Patent Description:
The present application claims the Paris Convention priority of <CIT>.

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

There are many applications and use cases where it is desirable to be able to determine a distance and direction between communications devices. Although current wireless communications networks can provide location services which allow an absolute location (e.g. latitude, longitude, elevation) of a communications device to be determined, these have several disadvantages, and there thus arises a challenge to provide an efficient determination of distance and direction between communications devices which needs to be addressed.

<CIT> discloses that a user equipment (UE) or network device such as a Vehicle-to-everything (V2X) node, or a V2X device is configured to use sidelink signals transmitted/received with another vehicle or node with a reference that can be used for ranging and communications. The UE/device use a broadcast communication of the sidelink signals via an adaptive antenna array or direction array to form a directional radiation pattern from a beam sweeping operation based on geo-location information.

The present disclosure can help address or mitigate at least some of the issues discussed above, and accordingly the invention is defined in the appended claims.

Example embodiments of the present technique can provide a method of operating a communications device to provide a ranging-based service which uses a proximity between the communications device and at least one other communications device.

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, 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 <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.

<FIG> illustrates a more detailed illustration of a first communications device 270a and an example network infrastructure equipment <NUM>, which may be thought of as a base station <NUM> or a combination of a controlling node <NUM> and TRP <NUM>. As shown in <FIG>, the first communications device 270a is shown to transmit uplink data to the infrastructure equipment <NUM> of a wireless access interface as illustrated generally by an arrow <NUM>. The first communications device 270a 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 first communications device 270a 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 first communications device 270a 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 first communications device 270a 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, operating according to instructions stored on a computer readable medium.

<FIG> also shows a second communications device 270b which may be physically proximate to the first communications device 270a, separated from the first device 270a by a distance D, and may be configured in accordance with embodiments of the disclosure as described herein. As shown in <FIG>, the first and second communications devices 270a, 270b may communicate using signals transmitted from the first communications device 270a to the second communications device 270b as represented by arrow <NUM> and/or signals transmitted from the second communications device 270b to the first communications device 270a as represented by arrow <NUM>. Signals transmitted between the first and second communications devices <NUM>, <NUM> may form part of a side link interface between the first and second communications devices. The side link interface may be a PC-<NUM> interface for example. As shown in <FIG>, an angle θ may exist between a boresight of an antenna <NUM> of the second communications device 270b and the signals <NUM> received from the first communications device 270a. The angle θ is indicative of a direction of the second communications device 270b from the first communications device 270a.

The second communications device 270b may be configured in a similar way and have similar functionality to the first communications device 270a.

In the example of <FIG>, as described above, the first communications device 270a is configured to communicate with the infrastructure equipment <NUM>. In some embodiments, the second communications device 270b is also configured to communicate with the infrastructure equipment <NUM>. In some embodiments, the second communications device 270b is configured to communicate with a second infrastructure equipment (not shown in <FIG>), whereby the first and second infrastructure equipment form parts of different wireless communications networks.

In some embodiments, one or both of the first and second communications device 270a, 270b are not within a communication range of an infrastructure equipment with which they are configured to communicate. In some further embodiments, one or both of the first and second communications device 270a, 270b are not configured to communicate with an infrastructure equipment of a wireless communications network.

There are many applications and use cases where it would be beneficial to be able to efficiently determine an estimate of the physical separation D of an estimate of a direction between (such as the angle θ) the first and second devices 270a, 270b.

Examples, of applications in which it is beneficial to efficiently determine an estimate of a distance and direction between two communications devices include:.

Current 3GPP specifications define functionality for identifying an absolute location of a UE or communications device which is configured to operate in accordance with those specifications, and in communications with a wireless communications network operating according to those specifications. There are various positioning techniques that are specified, including:.

In addition to the applications mentioned above, it would be beneficial to efficiently determine a distance and a direction between two communications devices for ranging-based services. Ranging-based services may be defined as services which can utilise a distance and a direction between at least two communications devices for short range communications (one the order of several metres) [<NUM>]. Examples of applications of ranging-based services include developments to smart home, smart city, smart transportation, smart retail, and industry <NUM>. Such applications may have different requirements on an accuracy of the determined distance and direction and/or how quickly the distance and direction can be determined. Ranging-based services operate according to a relative distance and relative direction between communications devices and therefore do not rely on the absolute positions of the communications devices being known. Ranging-based services therefore have the benefit of not requiring deployment of positioning services by network infrastructure equipment.

Ranging-based services may be particularly beneficial in environments in which positioning information provided by network infrastructure equipment according to conventional techniques may not be available or sufficiently accurate. For example, positioning information provided by network infrastructure equipment according to conventional techniques may be inaccurate or unavailable for communications devices operating indoors.

Ranging-based services may have difference performance requirements compared to positioning information provided by network infrastructure equipment according to conventional techniques. For example, positioning performance requirements include horizontal and vertical accuracy, positioning service availability, service latency and velocity of the communications devices. By contrast, since the ranging-based services may be directed towards different applications compared to positioning information, their requirements may be different. For example, latency requirements in ranging-based services may be much more stringent. This is because determination of relative distance in ranging-based services would require much less time than determining absolute positions of the communications devices because of the additional delay introduced by using network infrastructure equipment.

Thus, referring to the example of <FIG>, there are numerous applications and use cases where an efficient means to determine a distance and a direction between the first and second communications device 270a, 270b are required.

Existing techniques can provide for a determination of an absolute location of a communications device which is configured to communicate with a wireless communications network. In the present disclosure, an absolute location is one where the location is determined relative to a fixed frame of reference. For example, a longitude/latitude pair may constitute an absolute location for a device constrained (or assumed) to be at ground level. Other examples of absolute locations may be represented by a grid reference or a unique address or postal code.

In accordance with example embodiments, a communications device may determine an indication of a direction of signals received from another communications device. In one example, the indication of the direction of the signals received from the other communications device may be an angle of arrival (AoA) of the received signals.

In accordance with example embodiments, a communications device is configured to determine an angle of arrival (AoA) of a signal by using elements of an antenna of the communications device. A time difference may be measured between different arrival points of a signal by a plurality of antenna elements in the antenna [<NUM>].

For example, in <FIG>, an incoming signal <NUM> is incident on a first <NUM> and a second <NUM> antenna element of a communications device. In some examples, the communications device may be either of the first and second communications devices 270a, 270b and the antenna comprising the first <NUM> and second <NUM> antenna element may be either of the antennae <NUM>, <NUM> of the first and second communications devices respectively 270a, 270b, 270b shown in <FIG>. In such examples, the incoming signal <NUM> may be a signal between the first and second communications devices 270a, 270b as represented by arrows <NUM> and <NUM> in <FIG>.

As shown in <FIG>, an incoming signal arrives at a point A corresponding to the first antenna element <NUM> and a point C corresponding to the second antenna element <NUM>. An incoming signal arriving at two different antenna elements, such as the first and second elements <NUM>, <NUM>, may be referred to herein as different versions of the same incoming signal. In the example of <FIG>, an angle θ exists between the incoming signal <NUM> and a boresight <NUM> of the second antenna element <NUM>. For the example in <FIG>, the angle θ is measured positively anti-clockwise from the boresight of the second antenna element for the range <NUM>° ≤ θ < <NUM>°.

It will be appreciated by one skilled in the art that the boresight of an antenna element is an axis of maximum gain for a directional antenna element. It will be appreciated from <FIG> that a boresight of the first antenna element <NUM> (not shown) is along the same axis as the boresight <NUM> of the second antenna element <NUM>.

In <FIG> a time of arrival of the incoming signal at the first and second antenna elements <NUM>, <NUM> are different from each other provided θ ≠<NUM>° or <NUM>°. If θ = <NUM>° or <NUM> °, then the time of arrival of the incoming signal at the first and second is the same.

As shown in <FIG>, the first and second antenna elements <NUM>, <NUM> are physically separated in the antenna by a distance d. At the time of arrival of the incoming signal <NUM> at the first antenna element <NUM>, the incoming signal <NUM> must still propagate through a distance dsinθ before reaching the second antenna element <NUM>. Accordingly, dsinθ is a path difference between the incoming signal <NUM> arriving at the first and second antenna elements <NUM>, <NUM>. As will be appreciated by one skilled in the art, for an incoming signal <NUM> of wavelength λ and a path difference of dsinθ, a phase difference, Δφ, between the arrival of the incoming signal <NUM> at the first and second antenna elements <NUM>, <NUM> may be represented by Equation <NUM>.

In example embodiments, a communications device comprising the first and second antenna elements <NUM>, <NUM> may receive the incoming signal <NUM> from another communications device. In such embodiments, the communications device may be configured to measure the phase difference, Δφ, between the arrival of the incoming signal <NUM> at the first and second antenna elements <NUM>, <NUM>. In such embodiments, the wavelength of the incoming signal λ and the distance, d, between the first and second antenna elements <NUM>, <NUM> may be known to the communications device. Therefore the communications device may compute the angle θ from Equation <NUM> which is a rearrangement of Equation <NUM>.

In such embodiments, the angle θ may be referred to as the AoA of the incoming signal <NUM> to the communications device.

In example embodiments, an accuracy of AoA calculations may be improved by accounting for multipath signals (for example, delayed reflected signals) by using algorithms such as MUSIC (Multipath Signal Classification) [<NUM>].

Therefore, in accordance with example embodiments, a communications device may use an incoming signal to determine an AoA of an incoming signal to a communications device.

As will be appreciated by those acquainted with radio communications and in particular <NUM>/NR, beam steering is a technique in which transmitted signals may be focused into a beam in a particular direction by transmitting a different version of the same signal from different antennae and adjusting a phase of the each version of the transmitted so that the transmitted versions combine coherently into a beam. Accordingly a communications device or a gNB equipped with an antenna array can form a beam and steer the beam by focusing the beam in a particular direction by adjusting the phase of the different versions of the signal. Correspondingly, a communications device or gNB can receive signals in a particular direction as a beam by adjusting a phase of different versions of a signal received by each antenna so as to combine coherently.

As will be appreciated therefore beam steering techniques can also be applied to direct a beam in a direction of a transmitter/receiver which can also be used to detect an AoA of a transmitted or received signal. According to example embodiments, an AoA of signals is detected by one communications device from another communications device from signals transmitted via a side link interface. Currently although beam steering has been proposed between a communications device and a gNB for <NUM>/NR, it is not specified for sidelink communications, although those skilled in the art will appreciate that beam steering techniques can be used for sidelink communications in order to extract AoA indications.

In accordance with example embodiments, a communications device may determine a distance between the communications device and another communications device.

In example embodiments, a communications device may use a one-way propagation delay for a signal transmitted to the other communications device to determine the distance between the communications devices. For example, a communications device may determine the one-way propagation delay, t, and use the one-way propagation delay, t, in combination with the speed of light in a vacuum, c, at which the signal is assumed to be travelling, and determine the distance, s, between the communications devices from Equation <NUM>.

Other distance measurement techniques are disclosed in our co-pending European Application, <CIT>.

As discussed above, it is possible for a communications device to determine a distance and direction between itself and another communications device without relying on positioning information provided by network infrastructure equipment. In some examples, the distance and direction may be used in ranging-based services.

However, there is no guarantee that a communications device will be able to determine the distance and direction between itself and another communications device. For example, the communications device may not have access to information which it can use to determine the distance and direction of another communications device from the communications device. In one example, a user of a communications device may select to initiate a ranging-based service using an application on the communications device. However, if the communications device does not have access to information which it can use to determine the distance and direction of the communications device, then the ranging-based service cannot be initiated.

Example embodiments of the present technique can provide a method of operating a communications device to provide a ranging-based service which uses a proximity between the communications device and at least one other communications device. The method comprises transmitting, by transceiver circuitry in the communications device, a discovery signal to the at least one other communications device, the discovery signal including an indication that the communications device is attempting to initiate a ranging-based service with the at least one other communications device; receiving, by the transceiver circuitry in the communications device, a response signal from the at least one other communications device, determining, by control circuitry in the communications device, an estimate of an angle-of-arrival of the response signal to the communications device and an estimate of a distance between the communications device and the at least one other communications device from the response signal; using, by the control circuitry in the communications device, the estimate of the angle-of-arrival of the response signal to the communications device and the estimate of the distance between the communications device and the at least one other communications device to initiate the ranging-based service between the communications device and the at least one other communications device.

<FIG> shows an example of a communications device initiating a ranging-based service between itself and another communications device. As shown in <FIG>, a master UE <NUM> is performing communications with a nearby UE <NUM>. In accordance with example embodiments, a master UE <NUM> is a communications device which is configured to initiate a ranging-based service. For example, the master UE <NUM> may be a communications device which controls and manages ranging-based services for a specific location for example, a house, a coffee shop, a warehouse, a factory, a traffic light for a pedestrian crossing or the like.

The master UE <NUM> is configured to determine a distance and AoA of signals received by the master UE from one or more other nearby UEs. The master UE <NUM> may ensure that pre-defined criteria for the ranging-based service are met during set-up of the ranging-based service and are maintained subsequently. For example an application at an application layer can trigger a requirement for the ranging-based, which is received by other layers through an application layer interface, which then causes the ranging based service to be initiated.

In accordance with example embodiments, a nearby UE <NUM> is a communications device in proximity to the master UE <NUM> that is configured to support a ranging-based service initiated by a master UE <NUM>. However, the nearby UE <NUM>, is not configured to initiate a ranging-based service.

In step <NUM> of <FIG>, the master UE <NUM> determines to initiate a ranging-based service. In one example, a user of an application the master UE <NUM> may make a selection which causes the master UE <NUM> to determine to initiate the ranging based service. In response to determining to initiate the range-based service, the master UE <NUM> broadcasts a discovery signal <NUM>. The discovery signal <NUM> may be broadcasted periodically by the master UE <NUM>. The discovery signal <NUM> may include an indication that the master <NUM> is attempting to initiate a ranging-based service. For example, the discovery signal <NUM> may include a solicitation to one or more other communications devices to provide information which can be used by the master <NUM> to determine a distance and direction of the each of the respective one or more other communications device from the master UE <NUM>. In the example of <FIG>, the nearby UE <NUM> is an example of "one or more other communications devices".

In example embodiments, the discovery signal <NUM> is transmitted in a sidelink synchronisation signals (S-SS) and/or a physical sidelink broadcast channel (PSBCH) used in sidelink communications between the master UE <NUM> and the nearby UE <NUM>. In other words, the discovery signal <NUM> may be transmitted in an S-SS and/ or PSBCH block comprising <NUM> OFDM symbols for normal cyclic prefix and <NUM> symbols for extended cyclic prefix as will be appreciated by one skilled in the art. In such embodiments, the indication that the master UE <NUM> is attempting to initiate a ranging-based service included in the discovery signal <NUM> may be indicated by a bit in the PSBCH. For example, a bit may be included in the PSBCH where a bit value of "<NUM>" indicates that the master UE <NUM> is attempting to initiate ranging-based service and a bit value of "<NUM>" indicates that the ranging-based service has not been initiated or is not available. As will be explained below, the nearby UE <NUM> may be able to identify a time slot used to transmit the discovery signal <NUM> and other slots within a radio frame based on the detection of the S-SS or PSBCH block containing the discovery signal <NUM>.

In step <NUM>, the nearby UE <NUM> processes <NUM> the received discovery signal <NUM>. If the nearby UE <NUM> is configured to support a ranging based service (for example, the nearby UE <NUM> may be configured to support the ranging-based service by higher layers such as an application layer) then the nearby UE <NUM> will attempt to detect the discovery signal <NUM>. If the discovery signal is successfully detected by the nearby UE <NUM> then the nearby UE <NUM> proceeds to establish time and frequency synchronisation with the master UE <NUM> and checks for an indication that the master UE <NUM> is attempting to initiate ranging-based services. In the example where a bit in the PSBCH is used to indicate that the master UE <NUM> is attempting to initiate a ranging based service, the nearby UE <NUM> reads the PSBCH to check if the bit value is <NUM> or <NUM>.

Based on the indication of whether or not the master UE <NUM> is attempting to initiate a ranging-based service, the nearby UE <NUM> may transmit a response signal <NUM> to the master UE <NUM>. In such embodiments, the nearby UE <NUM> transmits the response signal <NUM> to the master UE <NUM> such that the master UE <NUM> can determine an estimate of a distance of the nearby UE <NUM> from the master UE <NUM> and an estimate of an AoA of the response signal <NUM> transmitted from the nearby UE <NUM> to the master UE <NUM>.

In example embodiments, the response signal <NUM> contains control information and one or more demodulating reference signals (DMRS). In example embodiments a Physical Sidelink Control Channel (PSCCH) may be used to transmit the response signal <NUM>. In such embodiments, the master UE <NUM> may estimate the distance of the nearby UE <NUM> from the master UE <NUM> and estimate an AoA of the response signal <NUM> transmitted from the nearby UE <NUM> to the master UE <NUM> based on the DMRS included in the response signal <NUM> transmitted by the PSCCH. In example embodiments, the master UE <NUM> may determine an identification of the nearby UE <NUM> from the PSCCH carrying the response signal <NUM>.

<FIG> illustrate an example of how the nearby UE <NUM> may transmit the response signal <NUM> in a way which enables the master UE <NUM> to determine an estimate of a distance of the nearby UE <NUM> from the master UE <NUM> from the response signal <NUM>. <FIG> illustrate time and frequency domain physical resources represented as two time slots <NUM>, <NUM> each comprising physical resources provided by a number of Orthogonal Frequency Division Multiplexing (OFDM) symbols. It will be appreciated by one skilled in the art that the time slot may have a number of OFDM symbols determined by a 3GPP standard such as for example a <NUM>/NR wireless access interface. In <FIG>, the two time slots <NUM>, <NUM> are shown, which illustrate the master UE <NUM> transmitting the discovery signal <NUM> to the nearby UE <NUM>. In <FIG> the two time slots <NUM>, <NUM> are shown to illustrate the nearby UE <NUM> receiving the discovery signal <NUM>. In <FIG> the two time slots <NUM>, <NUM> are shown to illustrate the nearby UE <NUM> transmitting the response signal <NUM> to the master UE <NUM>. In <FIG>, the two time slots <NUM>, <NUM> are shown to illustrate the master UE <NUM> receiving the response signal <NUM> from the nearby UE <NUM>.

<FIG> illustrates a process in which, the master UE <NUM> transmits in a time slot n the discovery signal <NUM> to the nearby UE <NUM>. In <FIG> the time slot n is an example of a first <NUM> of the two time slots <NUM>, <NUM>. Symbol tMtx is used to represent a time during the time slot n at which transmission of the discovery signal <NUM> begins at the master UE <NUM>. As will be appreciated by one skilled in the art, the transmission of the discovery signal <NUM> may last one or more OFDM symbols in time slot n as illustrated in the first time slot <NUM>. In some embodiments, the discovery signal <NUM> includes an indication of a slot timing for the master UE <NUM>. The nearby UE <NUM> determines the time slot in which the discovery signal <NUM> is transmitted. For example, the nearby UE <NUM> may determine that the discovery signal <NUM> was transmitted in slot n, from which the nearby UE <NUM> can derive a slot timing. For example, as discussed above, the nearby UE <NUM> may be able to identify a time slot used to transmit the discovery signal <NUM> and other slots within a radio frame based on the detection of the S-SS or PSBCH block containing the discovery signal <NUM>. Symbol tNrx is used to represent a time at which the nearby UE <NUM> begins receiving the discovery signal <NUM>. It will be appreciated that a difference between the time at which the transmission of the discovery signal <NUM> begins and the time at which the nearby UE <NUM> begins receiving the discovery signal is a first propagation delay t1 between the master UE <NUM> and the nearby UE <NUM>.

In example embodiments, the response signal <NUM> is transmitted to the master UE <NUM> in a way which enables the master UE <NUM> to determine an estimate of a distance between the nearby UE <NUM> and the master UE <NUM> from the response signal <NUM>. For example, the nearby UE <NUM> may be configured to transmit the response signal <NUM> to the master UE <NUM> at a slot boundary of a second <NUM> of the time slots <NUM>, <NUM> in which the nearby UE <NUM> determines to transmit the response signal <NUM>. In one example, the nearby UE <NUM>, in response to determining that the discovery signal <NUM> was transmitted in time slot n <NUM>, transmits the response signal <NUM> at a slot boundary <NUM> of a first subsequent time slot n+<NUM> to the time slot n in which the discovery signal was received as shown in <FIG>. In <FIG>, the first subsequent time slot n+<NUM> is an example of the second time slot <NUM>. However this could be any number of slots m after the slot n <NUM> in which the discovery signal was transmitted. In one example the slot boundary could mean the first OFDM symbol or symbols after the slot boundary. It will be appreciated therefore that, in other examples, the nearby UE <NUM> may determine to transmit the response signal <NUM> at a slot boundary of a time slot later than time slot n+<NUM>.

Symbol tNtx represents a time at which the transmission of the response signal <NUM> from the nearby UE <NUM> to the master UE <NUM> begins as measured at the master UE (all timings are with respect to those at the master UE <NUM>). The nearby UE <NUM> may begin transmitting the response signal <NUM> on a first OFDM symbol after the slot boundary <NUM>. It will be appreciated by one skilled in the art that the transmission of the response signal <NUM> may last one or more OFDM symbols. Symbol tMrx represents a time as measured at the master UE at which the response signal arrives at the master UE <NUM>. As will be appreciated from <FIG>, a difference between the time at which the master UE <NUM> begins transmitting the discovery signal tMtx and a time at which the response signal is received at the master UE <NUM> tMrx is represented by symbol tT. As will be appreciated from <FIG>, a difference between the time at which the nearby UE <NUM> begins receiving the discovery signal tNrx and the time at which the master UE <NUM> begins transmitting the discovery signal tMtx is represented by a first propagation delay t<NUM>. The first propagation delay t<NUM> represents an indication of a time taken for the discovery signal to propagate from the master UE <NUM> to the nearby UE <NUM>. As will be appreciated from <FIG>, a difference between the time at which the master UE <NUM> begins receiving the response signal tMrx and the time at which the nearby UE <NUM> begins transmitting the discovery signal tNtx is represented by a second propagation delay t<NUM>. The second propagation delay t<NUM> represents an indication of a time taken for the response signal to propagate from the nearby UE <NUM> to the master UE <NUM>. The first and second propagation delays t<NUM>,t<NUM> may be equal or nearly equal. A sum of the first and second propagation delays t<NUM>,t<NUM> may be referred to as a "two-way propagation delay".

The master UE <NUM> may compare the time at which the response signal <NUM> arrives at the master UE <NUM> tMrx with the time at which the transmission of the discovery signal <NUM> from the master UE <NUM> begins tMtx to determine tT. In such embodiments, the master UE <NUM> may detect the response signal <NUM> and, in response to detecting the response signal, compare the time of arrival of the response signal <NUM> tMrx with the time at which the transmission of the discovery signal <NUM> from the master UE <NUM> begins tMtx. Since the master UE <NUM> may be aware of its own slot duration, the master UE may use tT to determine the two-way propagation delay. The master UE <NUM> may then calculate a one-way propagation delay by halving the two-way propagation delay. The master UE <NUM> may then use the propagation delay to determine an estimate of the distance between the master UE <NUM> and the nearby UE <NUM>.

It will be appreciated by one skilled in the art that the above embodiment assumes that the nearby UE <NUM> and the master UE <NUM> do not perform timing advance (TA). It will be appreciated by one skilled in the art that the propagation delay may be determined in a case in which the master UE <NUM> and the nearby UE <NUM> perform TA. Typically this involves transmission of a RACH preamble in a PRACH slot and a receiving UE measuring a propagation delay between the preamble and the PRACH slot boundary.

Returning to <FIG>, in step <NUM>, the master UE <NUM> determines an estimate of a distance of the nearby UE <NUM> from the master UE <NUM> and an estimate of an AoA of the response signal <NUM> transmitted from the nearby UE <NUM> to the master UE <NUM>. Such estimates of the distance and direction can be utilised during the ranging-based service.

Example embodiments explained above can therefore provide a communications device initiating a ranging-based service which can obtain information which the communications device can use to determine the distance and direction of the communications device from one or more other communications devices.

However, there may exist scenarios in which the communications device moves after the ranging-based service has been initiated. Example embodiments can provide a method for updating distance and direction measurements at the communications device. Such embodiments can enable an application layer providing the ranging-based service in the communications devices to decide whether or not to discontinue the ranging-based service or take pre-defined actions while continuing to provide the ranging-based service.

For example, after the ranging-based service has been initiated, the master UE <NUM> may transmit one or more signals to the nearby UE <NUM> including a request for the nearby UE <NUM> to transmit corresponding response signals such that the master UE <NUM> can determine an updated estimate of the distance between the master UE <NUM> and the nearby UE <NUM> and an estimate of an AoA for the corresponding response signals from the nearby UE <NUM>. The periodic signals may be transmitted as discovery signals as described herein (for example in S-SS or PSBCH) or physical channels used for carrying data and control information (for example Physical Sidelink Control Channel (PSCCH) and/or Physical Sidelink Shared Channel (PSSCCH)).

In example embodiments, the updated estimates of the distance between the master UE <NUM> and the nearby UE and the estimate of the AoA for the corresponding response signals from the nearby UE <NUM> may be periodically reported to the application layer. In other examples, the updated estimates of the distance between the master UE <NUM> and the nearby UE and the estimate of the AoA for the corresponding response signals from the nearby UE <NUM> may be reported to a Radio Resource Control (RRC) layer or a sidelink Radio Resource Control (SL-RRC) layer.

In example embodiments, the updated estimates of the distance between the master UE <NUM> and the nearby UE and the estimate of the AoA for the corresponding response signals from the nearby UE <NUM> are only reported to the application layer if a change in one or more of the updated estimates of the distance between the master UE <NUM> and the nearby UE and estimates of the AoA for the response signals from the nearby UE <NUM> are above pre-defined thresholds.

In such scenarios where the updated estimates of the distance between the master UE <NUM> and the nearby UE and the estimate of the AoA for the corresponding response signals nearby UE <NUM> are reported to the application layer, the updated estimates of the distance between the master UE <NUM> and the nearby UE and the estimate of the AoA for the corresponding response signals nearby UE <NUM> may be weighted by Layer <NUM> (L1) or Layer <NUM> (L3) algorithms before reporting to the application layer.

In such scenarios where a communications device moves after the ranging-based service has been initiated, example embodiments provide a method for declaring radio link failure (RLF), thereby discontinuing the ranging-based service.

In conventional techniques, a communications device monitors a radio link quality based on a signal strength of reference signals or channels. If the radio link quality is below a predefined threshold, the communications device reports RLF to higher layers (such as an application layer for example).

In example embodiments RLF may be declared by the master UE <NUM> based on one or more of measurements of radio signal strength of the response signals from the nearby UE <NUM>, a distance between the master UE <NUM> and the nearby UE <NUM> and an AoA of the response signals received at the master UE <NUM>. Conditions for declaring RLF may depend on a type of application providing the ranging-based service.

For example if a ranging-based service has stringent requirements on AoA, then if an AoA exceeds a pre-determined threshold or an accuracy of the AoA is below a pre-determined threshold, then the master UE <NUM> may declare RLF. Similarly, if the distance between the nearby UE <NUM> and the master UE <NUM> exceeds a pre-determined threshold then the master UE <NUM> may declare RLF.

In example embodiments, both the master UE <NUM> and the nearby UE <NUM> determine estimations of distance and AoA. An example of both the master UE <NUM> and the nearby UE <NUM> determining measurements of distance and AoA is shown in <FIG> is based on <FIG> but has additional steps <NUM> and <NUM>.

After the determination of the estimation of the distance of the nearby UE <NUM> from the master UE <NUM> and the estimation of the AoA of the response signal <NUM> transmitted from the nearby UE <NUM> to the master UE <NUM>, the master <NUM> transmits a counter response signal <NUM> to the nearby UE <NUM>. The counter response signal <NUM> transmitted by the master UE <NUM> may be similar to the response signal transmitted by the nearby UE <NUM>. The counter response signal <NUM> may include an identification of the master UE <NUM> which can be used by the nearby UE <NUM> to determine an identity of the master UE <NUM>. In example embodiments, the master UE <NUM> may include the determined estimation of the distance of the nearby UE <NUM> from the master UE <NUM> and/or the estimation of the AoA of the response signal <NUM> transmitted from the nearby UE <NUM> to the master UE <NUM> in the counter response signal <NUM> transmitted to the nearby UE <NUM>. The counter response signal <NUM> may comprise physical channels carrying control information and data (for example, PSCCH and/or PSSCH). In some embodiments, the counter response signal <NUM> may be transmitted to the nearby UE <NUM> such that the nearby UE <NUM> can determine an estimate of the distance between the nearby UE <NUM> and the master UE <NUM> and an estimate of an AoA of the counter response signal <NUM> at the nearby UE <NUM>. In one example, the counter response signal <NUM> is transmitted to the nearby UE <NUM> in the same way in which the response signal <NUM> was transmitted to the master UE <NUM> as shown in <FIG>.

In step <NUM>, the nearby UE <NUM> determines an estimate of the distance between the nearby UE <NUM> and the master UE <NUM> and an estimate of an AoA of the counter response signal <NUM> at the nearby UE <NUM>.

An accuracy of an estimation of an AoA is dependent on the radio propagation environment. For example, if there are multiple paths or an obstacle between a receiver of the master UE <NUM> and a transmitter of the nearby UE <NUM>, then the master UE <NUM> may detect reflections of the response signal <NUM>.

In example embodiments, an accuracy of an estimation of an AoA can be improved by including an indication of a beam direction used to transmit the discovery signal <NUM> to the nearby UE <NUM> in the discovery signal <NUM>.

For example, <FIG> illustrates an example of the master UE <NUM> transmitting the discovery signal <NUM> by beam sweeping in a radio propagation environment in which there are no obstacles between the transmitter of the master UE <NUM> and the receiver of the nearby UE <NUM>. Such a radio propagation environment may be referred to as a "direct wave" radio propagation environment.

As will be appreciated by one skilled in the art "beam sweeping" is a technique used to transmit a signal in a plurality of pre-defined directions in a pre-defined time interval. In other words, the signal is transmitted in a plurality of different directions in a plurality of equal or near-equal time intervals. An example is shown in <FIG>, where the master UE <NUM> transmits eight discovery signals 508a-d in a plurality of directions, namely, East, North-East, North, North-West, West, South-West, South and South-East respectively. As shown in <FIG>, the each discovery signal 508a-g is transmitted in a pre-defined time interval. The time intervals may correspond to OFDM time slots for example. It will be appreciated that <FIG> illustrate an example of beam sweeping and more or fewer discovery signals may be transmitted in more or fewer directions over more or fewer time slots respectively.

In <FIG>, the nearby UE <NUM> receives the discovery signal 508a which was transmitted eastward from the master UE <NUM>. As explained above, the discovery signal 508a which was transmitted eastward from the master UE <NUM> may include an indication that it was transmitted from the master UE <NUM> in the eastward direction. In some embodiments, the indication that the discovery signal 508a was transmitted in an eastward direction from the master UE <NUM> may be included in sidelink control information (SCI).

For the example in <FIG>, where an indication is included for each of eight directions, three bits may be allocated in first stage SCI in PSCCH. It will be appreciated by one skilled in the art that eight directions can be indicated by three bits because three bits can be arranged in eight different combinations. As will be appreciated by one skilled in the art, a larger number of bits may be used to indicate a larger number of directions or a smaller number of bits may be used to indicate a smaller number of directions. For example, for a higher accuracy application with <NUM> beam directions, four bits may be used to indicate each of the <NUM> directions. In example embodiments, a number of bits used to indicate beam directions will be indicated to the master UE <NUM> by signalling from a network or the number of bits will be fixed in specifications. Additionally, there are reserved bits in SCI format <NUM>-A, which may be used in accordance with example embodiments for scheduling of PSSCH and a second stage SCI on PSSCH. Alternatively, a new SCI format may be defined for the ranging-based service.

The number of bits for beam direction could be changeable. For example, if the application requires high accuracy, the number of bits should be expanded bysignalling or pre-defined in system specifications. In terms of beam sweeping, NR base station (SSB index) assumes a FR1 <<NUM> max <NUM> beams, FR1 <NUM>-<NUM> max <NUM> beams and FR2 mmWave max <NUM> beams. Currently, the sidelink in FR1 does not support beamforming. The sidelink for FR2 may use beamforming, but, the number of beams has not been specified yet. Therefore between <NUM> and <NUM> beams are likely.

The nearby UE <NUM> may use the indication to determine whether or not the discovery signal 508a was transmitted directly to the nearby UE <NUM>. For example, the nearby UE <NUM> may use an electronic compass to determine a direction of approach of the discovery signal 508a. Alternatively, the nearby UE <NUM> may estimate an AoA of the discovery signal 508a to determine the direction of approach. Since the discovery signal 508a was transmitted by the master UE <NUM> from the east, the nearby UE <NUM> can determine that the discovery signal was directly transmitted to the nearby UE <NUM> if it approaches the nearby UE <NUM> from the west. In some examples, the nearby UE <NUM> determines that the discovery signal 508a was directly transmitted to the nearby UE <NUM> if the determined angle of approach is within a pre-defined angle of west.

<FIG> illustrates an example of the nearby UE <NUM> receiving the discovery signal 508b indirectly from the master UE <NUM>. For simplicity, it may be assumed that the master UE <NUM> in <FIG> transmits discovery signals 508a-g using the bean sweeping described in <FIG>. As will be appreciated from <FIG>, a horizontal <NUM> and vertical wall <NUM> act as obstacles to signals transmitted by the master UE <NUM>. It is assumed in this example that the walls <NUM>, <NUM> reflect incident signals. In this example, the discovery signal 508b transmitted in the north-east direction from the master UE <NUM> is reflected off the horizontal wall <NUM> and received at the nearby UE <NUM>. As explained above, the discovery signal 508b which was transmitted from the master UE <NUM> in the north-eastern direction may contain an indication that it was transmitted from the master UE <NUM> in the north-eastern direction. As explained above, the nearby UE <NUM> may determine a direction of approach of the discovery signal 508b. In this example, the nearby UE <NUM> may determine that the discovery signal 508b is a direct signal if the determined direction of approach is west. However, as shown in <FIG>, the direction of approach of the discovery signal 508b to the nearby UE <NUM> is south-east. The nearby UE <NUM> may therefore determine that the discovery signal 508b was sent indirectly to the nearby UE <NUM>. Such a radio propagation environment may be referred to as an "indirect wave" propagation environment.

In example embodiments, the nearby UE <NUM> may determine not to use a ranging-based service which the master UE <NUM> is attempting to initiate if the nearby UE <NUM> determines that a discovery signal sent to the nearby UE <NUM> was not directly sent to the nearby UE <NUM>. In other words, the nearby UE <NUM> may determine not to send a response signal to the master UE <NUM> or the nearby UE <NUM> may send a response signal to the master UE <NUM> including an indication that the nearby UE <NUM> does not intend to participate in the ranging-based service which the master UE <NUM> is attempting to initiate.

Such embodiments can ensure that the nearby UE <NUM> only participates in the ranging-based service if the radio propagation environment is reliable. In other words, such embodiments can increase an accuracy of any AoAs calculated by the master UE <NUM> or the nearby UE <NUM> by only allowing the nearby UE <NUM> to participate in the ranging-based service when the discovery signal <NUM> received by the nearby UE <NUM> is a direct signal rather than, for example, a reflected signal.

<FIG> illustrates a flow diagram for a method of operating a communications device to provide a ranging-based service which uses a proximity between the communications device and at least one other communications device. The method starts in Step S1. In step S2, the communications device uses transceiver circuitry to transmit a discovery signal to the at least one other communications device, the discovery signal including an indication that the communications device is attempting to initiate a ranging-based service with the at least one other communications device.

In step S3, the communications device uses the transceiver circuitry to receive a response signal from the at least one other communications device.

In step S4, the communications device uses control circuitry to estimate an estimate of an angle-of-arrival of the response signal to the communications device and an estimate of a distance between the communications device and the at least one other communications device from the response signal.

In step S5, the communications device uses the control circuitry to use the estimate of the angle-of-arrival of the response signal to the communications device and the estimate of the distance between the communications device and the at least one other communications device to initiate the ranging-based service between the communications device and the at least one other communications device. The method ends in step S6.

It may be noted various example approaches discussed herein may rely on information which is predetermined / predefined in the sense of being known by both the base station and the communications device. It will be appreciated such predetermined / predefined information may in general be established, for example, by definition in an operating standard for the wireless telecommunication system, or in previously exchanged signalling between the base station and communications devices, for example in system information signalling, or in association with radio resource control setup signalling, or in information stored in a SIM application. That is to say, the specific manner in which the relevant predefined information is established and shared between the various elements of the wireless telecommunications system is not of primary significance to the principles of operation described herein. It may further be noted various example approaches discussed herein rely on information which is exchanged / communicated between various elements of the wireless telecommunications system and it will be appreciated such communications may in general be made in accordance with conventional techniques, for example in terms of specific signalling protocols and the type of communication channel used, unless the context demands otherwise. That is to say, the specific manner in which the relevant information is exchanged between the various elements of the wireless telecommunications system is not of primary significance to the principles of operation described herein.

It will be appreciated that the principles described herein are not applicable only to certain types of communications device, but can be applied more generally in respect of any types of communications device, for example the approaches can be applied in respect of any type of wireless communications device capable of transmitting to another wireless communications device.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims.

Claim 1:
A method of operating a communications device to provide a ranging-based service which uses a proximity between the communications device and at least one other communications device, the method comprising
transmitting (<NUM>), by transceiver circuitry in the communications device, a discovery signal to the at least one other communications device, the discovery signal including an indication that the communications device is attempting to initiate a ranging-based service with the at least one other communications device;
receiving (<NUM>), by the transceiver circuitry in the communications device, a response signal from the at least one other communications device;
determining (<NUM>), by control circuitry in the communications device, an estimate of an angle-of-arrival of the response signal to the communications device and an estimate of a distance between the communications device and the at least one other communications device from the response signal;
using, by the control circuitry in the communications device, the estimate of the angle-of-arrival of the response signal to the communications device and the estimate of the distance between the communications device and the at least one other communications device to initiate the ranging-based service between the communications device and the at least one other communications device,
characterized in that the transmitting, by the transceiver circuitry in the communications device, the discovery signal to the at least one other communications device, comprises
transmitting the discovery signal in a Physical Sidelink Broadcast Channel, PSBCH and the indication that the communications device is attempting to initiate the ranging-based service with the at least one other communications device is indicated by one or more bits in the PSBCH,
transmitting, by the transceiver circuitry in the communications device, a plurality of copies of the discovery signal in a plurality of directions in a plurality of pre-defined time intervals, and
including, by the control circuitry in the communications device, an indication of a direction of transmission of the respective copy of the discovery signal in each of the plurality of copies of the discovery signal.