Integrated sensing and communication

Abstract

Methods and apparatuses for privacy protection in wireless sensing are provided A method comprises obtaining a signal for transmission by a transmitting apparatus, and dividing the obtained signal into a plurality of portions. The method further comprises calculating altered properties of the obtained signal such that, when an altered signal is obtained by applying the altered properties to the obtained signal, artifacts are introduced into the altered signal relative to the obtained signal. The method also comprises transmitting, by the transmitting apparatus, the altered signal, and receiving a reflected signal that is a reflection of the transmitted altered signal from a target. The method still further comprises estimating, using the altered properties of the transmitted altered signal and the reflected signal, one or more properties of the target.

Description

[0001] Integrated Sensing and Communication

[0002] Technical field

[0003] The present disclosure relates to privacy protection. In particular, the present disclosure relates methods and apparatuses for privacy protection in wireless sensing.

[0004] Background

[0005] Integrated Sensing and Communication (ISAC) is a technology which combines wireless communication and sensing into a single platform, allowing shared usage of hardware and resources. By way of example, ISAC, which may also be referred to as joint communication and sensing (JCAS / JCS), dual-function radar and communications (DFRC), may be integrated into a mobile communication network, thereby expanding a networks functionality beyond only communication. Thus, ISAC systems may detect and estimate specific target information, image and map the environment, while simultaneously supporting data communication.

[0006] The sensing and communication dual functionality of ISAC systems may introduce vulnerabilities due to unauthorized interceptions. By way of example, third parties may exploit the sensing functionality to obtain their own knowledge of targets and environments, potentially revealing private information. Such unauthorized access could lead to privacy violations, including unauthorized tracking or identification.

[0007] It is therefore desirable to improve privacy protection in wireless sensing.

[0008] Summary

[0009] The present invention is defined in the independent claims, to which reference should now be made. Advantageous optional features are set out in the sub claims.

[0010] According to an aspect, there is provided a method for privacy protection in wireless sensing. The method may be a computer-implemented method. The method may comprise the steps: obtaining a signal for transmission by a transmitting apparatus;dividing the obtained signal into a plurality of portions; calculating altered properties of the obtained signal such that, when an altered signal is obtained by applying the altered properties to the obtained signal, artifacts are introduced into the altered signal relative to the obtained signal; transmitting, by the transmitting apparatus, the altered signal; receiving a reflected signal that is a reflection of the transmitted altered signal from a target; and estimating, using the altered properties of the transmitted altered signal and the reflected signal, one or more properties of the target.

[0011] Artifacts may be, for example, artificial noise, artificial sidelobes and / or other types of perturbations in the altered signal.

[0012] The altered properties may comprise alterations to the configured power levels of at least one of the plurality of portions, such that the altered signal comprises portions having a higher power level, p, and portions having a lower power level, q. The lower power level may be lower than the higher power level.

[0013] The lower power level portions and higher power level portions may be interleaved. The lower power level portions and higher power level portions may define a repeating pattern.

[0014] The obtained signal may be a frequency division multiplexed, FDM, signal and the plurality of portions may be a plurality of frequency sub-bands; or the obtained signal may be a time division multiplexed, TDM, signal and the plurality of portions may be a plurality of time-slots; or the obtained signal may be a delay-Doppler or time-frequency-space multiplexed, TFS, signal and the plurality of portions may be a plurality of delay-Doppler bins; or the obtained signal may be a chirp division multiplexed, CDM, signal and the plurality of portions may be a plurality of chirps; or the obtained signal may be a time-sequency division multiplexed, TSM, signal and the plurality of portions may be a plurality of time-sequency bins.

[0015] The obtained signal may comprise an orthogonal signal. For example, the obtained signal may comprise an orthogonal frequency division multiplexed, OFDM, signal.The obtained signal may be divided by transmission time to obtain the plurality of portions. The altered signal may be transmitted in a time frame, such as a radio frame, sub-frame or slot, and the signal may be divided into portions. The portions may be referred to as sub-signals. Each portion may comprise one or more of the signals described above, that is FDM, TDM, TFS, CDM and / or TSM and the signals may be orthogonal, leading to OFDM, OTDM, OTFS, OCDM, OTSM. The altered signal may be a pulsed signal, and the sub-signals may form the pulses. That is, each portion may comprise a pulse of the pulsed signal.

[0016] The transmitting apparatus may form part of a 3rdGeneration Partnership Project, 3GPP, communication network. The transmitting apparatus may be a base station or a User Equipment, UE. The transmitting apparatus may be configured with a transmitter and / or transceiver for transmitting the altered signal.

[0017] The altered signal may be used in a 3GPP Integrated Sensing and Communication, ISAC, system. The altered signal may comprise random data, such as random communication data, which has been modulated to generate the obtained signal. The communication data may be communication data used in the ISAC system for communication between two apparatuses such as communication between base stations and / or UEs.

[0018] The transmitting apparatus may additionally or alternatively be configured to use an Institute of Electrical and Electronics Engineers, IEEE, 802.11 standard. The transmitting apparatus may be a wireless local area network, WLAN, access point or a WLAN User Equipment, UE.

[0019] The transmitting apparatus may be a RADAR transmitter. The obtained signal may be a pulsed signal. Further, the transmitting apparatus may be an apparatus for long range (LoRa) radio transmission and Internet of Things (IoT) transmissions. The obtained / altered signal type may be adapted as required, i.e., the obtained / altered signal may be a microwave or radio wave, millimetre wave, optical or any other suitable signal type.The transmitting apparatus may receive the reflected signal. That is, the transmitting apparatus may be configured with a receiver and / or transceiver for receiving the reflected signal.

[0020] A plurality of transmitting apparatuses may be used to transmit the altered signal. At least one receiving apparatus may receive the reflected signal. The method may further comprise communicating the altered properties of the obtained signal to at least one receiving apparatus.

[0021] The transmitting apparatus and / or plurality of transmitting apparatuses and / or at least one receiver may form a distributed ISAC system. The distributed ISAC system may be configured with multi-antenna transmission. A weighted summation of multi-user communication and multi-input multi-output (MIMO) signals may be used as the altered signal.

[0022] The one or more properties which may be estimated using the altered properties may comprise at least one of: target presence (e.g. range and / or angle); target location; target size and / or shape; target physical classification (e.g., type of target: human, animal type, vehicle type, and so on); target velocity; and imaging information. The target physical classification may be based on the physical shape of the target. A micro-Doppler technique may determine further properties of the target.

[0023] The target may be a human or animal. The one or more properties which may be estimated may further comprise at least one of: heart rate; breathing rate; behavioural recognition; and fall detection. The properties of the human / animal may be determined based on micro-doppler sensing. The behavioural recognition may include, for example, gesture control. Thus, the method may detect human / animal presence, density, location, behaviour and / or health status.

[0024] According to another aspect there is provided an information processing system for providing privacy protection in wireless sensing; the information processing system may comprise a transmitting apparatus and a receiving apparatus. The transmitting apparatus may comprise a memory and a processor connected to the memory. The processor may be configured to: obtain a signal for transmission by the transmittingapparatus; divide the obtained signal into a plurality of portions; calculate altered properties of the obtained signal such that, when an altered signal is obtained by applying the altered properties to the obtained signal, artifacts are introduced into the altered signal relative to the obtained signal; and instruct the transmitting apparatus to transmit the altered signal. The receiving apparatus may be configured to: receive a reflected signal that is a reflection of the transmitted altered signal from a target; estimate, using the altered properties of the transmitted altered signal and the reflected signal, one or more properties of the target.

[0025] The transmitting apparatus and the receiving apparatus may be co-located. The transmitting apparatus and receiving apparatus may form a sensing apparatus. The transmitting apparatus and receiving apparatus may share the memory and processor. That is, the transmitting apparatus and receiving apparatus may use the same memory and processor. Alternatively, the transmitting apparatus and receiving apparatus may be separate, that is, not co-located. The receiving apparatus may comprise its own memory and processor which may be referred to as a second memory and a second processor respectively.

[0026] A plurality of transmitting apparatuses may be used to transmit the altered signal. The transmitting apparatus may be one of the plurality of transmitting apparatuses. Each transmitting apparatus of the plurality of transmitting apparatuses may transmit a portion of the altered signal and / or each transmitting apparatus may transmit the altered signal.

[0027] A plurality of receiving apparatuses may receive the reflected signal. The receiving apparatus may be one of the pluralities of receiving apparatuses. Each receiving apparatus may receive the reflected signal. At least one transmitting apparatus may be configured to communicate the altered properties of the obtained signal to at least one receiving apparatus.

[0028] According to another aspect there is provided a computer program which, when run on a computer, causes the computer to carry out one or more of the methods described above.The methods described herein are described in terms of particular embodiments. Other embodiments are within the scope of the following claims. For example, the steps of the methods may be performed in a different order and still achieve desirable outcome.

[0029] The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore, except where mutually exclusive, any feature described herein may be applied to any aspect and / or combined with any other feature described herein. The scope of the disclosure is defined by the claims.

[0030] Brief description of the Drawings

[0031] For a better understanding of the present disclosure, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the following drawings in which:

[0032] Figure 1 shows steps of a method described herein for privacy protection in wireless sensing;

[0033] Figures 2A and 2B show example networks which may perform / integrate the methods described herein.

[0034] Figures 3A-3C show the effects of altered signal parameters according to the methods herein on privacy protection;

[0035] Figure 4 shows a flow chart of steps of an exemplary method for ISAC signal design with privacy protection in a single-node scenario with single-antenna transmission.

[0036] Figures 5A-5D show example apparatuses which may be used with the exemplary method described herein;

[0037] Figure 6 shows example Range-Doppler maps of resolved targets from altered signals using the exemplary method described herein;Figures 7A-7C show examples of performance plots for communication, legitimate sensing and eavesdropper sensing, for different altered signal parameters according to the exemplary method;

[0038] Figure 8 shows a flow chart of steps of a second exemplary method for ISAC signal design with privacy protection in a distributed ISAC System with Multiantenna Transmission;

[0039] Figures 9A and 9B show example apparatuses which may be used with the second exemplary method described herein;

[0040] Figure 10A shows exemplary target localization plots based on secure sensing ISAC transmission with two distributed ISAC nodes using the second exemplary method;

[0041] Figure 10B shows beam patterns for each of the signal to interference plus noise ratios (SINR) in Figure 10a;

[0042] Figures 11A-11C show exemplary performance plots for ISAC signal design with privacy protection in the case of a distributed ISAC system;

[0043] Figure 12 shows an example transmitting apparatus for performing steps of the methods described herein;

[0044] Figure 13 shows a block diagram of an information apparatus, or computer device for performing steps of the methods described herein.

[0045] Detailed description

[0046] Sensing systems, such as radio detection and ranging (RADAR) systems, are widely used in various technical areas, including: detection of uncrewed aerial vehicles (UAVs), positioning of automotive vehicles, and so on. A simple sensing system may comprise a transmitter which transmits a sensing signal and a receiver which receives the reflected transmitted signal. Typically, a signal may be transmitted as a ‘chirp’ and a reflected signal may be processed using matched filtering to determine a propertyabout a target object. For instance, sensing may be performed to determine the location of a target object.

[0047] Mobile communication systems, such as 3rdGeneration Partnership Project, 3GPP, systems, constantly transmit and receive mobile signals. By way of example, wireless mobile signals are constantly being transmitted between base stations (such as next generation NodeBs, gNBs and evolved NodeBs, eNBs) and user equipments (UEs). Furthermore, systems which conform to Institute of Electrical and Electronics Engineers (IEEE) standards, such as wireless local area networks (WLANs) access points and WLAN User equipment, also transmit wireless signals for communication. Sensing systems may be integrated into communication systems, thus developing integrated sensing and communication, ISAC. IEEE 802.11 standard, and in particular, IEEE, 802.11bf (available at https: / / ieeexplore.ieee.org / stamp / stamp.jsp?arnumber=10192291 as of 6 January 2025) addresses ISAC integration in WLANs.

[0048] The use of current mobile communication networks, such as 5G networks, may have limitations on the accuracy and reliability of ISAC. For instance, a 5G network using the millimetre wave (mmWave) spectrum, e.g., frequency range 2 (FR2), between 24.25 GHz to 71.0 GHz, with a bandwidth of several 100MHz, may have a high sensing resolution but with very limited coverage area. However, with the advent of 6G and the possible introduction of the centimetre wave, cm Wave, with a frequency between, for example 7-15 GHz, a superior resolution may be provided over a large coverage area. Thus, 6G may provide a suitable platform for implementing ISAC. Similar advancements using the IEEE standards may also provide effective ISAC systems.

[0049] As a consequence of the increase in resolution supported by 6G systems, the use of ISAC may become increasingly widespread. The integration of sensing into 6G systems means RADAR services may become a commodity. ISAC systems, which may combine communication and sensing functions using the same hardware and spectral resources, may face unresolved security challenges. In particular, ISAC systems may face the unique challenge of “sensing eavesdroppers”. A “sensing eavesdropper” may be an unauthorized system, such as a passive radar, that intercepts ISAC signals to estimate target information such as range, velocity, and / orangle of a target object, or perform radar imaging (all of which may be private information). Unauthorized parties may thus gather private information about sensing targets and environments. In this sense, an unauthorized system may be a system which does not have authorized access to intercept / receive signals transmitted by the ISAC system. A sensing target may be an object which is, for example, passive to radio signals, or an emitting device itself.

[0050] Key challenges in sensing security of ISAC systems may include one or more of:

[0051] 1) Uncertainty of Eavesdropper Location: The unknown location of sensing eavesdroppers may make it difficult to prevent ISAC transmissions from being leaked to the eavesdroppers.

[0052] 2) Uncontrollable Scattering Signals: ISAC signals may be subject to unpredictable scattering, which may make it hard / impossible to control the signal’s reflection toward the sensing eavesdropper.

[0053] 3) Uncertainty of Location of Target to be protected: The estimation of location of the target itself may be subject to noise and errors, and therefore may make it difficult to protect against potential eavesdropping.

[0054] 4) Lack of Data Encryption: There may be no data link to encrypt so instead sensing eavesdropping may involve the ability of an unauthorised entity to perform its own sensing of targets and environments. Sensitive information may therefore remain vulnerable to unauthorized access.

[0055] As a consequence of the above issues, conventional higher-layer communication security techniques, such as encryption, may not apply to the above scenario. Moreover, physical-layer communication security techniques, such as artificial noise (AN) transmission, may be insufficient to ensure sensing security within ISAC systems.

[0056] The present disclosure therefore may help address sensing security issues in integrated sensing and communication (ISAC) systems. Furthermore, the methods and apparatuses described herein may be used with any suitable sensing systems,including sensing only solutions, such as RADAR. The method may also be used in, for example, long range (LoRa) radio transmission and Internet of Things (IoT) transmissions. Thus, the altered signal type may be adapted as required, i.e., the altered signal may be a microwave or radio wave, millimetre wave, optical or any other suitable signal type.

[0057] Figure 1 shows steps of a method 100 described herein for privacy protection in wireless sensing. The method may be a computer-implemented method. The method may, for instance, prevent unauthorized receivers from accurately detecting and estimating target and / or environment information using ISAC signals. That is, the method may help to counter adversary sensing and / or provide target privacy protection in a network.

[0058] The method of Figure 1 comprises an obtaining step s10. In the obtaining step, a signal for transmission may be obtained by a transmitting apparatus. The step of obtaining the signal for transmission may comprise generating the signal at the transmitting apparatus, or receiving the signal from a source external to the transmitting apparatus (for example, a signal generator). The transmitting apparatus may comprise a transmitter and / or a transceiver for transmitting the signal. The transmitter may be, for example, a node, base station, gNb, user equipment, router and / or any suitable transmitting apparatus. The signal may comprise random data, such as random communication data, which has been modulated to generate the obtained signal.

[0059] In a dividing step s20, the obtained signal is divided into a plurality of portions. For instance, the obtained signal may be a frequency division multiplexed, FDM, signal and the plurality of portions may be a plurality of frequency sub-bands. The method may, be applied to other signals such as time division multiplexed signals, delay-Doppler or time-frequency-space multiplexed signals, a chirp division multiplexed signals, and / or a time-sequency division multiplexed signals. The portions for the listed signals may depend on the type of signal and are detailed herein.

[0060] In a calculating step s30, altered properties of the obtained signal are calculated such that, when an altered signal is obtained by applying the altered properties to theobtained signal, artifacts are introduced into the altered signal relative to the obtained signal. The “calculating step” may alternatively be referred to as a “determining step”.

[0061] In a transmitting step s40 the altered signal is transmitted, by the transmitting apparatus. For instance, the altered signal may be transmitted by a transmitter and / or transceiver of the transmitting apparatus. The altered signal may be transmitted by one or more transmitting apparatuses. For instance, a plurality of transmitting apparatuses may transmit the altered signal. Each apparatus may transmit the signal or may share the signal and may each transmit portions of the signal.

[0062] In a receiving step s50, a reflected signal is received that is a reflection of the transmitted altered signal. The reflected signal may be a reflection of the signal from a target. That is, the altered signal may be transmitted and may reflect off a target (which may be an object) and may then be received. The target may not itself be configured to emit or receive radio signals, that is, may be a passive target. The reflected altered signal may be received by the transmitting apparatus, in which case the transmitting apparatus may comprise a receiver and / or transceiver, and / or the reflected altered signal may be received by another apparatus. The other apparatus may comprise a receiver and / or transceiver for receiving the reflected altered signal. Examples of targets are vehicles and / or animals (including humans).

[0063] In an estimating step s60, using the altered properties of the transmitted altered signal and the reflected altered signal, one or more properties of the target are estimated. The one or more properties of the target may comprise at least one of: target presence, target location, target shape, target size, target physical classification, target velocity, and imaging information. In an instance where the target is a human or animal, the one or more properties may further comprise at least one of: heart rate, breathing rate, behavioural recognition, and fall detection.

[0064] The methods provided herein may provide solutions to the above identified challenges. For instance, by altering the obtained signal, which in an example may be a signal used in ISAC, so as to introduce artifacts, such as artificial noise / imperfections / perturbations and so on, accurate sensing at an eavesdropping device may be impaired, but may be resolvable at a legitimate sensing device (that is, a receiverwhich is authorized to receive the signal and to sense the target). Advantages of the method disclosed herein may be:

[0065] 1) Preventing Illegitimate Eavesdropping: The method may confuse’ potential sensing eavesdroppers by introducing ambiguity to the detection of any of the target parameters. It may also introduce artificial ghost targets incorporated into the altered obtained signal, effectively preventing unauthorized detection of sensing targets. The ambiguity of estimation may be tuned to an extent that makes the target estimates unusable by the eavesdropping device.

[0066] 2) No Prior Knowledge of Eavesdropper’s Location or Channel State Required: The method may not require prior information about the eavesdropper’s location or channel state, enabling wide-area sensing security coverage. However, if prior information of the eavesdroppers location was known, the method may be used to avoid transmitting towards the eavesdropper and / or may transmit strong noise / jamming signals towards the eavesdropper.

[0067] 3) No Prior Knowledge of Target’s Location, Parameters or Channel State Required: The method may not require prior information about the target’s location, parameters or channel state, enabling environment-agnostic sensing security coverage. The method simply relies on altering the transmitted signal to artificially increase the ambiguity of estimation at any receiver for any environment.

[0068] 4) No Additional Hardware Required: The method may alter a signal design, for example, by introducing altered properties (artifacts) such as artificial noise into an obtained signal. This signal design may improve security, and may eliminate the need for any additional hardware. This may make the solution both cost- effective and easy to implement, and compatible to any communication, RADAR, or ISAC device.

[0069] The method described herein may be applied to an ISAC system and may improve sensing security performance. By enhancing security through signal design, the method may avoid the complexities of additional hardware or intricate setups. Thissimplicity and effectiveness may make the method practical and suitable for wide-scale deployment in various applications, such as ISAC, and to a wide range of wireless communications standards, such as 3GPP, WiFi, LoRa, loT and others.

[0070] Figure 2 shows example networks which may perform / integrate the method described herein. In particular, Figure 2A shows a network 200a with a single ISAC node 205a in communication with a user equipment (UE) 210a. In this example, the ISAC node is an example of the transmitting apparatus and may be, for example, a base station, such as a gNb. The transmitting apparatus (ISAC node) and UE may form part of a 3rdGeneration Partnership Project, 3GPP, communication network. The ISAC node being in communication with the UE may form a “communication” part of the integrated sensing and communication system.

[0071] Furthermore, as indicated in Figure 2A, the ISAC node may function as a sensing device and may sense a target 215a. In this example, the target may be a vehicle (a car is shown). The network may also comprise a sensing eavesdropper 220a. This may be an unauthorized device. For example, the ISAC node, UE and / or target may not have authorized the sensing eavesdropper to perform sensing. The sensing eavesdropper may be configured to determine one or more properties of the target using signals transmitted by the ISAC system. The configuration of the sensing eavesdropper for determining the properties is described below.

[0072] In another example shown in Figure 2B, a network 200b may form a distributed ISAC system. The system shown in Figure 2B may be substantially similar to the system in Figure 2A but may comprise a further ISAC node, denoted as ISAC node 2206b and may comprise a central processing unit (CPU) 207B. Like reference signs are used in Figures 2Aand 2B (i.e., UE 210a, 210b, target 215a, 215b and sensing eavesdropper 220a, 220b). The central processing unit may control the ISAC nodes and / or may allow communication between the nodes. The obtained signal described in relation to Figure 1 may be obtained, for example, by an ISAC node from the CPU (but in another example the ISAC node may generate the signal).

[0073] Figures 2A and 2B show exemplary examples of telecommunications networks which may perform the methods described herein. In particular, the Figures show an exampleof a potential 6G networks which may conform to a 3GPP communication network. The 6G network is an exemplary example of a network which may be used with the methods described herein. However, the methods may be used with any suitable network. For example, the methods may be performed with a standalone sensing network, a 5G network or any other 3GPP network, and / or a network using an Institute of Electrical and Electronics Engineers (IEEE) standard.

[0074] As described above, in an example, the method for privacy protection in wireless sensing may be configured for ISAC sensing. In this example, the sensing eavesdropper may determine properties of a target from a signal transmitted by the ISAC node.

[0075] The following method may be used by a sensing eavesdropper signal model to determine properties within an ISAC system, and therefore compromise privacy within a network. The method may similarly be adapted for sensing in other networks:

[0076] Consider a sensing eavesdropper (Eve) using an ISAC signal for target detection, as illustrated in Figures 2A and 2B. The Eve may be assumed to have prior knowledge of the ISAC node location and a line-of-sight (LOS) channel.

[0077] The ISAC signal may be an Orthogonal frequency-division multiplexing (OFDM) signal. For instance, the ISAC signal may be an OFDM modulated signal within a telecommunications network. The below example is provided in relation to an OFDM signal. However, any suitable signal may be considered in this example.

[0078] A signal may be denoted as x e CLX1and may represent a transmitted OFDM signal in the frequency domain, with L subcarriers. The transmitted signal may be a signal transmitted by the ISAC node for object sensing used for sensing a target.

[0079] Assuming that an eavesdropper (Eve) is equipped with a sufficient number of receiving antennas, it may leverage an unintended leakage signal as a reference for sensing signal demodulation. The unintended leakage signal is shown in Figures 2A and 2B as a dashed line extending from the ISAC node to the sensing eavesdropper and may be denoted by yE r. The sensing eavesdropper may also receive a target-reflect signalfrom the target. That is, the ISAC node may transmit the sensing signal which is reflected from the target and received by the sensing eavesdropper. The reflected signal received by the sensing Eavesdropper may be referred to as a surveillance signal or surveillance target-reflected signal and may be denoted by yEsin the Figures. The surveillance (target-reflected) signal and the reference (unwanted leakage) signal received by Eve may be expressed as:

[0080] yEs= hsO x + zs, (Surveillance signal)

[0081] Equation 1

[0082] yEr= hrO x + zr, (Reference signal)

[0083] Equation 2

[0084] where hsis a target channel that may contain the target information to be estimated, hris the channel between the ISAC node and Eve, and zs, zrrepresent Gaussian noise. Here, O denotes the Hadamard product.

[0085] To demodulate the target channel hsat the Eve, the Eve may perform matched filtering using the reference signal. After compensating for the line-of-sight (LOS) channel in hr, the estimated target channel may be expressed as:

[0086] h

[0087]

[0088] s= hsO (x O x* ) + zm.

[0089] Equation 3

[0090] Here, zmmay include the effects of a non-line-of-sight (NLOS) channel between the ISAC node and the Eve and x* is the complex conjugate of x. Finally, the properties of the target, such as the target range, may be estimated from hs.

[0091] The product x O x* in Equation 3 may be directly related to an ambiguity function of the transmitted sensing signal. The ambiguity function may represent the distortion of the reflected sensing signal due to a receiver matched filter. Artificial sidelobes maybe introduced to the ambiguity function to introduce ambiguity in the target estimation. Thus, artificial targets may be generated in the Eve’s target estimation by controlling properties of the transmit signal x.

[0092] Figure 3A shows an example 300a of allocated subcarrier powers for ambiguity control of a transmit signal. That is, Figure 3A shows an example of modified properties of a transmission signal which may be applied to generate the altered signal. The ambiguity control may be for instance, the control / modification of a transmit signal to generate artificial targets in a sensing eavesdropper’s target estimation. As shown in the Figure, the altered signal may be an OFDM signal and may comprise L subcarriers. The x axis shows the OFDM sub carrier index, starting from 1 and counting to L and the y axis shows the allocated power for each sub-carrier.

[0093] The unambiguous range (maximum detectable range) in conventional OFDM radar with symbol duration Tp may be given by:

[0094] p — Tni' ■ c — L ■ c

[0095]

[0096] max2 2BIV

[0097] Equation 4

[0098] where BW is the signal bandwidth, and L / BW represents the inverse of the subcarrier spacing. In conventional RADAR systems, maximizing Rmax is often desirable for detecting distant targets. However, for privacy protection in, for example, a secure ISAC system, this property may be used to secure the sensing functionality by providing enhanced privacy protection.

[0099] To control ambiguity (for instance range ambiguity), altered properties of the transmitted signal may be calculated and applied to the transmitted signal before transmission. For example, sub carrier spacings of the transmitted signals may form a plurality of portions of the signal and an altered property of the signal may be alterations to the configured power levels of at least one of the plurality of portions. The altered signal may therefore comprise portions having a higher power level, p, and portions having a lower power level, q, the lower power level being lower than thehigher power level. The subcarrier power allocation, which may be periodic, may generate (periodic) ‘undesired’ peaks in the ambiguity function and therefore within the estimation range of Rmax. The peaks may be described as undesired as an Eve detecting the signal may therefore detect multiple peaks for the target location, e.g.,. multiple target locations for a single target. The peaks are purposefully introduced and are therefore desired for privacy protection purposes.

[0100] The periodic subcarrier power allocation may be expressed as follows: Let R = E[xxH] e CLx Ldenote the covariance matrix of the transmitted signal. The power allocated at each subcarrier may be found in the diagonal elements of R. The lower power level portions and higher power level portions may be interleaved. The lower power level portions and higher power level portions may define a repeating pattern. For example, for the ambiguity control, the subcarrier power may be constrained as:

[0101] R = diag(

[0102]

[0103] 7p, yfq, y / q,..., y / q, y[p, y[q, y[q,..., y[q,..., y[p, y[q, y[q,..., y[q),

[0104] Equation 5a

[0105] where

[0106]

[0107] Equation 6a

[0108] Here, K may be a common divisor of L, and PTmay be the total transmit power, as shown in Figure 3A. The variable K may be the spacing of subcarriers with peak power and may therefore be referred to as peak sub-carrier spacing and / or peak-power subcarrier spacing.

[0109] The parameter K may control the number of artificial peaks detected at the Eve, while the power ratio between p and q may determine the magnitude of these peaks. As shown in the Figure, the power p may be seen as a higher power level, which may be a peak subcarrier power, and q may be for instance a default subcarrier power. As aresult, the sensing secrecy may be influenced by the design choices for K and p, which in turn may affect both sensing and communication performance in the ISAC system.

[0110] The above example provides an implementation for range ambiguity control. An alternative embodiment, which may be referred to as Doppler ambiguity control, may be implemented through the application of power allocation along pulses (or OFDM symbols). The overall principles may remain consistent with those of range ambiguity control; however, the application domain may shift from frequency (subcarriers) to time (pulse-to-pulse) allocation. In this example it may be assumed that the system employs M OFDM pulses in a single transmission frame. In this case, the power allocation across pulses may be subject to the following constraint:

[0111] RD= diag(

[0112]

[0113] 7p, y / q, y / q,.... y / q, y / p, y / q, y / q,..., y / q,..., y / p, y / q, y / q,.... y / q),

[0114] Equation 5b

[0115] where

[0116] M ( M\

[0117] p — I- q ■ \ M — = PT F.

[0118]

[0119] K \ K)

[0120] Equation 6b

[0121] RDmay be the covariance matrix of the transmitted signal with M OFDM pulses and PT Fmay be the total transmit power in a single transmission frame. The behaviours of artificial peaks with respect to K, p, and q may be consistent with the example of the range ambiguity control. In this instance K may refer to the spacing between peakpower OFDM pulses (analogous to peak-power sub-carrier spacing). In this example, the obtained signal described in relation to Figure 1, may refer to a plurality of signals (sub signals) within a transmission frame. That is, the obtained signal may refer to a plurality of OFDM signals and / or time-slots within a transmission frame and a portion of the obtained signal may be an OFDM signal and / or time-slot. A time frame may refer to for example a radio frame. The frame may be 10ms long (for example in the case of 5G). The radio frame may comprise sub-frames and the sub-frames may compriseslots. 1 slot may comprise 14 OFDM signals. The time frame may alternatively refer to a subframe or a slot. As an example with the OFDM signals being configured with 15kHz sub carriers, the radio frame may comprise 10 subframes with each such frame comprising 1 slot and each slot comprising 14 OFDM signals.

[0122] The relationships between design parameters and sensing secrecy may be summarized as follows:

[0123] Peak subcarrier spacing K: may be used to determine the number of artificial peaks at a sensing eavesdropper. Thus, a larger value of K may offer a higher sensing security, (K may otherwise be referred to as peak-power sub-carrier spacing and / or Weighted-power sub-carrier spacing).

[0124] Power ratio between y and g: may determine the magnitude of artificial peaks at the sensing eavesdropper. The larger ratio p / q may produce a higher sensing security. The best sensing secrecy may be achieved when q = 0 as p / q goes to infinity, which implies that the magnitude of artificial peaks is same with that of the target peak.

[0125] Figure 3B shows examples 300b of a range of ambiguity functions for various K values when p -Pr / clL and q = 0. The Figure shows plots of Range in meters (as a fraction of the maximum unambiguous range) against normalized magnitude in dB.

[0126] As shown in the Figure, when K - 1 305b, no ambiguity control is applied, and no ambiguous peaks may be generated within themaxrange. The true location of a target object may be the first peak shown at zero range (0m). As peak subcarrier spacing increases for a power allocation, the number of ambiguous peaks may rise to K- 1. As shown in the Figure, the peak subcarrier spacing for K- 431 Ob may produce 3 extra peaks within Rmax, the peak subcarrier spacing K- 8 may produce 7 peaks and K = 16 may produce 15 peaks.

[0127] Furthermore, as described above, the power ratio between y?and ^may affect the peak magnitude of the additional peaks. Figure 3C shows plots with K = 4 and varying peakpowers p. The configuration p = PT K! L and q = 0 may provide the highest peak magnitude, optimizing privacy protection and sensing secrecy.

[0128] As p decreases, peak magnitude also decreases, resulting in reduced sensing security in the ISAC system. As shown in Figure 3C,

[0129]

[0130] = 1 305c produces the highest peak,

[0131]

[0132] followed by — = 0.8310c and then — = 0.5315c.

[0133] PfK PfK

[0134] Thus, the ambiguity control feature may be integrated into ISAC signalling design, balancing trade-offs among radar sensing, communication, and sensing privacy performance.

[0135] Performance Metric for Sensing Privacy

[0136] The sensing security performance, i.e., the performance of privacy protection in the wireless sensing, may be evaluated using sidelobe levels in a sensing eavesdropper’s detection as a metric for sensing privacy. In practical applications, the sidelobe levels in a sensing eavesdropper may not be known; in practice, it may not even be known if there is a sensing eavesdropper present in the network. However, as described below, the sidelobe levels may be estimated, thus providing an estimate for the privacy protection.

[0137] Two types of sidelobe level metrics may be considered. The first sidelobe metric may be the peak sidelobe level (PSL). The PSL may be defined as the largest sidelobe magnitude relative to the main lobe magnitude, the main lobe magnitude corresponding to the target. This metric may show the relative magnitude between the target peak and maximum artificially generated peak, in which the higher PSL may imply the higher sensing security. That is, a higher PSL may indicate to the eavesdropper that another target exists or that the target is in an alternative location, thus enhancing the secrecy of the true target.

[0138] The second sidelobe metric may be the integrated sidelobe level (ISL). The ISL may be defined as the total integrated power of all sidelobes relative to the main lobe power. Since ISL may increase as the number of artificial peaks increases, a higher ISL maybe desirable for an increased secure sensing functionality. That is, a higher ISL may indicate to the eavesdropper that multiple targets exist or that the target may be in a multiplicity of alternative locations, thus enhancing the secrecy of the true target.

[0139] As described above, it may not be possible to calculate the exact PSL and ISL at an Eve, due to, for example, a lack of knowledge about the Eve’s channel. However, a worst-case sensing secrecy (which may be assumed to be equivalent to Eve’s best performance) may be established by evaluating the ambiguity function of the ISAC signals, as shown in Equation 3.

[0140] Letting AE(τ) represent a range ambiguity function, which may be obtained by performing an inverse Fourier transform over x ⊙ x*, the PSL and ISL may be defined as:

[0141] max|AE(τ)|2

[0142] PSLE= 10 log10

[0143] |AE(0)|2

[0144] Equation 7

[0145] ∑τ≠0|AE(τ)|2

[0146] ISLE= 10 log10

[0147]

[0148] |AE(0)|2

[0149] Equation 8

[0150] By applying ambiguity control to x (i.e. applying altered properties to the obtained signal), that is in this example by controlling the ratio of p to q, and K, approximate closed-form expressions for PSL and ISL may be derived as:

[0151] (p - q)2

[0152] PSLE= 10 log10((p + (K - 1)q)2

[0153] Equation 9

[0154] (p - q)2(κ - 1)

[0155] ISLE= 10 log10

[0156]

[0157] (p + (K - l)q)2 /

[0158] Equation 10The above expressions for PSL and ISL may represent worst-case PSL and ISL values. Hence, the actual PSL and ISL observed by the Eve may be less favorable. These metrics may therefore be used as performance indicators for sensing security to guide the design of, in this example, the altered signals.

[0159] While the above equations may be applied for range ambiguity control (that is, introducing “ghost” locations for a target object at an eavesdropper), the equations described herein may be adapted to determine other properties of the target object. For instance, the equations may be adapted for angle estimation, Doppler estimation (velocity), and / or radar imaging. The methods described herein may be adapted to the other estimation cases (e.g. Doppler estimation) by using analogous equations to 5 and 6. The exemplary examples herein, given for the range estimation, may utilize power allocation along the sub-carrier axis, as in the examples the range estimation is performed along subcarrier evaluation. Similarly the Doppler ambiguity may be altered by applying power allocation along symbol axis (equivalent representation may be pulse-to-pulse or slow-time). The principle may follow with the range estimation and may substantially the same (e.g. applying R in Equation 5a and 6b to a symbol-axis / pulse-to-pulse as shown in Equations 5b and 6b).

[0160] ISAC Signalling for Secure Sensing

[0161] The privacy protection method described herein may be integrated with various types / kinds of ISAC signal design in different scenarios.

[0162] As shown in Figures 2A and 2B above, a network, such as an ISAC system, may comprise a single ISAC node, configured for transmitting and receiving, or may comprise multiple ISAC nodes for transmitting and / or receiving. The method described herein may be adapted / extended to signalling with different system setups. Two examples of network design and a method for implementing the privacy protection are described below.

[0163] Single-node ISAC with Single-antenna Transmission:For a single-node scenario with single-antenna transmission, a communication signal may be embedded with random data to form a sensing signal, for example to form the obtained signal described in relation to Figure 1, for the ISAC system. The ISAC node may generate the obtained signal or the obtained signal may be generated externally, for instance by a central unit, and may be transmitted to the ISAC node.

[0164] Unit-amplitude constellations may be utilized for data modulation schemes. An objective of the ISAC signalling for secure sensing may be to design a signal x, in this instance the altered signal, by adjusting the parameters K and p in Equations 5a / 5b, based on for example the required radar sensing, communication, and sensing security performance. Other non-unit amplitude constellations may also be used with the methods described herein. It may be assumed that the legitimate sensing receiver, which in this instance may be the single ISAC node, has prior knowledge of the transmitted ISAC signal.

[0165] Additionally, a condition that q ≠ 0 in the ambiguity control may be imposed which may enable the legitimate receiver to apply reciprocal filtering (compensating subcarrier power allocation) to demodulate the sensing signals and mitigate the impact of ambiguity control.

[0166] Thus, for ISAC performance metrics, an achievable communication rate and the PSL and ISL for radar sensing may be used as follows to perform a method for privacy protection.

[0167] Figure 4 shows a flow chart of steps of an exemplary method 400 for ISAC signal design with the privacy protection (ambiguity control) in a single-node scenario with single-antenna transmission, in accordance with some embodiments. The flow chart shows steps in the case of single-antenna transmission, using a communication signal embedded with random data as the sensing signal for the ISAC system.

[0168] The transmitting apparatus may form part of a 3rdGeneration Partnership Project, 3GPP, communication network and may be a base station or a User Equipment, UE. The altered signal may be used in a 3GPP Integrated Sensing and Communication, ISAC, system. The transmitting apparatus may alternatively be any other suitabletransmitting apparatus and may apply any other suitable standard and / or protocol, such as a WLAN apparatus applying the IEEE standard.

[0169] In a setting step s410, the desired worst-case sensing secrecy levels, PSLE > ePSL and ISLE > elSL may be set. The worst-case sensing secrecy levels may be set according to a desired security level of the system. For instances, the value ePSL may be set to be smaller than 1 (which may correspond to 0 dB), and elSL may be set smaller than ePSL*(L-1).

[0170] In a computing step s420, the power weights p and q may be computed, along with the peak subcarrier spacing K satisfying the worst case sensing secrecy. The values of p, and K may be computed using, for example, Equations 6, 9 and 10 above.

[0171] The parameters p, q and K are examples of the altered properties which may be calculated such that, when an altered signal is obtained by applying the altered properties to the obtained signal, artifacts are introduced into the altered signal relative to the obtained signal.

[0172] In an allocating step s430, the subcarrier powers may be allocated to x (e.g., the obtained signal) based on the obtained parameters p, q, and the peak subcarrier spacing K in the computing step above.

[0173] These steps are also summarized in Algorithm 1 below. After designing the altered signal x, the legitimate sensing performance PSLLand ISLLand the communication rate may be evaluated. The communication rate may be calculated as

[0174] hcHRhc

[0175] C0= B ∑(l=1)Llog2(1 + hcHRhc / σc2)

[0176] σc2

[0177] Equation 11

[0178] where hcis the communication channel, and B is the bandwidth of the OFDM signal.Algorithm 1 ISAC signal design with range ambiguity control for single-antenna transmission.

[0179] Input: Communication data, Worst-case sensing secrecy (εPSLand εISL) Output: ISAC signal with ambiguity control, x

[0180] 1: Modulate random communication data into OFDM signal x

[0181] 2: Compute an integer κ satisfying κ ≥ 10(ε - ε) / 10+ 1

[0182] 3: Compute power weights p and q based on (6) and (9) such that PSLE≥ εPSL4: Allocate subcarrier powers to x as in (5)

[0183] Thus, a minimum change to the obtained signal may be to alter the power of the different subcarriers of the OFDM signal; in doing so, introducing false peaks in the ambiguity function for a sensing eavesdropper which may not have prior knowledge of the power variation pattern in the subcarriers.

[0184] Figures 5A-5D show block diagrams for apparatuses which may be used to perform the privacy protection in accordance with the single node system described above.

[0185] Figure 5A shows a transmitting apparatus 500a for transmitting the altered signal. The transmitting apparatus may be, for example, an ISAC transmitter. The ISAC transmitter may be configured with ambiguity control 505a. That is, the transmitting apparatus may be configured to obtain a signal for transmitting and calculate altered properties to introduce artifacts into the signal. Thus, the transmitting apparatus may generate an altered signal and may transmit the altered signal.

[0186] As shown in Figure 5A, the transmitting apparatus may receive and / or generate communication data 510a. The communication data may be data for communicating between the transmitting apparatus and another apparatus in the network. For example, the transmitting apparatus may be the ISAC transmitter and the communication data may be transmitted to a User Equipment. In another example, the transmitting equipment may be the User Equipment.The communication data may be modulated. That is modulation 515a of the communication data may be applied to obtain (potentially generate) a signal for transmission by the transmitting apparatus. The modulation may be applied to modulate the communication data into an OFDM signal (as described in algorithm 1 above). As described herein, the communication data may be modulated into other suitable signals such as OFDM, OTDM, OTFS, OCDM, and / or OTSM.

[0187] Subcarrier power allocation 515a may then be performed using the ambiguity control 505a, to compute altered properties of the obtained signal such that, when an altered signal is obtained by applying the altered properties to the obtained signal, artifacts are introduced into the altered signal relative to the obtained signal.

[0188] The transmitting apparatus may further comprise a transmitting antenna 520a which is configured to transmit the altered signal. The transmitting antenna may be referred to as a transmitter. In another example, the transmitting apparatus may comprise a transceiver for transmitting the altered signal. In an example with a single-node ISAC with single-antenna transmission, as indicated, the transmitting apparatus may comprise a single antenna for transmitting the altered signal.

[0189] As described above, the transmitting apparatus may form part of a 3rdGeneration Partnership Project, 3GPP, communication network and may be a base station or a User Equipment, UE. In such an instance, the altered signal may be used in a 3GPP Integrated Sensing and Communication, ISAC, system.

[0190] In another example, the transmitting apparatus may be configured to use the Institute of Electrical and Electronics Engineers, IEEE, 802.11 standard. The transmitting apparatus may be a wireless local area network, WLAN, access point or a WLAN User Equipment, UE. The WLAN UE may be, for example, a Wi-Fi enabled device.

[0191] In yet another example, the transmitting apparatus may be a RADAR transmitter. That is, the transmitting device may form a stand-alone sensing device (and therefore may not perform communication with the same obtained signal). The obtained signal in this example may be a pulsed signal. The altered signal may be a pulsed signal.The transmitting apparatus may comprise a storage medium, such as a memory, for storing information / data, and a controller, such as a processor, for carrying out steps of the methods described herein. An example of the transmitting apparatus comprising the memory and controller is described in relation to Figure 12 below.

[0192] Figure 5B shows an example sensing apparatus 500b for receiving the transmitted altered signal. The sensing apparatus may be integrated within the transmitting apparatus. That is, the transmitting apparatus may be configured for transmitting the altered signal and for receiving the reflected altered signal. The transmitting apparatus may be configured for transmitting and receiving in the example with a single ISAC node.

[0193] In another example the sensing apparatus may be at least one receiving apparatus which receives the reflected signal. The receiving apparatus may receive the reflected signal and may communicate the altered properties of the obtained signal to at least one receiving apparatus. That is, the reflected signal may be received by a receiving apparatus and may be communicated to other receiving apparatus.

[0194] As described above, the transmitting apparatus may transmit the altered signal. The altered signal may reflect from a target and may be received by the sensing apparatus. The sensing apparatus may comprise a receiver antenna (RX antenna 505b) configured to receive the reflected altered signal. In an instance with the transmitting apparatus being configured to receive the reflected signal, the transmitting apparatus may be configured with a transmitter and a receiver and / or may be configured with a transceiver for transmitting and receiving signals.

[0195] The sensing apparatus may be configured to estimate, using the altered properties of the transmitted altered signal and the reflected signal, one or more properties of the target. The sensing apparatus may apply reciprocal filtering 51 Ob using the transmitted signal with ambiguity control 515b as a reference. Additionally or alternatively, the sensing apparatus may apply matched filtering using the altered signal as a reference. Other methods may be used for estimating the one or more properties of the target. There are many other, and for example potentially more advanced radar receiver technologies, such as multiple signal classification (MUSIC), estimation of signalparameters via rotational invariant techniques (ESPRIT), compressed sensing and others which may be used with the methods described herein.

[0196] As shown in the Figure, an example of the one or more properties of the target may be target detection 520b. For instance, the one or more properties may comprise at least one of: target presence; target location; target size, target shape, target physical classification; target velocity; and imaging information. The one or more properties are examples of properties which may be determined through RADAR sensing. In an example, the target may be a vehicle and / or other road infrastructure user. The methods described herein may provide and improve traffic monitoring. In another example, the methods may additionally or alternatively be used to image and / or map an environment, and / or monitor environmental conditions.

[0197] Furthermore, in an example where the target is a human or animal or living being, the one or more properties of the target may further comprise at least one of: heart rate; breathing rate; behavioural recognition; and fall detection. The properties of the human / animal may be determined based on micro-doppler sensing. The behavioural recognition may include, for example, gesture control. Thus, the methods described herein may detect human / animal presence, density, location, behaviour and / or health status.

[0198] The methods described herein may be deployed, for example, using a WLAN network in a building, such as a house, office or factory. The methods may therefore be deployed to detect properties of a human or animal within the building. Furthermore, with the onset of 6G and potential high frequency signals with high bandwidth, the methods may also be applied in open spaces in a 6G network with high accuracy. As described above, the method may be deployed in a sensing only configuration, in which case the transmitting apparatus and sensing apparatuses may be configured for sensing only (and not for communication in a network which also uses a communication signal for sensing).

[0199] The transmitting apparatus and the receiving apparatus may be comprised within an information processing system for providing privacy protection in wireless sensing and may perform the steps of the methods described herein.Figure 5C shows a communication apparatus 500c for communication with the transmitting apparatus. The communication apparatus may be, for example, a user equipment configured to communicate with the transmitting apparatus. The UE may communicate wirelessly with the transmitting apparatus to transfer and receive data. For instance, the transmitting apparatus may be an ISAC node and the communication apparatus may be a UE, or any other suitable apparatus, for communicating with the node in a telecommunications network. Equally, the UE may be the transmitting apparatus, and the ISAC node may be the communication apparatus, for example.

[0200] The transmitting apparatus and communication apparatus may use the same signal type for communication as the signal type for sensing. That is, if an OFDM signal is used for sensing, an OFDM signal may also be used for communication. In fact, the same signal may be used for sensing and communication. The same signal may be transmitted by the transmitting apparatus for both communication and sensing. The communication signal may be randomised and modulated for transmitting as the sensing signal. The methods described herein may be applied to signal types other than communication signals. For instance, sensing may be performed using data-payload signals (as have been described herein) and / or reference signals and / or channel estimation signals. Each of these signals may typically be found in communication frames. Other signals typically used in communication frames may also be used with the methods described herein.

[0201] As shown in the Figure, the communication apparatus may comprise a receiver (an RX antenna 505x) for receiving the communication signal. Additionally or alternatively, the communication apparatus may comprise a transceiver. The communication apparatus may receive the communication signal and perform demodulation 510. Demodulation may be performed according to an assigned protocol. By way of example, in a 5G network, a demodulation reference signal (DM-RS) may be used as a UE-specific reference signal for the UE to estimate the radio channel conditions for coherent (intelligent) data demodulation.

[0202] Once the communication signal has been demodulated the communication apparatus may generate an estimated communication data 515c for the received signal.Figure 5D shows an example schematic for a sensing eavesdropper 500d which may be configured for unauthorized sensing. The sensing eavesdropper may be any suitable device for receiving signals and performing signal computation. For instance, the sensing eavesdropper may be any suitable device with a processor and memory such as a computer, laptop or mobile phone, or with a dedicated RADAR or ISAC processor and memory. The sensing eavesdropper may comprise a receiver (RX antennas) for receiving the sensing signal. Figures 2A and 2B show example configuration of the sensing eavesdropper configured for wireless sensing.

[0203] As shown in Figures 2A and 2B, the sensing eavesdropper may be configured with a line-of-sight view of the transmitting apparatus (shown as the ISAC node in Figure 2A and ISAC node 1 in Figure 2B). The eavesdropper may receive the sensing signal (denoted as reference signal 51 Od in Figure 5D) from the transmitting apparatus. As the eavesdropper is in line-of-sight of the transmitting apparatus, the eavesdropper may assume that the reference signal has minimal noise and may therefore use the reference signal as a sensing signal.

[0204] The eavesdropper may additionally receive a surveillance signal 515d. The surveillance signal may be the sensing signal which has reflected from a target and is received by the eavesdropper. The surveillance signal is denoted as YESin Figures 2A and 2B. As with usual radar type systems, the Eavesdropper may then use a matched filter 520d, with the reference signal set as the filter, for target detection 525d. In a system without the privacy protection described herein, the eavesdropper may therefore resolve the properties of the target, for instance the target’s location. However, if the sensing signal is altered using the methods described herein, the eavesdropper may fail to resolve the properties of the target as the altered signal may cause the eavesdropper to detect multiple target locations or ‘ghost targets’ within range. An example of the failed target detection of the eavesdropper due to the modified signal is shown in Figure 6 below. Thus, the methods described herein may not prevent a sensing eavesdropper from obtaining the altered signals but instead introduces enough ambiguity to prevent the eavesdropper from being able to accurately derive target properties as described above.Figure 6 shows example Range-Doppler maps 600 of resolved targets from altered signals using the method described herein. In particular Figure 6 shows numerical simulations of Range-Doppler maps with secure sensing ISAC transmission in a single-node ISAC with single antenna (Algorithm 1). In this example, a target is positioned at 1000m distance with zero-Doppler shift (i.e., the target is stationary). Design parameters / rand / for the ambiguity control are determined with respect to the required sensing secrecy ePSL and elSL.

[0205] The x-axis of each graph shows the doppler shift, in Hertz Hz, for the resolved target signal. In this example, as the doppler shift caused by the target is zero (i.e., it may be assumed the target is stationary), each resolved signal is shown centred with 0 Hz doppler shift with a small spread in frequency. The Y axis of each graph shows the range, or distance, of the target from the transmitting apparatus. While in this example, a property of the target which is determined is range, the method may equally be implemented to determine at least one of target presence (range and / or angle); target location; target size; target shape; target physical classification (that is, type of target: human, animal type, vehicle type, and so on); target velocity; and imaging information. The target physical classification may be based on the physical shape of the target. The sensing may also apply a micro-Doppler technique to determine further properties of the target.

[0206] A first column 605 shows the Range-Doppler map at a legitimate receiver, for example, at the sensing apparatus described in Figure 5B above. In this example, with a single node, the transmitting apparatus and sensing apparatus may be comprised in a single apparatus. The transmitting apparatus may comprise a single antenna for transmission and / or a single antenna for reception. A second column 615 shows the Range-Doppler map at a sensing eavesdropper, for example the sensing eavesdropper described in relation to Figure 5D above.

[0207] The Range-Doppler maps show the results of following algorithm 1 and the method described in relation to Figure 4. Each of a first 606, second 608 and third 610 row show a different privacy protection / worst case sensing secrecy. As described in relation to Figure 4, values for elSL and ePSL may first be set based on the desired privacy protection level. Values for K and the ratio of p and q may then be setaccordingly. In this instance, a normalized value of p is used, denoted by p, which refers to pL / PtK).

[0208] Figures 7A - 7C show examples of performance plots for communication, legitimate sensing and eavesdropper sensing, for different values of p and K. In particular, the Figures show performance of an ISAC signal design with ambiguity control in the case of single-node ISAC with single-antenna transmission. Figure 7A shows a plot for communication rate, Figure 7B shows a plot for PSLz and ISLz, and Figure 7C shows a plot for PSLz- and ISLz-. As described above, the normalized p in the graphs refers to pL / (Pt K).

[0209] Figure 7A is a graph 700a of normalized power against communication rate for various peak sub-carrier spacings. In particular, the graphs show plots for K = 8, 16 and 32. In this example, the communication rate may be measured between an ISAC node, acting as a transmitting apparatus, and a communication apparatus such as a UE. As show in the graph, as the normalised power for each of the peak sub-carrier spacings is increased, the communication rate decreases. Furthermore, as shown, as the peak sub-carrier spacing is increased, the communication rate decreases.

[0210] Figure 7B shows a graph 700b of normalised power against sidelobe level for various peak sidelobe levels and integrated sidelobe level at a legitimate receiver (e.g., at a sensing apparatus as described in relation to Figure 5B). In this example, the transmitting apparatus and sensing apparatus may both be comprised within a single ISAC node. That is, the ISAC node may be configured for transmission and reception of communication data. The graphs show the PSL and ISL with increasing normalized power, for various peak sub-carrier spacings.

[0211] As shown in the graph, as the normalized power is increased, for each peak subcarrierspacing, both the PSL and ISL increase, which is indicative of improved privacy protection. Furthermore, as shown in the graph, for each normalized power, the larger peak sub-carrier spacing has a higher sidelobe level, also indicative of improved privacy protection.Figure 7C shows a graph 700c of normalised power against sidelobe level for various peak sidelobe levels and integrated sidelobe level at a sensing eavesdropper (e.g., at a sensing eavesdropper apparatus as described in relation to Figure 5D).

[0212] Similarly for the legitimate sensing apparatus, as shown in the graph, as the normalized power level is increased, the sidelobe for ISL and PSL at the sensing Eavesdropper increases. As described above, while in a practical application the ISL and PSL of an eavesdropper may not be known, the graphs in Figures 7B and 7C show that the estimated sidelobe levels for PSL and ISL at the legitimate receiver are worse case estimates and the actual PSL and ISL observed by the sensing Eavesdropper may be less favorable.

[0213] The simulations in Figures 7A-7C reveal a potential trade-off between communication and sensing (in this instance ISAC performance) and privacy protection (sensing secrecy). This indicates that, for example, enhancing the security / privacy protection of an ISAC system may lead to a potential reduction in both sensing and communication performance. However, an advantage is improved privacy protection. Thus, a balance may be made between the privacy protection and communication ability, and this may be explicitly designed by selecting q, p and K.

[0214] The above description in relation to Figures 4 to 7C provides an exemplary example of a method for privacy protection using a transmitting apparatus for altering a signal, receiving a reflected altered signal and estimating, using the altered properties of the transmitted altered signal and the reflected signal, one or more properties of the target. In particular, the above example is provided in relation to a single node ISAC with single antenna transmission.

[0215] In another exemplary example, the method of privacy protection may be performed with a Distributed ISAC System with Multi-antenna Transmission. An example of such as system is provided in relation to Figure 2B and is described in detail below. For instance, in a distributed system, a plurality of transmitting apparatuses may be used to transmit the altered signal. Further, at least one receiving apparatus may receive the reflected signal.Distributed ISAC System with Multi-antenna Transmission

[0216] Figure 8 shows a flow chart of steps of another exemplary method 800 for ISAC signal design with privacy protection (ambiguity control) in a Distributed ISAC System with Multi-antenna Transmission. In particular, Figure 8 presents an example using sensing with multiple nodes / devices, using weighted summation of multi-user communication and multi-input multi-output (MIMO) radar signals as the ISAC transmit signal.

[0217] In a setting step s810, as with the single ISAC system, the worst-case sensing secrecy may be set according to values of e / SL and ePSL.

[0218] In a computing step s820, again similar to the single ISAC system, peak sub-carrier spacing, K, may be computed for the ISAC subcarriers.

[0219] In another setting step S830, a communication signal-to-interference-plus-noise ratio (SINR) for each communication user may be set as a constraint for communication performance.

[0220] In a design step s840, ISAC signals for transmission by the distributed ISAC System may be designed by optimizing a Cramer-Rao Bound (CRB). That is, an obtained signal may be altered using calculated altered properties. More details of the steps of the above method are provided below and in relation to Algorithm 2.

[0221] In a distributed ISAC system with multi-antenna transmission, a weighted summation of multi-user communication and multi-input multi-output (MIMO) (RADAR) signals may be used as the (ISAC) transmit signal (i.e., as the altered signal). Block diagrams of an ISAC transmitter and distributed legitimate sensing receivers are shown in Figures 9Aand 9B below.

[0222] In this exemplary example, N distributed nodes may cooperatively serve an ISAC function, with each node equipped with Mt transmit antennas. Using the frequencydomain representation of OFDM signals, the transmitted signal of a single OFDM symbol at node n may be expressed as:Equation 12

[0223] where Xc,n= \Nc nSc, with Wc,n e cMtXUand Sc e CUxLrepresent the precoding matrix and the desired data symbols for multi-user communication, respectively. Here, Xr,n e cMf XLrepresents a MIMO (radar) sensing signal for multi-target sensing. As described below, the communication precoding matrix \Ncnand the MIMO radar signal Xr,n may be designed to achieve optimal radar sensing, communication, and privacy protection (sensing security performance).

[0224] For secure sensing, ambiguity control, e.g., the altered properties of an obtained signal, may be incorporated by constraining the subcarrier power of the sensing signal with q- 0 in Equation 5a and / or similarly for pulse-to-pulse allocation in equation 5b. That is, the altered properties of the obtained signal may be calculated based on an ambiguity control Equations 5a / 5b. The altered properties may introduce artifacts (e.g., artificial imperfections and / or artificial noise) in the Ambiguity Function of the ISAC signal. The artificial imperfections may be modelled as additional peaks on a delta function, which may result in multiple target locations and / or “ghost” targets at a sensing eavesdropper.

[0225] The subcarrier power p, with periodicity K, may be allocated to the sensing signals to balance the trade-off between sensing and communication performance. This may ensure that the sensing eavesdropper’s PSL is close to or higher than 0 dB, as derived in Equation 9. Meanwhile, the distributed legitimate sensing receivers may mitigate the increased sidelobe levels caused by the altered properties (ambiguity control) in the legitimate radar sensing. Additionally or alternatively, if target locations are known from an initial target search phase, the ambiguity control’s adverse effects may be (further) reduced.

[0226] For a sensing performance metric, the Cramer-Rao Bound (CRB) for target localization may be used. The CRB may serve as a lower bound for target localization accuracy (e.g., a lower bound of estimation performance). Additionally, signal-to-interference-plus-noise ratio (SINR) for each communication user may be adopted asa communication performance metric. Based on the desired sensing secrecy levels PSLr and ISLr, the ISAC peak subcarrier spacing K may be computed using Equations 9 and 10.

[0227] The following optimization problem for secure distributed ISAC signaling may be solved as follows:

[0228] Minimize

[0229] ^c,n^r,n,p tr ([F(0) j’1)'

[0230] Equation 13a

[0231] subject to yc,u > Tc, Vit,

[0232] Equation 13b

[0233] [Rn]m,m=

[0234] Equation 13c

[0235] [p i — (P> if I = n + Kt

[0236] L r,n,ijm m(Q otherwise

[0237] Equation 13d

[0238] KPT

[0239]

[0240] P~ —

[0241] Equation 13e

[0242] where F(0) is the Fisher information matrix,c,u is the SINR of a communication user zz, and rcis an SINR threshold. R» is the covariance matrix of X and Rr^z is the covariance matrix of the / hcolumn vector of Xr,«.

[0243] The above optimization problem may aim to minimize the localization CRB (13a), while ensuring at least a minimum SINR for all communication users (13b) and satisfyingper-antenna power constraints (13c). That is, it may be ensured that communication users meet or exceed a minimum (or threshold) SINR value. Constraints (13d) and (13e) handle the subcarrier power allocation for privacy protection. To solve this problem, the problem may be ‘relaxed’ to a convex problem using semi-definite relaxation (SDR) and then solved using a convex optimization tool (by way of example, CVX, as discussed at https: / / cvxr.com / cvx / as of 8 January 2024). The steps for implementing the above method are shown the flow chart in Figure 8 and are similarly summarized in Algorithm 2 below.

[0244] Algorithm 2 ISAC signal design with ambiguity control for distributed ISAC Input: Communication SINR threshold (C), Worst-case sensing secrecy (e^sz and zsz)

[0245] Output: Communication precoder W^, MIMO radar signals

[0246]

[0247] 1: Compute an integer K satisfying K > o^£lSL~ePSL^10+ 1

[0248] 2: Set per-antenna power, ISAC subcarrier power, and communication SINR constraints

[0249] 3: Using CVX to calculate solutions of (13)

[0250] Figure 9A shows an example of a transmitting apparatus 900a for transmitting the altered signal (denoted as Radar signal in the Figure) and communication data. The transmitting apparatus may be, for example, an ISAC transmitter and may be used in, for example, a network of distributed ISAC nodes with multi-antenna transmission.

[0251] The transmitting apparatus may be used to communicate with, for example, a UE. The transmitting apparatus may obtain and / or generate communication data 905a. The communication data may be modulated (using modulation 910a). The modulation may be applied to modulate the communication data into an OFDM signal, for instance if the communication is in a telecommunications network using 5G and / or 6G and / or WLAN. The signal may be modulated into other signal types with appropriate portions. That is, while the methods disclosed herein have been described within the context of an orthogonal frequency division multiplexing (OFDM)-based ISAC system, the methods are not limited to any specific waveformand may be readily adapted to other ISAC waveforms and other sensing waveforms. For instance, the method may be used with signals such as: a frequency division multiplexed, FDM, signal and the plurality of portions may be a plurality of frequency sub-bands; or the obtained signal may be a time division multiplexed, TDM, signal and the plurality of portions may be a plurality of time-slots; or the obtained signal may be a delay-Doppler or time-frequency-space multiplexed, TFS, signal and the plurality of portions may be a plurality of delay-Doppler bins; or the obtained signal may be a chirp division multiplexed, CDM, signal and the plurality of portions may be a plurality of chirps; or the obtained signal may be a time-sequency division multiplexed, TSM, signal and the plurality of portions may be a plurality of time-sequency bins. In any case the signals may be orthogonal signals, e.g., OFDM, OTDM, OTFS, OCDM, OTSM, etc., signals and may be used in single or distributed network systems.

[0252] The communication data may be processed by a precoder 915a. The communication data may be pre-coded by the precoder. Precoding may be used as a signal processing technique in MIMO systems so that multiple streams are transmitted from transmit antennas (920a) with independent and appropriate weighting per antenna such that the throughput is maximized at a receiver output.

[0253] As shown in the Figure, the transmitting apparatus may additionally generate and / or obtain a radar signal 925a (i.e., the altered signal). The radar signal may be processed with sub-carrier allocation 930a and ambiguity control 935a, according to, for example, algorithm 2 and / or the method steps in Figure 8. That is, the radar signal may be obtained and altered properties may be determined such that when an altered signal is obtained by applying the altered properties to the obtained signal, artifacts are introduced into the altered signal relative to the obtained signal.

[0254] As shown in the Figure, the transmitting apparatus may further comprise transmitting antennas 920a which are configured to transmit the pre-coded communication signal and the altered radar signal. The transmitting antennas may be referred to as transmitters. In another example, the transmitting apparatus may comprise transceivers for transmitting the signals.An ISAC network may encompass multiple levels of resource sharing, from low level (colocation of equipment) to high level (using the same signals for communication and sensing). As may be understood from the disclosure herein, the methods for privacy protection may be applicable to any level of resource sharing. Furthermore, the methods may also be applicable to RADAR only solutions.

[0255] Figure 9B shows sensing apparatuses 901b-903b for receiving the transmitted altered signal. In an example, one or more ISAC transmitters may transmit the altered signal, and a reflected altered signal may be received by each of the sensing apparatuses, which may be for example ISAC nodes. One of the sensing apparatuses may be integrated within the transmission apparatus. That is, the transmitting apparatus may be configured for transmitting the altered signal and for receiving the altered signal.

[0256] As described above, the transmitting apparatus may transmit the altered signal. The altered signal may reflect from a target and may be received by the sensing apparatuses. Each of the sensing apparatuses may comprise a receiver antenna (denoted as RX antenna for each node in the Figure) configured for receiving the reflected altered signal. The RX antennas may be comprised within a transceiver. In an instance with the transmitting apparatus being configured to also receive the reflected signal, the transmitting apparatus may be configured with a transmitter and a receiver and / or may be configured with a transceiver for transmitting and receiving signals.

[0257] The sensing apparatuses may be configured to estimate, using the altered properties of the transmitted altered signal and the reflected signal, one or more properties of the target. The sensing apparatus may apply reciprocal filtering 51 Ob using the transmitted signal with ambiguity control 515b as a reference. As shown in the Figure, a maximum likelihood estimator 905b may be used to estimate one or more of the properties of a target for target detection 910b. The maximum likelihood estimator may be a receiver processing that maximizes a cost function (likelihood function) for target estimation. For example, denoting the target position as [x,y], the maximum likelihood estimation may becomes [x,y] = arg max(x,y) (cost function determined by (x,y)).The maximum likelihood estimation may be performed by a central unit. For example, the central processing unit shown in Figure 2B. The central unit may be in communication with the sensing apparatuses and may receive the reflected signals detected at each of the sensing apparatuses. The central unit may then perform the maximum likelihood estimation to determine one or more properties of the target. The estimation may be performed by at least one of the receiving apparatuses. An example of an apparatus which may perform the estimation is shown in Figure 13.

[0258] In this example, configurations of a communication device and a sensing eavesdropper may be the same, or substantially the same, as the communication device and sensing eavesdropper as described in relation to Figures 5C and 5D.

[0259] Figure 10A shows exemplary target localization plots 1000a based on secure sensing / privacy protection ISAC transmission with two distributed ISAC nodes. In this example, algorithm 2 was used with the worst-case sensing secrecy set as epsi - OdB and eisi -11.7dB.

[0260] The graphs show x coordinates, in meters, on the x axis and y coordinates, in meters, on the y-axis. In this example, a target object was located at [0,0], two ISAC nodes were located at [-50, -50] and [50, -50], respectively, and a sensing eavesdropper was located at [50,50],

[0261] A first column 1005a in the Figure shows a localization of a target using the distributed ISAC system. A second column shows the attempted localization of the target using the sensing eavesdropper.

[0262] Each row in the Figure shows the localization graphs for different signal to interference plus noise ratios (SINR) for a communication signal (i.e., the altered signal). Figure 10B shows beam patterns (which may be generated by, for example, beamforming) for each of the SINR ratios.

[0263] A first row 1006a corresponds to OdB SINR. Figure 10B shows in the first column of the first row a high intensity in a location corresponding to the target for the D-ISAC. In contrast, the graph in the second column of the first row, belonging to the sensingeavesdropper, shows multiple false locations with high intensities. Hence, the sensing eavesdropper may not be able to resolve the true location of the target.

[0264] A second row 1008a shows plots for a SINR of 18dB. As shown in Figure 10B, the 18dB SINR may result in two prominent signal lobes, one pointing in a user communication device direction and one for target detection. As shown in the second row of Figure 10A, in the first column effective target detection may still be performed by the distributed ISAC system. However, the eavesdropper signal may contain even more ghost target locations.

[0265] A third row 1010a in Figure 10A shows an SINR of 21 dB. This may correspond to a further improved communication rate, however may reduce the sensing accuracy. As shown in the first column the distributed system may no longer be able to resolve the properties (in this instance location) of the target. Hence, the SINR ratio may be adjusted accordingly so that communication may be performed between the transmitting apparatus and a communication device and properties of the target may be resolved by the distributed system but may not be easily resolved by the sensing eavesdropper. In this exemplary example, with the above worst-case sensing secrecy settings, 18dB may be the most effective SINR for combined communication and sensing tasks. The SINR may depend on various factors including but not limited to the system used, the sensing parameters, and communication rate requirements for example.

[0266] Figures 11A-11C show exemplary performance plots for ISAC signal design with ambiguity control in the case of distributed ISAC.

[0267] Figure 11 A shows a plot 1100a of Peak sidelobe level, in decibels, against communication SINR, in decibels. The graph shows plots for both the distributed ISAC system and a sensing eavesdropper. The term "w / o RAC" in the plot refers to "without range ambiguity control".

[0268] In line with the design constraint that q = 0 for sensing subcarriers, the sensing eavesdropper’s PSL is close to or above 0 dB for each peak subcarrier spacing andSINR. This indicates that the eavesdropper may not be able to accurately determine the target location due to artificial targets generated by the secure ISAC signaling.

[0269] Figure 11 B shows a plot 1100b of integrated sidelobe against communication SINR for the distributed ISAC system and an eavesdropper. As shown in the Figure the eavesdropper’s ISL, which may correspond to the number of artificial targets, increases as the peak subcarrier spacing, K, increases. However, this increase in privacy protection may come at the expense of legitimate sensing performance in the distributed ISAC system, as both PSL and ISL for legitimate sensing may also increase.

[0270] Figure 11 C shows a plot 1100c of localization Root Cramer-Rao Bound (RCRB) for the legitimate receiver, in meters, against communication SINR. The plots indicate a direct trade-off between the sensing and communication performance, shown for various values of the peak subcarrier spacing, κ and for the case without range ambiguity control, i.e. without privacy protection. Figure 11 C shows a small decrease of the RCRB and the RCRB vs SINR trade-off, as the peak subcarrier spacing, K, increases, to improve privacy protection.

[0271] Unlike the single-antenna transmission design described above, in a distributed system, a higher communication performance may support increased privacy protection (sensing security). This is because a higher communication performance may allow the sensing signal (the altered signal) to have lower power p, meaning less signal power is directed toward the sensing target. That is, in a multi-antenna system, the altered signal may be degraded further as there may be multiple pickup locations to compensate for degradation of original signal (degradation here being the introduction of additional false peaks through the altered properties of the signal). In this instance the multiple systems could be for example a single transmitter-multiple receiver, or multiple transmitter-receivers

[0272] The methods described herein introduce methods which may introduce ambiguity for target detection at an eavesdropper while still allowing a legitimate ISAC system to accurately detect and estimate target properties / information. In an orthogonal frequency division multiplexing (OFDM) system this may be achieved by usingfrequency-interleaved subcarriers — some for ISAC functionality and others for communication. As described above, other alterations may be made to signals such as pulse-to-pulse allocations. These setups may generate multiple artificial (ghost) peaks in the eavesdropper's sensing results, making it difficult to pinpoint true properties, e.g., target range. On the other hand, the legitimate receiver may avoid this ambiguity by utilizing one or more of the following:

[0273] 1 ) Prior knowledge of the target's location.

[0274] 2) Deployment of distributed ISAC systems.

[0275] 3) Exploitation of reciprocal filtering to avoid ambiguity.

[0276] In an example where the receiver has prior knowledge of the target's location, the accuracy / precision of tracking the target may be further improved.

[0277] Figure 12 shows an example transmitting apparatus 1200 for performing steps of the method described herein. The example transmitting apparatus may correspond to the transmitting apparatuses described in relation to Figures 5A and / or 9A. The transmitting apparatus may be configured to carry out the method steps described above with respect to Figures 1, 4 and 8 accordingly. The transmitting apparatus may comprise an antenna 1202 and transmitter (Tx) / receiver (Rx) units 1204 (or alternatively transceiver units) for transmitting and receiving, amplifying and digitizing signals / information, for example for transmitting the altered signal and receiving a reflected signal. While 1 antenna is shown in the Figure, any suitable number of antennas and RX / TX units may be present, for example the antennas may be used in a MIMO array as described above.

[0278] The transmitting apparatus may further comprise a storage medium 1208, such as a memory, for storing information / data, and a controller 1206, such as a processor, for carrying out method steps / operations that the transmitting apparatus performs.

[0279] The controller may execute instructions stored as a computer program in the storage medium carry out operations / method steps. The transmitting apparatus may beconsidered to correspond to the ISAC node shown in Figure 2A and / or any of ISAC nodes 1-2 as shown in Figure 2B.

[0280] The transmitting apparatus may correspond to an ISAC node in a communication network. The transmitting apparatus may correspond to an eNB, gNB, UE, etc. Thus, the transmitting apparatus may form part of a 3rdGeneration Partnership Project, 3GPP, communication network and may be a base station or a User Equipment, UE. For instance, the methods described herein may conform to 3GPP TS 38.901. TS 38.901 release 18 addresses a study on channel model for frequencies from 0.5 to 100 GHz. In particular, TS 38.901 captures the findings of a study item, " Study on channel model for frequency spectrum above 6 GHz" and from further findings of a study item, " Study on New Radio Access Technology" and a study item " Study on Channel Modeling for Indoor Industrial Scenarios". The channel models in the TS document address the frequency range 0.5-100 GHz. The document helps TSG RAN WG1 to properly model and evaluate the performance of physical layer techniques using the appropriate channel model(s). The document relates to the 3GPP evaluation methodology and covers the modelling of the physical layer of both Mobile Equipment and Access Network of 3GPP systems. The document is intended to capture the channel model(s) for frequencies from 0.5GHz up to 100GHz. Additionally or alternatively, the methods described herein may conform to 3GPP TSG SA, TR 22.837 “Feasibility Study on Integrated Sensing and Communication”. _ Alternatively, the transmitting apparatus may be a wireless local area network, WLAN, access point or a WLAN User Equipment, UE. The transmitting apparatus may be configured to use the Institute of Electrical and Electronics Engineers, IEEE, 802.11 standard. In particular, the transmitting apparatus may use the IEEE, 802.11 bf standard which addresses ISAC integration in WLANs.

[0281] The methods described herein may apply to other communication types such as those set by European Telecommunications Standards Institute, ETSI.

[0282] The transmitting apparatus may be comprised within an information processing system for providing privacy protection in wireless sensing. The information processing system may comprise the transmitting apparatus and a receivingapparatus. The information processing system may be configured to perform the steps of the methods described herein.

[0283] Figure 13 shows a block diagram of an information processing apparatus 1300 or a computing device 1300, such as a data storage server which may be used to implement some or all the operations of the methods described herein and perform some or all of the tasks of apparatus of an embodiment. The computing device 1300 may be used to implement any of the method steps described above, e.g. any of steps S10-S60 and / or S410 - S430 and / or S810-S840 for example.

[0284] The computing device 1300 comprises a processor 1303 and memory 1304. Optionally, the computing device also includes a network interface 1307 for communication with other such computing devices. Optionally, the computing device also includes one or more input mechanisms such as keyboard and mouse 1306, and a display unit such as one or more monitors 1305. These elements may facilitate user interaction. The components are connectable to one another via a bus 1302.

[0285] The memory 1304 may include a computer readable medium, which term may refer to a single medium or multiple media (e.g., a centralized or distributed database and / or associated caches and servers) configured to carry computer-executable instructions. Computer-executable instructions may include, for example, instructions and data accessible by and causing a computer (e.g., one or more processors) to perform one or more functions or operations. For example, the computer-executable instructions may include those instructions for implementing a method disclosed herein, or any method steps disclosed herein, for example any of steps S10-S60. Thus, the term “computer-readable storage medium” may also include any medium that is capable of storing, encoding or carrying a set of instructions for execution by the machine and that cause the machine to perform any one or more of the method steps of the present disclosure. The term “computer-readable storage medium” may accordingly be taken to include, but not be limited to, solid-state memories, optical media and magnetic media. By way of example, and not limitation, such computer-readable media may include non-transitory computer-readable storage media, including Random Access Memory (RAM), Read-Only Memory (ROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Compact Disc Read-Only Memory (CD-ROM) orother optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory devices (e.g., solid state memory devices).

[0286] The processor 1303 is configured to control the computing device and execute processing operations, for example executing computer program code stored in the memory 1304 to implement any of the method steps described herein. The memory 1304 stores data being read and written by the processor 1303 and may store at least one altered signal and / or reflected signal and / or reference signal and / or reciprocal filter and / or matched filter and / or maximum likelihood estimator and / or algorithm (e.g. algorithm 1 and / or 2) and / or other data, described above, and / or programs for executing any of the method steps described above. These entities may be in the form of code blocks which are called when required and executed in a processor.

[0287] As referred to herein, a processor may include one or more general-purpose processing devices such as a microprocessor, central processing unit, or the like. The processor may include a complex instruction set computing (CISC) microprocessor, reduced instruction set computing (RISC) microprocessor, very long instruction word (VLIW) microprocessor, or a processor implementing other instruction sets or processors implementing a combination of instruction sets. The processor may also include one or more special-purpose processing devices such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), a software defined radio (SDR), network processor, or the like. In one or more embodiments, a processor is configured to execute instructions for performing the operations and operations discussed herein. The processor 1303 may be considered to comprise any of the units, or modules, described above. Any operations described as being implemented by a unit may be implemented as a method by a computer and e.g. by the processor 1303.

[0288] The display unit 1305 may display a representation of data stored and / or generated by the computing device, such as range-doppler maps, localization maps and / or any of the graphs disclosed herein (for example shown in Figures 3, 6, 7A-7C, 10, and 11A-11C), and / or GUI windows (e.g. for displaying the generated graphs) and / or interactive representations enabling a user to interact with the apparatus 1300 by e.g. selection interaction, input text boxes, and / or any other output such as an option toview a specific graph, and may also display a cursor and dialog boxes and screens enabling interaction between a user and the programs and data stored on the computing device. The input mechanisms 1306 may enable a user to input data and instructions to the computing device.

[0289] The network interface (network l / F) 1307 may be connected to a network, such as the Internet, and is connectable to other such computing devices via the network. The network l / F 1307 may control data input / output from / to other apparatus via the network. Other peripheral devices such as microphone, speakers, printer, power supply unit, fan, case, scanner, trackerball etc may be included in the computing device.

[0290] Methods described herein may be carried out on a computing device / apparatus 1300 such as that illustrated in Figure 13. Such a computing device need not have every component illustrated in Figure 13 and may be composed of a subset of those components. For example, the apparatus 1300 may comprise the processor 1303 and the memory 1304 connected to the processor 1303. Or the apparatus 1300 may comprise the processor 1303, the memory 1304 connected to the processor 1303, and the display 1305. The apparatus may further comprise a transceiver, transmitter, receiver and / or antenna(s), as described herein. The methods described herein may be carried out by a single computing device in communication with one or more data storage servers via a network. The computing device may be a data storage itself storing at least a portion of the data.

[0291] The methods described herein may be carried out by a plurality of computing devices operating in cooperation with one another. One or more of the plurality of computing devices may be a data storage server storing at least a portion of the data.

[0292] The methods described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. The methods described herein may be implemented as a computer program or computer program product, i.e., a computer program tangibly embodied in a non-transitory information carrier, e.g., in a machine-readable storage device, or in a propagated signal, forA computer program may be in the form of a stand-alone program, a computer program portion or more than one computer program and may be written in any form of programming language, including compiled or interpreted languages, and it may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a data processing environment. A computer program may be deployed to be executed on one module or on multiple modules at one site or distributed across multiple sites and interconnected by a communication network.

[0293] The methods described herein may be performed by one or more programmable processors executing a computer program to perform functions of the methods by operating on input data and generating output. Apparatus performing the methods may be implemented as programmed hardware or as special purpose logic circuitry, including e.g., an FPGA (field programmable gate array) or a SDR (software defined radio) or an ASIC (application-specific integrated circuit).

[0294] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random-access memory or both. The essential elements of a computer are a processor for executing instructions coupled to one or more memory devices for storing instructions and data.

[0295] The above-described embodiments may advantageously be used independently of any other of the embodiments or in any feasible combination with one or more others of the embodiments.

Claims

Claims1. A method for privacy protection in wireless sensing, the method comprising;obtaining a signal for transmission by a transmitting apparatus; dividing the obtained signal into a plurality of portions;calculating altered properties of the obtained signal such that, when an altered signal is obtained by applying the altered properties to the obtained signal, artifacts are introduced into the altered signal relative to the obtained signal;transmitting, by the transmitting apparatus, the altered signal; receiving a reflected signal that is a reflection of the transmitted altered signal from a target;estimating, using the altered properties of the transmitted altered signal and the reflected signal, one or more properties of the target.

2. The method of claim 1, wherein the altered properties comprise alterations to the configured power levels of at least one of the plurality of portions, such that the altered signal comprises portions having a higher power level, p, and portions having a lower power level, q, wherein the lower power level is lower than the higher power level.

3. The method of claim 2, wherein the lower power level portions and higher power level portions are interleaved.

4. The method of any of claims 2 and 3 wherein the lower power level portions and higher power level portions define a repeating pattern.

5. The method of any of claims 1 to 4, wherein:the obtained signal is a frequency division multiplexed, FDM, signal and the plurality of portions are a plurality of frequency sub-bands; or the obtained signal is a time division multiplexed, TDM, signal and the plurality of portions are a plurality of time-slots; or the obtained signal is a delay-Doppler or time-frequency-space multiplexed, TFS, signal and the plurality of portions are a plurality of delay-Doppler bins; or theobtained signal is a chirp division multiplexed, CDM, signal and the plurality of portions are a plurality of chirps; or the obtained signal is a time-sequency division multiplexed, TSM, signal and the plurality of portions are a plurality of time-sequency bins.

6. The method according to any of claims 1- 4, wherein the obtained signal is divided by transmission time to obtain the plurality of portions.

7. The method of any of claims 1 to 6, wherein the transmitting apparatus forms part of a 3rdGeneration Partnership Project, 3GPP, communication network and is a base station or a User Equipment, UE.

8. The method of claim 7, wherein the altered signal is used in a 3GPP Integrated Sensing and Communication, ISAC, system.

9. The method of any of claims 1 to 6, wherein the transmitting apparatus is configured to use the Institute of Electrical and Electronics Engineers, IEEE, 802.11 standard and is a wireless local area network, WLAN, access point or a WLAN User Equipment, UE.

10. The method of any of claims 1 to 6, wherein the obtained signal is a pulsed signal and the transmitting apparatus is a radar transmitter.

11. The method of any preceding claim, wherein the transmitting apparatus receives the reflected signal.

12. The method of any preceding claim, wherein a plurality of transmitting apparatuses is used to transmit the altered signal.

13. The method of any preceding claim, wherein at least one receiving apparatus receives the reflected signal.

14. The method of claim 13, further comprising communicating the altered properties of the obtained signal to at least one receiving apparatus.

15. The method of any preceding claim, wherein the one or more properties comprise at least one of:target presence;target location;target size;target shape;target physical classification;target velocity; andimaging information.

16. The method of claim 15, wherein the target is a human or animal and wherein the one or more properties further comprise at least one of:heart rate;breathing rate;behavioural recognition; andfall detection.

17. An information processing system for providing privacy protection in wireless sensing, the information processing system comprising a transmitting apparatus and a receiving apparatus, wherein the transmitting apparatus comprises a memory and a processor connected to the memory, wherein the processor is configured to:obtain a signal for transmission by the transmitting apparatus; divide the obtained signal into a plurality of portions;calculate altered properties of the obtained signal such that, when an altered signal is obtained by applying the altered properties to the obtained signal, artifacts are introduced into the altered signal relative to the obtained signal; andinstruct the transmitting apparatus to transmit the altered signal; and wherein the receiving apparatus is configured to:receive a reflected signal that is a reflection of the transmitted altered signal from a target;estimate, using the altered properties of the transmitted altered signal and the reflected signal, one or more properties of the target.

18. The system of claim 17, wherein the transmitting apparatus and the receiving apparatus are co-located, or wherein the transmitting apparatus is separate from the receiving apparatus.

19. The system of any of claims 17 - 18, wherein a plurality of transmitting apparatuses are configured to transmit the altered signal.

20. The system of any of claims 17 -19, wherein a plurality of receiving apparatuses are configured to receive the reflected signal.

21. The system of any of claims 17-20, wherein at least one transmitting apparatus is further configured to communicate the altered properties of the obtained signal to at least one receiving apparatus.

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