Methods, communications apparatus and devices

Abstract

A method of operating a reader device forming part of a wireless communications network and configured to transmit signals to and / or to receive signals from one or more other tag / Ambient IoT (A-IoT) devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices. The method comprises transmitting a reader-to-device (R2D) signal for receipt by a tag / A-IoT device, wherein the R2D signal comprises one or more packets. Each packet comprises orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation. The packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols. The format of the control information part is different to the format of the data bearing part.

Description

[0001] METHODS, COMMUNICATIONS APPARATUS AND DEVICES

[0002] BACKGROUND

[0003] Field of the Disclosure

[0004] The present disclosure relates to methods, a communications apparatus and devices. The present disclosure claims the Paris Convention priority to European patent application number EP24204560.7 filed on 3 October 2024, the contents of which are incorporated herein by reference in its entirety.

[0005] Background

[0006] The “background” description provided is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in the background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure.

[0007] Current and future wireless communications networks are expected routinely and efficiently to support communications with an ever-increasing range of devices associated with a wider range of data traffic profiles and types. For example, wireless communications networks will be expected efficiently to support communications with devices including reduced complexity devices, machine type communication (MTC) devices, high resolution video displays, virtual reality headsets, extended Reality (XR) and so on. Some of these different types of devices may be deployed in very large numbers, for example low complexity devices for supporting the “The Internet of Things”, and may typically be associated with the transmissions of relatively small amounts of data with relatively high latency tolerance. Other types of device, for example, devices supporting high-definition video streaming, may be associated with transmissions of relatively large amounts of data with relatively low latency tolerance. Other types of device, for example devices used for autonomous vehicle communications and for other critical applications, may be characterised by data that should be transmitted through the network with low latency and high reliability. A single device type might also be associated with different traffic profiles / characteristics depending on the application(s) it is running. For example, different considerations may apply for efficiently supporting data exchange with a smartphone when it is running a video streaming application (high downlink data) as compared to when it is running an Internet browsing application (sporadic uplink and downlink data) or being used for voice communications by an emergency responder in an emergency scenario (data subject to stringent reliability and latency requirements).

[0008] In view of this there is expected to be a desire for current wireless communications networks, for example those which may be referred to as 5G or new radio (NR) systems / new radio access technology (RAT) systems, or indeed future 6G wireless communications, as well as future iterations / releases of existing systems, efficiently to support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles and requirements. 5G NR has continuously evolved and the current work plan includes 5 G-NR- Advanced in which some further enhancements are expected, especially to support new use-cases / scenarios with higher requirements. A further area of study which has developed concerns the use of low complexity devices, which may use power from incident radiation for communicating or backscattering received signals. Such devices may be referred to as tags or Ambient loT devices (tags / A-IoT). Improving communication with such devices can represent a technical challenge.

[0009] SUMMARY

[0010] The present disclosure can help address or mitigate at least some of the issues discussed above.

[0011] According to example embodiments a communications device acting as a reader for a tag / A-IoT device and a method of operating a reader device for a tag / A-IoT is disclosed. The reader forms part of a wireless communications network and is configured to transmit signals to and / or to receive signals from one or more other tag / A-IoT devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices. The transmitted and received signals should therefore be compatible with and harmonious with the radio access interface. The method comprises transmitting a reader-to-device (R2D) signal for receipt by a tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

[0012] According to various disclosed examples, the different format of the control information can provide a more robust communication of the control information than data carried by the data bearing part.

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

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

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Non-limiting embodiments and advantages of the present disclosure are explained with reference to the following detailed description taken in conjunction with the accompanying drawings, in which like parts have the same numerical designations and wherein:

[0017] Figures 1 A and IB schematically represent examples of communication systems in which tags are deployed within a coverage area of an infrastructure equipment (e.g. a gNB) of a wireless communications network and in which carrier wave emitters are controlled by the infrastructure equipment to transmit carrier wave signals and backscattered signals are detected;

[0018] Figures 2A and 2B schematically represent examples in which a reader in the form of a base station of a wireless communications network (Figure 2A) and a communications device (UE) of a wireless communications network (Figure 2B) transmit a reader to device (R2D) signal to a tag / A- loT device and receive a response signal as a backscattered signal according to example embodiments;

[0019] Figure 3 is a schematic block diagram illustrating an example wireless communications network configured in accordance with a 5G or new radio (NR) 3GPP standard according to example embodiments;

[0020] Figure 4 is a schematic block diagram illustrating in more detail a communications device (e.g. a UE) and an infrastructure equipment (e.g. a gNB) formed from components of the wireless communications network shown in Figure 2;

[0021] Figure 5 is a schematic block diagram illustrating an example of backscattering circuitry of an example tag / A-IoT device;

[0022] Figure 6 is a schematic illustration representing an example in which a carrier wave signal transmitted by an external carrier wave emitter is backscattered;

[0023] Figure 7 is an illustrative representation of a packet of an R2D signal comprising a plurality of OFDM symbols preceded by a preamble according to example embodiments:

[0024] Figure 8 is an illustrative representation of a method of generating a time-domain R2D signal superposed with an NR signal;

[0025] Figure 9 is an illustrative representation of an R2D signal designed with a tail portion and a cyclic prefix portion which copies the tail portion to improve synchronisation compared with an R2D signal without a tail-CP;

[0026] Figure 10 is a schematic block diagram illustrating a transmitter and receiver chain for transmitting and receiving an R2D signal for which simulation results provided in Figures 11 and 12 were generated;

[0027] Figure 11 is a graphical plot of simulation results of block or packet error rate (BLER) against signal to noise ratio (SNR) in dB for the transceiver chain shown in Figure 10 for a different number of blocks received;

[0028] Figure 12 is a graphical plot of simulation results of block or packet error rate (BLER) against signal to noise ratio (SNR) in dB for the transceiver chain shown in Figure 10 for a different ratio between a power of a tail-CP to a data part and different sampling frequency offset errors;

[0029] Figure 13 is a schematic representation of an R2D signal in which a different format of OOK modulation is used for a control information part with respect to a data bearing part of the R2D signal;

[0030] Figure 14 is a schematic representation of an R2D signal in which a different format of a density of timing signal parts is used for a control information part with respect to a data bearing part of the R2D signal;

[0031] Figure 15 is a schematic representation of an R2D signal in which a different format of encoding respective CP tail parts of the OFDM symbols is used for a control information part with respect to a data bearing part of the R2D signal; Figure 16 is a schematic representation of an R2D signal in which a different format of repeating OOK modulation parts of OFDM symbols representing data bits is repeated by different amounts for a control information part with respect to a data bearing part of the R2D signal; and

[0032] Figure 17 is a schematic representation of an R2D signal in which a different format of CP -tail power is used for the control information part with respect to the data bearing part of the R2D signal.

[0033] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Ambient loT

[0035] In release 19 of 3GPP (Rel-19), 3GPP will study Ambient loT [1] where a communications device (such as a user equipment (UE)) is essentially a zero power communications device. In Ambient loT, it is considered that the communications device can harvest energy to power its communication with a base station (such as a gNB). For example, the energy can be harvested from solar or kinetic energy such as vibrations. Alternatively, the energy to power the communications device can come from incident radio frequency (RF) energy, either directly from a base station or from a carrier wave emitter (CWE). An example in which such communication devices are powered by radio frequency energy derived from radio signals transmitted as a carrier wave (CW) by a CWE is shown in Figures 1 A and IB. Figures 1A and IB show a plurality of low- complexity communications devices 1, which can be deployed in accordance with an ambient loT scenario, which can be referred to as “tags” because of the simplicity of the devices. These tags 1 are powered as a result of radio frequency energy received from an incident CW 2 transmitted by the CWE 3. The tags 1 may also be referred to as ambient loT (A-IoT) devices.

[0036] In a first example illustrated by Figure 1A, a base station 4, or gNB 4 according to 3GPP 5G terminology, receives a backscattered signal 5 from the tags 1, the backscattered signal 5 being formed as a reflection of the carrier wave 2 transmitted by the CWE 3.

[0037] In a second example, a UE 7 receives a backscattered signal 5 from the tags 1. The UE 7 then transmits an indication of the received backscattered signals 5, which were received from the tags 1, to the gNB 4 via a wireless access interface 8 formed between the gNB 4 and the UE 7. Therefore, the gNB 4 may control the CWEs 3 to transmit the CWs 2, and the backscattered signals are detected by the detection station (UE) 7, and the detection station transmits an indication of the detected backscattered signals to the gNB 4.

[0038] The station which controls the CWEs 3 may be regarded as a controller station. The station which detects the backscattered signals 5 may be regarded as detection station. The detection station may also be referred to as reader. Therefore in the Figure 1 A both the controller station and the detection station are formed by a gNB 4 whereas in Figure IB the detection station 7 in the form of the UE is separate from the gNB 4 which acts as a controller station.

[0039] According to the arrangements of Figures 1A and IB, the tags 1 may modulate the reflected or backscattered signal 5 with information which is detected by the gNB 4 or a UE 7 acting as a detection station.

[0040] As shown in Figures 1 A and IB, the gNB 4, which provides a cell represented by dashed line 12 controls the CWE 3 to transmit the CW 2. In some examples, the CWE 3 is formed by a communications device (such as a UE) which operates with a wireless communications network of which the gNB 4 forms part. The gNB 4 has an interface 6 to the CWE 3. In some examples therefore the interface 6 may be a Uu interface using 3 GPP terminology. In some examples, the CWE is part of the gNB 4. In this case, the interface 6 can be an internal interface to the gNB 4.

[0041] The CWE 3 can be a standalone device or can be part of another network node. In one example, the CWE is a UE, such as a legacy UE or smartphone. In this case, the UE can be controlled to send a suitable signal to act as a carrier wave signal. It is also possible for the AIoT device to transmit data in the uplink by backscattering another signal (for example the DL signal from the gNB 4).

[0042] In some examples, such as the example of Figure IB, the backscattered signal 5 may be received by a separate detection station (e.g. UE 7) which does not form part of the gNB 4. However, since example embodiments can operate within or in association with wireless communications networks, an architecture of a typical 5G or New Radio (NR) wireless communications network will be now be described with reference to Figures 3 and 4.

[0043] In some examples, the CWE 3 may be incorporated within the detection station as a reader, in that the reader both emits the carrier wave signals and detects the backscattered signal from the one or more tags. The reader may then send the decoded information to the controller station.

[0044] Figures 2A and 2B provide alternative scenarios in which a reader of a tag / A-IoT device 1 transmits a reader to device (R2D) signal 21 to the tag / A-IoT device 1. In Figure 2A, the reader is a gNB 4 and in Figure 2B the reader is a UE 7. In some examples the reader may also receive a backscattered signal 5 reflected or backscattered by the tag / A-IoT device 1. Example embodiments described below relate to a design of the R2D signal 21. A problem addressed by the present technique concerns a need for the tags to synchronise with information transmitted in the R2D signal. The tags / A-IoT devices 1 may be of low complexity and have low accuracy clocks in order to reduce device complexity and to reduce power consumption. The tag is hence unable to accurately synchronise to the reader (e.g. gNB) and is unable to maintain accurate and consistent timing between synchronisation events (e.g. transmission of the Synchronization Signal Block (SSB)) as the tag’s clock would drift in the meantime. The low complexity of the tag / A-IoT device means that there may be limited processing capability for both cost and power consumption reasons and it is likely to be challenging to maintain an accurate clock frequency. The sampling frequency offset (SFO) can reach 104or 105parts per million (ppm) and can depend on device type. A type 1 device is a very low cost, low power and low complexity device and may use a ring oscillator with a frequency accuracy of 105parts per million (ppm). In contrast, a type 2a or 2b device can tolerate higher cost, higher power consumption and higher complexity. These type 2a or 2b devices may use an RC or crystal oscillator having a frequency accuracy of 103or 104parts per million (ppm). The frequency accuracy impacts the SFO directly. It is hence apparent that the initial SFO may relate to the device type. The SFO of a device can alternatively be determined by a reader from a measurement performed by the reader during a protocol exchange involving D2R signals that are sent by the tag / A-IoT device. In this case, the reader can measure the SFO on the D2R signals and determine that that SFO will also be applied by the tag / A-IoT device when the tag / A-IoT device decoding R2D signals. Atag / A-IoT device will have a small energy store; hence reception and transmission procedures can only consume small amounts of power. The device may hence not be capable of performing complicated signal processing algorithms.

[0045] 5G New Radio (NR) Wireless Communications System

[0046] As indicated above, example embodiments utilise and / or form part of components of the wireless communications network as illustrated in Figures 1A and IB and 2A and 2B. An example configuration of a wireless communications network which uses some of the terminology proposed for NR is shown in Figure 3. In Figure 3 a plurality of transmission and reception points (TRPs) 10 are connected to distributed control units (DUs) 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 dashed line 12. As such, wireless communications devices 7, 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 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 a core network 20 which may contain all other functions required for communicating data to and from the wireless communications devices and the core network 20. The core network 20 may be connected to other radio networks and infrastructure equipment.

[0047] The elements of the wireless access network shown in Figure 3 may operate in a similar way to corresponding elements of an LTE network. It will be appreciated that operational aspects of the telecommunications network represented in Figure 3 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.

[0048] The TRPs 10 of Figure 3 may in part have a corresponding functionality to a base station or eNodeB of an LTE network. It will be appreciated, therefore, that operational aspects of an NR 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 an NR network will be functionally similar to, respectively, the core network component, base stations and communications devices of an LTE wireless communications network. 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. As such, the terms infrastructure equipment, base station, transceiver stations, nodeBs, e-nodeBs, eNB, g-nodeBs, and gNB are used interchangeably in the present disclosure.

[0049] The term network infrastructure equipment / access node may be used to encompass the central unit 40 and associated DU 42 and TRP 10 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 CU 40, DUs 42 and / or TRPs 10. Communications devices 7 are represented in Figure 3 within the coverage area of respective communication cells 12. These communications devices 7 may thus exchange signalling with the CU 40 via the TRP 10 associated with their respective communications cells 12.

[0050] It will further be appreciated that Figure 3 represents merely one example of a proposed architecture for an NR-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.

[0051] A more detailed diagram of some of the components of the network shown in Figure 3 is provided by Figure 4. In Figure 4, a TRP 10 as shown in Figure 3 comprises, as a simplified representation, a wireless transmitter 30, a wireless receiver 32 and a controller or controlling processor 34 which is configured to control the transmitter 30 and the receiver 32 to transmit radio signals to and receive radio signals from one or more UEs 7 within a cell 12 formed by the TRP 10. As shown in Figure 4, an example UE 7 is shown to include a corresponding wireless transmitter 49, wireless receiver 48 and a controller or controlling processor 44 which is configured to control the transmitter 49 to transmit signals representing uplink data to the wireless communications network via the wireless access interface formed by the TRP 10 and the receiver 48 to receive downlink data as signals transmitted by the transmitter 30 in accordance with the conventional operation.

[0052] 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.

[0053] The interface 46 between the DU 42 and the CU 40 is known as the Fl 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, for example, may be formed from a fibre optic or other wired 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 TRP10 to the DU 42 and the Fl interface 46 from the DU 42 to the CU 40.

[0054] RF Incident Energy

[0055] As explained above with reference to the example shown in Figures 1 A, IB, 2A and 2B, Ambient loT proposes to use energy received from a radio frequency carrier wave in order to power devices. An Ambient loT device 1 could be powered by other ambient power sources, such as solar or thermal power. Harvesting energy based on the incident RF energy has several advantages and disadvantages.

[0056] An advantage is the RF energy is always available. Hence the Ambient loT device can always be awake while being powered from this energy. Furthermore a signal transmitted in the uplink from a tag can be backscattered using the incident radio frequency wave.

[0057] A disadvantage is the received power of the RF energy source is typically low. A receiver operating on such energy typically requires a power level of -30dBm to -20dBm for operation, which is not consistent with the low amounts of received power that are typically available directly from a base station. This required received power level sets a limit on the range (communication distance) supported by the AIoT system.

[0058] Another disadvantage is the transmission power level of a device that is powered by an RF energy source is typically very low. Such devices may operate based on backscattering technology, for example. The backscattered signal is created at the same carrier frequency as the incident RF energy. It is thus hard for the source of the RF energy (e.g. a gNB) to differentiate between the transmitted RF signal and the backscattered signal.

[0059] Another disadvantage is that, to reduce the power consumption of a receiver that operates on incident RF energy, a low power waveform / signaling scheme that is amenable to being decoded and received by a low power consumption receiver is typically required. For example, as explained below, an on-off keying (OOK) signaling scheme may be used for such lower power communications. There are then issues of multiplexing this new signaling scheme with the currently supported orthogonal frequency-division multiplexing (OFDM) and Discrete Fourier Transform-spread (DFT-s)-OFDM waveforms.

[0060] Despite the above listed disadvantages, it is considered that Ambient loT based on RF incident energy is feasible. Hence, 3 GPP have started a study item on Ambient loT technology [1] and collected some initial design targets, requirements, topologies, deployment scenarios, etc., in a technical report TR38.848 [3],

[0061] Backscattering Principle

[0062] As explained above with reference to Figures 1 A, IB, 2A and 2B, a passive device can transmit in the uplink (UL) using the backscattering principle. The UL signal can be backscattered on RF incident energy that can be either ambient (some RF energy that is already being transmitted in the ether, such as a cellular radio signal or a TV signal) or transmitted as a carrier-wave by a CW emitter for the express purpose of being backscattered. In either case, backscattering is performed based on the backscattering principle which is further described below. Different from the conventional wireless communications device which actively generates its own signal, backscattering devices rely on reflecting an incident signal to transmit data. The encoded data is modulated by varying the amplitude (ASK), phase (PSK), or frequency (FSK) of the backscattered signal. More specifically, backscattering modulation is achieved by alternating between distinct load impedances of the antenna, with each impedance state leading to a unique characteristic of the reflected signal [4], Figure 5 illustrates a generic form of the backscattering circuitry including a matching network and an integrated circuit (IC).

[0063] There are two aspects of power that are relevant to the Ambient loT device:

[0064] • Absorbed power. This is the power that is energy harvested and can be used to drive the circuits within the tag.

[0065] • Reflected power. This is the power that is reflected as a backscattered signal.

[0066] Given the antenna and load impedances denoted as Za= Ra+ jXaand Zn= Rn+ jXn, n = 1,2, respectively, the reflection coefficient corresponding to each state is expressed as where * denotes the complex conjugate operation. Note that Figure 5 shows the antenna impedance Zaas Zant. Note that it is possible for the load impedance to vary between more than two states, while in the present disclosure we consider binary state switching for the sake of simplicity. Ideally, when the load impedance is set to the complex conjugate of the antenna impedance at a certain state, n = 1, L = Z*, F] = 0 holds and thus the received power is completely absorbed by the communications device, leading to a lower reflection state. Different reflection coefficients can be obtained with different values of load impedance. For example, a value of Znthat is much greater than Zawill lead to a reflection coefficient close to 1, leading to a higher reflection state. Note that in practice, the reflection coefficient |Fn| depends on the manufacturing process and may vary within the range of (0,1).

[0067] The absorbed power can be calculated as where Pavaildenotes the power delivered from the antenna when the load impedance perfectly matches with the antenna impedance. In the literature the power transmission coefficient [5,6] is defined as:

[0068] In fact, the power captured by the antenna will be split into two; one part is scattered back to the reader while another part is delivered to the tag. For the design of the reflection ratio, a trade-off needs to be considered to balance the need for both parts of the power.

[0069] Given Pavaii, the average power absorbed by the device can be calculated as Where pn,n=i,2 denote the ratio of time duration for each impedance state; p = p2holds if the probability of each impedance equals to the other (this also means that the same probability of 0s and Is appears in the encoded data if the backscattered signal uses a pure OOK waveform).

[0070] CW Emitter

[0071] As explained above with reference to Figures 1A, IB, 2A and 2B, carrier-wave emitters (or CW emitter / CWE) can transmit a carrier wave signal (CWS) that can be used by the tag to backscatter a signal from. As explained above, the CWE may form part of a reader or detector and the CWS may be the R2D signal transmitted by the reader. The tag may additionally harvest energy from the CWS or simply use the power from the CWS to power the circuitry in the tag (i.e. energy may not be stored by the tag but may be used for ongoing operations). The scenario is shown in Figure 6. Figure 6 shows a tag 1 with a backscattering module 70. The backscattered signal is backscattered on the CW signal by the backscattering circuit, which may have the structure shown in Figure 5. The tag 1 includes an energy harvesting module 72, which converts energy of the carrier wave signal into power to drive a microcontroller 74 and the backscattering module 70. More explanation of the role and functionality of the CWE and CWS is described in European patent application 24192725.0, the contents of which are incorporated herein by reference.

[0072] Reader-to-Device (R2D) Signal

[0073] As discussed above, R2D signals may be transmitted from a reader to an A-IoT device. The reader that transmits the R2D signal may be a base station or may be a UE, as discussed in [3] and shown in Figures 2A and 2B, and as such both a base station and a UE that transmit an R2D signal may collectively be referred to as a reader or a transmitter. Although not shown in Figures 2A and 2B, the same R2D signal may be received by more than one A-IoT device.

[0074] It is expected that such R2D signals should be compatible with legacy OFDM-based systems in future deployments [8, 9], where these legacy OFDM-based systems are often referred to as cyclic prefix OFDM (CP-OFDM) systems. In particular, base stations or UEs according to existing 5G / NR wireless communications systems, such as those described above, are expected to transmit R2D signals in future 6G-I0T deployments. Accordingly, it is desirable that R2D signals can be generated using the same hardware as CP-OFDM systems. It is expected that the R2D signal is transmitted as one or more packets, which may be transmitted (e.g. by a base station) simultaneously with NR packets, and as such the actual transmitted signal may be a superposition of the R2D packets and the NR packets. A-IoT devices would then perform filtering in order to isolate the R2D signal from the superposed signal.

[0075] An example of an R2D packet 700 is shown in Figure 7, which includes a preamble 702 followed by M OFDM symbols 704, however other structures are envisaged. Figure 7 shows a close up view 706 of OFDM symbol M-l, showing a cyclic prefix (CP) 708 located at the start of the OFDM symbol, followed by a data portion 710 which includes tail portion 712. The tail portion 712 may alternatively be separate from the data portion 710. The CP 708 is a duplicate of the tail portion 712. This OFDM symbol structure shown in Figure 7 is the same as the OFDM symbol structure used in CP-OFDM systems. The CP in legacy NR / LTE systems allows for the use of low cost one tap channel equalization using fast Fourier transforms for decoding. The CP can also be used for subframe detection and timing correction. As mentioned above, R2D signals for A-IoT applications should coexist with legacy NR downlink systems, and as such the waveform type of the R2D signal should conform to the CP rule (i.e. the CP is a copy of a tail portion of the OFDM symbol).

[0076] However, due to the low-complexity nature of the A-IoT devices, the R2D signal carries information through amplitude variation in the time domain, e.g., OOK modulation. This differs from the conventional OFDM-based frequency-domain information carrying approach. Therefore, the R2D signal needs to be carefully designed such that the CP is properly included. However, the CP should be included in such a way that it does not interfere with the decoding of the R2D signal at the (low complexity) A-IoT device.

[0077] In addition, as A-IoT devices are of low complexity, it is challenging for these devices to maintain an accurate clock frequency. For example, the sampling frequency offset (SFO) can in some cases reach 104or 105ppm. While it is possible for devices to perform clock acquisition based on a preamble of the received signal (e.g. NR or R2D signal), the A-IoT device may not be able to maintain an accurate clock based only on this initial clock information. In particular, since the time duration of the clock acquisition part may be short, the accuracy of the A-IoT device’s derived clock may be poor. Support of continuous clock acquisition is one potential means of addressing this high SFO, however thus far the R2D signal does not support this functionality. It would therefore also be desirable to provide an R2D signal format that supports continuous clock acquisition such that the device can estimate and then correct the clock based on the reception of the R2D signal.

[0078] Our co-pending European patent application EP24192725.0 discloses a proposed structure for the R2D signal, the contents of which are incorporated by reference in their entirety. As disclosed in EP24192725.0, a reader device (i.e. a reader) transmits a reader-to-device (R2D) signal for receipt by a communications device, wherein the R2D signal spans one or more orthogonal frequencydivision multiplexing (OFDM) symbols of the radio access interface, wherein the R2D signal is transmitted according to an ON-OFF-keying (OOK) structure, and wherein the OOK structure for each of the one or more OFDM symbols comprises: a data portion comprising a first signal indicative of first data for receipt by the communications device; a tail portion located at an end of the OFDM symbol; and a cyclic prefix (CP) located at the start of the OFDM symbol, wherein the CP is a duplicate of the tail portion, and wherein the tail portion and the CP each comprise a second signal indicative of additional information for receipt by the communication’s device.

[0079] As disclosed in EP24192725.0, the R2D signals may be generated utilising an on-off-keying (OOK) scheme, commonly referred to as OOK-4, as shown in Figure 8. It should be appreciated that Figure 8 only represents one of the possibilities for signal generation and that the R2D signal may be generated using other OOK schemes. As illustrated in Figure 8, first the R2D signal 800 may be determined in the time domain to have a desired waveform 802. That time-domain R2D signal 800 is then converted into the frequency-domain via a fast Fourier transform (FFT) 804, producing a set of frequency domain sampled frequency components illustrated by a graphical plot 816. In some cases, the frequency-domain R2D signal may be rearranged 806 through subcarrier shifting and truncation, as shown by a graphical plot 818. The purpose of both operations is to preserve the OOK-like shape of the resulting time-domain R2D signal and ensure the retained subcarriers are within the corresponding subband assigned to the R2D link. An inverse FFT 810 may be performed to recover a time-domain R2D signal. The tail portion is then copied (i.e. duplicated) to the CP portion 812 to form the time-domain R2D and NR signal 814 that is represented by a discrete time plot 820.

[0080] According to our co-pending European patent application EP24192725.0, an OOK structure / scheme utilised for generation of the R2D signal contains two portions: a data-carrying portion, and CP -tail portions. Unlike the conventional usage of OOK-4 scheme where only the data-carrying portion is generated, the proposed R2D signal structure provides an efficient approach of CP handling through the introduction of the tail portion, i.e., the CP of each OOK symbol block is the duplicate of the tail portion. In particular, after a tail portion is determined the tail portion is copied to the CP portion. It should be noted that the CP and tail portions may in some cases be coded differently and may use a different waveform structure. Furthermore, as per above, the OOK symbol block is incorporated in the OFDM symbol block and is superposed with NR signals. Figure 9 provides a comparison between a CP handling for the proposed R2D signal and an original R2D signal. A top part of Figure 9 900 represents an example of the proposed R2D signal, in which a tail part 902 is copied to form the CP part 904, which has an effect of squeezing the data sequence 906 compared to an original data sequence 908 shown for an R2D signal 910 without the tail part 902 and including the CP part 904. The bottom left low-to-high dashed line is the CP-part of 910. Every OFDM signal needs to have this CP part. The squeezing of the data portion comes from the addition of the tail part 902 in 904. The overhead of the CP- part is common for both 900 and 910.

[0081] In utilising this approach, an A-IoT device may detect the CP portion of the R2D signal (i.e. the waveform). Furthermore, the R2D transmitter (i.e. the reader device, which may be a gNB or UE) may transmit an R2D signal with a CP. Accordingly, the R2D signal will be compatible with (and orthogonal to) other OFDM signals transmitted by the R2D transmitter. This approach also simplifies CP handling procedures compared to cases where the CP is inserted prior to performing an FFT. In addition, it is envisaged that the CP 902 and tail portions 904 may be utilised for one or more additional purpose, by indicating additional information for use by the A-IoT device, as will be discussed later. The R2D signal 900 can provide for either continuous clock acquisition by a tag / A-oT device or for data transmission to the device. Considering both the CP and the tail (i.e. the CP -tail), the device can either perform better clock acquisition or could support data transmission via the CP -tail pair.

[0082] Various further examples of signal designs for the R2D signal are provided in Figures 10 to 21 of EP24192725.0, with supporting explanation, which is incorporated by reference.

[0083] As a result of the good second-order cyclostationarity property of the CP-OFDM signal, a receiver can conduct a clock acquisition procedure in a continuous manner, e.g., a block-by-block or packet-by-packet manner. As for the R2D link, the clock frequency of tag / AIoT devices can be significantly drifted due to hardware limitations. Therefore, the CP and tail which are to be inserted into the R2D signal is desired to support the clock acquisition functionality of the devices. The R2D signal therefore has to 1) to co-exist well with the NR system and 2) to enable clock acquisition for the tag / AIoT device.

[0084] The tail part 902 or tail or tail pattern may be formed with an OOK data sequence. The tail pattern is designed to accommodate the needs of coexistence with NR systems and clock acquisition enabling. It is inserted for each OOK data sequence that spans a single OFDM symbol duration. Figure 9 illustrates the proposed signal structure in which a OOK data sequence spans a duration of a single OFDM symbol. To retain the same spectrum efficiency, the R2D signal retains a symbol duration as compared to the original OOK signal by squeezing the duration of the OOK data sequence (T^^ip > T’chipjd)-

[0085] With such an R2D signal structure, the following advantages may be achieved

[0086] 1) Straightforward CP insertion - the tail pattern duration can be designed to perfectly match with the CP duration; therefore, the CP insertion is realized in a straightforward way without introducing any confusing rising / falling edges. It is worth noting that the OOK data chip differs from the OOK chips incorporated by the tail pattern (e.g., in terms of chip duration, amplitude or phase).

[0087] 2) Compatibility with OOK-4 signal generation - given a particular bandwidth assigned to the R2D link, the designed signal can be generated by the OOK-4 scheme in a straightforward way.

[0088] 3) Support of continuous clock acquisition procedure - with tangible knowledge (e.g., the knowledge of tail pattern, reference sequence length, etc.), AIoT devices may conduct the clock acquisition procedure through cross- / auto-correlation calculation and adjust their local clock frequency accordingly.

[0089] It could be argued that squeezing the data sequence for tail pattern insertion may degrade the transmitted signal energy efficiency, because a certain amount of signal energy is assigned to the tail part 902. Although this may be true, characteristics of the tail part 902 may be optimised or at least improved to balance energy between the CP -tail portion and the data portion of the signal.

[0090] An example transceiver chain for transmitting and receiving the R2D signal disclosed in EP24192725.0 is illustrated in Figure 10. As shown in Figure 10, an information bitstream 1000 is received by a transmitter 1002 and first encoded with a Manchester encoding scheme 1004. Then, based on the system configurations (e.g., number of FFT grids, tail pattern), the data sequence length is adjusted and appended with a tail pattern 1006. The transmitter 1002 employs a OOK-4 scheme to generate the R2D signal using a particular assigned bandwidth, by applying an FFT 1008, performing signal modification 1010 as explained above with reference to Figure 8 as rearranging, and then transforms the frequency domain signal into the time domain using an IFFT 1012. Depending on the size of assigned bandwidth, an accuracy of OOK-4 enabled signal approximation may differ. With CP inserted 1014, the R2D signal is transmitted through the mobile fading channel 1016.

[0091] At the receiver side, a receiver 1018 receives an analogue signal, which is filtered with band pass filter 1020, rectified, with an envelope detector 1022 and then quantized into a digital signal with an analogue to digital converter 1024 (assuming RF-ED receiver architecture). Based on the received signal which offers good a cyclostationarity property in terms of the amplitude (incorporating both CP and tail pattern), the receiver 1018 is able to determine the location of CP and tail patterns. This could be done by calculating the cross-correlation between the received signal and a known pattern or alternatively, autocorrelation calculations. Based on the calculation, the receiver estimates the SFO 1026 by comparing the determined index of both CPs and tails with their reference locations which is indicated to the receiver. After the SFO estimation 1026, the receiver may correct its local clock frequency 1028 accordingly and decode the received data 1030, and output detected bits 1032.

[0092] Clock Acquisition Performance of Proposed R2D Signal

[0093] While the signal structure of the scheme proposed and disclosed in EP24192725.0 allows a tag / A- loT device to perform clock acquisition, it has been observed that the accuracy of the clock acquisition improves with time. When the clock acquisition process spans a longer time period, a receiver is able to apply more averaging and hence estimate a less noisy timing estimate for decoding.

[0094] Figure 11 presents a graphical plot of block error rate (BLER) which is equivalent to a packet error rate since the R2D signal is transmitted as packets, with respect to signal-to-noise ratio. Figure 11 shows the performance of the R2D scheme disclosed in EP24192725.0 as a function of a number of blocks transmitted. The performance was obtained as a simulation based on the transceiver chain shown in Figure 10. The simulation results were obtained for a setup which considered a case where five consecutive blocks of data were transmitted using the R2D signal of EP24192725.0. The clock acquisition function worked consecutively over the set of blocks. The clock acquisition and SFO of the device were reset after this clock acquisition. It is clear that the BLER performance improves with time (block 2 has a more averaged clock than block 1 since the averaging function has been carried over from block 1). The received signal reliability improves with time as the clock acquisition improves.

[0095] Figure 12 presents a graphical plot for a simulated performance of the R2D scheme disclosed in EP24192725.0 as a function of the device SFO and the amplitude of the CP -tail relative to the amplitude of the data portion of the signal. Figure 12 shows that:

[0096] When SFO = 0, a relative amplitude of 1 is optimal. With low SFO, the device is not limited by clock acquisition and hence it is preferable to concentrate signal energy in the data portion of the signal.

[0097] When SFO is high, a relative amplitude of 2 is preferable. With a high SFO, the device performance is limited by its clock acquisition ability. Hence, it is preferable to concentrate energy in the CP -tail portion of the signal.

[0098] With the simulation results illustrated in Figures 11 and 12, embodiments of the present technique seek to provide improvements in respect of the design of the R2D scheme disclosed in EP24192725.0. This is because an A-IoT system needs to be designed to account for the conclusions from the simulation results presented in Figures 11 and 12 that show that:

[0099] The decoding reliability improves with time.

[0100] The optimal parameter choice for the R2D signal depends on device characteristics (such as SFO) and operating conditions (such as SNR)

[0101] R2D Signal Design with Control Information In embodiments according to example embodiments there is provided a communications apparatus acting as a reader for a tag / A-IoT device. The communications apparatus operating as a reader device forms part of a wireless communications network and is configured to transmit signals to and / or to receive signals from one or more other tag / A-IoT devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A- loT devices. The communications apparatus includes transceiver circuitry configured to transmit a reader-to-device (R2D) signal for receipt by a tag / A-IoT device. The R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

[0102] According to example embodiments, control information is transmitted using a default format. Payload data may be sent using a format that is defined by a control information part of the R2D signal.

[0103] A: Control information transmitted with a more robust format

[0104] According to example embodiments, the communications apparatus transmits control information with the R2D packet by applying techniques to provide a more robust communication than the data part. According to example embodiments a first portion of a packet may have lower reliability than the following part of the packet. This issue occurs because of the high initial sampling frequency offset assumed at the device and the fact that the clock acquisition improves throughout the decoding of the packet. It is hence desirable that the initial portion of the packet is more robust than the rest of the packet.

[0105] A.l Control information transmitted with a modulation more tolerant to clock error

[0106] According to some example embodiments, the control information is transmitted with a modulation that is more tolerant to clock error than a main data part of the R2D signal.

[0107] According to one example, the control portion of the R2D signal or packet is transmitted with a different modulation such as an OOK-1 waveform and the data part is transmitted with an OOK- 4 waveform. The chip duration of an OOK-1 waveform is longer than that of an OOK-4 waveform and is hence more tolerant of timing error.

[0108] An R2D signal that is formed according to example embodiments is illustrated in Figure 13. The Figure 13 shows an R2D signal forming a packet 1300 for transmission to a tag / A-IoT device, comprising a preamble or clock acquisition section 1302, followed by a control information part 1304 after which is transmitted a data carrying part 1306. According to example embodiments, the control information part 1302 is transmitted with a more robust modulation (OOK-1) than the data part 1306 (OOK-4). Figure 13 also shows the whole signal 1300 being preceded by the preamble / clock acquisition part (CAP) 1302. The purpose of this preamble / CAP 1302 is to achieve some rudimentary clock calibration prior to the control information 1304. The clock will be further refined within the control information 1304 and data parts 1306 of the R2D signal. As will be appreciated, whenever a modulation of control information is more robust than a modulation of the data part, any combination of modulations can be applied. For example, the OOK-1 (or OOK-2) can be used for the control portion, while OOK-2 (or OOK-4) can be used for the data part.

[0109] A.2 Control information transmitted with its own inherent timing reference

[0110] According to some example embodiments, a data in the control information may be surrounded by timing pulses at the start and end (like the CP -tail signal, as discussed with reference to Fig. 9). The timing pulses allow the control information to be decoded in a one-shot process (e.g. by interpolating between the timing pulses) whereas the subsequent data can be decoded based on longer term timing acquisition. A longer term timing acquisition process has less jitter than the one-shot timing acquisition process and this leads to more robust decoding. An example is illustrated in Figure 14. Figure 14 shows that the R2D signal structure 1300 contains more timing information in the control information portion 1304 of the signal than the data part 1306 of the signal. Figure 14 shows within first and second bubbles surrounded by dashed lines 1400, 1402, a structure of respectively the control information part and the data part of a packet of the R2D signal. As shown in the control information carrying part 1400, the modulated OFDM symbols comprise four timing parts 1404 and two information carrying parts 1406 within the timespan of the first dashed-line bubble. Within the timespan of the second dashed line bubble 1402, the data bearing section of the R2D packet which is modulated with OOK-4 comprises a first timing part 1404 at the start and a second timing part at the end between which there is a data bearing part modulated with OOK-4 carrying data 1410. As can be seen in Figure 14, according to this example embodiment, a ratio of timing parts to data carrying parts is significantly lower in the data bearing part of the R2D packet 1402. Figure 14 shows that the number of timing pulses within a time window 1400 for the control information part is greater than the number of timing pulses within a time window 1402 for the data bearing part. Hence the density of timing pulses is greater in the control information part than in the data bearing part.

[0111] A.2.1 CP-tail of control information used for timing, CP-tail of rest of packet used for data

[0112] As taught by EP24192725.0, the CP -tail portion of the OFDM-generated OOK signal can either be used to support clock acquisition or can be used for the transmission of data. Since the device has poor clock calibration at the start of the packet, it is beneficial to use different CP -tail types in the control information part of the main data part of the packet:

[0113] CP -tail is used for clock acquisition at the start of the packet

[0114] CP -tail is used for data transmission in the main data part of the packet

[0115] Figure 15 illustrates an example embodiment, in which a CP -tail in a control information part 1304 is used for clock acquisition and a CP -tail in the data transmission part 1306 is used for data transmission of an R2D packet 1300. As shown in Figure 15, an OFDM symbol 1500 of the control information part 1304, includes a tail portion 1504 which is copied to a CP portion 1506 is a front of the OFDM symbol 1500, which carries control information in a main section 1508. For the data bearing part of the R2D packet 1510, two OFDM symbols 1512, 1514 each include a tail portion 1516, 1518 and a CP portion 1520, 1522, which copies the respective tail portions 1516, 1518. Between the tail portions 1516, 1518, and the CP portions 1520, 1522 there is a data-carrying portion 1524, 1526, which is modulated to represent the data being transmitted in the data part 1306. However, for the second OFDM symbol 1514, the tail portion 1518 and the CP portion 1522 are modulated differently from the tail portion 1516 and the CP portion 1520 of the first OFDM symbol 1512. This is because, in the control information part, the CP -tail is used for clock acquisition, as explained in EP24192725.0, whereas for the data part, the CP -tail 1506, 1508, is a function of the data transmitted. These CP -tail types are discussed in more detail in EP24192725.0.

[0116] A.2.1.1 CP-tail type of main data part depends on channel conditions

[0117] According to another example embodiment, the CP -tail of the main data carrying part is used for data transmission in accordance with the channel conditions. For example, the CP -tail of the main data carrying part is only used for data transmission when the channel conditions are good. Hence, based on knowledge of the channel conditions, the control information portion of the R2D packet signals the CP -tail type of the main data part of the packet:

[0118] In good channel conditions, the control information can signal that the CP -tail of the main data part of the packet transmits data

[0119] In poor channel conditions, the control information can signal that the CP -tail of the main data part of the packet contains a signal type that is suitable for clock acquisition

[0120] A.2.1.2 CP-tail type of main data part depends on SFO

[0121] According to this embodiment, the CP -tail of the main data carrying part is used for data transmission in accordance with SFO conditions at the device, or as a combination of the channel conditions and the SFO conditions at the device. When the SFO at the device is low, the CP -tail of the main data part of the packet transmits data, otherwise the CP -tail portion is used for clock acquisition.

[0122] Since different device type of the tag / A-IoT device (e.g. 1, 2a, 2b, etc.) may have different initial SFO assumptions / requirements, the SFO at the device may depend on the device type. The information of the device type of the device is sent to the network. Therefore, the network can control the CP -tail transmission depending on the SFO condition implicitly with reference to the device type.

[0123] A.3 Repetition coding applied to control information part of the packet

[0124] According to some example embodiments, the chips / bits of the control information part of the packet are repetition coded. This improves the reliability of this portion of the packet. The repetition coding pattern also helps from the perspective of clock acquisition, since the repeated chips naturally contain a timing reference (the chip transitions in adjacent symbols are in the same location, allowing the time between those transitions to be measured for clock acquisition purposes). An example of this embodiment is shown in Figure 16 in which an R2D packet 1300 comprises a preamble 1302, control information part 1304 and the data bearing part 1306.

[0125] Figure 16 shows within first and second bubbles surrounded by dashed lines 1610, 1612, a structure of respectively the control information part 1304 and the data part 1306 of a packet of the R2D signal 1300. As shown in the control information carrying part 1610, the OOK-1 modulated OFDM symbols comprise two or more OFDM symbols, modulated with OOK-1, in first and second sections 1614, 1616, which are bounded by vertical dashed lines. Each section 1614, 1616, respectively carries a single bit, which are different bits, bitl and bit2, between each of the sections 1614, 1616. Within the second dashed line bubble 1612, the data bearing section of the R2D packet which is modulated with OOK-4 also comprises first and second sections 1620, 1622, which are bounded by vertical dashed lines. The CP -tail is not shown in Figure 16 for simplicity. Each section 1620, 1622, respectively carries two bits, bitl, bit2 and bit3, bit4, which are different in each section.

[0126] According to this example embodiment, the number of OFDM symbols forming each of the sections of the control information part 1614, 1616 and the data part 1620 1622 between the dashed vertical lines carries the same number of OOK chips formed from OFDM symbols. The number of OFDM symbols shown for the control information part 1614, 1616, and the data part 1620, 1622 is different, since in the first bubble 1610 the modulation is OOK-1 and in the second bubble 1612 the modulation is OOK-4, where OOK-4 can carry more chips per OFDM symbol than OOK-1. Each section 1614, 1616 in the control information part 1604 carries half the number of bits than the respective sections 1620, 1622 of the data carrying part 1606 of the R2D packet 1600.

[0127] A.4 CP-tail of control information is transmitted at a higher power level

[0128] As explained in EP24192725.0, the CP -tail portion of the OFDM symbols used to transmit the control information can be transmitted at a higher power than the data portions of the OFDM symbols. A high CP -tail power improves the clock acquisition performance of the tag / A-IoT device’s receiver. Since the clock acquisition performance is worse at the start of the packet, it is desirable to improve this performance through transmitting the CP -tail at a higher power. An example according to these embodiments is represented in Figure 17. Figure 17 shows within first and second bubbles surrounded by dashed lines 1700, 1702, a structure of respectively the control information part 1304 and the data part 1306 of a packet of the R2D signal 1300. As shown in the control information carrying part 1304, an OOK-4 modulated OFDM symbol is shown with vertical dashed lines, which comprises a data bearing section 1704 followed by a tail part 1706 with a CP part 1708 preceding the data section 1704 which copies the tail section 1706. Correspondingly, in the second dashed bubble 1702 illustrating a format of the data part 1306, Figure 17 shows the same format as the first dashed bubble 1700 of the control information part 1304. That is to say, a data bearing portion 1720 of an OOK-4 modulated symbols includes a data bearing part 1720, followed by a tail part 1722 and preceded by a CP part 1724, which copies the tail part 1722. As illustrated by this example embodiment, for the OFDM symbol 1700 transmitted as part of the control information part 1304, a power or amplitude of the CP part and tail part 1706, 1708 is larger than the data bearing part 1704. This differs with the OFDM symbol transmitted in the data carrying part 1306 in which an amplitude / power of transmission of the data part 1720 and the CP and tail parts 1722, 1724 is substantially the same. According to this example therefore the control information section 1304 can be used by a tag / a loT device to acquire more easily synchronisation and reduce SFO because the tail part 1706 and CP part 1708 portions are transmitted with a higher amplitude.

[0129] A.5 Control information is transmitted with a default format In some example embodiments, a different OOK-4 modulation scheme may be used for the CP- tail 1708, 1706, depending upon prevailing channel conditions or depending on a sampling offset error of the tag / A-IoT device (SFO). For example, an optimum power setting for the CP -tail portion relative to the data portion of an OFDM symbol may depend on SFO. If the SFO is low, the CP -tail portion is preferably transmitted at a lower power as the CP -tail portion does not add considerably to the clock acquisition accuracy in this case and it is better that the energy is concentrated in the data portion of the signal. Alternatively, when the SFO is high, the packet is limited by the clock acquisition capability from the CP -tail portion and it is preferable for more power to be applied to this portion of the signal in order to improve the clock calibration performance of the system.

[0130] Hence, in such embodiments, the control information 1304 is sent using a default format (e.g. a default power of the CP -tail relative to the data portion) and the data portion 1306 of the packet 1300 is sent in a format that is signalled by the control information 1304. The default format may be transmitted robustly such that it does not limit system performance. Examples of robust transmission are provided in above example embodiments (A.l to A.4).

[0131] As also described in above example embodiments (such as A.2.1.2), the SFO can be known by the network through the information of device type of the device.

[0132] Embodiment B: First packet of a sequence of packets is enhanced for clock acquisition

[0133] B.l Repetition of first packet in a sequence of packets

[0134] The above-described embodiments identified as Al to A5 concern a format and structure of an R2D signal representing a packet so that both control information and data can be communicated to a tag / A-IoT device in the presence of SFO. The following examples concern a transmission of an R2D signal comprising a plurality of packets. According to a 1stexample embodiment, a first packet of a sequence of packets is repeated. In some examples, fewer repetitions are used for later packets of a sequence of packets.

[0135] A reliability of a first packet in a sequence of packets is likely to be lower than a reliability of subsequent packets due to clock unreliability and greater SFO. Once a first packet is received, the tag / A-IoT device will have calibrated its clock and will be able to decode further packets more reliably.

[0136] Hence, in accordance with some embodiments, a first packet of a sequence of packets of the R2D signal is repeated. If the first packet is not received correctly, the second packet is still likely to be received correctly. Duplicate packets can be discarded by the tag / A-IoT device based on a sequence numbering scheme, that is to say that each packet includes a field identifying its number order in the sequence of packets so that once the packet has been detected other packets can be discarded.

[0137] If a first packet of a set of received packets is received correctly, the device can sleep for further repetitions of that packet, maintaining its clock calibration. This will save power at the tag / A-IoT device, for example the tag / A-IoT device can save the limited energy that it has managed to harvest by an energy harvesting mechanism. For this functionality to be viable, the tag / A-IoT device would have to know when the repetitions of the packet are transmitted, such that it wakes up following those repetitions and before the start of new packets. Alternatively, the tag / A-IoT device could use the repetitions of the packet for energy harvesting purposes.

[0138] B.2 First packet has a longer clock acquisition part

[0139] According to some example embodiments, a first packet of a sequence of packets has a longer clock acquisition part (preamble) 1302. This allows the tag / A-IoT device’s clock to be calibrated using the long clock acquisition signal. The calibrated clock can then be used for decoding subsequent packets.

[0140] In this embodiment, a clock acquisition part 1302 can be terminated by a start delimiter. The device can then calibrate its clock until the start delimiter is observed. In previously proposed arrangements, a clock acquisition part 1302 is a fixed length and a start of a packet is determined by counting the elements of the clock acquisition part 1302, for example if the clock acquisition part consists of sixteen transitions, the start of the packet is determined by counting those sixteen transitions.

[0141] Embodiment C: Information in control packet that needs to be transmitted robustly

[0142] Example embodiments can also relate to information transmitted in the control information part 1304. This section lists items in the control information that need to be transmitted robustly.

[0143] C.l Length of Packet

[0144] If a tag / A-IoT device is not able to detect a length of a packet of an R2D signal, for example because the length of the packet is not signalled robustly, the tag / A-IoT device would not be able to detect an end of the packet. This could lead to false decoding of the packet. The tag / A-IoT device is not able to receive other signals while it is attempting to decode a packet. Hence, if the tag / A-IoT device misinterprets a length as being longer than it actually is, the tag / A-IoT device will be unable to decode other packets while committing its processing circuitry to decode a portion of a packet that does not actually exist.

[0145] C.l Identity of the Device in a R2D Packet

[0146] Example embodiments can also provide an arrangement in which a device can identify a packet based on information provided within the packet such as within the control information part. If the tag / A-IoT device decodes a packet for a different device (i.e. it misreads the identity), it will waste energy on trying to decode that packet.

[0147] Accordingly, by providing information within the control information, which identifies a device for which the packet is being transmitted, the device may quickly identify that the packet is or is not to be received by this device.

[0148] In some example embodiments, the tag / A-IoT the device can send a NACK to the reader if an R2D packet is not successfully decoded by the device. The device can only send this NACK if it identifies that a packet is assigned for it.

[0149] According to some examples, an identity of the device is transmitted in a portion of the packet, which will increase the likelihood of the device being able to decode this identity. If the rest of the packet cannot be correctly decoded, the device can then send a NACK to the reader and a retransmission can be sent.

[0150] C.3 Chip length

[0151] According to some embodiments, a chip length of Manchester encoded data in a data part 1306 may be different to a chip length of a control information part. For example, the chip length of the data part might be shorter than the chip length of the control information, allowing for a higher data rate for the data part. The control information can hence signal the chip length of the data part.

[0152] Those skilled in the art would further appreciate that methods, 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, provided that these are within the scope of the claims.

[0153] The methods described herein may also be embodied or encoded in a computer-readable medium, such as a computer-readable storage medium, containing instructions. Instructions embedded or encoded in a computer-readable medium may cause a programmable processor, or other processor, to perform the method, e.g., when the instructions are executed. Computer-readable media may include non-transitory computer-readable storage media and transient communication media. Computer readable storage media, which is tangible and non-transitory, may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a CD-ROM, a floppy disk, a cassette, magnetic media, optical media, or other computer-readable storage media. The term “computer- readable storage media” refers to physical storage media, and not signals, carrier waves, or other transient media. As noted above, computer readable media may include transient communication media. Such communication media may occur within a single computer system or between multiple computer systems, and may take the form of transient signal-conveying media such as carrier waves and transmission signals.

[0154] Therefore, from one perspective there has been described methods, reader devices, communications devices, and circuitry for providing a R2D signal that is compatible with legacy OFDM-based systems.

[0155] Particular examples of the present disclosure are set out in the following numbered paragraphs:

[0156] Paragraph 1. A method of operating a reader device forming part of a wireless communications network and configured to transmit signals to and / or to receive signals from one or more other tag / Ambient loT (A-IoT) devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices, the method comprising: transmitting a reader-to-device (R2D) signal for receipt by a tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF- keying (OOK) modulation, wherein the packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

[0157] Paragraph 2. A method of paragraph 1, comprising modulating the one or more OFDM symbols of the data bearing part according to a first OOK modulation scheme, and modulating the one or more OFDM symbols of the control information part according to a second OOK modulation scheme, the format of the control information part being different to the format of the data bearing part as a result of the second OOK modulation scheme being different to the first OOK modulation scheme.

[0158] Paragraph 3. A method of paragraph 2, wherein the second OOK modulation scheme is more tolerant to clock errors than the first OOK modulation scheme.

[0159] Paragraph 4. A method of paragraph 2 or 3, wherein the second OOK modulation scheme is an OOK-1 scheme and the first OOK modulation scheme is an OOK-4 scheme.

[0160] Paragraph 5. A method of any of paragraphs 1 to 4, comprising forming the control information part with a plurality of timing pulses, each of the one or more OOK modulated OFDM symbols carrying the control information and includes one or more of the timing pulses, and forming the data bearing part with a plurality of timing pulses, each of one or more OOK modulated OFDM symbols carrying data and includes one or more of the timing pulses, wherein a density of timing pulses in respect of a number of the timing pulses within a time window is greater in the control information part than the data bearing part.

[0161] Paragraph 6. A method of paragraph 5, wherein the timing pulses comprise OOK signals with a chip duration which is less than a chip rate of the one or more OOK modulated OFDM symbols.

[0162] Paragraph 7. A method of any of paragraphs 1 to 4, comprising forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part to carry data and not modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part. Paragraph 8. A method of any of paragraphs 1 to 4, comprising forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, determining channel conditions for communicating the R2D signal, and depending on the channel conditions either modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part with a known pattern, or modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part with a pattern that is function of transmitted data, and modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part with a known pattern.

[0163] Paragraph 9. A method of any of paragraphs 1 to 4, comprising forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and depending on a device type, either modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part to carry data with a known pattern, or modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part with a pattern that is function of transmitted data, and modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part with a known pattern.

[0164] Paragraph 10. A method of any of paragraphs 1 to 4, comprising forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, wherein the transmitting the R2D signal comprises transmitting the tail portion and the CP portion of each of the OOK modulated OFDM symbols carrying the control information with a power which is greater than a portion modulated with the control information, and greater than a power with which the tail portion and the CP portion of the OOK modulated OFDM symbols of the data bearing part carrying the data is transmitted.

[0165] Paragraph 11. A method of paragraph 9, wherein the power with which the tail portion and the CP portion of each of the OOK modulated OFDM symbols carrying the control information with respect to the power with which the portion modulated with the data is based on the device type.

[0166] Paragraph 12. A method of paragraph 9 or 11, comprising determining channel conditions for communicating the R2D signals, wherein the power with which the tail portion and the CP portion of each of the OOK modulated OFDM symbols carrying the control information with respect to the power with which the portion modulated with the data is based on the determined channel conditions.

[0167] Paragraph 13. A method of any of paragraphs 1 to 4, comprising forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of one or more parts of each of the OFDM symbols being modulated with a data bit of the control information, and forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of one or more parts of the OFDM symbol being modulated with a bit of the data, wherein each of the one or more parts of the OFDM symbols are repeated one or more times to represent each of the data bits of the control information, the format of the data bearing part being different to the format of the control information as a result of the repetition of the one or more parts of the OFDM symbols to represent the one or more data bits of the control information.

[0168] Paragraph 14. A method of paragraph 13, wherein each of the one or more parts of the OFDM symbols are repeated one or more times to represent each of the data bits carried by the data bearing part, and a number of repetitions of the one or more parts of the OFDM symbols to represent a bit of the control information is greater than a number of repetitions of the one or more parts of the OFDM symbols to represent a data bit of the data bearing part.

[0169] Paragraph 15. A method of any of paragraphs 5 to 9, wherein the forming the control information part includes forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of one or more parts of each of the OFDM symbols being modulated with a data bit of the control information, and the forming the data bearing part includes forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of one or more parts of the OFDM symbol being modulated with a bit of the data, wherein the each of the one or more parts of the OFDM symbols is repeated one or more times to represent the data bits of the control information, the format of the data bearing part being different to the format of the control information as a result of the repetition of the one or more parts of the OFDM symbols to represent the one or more data bits of the control information.

[0170] Paragraph 16. A method of any of paragraphs 1 to 15, comprising forming the R2D signal from a plurality of the one or more packets, and repeating a first of the plurality of packets one or more times.

[0171] Paragraph 17. A method of paragraph 16, comprising adding a sequence number to each of the plurality of packets which uniquely identifies that packet.

[0172] Paragraph 18. A method of any of paragraphs 1 to 15, comprising forming the R2D signal from a plurality of the one or more packets, and forming each packet with a preamble followed by the control information part, followed by the data bearing part.

[0173] Paragraph 19. A method of paragraph 18, wherein the preamble of a first of the packets is longer than the preamble of subsequent packets.

[0174] Paragraph 20. A method of paragraph 18, forming the preamble of the first packet with a start delimiter.

[0175] Paragraph 21. A method of any of paragraphs 1 to 20, wherein the control information includes an indication of a length of the packet.

[0176] Paragraph 22. A method of any of paragraphs 1 to 21, wherein the control information includes an indication of a tag / A-IoT device to which the R2D signal is transmitted.

[0177] Paragraph 23. A method of any of paragraphs 1 to 22, wherein the control information includes an indication of a chip length of the OOK modulation representing the data carried by the data bearing portion.

[0178] Paragraph 24. A communications apparatus operating as a reader device forming part of a wireless communications network, the communications apparatus comprising transceiver circuitry configured to transmit signals to and / or to receive signals from one or more other tag / A-IoT devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices, and controller circuitry configured to control the transceiver circuitry to transmit a reader-to- device (R2D) signal for receipt by a tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

[0179] Paragraph 25. A method performed by a tag / A-IoT device, the method comprising receiving a reader-to-device (R2D) signal from a communications apparatus acting as a reader device, the communications apparatus operating with a wireless communications network and the R2D signal being transmitted via a radio access interface of the wireless communications network between the reader device and the tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

[0180] Paragraph 26. A method of paragraph 25, wherein the one or more OFDM symbols of the data bearing part have been modulated according to a first OOK modulation scheme, and the one or more OFDM symbols of the control information part have been modulated according to a second OOK modulation scheme, the format of the control information part being different to the format of the data bearing part as a result of the second OOK modulation scheme being different to the first OOK modulation scheme.

[0181] Paragraph 27. A method of paragraph 26, wherein the second OOK modulation scheme is more tolerant to clock errors than the first OOK modulation scheme.

[0182] Paragraph 28. A method of paragraph 26 or 27, wherein the second OOK modulation scheme is an OOK-1 scheme and the first OOK modulation scheme is an OOK-4.

[0183] Paragraph 29. A method of any of paragraphs 25 to 28, wherein the control information part includes a plurality of timing pulses, each of one or more OOK modulated OFDM symbols carrying the control information and includes one or more timing pulses, and the data bearing part includes a plurality of timing pulses, each of one or more OOK modulated OFDM symbols carrying data including one or more timing pulses, wherein a density of timing pulses, in respect of a number of timing pulses within a time window is greater in the control information part than the data bearing part, and the method includes using the timing pulses to acquire a clock synchronisation for detecting the control information and the data from the OOK modulated OFDM symbols.

[0184] Paragraph 30. A method of paragraph 29, wherein the timing pulses comprises OOK signals with a chip duration which is less than a chip rate of the one or more OOK modulated OFDM symbols. Paragraph 31. A method of any of paragraphs 25 to 28, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part includes one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated to carry data and the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part have not been modulated, and the method comprises using the tail portion and the CP of the control information part to acquire a clock synchronisation for detecting the control information and the data from the OOK modulated OFDM symbols.

[0185] Paragraph 32. A method of any of paragraphs 25 to 28, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part including one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and depending on the channel conditions either the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have not been modulated to carry data, or the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated to carry data, and the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part have been modulated to carry data, and the method comprises using the tail portion and the CP of the control information part and the data part to synchronise a clock of the tag / A-IoT device.

[0186] Paragraph 33. A method of any of paragraphs 25 to 28, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part including one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part have been modulated with a known pattern and depending on the channel conditions either the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated with a known pattern, or the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated with a pattern that is a function of transmitted data.

[0187] Paragraph 34. A method of any of paragraphs 25 to 28, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part including one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, comprising determining a sampling frequency offset (SFO) of the tag / A-IoT device caused by an error in a clock of the tag / A-IoT device and a clock used to form the R2D signal, transmitting an indication of the SFO to the reader, and depending on the SFO either the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have not been modulated to carry data, or the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated to carry data, and the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part have been modulated to carry data, and the method comprises using the tail portion and the CP of the control information part and the data part to synchronise a clock of the tag / A-IoT device.

[0188] Paragraph 35. A method of any of paragraphs 25 to 28, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part including one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, comprising determining a device type of the tag / A-IoT device, transmitting an indication of the device type to the reader, and depending on the device type either the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated with a known pattern, or the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated with a pattern that is a function of transmitted data, and the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part have been modulated with a known pattern.

[0189] Paragraph 36. A method of any of paragraphs 25 to 28, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part includes one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and the tail portion and the CP portion of each of the OOK modulated OFDM symbols carrying the control information have been transmitted with a power which is greater than a portion modulated with the control information, and greater than a power with which the tail portion and the CP portion of the OOK modulated OFDM symbols of the data bearing part carrying the data.

[0190] Paragraph 37. A method of paragraph 36, comprising transmitting an indication of the device type, and receiving the R2D signal, wherein a power with which the tail portion and the CP portion of each of the OOK modulated OFDM symbols carrying the control information with respect to the power with which the portion modulated with the data is based on the device type.

[0191] Paragraph 38. A method of any of paragraphs 25 to 28, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of one or more parts of each of the OFDM symbols having been modulated with a data bit of the control information, and the data bearing part includes one or more OOK modulated OFDM symbols carrying data, each of one or more parts of the OFDM symbol having been modulated with a bit of the data, wherein each of the one or more parts of the OFDM symbols are repeated one or more times to represent each of the data bits of the control information, the format of the data bearing part being different to the format of the control information as a result of the repetition of the one or more parts of the OFDM symbols to represent the one or more data bits of the control information.

[0192] Paragraph 39. A method of paragraph 38, wherein each of the one or more parts of the OFDM symbols are repeated one or more times to represent each of the data bits carried by the data bearing part, and a number of repetitions of the one or more parts of the OFDM symbols to represent a bit of the control information is greater than a number of repetitions of the one or more parts of the OFDM symbols to represent a data bit of the data bearing part.

[0193] Paragraph 40. A method of any of paragraphs 25 to 39, wherein the R2D signal includes a plurality of the one or more packets, a first of the plurality of packets is repeated one or more times, and each of the plurality of packets includes a sequence number which uniquely identifies the packet, and the method comprises detecting the first packet from the plurality of repetitions of the first packet in the R2D signal, and once the sequence number has been detected not decoding repeated packets having the same sequence number after detecting the sequence number of the first packet.

[0194] Paragraph 41. A method of any of paragraphs 25 to 40, wherein the R2D signal includes a plurality of the one or more packets, each packet including a preamble followed by the control information part, followed by the data bearing part, and the preamble of a first of the packets is longer than the preamble of subsequent packets, and the method comprises using the preamble of the first packet to acquire a clock synchronisation for detecting the control information and the data from the OOK modulated OFDM symbols from the R2D signal.

[0195] Paragraph 42. A method of paragraph 41, wherein the preamble of the first packet includes a start delimiter, and the method comprises using the preamble of the first packet to acquire a clock synchronisation until the delimiter is detected.

[0196] Paragraph 43. A method of any of paragraphs 25 to 42, wherein the control information includes an indication of a length of the packet.

[0197] Paragraph 44. A method of any of paragraphs 25 to 43, wherein the control information includes an indication of a tag / A-IoT device to which the R2D signal is transmitted.

[0198] Paragraph 45. A method of any of paragraphs 25 to 44, wherein the control information includes an indication of a chip length of the OOK modulation representing the data carried by the data bearing portion.

[0199] Paragraph 46. A method of any of paragraphs 25 to 45, comprising sending a NACK to the reader if an R2D packet is not successfully decoded.

[0200] Paragraph 47. A tag / A-IoT device comprising transceiver circuitry configured to transmit signals to and / or to receive signals from one or more other tag / A-IoT devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices, and controller circuitry configured to control the transceiver circuitry to receive a reader-to- device (R2D) signal from a communications apparatus acting as a reader device, the communications apparatus operating with a wireless communications network and the R2D signal being transmitted via a radio access interface of the wireless communications network between the reader device and the tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part. Paragraph 48. Circuitry for a communications apparatus operating as a reader device forming part of a wireless communications network, the circuitry comprising transceiver circuitry configured to transmit signals to and / or to receive signals from one or more other tag / A-IoT devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices, and controller circuitry configured to control the transceiver circuitry to transmit a reader-to- device (R2D) signal for receipt by a tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

[0201] Paragraph 49. Circuitry for a tag / A-IoT device, the circuitry comprising transceiver circuitry configured to transmit signals to and / or to receive signals from one or more other tag / A-IoT devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices, and controller circuitry configured to control the transceiver circuitry to receive a reader-to- device (R2D) signal from a communications apparatus acting as a reader device, the communications apparatus operating with a wireless communications network and the R2D signal being transmitted via a radio access interface of the wireless communications network between the reader device and the tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

[0202] Paragraph 50. A computer program which, when the program is executed by a computer, cause the computer to perform the method of any one of paragraphs 1 to 23 or any one of paragraphs 25 to 46.

[0203] Paragraph 51. A non-transitory computer-readable storage medium storing a computer program according to paragraph 50.

[0204] REFERENCES

[0205] [1] RP-234058, “New SID: Study on solutions for Ambient loT (Internet of Things) in NR”. RAN plenary #102. Edinburgh. December 2023.

[0206] [2] TR 38.913, “3rdGeneration Partnership Project; Technical Specification Group Radio Access Network; Study on Scenarios and Requirements for Next Generation Access Technologies (Release 14)”, 3GPP, V14.3.0, August 2017. [3] ‘Study Ambient loT (Internet of Things) in RAN’, 3 GPP TR38.848. https: / / www.3gpp.org / ftp / Specs / archive / 38_series / 38.848 / 38848-i00.zip

[0207] [4] Van Huynh, Nguyen, Dinh Thai Hoang, Xiao Lu, Dusit Niyato, Ping Wang, and Dong In Kim. "Ambient Backscatter Communications: A Contemporary Survey." IEEE Communications Surveys & Tutorials 20, no. 4 (2018): 2889-2922.

[0208] [5] RP-234065, “New WID: Enhancements of network energy savings for NR,” 3GPP TSG RAN Meeting# 102, Edinburgh, Scotland, December 1 lth-15th, 2023

[0209] [6] GSMA, 5G energy efficiencies: Green is the new black, https: / / data.gsmaintelligence.com / api-web / v2 / research-file- download?id=54165956&file=241120-5G-energy.pdf

[0210] [7] ‘Study Ambient loT (Internet of Things) in RAN’, 3 GPP TR 38.848. https: / / www.3gpp.org / ftp / Specs / archive / 38_series / 38.848 / 38848-i00.zip

[0211] [8] Rl-2403821 “Report of RANl#116bis meeting”. ETSI MC, 3GPP TSGRAN WG1 #117, Fukuoka, Japan, May 20th - May 24th, 2024.

[0212] [9] Draft Report of 3GPP TSG RAN WG1 #117 v0.2.0’, 3GPP TSG RAN WG1 #117, Fukuoka, Japan, May 20th - May 24th, 2024.

[0213]

[0010] ‘Study on Low-Power Wake-Up signal and Receiver for NR’, 3GPP TR 38.869. https: / / www.3gpp.org / ftp / Specs / archive / 38_series / 38.869 / 38869-i00.zip

[0214]

[0011] European patent application EP24192725.0

Claims

CLAIMS1. A method of operating a reader device forming part of a wireless communications network and configured to transmit signals to and / or to receive signals from one or more other tag / Ambient loT (A-IoT) devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices, the method comprising: transmitting a reader-to-device (R2D) signal for receipt by a tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF- keying (OOK) modulation, wherein the packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

2. A method of claim 1, comprising modulating the one or more OFDM symbols of the data bearing part according to a first OOK modulation scheme, and modulating the one or more OFDM symbols of the control information part according to a second OOK modulation scheme, the format of the control information part being different to the format of the data bearing part as a result of the second OOK modulation scheme being different to the first OOK modulation scheme.

3. A method of claim 2, wherein the second OOK modulation scheme is more tolerant to clock errors than the first OOK modulation scheme.

4. A method of claim 2, wherein the second OOK modulation scheme is an OOK-1 scheme and the first OOK modulation scheme is an OOK-4 scheme.

5. A method of claim 1, comprising forming the control information part with a plurality of timing pulses, each of the one or more OOK modulated OFDM symbols carrying the control information and includes one or more of the timing pulses, and forming the data bearing part with a plurality of timing pulses, each of one or more OOK modulated OFDM symbols carrying data and includes one or more of the timing pulses, wherein a density of timing pulses in respect of a number of the timing pulses within a time window is greater in the control information part than the data bearing part.

6. A method of claim 5, wherein the timing pulses comprise OOK signals with a chip duration which is less than a chip rate of the one or more OOK modulated OFDM symbols.

7. A method of claim 1, comprising forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part to carry data and not modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part.

8. A method of claim 1, comprising forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, determining channel conditions for communicating the R2D signal, and depending on the channel conditions either modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part with a known pattern, or modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part with a pattern that is function of transmitted data, and modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part with a known pattern.

9. A method of claim 1, comprisingforming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and depending on a device type, either modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part to carry data with a known pattern, or modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part with a pattern that is function of transmitted data, and modulating the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part with a known pattern.

10. A method of claim 1, comprising forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, wherein the transmitting the R2D signal comprises transmitting the tail portion and the CP portion of each of the OOK modulated OFDM symbols carrying the control information with a power which is greater than a portion modulated with the control information, and greater than a power with which the tail portion and the CP portion of the OOK modulated OFDM symbols of the data bearing part carrying the data is transmitted.

11. A method of claim 9, wherein the power with which the tail portion and the CP portion of each of the OOK modulated OFDM symbols carrying the control information with respect to the power with which the portion modulated with the data is based on the device type.

12. A method of claim 9, comprisingdetermining channel conditions for communicating the R2D signals, wherein the power with which the tail portion and the CP portion of each of the OOK modulated OFDM symbols carrying the control information with respect to the power with which the portion modulated with the data is based on the determined channel conditions.

13. A method of claim 1, comprising forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of one or more parts of each of the OFDM symbols being modulated with a data bit of the control information, and forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of one or more parts of the OFDM symbol being modulated with a bit of the data, wherein each of the one or more parts of the OFDM symbols are repeated one or more times to represent each of the data bits of the control information, the format of the data bearing part being different to the format of the control information as a result of the repetition of the one or more parts of the OFDM symbols to represent the one or more data bits of the control information.

14. A method of claim 13, wherein each of the one or more parts of the OFDM symbols are repeated one or more times to represent each of the data bits carried by the data bearing part, and a number of repetitions of the one or more parts of the OFDM symbols to represent a bit of the control information is greater than a number of repetitions of the one or more parts of the OFDM symbols to represent a data bit of the data bearing part.

15. A method of claim 5, wherein the forming the control information part includes forming the control information part with one or more OOK modulated OFDM symbols carrying the control information, each of one or more parts of each of the OFDM symbols being modulated with a data bit of the control information, and the forming the data bearing part includes forming the data bearing part with one or more OOK modulated OFDM symbols carrying data, each of one or more parts of the OFDM symbol being modulated with a bit of the data, wherein the each of the one or more parts of the OFDM symbols is repeated one or more times to represent the data bits of the control information, the format of the data bearing part being different to the format of the control information as a result of the repetition of the one or more parts of the OFDM symbols to represent the one or more data bits of the control information.

16. A method of claim 1, comprising forming the R2D signal from a plurality of the one or more packets, and repeating a first of the plurality of packets one or more times.

17. A method of claim 16, comprising adding a sequence number to each of the plurality of packets which uniquely identifies that packet.

18. A method of claim 1, comprising forming the R2D signal from a plurality of the one or more packets, and forming each packet with a preamble followed by the control information part, followed by the data bearing part.

19. A method of claim 18, wherein the preamble of a first of the packets is longer than the preamble of subsequent packets.

20. A method of claim 18, forming the preamble of the first packet with a start delimiter.

21. A method of claim 1, wherein the control information includes an indication of a length of the packet.

22. A method of claim 1, wherein the control information includes an indication of a tag / A- loT device to which the R2D signal is transmitted.

23. A method of claim 1, wherein the control information includes an indication of a chip length of the OOK modulation representing the data carried by the data bearing portion.

24. A communications apparatus operating as a reader device forming part of a wireless communications network, the communications apparatus comprising transceiver circuitry configured to transmit signals to and / or to receive signals from one or more other tag / A-IoT devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices, and controller circuitry configured to control the transceiver circuitry to transmit a reader-to- device (R2D) signal for receipt by a tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOKmodulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

25. A method performed by a tag / A-IoT device, the method comprising receiving a reader-to-device (R2D) signal from a communications apparatus acting as a reader device, the communications apparatus operating with a wireless communications network and the R2D signal being transmitted via a radio access interface of the wireless communications network between the reader device and the tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

26. A method of claim 25, wherein the one or more OFDM symbols of the data bearing part have been modulated according to a first OOK modulation scheme, and the one or more OFDM symbols of the control information part have been modulated according to a second OOK modulation scheme, the format of the control information part being different to the format of the data bearing part as a result of the second OOK modulation scheme being different to the first OOK modulation scheme.

27. A method of claim 26, wherein the second OOK modulation scheme is more tolerant to clock errors than the first OOK modulation scheme.

28. A method of claim 26, wherein the second OOK modulation scheme is an OOK-1 scheme and the first OOK modulation scheme is an OOK-4.

29. A method of claim 25, wherein the control information part includes a plurality of timing pulses, each of one or more OOK modulated OFDM symbols carrying the control information and includes one or more timing pulses, and the data bearing part includes a plurality of timing pulses, each of one or more OOK modulated OFDM symbols carrying data including one or more timing pulses, wherein a density of timing pulses, in respect of a number of timing pulses within a time window is greater in the control information part than the data bearing part, and the method includes using the timing pulses to acquire a clock synchronisation for detecting the control information and the data from the OOK modulated OFDM symbols.

30. A method of claim 29, wherein the timing pulses comprises OOK signals with a chip duration which is less than a chip rate of the one or more OOK modulated OFDM symbols.

31. A method of claim 25, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part includes one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated to carry data and the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part have not been modulated, and the method comprises using the tail portion and the CP of the control information part to acquire a clock synchronisation for detecting the control information and the data from the OOK modulated OFDM symbols.

32. A method of claim 25, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part including one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and depending on the channel conditions either the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have not been modulated to carry data, or the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated to carry data, and the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part have been modulated to carry data, and the method comprises using the tail portion and the CP of the control information part and the data part to synchronise a clock of the tag / A-IoT device.

33. A method of claim 25, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the databearing part including one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part have been modulated with a known pattern and depending on the channel conditions either the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated with a known pattern, or the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated with a pattern that is a function of transmitted data.

34. A method of claim 25, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part including one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, comprising determining a sampling frequency offset (SFO) of the tag / A-IoT device caused by an error in a clock of the tag / A-IoT device and a clock used to form the R2D signal, transmitting an indication of the SFO to the reader, and depending on the SFO either the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have not been modulated to carry data, or the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated to carry data, and the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part have been modulated to carry data, and the method comprises using the tail portion and the CP of the control information part and the data part to synchronise a clock of the tag / A-IoT device.

35. A method of claim 25, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part including one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, anda cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, comprising determining a device type of the tag / A-IoT device, transmitting an indication of the device type to the reader, and depending on the device type either the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated with a known pattern, or the tail portion and the CP of the one or more OOK modulated OFDM symbols of the data bearing part have been modulated with a pattern that is a function of transmitted data, and the tail portion and the CP of the one or more OOK modulated OFDM symbols of the control information part have been modulated with a known pattern.

36. A method of claim 25, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, the data bearing part includes one or more OOK modulated OFDM symbols carrying data, each of the OOK modulated OFDM symbols having a tail portion located at an end of the OFDM symbol, and a cyclic prefix (CP) located at the start of the OFDM symbol, the CP being a duplicate of the tail portion, and the tail portion and the CP portion of each of the OOK modulated OFDM symbols carrying the control information have been transmitted with a power which is greater than a portion modulated with the control information, and greater than a power with which the tail portion and the CP portion of the OOK modulated OFDM symbols of the data bearing part carrying the data.

37. A method of claim 36, comprising transmitting an indication of the device type, and receiving the R2D signal, wherein a power with which the tail portion and the CP portion of each of the OOK modulated OFDM symbols carrying the control information with respect to the power with which the portion modulated with the data is based on the device type.

38. A method of claim 25, wherein the control information part includes one or more OOK modulated OFDM symbols carrying the control information, each of one or more parts of each of the OFDM symbols having been modulated with a data bit of the control information, and the data bearing part includes one or more OOK modulated OFDM symbols carrying data, each of one or more parts of the OFDM symbol having been modulated with a bit of the data, wherein each of the one or more parts of the OFDM symbols are repeated one or more times to represent each of the data bits of the control information, the format of the data bearing part being differentto the format of the control information as a result of the repetition of the one or more parts of the OFDM symbols to represent the one or more data bits of the control information.

39. A method of claim 38, wherein each of the one or more parts of the OFDM symbols are repeated one or more times to represent each of the data bits carried by the data bearing part, and a number of repetitions of the one or more parts of the OFDM symbols to represent a bit of the control information is greater than a number of repetitions of the one or more parts of the OFDM symbols to represent a data bit of the data bearing part.

40. A method of claim 25, wherein the R2D signal includes a plurality of the one or more packets, a first of the plurality of packets is repeated one or more times, and each of the plurality of packets includes a sequence number which uniquely identifies the packet, and the method comprises detecting the first packet from the plurality of repetitions of the first packet in the R2D signal, and once the sequence number has been detected not decoding repeated packets having the same sequence number after detecting the sequence number of the first packet.

41. A method of claim 25, wherein the R2D signal includes a plurality of the one or more packets, each packet including a preamble followed by the control information part, followed by the data bearing part, and the preamble of a first of the packets is longer than the preamble of subsequent packets, and the method comprises using the preamble of the first packet to acquire a clock synchronisation for detecting the control information and the data from the OOK modulated OFDM symbols from the R2D signal.

42. A method of claim 41, wherein the preamble of the first packet includes a start delimiter, and the method comprises using the preamble of the first packet to acquire a clock synchronisation until the delimiter is detected.

43. A method of claim 25, wherein the control information includes an indication of a length of the packet.

44. A method of claim 25, wherein the control information includes an indication of a tag / A- loT device to which the R2D signal is transmitted.

45. A method of claim 25, wherein the control information includes an indication of a chip length of the OOK modulation representing the data carried by the data bearing portion.

46. A method of claim 25, comprising sending a NACK to the reader if an R2D packet is not successfully decoded.

47. A tag / A-IoT device comprising transceiver circuitry configured to transmit signals to and / or to receive signals from one or more other tag / A-IoT devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices, and controller circuitry configured to control the transceiver circuitry to receive a reader-to- device (R2D) signal from a communications apparatus acting as a reader device, the communications apparatus operating with a wireless communications network and the R2D signal being transmitted via a radio access interface of the wireless communications network between the reader device and the tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

48. Circuitry for a communications apparatus operating as a reader device forming part of a wireless communications network, the circuitry comprising transceiver circuitry configured to transmit signals to and / or to receive signals from one or more other tag / A-IoT devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices, and controller circuitry configured to control the transceiver circuitry to transmit a reader-to- device (R2D) signal for receipt by a tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

49. Circuitry for a tag / A-IoT device, the circuitry comprisingtransceiver circuitry configured to transmit signals to and / or to receive signals from one or more other tag / A-IoT devices of the wireless communications network via a radio access interface between the reader device and the one or more other tag / A-IoT devices, and controller circuitry configured to control the transceiver circuitry to receive a reader-to- device (R2D) signal from a communications apparatus acting as a reader device, the communications apparatus operating with a wireless communications network and the R2D signal being transmitted via a radio access interface of the wireless communications network between the reader device and the tag / A-IoT device, wherein the R2D signal comprises one or more packets, each packet comprising orthogonal frequency-division multiplexing (OFDM) symbols of the radio access interface modulated according to ON-OFF-keying (OOK) modulation, wherein the packet of OFDM symbols comprises a data bearing part comprising one or more OOK modulated OFDM symbols and a control information part comprising one or more OOK modulated OFDM symbols, the format of the control information part being different to the format of the data bearing part.

50. A computer program which, when the program is executed by a computer, cause the computer to perform the method of claim 1 or claim 25.

51. A non-transitory computer-readable storage medium storing a computer program according to claim 50.

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