices are calculated by the satellite of the NTN part of the wireless communications network.

[0147] Paragraph 20. A method of operating a communications device to transmit or to receive radio signals via a Non-Terrestrial Network, NTN, part of a wireless communications network, the method comprising transmitting an indication of a location of the communications device to the NTN part, and one or both of

[0148] transmitting radio signals, by the communications device to an air borne or space borne satellite of the NTN part, the radio signals for reception on the uplink multiplexed in communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, the communications resources being for co-scheduling with another communications device, and

[0149] receiving radio signals by the communications device transmitted from the satellite on the downlink, the radio signals transmitted on the downlink by the satellite in communications resources using the plurality of antennas mounted on the satellite according to the MU-MIMO scheme, the communications resources being for co-scheduling with another communications device, wherein the radio signals are transmitted or received using the plurality of antennas according to the MU-MIMO scheme using precoder vectors of coefficients based on the location of the communications device.

[0150] Paragraph 21. A method of paragraph 20, wherein the precoder vectors of coefficients of the MU-MIMO scheme are calculated for the transmission and the reception of the radio signals based on the location of the communications device and the location of the other communications device with alikelihood that the communications device and the other communications devices have sufficiently uncorrelated radio channel impulse responses.

[0151] Paragraph 22. A method of paragraph 20 or 21, comprising

[0152] determining, by the communications device, an impulse response of a radio channel between the communications device and the satellite,

[0153] forming a compressed representation of the measured radio channel impulse response, and transmitting the compressed representation of the measured radio channel impulse response. Paragraph 23. A method of paragraph 22, wherein the radio channel impulse response comprises a direct path component (HL) and multipath components (Hw) produced by a plurality of reflected paths, and the forming the compressed representation of the measured radio channel impulse response comprises representing the multipath component as a reduced number of paths by combining an effect of one or more of the paths.

[0154] Paragraph 24. A method of paragraph 20, wherein the indication of the location of the communications device is transmitted to the wireless communications network for determining a relative difference in a location of the communications device with respect to the other communications device with which the communications device is paired so that the communications device and the other communications device have a sufficiently uncorrelated radio channel impulse responses when the relative location is sufficiently large that the radio signals can be spatially multiplexed in the co-scheduled communications resources. Paragraph 25. A Non-Terrestrial Network, NTN, part of a wireless communications network for communicating with a plurality communications devices, the NTN part comprising a satellite and a ground station, the ground station providing a wireless back channel with the satellite and for communicating between the satellite and a core network of the wireless communications network, the satellite comprising

[0155] transceiver circuitry configured with the ground station to perform one or both of transmitting, from an air borne or space borne satellite of the NTN part, radio signals for reception on the downlink by a first communications device and a second communications device multiplexed in co-scheduled communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, and receiving radio signals transmitted on the uplink by the first and the second communications devices multiplexed in co-scheduled communications resources using the plurality of antennas according to the MU-MIMO scheme, wherein the radio signals are transmitted or received using the plurality of antennas according to the MU-MIMO scheme using precoding vectors of coefficients for each of the first and the second communications device for the plurality of antennas when the first and second communications devices have sufficiently uncorrelated radio channel impulse responses.

[0156] Paragraph 26. A communications device (UE, 16) for transmitting or to receiving radio signals via a Non-Terrestrial Network, NTN, part of a wireless communications network, the communications device comprising

[0157] controller circuitry, and

[0158] transceiver circuitry for transmitting an indication of a location of the communications device to the NTN part controlled by the controller circuitry, and one or both of

[0159] transmitting radio signals to an air borne or space borne satellite of the NTN part, the radio signals for reception on the uplink multiplexed in communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, the communications resources being for co-scheduling with another communications device, and receiving radio signals by the communications device transmitted from the satellite on the downlink, the radio signals transmitted on the downlink by the satellite in communications resources using the plurality of antennas mounted on the satellite according to the MU-MIMO scheme, the downlink communications resources being for co-scheduling with another communications device, wherein the radio signals are transmitted or received using the plurality of antennas according to the MU-MIMO scheme using precoder vectors of coefficients based on the location of the communications device.

[0160] In so far as embodiments of the disclosure have been described as being implemented, at least in part, by software-controlled data processing apparatus, it will be appreciated that a non-transitory machine-readable medium carrying such software, such as an optical disk, a magnetic disk, semiconductor memory or the like, is also considered to represent an embodiment of the present disclosure.

[0161] It will be appreciated that the above description for clarity has described embodiments with reference to different functional units, circuitry and / or processors. However, it will be apparent that any suitable distribution of functionality between different functional units, circuitry and / or processors may be used without detracting from the embodiments.

[0162] Described embodiments may be implemented in any suitable form including hardware, software, firmware or any combination of these. Described embodiments may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. The elements and components of any embodiment may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the disclosed embodiments may be implemented in a single unit or may be physically and functionally distributed between different units, circuitry and / or processors. Although the present disclosure has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognise that various features of the described embodiments may be combined in any manner suitable to implement the technique.References

[0163] [1] 3GPP TR38.811, “Study on New Radio (NR) to support non-terrestrial networks (Release 15)”, Sept 2019.

[0164] [2] 3GPP TR38.821, “Solutions for NR to support non-terrestrial networks (NTN) (Release 16)”, Dec 2019.

[0165] [3] 3GPP TR36.763, “Study on Narrow-Band Internet of Things (NB-IoT)Zenhanced Machine Type Communication (eMTC) support for Non-Terrestrial Networks (NTN) (Release 17)”

[0166] [4] M M da Silva et al, „Ch 2 in: MIMO Processing for 4G and beyond“, CRC Press, 2014, ISBN: 13:978-1-4665-9807-2

[0167] [5] Matthaiou, M., Smith, P. J., Ngo, H. Q., & Tataria, H. (2018). “Does Massive MIMO Fail in Ricean Channels?” IEEE Wireless Communications Letters. Advance online publication. https: / / doi.org / 10.1109 / LWC.2018.2853131

[0168] [6] M Matthaiou, D Laurenson, and Cheng-Xiang Wang, “Reduced Complexity Detection for Ricean MIMO Channels Based on Condition Number Thresholding”, Proc of IWCMC 2008, IEEE

Claims

CLAIMSWhat is claimed is:

1. A method of communicating by a Non-Terrestrial Network, NTN, part of a wireless communications network with a plurality communications devices, comprising one or both of transmitting, from an air borne or space borne satellite of the NTN part, radio signals for reception on the downlink by a first communications device and a second communications device multiplexed in co-scheduled communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, or receiving radio signals transmitted on the uplink by the first and the second communications devices multiplexed in co-scheduled communications resources using the plurality of antennas according to the MU-MIMO scheme, wherein the radio signals are transmitted or received using the plurality of antennas according to the MU-MIMO scheme using precoding vectors of coefficients for each of the first and the second communications device for the plurality of antennas when the first and second communications devices have sufficiently uncorrelated radio channel impulse responses.

2. A method of claim 1, wherein the first and second communications devices have sufficiently uncorrelated radio channel impulse responses when a difference between the relative location of the first communications device (UEs, 16, 16.1, 16.2) with respect to the second communications device (UEs, 16, 16.1, 16.2) is sufficiently large that the first and the second communications devices can be spatially multiplexed in co-scheduled communications resources.

3. A method of claim 2, wherein the first and second communications devices have sufficiently uncorrelated radio channel impulse responses when one or both ofa distance which separates the first and the second communications devices exceeds a predetermined threshold, andan azimuth angle of transmission of radio signals from the first and the second communications devices to the satellite or reception of radio signals at the first and the second communications devices from the satellite differs by a predetermined amount.

4. A method of claim 3, wherein the predetermined threshold of the distance of separation of the first and the second communications devices is determined from prevailing atmospheric conditions or weather patterns.

5. A method of claim 3, wherein the predetermined amount by which the azimuth angles differ for the first and the second communications devices is determined from prevailing atmospheric conditions or weather patterns.

6. A method of claim 1, comprisingdetermining, based on a relative location of the first communications device (UEs, 16, 16.1, 16.2) with respect to the second communications device (UEs, 16, 16.1, 16.2), that the first and the second communications devices have sufficiently uncorrelated radio channel impulse responses and can be spatially multiplexed in co-scheduled communications resources.

7. A method of claim 6, comprisingreceiving a location of the first communications device from the first communications device, receiving a location of the second communications device from the second communications device, andbased on the relative difference in location of the first and the second communications devices determining that the first and the second communications devices have sufficiently uncorrelated radio channel impulse responses and can be spatially multiplexed in co-scheduled communications resources.

8. A method of claim 5, comprisingconfiguring transceiver circuitry of the satellite of the NTN part for one or both of transmitting the radio signals to be received on the downlink by the first and the second communications devices in the co-scheduled communications resources using the plurality of antennas mounted on the satellite according to the MU-MIMO scheme, orreceiving the radio signals transmitted on the uplink by the first and the second communications devices in the co-scheduled communications resources using the plurality of antennas according to the MU-MIMO scheme,wherein the configuring the transceiver circuitry includes calculating precoder vectors of coefficients for the MIMO scheme for each of the first and the second communications devices for the plurality of antennas.

9. A method of claim 8, comprisingreceiving an updated location of the first communications device from the first communications device,receiving an updated location of the second communications device from the second communications device,determining that one or both of the location of the first and the second communications devices has changed, andbased on the change of the relative location of the first and the second communications devices, recalculating the precoder vectors of coefficients for the MIMO scheme for each of the first and the second communications devices for the plurality of antennas.

10. A method of claim 1, wherein the transmitting the radio signals multiplexed in the co-scheduled communications resources for the first communications device comprises precoding with a first vector of coefficients for transmission via the plurality of antennas of the transmitted radio signals forming a first multiplexed layer, and the transmitting the radio signals multiplexed in the co-scheduled communications resources to the second communications device comprises precoding with a second vector of coefficients for transmission via the plurality of antennas of the transmitted radio signals forming a second multiplexed layer.

11. A method of claim 1, wherein the receiving the radio signals multiplexed in the co-scheduled communications resources from the first communications device comprises precoding with a first vector of coefficients for reception via the plurality of antennas of the received radio signals forming a first multiplexed layer, and the receiving of the radio signals multiplexed in the co-scheduled communications resources from the second communications device comprises precoding with a second vector of coefficients for reception via the plurality of antennas of the received radio signals forming a second multiplexed layer.

12. A method of claim 10, comprisingreceiving first channel feedback information from the first communications device, the first channel feedback information representing a channel impulse response of the radio channel between the first communications device and the satellite,receiving second channel feedback information from the second communications device, the second channel feedback information representing a channel impulse response of the radio channel between the second communications device and the satellite, andcalculating the first and second precoder vectors of coefficients for the first and second communications devices based on the first channel feedback information and the second channel feedback information.

13. A method of claim 12, wherein the first and the second channel feedback information representing the channel impulse response for the first and the second communications devices comprise a representation of a main path corresponding to a Ricean profile and one or more paths corresponding to reflected paths which are less than a total number of reflected paths of the channel impulse response.

14. A method of claim 12, wherein the first and second channel feedback information comprise a compressed representation of the channel impulse response represented as a codebook entry.

15. A method of claim 8, comprisingdetermining a performance of data transmission to the first communications device and data reception from the first communications device,determining a performance of data transmission to the second communications device and data reception from the second communications device, andbased on the determined performance re-calculating the first and the second precoding vectors of coefficients for the first and second communications devices from the one or both of the performance of the data transmission and the data reception of the first and the second communications devices.

16. A method of claim 1, comprisingdetermining a performance of data transmission to the first communications device and data reception from the first communications device,determining a performance of data transmission to the second communications device and data reception from the second communications device, andbased on the determined performance, transmitting radio signals for reception on the downlink by the first communications device and the second communications device in separate scheduled communications resources using the plurality of antennas according to a Single Input Single Output, SISO scheme, orreceiving radio signals transmitted on the uplink by the first and the second communications devices in separately scheduled communications resources using the plurality of antennas according to the SISO scheme.

17. A method of claim 8, wherein the first and second precoding vectors of coefficients for the first and second communications devices are calculated by an infrastructure equipment of the wireless communications network.

18. A method of claim 17, wherein the infrastructure equipment is part of the NTN.

19. A method of claim 17, wherein the first and second vectors of coefficients for the first and second communications devices are calculated by the satellite of the NTN part of the wireless communications network.

20. A method of operating a communications device to transmit or to receive radio signals via a NonTerrestrial Network, NTN, part of a wireless communications network, the method comprisingtransmiting an indication of a location of the communications device to the NTN part, and one or both oftransmiting radio signals, by the communications device to an air borne or space borne satellite of the NTN part, the radio signals for reception on the uplink multiplexed in communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, the communications resources being for co-scheduling with another communications device, andreceiving radio signals by the communications device transmited from the satellite on the downlink, the radio signals transmited on the downlink by the satellite in communications resources using the plurality of antennas mounted on the satellite according to the MU-MIMO scheme, the communications resources being for co-scheduling with another communications device, wherein the radio signals are transmited or received using the plurality of antennas according to the MU-MIMO scheme using precoder vectors of coefficients based on the location of the communications device.

21. A method of claim 20, wherein the precoder vectors of coefficients of the MU-MIMO scheme are calculated for the transmission and the reception of the radio signals based on the location of the communications device and the location of the other communications device with a likelihood that the communications device and the other communications devices have sufficiently uncorrelated radio channel impulse responses.

22. A method of claim 20, comprisingdetermining, by the communications device, an impulse response of a radio channel between the communications device and the satellite,forming a compressed representation of the measured radio channel impulse response, and transmiting the compressed representation of the measured radio channel impulse response.

23. A method of claim 22, wherein the radio channel impulse response comprises a direct path component (HL) and multipath components (Hw) produced by a plurality of reflected paths, and the forming the compressed representation of the measured radio channel impulse response comprises representing the multipath component as a reduced number of paths by combining an effect of one or more of the paths.

24. A method of claim 20, wherein the indication of the location of the communications device is transmited to the wireless communications network for determining a relative difference in a location of the communications device with respect to the other communications device with which the communications device is paired so that the communications device and the other communications device have a sufficiently uncorrelated radio channel impulse responses when the relative location is sufficiently large that the radio signals can be spatially multiplexed in the co-scheduled communications resources.

25. A Non-Terrestrial Network, NTN, part of a wireless communications network for communicating with a plurality communications devices, the NTN part comprising a satellite and a ground station, the ground station providing a wireless back channel with the satellite and for communicating between the satellite and a core network of the wireless communications network, the satellite comprising transceiver circuitry configured with the ground station to perform one or both of transmiting, from an air borne or space borne satellite of the NTN part, radio signals for reception on the downlink by a first communications device and a second communications device multiplexed in co-scheduled communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, andreceiving radio signals transmited on the uplink by the first and the second communications devices multiplexed in co-scheduled communications resources using the plurality of antennas according to the MU-MIMO scheme, wherein the radio signals are transmited or received using the plurality of antennas according to the MU-MIMO scheme using precoding vectors of coefficients for each of the first and the second communications device for the plurality of antennas when the first and second communications devices have sufficiently uncorrelated radio channel impulse responses.

26. A communications device (UE, 16) for transmiting or to receiving radio signals via a NonTerrestrial Network, NTN, part of a wireless communications network, the communications device comprisingcontroller circuitry, andtransceiver circuitry for transmiting an indication of a location of the communications device to the NTN part controlled by the controller circuitry, and one or both oftransmiting radio signals to an air borne or space borne satellite of the NTN part, the radio signals for reception on the uplink multiplexed in communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, the communications resources being for co-scheduling with another communications device, and receiving radio signals by the communications device transmited from the satellite on the downlink, the radio signals transmited on the downlink by the satellite in communications resources using the plurality of antennas mounted on the satellite according to the MU-MIMO scheme, the downlink communications resources being for co-scheduling with another communications device, wherein the radio signals are transmited or received using the plurality of antennas according to the MU-MIMO scheme using precoder vectors of coefficients based on the location of the communications device.

27. A Non-Terrestrial Network, NTN, infrastructure equipment comprisingtransceiver circuitry configured to perform one or both oftransmiting radio signals for reception on the downlink by a first communications device and a second communications device multiplexed in co-scheduled communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, andreceiving radio signals transmited on the uplink by the first and the second communications devices multiplexed in co-scheduled communications resources using the plurality of antennas according to the MU-MIMO scheme, wherein the radio signals are transmited or received using the plurality of antennas according to the MU-MIMO scheme using precoding vectors of coefficients for each of the first and the second communications device for the plurality of antennas when the first and second communications devices have sufficiently uncorrelated radio channel impulse responses.

28. Circuitry for a Non-Terrestrial Network, NTN, infrastructure equipment comprising transceiver circuitry configured to perform one or both oftransmiting radio signals for reception on the downlink by a first communications device and a second communications device multiplexed in co-scheduled communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, andreceiving radio signals transmited on the uplink by the first and the second communications devices multiplexed in co-scheduled communications resources using the plurality of antennas according to the MU-MIMO scheme, wherein the radio signals are transmited or received using the plurality of antennas according to the MU-MIMO scheme using precoding vectors of coefficients for each of the firstand the second communications device for the plurality of antennas when the first and second communications devices have sufficiently uncorrelated radio channel impulse responses.

29. Circuitry for transmitting or to receiving radio signals via a Non-Terrestrial Network, NTN, part of a wireless communications network, the circuitry comprisingcontroller circuitry, andtransceiver circuitry for transmitting an indication of a location to the NTN part controlled by the controller circuitry, and one or both oftransmitting radio signals to an air borne or space borne satellite of the NTN part, the radio signals for reception on the uplink multiplexed in communications resources using a plurality of antennas mounted on the satellite according to a Multiple-User, Multiple Input Multiple Output, MU-MIMO scheme, the communications resources being for co-scheduling with another communications device, and receiving radio signals transmitted from the satellite on the downlink, the radio signals transmitted on the downlink by the satellite in communications resources using the plurality of antennas mounted on the satellite according to the MU-MIMO scheme, the downlink communications resources being for co-scheduling with another communications device, wherein the radio signals are transmitted or received using the plurality of antennas according to the MU-MIMO scheme using precoder vectors of coefficients based on the location.

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