Patent Description:
Document <CIT> discloses a method applied to a remote UE including receiving PCS discontinuous reception configuration information; performing PCS discontinuous reception configuration and performing PCS discontinuous reception.

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

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

One aspect of both LTE and NR is direct device-to-device (D2D) communications between two communications devices, where some of the signals are not transmitted to or from a base station. Such D2D communications are also referred to as sidelink communications, and signals are transmitted directly between communications devices over a sidelink interface
The increasing use of different types of network infrastructure equipment and terminal devices associated with different traffic profiles give rise to new challenges for efficiently handling communications in wireless communications systems that need to be addressed.

Embodiments of the present technique, which further relate to a receiving communication device, a method of operating communications devices and circuitry for communications devices, as defined by the appended independent claims, allow for the reduction of battery power consumption for sidelink/D2D communications.

It will be appreciated that operational aspects of the telecommunications (or simply, communications) networks discussed herein which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to the relevant standards and known proposed modifications and additions to the relevant standards.

The network <NUM> includes a plurality of base stations <NUM> connected to a core network <NUM>. Each base station provides a coverage area <NUM> (i.e. a cell) within which data can be communicated to and from terminal devices <NUM>. Data is transmitted from base stations <NUM> to terminal devices <NUM> within their respective coverage areas <NUM> via a radio downlink (DL). Data is transmitted from terminal devices <NUM> to the base stations <NUM> via a radio uplink (UL). The core network <NUM> routes data to and from the terminal devices <NUM> via the respective base stations <NUM> and provides functions such as authentication, mobility management, charging and so on. Terminal devices may also be referred to as mobile stations, user equipment (UE), user terminal, mobile radio, communications device, and so forth. Base stations, which are an example of network infrastructure equipment / network access node, may also be referred to as transceiver stations / nodeBs / e-nodeBs / eNBs / g-nodeBs / gNBs and so forth. In this regard different terminology is often associated with different generations of wireless telecommunications systems for elements providing broadly comparable functionality. However, certain embodiments of the disclosure may be equally implemented in different generations of wireless telecommunications systems, and for simplicity certain terminology may be used regardless of the underlying network architecture. That is to say, the use of a specific term in relation to certain example implementations is not intended to indicate these implementations are limited to a certain generation of network that may be most associated with that particular terminology.

As mentioned above, the embodiments of the present disclosure can also find application with advanced wireless communications systems such as those referred to as <NUM> or New Radio (NR) Access Technology. The use cases that are considered for NR include:.

eMBB services are characterised by high capacity with a requirement to support up to <NUM> Gb/s. The requirement for URLLC is a reliability of <NUM> - <NUM>-<NUM> (<NUM> %) for one transmission of a relatively short packet such as <NUM> bytes with a user plane latency of <NUM>.

The elements of the wireless access network shown in <FIG> may be equally applied to a <NUM> new RAT configuration, except that a change in terminology may be applied as mentioned above.

An example configuration of a wireless communications network which uses some of the terminology proposed for and used in NR and <NUM> is shown in <FIG>. In <FIG> a plurality of transmission and reception points (TRPs) <NUM> are connected to distributed control units (DUs) <NUM>, <NUM> by a connection interface represented as a line <NUM>. Each of the TRPs <NUM> 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 <NUM>, forms a cell of the wireless communications network as represented by a circle <NUM>. As such, wireless communications devices <NUM> which are within a radio communications range provided by the cells <NUM> can transmit and receive signals to and from the TRPs <NUM> via the wireless access interface. Each of the distributed units <NUM>, <NUM> are connected to a central unit (CU) <NUM> (which may be referred to as a controlling node) via an interface <NUM>. The central unit <NUM> is then connected to the core network <NUM> which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network <NUM> may be connected to other networks <NUM>.

The TRPs <NUM> of <FIG> may in part have a corresponding functionality to a base station or eNodeB of an LTE network. Similarly, the communications devices <NUM> may have a functionality corresponding to the UE devices <NUM> known for operation with an LTE network. It will be appreciated therefore that operational aspects of a new RAT network (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be different to those known from LTE or other known mobile telecommunications standards. However, it will also be appreciated that each of the core network component, base stations and communications devices of a new RAT network will be functionally similar to, respectively, the core network component, base stations and communications devices of an LTE wireless communications network.

In terms of broad top-level functionality, the core network <NUM> connected to the new RAT telecommunications system represented in <FIG> may be broadly considered to correspond with the core network <NUM> represented in <FIG>, and the respective central units <NUM> and their associated distributed units / TRPs <NUM> may be broadly considered to provide functionality corresponding to the base stations <NUM> of <FIG>. The term network infrastructure equipment / access node may be used to encompass these elements and more conventional base station type elements of wireless telecommunications systems. Depending on the application at hand the responsibility for scheduling transmissions which are scheduled on the radio interface between the respective distributed units and the communications devices may lie with the controlling node / central unit and / or the distributed units / TRPs. A communications device <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 central unit <NUM> in the first communication cell <NUM> via one of the distributed units <NUM> associated with the first communication cell <NUM>.

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

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

A more detailed diagram of some of the components of the network shown in <FIG> is provided by <FIG>. In <FIG>, a TRP <NUM> as shown in <FIG> comprises, as a simplified representation, a wireless transmitter <NUM>, a wireless receiver <NUM> and a controller or controlling processor <NUM> which may operate to control the transmitter <NUM> and the wireless receiver <NUM> to transmit and receive radio signals to one or more UEs <NUM> within a cell <NUM> formed by the TRP <NUM>. As shown in <FIG>, an example UE <NUM> is shown to include a corresponding transmitter <NUM>, a receiver <NUM> and a controller <NUM> which is configured to control the transmitter <NUM> and the receiver <NUM> to transmit signals representing uplink data to the wireless communications network via the wireless access interface formed by the TRP <NUM> and to receive downlink data as signals transmitted by the transmitter <NUM> and received by the receiver <NUM> in accordance with the conventional operation.

The transmitters <NUM>, <NUM> and the receivers <NUM>, <NUM> (as well as other transmitters, receivers and transceivers described in relation to examples and embodiments of the present disclosure) may include radio frequency filters and amplifiers as well as signal processing components and devices in order to transmit and receive radio signals in accordance for example with the <NUM>/NR standard. The controllers <NUM>, <NUM>, <NUM> (as well as other controllers described in relation to examples and embodiments of the present disclosure) may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc., configured to carry out instructions which are stored on a computer readable medium, such as a non-volatile memory. The processing steps described herein may be carried out by, for example, a microprocessor in conjunction with a random access memory, operating according to instructions stored on a computer readable medium. The transmitters, the receivers and the controllers are schematically shown in <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 / TRP / base station as well as the UE / communications device will in general comprise various other elements associated with its operating functionality.

As shown in <FIG>, the TRP <NUM> also includes a network interface <NUM> which connects to the DU <NUM> via a physical interface <NUM>. The network interface <NUM> therefore provides a communication link for data and signalling traffic from the TRP <NUM> via the DU <NUM> and the CU <NUM> to the core network <NUM>.

The interface <NUM> between the DU <NUM> and the CU <NUM> is known as the F1 interface which can be a physical or a logical interface. The F1 interface <NUM> between CU and DU may operate in accordance with specifications 3GPP TS <NUM> and 3GPP TS <NUM>, and may be formed from a fibre optic or other wired high bandwidth connection. In one example the connection <NUM> from the TRP <NUM> to the DU <NUM> is via fibre optic. The connection between a TRP <NUM> and the core network <NUM> can be generally referred to as a backhaul, which comprises the interface <NUM> from the network interface <NUM> of the TRP <NUM> to the DU <NUM> and the F1 interface <NUM> from the DU <NUM> to the CU <NUM>.

In a typical currently deployed network, idle mode terminal devices are configured to monitor for paging messages periodically. For terminal devices (in connected and idle mode) operating in a discontinuous reception (DRX) mode this occurs when they wake up for their DRX wake time. Paging signals for a specific terminal device are transmitted in defined frames (Paging Frames) / sub-frames (Paging Occasions) which for a given terminal device may be derived from the International Mobile Subscriber Identifier (IMSI) of the terminal device, as well as paging related DRX parameters established in system information transmitted within the network. In connected mode, the terminal device is configured to periodically monitor PDCCH in groups of slots or subframes. If a PDCCH is not detected during the group of slots or subframes, the terminal device may sleep for the next cycle of the periodicity. Power saving is an important aspect of a user's experience of NR, which will influence the adoption of <NUM> handsets and/or services. DRX is one method of power saving for NR terminal devices.

The basic DRX cycle is shown in <FIG>, which consists of a DRX ON period of duration TDRX-ON and a period of inactivity, i.e. a DRX OFF period of duration TDRX-OFF where the DRX ON period occurs periodically at a DRX period, PDRX. During the DRX ON period, the UE switches on its receiver to monitor for downlink traffic and switches off its receiver during the DRX OFF period to save power consumption. The DRX parameters TDRX-ON & PDRX are configured by the network. It should be appreciated by those skilled in the art that such a basic operation may not always be efficient, particularly if a UE frequently does not receive any signals during the ON period (or active operating mode) of the DRX operation.

If a PDCCH is detected for the UE during the DRX ON period, the UE starts an inactivity timer TInactivity specifying a period in which the UE will remain awake (i.e. receiver is active) and continues to monitor for further downlink and/or uplink traffic, notably PDCCH. When the inactivity timer expires, the UE moves to the DRX OFF state. An example is shown in <FIG>, where a PDCCH is detected at time t<NUM> of a DRX ON period, which triggers the inactivity timer which starts at time t<NUM> for a duration of TInactivity. When the timer expires at time t<NUM>, the UE switches off its receiver. The inactivity period can extend beyond the DRX ON period; that is, the UE continues to stay awake after the DRX ON period as shown in <FIG> where the DRX ON ends at time t<NUM> and the inactivity period continues until time t<NUM>. The rationale here is that if the UE receives a data packet, then it is likely it may receive another data packet in the near future and so if the UE receives a data packet towards the end of its DRX ON period, the inactivity timer will keep the UE awake to receive potential further data packets. If the UE receives a packet during the inactivity period, the inactivity timer will reset, i.e. the UE would extend its wake up duration due to the possibility of receiving yet further data packets.

If during the inactivity period, the UE receives a further PDCCH, the inactivity timer is reset, i.e. restarted. It should be noted that the inactivity timer is only restarted here following a single successful decoding of the further PDCCH for a first transmission only; i.e. not when that further PDCCH is a retransmission. An example is shown in <FIG>, where during a DRX ON period (between time t<NUM> and t<NUM>), a PDCCH is detected by the UE at time t<NUM> and so the inactivity timer starts after the PDCCH at time t<NUM> which expires at time t<NUM>. During this first inactivity period, another PDCCH is detected at time t<NUM> which then resets the inactivity timer, i.e. the inactivity timer restarts after this PDCCH at time t<NUM> with a duration of Tinactivity. This follows the same rationale above; that if a data packet is transmitted for a UE then it is likely that another data packet would be transmitted for the same UE in the near future.

The inactivity timer is configured via RRC signalling by the network and can range from <NUM> to <NUM>. In [<NUM>], some DRX parameters and Tinactivity values are proposed for evaluation, which represent likely network configurations. Example values in [<NUM>] include <NUM> TDRX-ON with <NUM> Tinactivity, <NUM> TDRX-ON with <NUM> Tinactivity. It is observed that the inactivity period is typically significantly longer than the DRX ON duration, which would also consume significant battery power.

DRX may be further characterised (as is described in [<NUM>]) by an active time, which defines the total duration during which the UE monitors PDCCH, including the on duration DRX ON of the DRX cycle, the time during which the UE is performing continuous reception while the inactivity timer has not expired, and the time during which the UE is performing continuous reception while waiting for a retransmission opportunity. DRX may also be characterised by a retransmission timer, which signifies a duration until a retransmission can be expected. It would be appreciated by those skilled in the art that inactivity timers, on-duration timers, retransmission timers and the link are enumerated in units of subframes in LTE and in units of <NUM>, or sub-millisecond (i.e. <NUM>/<NUM>) in NR.

Both NR and LTE support a short DRX mode of operation. The short DRX cycle may be optionally implemented within a long DRX (i.e. standard) cycle and follows the period where the inactivity timer is running. It is controlled by the following parameters:.

Operation of short DRX is described in the 3GPP Technical Specification <NUM> [<NUM>], in section <NUM>. Some of the text herein describing the short DRX operation is reproduced and adapted from [<NUM>]. The principle of operation of "short DRX" is that PDCCH is monitored according to a DRX cycle once the inactivity period has expired. This is illustrated in <FIG> which shows the following aspects of short DRX operation:.

If the UE decodes a PDCCH during one of the DRX_ON durations of the short DRX phase, the UE restarts its inactivity timer (and can then enter a second period of short DRX if there was no PDCCH activity during this second running of the inactivity timer). This operation is shown in <FIG>. The duration of the inactivity timer and the parameters controlling short-DRX operation are configurable. At the extremes, the network can configure:.

Device-to-Device (D2D) communications is an aspect of mobile communications which has been established for devices to communicate directly with each other rather than via a wireless communications network. That is to say that radio signals representing data are transmitted via a wireless interface by one device and received by another to communicate that data, rather than the signals being transmitted to radio infrastructure equipment of a wireless communication network, which are then detected and decoded by the infrastructure equipment to recover that data and communicated on to a destination device.

D2D communications can take different forms, which are illustrated in <FIG>. As shown in <FIG>, in one example two communications devices (UEs) <NUM>, <NUM> are operating within a coverage area of a cell <NUM> provided by radio infrastructure equipment <NUM>, which has a cell boundary <NUM> represented by a dashed line. The radio infrastructure equipment <NUM> may for example be a TRP <NUM> such as that shown in <FIG>. As represented by dashed lines <NUM>, <NUM>, the UEs <NUM>, <NUM>, may transmit and receive signals to the infrastructure equipment <NUM> to transmit or to receive data on an uplink or a downlink respectively of a wireless access interface formed by a wireless communications network of which the infrastructure equipment <NUM> forms part. However within the radio coverage area of the cell <NUM> the UEs <NUM>, <NUM> may communicate directly between one another via a D2D wireless access interface as represented by a dashed line <NUM>. The UEs <NUM>, <NUM> can be configured to transmit and to receive signals via a D2D wireless access interface which may be separate and not shared or overlap a frequency band of the wireless access interface provided by the infrastructure equipment <NUM>. Alternatively the UEs <NUM>, <NUM> may transmit and receive signals via a part of the wireless access interface provided by the infrastructure equipment <NUM>. A D2D wireless access interface formed for one UE to transmit radio signals to another UE is referred to as a sidelink or PC5.

Another example of D2D communications is also shown in <FIG> where UEs fall outside a coverage area of a wireless communication network and so communicate directly with one another. As represented by dashed lines <NUM>, <NUM>, <NUM>, three UEs <NUM>, <NUM>, <NUM> are operable to transmit and receive signals representing data via sidelinks. These sidelinks <NUM>, <NUM>, <NUM> may be formed by a D2D wireless access interface which falls within a frequency band of the infrastructure equipment <NUM> or may be outside this frequency band. However the UEs <NUM>, <NUM>, <NUM> organise access to a D2D wireless access interface autonomously without reference to a wireless access interface. In some cases, the UEs <NUM>, <NUM>, <NUM> may be pre-configured with some parameters for a D2D wireless access interface. As another example, one of the UEs <NUM> within the coverage area of the cell <NUM> acts as a relay node for one or more of the UEs <NUM>, <NUM>, <NUM> which are outside the coverage area as represented by a sidelink <NUM>.

Here D2D communications of the form of sidelink <NUM> are referred to as in-coverage communications, D2D communications of the form of sidelink <NUM> are referred to as partial coverage communications, and D2D communications of the form of sidelinks <NUM>, <NUM>, <NUM> are referred to as out-of-coverage communications.

According to 3GPP standards such as LTE, whilst downlink and uplink communications are specified for transmissions from an infrastructure equipment such as a gNB to a UE and from a UE to a gNB respectively, sidelink communications are specified to realise UE-to-UE (device-to-device (D2D)) communication, especially for sidelink discovery, sidelink communication and vehicle to everything (V2X) sidelink communication between UEs. The LTE sidelink has the following characteristics as described below, which are reproduced from [<NUM>]:.

Currently, for <NUM> or New Radio (NR) standardisation, a sidelink has been specified in Release-<NUM> for V2X communication, with the LTE sidelink being a starting point for the NR sidelink. For NR sidelink, the following sidelink physical channels are defined:.

Furthermore, the following sidelink physical signals are defined:.

NR sidelink can be enhanced with a power saving mechanism for sidelink which would be a useful feature especially for D2D (device-to-device) communications between devices having limited battery power.

A UE is provided by RRC signalling a bandwidth part (BWP) for SL transmissions (SL BWP) and a resource pool. This is typically done by the base station if the UE is in coverage or reachable by a relay node, but for some corner cases where it is known a UE will be or is likely to be out of coverage or reach by a base station, the SL BWP and resource pool may be hardcoded (preconfigured) onto the UE's SIM, for example. The resource pool is configured within the SL BWP. For the resource pool, the UE is provided a number of sub-channels where each sub-channel includes a number of contiguous physical resource blocks (PRBs). The sub-channel is defined as the minimum granularity in the frequency domain for transmission and reception of sidelink in the unit of PRB. The first PRB of the first sub-channel in the SL BWP is indicated. Hence the UE only needs to monitor those sub-channels that have been indicated, reducing the search space and number of blind decodes necessary at the UE. A slot is the time-domain granularity for a resource pool. Available slots for a resource pool are provided by RRC signalling and occur with a periodicity. For each periodicity, the RRC signalling may be bitmap signalling or indication of starting slot and length. A UE may be configured with an Rx (reception) resource pool and a Tx (transmission) resource pool separately. The Rx resource pool may be used for PSCCH monitoring at a Rx UE. Here, those skilled in the art would appreciate that a BWP (which is well known in the art as a power saving scheme for a UE) is a part of a carrier bandwidth providing a number of contiguous physical resource blocks (PRBs) which can be grouped to form a BWP in NR. Multiple BWPs can exist within a carrier bandwidth, but only one BWP is activated per UE at a given time.

<FIG> shows an example of resource pool configuration in a sidelink BWP <NUM>. Each instance of the resource pool <NUM> (labelled A to G) consists of four sub-channels <NUM> and ten slots <NUM> starting from the second slot of the resource pool periodicity, where the resource pool periodicity <NUM> is sixteen slots; i.e. the start of each instance of the resource pool <NUM> is sixteen slots from the start of the previous resource pool instance. Sidelink BWP portion <NUM> is a zoomed in portion of overall sidelink BWP <NUM>, showing more clearly how two resource pool instances <NUM> (A and B) are made up from four sub-channels <NUM> and ten slots <NUM>, with the periodicity <NUM> of sixteen slots being clearly seen. It should be noted that each instance of the resource pool within the periodicity may consist of non-contiguous slots in the time domain.

NR sidelink supports broadcast, groupcast and unicast (i.e. three "cast types" are supported). For SL broadcast, a UE transmits data to unspecified UEs which are close to the transmitter UE. The SL broadcast may be suitable for alert indication. For SL unicast, a UE transmits data to a specified UE. To realise the unicast transmission, SCI (sidelink control information) includes a destination ID (i.e. identifier of a receiver UE) and a source ID (i.e. identifier of a transmitter UE). For SL groupcast, a UE transmits data to one or more specified UEs within the same group. SL groupcast may be suitable for a platooning application which is a method for driving a group of vehicles together. To realise the groupcast transmission, SCI includes a destination group ID (i.e. identifier of a group to be received) and a source ID.

The UE needs to be able to save power in V2X. This is particularly relevant to pedestrian UEs, as these are typically connected to far smaller batteries than UEs which are implemented in vehicles. In sidelink communications, the UE monitors for activity at a resource-pool granularity and not at a subframe-level granularity (herein, for NR, the term "subframe-level granularity" can mean either "at the granularity of every <NUM>" or "at the granularity of every <NUM>/<NUM>"). The Release-<NUM> DRX-based power-saving mechanisms are thus not applicable for sidelink due to the mismatch between the resource-pool granularity and the subframe-level granularity. For example, with reference to <FIG>, there are some subframes in the NR frame structure that are not part of the resource pools; resource pools A to G do not occupy the entirety of the sidelink BWP <NUM>. It would be inappropriate for the UE to monitor PSCCH in subframes that are not contained within resource pools. Embodiments of the present technique seek to overcome these issues, enabling enhanced power saving by a UE in V2X.

<FIG> shows a schematic representation of a wireless communications system comprising a plurality of communications devices <NUM>, <NUM> in accordance with embodiments of the present technique. The communications devices <NUM>, <NUM> each comprise a controller (or controller circuitry) <NUM>, <NUM>, which may be, for example, a microprocessor(s), a CPU(s), a chip(s), or a dedicated chipset(s), etc..

The communications device <NUM> (which is a receiving communications device) comprises a receiver (or receiver circuitry) <NUM> configured to receive signals from one or more other communications devices within sidelink communications resources of a plurality of resource pool instances of a sidelink interface <NUM>, each of the resource pool instances being arranged in time (e.g. each of the resource pool instances could be temporally discrete i.e. each resource pool instance is separate in time from the others of the resource pool instances, or could share common borders with no gaps in between, or could at least partially overlap each other) in accordance with a resource pool periodicity (i.e. the frequency of occurrence of each of the resource pool instances, defining when they start with respect to the start of the previous resource pool instance). It should be appreciated by those skilled in the art that this receiver <NUM> may be a standalone receiver, or may form part of a transceiver (or transceiver circuitry, which is not shown in <FIG>) capable of transmitting and receiving signals. The communications device <NUM> may also comprise a separate transmitter (not shown in <FIG>). Similarly, the other communications device <NUM> (which may be one of a plurality of other communications devices <NUM> to the communications device <NUM>) may comprise a transceiver (or transceiver circuitry) <NUM>, which is configured to transmit or receive signals to or from the communications device <NUM> or other communications devices <NUM> via the sidelink interface <NUM>. This transceiver <NUM> may also be formed of separate transmitter and receiver elements/circuitry (not shown in <FIG>).

In embodiments of the present technique, the receiver circuitry <NUM> and the controller circuitry <NUM> of the communications device <NUM> are configured in combination to switch <NUM> at a first periodic rate between a primary active operating mode and a primary reduced power operating mode in accordance with a primary discontinuous reception, DRX, operation (i.e. long DRX), to monitor <NUM> for signals <NUM> transmitted by the other communications devices <NUM> to the communications device <NUM> in one or more of the resource pool instances during the primary active operating mode (of course, it would be appreciated that such signals <NUM> are not always transmitted by the other communications device(s) <NUM> or received by the communications device <NUM> in each instance of the primary active operating mode), and to stop monitoring <NUM> for signals transmitted by the other communications devices to the receiving communications device in one or more of the resource pool instances during the primary reduced power operating mode. The first periodic rate is dependent on the resource pool periodicity. Here, it should be noted that the "first periodic rate" refers to the DRX period of the long DRX cycle (i.e. the primary DRX operation), and is analogous to PDRX of <FIG>, for example. For example, in some arrangements of embodiments of the present technique, the first periodic rate may be an integer multiple of the resource pool periodicity.

Essentially, embodiments of the present technique propose that DRX operation be applied at the resource pool level for sidelink communications. Embodiments of the present technique therefore allow for the following features of DRX operation to be supported:.

The following description of arrangements of embodiments of the present technique provides detail on how such features of DRX operation may be supported for sidelink communications.

Functionality of a basic embodiment of the invention is shown in <FIG> shows a UE operating according to sidelink DRX functionality, where there is no data sent to the UE. In <FIG>, there are seven instances of a resource pool that the UE is configured to monitor (the instances are labelled 'A' to 'G'). The following functionality applies, during each of the instances of the resource pool A to G:.

A skilled artisan will appreciate that while the UE may be required to switch between the primary active operating mode and the primary reduced power operating mode at the start of a resource pool instance, it may also switch to a reduced power operating mode for other reasons. For example, in periods between resource pool instances when these resource pool instances are temporally discrete, the UE may also switch to a reduced power operating mode, since there is no resource for the UE to monitor. In other words, here, the UE may switch to the primary reduced power operating mode at the end of the final resource pool instance in which it was in the primary active operating mode, rather than at the start of the first resource pool instance in which it is in the primary reduced power operating mode. It will be further appreciated that the requirement to switch between the primary active operating mode and the primary reduced power operating mode may be a soft requirement, which in effect allows the UE to operate in the primary reduced power operating mode, rather than mandating certain UE power consumption functionality or design targets. For example, the UE may determine that it is allowed to switch to the primary reduced power operating mode, but decides to make a measurement, and so remains in the primary active operating mode in order to make the measurement.

<FIG> shows the long DRX cycle <NUM> functionality when the UE receives a PSCCH <NUM> in a resource pool during the DRX_ON <NUM> duration. In this case, an inactivity timer <NUM> is started and the UE monitors for further PSCCHs in resource pool instances during the running of the inactivity timer <NUM> (i.e. during an inactivity period), during which the UE does not enter DRX_OFF. In other words, the receiving communications device is configured to start, during a current instance of the primary active operating mode upon receiving a first signal from one of the other communications devices, an inactivity timer specifying an inactivity period comprising one or more resource pool instances (following the resource pool instance in which the PSCCH is received) during which the receiving communications device does not switch into the primary reduced power operating mode. Functionality in the different instances of the resource pools in the example of <FIG> is described below:.

<FIG> shows long DRX <NUM> and short DRX <NUM> functionality applied to the sidelink at the resource pool level; i.e. short DRX <NUM> functionality is applied to the example of <FIG>. Due to PSCCH <NUM> activity during the DRX_ON <NUM> phase of the long DRX cycle <NUM>, the inactivity timer <NUM> runs for the duration of resource pool instances B and C. Once the inactivity timer <NUM> expires, due to there being no PSCCH during the running of the inactivity timer, the UE enters a short DRX phase <NUM>, whereby the UE monitors some instances of the resource pool and does not monitor other instances. After the short DRX phase <NUM>, the UE goes to sleep until the DRX_ON <NUM> phase at the start of the next long DRX cycle <NUM>. The functionality in the various instances of the resource pool are described below:.

As described above, operation of the UE during the short DRX phase <NUM> could be in accordance with one or more of a plurality of different implementations. The secondary DRX operation may comprise a plurality of phases, each of the phases having a different value of at least one DRX parameter. This parameter may comprise a proportion of the secondary DRX operation during which the receiving communications device is in the secondary active operating mode, or may comprise a number of resource pool instances during which the receiving communications device is in each instance of the second active operating mode during the secondary DRX operation. In at least some implementations, there may be a gap of one or more resource pool instances between two of the plurality of phases of the secondary DRX operation during which the receiving communications device is in the secondary reduced power operating mode. In at least some implementations, the proportion of the secondary DRX operation during which the receiving communications device is in the secondary active operating mode is highest in a first of the plurality of phases and decreases over time such that the proportion of the secondary DRX operation during which the receiving communications device is in the secondary active operating mode is lowest in a last of the plurality of phases.

Embodiments of the present technique also provide a transmitting UE that knows the DRX operation of the receiving UE, for example because the transmitting UE indicates to the receiving UE how it should behave in terms of its DRX operation, or the transmitting UE receives signalling information from the receiver UE or otherwise detects signalling information transmitted from or to the receiver UE which indicates the receiver UE's DRX operation. The transmitter UE is then able to transmit signals to the receiver UE in accordance with its DRX operation; i.e. when the receiver UE is awake and actively monitoring for signals. In other words, such embodiments of the present technique can provide a transmitting communications device comprising a transmitter configured to transmit signals to one or more other communications devices within sidelink communications resources of a plurality of resource pool instances of a sidelink interface, each of the resource pool instances being arranged in time in accordance with a resource pool periodicity, and a controller configured in combination with the transmitter to determine that a receiving communications device of the other communications devices is operating in accordance with a primary discontinuous reception, DRX, operation in which the receiving communications device switches at a first periodic rate between a primary active operating mode in which the receiving communications device will monitor for the signals transmitted by the transmitting communications device in one or more of the resource pool instances and a primary reduced power operating mode in which the receiving communications device will stop monitoring for signals transmitted by the transmitting communications device in one or more of the resource pool instances, and to transmit signals to the receiving communications device in accordance with the primary DRX operation, wherein the first periodic rate is dependent on the resource pool periodicity.

In at least some arrangements of embodiments of the present technique, one or more of the first periodic rate and primary DRX operation (i.e. the long DRX cycle), the second periodic rate and secondary DRX operation (i.e. the short DRX phase), the inactivity timer and inactivity period, and the specified value (the offset value for comparing to the resource pool ID MOD long DRX cycle duration calculation as described above) may be signalled to the receiving communications device by at least one of the other communications devices (i.e. a transmitting communications device/signalling communications device). Furthermore, in at least some of these arrangements, the signalling communications device may actually decide itself what these DRX parameters should be for the receiving communications device, whilst in other arrangements, the signalling communications device may simply relay the DRX parameters to the receiving communications device having been itself signalled such DRX parameters by the network or by another of the communications devices.

It should be appreciated by those skilled in the art that, where signalling or signals have been referred to herein as being received from a mobile communications network, such signalling/signals may be from the core network or radio access network, and may be transmitted to the UE by a gNB/base station or by a relay node between the UE and the gNB/base station.

<FIG> shows a flow diagram illustrating a method of operating a communications device according to embodiments of the present technique. The communications device (which is a receiving communications device) is configured to receive signals from one or more other communications devices within sidelink communications resources of a plurality of resource pool instances of a sidelink interface, each of the resource pool instances being arranged in time in accordance with a resource pool periodicity.

The method begins in step S151. The method comprises, in step S152, switching at a first periodic rate between a primary active operating mode and a primary reduced power operating mode in accordance with a primary discontinuous reception, DRX, operation. In step S153, the method comprises monitoring for signals transmitted by the other communications devices to the receiving communications device in one or more of the resource pool instances during the primary active operating mode. In step S154, the process comprises stopping the monitoring for signals transmitted by the other communications devices to the receiving communications device in one or more of the resource pool instances during the primary reduced power operating mode. Here, the first periodic rate is dependent on the resource pool periodicity. The process ends in step S155.

Those skilled in the art would appreciate that the method shown by <FIG> may be adapted in accordance with embodiments of the present technique. For example, other intermediate steps may be included in the method, or the steps may be performed in any logical order. Though embodiments of the present technique have been described largely by way of the example communications system shown in <FIG>, and in accordance with the arrangements shown in <FIG>, it would be clear to those skilled in the art that they could be equally applied to other systems to those described herein.

Those skilled in the art would further appreciate that such infrastructure equipment and/or communications devices as herein defined may be further defined in accordance with the various arrangements and embodiments discussed in the preceding paragraphs. It would be further appreciated by those skilled in the art that such infrastructure equipment and communications devices as herein defined and described may form part of communications systems other than those defined by the present disclosure.

Claim 1:
A receiving communications device comprising
a receiver configured to receive signals from one or more other communications devices within sidelink communications resources of a plurality of resource pool instances of a sidelink interface, each of the resource pool instances being arranged in time in accordance with a resource pool periodicity, and
a controller configured in combination with the receiver
to switch at a first periodic rate between a primary active operating mode and a primary reduced power operating mode in accordance with a primary discontinuous reception, DRX, operation (S152),
to monitor for signals transmitted by the other communications devices to the receiving communications device in one or more of the resource pool instances during the primary active operating mode (S153), and
to stop monitoring for signals transmitted by the other communications devices to the receiving communications device in one or more of the resource pool instances during the primary reduced power operating mode (S154),
wherein the first periodic rate is dependent on the resource pool periodicity;
wherein each of the resource pool instances is associated with an index value, and wherein the receiving communications device is configured to switch between the primary reduced power operating mode and the primary active operating mode at the start of a resource pool instance when a result of a function of the index value of the resource pool instance and a period defined by the first periodic rate is equal to a specified value.