Methods, communications devices, and infrastructure equipment

Abstract

A method of operating a communications device comprising a low-power receiver and a main receiver is provided. The method comprises receiving a low-power wake-up signal, LP-WUS, from a wireless communications network via the low-power receiver while the low-power receiver is in an ON state and the main receiver is in an OFF state, and transmitting to the main receiver, based on receiving the LP- WUS, a wake-up command indicating that the main receiver is to switch from the OFF state to an ON state. Here, a power consumption of the low-power receiver when the low-power receiver is in the ON state is lower than a power consumption of the main receiver when the main receiver is in the ON state. Here, the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

Description

[0001] METHODS, COMMUNICATIONS DEVICES, AND INFRASTRUCTURE EQUIPMENT

[0002] BACKGROUND

[0003] Field of Disclosure

[0004] The present disclosure relates to communications devices, infrastructure equipment and methods for the more effective power saving of communications devices in wireless communications networks.

[0005] The present application claims the Paris Convention priority from European patent application number EP24154844.5, fded on 30 January 2024, the contents of which are hereby incorporated by reference.

[0006] Description of Related Art

[0007] The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of fding, are neither expressly or impliedly admitted as prior art against the present invention.

[0008] Previous generation mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) architecture, are able to support a wider range of services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. For example, with the improved radio interface and enhanced data rates provided by LTE systems, a user is able to enjoy high data rate applications such as mobile video streaming and mobile video conferencing that would previously only have been available via a fixed line data connection. The demand to deploy such networks is therefore strong and the coverage area of these networks, i.e. geographic locations where access to the networks is possible, is expected to continue to increase rapidly.

[0009] Current and future wireless communications networks are expected to routinely and efficiently support communications with an ever-increasing range of devices associated with a wider range of data traffic profiles and types than existing 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, extended Reality (XR) and so on. Some of these different types of devices may be deployed in very large numbers, for example low complexity devices for supporting the “The Internet of Things”, and may typically be associated with the transmissions of relatively small amounts of data with relatively high latency tolerance. Other types of device, for example supporting high-definition video streaming, may be associated with transmissions of relatively large amounts of data with relatively low latency tolerance. Other types of device, for example used for autonomous vehicle communications and for other critical applications, may be characterised by data that should be transmitted through the network with low latency and high reliability. A single device type might also be associated with different traffic profiles / characteristics depending on the application(s) it is running. For example, different consideration may apply for efficiently supporting data exchange with a smartphone when it is running a video streaming application (high downlink data) as compared to when it is running an Internet browsing application (sporadic uplink and downlink data) or being used for voice communications by an emergency responder in an emergency scenario (data subject to stringent reliability and latency requirements).

[0010] In view of this there is expected to be a desire for current wireless communications networks, for example those which may be referred to as 5G or new radio (NR) systems / new radio access technology (RAT) systems, or indeed future 6G wireless communications, as well as future iterations / releases of existing systems, to efficiently support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles and requirements.

[0011] One example of a new service is referred to as Ultra Reliable Low Latency Communications (URLLC) services which, as its name suggests, requires that a data unit or packet be communicated with a high reliability and with a low communications delay. Another example of a new service is enhanced Mobile Broadband (eMBB) services, which are characterised by a high capacity with a requirement to support up to 20 Gb / s. URLLC and eMBB type services therefore represent challenging examples for both LTE type communications systems and 5G / NR communications systems.

[0012] 5G NR has continuously evolved and the current work plan includes 5G-NR-advanced in which some further enhancements are expected, especially to support new use-cases / scenarios with higher requirements. The desire to support these new use-cases and scenarios gives rise to new challenges for efficiently handling communications in wireless communications systems that need to be addressed.

[0013] SUMMARY OF THE DISCLOSURE

[0014] The present disclosure can help address or mitigate at least some of the issues discussed above.

[0015] Embodiments of the present technique can provide a method of operating a communications device comprising a low-power receiver and a main receiver. The method comprises receiving a low-power wake-up signal, LP-WUS, from a wireless communications network via the low-power receiver while the low-power receiver is in an ON state and the main receiver is in an OFF state, and transmitting to the main receiver, based on receiving the LP-WUS, a wake-up command indicating that the main receiver is to switch from the OFF state to an ON state. Here, a power consumption of the low-power receiver when the low-power receiver is in the ON state is lower than a power consumption of the main receiver when the main receiver is in the ON state. Here, the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

[0016] Embodiments of the present technique, which, in addition to methods of operating communications devices, relate to methods of operating infrastructure equipment, communications devices and infrastructure equipment, circuitry for communications devices and infrastructure equipment, computer programs, and computer-readable storage mediums, can allow for the more effective power saving of communications devices operating in a wireless communications network.

[0017] Respective aspects and features of the present disclosure are defined in the appended claims.

[0018] It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the present technology. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein like reference numerals designate identical or corresponding parts throughout the several views, and wherein: Figure 1 schematically represents some aspects of an LTE-type wireless telecommunication system which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0021] Figure 2 schematically represents some aspects of a new radio access technology (NR) wireless telecommunications system which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0022] Figure 3 is a schematic block diagram of an example infrastructure equipment and communications device which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0023] Figure 4 is a graphical plot of user equipment (UE) processing activity against time illustrating an example of a discontinuous reception (DRX) cycle;

[0024] Figure 5 is a graphical plot of UE processing activity against time illustrating an example of a paging occasion preceded by a wake-up signal (WUS) according to that used for LTE;

[0025] Figure 6 is a graphical plot of UE processing activity against time illustrating an example of a DRX cycle according to that used for 5G / NR;

[0026] Figure 7 illustrates the relationship between a main receiver (MR) and a lower power receiver (LP-WUR) of a UE which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0027] Figure 8 shows an example of how a low-power wake-up signal (LP-WUS) may be monitored for by an LP-WUR of a UE prior to a paging occasion;

[0028] Figure 9 shows a part schematic, part message flow diagram representation of a wireless communications system comprising a communications device and an infrastructure equipment in accordance with embodiments of the present technique;

[0029] Figure 10 illustrates an example orthogonal frequency division multiplexing (OFDM)-on-off keying (OOK) LP-WUS waveform and a corresponding OFDM symbol envelope in accordance with embodiments of the present technique;

[0030] Figure 11 shows a block diagram of an example OOK LP-WUS receiver in accordance with embodiments of the present technique;

[0031] Figure 12 illustrates an example of a Manchester coded OOK (MC-OOK) LP-WUS waveform and a corresponding OFDM symbol envelope in accordance with embodiments of the present technique;

[0032] Figure 13 shows an exemplary block diagram for a system at the wireless communications network that generates an MC-OOK OFDM symbol template in accordance with embodiments of the present technique;

[0033] Figure 14 illustrates a WUS design based on both time-multiplexed OFDM symbols and MC-OOK symbols in accordance with embodiments of the present technique;

[0034] Figure 15 illustrates how OFDM-based WUS symbols may be superposed on MC-OOK-based WUS symbols in accordance with embodiments of the present technique;

[0035] Figure 16 shows an exemplary block diagram for a system at the wireless communications network that generates superposed WUS symbols where OFDM-based WUS symbols are superposed on MC-OOK- based WUS symbols in accordance with embodiments of the present technique; and

[0036] Figure 17 shows a flow diagram illustrating a process of communications in a communications system in accordance with embodiments of the present technique.

[0037] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Long Term Evolution Advanced Radio Access Technology (4G)

[0039] Figure 1 provides a schematic diagram illustrating some basic functionality of a mobile telecommunications network / system 6 operating generally in accordance with LTE principles, but which may also support other radio access technologies, and which may be adapted to implement embodiments of the disclosure as described herein. Various elements of Figure 1 and certain aspects of their respective modes of operation are well-known and defined in the relevant standards administered by the 3GPP (RTM) body, and also described in many books on the subject, for example, Holma H. and Toskala A [1] . It will be appreciated that operational aspects of the telecommunications 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.

[0040] The network 6 includes a plurality of base stations 1 connected to a core network 2. Each base station provides a coverage area 3 (i.e. a cell) within which data can be communicated to and from communications devices 4. Although each base station 1 is shown in Figure 1 as a single entity, the skilled person will appreciate that some of the functions of the base station may be carried out by disparate, inter-connected elements, such as antennas (or antennae), remote radio heads, amplifiers, etc. Collectively, one or more base stations may form a radio access network.

[0041] Data is transmitted from base stations 1 to communications devices 4 within their respective coverage areas 3 via a radio downlink (DL). Data is transmitted from communications devices 4 to the base stations 1 via a radio uplink (UL). The core network 2 routes data to and from the communications devices 4 via the respective base stations 1 and provides functions such as authentication, mobility management, charging and so on. Communications devices may also be referred to as mobile stations, user equipment (UEs), user terminals, mobile radios, mobile terminals, terminal devices, wireless transmit and receive units (WTRUs), and so forth. Services provided by the core network 2 may include connectivity to the internet or to external telephony services. The core network 2 may further track the location of the communications devices 4 so that it can efficiently contact (i.e. page) the communications devices 4 for transmitting downlink data towards the communications devices 4.

[0042] Base stations, which are an example of network infrastructure equipment, may also be referred to as transceiver stations, nodeBs, e-nodeBs, eNB, g-nodeBs, gNB and so forth. In this regard different terminology is often associated with different generations of wireless telecommunications systems for elements providing broadly comparable functionality. However, 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.

[0043] New Radio Access Technology (5G)

[0044] Systems incorporating NR technology are expected to support different services (or types of services), which may be characterised by different requirements for latency, data rate and / or reliability. For example, Enhanced Mobile Broadband (eMBB) services are characterised by high capacity with a requirement to support up to 20 Gb / s. The requirements for Ultra Reliable and Low Latency Communications (URLLC) services are for one transmission of a 32 byte packet to be transmitted from the radio protocol layer 2 / 3 SDU ingress point to the radio protocol layer 2 / 3 SDU egress point of the radio interface within 1 ms with a reliability of 1 - 10'5(99.999 %) or higher (99.9999%) [2],

[0045] Massive Machine Type Communications (mMTC) is another example of a service which may be supported by NR-based communications networks. In addition, systems may be expected to support further enhancements related to Industrial Internet of Things (IIoT) in order to support services with new requirements of high availability, high reliability, low latency, and in some cases, high-accuracy positioning. An example configuration of a wireless communications network which uses some of the terminology proposed for and used in NR and 5G is shown in Figure 2. In Figure 2 a plurality of transmission and reception points (TRPs) 10 are connected to distributed control units (DUs) 41, 42 by a connection interface represented as a line 16. Each of the TRPs 10 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 10, forms a cell of the wireless communications network as represented by a circle 12. As such, wireless communications devices 14 which are within a radio communications range provided by the cells 12 can transmit and receive signals to and from the TRPs 10 via the wireless access interface. Each of the distributed units 41, 42 are connected to a central unit (CU) 40 (which may be referred to as a controlling node) via an interface 46. The central unit 40 is then connected to the core network 20 which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network 20 may be connected to other networks 25.

[0046] The elements of the wireless access network shown in Figure 2 may operate in a similar way to corresponding elements of an LTE network as described with regard to the example of Figure 1. It will be appreciated that operational aspects of the telecommunications network represented in Figure 2, and of other networks discussed herein in accordance with embodiments of the disclosure, 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 currently used approaches for implementing such operational aspects of wireless telecommunications systems, e.g. in accordance with the relevant standards.

[0047] The TRPs 10 of Figure 2 may in part have a corresponding functionality to a base station or eNodeB of an LTE network. Similarly, the communications devices 14 may have a functionality corresponding to the UE devices 4 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.

[0048] In terms of broad top-level functionality, the core network 20 connected to the new RAT telecommunications system represented in Figure 2 may be broadly considered to correspond with the core network 2 represented in Figure 1, and the respective central units 40 and their associated distributed units / TRPs 10 may be broadly considered to provide functionality corresponding to the base stations 1 of Figure 1. The term network infrastructure equipment / access node may be used to encompass these elements and more conventional base station type elements of wireless telecommunications systems. Depending on the application at hand the responsibility for scheduling transmissions which are scheduled on the radio interface between the respective distributed units and the communications devices may lie with the controlling node / central unit and / or the distributed units / TRPs. A communications device 14 is represented in Figure 2 within the coverage area of the first communication cell 12. This communications device 14 may thus exchange signalling with the first central unit 40 in the first communication cell 12 via one of the distributed units / TRPs 10 associated with the first communication cell 12. It will further be appreciated that Figure 2 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.

[0049] 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 Figures 1 and 2. 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 1 as shown in Figure 1 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 40 and / or a TRP 10 of the kind shown in Figure 2 which is adapted to provide functionality in accordance with the principles described herein.

[0050] A more detailed diagram of some of the components of the network shown in Figure 2 is provided by Figure 3. In Figure 3, a TRP 10 as shown in Figure 2 comprises, as a simplified representation, a wireless transmitter 30, a wireless receiver 32 and a controller or controlling processor 34 which may operate to control the transmitter 30 and the wireless receiver 32 to transmit and receive radio signals to one or more UEs 14 within a cell 12 formed by the TRP 10. As shown in Figure 3, an example UE 14 is shown to include a corresponding transmitter 49, a receiver 48 and a controller 44 which is configured to control the transmitter 49 and the receiver 48 to transmit signals representing uplink data to the wireless communications network via the wireless access interface formed by the TRP 10 and to receive downlink data as signals transmitted by the transmitter 30 and received by the receiver 48 in accordance with the conventional operation.

[0051] The transmitters 30, 49 and the receivers 32, 48 (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 5G / NR standard. The controllers 34, 44 (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 Figure 3 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 Figure 3, the TRP 10 also includes a network interface 50 which connects to the DU 42 via a physical interface 16. The network interface 50 therefore provides a communication link for data and signalling traffic from the TRP 10 via the DU 42 and the CU 40 to the core network 20.

[0052] The interface 46 between the DU 42 and the CU 40 is known as the F 1 interface which can be a physical or a logical interface. The Fl interface 46 between CU and DU may operate in accordance with specifications 3GPP TS 38.470 and 3GPP TS 38.473, and may be formed from a fibre optic or other wired or wireless high bandwidth connection. In one example the connection 16 from the TRP 10 to the DU 42 is via fibre optic. The connection between a TRP 10 and the core network 20 can be generally referred to as a backhaul, which comprises the interface 16 from the network interface 50 of the TRP 10 to the DU 42 and the Fl interface 46 from the DU 42 to the CU 40.

[0053] In order for a UE such as UE 4 or 14 to transmit uplink data to the network (e.g. on a Physical Uplink Control Channel (PUCCH) or a Physical Uplink Shared Channel (PUSCH)) to, for example, base station 1 or TRP 10, the UE must first ensure it is synchronised with the network on the uplink. Since a particular eNB or gNB expects to be receiving communications from many UEs, it needs to ensure that it shares a common timing understanding with each of these UEs (i.e. they are synchronised in terms of the starting times of frames and Orthogonal Frequency Division Multiplexing (OFDM) symbols). This is so that the eNB is able to schedule communication with each of them in a manner that avoids collisions and to ensure orthogonality of the uplink signals, such that inter-subcarrier interference is avoided or mitigated.

[0054] Power Saving and Discontinuous Reception (DRX) in NR

[0055] In atypical currently deployed network, communications devices can operate in a discontinuous reception (DRX) mode during which the communications devices wake-up (i.e. power-up their receivers) to receive signals during their DRX wake time. DRX operation can occur when the communications devices are in an idle mode or in a connected mode. In connected mode, the communications device is configured to periodically monitor physical downlink control channels (PDCCHs) in groups of slots or subframes. If a PDCCH with a Radio Network Temporary Identifier (RNTI) addressed to the communications device is not detected during the group of slots or subframes, the communications device may sleep for the next cycle of the periodicity. Power saving is an important aspect of a user’s experience of such wireless radio access technologies such as NR, which will influence the adoption of 5G and future generation handsets and / or services. DRX is one method of power saving for NR communications devices.

[0056] In legacy systems such as LTE and NR, a UE in RRC-CONNECTED mode will send a scheduling request when it has UL data to transmit. Following this, the gNB will schedule / allocate some UL transmission resources and inform the UE via DCI on PDCCH where the resources are both in time and frequency and the configuration for the UE’s UL transmission such as MCS, TBS etc. When the UE has no data to transmit in the UL, it waits in RRC-CONNECTED mode. If on the other hand data arrives at the gNB for the UE, the gNB will also schedule DL resources and inform the UE via DCI on PDCCH on the location in frequency and time of the resources and the configuration the UE is to use for DL reception on the allocated resources. Once the UE receives the DL data, it waits in RRC-CONNECTED mode for the next DL data whilst monitoring the PDCCH in every DL subframe for any scheduling information targeted at the UE. The UE battery power consumption whilst in RRC-CONNECTED mode could be quite high because of the continuous PDCCH monitoring by the UE and reception of other DL channels and signals. However, if the network knows that neither DL data for nor UL data from the UE is imminent, it is desirable that the UE goes to sleep while remaining in RRC-CONNECTED mode. In legacy LTE and NR, this entails UE undertaking RRC-CONNECTED mode DRX (C-DRX). The basic DRX cycle is shown in Figure 4, 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 the PDCCH for downlink traffic and switches off its receiver during the DRX OFF period to save power consumption. The DRX parameters TDRX-ON & PDRX SXQ configured by the network.

[0057] The price paid for utilising DRX operation (e.g. C-DRX) is that if data meant for a UE currently in its DRX OFF period arrives at the gNB for delivery to the UE, the gNB can only schedule the data after the DRX OFF period is finished. This latency in data scheduling that arises because of C-DRX can be reduced by initiating a timer, drx-InactivityTimer. immediately after the UE detects a DCI scheduling data to it in one of the PDCCH it monitors during the drx-onDuration intervals of its C-DRX cycle. The effect of this timer is to increase the DRX ON time in anticipation that more data for the UE may arrive at the network. The rationale for this is that if data is being scheduled to the UE now, it is highly likely that more data to the same UE will follow.

[0058] When a UE has no data to transmit and the network has no data for the UE, the UE can transition into RRC-IDLE mode. In legacy systems, there is also RRC-IDLE mode DRX. RRC-IDLE mode DRX is set up to work in conjunction with other RRC-IDLE mode UE procedures such as paging of the UE, tracking area update (TAU) etc. Paging is used by the network to establish mobile terminated connections with the UE. During RRC-IDLE mode the UE can go to sleep to minimise battery power consumption. It is desirable however, for an RRC-IDLE mode UE to wake up regularly and listen for any paging messages that the network may have sent to initiate a mobile terminated connection with the UE or for other established reasons such as TAU. In NR, a UE can also wake up to listen to paging messages in RRC- INACTIVE mode.

[0059] For a UE that is awake, listening for a paging message entails monitoring the PDCCH during configured paging occasions for a DCI Format 1 0 whose cyclic redundancy check (CRC) is scrambled with P- RNTI. For an RRC-IDLE mode UE with which the network is seeking to establish a mobile terminated connection, this DCI carries resource allocation information for a subsequent PDSCH that will carry the actual paging information. If the UE detects the DCI Format 1 0 scrambled with P-RNTI, the UE stays awake to receive the scheduled PDSCH; otherwise, the UE should conclude that it is not being paged and so go back to sleep. The paging information PDSCH carries such information for many targeted UEs. Therefore, the UE needs to decode the PDSCH information to decide whether any of it is meant for the said UE. This is done by determining that some of the information is targeted towards a UE with a network preconfigured UE temporary identity (5G-S-TMSI) that matches the UE’s. The cadence with which the UE wakes up to monitor for paging messages typically follows the RRC-IDLE mode DRX configuration which defines the DRX ON and OFF times in each DRX cycle. Therefore, the network is expected to initiate paging towards a given UE during its DRX ON periods.

[0060] Often, when the UE wakes up to monitor the PDCCH for a DCI Format 1 0 with CRC scrambled with P- RNTI, it would not find it as the UE may not have been paged. Furthermore, even when the UE does find the DCI and then goes on to decode the associated PDSCH, the UE would not find a paging message targeted towards its temporary UE identity. It is only after this that a UE which found the DCI Format 1 0 with CRC scrambled with P-RNTI can conclude that there was no page for it in this paging occasion and go back to sleep. Every time the UE wakes up and does not find a PDCCH scrambled with P-RNTI, the awake UE consumes battery power. Furthermore, every time the UE wakes up, finds a PDCCH scrambled with P-RNTI but does not find a paging message targeted towards its temporary UE identity in the PDSCH, the UE consumes battery power. It should therefore be appreciated by those skilled in the art that such a basic DRX operation may not always be efficient, particularly if a UE frequently does not receive any signals (i.e. any PDCCHs with RNTIs addressed to that UE) during the ON period of the DRX operation. It is therefore desirable to wake the UE up only when there is a paging message actually targeted at the UE in the given paging occasion i.e., when the particular UE is being paged.

[0061] Wake-up Signals to Save Power

[0062] There are a number of different ways in which the battery life of a UE may be improved. One such way is by enabling a DRX configuration to adapt to a UE’s expected data reception or transmission profile. For example, a Wake-Up Signal (WUS) may be used to indicate whether a UE should wake up during a DRX ON period. The WUS is a signal or a channel that is transmitted to a UE or a group of UEs prior to a DRX ON period or Paging Occasion (PO) to indicate whether the UE(s) needs to wake up during this ON period and monitor for possible traffic, e.g. monitor the PDCCH. Using a WUS in this way to wakeup a UE recognises that not every DRX ON period contains traffic for the UE, and for such a case, the PDCCH monitoring consumes unnecessary power from the UE, which can be avoided with this WUS signaling.

[0063] Wake-up signals are supported in technologies such as eMTC, NB-IoT and in 5G NR. The eMTC / NB- loT wake-up signal (WUS) is used in RRC-IDLE mode before a paging occasion. If the UE detects a WUS, it wakes up and monitors the following paging occasion for an MTC PDCCH (MPDCCH) or an NB-IoT (NPDCCH) that may further allocate a paging message. If the UE does not receive a WUS, it can go back to sleep. The WUS consists of a known sequence. The UE can monitor for the WUS by performing a correlation against this known sequence. As indicated above, the WUS either can be common to all the UEs associated with the paging occasion, or can be associated with a group of one or more UEs that are associated with the paging occasion.

[0064] An example of a WUS is illustrated by a timing diagram showing a plot of transmission power and UE receiver activity with respect to time provided in Figure 5. As shown in Figure 5, a wake-up signal WUS 51 occurs at a known time offset (T2 - rl) 52 before a paging occasion 54. The time offset 52 allows the UE to “boot-up” its main receiver (MR) after WUS reception and before the paging occasion 54. As a result, the WUS itself can be monitored with a lower power receiver, since the lower power receiver does not need to be able to receive all the features of the signal that the MR is able to receive. The WUS is transmitted prior to the paging occasion 54 as shown in Figure 5 at time r i, only when there is an MPDCCH transmission in the paging occasion 54. The MPDCCH transmission in the paging occasion 54 allocates a PDSCH transmission between time is and T4. The PDSCH transmission comprises paging information such as the Temporary Mobile Subscriber Identity (TMSI) of a UE. The PDSCH transmission allocated by the MPDCCH may be inside or outside the paging occasion 54.

[0065] When the WUS is UE-specific (i.e. each UE has its own WUS), the WUS for that UE is only sent when there is an MPDCCH in a paging occasion which allocates a PDSCH that is targeted at that UE. When the WUS is group-specific (i.e. a group of UEs share a WUS), the WUS for that group is sent when there is an MPDCCH in a paging occasion which allocates a PDSCH that is targeted to at least one of the UEs in that group. Upon detection of a WUS, the UE will proceed to-fine tune its frequency and timing tracking loops if required and blind detects for an MPDCCH between time r 2 and r 3 followed by decoding of the PDSCH carrying the paging information between time r3and r4. If the UE fails to detect a WUS, it will go back to sleep and skip detecting for MPDDCH. Hence by using WUS, the UE will consume less energy by avoiding unnecessary monitoring of MPDCCH. It should be appreciated that WUS can also be used in connected mode when DRX is used. The paging functionality discussed above has been described with respect to LTE-M / eMTC operation, where the paging PDSCH is allocated using an MPDCCH. Those skilled in the art would appreciate that operation in 5G / NR is similar. In some examples, the WUS may be a physical channel containing very little information (e.g. UE ID or a single bit indicating that UEs monitoring that WUS should wake up) and so the UE can decode the WUS very quickly compared with blind decoding for MPDCCH. The WUS can also be encoded with a format that enables low power decoding; for example, the WUS may be a narrow bandwidth signal that can be decoded with low power using a low sampling rate receiver.

[0066] For the example of 5G NR, a wake-up signal WUS is used in CONNECTED mode DRX operation as described in [3], the contents of which are hereby incorporated by reference in their entirety. The 5G NR WUS is based on a PDCCH that carries Downlink Control Information (DCI) format 2 6. The PDCCH may be referred to as Power saving-PDCCH (PS-PDCCH), while the monitoring period for this PDCCH is referred to as a PS-PDCCH monitoring period. Here, the term PS-PDCCH is synonymous with “DCI format 2 6 with CRC scrambled by PS-RNTI”. This monitoring period may also be referred to as a “power saving monitoring period”. The procedure for monitoring DCI format 2 6 is described in detail in section 10.3 of [4], the contents of which are hereby incorporated by reference in their entirety. The NR WUS is described in more detail in [5], the contents of which are hereby incorporated by reference in their entirety.

[0067] An example timing diagram illustrating a transmission of signals with respect to time for a 5G NR operation in CONNECTED mode is shown in Figure 6. As shown in Figure 6, a PS-PDCCH 61 occurs in a search space before a DRX_ON phase 62 of a DRX cycle represented by a double headed arrow 64. This example represents one full CONNECTED mode DRX cycle. A temporal location of the PS- PDCCH 61 is in advance of the DRX ON phase 62 by an amount ps Offset 66. A UE decodes the DCI format 2 6 within the PS-PDCCH. Since the UE only has to decode the PS-PDCCH, it does not have to operate its full receiver circuitry, and therefore PS-PDCCH can be decoded with a lower receive power. If the DCI indicates that the UE should wake up, the UE wakes up its full receiver circuitry for the next DRX ON duration 62. Otherwise the UE can go to sleep following the PS-PDCCH and does not have to decode other PDCCH during the DRX ON duration 62. The UE needs to monitor for PS-PDCCH during a monitoring window, where the monitoring window starts at a known time before the start of the DRX ON period and ends at a time ps Offset before the start of the next DRX ON period.

[0068] At the time of filing of the present disclosure, 3GPP has completed a study item [6], the contents of which are hereby incorporated by reference in their entirety, on low power receivers and low power wake-up signals for NR-5G. This study item had the following objectives:

[0069] • Identify evaluation methodology (including the use cases) & key performance indicators [RANI];

[0070] • Study and evaluate low-power wake-up receiver architectures [RANI, RAN4];

[0071] • Study and evaluate wake-up signal designs to support wake-up receivers [RANI, RAN4];

[0072] • Study and evaluate LI procedures and higher layer protocol changes needed to support the wakeup signals [RAN2, RANI]; and

[0073] • Study potential UE power saving gains compared to the existing Rel-15 / 16 / 17 UE power saving mechanisms, the coverage availability, as well as latency impact of low-power WUR / WUS. System impact, such as network power consumption, coexistence with non-low-power-WUR UEs, network co verage / capacity / re source overhead should be included in the study [RANI].

[0074] The justification of the study, as described in section 3 of [6], is reproduced below. 5G systems are designed and developed targeting for both mobile telephony and vertical use cases. Besides latency, reliability, and availability, UE energy efficiency is also critical to 5G. Currently, 5G devices may have to be recharged per week or day, depending on an individual’s usage time. In general, 5G devices consume tens of milliwatts in RRC idle / inactive state and hundreds of milliwatts in RRC connected state. Designs to prolong battery life therefore are a necessity for improving energy efficiency as well as for providing a better user experience.

[0075] Energy efficiency is even more critical for UEs without a continuous energy source, e.g., UEs using small rechargeable and single coin cell batteries. Among vertical use cases, sensors and actuators are deployed extensively for monitoring, measuring, charging, etc. Generally, their batteries are not rechargeable and are expected to last for at least a few years. Such UEs may be wearable devices which may include smart watches, rings, eHealth related devices, and medical monitoring devices. With typical battery capacities, it is challenging to sustain power for up to one or two weeks as required.

[0076] The power consumption depends on the configured length of wake-up periods, e.g., on the paging cycle. To meet the battery life requirements noted above, eDRX cycles of long durations are expected to be used, resulting in high latency, which is not suitable for services with requirements of both long battery life and low latency. For example, in fire detection and extinguishment use cases, fire shutters should be closed and fire sprinklers should be turned on by the actuators within one or two seconds from the time the fire is detected by sensors; a long eDRX cycle therefore cannot meet the delay requirements. eDRX thus appears not to be suitable for latency-critical use cases. Therefore, the intention is to study ultra-low power mechanisms that can support low latency in Rel-18, e.g. lower than eDRX latency.

[0077] Currently, UEs need to periodically wake up once per DRX cycle, which dominates the power consumption in periods with no signalling or data traffic. If UEs are able to wake up only when they are triggered, e.g. via paging, power consumption could be dramatically reduced. This can be achieved by using a wake-up signal (WUS) - as described above - to trigger the main radio, and a separate receiver at the UE which has the ability to monitor for wake-up signals with ultra-low power consumption without needing to power-up the main radio (MR). The MR is relatively high power consuming, which handles the normal communication with the gNB and works for data transmission and reception, and can be turned off or set to deep sleep when it is not needed to receive data, transmit data or carry out measurements.

[0078] The power consumption for monitoring the wake-up signal depends on the wake-up signal design and the hardware module of the wake-up receiver used for wake-up signal detection and processing. The study in [6] was to primarily target low-power WUS and wake-up receiver (WUR) for power-sensitive, small form -factor devices including loT use cases (such as industrial sensors, controllers) and wearable devices. Other use cases are not precluded, e.g. extended Reality (XR) / smart glasses, smart phones, etc.

[0079] The goal was hence to support a low power wake up signal (LP-WUS) that is received by a low power wake-up receiver (LP-WUR). While the main receiver (MR) of the UE is asleep, if the LP-WUR detects an LP-WUS in between DRX ON occasions, the MR is woken up by a signal transmitted from the LP- WUR (i.e. a wake-up command), so that the MR can then listen for a paging message in the following paging occasions, and the MR can then subsequently decode any data that is transmitted by the network. Therefore, if the WUS is only transmitted shortly before paging occasions in which the target UE is paged, the MR will be woken up only when an actual paging message targeted at the UE is present in the following paging occasions. This stops the UE MR from waking up to needlessly search for a paging message during paging occasions when the network has not paged the UE, thereby reducing further batery power consumption. A WUS can also be transmited prior to paging occasions in which the UE is paged for other reasons such as TAU etc.

[0080] Figure 7 shows the relationship between the MR 71 and LP-WUR 72 of a UE. The LP-WUR 72 receives a signal, RX_sig2, and monitors for LP-WUS within RX_sig2. If the LP-WUR 72 detects an LP-WUS, it wakes up the MR 71 via a wake-up command 73, which may for example be an “ON / OFF” indication. The MR 71 then decodes its input signal, RX_sigl, and receives data 74 which can then be forwarded to the UE’s buffers or processors or the like. In some cases, RX_sig2 is the same as RX_sigl. For example, RX_sigl and RX_sig2 can both exist within the system bandwidth of an NR waveform. In other cases, RX sig 1 and RX_sig2 are different. For example, RX sig 1 could be within the system bandwidth of an NR waveform and RX_sig2 could be a narrower bandwidth signal that is in or out of band of the system bandwidth of the NR signal.

[0081] In RRC-IDLE mode, the LP-WUS can be used to wake up the MR so that the UE can monitor a paging occasion (PO). That is:

[0082] • If an LP-WUS is detected, the UE wakes up the MR and the UE decodes the PO; or

[0083] • If an LP-WUS is not detected, the MR is not woken up.

[0084] Figure 8 shows the case where an LP-WUS 81 is used to wake an RRC-IDLE mode UE MR up to monitor for a paging message during a paging occasion (PO). The LP-WUR of the UE monitors for an LP-WUS 81 during an LP-WUS monitoring window. The LP-WUR of the UE knows that if the network were to transmit an LP-WUS 81, it would be transmited during the LP-WUS monitoring window. Hence, the LP-WUR only needs to actively monitor for LP-WUS 81 during this LP-WUS monitoring window. If LP-WUS 81 is detected, the LP-WUR wakes the MR up (those skilled in the art would appreciate that this process may take some time, for example 100ms). The MR then synchronises to the downlink and monitors for PDCCH 82 during the following paging occasion. If the UE receives a PDSCH 83 containing its identifier during the PO, the UE performs an initial access procedure with the network. During the time that the MR wakes up, the MR needs to synchronise with the network and potentially read system information. It should be appreciated here that if an LP-WUS is not detected, the LP-WUR does not need to wake up the MR.

[0085] Some LP-WUR architectures have sufficiently low power consumption that they can be “ON” all the time. Other LP-WURs have a higher power consumption, or are implemented in UEs which require lower power consumption, and it is therefore advantageous for those LP-WUR to only monitor for LP- WUS in an LP-WUS monitoring window (i.e. in a DRX-like fashion).

[0086] For a LP-WUR listening out for a WUS targeted at the particular UE, the WUR further needs to accomplish a number of functions.

[0087] The WUR needs to stay relatively synchronised to the DL signal so that it can detect a WUS efficiently with a low misdetection rate. This is especially critical if the WUS signal is transmited at specific times or within specific time windows e.g. shortly before the DRX ON occasions of the UE. The WUR needs to roughly keep track of the DRX ON occasions. This is also quite critical if the UE stays in RRC-IDLE mode for extended periods as its clock can drift and mobility can also cause significant frequency offsets. Relatively good synchronisation also reduces the false alarm rate. The WUR needs to atempt to decode for a potential WUS at any time that a WUS might have been transmited. Every decoding atempt leads to the potential for a false alarm. If synchronisation is poorer, the WUR needs to atempt to decode for a potential WUS over a wider time window, due to the timing uncertainty. The wider time window means that more decoding attempts are required and the false alarm rate increases.

[0088] During any extended periods when the MR is asleep and the WUR is on, it may be necessary to carry out RRM measurements. The MR can be configured to wake up to carry out RRM measurements during RRM measurement windows / events. However, better power saving can be achieved if the WUR that is already on carries out the RRM measurements by itself. For this, the WUS would have to incorporate resources on which RRM measurements can be taken by the WUR.

[0089] In detecting and decoding the UP-WUS signal, the WUR should use as little power as possible in signal detection and decoding. The power consumption of the WUR depends very much on the kind of waveform used for transmitting the UP-WUS, the receiver processing algorithm needed for its detection and decoding and the required level of coverage i.e. the maximum distance between the base station that transmits the UP-WUS and the UE that detects and decodes the UP-WUS.

[0090] The WUR needs to receive and decode embedded WUS signalling which could comprise: the cell ID of the cell transmitting the WUS, the UE group or UE ID to which the WUS is targeted etc.

[0091] As such, a technical problem to solve is hence how to provide an LP-WUS signal that can be received by as low a complexity LP-WUR as possible, that enables a UE to increase its power-saving capabilities, whilst still properly accomplishing the functions detailed above relating to synchronisation, performance of measurements, reducing power consumption in signal detection and decoding, and properly receiving and decoding WUS signalling. Embodiments of the present technique therefore seek to provide solutions to address such a problem.

[0092] Low Power Wake-Up Signal Based on OFDM and OOK Waveforms

[0093] Figure 9 shows a part schematic, part message flow diagram representation of a wireless communications system comprising a communications device (e.g. UE) 91 and an infrastructure equipment (e.g. gNB) 92 in accordance with at least some embodiments of the present technique. The communications device 91 is configured to transmit signals to and / or receive signals from the wireless communications network, for example, to and from the infrastructure equipment 92. Specifically, the communications device 91 may be configured to transmit data to and / or receive data from the wireless communications network (e.g. to / from the infrastructure equipment 92) via a wireless radio interface provided by the wireless communications network (e.g. a Uu interface between the communications device 91 and the Radio Access Network (RAN), which includes the infrastructure equipment 92). The communications device 91 comprises a main receiver (or main receiver circuitry) 91.1, a low-power receiver (or low-power receiver circuitry) 91.2 and at least one controller (or controller circuitry) 91.3, 91.4, while the infrastructure equipment 92 comprises a transceiver (or transceiver circuitry) 92. 1, and a controller (or controller circuitry) 92.2. Each of the controllers 91.3, 91.4, 92.2 may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc. In the example of Figure 9, two controllers 91.3, 91.4 are shown, with a first controller 91.3 operatively coupled to (and hence controlling) the main receiver 91.1, and a second controller 91.4 operatively coupled to (and hence controlling) the low-power receiver 91.2. Those skilled in the art would appreciate that this would be advantageous given that the main CPU (e.g. controller 91.3) of the communications device 91 may be more powerful than a CPU (e.g. controller 91.4) connected to the low-power receiver 91.2 and would consume a lot of power if it needed to be on so as to control the low-power receiver 91.2. Of course, those skilled in the art would appreciate that in some arrangements of embodiments of the present technique, the communications device 91 may comprise a single controller (or controller circuitry) used to control both of the main receiver 91.1 and the low-power receiver 91.2. As shown in the example of Figure 9, the at least one controller 91.3, 91.4 of the communications device 91 is configured to control the communications device 91 to receive 94 a low-power wake-up signal, LP- WUS, from a wireless communications network (e.g. from the infrastructure equipment / gNB 92) via the low-power receiver 91.2 while the low-power receiver 91.2 is in an ON state and the main receiver 91.1 is in an OFF state - wherein the LP-WUS 94 comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF - and to transmit 96 to the main receiver 91.1, based on receiving the LP-WUS 94, a wake-up command indicating that the main receiver 91. 1 is to switch from the OFF state to an ON state. Here a power consumption of the low-power receiver when the low-power receiver is in the ON state is lower than a power consumption of the main receiver when the main receiver is in the ON state.

[0094] Essentially, embodiments of the present technique therefore propose that the LP-WUS is a signal which comprises both ON / OFF keying (OOK) symbols and OFDM symbols, where the symbols of the OOK portion of the LP-WUS (e.g. OFDM symbols) are OOK-modulated before transmission. In this system, for the OOK portion of the LP-WUS, there are ON symbols (which may specifically be OOK-encoded ON OFDM symbols) and OFF symbols (which may specifically be OOK-encoded OFF OFDM symbols). This enables the WUS signal to be very simple and therefore receivable by low-complexity low-power receivers (e.g. those which may be unable to receive the OFDM portion of the LP-WUS, or would consume too much power to do so).

[0095] As illustrated in Figure 10, the resource elements (REs) of the ON OFDM symbols 101 may in accordance with at least some such embodiments of the present technique be OOK-modulated such that, in the time domain, the (ON) OFDM symbol will exhibit non-zero energy, whilst the REs of the OFF OFDM symbols are each modulated such that, in the time domain, the (OFF) OFDM symbol will exhibit substantially zero energy. In other words, ON symbols may have a first energy level which is non-zero and OFF symbols may have a second energy level which is substantially zero. The modulation symbols assigned to the set of REs in the frequency domain can be optimised to produce the appropriate signal in the time domain. For example, the set of modulation symbols in the frequency domain can be optimised to minimise the peak-to-average power of the (ON) OFDM symbol signal in the time domain. The OOK- OFDM symbols 101 may then be detected at various decision points 103 by an envelope detector, with an output 102 as shown in Figure 10.

[0096] In accordance with such embodiments of the present technique, the low complexity wake-up radio (WUR) 110 at the UE may operate in such a manner as that illustrated in Figure 11. The receiver 110 is comprised of a bandpass filter 111 roughly tuned to the LP-WUS transmission frequency with a 3dB bandwidth substantially equal to the bandwidth of the LP-WUS frequency resources, followed by an envelope detector 112. The absence of a local oscillator contributes to the WUR’s 110 low power operation. The envelope detector 112 accumulates input energy during the period of one OFDM symbol. At the end of the said OFDM symbol period, the output of the energy accumulator is measured and compared to a set threshold. The output of the envelope calculating circuit of the envelope detector 112 may be such as that which is illustrated 102 in Figure 10 as described above. If the measured energy accumulator output is above the set threshold, the receiver 110 declares an ON OFDM symbol 113 or, if the measured energy accumulator output is below the set threshold, an OFF OFDM symbol 113 is declared by the receiver 110. In other words, the low-power receiver comprises a band-pass filter and an envelope detector, and the communications device may be configured, when receiving the LP-WUS, to suppress, by the band-pass filter, frequencies outside of a frequency range in which the LP-WUS is to be received such that the low-power receiver is able to receive the LP-WUS within that frequency range, to compare, by the envelope detector, an amount of energy accumulated during receipt of each of the symbols of the LP-WUS to a preconfigured threshold, and to determine, by the low-power receiver based on the comparison for each symbol, whether the energy accumulated in the duration of that symbol is above the preconfigured threshold and so the symbol is therefore an ON symbol or whether the energy accumulated in the duration of that symbol is below the preconfigured threshold and so the symbol is therefore an OFF symbol. The threshold against which the output of the energy accumulator is measured can be set based on a parameter of an automatic gain control circuit, by an estimation of a noise power at the receiver, or by any other suitable means. In some implementations, if the accumulated energy is equal to the threshold, the low-power receiver may determine that the symbol is an ON symbol, though in other implementations, such a symbol may be determined to be an OFF symbol.

[0097] The LP-WUS signal comprises a sequence of A ON / OFF OFDM symbols. So, the presence or absence of an LP-WUS is determined by further matching of the L length ON / OFF LP-WUS sequence. The further matching can take the form of correlating the sequences of ON and OFF decisions from the envelope detector with the known LP-WUS sequence(s). In other words, the communications device may be configured, when receiving the LP-WUS, to detect a sequence based on whether each symbol of the received LP-WUS is determined to be an ON symbol or an OFF symbol, and to determine, by the low- power receiver, whether the LP-WUS has been successfully received by comparing the detected sequence of ON / OFF symbols with one or more predefined LP-WUS sequences.

[0098] In some arrangements of embodiments of the present technique, the matching may be carried out using an Lth order matched filter with its impulse response set to the expected LP-WUS sequence. The input of the matched filter is the ON / OFF decisions on the output of the envelope detector (such as the output 102 of Figure 10) wherein an ON OFDM symbol represents a 1 and an OFF OFDM symbol represents a (-1) for example. In other words, the low -power receiver may comprise a matched filter that performs the step of determining whether the LP-WUS has been successfully received by comparing the detected sequence of ON / OFF symbols with the one or more predefined LP-WUS sequences.

[0099] In such arrangements, LP-WUS signalling can be achieved by the choice and transmission of one amongst AT possible different LP-WUS sequences by the network when it decides to transmit an LP- WUS. In other words, the low-power receiver may be configured to determine that the LP-WUS is one of a plurality of predefined LP-WUS sequences, wherein each of the predefined LP-WUS sequences may define different signalling information for reception by the communications device. In such arrangements, the number of signalling bits in one LP-WUS is then log2(AT). In this case, the transmitted LP-WUS sequence is identified by running M matched filters with each filter’s impulse response set to one of the M transmissible sequences. If at the end of L inputs from the envelope detector the m-th matched filter shows the highest output amplitude and that amplitude is above a threshold, then sequence m is identified as the one that was transmitted, and the signalling has thus been decoded.

[0100] On the other hand, the signalling to be carried may be comprised of the individual elements / bits of the sequence itself. In other words, the low -power receiver may be configured to determine that signalling information for reception by the communications device is carried by at least one of the symbols of the LP-WUS. In such arrangements, if there are q bits of signalling carried, then multiple matched filtering with 2qfilters can be used to identify the signalling in a similar manner to the arrangement described in the previous paragraph above.

[0101] The LP-WUS sequence may need to be repeatedly transmitted multiple times to provide redundancy. In this case, the output of the envelope detector can be accumulated sequence-wise over the repetitions prior to matched filtering. In other words, the LP-WUS may be repeatedly received by the low-power receiver in accordance with a configured number of repetitions, where here, the step of comparing the amount of energy accumulated during reception of each of the symbols of the LP-WUS to the preconfigured threshold may comprise accumulating a total of the energy accumulated during receipt of each of the symbols during each of the repetitions.

[0102] In some arrangements of embodiments of the present technique, the LP-WUS signal may be carried in the same spectrum as the main signal. In other words, the LP-WUS may be received within a same frequency band as that used by the main receiver to receive signals from the wireless communications network. Here, the main signal may refer to any downlink signal received by the main receiver from the wireless communications network, such as data carried by a PDSCH. Such a main signal may also refer to control signalling, such as that of a traditional WUS (i.e. a non-low power WUS) for example, or may refer to the OFDM portion of the LP-WUS and OOK portion of the LP-WUS being received in the same frequency band. If the main signal is OFDM-based for example, then the LP-WUS signal will occupy the designated REs in the frequency domain and will occupy as many time resources (i.e. L OFDM symbols) as are necessary to reach the required coverage level. The bandwidth occupied by the LP-WUS is thus the frequency range of the occupied REs and its time duration is the total duration of the L OFDM symbols. The LP-WUS signal, in such arrangements of embodiments of the present disclosure, can therefore be thought of as an OFDM signal that exists only on the designated REs for L OFDM symbols. The advantage of an in-band LP-WUS is that the LP-WUR does not need to tune to an out-of-band carrier for performing measurements or achieving synchronisation. Furthermore, an in-band LP-WUS means that the network does not need to assign additional out-of-band spectrum for the LP-WUS, where additional spectrum is valuable.

[0103] The transitions between full energy ON OFDM symbols and zero energy OFF OFDM symbols do not always occur between each symbol, because there may be more than one consecutive ON or OFF symbol. This therefore makes using the LP-WUS for synchronisation more difficult, as it is not always clear to the LP-WUR (if not synchronised) the exact time at which one symbol ends and the next begins. Recognising this, in some arrangements of embodiments of the present technique, each OOK symbol is Manchester encoded (MC-OOK), as is illustrated in Figure 12 for example. In other words, where the OOK symbols are Manchester encoded by the network, the ON symbols may have an energy transition in the middle of the symbol interval such that energy is high at the start of the symbol and low at the end of the symbol whilst OFF symbols may have an energy transition in the middle of the symbol interval such that energy is low at the start of the symbol and high at the end of the symbol. Alternatively, the ON symbols may have an energy transition which is low at the start of the symbol and high at the end of the symbol whilst the OFF symbols may have an energy transition which is high at the start of the symbol and low at the end of the symbol.

[0104] In MC-OOK, each time domain OOK symbol 121 has an energy transition at the mid-symbol time instant. For example, as shown in Figure 12, the ON OFDM symbol has an energy transition from high to low mid-symbol whilst the OFF OFDM symbol has an energy transition from low to high mid-symbol. It can also be such that the ON OFDM symbol has an energy transition from low to high mid-symbol whilst the OFF OFDM symbol has an energy transition from high to low mid-symbol. This means that all OFDM symbols 121 have energy with the energy in the OOK OFDM symbol 121 concentrated either only in the first half or in the second half of the time domain OFDM symbol 121.

[0105] For such arrangements, the energy accumulator of the LP-WUR still resets at the end of every OFDM symbol. The envelope detector 122 thresholds the output of the energy accumulator every half symbol and, taking the example in Figure 12, declares: an ON if the higher than set threshold peak output occurs at the end of the first half of the OFDM symbol (i.e. at ON decision points 123); or an OFF if the higher than set threshold peak output occurs at the end of the second half of the OFDM symbol (i.e. at OFF decision points 124). Alternatively, the receiver can determine whether a logic ‘ 1’ (i.e. ON) or logic ‘0’ (i.e. OFF) has been transmitted by simply comparing the output of the envelope detector 122 for the first half of the OFDM symbol with the level of the envelope detector 122 for the second half of the OFDM symbol. Since there is guaranteed to be a transition every OFDM symbol (due to the nature of the Manchester-encoded signal), clock recovery at the UE (LP-WUR) is also simplified.

[0106] In some arrangements of embodiments of the present technique, the MC-OOK OFDM symbols are formed by transmitting a symbol template which has been generated in a manner such as that which is illustrated in Figure 13.

[0107] In Figure 13 the desired time domain shape 131 for the MC-OOK OFDM symbol is input into a forward discrete Fourier transform (DFT) 132. Given the abrupt transition mid-symbol, a lot of ringing into adjacent REs of the transmitted signal can be expected. The BW Limit block 133 is a frequency domain filter that enforces localisation of the LP-WUS to be only in REs configured for LP-WUS. The output of the BWLimit block 133 then goes through an inverse DFT 134 to produce a time domain template 135 for the ON / OFF MC-OOK OFDM symbol depending on whether the desired symbol shape 131 of an ON or OFF OFDM symbol was input into the DFT 132. In other words, the wireless communications network (e.g. the infrastructure equipment) may be configured to encode the OOK symbols in accordance with Manchester coding by performing a discrete Fourier transform, DFT, on a desired time domain shape for the encoded OOK symbols, filtering the output of the DFT in the frequency domain (i.e. to ensure that the LP-WUS is carried only within frequency resources configured for carrying the LP-WUS), and performing an inverse DFT on the filtered output to produce the encoded OOK symbols. In some implementations, the samples produced by the inverse DFT function as a time domain template are stored by the infrastructure equipment and the infrastructure equipment then reads out samples from the time domain template depending on whether the desired symbol shape of the OFDM symbol was ON or OFF. In other implementations, the infrastructure can re-encode the time domain template every time an MC- OOK OFDM symbol is to be transmitted. In other implementations, a frequency domain template is produced, where the frequency domain template defines the input sample sequence to the IDFT 134, where a first sample sequence is used if an ON MC-OOK OFDM symbol is to be transmitted and a second sample sequence is used if an OFF MC-OOK OFDM symbol is to be transmitted.

[0108] An OOK based LP-WUS signal such as that described in accordance with arrangements of embodiments of the present technique above has the advantage of a low complexity envelope detector receiver. However, because of the poor signal-to-noise ratio (SNR) performance of the OOK signal, and the high noise floor of the envelope detector-based LP-WUR, long sequences (large L) and / or many repetitions of the sequence often need to be transmitted if the desired coverage is to be achieved with low rates of misdetection and false alarm. Furthermore, the power saving advantages of the low complexity receiver is compromised by the fact that the LP-WUR must stay on for a relatively longer period of time to detect all of the L symbols in the sequence, potentially over many repetitions.

[0109] In some arrangements of embodiments of the present technique, the LP-WUS comprises a few OFDM symbols that carry the required signalling concentrated in a short time interval. Some example OFDMbased LP-WUS designs are described in co-pending European patent applications [7] and [8], OFDM requires a quadrature receiver that includes a frequency oscillator and effective filtering. The rate of power consumption for such receivers is much higher than that of an envelope detector. However, the receiver stays on only for a short time as the LP-WUS signal is carried only on a few OFDM symbols, and this short signal can be received successfully due to the better SNR performance and lower noise figure of this type of LP-WUR. OFDM-based LP-WUS designs may also be better suited for RRM measurements and re synchronisation of the LP-WUR during long RRC-IDLE periods. However, the downside of such arrangements is that lower-complexity WURs will not be able to receive such OFDMbased LP-WUS signals, because they simply may not have the required processing capability and / or battery powers required to do so.

[0110] Recognising both the advantages and disadvantages of OFDM-based LP-WUS designs as discussed in the paragraph above therefore, embodiments of the present technique therefore propose that OFDM-based LP-WUS is combined with MC-OOK based LP-WUS as described above with reference to Figure 9. Here, the LP-WUS may comprise relatively few OFDM symbols compared to the number of OOK symbols as described above. In other words, the number of OFDM symbols of the LP-WUS may be lower than the number of OOK symbols of the LP-WUS (and where both the OFDM symbols and the OOK symbols may comprise the same wake-up signalling).

[0111] One example of this is shown in Figure 14 which specifically uses time multiplexing between the OFDMbased WUS symbols 141 and the MC-OOK based OFDM WUS symbols 142. In other words, the OFDM symbols of the LP-WUS and the OOK symbols of the LP-WUS may be separated from each other in time. In such arrangements, N full OFDM symbols comprise an OFDM based LP-WUS 141. This is then followed by L MC-OOK OFDM symbols 142 that typically use fewer resources in the frequency domain (i .e . have a lower bandwidth) than each of the N OFDM symbols of the OFDM-based WU S 141. That is, in other words, the OFDM symbols of the LP-WUS may be receivable by the low -power receiver across a wider frequency range than the OOK symbols of the LP-WUS. Receivers that can deploy sufficient processing capability in the LP-WUR can receive the OFDM-based LP-WUS 141 - and then turn off upon receiving these without needing to further receive the MC-OOK-based WUS 142 - while receivers with limited battery power and / or processing capability for the WUR can ignore the N initial OFDM symbols 141 of the WUS and receive instead the L symbols of the MC-OOK based WUS 142. These lower capability receivers can use the envelope of the OFDM-based WUS symbols 141 for other purposes. For example, these symbols can be used to set a detection threshold for the MC-OOK based WUS portion 142. In order to set this threshold, the power of the OFDM-based WUS 141 relative to the power of the MC-OOK based WUS 142 needs to be known. This power ratio can be signalled in LP- WUS configuration signalling. The low-power receiver may be configured to determine that signalling information for reception by the communications device is carried by at least one of the OFDM symbols of the LP-WUS but is not carried by any of the OOK symbols.

[0112] In some arrangements of embodiments of the present technique, the signalling incorporated in the WUS can be forward error correction (FEC) protected and modulated on the resource elements of the OFDMbased LP-WUS symbols to be decoded by the receiver. In other words, the at least one of the OFDM symbols may comprise one or more error correction codewords associated with the signalling information. Alternatively, uncoded signalling can be carried robustly in cyclic shifts of the OFDM symbols as described in co-pending European patent applications [7] and [8] for example.

[0113] In such arrangements of embodiments of the present technique as those described above, in which a combination of OFDM-based WUS symbols and MC-OOK-based WUS symbols may be transmitted, the envelope detector used for receiving the MC-OOK LP-WUS must avoid the OFDM-based LP-WUS symbols as these would always show energy in both halves of the symbol. The MC-OOK receiver could however use these OFDM symbols as a synchronisation signal if it could detect them using the half symbol envelope detector.

[0114] Recognising this, in some arrangements of embodiments of the present technique, these OFDM-based LP-WUS symbols can be superposed (by addition) on the MC-OOK symbols. This superposition should be done in a manner so that the MC-OOK envelope detector does not need to avoid any OFDM symbols. In other words, the OFDM symbols of the LP-WUS may be superposed on the OOK symbols of the LP- WUS.

[0115] In some such arrangements, this superposition is weighted with a weight w (where w < 1) is used to multiply the MC-OOK signal and another weight (1-w) used to multiply the OFDM-based WUS before the superposition. In other words, the OFDM symbols of the LP-WUS may be weighted with a first weighting value and the OOK symbols of the LP-WUS may be weighted with a second weighting value different to the first weighting value. If the MC-OOK signal is denoted xwc(t) and the OFDM-based signal is denoted xoFDMft), the transmitted signal, would be:

[0116] Xtr(t) = W * XMc t) + (1-W) * XoFDMft)

[0117] In this case, the MC-OOK receiver would filter out the OFDM-based signal, XOFDM(L) and the OFDMbased receiver could cancel the MC-OOK signal, xwc(t). For example, if the xwc(t) signal is a synchronisation signal with a known pattern, the OFDM receiver could subtract that signal pattern before decoding the OFDM signal. Alternatively, if the xMC( ) signal is a data bearing signal (where the transitions would be unknown to the OFDM receiver), the OFDM receiver could demodulate the OFDM symbol by hypothesis testing of the MC-OOK signal (i.e. the OFDM receiver could attempt to demodulate an OFDM symbol based on both the hypotheses that the MC-OOK signal transmits logic ‘0’ and that the MC-OOK signal transmits logic ‘ 1 ’ and to then decode on the basis of whether the first hypothesis or the second hypothesis is more likely. Alternatively, the LLRs (log-likelihood ratios) can take account of the estimated correctness of the MC-OOK signal’s logic ‘0’ / logic ‘ 1 ’ determination).

[0118] In some arrangements of embodiments of the present technique, the OFDM-based LP-WUS symbols may use double the subcarrier spacing (SCS) of the MC-OOK OFDM symbols. In other words, the OFDM symbols of the LP-WUS may be arranged in accordance with a first subcarrier spacing and the OOK symbols of the LP-WUS may be arranged in accordance with a second subcarrier spacing different to the first subcarrier spacing. This means that the OFDM-based WUS symbols have half the duration of the MC-OOK OFDM symbols. This allows them to be superposed only on the high energy half of the MC- OOK OFDM symbol. An example of this is illustrated in Figure 15, where the desired OFDM symbols 151 have only half the duration of the desired MC-OOK symbols 152, where the OFDM symbols 151 are matched in time to the high energy halves of the MC-OOK symbols 152 before being superposed on them.

[0119] In some arrangements of embodiments of the present technique, the superposed symbol is generated in a manner such as that which is illustrated in Figure 16. In the block diagram of Figure 16, the OFDM based WUS symbol is generated separately and then superposed on the MC-OOK symbol template. To do so, the WUS signalling 161 is first OFDM modulated 162, and then prior to weighted superposition, the OFDM based WUS symbol - which is only half the length of the MC-OOK symbol template - is either delayed 163 (zeros appended to its beginning to double its length) or advanced 163 (zeros appended from its end to double its length). The delayed or advanced WUS symbols are then weighted 164 by a weight w.

[0120] Separately to this, the MC-OOK LP-WUS symbols are generated; for example, in the same (or a similar) manner as that described above with respect to Figure 13. That is, the desired time domain shape 165 for the MC-OOK symbol is input into a forward DFT 166 before the output of this is fed into aBW Limit block 167. The output of the BW Limit block 167 then goes through an inverse DFT 168 to produce a time domain template for the ON / OFF MC-OOK symbols which are then weighted 169 by a weight (1- w). The generated and weighted OFDM-based WUS symbols are then superposed 170 on these generated and weighted MC-OOK WUS symbols to produce the superposed OFDM LP-WUS symbols 171. In other words, the wireless communications network (e.g. the infrastructure equipment) may be configured to generate the OFDM symbols of the LP-WUS and the OOK symbols of the LP-WUS prior to superposing the generated OFDM symbols of the LP-WUS on the OOK symbols of the LP-WUS.

[0121] In some other arrangements of embodiments of the present technique, in the generation of the superposed WUS signal, the OFDM-based WUS symbols may be generated and modulated with the signalling data as desired. Each OFDM-based WUS symbol is then superposed on the non-zero energy half of the desired MC-OOK symbol. The resulting superposition may then be input into the circuit of Figure 13 to generate the superposed OFDM symbols to be transmitted. In other words, the wireless communications network (e.g. the infrastructure equipment) may be configured to generate the OFDM symbols of the LP- WUS, to superpose the OFDM symbols of the LP-WUS on a desired time domain shape for the encoded OOK symbols of the LP-WUS, to perform a DFT on the superposed symbols of the LP-WUS, to filter the output of the DFT in the frequency domain (i.e. to ensure that the superposed symbols of the LP-WUS are carried only within frequency resources configured for carrying the LP-WUS), and to perform an inverse DFT on the filtered output to produce the superposed symbols of the LP-WUS.

[0122] Either method (i.e. that shown in Figure 16 or that described in the paragraph above) allows the OFDMbased WUS symbols to carry signalling data either through modulation of its REs or by cyclic shifts of the time domain symbol (the cyclic shift of the OFDM-based WUS is now possible since a full symbol length of the higher-SCS OFDM-based WUS fits within the half symbol length of the lower-SCS MC- OOK WUS). At the WUR of the UE, the OFDM-based WUS symbols can be decoded as described in co-pending European patent applications [7] and [8] if desired with a higher complexity OFDM receiver. A lower complexity WUR based on envelope detection, such as that shown in Figure 11 and described above) can decode the MC-OOK signal inclusive of the MC-OOK OFDM symbols over which the OFDM-based WUS OFDM symbols have been superposed.

[0123] Figure 17 shows a flow diagram illustrating an example process of communications in a communications system in accordance with embodiments of the present technique. The process shown by Figure 17 is a method of operating a communications device comprising a low-power receiver and a main receiver (where a power consumption of the low-power receiver when the low-power receiver is in the ON state is lower than a power consumption of the main receiver when the main receiver is in the ON state).

[0124] The method begins in step SI. The method comprises, in step S2, receiving a low -power wake-up signal, LP-WUS, from a wireless communications network (e.g. from an infrastructure equipment) via the low- power receiver while the low-power receiver is in an ON state and the main receiver is in an OFF state. Here, the LP-WUS comprises one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF. In step S3, the method comprises transmitting to the main receiver, based on receiving the LP-WUS, a wake-up command indicating that the main receiver is to switch from the OFF state to an ON state. The process ends in step S4.

[0125] Those skilled in the art would appreciate that the method shown by Figure 17 may be adapted in accordance with embodiments of the present technique. For example, other intermediate steps may be included in this 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 Figure 10 and with further reference to Figures 11 to 16, 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.

[0126] The following numbered paragraphs provide further example aspects and features of the present technique:

[0127] Paragraph 1. A method of operating a communications device comprising a low-power receiver and a main receiver, the method comprising receiving a low-power wake-up signal, LP-WUS, from a wireless communications network via the low-power receiver while the low-power receiver is in an ON state and the main receiver is in an OFF state, and transmitting to the main receiver, based on receiving the LP-WUS, a wake-up command indicating that the main receiver is to switch from the OFF state to an ON state, wherein a power consumption of the low-power receiver when the low-power receiver is in the ON state is lower than a power consumption of the main receiver when the main receiver is in the ON state, and wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

[0128] Paragraph 2. A method according to Paragraph 1, wherein the one or more OOK symbols of the LP- WUS are OFDM symbols.

[0129] Paragraph 3. A method according to Paragraph 1 or Paragraph 2, wherein the LP-WUS is received within a same frequency band as that used by the main receiver to receive signals from the wireless communications network.

[0130] Paragraph 4. A method according to any of Paragraphs 1 to 3, wherein ON symbols have a first energy level which is non-zero and OFF symbols have a second energy level which is substantially zero. Paragraph 5. A method according to any of Paragraphs 1 to 4, wherein the low-power receiver comprises a band-pass filter and an envelope detector, and the step of receiving the LP-WUS comprises suppressing, by the band-pass filter, frequencies outside of a frequency range in which the LP- WUS is to be received such that the low -power receiver is able to receive the LP-WUS within that frequency range, comparing, by the envelope detector, an amount of energy accumulated during receipt of each of the symbols of the LP-WUS to a preconfigured threshold, and determining, by the low-power receiver based on the comparison for each symbol, whether the amount of energy accumulated during receipt of that symbol is above the preconfigured threshold and is therefore an ON symbol or whether the amount of energy accumulated during receipt of that symbol is below the preconfigured threshold and is therefore an OFF symbol.

[0131] Paragraph 6. A method according to Paragraph 5, wherein the step of receiving the LP-WUS further comprises detecting a sequence based on whether each symbol of the received LP-WUS is determined to be an ON symbol or an OFF symbol, and determining, by the low-power receiver, whether the LP-WUS has been successfully received by comparing the detected sequence of ON / OFF symbols with one or more predefined LP-WUS sequences. Paragraph 7. A method according to Paragraph 6, wherein the low-power receiver comprises a matched filter that performs the step of determining whether the LP-WUS has been successfully received by comparing the detected sequence of ON / OFF symbols with the one or more predefined LP-WUS sequences.

[0132] Paragraph 8. A method according to any of Paragraphs 5 to 7, wherein the LP-WUS is repeatedly received by the low-power receiver in accordance with a configured number of repetitions, and wherein the step of comparing the amount of energy accumulated during receipt of each of the symbols of the LP-WUS to the preconfigured threshold comprises accumulating a total of the energy accumulated during receipt of each of the symbols during each of the repetitions. Paragraph 9. A method according to any of Paragraphs 1 to 8, comprising determining, by the low-power receiver, that the LP-WUS is one of a plurality of predefined LP- WUS sequences, wherein each of the predefined LP-WUS sequences defines different signalling information for reception by the communications device.

[0133] Paragraph 10. A method according to any of Paragraphs 1 to 9, comprising determining, by the low-power receiver, that signalling information for reception by the communications device is carried by at least one of the symbols of the LP-WUS.

[0134] Paragraph 11. A method according to any of Paragraphs 1 to 10, wherein either: the ON symbols have an energy transition which is high at the start of the symbol and low at the end of the symbol and the OFF symbols have an energy transition which is low at the start of the symbol and high at the end of the symbol, or the ON symbols have an energy transition which is low at the start of the symbol and high at the end of the symbol and the OFF symbols have an energy transition which is high at the start of the symbol and low at the end of the symbol.

[0135] Paragraph 12. A method according to any of Paragraphs 1 to 11, wherein the number of OFDM symbols of the LP-WUS is lower than the number of OOK symbols of the LP-WUS.

[0136] Paragraph 13. A method according to Paragraph 12, wherein the OFDM symbols of the LP-WUS are receivable by the low-power receiver across a wider frequency range than the OOK symbols of the LP- WUS.

[0137] Paragraph 14. A method according to any of Paragraphs 1 to 13, wherein the at least one of the OFDM symbols comprises one or more error correction codewords associated with the wake-up signalling.

[0138] Paragraph 15. A method according to any of Paragraphs 1 to 14, wherein the OFDM symbols of the LP- WUS and the OOK symbols of the LP-WUS are separated from each other in time.

[0139] Paragraph 16. A method according to any of Paragraphs 1 to 15, wherein the OFDM symbols of the LP- WUS are superposed on the OOK symbols of the LP-WUS.

[0140] Paragraph 17. A method according to Paragraph 16, wherein the OFDM symbols of the LP-WUS are weighted with a first weighting value and the OOK symbols of the LP-WUS are weighted with a second weighting value different to the first weighting value.

[0141] Paragraph 18. A method according to Paragraph 16 or Paragraph 17, wherein the OFDM symbols of the LP-WUS are arranged in accordance with a first subcarrier spacing and the OOK symbols of the LP- WUS are arranged in accordance with a second subcarrier spacing different to the first subcarrier spacing. Paragraph 19. A communications device comprising a low -power receiver, a main receiver, and at least one controller configured to control the communications device to receive a low-power wake-up signal, LP-WUS, from a wireless communications network via the low-power receiver while the low-power receiver is in an ON state and the main receiver is in an OFF state, and to transmit to the main receiver, based on receiving the LP-WUS, a wake-up command indicating that the main receiver is to switch from the OFF state to an ON state, wherein a power consumption of the low-power receiver when the low-power receiver is in the ON state is lower than a power consumption of the main receiver when the main receiver is in the ON state, and wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

[0142] Paragraph 20. Circuitry for a communications device comprising low-power receiver circuitry, main receiver circuitry, and at least one controller circuitry configured to control the communications device to receive a low-power wake-up signal, LP-WUS, from a wireless communications network via the low-power receiver circuitry while the low-power receiver circuitry is in an ON state and the main receiver circuitry is in an OFF state, and to transmit to the main receiver circuitry, based on receiving the LP-WUS, a wake-up command indicating that the main receiver circuitry is to switch from the OFF state to an ON state, wherein a power consumption of the low-power receiver circuitry when the low-power receiver circuitry is in the ON state is lower than a power consumption of the main receiver circuitry when the main receiver circuitry is in the ON state, and wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

[0143] Paragraph 21. A method of operating an infrastructure equipment forming part of a wireless communications network, the method comprising transmitting a low -power wake-up signal, LP-WUS, to a communications device for reception by a low -power receiver of the communications device, wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

[0144] Paragraph 22. A method according to Paragraph 21, wherein the one or more OOK symbols of the LP- WUS are OFDM symbols.

[0145] Paragraph 23. A method according to Paragraph 21 or Paragraph 22, wherein the LP-WUS is transmitted within a same frequency band as that used by the infrastructure equipment to transmit signals to and to receive signals from the main receiver of the communications device.

[0146] Paragraph 24. A method according to any of Paragraphs 21 to 23, wherein ON symbols have a first energy level which is non-zero and OFF symbols have a second energy level which is substantially zero. Paragraph 25. A method according to any of Paragraphs 21 to 24, wherein the LP-WUS is one of a plurality of predefined LP-WUS sequences, wherein each of the predefined LP-WUS sequences defines different signalling information for reception by the communications device.

[0147] Paragraph 26. A method according to any of Paragraphs 21 to 25, comprising transmitting signalling information for reception by the communications device, wherein the signalling information is carried by at least one of the symbols of the LP-WUS.

[0148] Paragraph 27. A method according to any of Paragraphs 21 to 26, comprising encoding the OOK symbols in accordance with Manchester coding, such that either: the ON symbols have an energy transition which is high at the start of the symbol and low at the end of the symbol and the OFF symbols have an energy transition which is low at the start of the symbol and high at the end of the symbol, or the ON symbols have an energy transition which is low at the start of the symbol and high at the end of the symbol and the OFF symbols have an energy transition which is high at the start of the symbol and low at the end of the symbol.

[0149] Paragraph 28. A method according to Paragraph 27, wherein the step of encoding the OOK symbols in accordance with Manchester coding comprises performing a discrete Fourier transform, DFT, on a desired time domain shape for the encoded OOK symbols, filtering the output of the DFT in the frequency domain, and performing an inverse DFT on the filtered output to produce the encoded OOK symbols.

[0150] Paragraph 29. A method according to any of Paragraphs 21 to 28, wherein the number of OFDM symbols of the LP-WUS is lower than the number of OOK symbols of the LP-WUS. Paragraph 30. A method according to Paragraph 29, wherein the OFDM symbols of the LP-WUS are receivable by the low-power receiver of the communications device across a wider frequency range than the OOK symbols of the LP-WUS.

[0151] Paragraph 31. A method according to any of Paragraphs 21 to 30, wherein the at least one of the OFDM symbols comprises one or more error correction codewords associated with the signalling information.

[0152] Paragraph 32. A method according to any of Paragraphs 21 to 31, comprising multiplexing the OFDM symbols of the LP-WUS and the OOK symbols of the LP-WUS to be separated from each other in time.

[0153] Paragraph 33. A method according to any of Paragraphs 21 to 32, comprising superposing the OFDM symbols of the LP-WUS on the OOK symbols of the LP-WUS.

[0154] Paragraph 34. A method according to Paragraph 33, comprising weighting the OFDM symbols of the LP-WUS with a first weighting value, and weighting the OOK symbols of the LP-WUS with a second weighting value different to the first weighting value.

[0155] Paragraph 35. A method according to Paragraph 33 or Paragraph 34, comprising arranging the OFDM symbols of the LP-WUS in accordance with a first subcarrier spacing, and arranging the OOK symbols of the LP-WUS in accordance with a second subcarrier spacing different to the first subcarrier spacing.

[0156] Paragraph 36. A method according to any of Paragraphs 33 to 35, comprising generating the OFDM symbols of the LP-WUS and the OOK symbols of the LP-WUS prior to superposing the generated OFDM symbols of the LP-WUS on the OOK symbols of the LP-WUS. Paragraph 37. A method according to any of Paragraphs 21 to 36, comprising generating the OFDM symbols of the LP-WUS, superposing the OFDM symbols of the LP-WUS on a desired time domain shape for the encoded OOK symbols of the LP-WUS, performing a DFT on the superposed symbols of the LP-WUS, filtering the output of the DFT in the frequency domain, and performing an inverse DFT on the filtered output to produce the superposed symbols of the LP-

[0157] WUS.

[0158] Paragraph 38. An infrastructure equipment forming part of a wireless communications network, the infrastructure equipment comprising transceiver circuitry, and controller circuitry configured in combination with the transceiver circuitry to transmit a low-power wake-up signal, LP-WUS, to a communications device for reception by a low-power receiver of the communications device, wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

[0159] Paragraph 39. Circuitry for an infrastructure equipment forming part of a wireless communications network, the infrastructure equipment comprising transceiver circuitry, and controller circuitry configured in combination with the transceiver circuitry to transmit a low-power wake-up signal, LP-WUS, to a communications device for reception by a low-power receiver of the communications device, wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

[0160] Paragraph 40. A wireless communications system comprising a communications device according to Paragraph 19 and an infrastructure equipment according to Paragraph 38. Paragraph 41. A computer program comprising instructions which, when loaded onto a computer, cause the computer to perform a method according to any of Paragraphs 1 to 18 or Paragraphs 21 to 37.

[0161] Paragraph 42. A non-transitory computer-readable storage medium storing a computer program according to Paragraph 41.

[0162] It will be appreciated that the above description for clarity has described embodiments with reference to different functional units, circuitry and / or processors. However, it will be apparent that any suitable distribution of functionality between different functional units, circuitry and / or processors may be used without detracting from the embodiments.

[0163] Described embodiments may be implemented in any suitable form including hardware, software, firmware or any combination of these. Described embodiments may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. The elements and components of any embodiment may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the disclosed embodiments may be implemented in a single unit or may be physically and functionally distributed between different units, circuitry and / or processors.

[0164] Although the present disclosure has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognise that various features of the described embodiments may be combined in any manner suitable to implement the technique.

[0165] References

[0166] [1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radio access”, John Wiley and Sons, 2009.

[0167] [2] TR 38.913, “3rdGeneration Partnership Project; Technical Specification Group Radio Access Network; Study on Scenarios and Requirements for Next Generation Access Technologies

[0168] (Release 14)”, 3GPP, vl4.3.0, August 2017.

[0169] [3] Rl-1708311, “Idle Mode Power Efficiency Reduction,” Sierra Wireless, RAN1#89.

[0170] [4] TS 38.213, “Physical layer procedures for control (Release 18)”, 3GPP, vl8.1.0, December 2023.

[0171] [5] TR 38.840, “NR: Study on UE Power Saving (Release 16, vO.1.0)”, 3GPP, November 2018. [6] RP-222644, “Revised SID: Study on low -power Wake-up Signal and Receiver for NR”,

[0172] RANP#97e, September 2022.

[0173] [7] European patent application with application number EP23185615.4.

[0174] [8] European patent application published under number EP3665882.

Claims

CLAIMSWhat is claimed is:

1. A method of operating a communications device comprising a low-power receiver and a main receiver, the method comprising receiving a low-power wake-up signal, LP-WUS, from a wireless communications network via the low-power receiver while the low-power receiver is in an ON state and the main receiver is in an OFF state, and transmitting to the main receiver, based on receiving the LP-WUS, a wake-up command indicating that the main receiver is to switch from the OFF state to an ON state, wherein a power consumption of the low-power receiver when the low-power receiver is in the ON state is lower than a power consumption of the main receiver when the main receiver is in the ON state, and wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

2. A method according to Claim 1, wherein the one or more OOK symbols of the LP-WUS are OFDM symbols.

3. A method according to Claim 1, wherein the LP-WUS is received within a same frequency band as that used by the main receiver to receive signals from the wireless communications network.

4. A method according to Claim 1, wherein ON symbols have a first energy level which is non-zero and OFF symbols have a second energy level which is substantially zero.

5. A method according to Claim 1, wherein the low-power receiver comprises a band-pass filter and an envelope detector, and the step of receiving the LP-WUS comprises suppressing, by the band-pass filter, frequencies outside of a frequency range in which the LP- WUS is to be received such that the low -power receiver is able to receive the LP-WUS within that frequency range, comparing, by the envelope detector, an amount of energy accumulated during receipt of each of the symbols of the LP-WUS to a preconfigured threshold, and determining, by the low-power receiver based on the comparison for each symbol, whether the amount of energy accumulated during receipt of that symbol is above the preconfigured threshold and is therefore an ON symbol or whether the amount of energy accumulated during receipt of that symbol is below the preconfigured threshold and is therefore an OFF symbol.

6. A method according to Claim 5, wherein the step of receiving the LP-WUS further comprises detecting a sequence based on whether each symbol of the received LP-WUS is determined to be an ON symbol or an OFF symbol, and determining, by the low-power receiver, whether the LP-WUS has been successfully received by comparing the detected sequence of ON / OFF symbols with one or more predefined LP-WUS sequences.

7. A method according to Claim 6, wherein the low-power receiver comprises a matched filter that performs the step of determining whether the LP-WUS has been successfully received by comparing the detected sequence of ON / OFF symbols with the one or more predefined LP-WUS sequences.

8. A method according to Claim 5, wherein the LP-WUS is repeatedly received by the low-power receiver in accordance with a configured number of repetitions, and wherein the step of comparing the amount of energy accumulated during receipt of each of the symbols of the LP-WUS to the preconfigured threshold comprises accumulating a total of the energy accumulated during receipt of each of the symbols during each of the repetitions.

9. A method according to Claim 1, comprising determining, by the low-power receiver, that the LP-WUS is one of a plurality of predefined LP- WUS sequences, wherein each of the predefined LP-WUS sequences defines different signalling information for reception by the communications device.

10. A method according to Claim 1, comprising determining, by the low-power receiver, that signalling information for reception by the communications device is carried by at least one of the symbols of the LP-WUS.

11. A method according to Claim 1, wherein either: the ON symbols have an energy transition which is high at the start of the symbol and low at the end of the symbol and the OFF symbols have an energy transition which is low at the start of the symbol and high at the end of the symbol, or the ON symbols have an energy transition which is low at the start of the symbol and high at the end of the symbol and the OFF symbols have an energy transition which is high at the start of the symbol and low at the end of the symbol.

12. A method according to Claim 1, wherein the number of OFDM symbols of the LP-WUS is lower than the number of OOK symbols of the LP-WUS.

13. A method according to Claim 12, wherein the OFDM symbols of the LP-WUS are receivable by the low-power receiver across a wider frequency range than the OOK symbols of the LP-WUS.

14. A method according to Claim 1, wherein the at least one of the OFDM symbols comprises one or more error correction codewords associated with the wake-up signalling.

15. A method according to Claim 1, wherein the OFDM symbols of the LP-WUS and the OOK symbols of the LP-WUS are separated from each other in time.

16. A method according to Claim 1, wherein the OFDM symbols of the LP-WUS are superposed on the OOK symbols of the LP-WUS.

17. A method according to Claim 16, wherein the OFDM symbols of the LP-WUS are weighted with a first weighting value and the OOK symbols of the LP-WUS are weighted with a second weighting value different to the first weighting value.

18. A method according to Claim 16, wherein the OFDM symbols of the LP-WUS are arranged in accordance with a first subcarrier spacing and the OOK symbols of the LP-WUS are arranged in accordance with a second subcarrier spacing different to the first subcarrier spacing.

19. A communications device comprising a low -power receiver, a main receiver, andat least one controller configured to control the communications device to receive a low-power wake-up signal, LP-WUS, from a wireless communications network via the low-power receiver while the low-power receiver is in an ON state and the main receiver is in an OFF state, and to transmit to the main receiver, based on receiving the LP-WUS, a wake-up command indicating that the main receiver is to switch from the OFF state to an ON state, wherein a power consumption of the low-power receiver when the low-power receiver is in the ON state is lower than a power consumption of the main receiver when the main receiver is in the ON state, and wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

20. Circuitry for a communications device comprising low-power receiver circuitry, main receiver circuitry, and at least one controller circuitry configured to control the communications device to receive a low-power wake-up signal, LP-WUS, from a wireless communications network via the low-power receiver circuitry while the low-power receiver circuitry is in an ON state and the main receiver circuitry is in an OFF state, and to transmit to the main receiver circuitry, based on receiving the LP-WUS, a wake-up command indicating that the main receiver circuitry is to switch from the OFF state to an ON state, wherein a power consumption of the low-power receiver circuitry when the low-power receiver circuitry is in the ON state is lower than a power consumption of the main receiver circuitry when the main receiver circuitry is in the ON state, and wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

21. A method of operating an infrastructure equipment forming part of a wireless communications network, the method comprising transmitting a low -power wake-up signal, LP-WUS, to a communications device for reception by a low -power receiver of the communications device, wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

22. A method according to Claim 21, wherein the one or more OOK symbols of the LP-WUS are OFDM symbols.

23. A method according to Claim 21, wherein the LP-WUS is transmitted within a same frequency band as that used by the infrastructure equipment to transmit signals to and to receive signals from the main receiver of the communications device.

24. A method according to Claim 21, wherein ON symbols have a first energy level which is nonzero and OFF symbols have a second energy level which is substantially zero.

25. A method according to Claim 21, wherein the LP-WUS is one of a plurality of predefined LP- WUS sequences, wherein each of the predefined LP-WUS sequences defines different signalling information for reception by the communications device.

26. A method according to Claim 21, comprising transmitting signalling information for reception by the communications device, wherein the signalling information is carried by at least one of the symbols of the LP-WUS.

27. A method according to Claim 21, comprising encoding the OOK symbols in accordance with Manchester coding, such that either: the ON symbols have an energy transition which is high at the start of the symbol and low at the end of the symbol and the OFF symbols have an energy transition which is low at the start of the symbol and high at the end of the symbol, or the ON symbols have an energy transition which is low at the start of the symbol and high at the end of the symbol and the OFF symbols have an energy transition which is high at the start of the symbol and low at the end of the symbol.

28. A method according to Claim 27, wherein the step of encoding the OOK symbols in accordance with Manchester coding comprises performing a discrete Fourier transform, DFT, on a desired time domain shape for the encoded OOK symbols, filtering the output of the DFT in the frequency domain, and performing an inverse DFT on the filtered output to produce the encoded OOK symbols.

29. A method according to Claim 21, wherein the number of OFDM symbols of the LP-WUS is lower than the number of OOK symbols of the LP-WUS.

30. A method according to Claim 29, wherein the OFDM symbols of the LP-WUS are receivable by the low-power receiver of the communications device across a wider frequency range than the OOK symbols of the LP-WUS.

31. A method according to Claim 21 , wherein the at least one of the OFDM symbols comprises one or more error correction codewords associated with the signalling information.

32. A method according to Claim 21, comprising multiplexing the OFDM symbols of the LP-WUS and the OOK symbols of the LP-WUS to be separated from each other in time.

33. A method according to Claim 21, comprising superposing the OFDM symbols of the LP-WUS on the OOK symbols of the LP-WUS.

34. A method according to Claim 33, comprising weighting the OFDM symbols of the LP-WUS with a first weighting value, and weighting the OOK symbols of the LP-WUS with a second weighting value different to the first weighting value.

35. A method according to Claim 33, comprising arranging the OFDM symbols of the LP-WUS in accordance with a first subcarrier spacing, andarranging the OOK symbols of the LP-WUS in accordance with a second subcarrier spacing different to the first subcarrier spacing.

36. A method according to Claim 33, comprising generating the OFDM symbols of the LP-WUS and the OOK symbols of the LP-WUS prior to superposing the generated OFDM symbols of the LP-WUS on the OOK symbols of the LP-WUS.

37. A method according to Claim 21, comprising generating the OFDM symbols of the LP-WUS, superposing the OFDM symbols of the LP-WUS on a desired time domain shape for the encoded OOK symbols of the LP-WUS, performing a DFT on the superposed symbols of the LP-WUS, filtering the output of the DFT in the frequency domain, and performing an inverse DFT on the filtered output to produce the superposed symbols of the LP- WUS.

38. An infrastructure equipment forming part of a wireless communications network, the infrastructure equipment comprising transceiver circuitry, and controller circuitry configured in combination with the transceiver circuitry to transmit a low-power wake-up signal, LP-WUS, to a communications device for reception by a low-power receiver of the communications device, wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

39. Circuitry for an infrastructure equipment forming part of a wireless communications network, the infrastructure equipment comprising transceiver circuitry, and controller circuitry configured in combination with the transceiver circuitry to transmit a low-power wake-up signal, LP-WUS, to a communications device for reception by a low-power receiver of the communications device, wherein the LP-WUS comprises one or more orthogonal frequency division multiplexing, OFDM, symbols and one or more on-off keying, OOK, symbols, wherein the OOK symbols are each defined as either ON or OFF.

40. A wireless communications system comprising a communications device according to Claim 19 and an infrastructure equipment according to Claim 38.

41. A computer program comprising instructions which, when loaded onto a computer, cause the computer to perform a method according to Claim 1 or Claim 21.

42. A non-transitory computer-readable storage medium storing a computer program according to Claim 41.

Images