Switched array for sensing with reduced number of transmitter chains

Abstract

Systems and methods are disclosed for switched array sensing signal transmission using a reduced number of transmitter chains. In one embodiment, a wireless transmitter comprises delay circuitry configured to provide a plurality of sensing signals (s0(t), s1(t),..., sN-1(t)) having different delays (τ 0 , τ 1 ,..., τ N-1 ), wherein each sensing signal (si(t)), for i= 0,1,..., N - 1, is time-limited to a respective time interval of τ = τ i to τ = τ i + T, where T is a predefined time duration. The wireless transmitter further comprises circuitry configured to provide the plurality of sensing signals (s0(t), s1(t),..., sN-1(t)) having different delays (τ 0 , τ 1 ,..., τ N-1 ), respectively, to a plurality of antennas. In this manner, the wireless transmitter is enabled to support virtual transmit beamforming, despite having fewer transmitter chains than antennas, which in turn enables improved sensing via improved target illumination. Embodiments of method performed by a wireless transmitter as well as embodiments of a wireless receiver and methods of operation thereof are also disclosed.

Description

[0001]SWITCHED ARRAY FOR SENSING WITH REDUCED NUMBER OF TRANSMITTER CHAINS Technical Field The present disclosure relates to integrated sensing and communication in a wireless communication system. Background Transmitter Antenna Switching a 3rdGeneration Partnership Project (3GPP) 5thGeneration (5G) system, a User Equipment (UE) often have multiple antennas for Multiple-Input Multiple-Output (MIMO) communication. While the UE has one receiver chain for each antenna, it often only has one transmitter chain that is shared among all antennas. The reason is to reduce hardware size and cost at the UE as well as power consumption. To obtain the channel state information at the New Radio (NR) base station (i.e., the gNodeB (gNB)) for downlink (DL) transmissions and to be able to select the antenna branch for uplink (UL) transmission, the UE transmits Sounding Reference Signal (SRS) from each antenna by a SRS transmitter (Tx) switch that allows the UE to connect the transmit chain to a specific antenna and control it, one at a time. Figure 1 illustrates SRS transmit antenna switching with single transmit and four receive antenna switching (T1R4). As shown, four receiver (Rx) ports are connected to four antennas, respectively. One transmitter (Tx) port is connected to the antennas via an SRS Tx switch. Integrated Sensing and Communication Integrated Sensing And Communication (ISAC) is emerging as a promising use case in future wireless cellular communications such as the 6thGeneration (6G) system. The principal idea is to use cellular communication nodes (i.e., base stations or UEs) to sense the environment by either using communication-specific signals or dedicated sensing signals and provide information such as location, shape, speed, etc. of sensed objects in the surrounding. Some of the possible applications of sensing using cellular communication systems are traffic monitoring, drone detection, gesture and motion detection, presence detection of objects or persons, vital sign detection, environment mapping, particle and pollution detection, etc. Sensing can be done either using a single node, i.e. the transmitter and receiver are co- located (monostatic), or multiple nodes, i.e. the transmitter and receiver(s) are in different locations (bistatic and multistatic). These two sensing topologies are described in the following two sub- sections, followed by a short introduction to conventional radar processing. Monostatic Radar: In a monostatic radar, the transmitter and receiver nodes are collocated, often in the same node. The transmitter sends a waveform that is reflected by the environment and sensing targets. These reflections are received by the receiver and processed, e.g. by the receiver or another connected entity, to obtain information about the environment and sensing targets. A radar pulse that spans one or multiple Orthogonal Frequency Division Multiplexing (OFDM) symbols would allow an easy integration of radar into the communication system. For example, for NR 30 kilohertz (kHz) numerology, the OFDM symbol duration, including cyclic prefix, is approximately 36 microseconds (^s). A radar pulse spanning a single OFDM symbol duration would have the same length. A round trip time of 36 ^s corresponds to single-way distance of 5.4 kilometers (km). For objects closer than 5.4 km, the echo would arrive while the transmitter still transmits the radar pulse, see Figure 2. The reflected signal must be received in the presence of strong self-interference (i.e., the transmitted signal that leaks into the receiver). A receiver having this capability is often called a full-duplex capable receiver. Full-duplex puts high requirements on the receiver and potentially also on the transmitter (e.g., linearity), especially for high transmit powers where high self-interference cancellation is required. Bistatic and Multistatic Radar: In bistatic radar, the transmitter and receiver are not collocated and thus avoid problems outlined above for monostatic radar. Distance measurements are based on measuring the Time of Flight (ToF) from the transmitter (BS1) via the sensing target to the receiver (BS2), see Figure 3. All possible target positions for a measured ToF value are located on an ellipsis (in 3D: ellipsoid) with focal points given by transmitter and receiver location. To determine the target position, the transmitter and receiver node location, ToF, and Angle of Departure (AoD) or Angle of Arrival (AoA) must be known. One of the angles is needed to determine the target location on the ellipse given by transmitter and receiver location and ToF. In order to accurately determine ToF, the transmitter and receiver need to be accurately synchronized in time. This is one of the main challenges for bistatic and multistatic radar. In multistatic radar, more than two nodes participate in the radar operation. For example, with one transmitter and three receivers three ellipses can be determined and the target is located where the three ellipses intersect each other. This method requires ToF estimates but angle information is not needed ( can however be used to improve performance). Radar Processing: The sensing receiver performs radar processing to estimate range and / or Doppler shift of the target. In case the receiver has multiple antennas, it can also estimate the direction in which the target is located. To estimate range, Doppler shift and direction to the target, the sensing receiver correlates the received signal with delayed and frequency shifted versions of the known transmitted signal. The result of this correlation is a delay—Doppler profile. Note that in some application only range or Doppler might be sufficient. To estimate the direction of the target, the delay—Doppler of the different antennas are correlated with the steering vector of the array for different values of the incidence angle. The result of this correlation is a radar cube, which is illustrated in Figure 4. The target, if illuminated properly, creates a “peak” in the radar cube at the values corresponding to its range, Doppler shift, and direction. Here, in this multi-dimensional function, a “peak” is a point in the function where the modulus of the function has a distinct maximum. An estimate of the range, Doppler shift and direction can thus be obtained by identifying where in the radar cube the peak that corresponds to the target is located. Transmit Beamforming: To illuminate only the target (ideally), or only a small area (practically), to avoid getting multiple peaks in the radar cube, the transmitter can use beamforming. Beamforming is the use of multiple transmit antennas to direct the signal power inside a cone with limited width by weighting the signal at individual antennas with precoding weights. If only the target is present inside this cone, only one peak is created in the radar cube. If multiple objects (clutter and / or multiple targets) are present, each of these objects create a peak, and effort needs to be spent on figuring out which peak belongs to the desired target. Since transmit beamforming limits the width of the cone, and thus the number of objects that are illuminated, transmit beamforming is a valuable tool for sensing to reduce clutter. Transmit beamforming also focuses the transmitted signal power, and thus improves the link budget and the received signal quality (i.e., Signal-to-Noise Ratio (SNR)), which makes sensing less sensitive to thermal noise and the sensing results more accurate. Summary Systems and methods are disclosed for switched array sensing signal transmission using a reduced number of transmitter chains. In one embodiment, a wireless transmitter comprises delay circuitry configured to provide a plurality of sensing signals (s0(t), s1(t), …, sN-1(t)) having differentdelays (^^^, ^^^, … , ^^ேି^), wherein each sensing signal (si(t)), for ^^ ൌ 0,1, … ,^^ െ 1, is time-limitedto a respective time interval of ^^ ൌ ^^^ to ^^ ൌ ^^^ ^ ^^, where ^^ is a predefined time duration. Thewireless further comprises circuitry configured to provide the plurality of sensingsignals (s0(t), s1(t), …, sN-1(t)) having different delays (^^^, ^^^, … , ^^ேି^), respectively, to a pluralityof antennas. In this manner, the wireless transmitter is enabled to do virtual transmit beamforming, despite having fewer transmitter chains than antennas. This virtual beamforming enables improved sensing via improved target illumination (i.e., reduced clutter illumination). In one embodiment, the circuitry comprises summing circuitry configured to combine the plurality of sensing signals to provide a combined sensing signal and switching circuitry configured to receive the combined sensing signal and output the combined sensing signal to the plurality of antennas such that, for each time interval of ^^ ൌ ^^^ to ^^ ൌ ^^^ ^ ^^ for ^^ ൌ 0,1, … ,^^ െ 1, thecombined sensing signal is output to an i-th antenna of the plurality of antennas. In one embodiment, the wireless transmitter further comprises a precoder configured to receive an initial sensing signal and apply a plurality of different precoding weights or filters to the initial sensing signal to thereby provide a plurality of precoded signals, respectively, wherein the delay circuitry is configured to apply the different delays (^^^, ^^^, … , ^^ேି^) to the plurality ofprecoded signals, respectively, to thereby provide the plurality of sensing signals (s0(t), s1(t), …, sN-1(t)). In one embodiment, the plurality of different precoding correspond to a desired beamform. In one embodiment, the predefined time duration ^^ is less than ^^^ െ ^^^ି^ for all values of^^ ൌ 1, … ,^^ െ 1.In one embodiment, the wireless transmitter is comprised in a first node configured indicative of at least one of the different delays (^^^, ^^^, … , ^^ேି^) to asecond wireless node. In one embodiment, the second wireless node is a network node in a radio access network of a cellular communications system. In one embodiment, the node is a wireless communication device. Embodiments of a method performed by a wireless transmitter are also disclosed. In one embodiment, a method performed by a wireless transmitter comprises providing a plurality of sensing signals (s0(t), s1(t), …, sN-1(t)) having different delays (^^^, ^^^, … , ^^ேି^), wherein eachsensing signal (si(t)), for ^^ ൌ 0,1, … ,^^ െ 1, is time-limited to a respective time interval of ^^ ൌ ^^^to ^^ ൌ ^^^ ^ ^^, where ^^ is a predefined time duration. The method providing theplurality of sensing signals (s0(t), s1(t), …, sN-1(t)) having different delays (^^^, ^^^, … , ^^ேି^) to aplurality of antennas, respectively. In this manner, virtual transmit beamforming is enabled for wireless sensing. Embodiments of a wireless receiver are also disclosed. In one embodiment, a wireless receiver comprises delay circuitry configured to apply a plurality of different delays (^^^ െ ^^^, ^^^ െ^^^, … , ^^^ െ ^^ேି^) to a sensing signal received via an antenna of the wireless receiver to provide aplurality of received sensing signals that are time-aligned, wherein ^^^is a constant value greater or equal to ^^ேି^. In one embodiment, the wireless receiver further comprises combiner circuitry configured to sum the plurality of received sensing signals to provide a combined sensing signal. In one embodiment, the wireless receiver further comprises combiner circuitry configured to combine the plurality of received sensing using a plurality of precoding weights or filters, respectively, to provide a combined, beamformed sensing signal. In one embodiment, a sensing signal component of each received sensing signal is time-limited to a respective time interval having a time duration of ^^ ^ ^^, where ^^ is a delay spread ofa channel between the wireless receiver and a corresponding wireless transmitter and ^^ is a predefined time duration. In one embodiment, the predefined time duration ^^ is less than ^^^െ^^^ି^ for all values of ^^ ൌ 1, … ,^^ െ 1.In one embodiment, the wireless receiver is comprised in a second to receive, from a first wireless node, information indicative of different delays (^^^, ^^^, … , ^^ேି^)used by a transmitter. In one embodiment, the wireless receiver is comprised in a second wireless node configured to receive, from the first wireless node, information indicative weights or filters used by the transmitter. In one embodiment, the second wireless node is a network node in a radio access network of a cellular communications system. In one embodiment, the first wireless node is a wireless communication device. In one embodiment, the wireless receiver comprises a plurality of antennas and the delay circuitry is first delay circuitry from a plurality of delay circuitries coupled to a first antenna from the plurality of antennas. In one embodiment, the wireless receiver further comprises at least oneadditional delay circuitry configured to apply a plurality of different delays (^^^ െ ^^^, ^^^ െ ^^^,… , ^^^ െ ^^ேି^) to an additional sensing signal received via an additional antenna of the wirelessreceiver to provide an additional plurality of received sensing signals that are time-aligned. embodiment, the wireless receiver further comprises first combiner circuitry configured to sum or combine the plurality of received sensing signals output by the first delay circuitry to provide a first combined sensing signal, at least one additional combiner circuitry configured to sum or combine the plurality of received sensing signals output by the at least one additional delay circuitry to provide at least one additional combined sensing signal, and further combiner circuitry configured to sum or combine the first combined sensing signal and the at least one additional combined sensing signal to provide an output sensing signal. Corresponding embodiments of a method performed by a wireless receiver are also disclosed. In one embodiment, a method performed by a wireless receiver comprises receiving a sensing signal via an antenna of the wireless receiver and applying a plurality of different delays(^^^ െ ^^^, ^^^ െ ^^^, … , ^^^ െ ^^ேି^) to the sensing signal received via the antenna of the wirelessreceiver to provide a plurality of received sensing signals that are time-aligned. Brief Description of the Drawings The accompanying drawing figures incorporated in and forming a part of this specification disclosure, and together with the description serve to explain the principles of the disclosure. Figure 1 illustrates Sounding Reference Signal (SRS) transmit antenna switching with single transmit and four receive antenna switching; Figure 2 illustrates an example of self-interface in monostatic full-duplex based sensing; Figure 3 illustrates an example of bistatic sensing; Figure 4 illustrates a sensing or radar cube; Figure 5 illustrates one example of a transmitter for transmission of a sensing signal for virtual transmit (Tx) beamforming, in accordance with embodiments of the present disclosure; Figure 6 illustrates one example of a receiver for reception of a sensing signal using virtual Tx beamforming, in accordance with embodiments of the present disclosure; Figure 7 illustrates one example of the signals involved in the transmission of sensing signal using virtual Tx beamforming, in accordance with embodiments of the present disclosure; Figure 8 is a flow chart that illustrates the operation of a transmitter for transmission of a sensing signal for virtual Tx beamforming, in accordance with embodiments of the present disclosure; Figure 9 is a flow chart that illustrates the operation of a receiver for reception of a sensing signal using virtual Tx beamforming, in accordance with embodiments of the present disclosure; Figure 10 illustrates one example of a signaling mechanism between first and second wireless nodes related to virtual Tx beamforming, in accordance with embodiments of the present disclosure; and Figure 11 illustrates another example of a receiver for reception of a sensing signal using virtual Tx beamforming using multiple Rx antennas, in accordance with embodiments of the present disclosure. Detailed Description The embodiments set forth below represent information to enable those skilled in the art to and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure. Certain challenges exist with existing sensing technology. If a User Equipment (UE) with only one transmit chain is going to act as a sensing transmitter, it cannot perform transmit beamforming. Without beamforming, the number of objects that are illuminated by the transmitted signal (i.e., the clutter) cannot be reduced, and angle of departure cannot be estimated. Systems and methods are disclosed that address the aforementioned and / or other challenges. Embodiments of the present disclosure enable a UE to create a virtual transmitter array by using a transmit antenna switch to transmit individual signals on each of multiple transmitter antennas, each with a known delay and optionally each precoded with a beamforming weight. Virtual beamforming is accomplished by enabling a receiver to combine the signals received from the different antennas in a way that takes the known, different delays into account. Embodiments of the present disclosure allow a wireless sensing system to use (virtual) transmitter beamforming even if the transmitter only has one transmitter chain. Embodiments of the present disclosure can also be extended to a general case where the transmitter has fewer transmitter chains than the number of antennas, i.e., the transmitter has NTx transmitter chains and NAntantennas, where NTx< NAntand NTxis a positive integer greater than or equal to 1. Embodiments related to signaling of the different delays of the transmit signals transmitted via the virtual transmitter array are also disclosed. In one embodiment, the transmitter signals information indicative of the different delays to the receiver. Embodiments of the present disclosure may provide advantages over existing technology. Embodiments of the present disclosure enable a wireless sensing system that uses a UE as the sensing transmitter to do virtual transmit beamforming, despite having NTx< NAnttransmitter chains (e.g., NTx=1 transmitter chains and NAnt > 1 antennas). This virtual beamforming maintains the benefit of real beamforming with respect to a narrower beam (after receiver processing) and thus reduced clutter illumination. However, contrary to real beamforming, it does not improve the link budget. Therefore, embodiments of the present disclosure provide benefits to sensing (where less clutter illumination is important) but not communication (where the improved link budget would be important). Figure 5 illustrates a transmitter 500 for transmitting sensing signals via a virtual antenna array, in accordance with an embodiment of the present disclosure. As illustrated, the transmitter 500 includes an optional precoder 502, delays 504-0 to 504-3, circuitry 505 optionally including summing circuitry 506 and a Tx switch 508, and antennas 510-0 to 510-3. The circuitry 505 can be any circuitry for coupling the outputs of the delays 504-0 to 504-3 to the respective antennas 510-0 to 510-3. While the summing circuitry 506 and Tx switch 508 are used in the example embodiments described herein, the circuitry 505 is not limited thereto. For example, a multi-input port Tx switch may have inputs coupled to the outputs of the delays 504-0 to 504-3 and outputs coupled to the antennas 510-0 to 510-3 and controlled or otherwise configured to connect the any input to any output. Note that example embodiment of Figure 5 assumes a single Tx chain and four antennas 510-0 to 510-3; however, the transmitter 500 may have a single Tx chain and any number of two or more antennas or, more generally, NTx transmitter chains and NAnt antennas, where NTx < NAntand NTxis a positive integer greater than or equal to 1. It should also be noted that the transmitter 500 may include further components that are not illustrated for clarity and ease of discussion. For example, the transmitter 500 may include a single Tx chain including components such as, e.g., digital-to-analog converter (DAC), filter(s), mixers / upconverters, amplifier, etc., where this Tx chain may be implemented between the summing circuitry 506 and the Tx switch 508, as an example. As discussed below, a sensing signal s(t) is optionally precoded by the precoder 502. The delays 504-0 to 504-3 apply different delays ^0to ^3, respectively, to the sensing signal s(t) or alternatively to the different precoded signals output by the precoder 502. Note that while there are four delays 504-0 to 504-3 and four antennas 510-0 to 510-3 in the example of Figure 5, there may be any number of two or more delays 504 and two or more antennas 510. The resulting delayed (precoded) sensing signals are routed by the circuitry 505 to the respective antennas 510- 0 to 510-3. For example, using the summing circuitry 506 and the Tx switch 508, the delayed (precoded) sensing signals are summed by the summing circuitry 506 to provide a combined sensing signal. The combined sensing signal, including the different delayed (precoded) sensing signals, is provided to the Tx switch 508 (possibly after passing through a Tx chain), and the Tx switch 508 outputs the combined signal to the different antennas 510-0 to 510-3 in a switching manner (i.e., switchably outputs the combined signal to the different antennas 510-0 to 50-3). In particular, the Tx switch 508 outputs the combined signal to the different antenna s 510-0 to 510-3 such that, for each time interval of ^^ ൌ ^^^^ to ^^ ൌ ^^^^ ^ ^^ for ^^ ൌ ^^,^^, … ,^^^^^^^^ െ ^^ (where in theillustrated example NAnt = 4), the combined sensing signal is output to an i-th antenna 510-i. ^^ is a predefined time duration. Figure 6 illustrates a receiver 600 for receiving (reflected) sensing signals via a virtual antenna array, in accordance with an embodiment of the present disclosure. In this example, thereceiver 600 includes delays 602-0 to 602-3 that apply the different delays ^^^^ െ ^^^^, ^^^^ െ ^^^^, ^^^^ െ^^^^,^^^^^^ ^^^^ െ ^^^^ , respectively, to a signal received via an antenna 604 to thereby providerespective Rx signals (Rx0 to Rx3), where ^^^^is a constant value, e.g., a predefined or predetermined constant that is greater than or equal to ^^^^^^^^^^ି^^. The receiver 600 optionally includes a combiner 606 that combines the Rx signals to provide combined Rx signal. The Rx signals (Rx0 to Rx3) or the combined Rx signal are then processed to sense a sensing target(s). Note that, while not illustrated for clarity and ease of discussion, the receiver 600 may include further components that are not illustrated in Figure 6. For example, the receiver 600 may include multiple Rx chains (e.g., 4 in the illustrated example) between the outputs of the delays 602-0 to 602-3 and the inputs of the combiner 606. These Rx chains may include conventional Rx circuitry such as, e.g., filters, mixers / down-converters, analog to digital converter (ADC), or the like. In embodiments of the present disclosure, the effect of transmit beamforming with respect to improved target illumination (i.e., reduced clutter illumination) in sensing can be accomplished in two ways: either through precoding at the transmitter 500 using the precoder 502 or through combining at the receiver 600 using the combiner 606. If transmit beamforming is provided via precoding at the transmitter 500, the precoder 502 applies precoding to a sensing signal s(t) in a manner similar to regular transmit beamforming for concurrent multiantenna transmission. If transmit beamforming is provided via combining at the receiver 600, the combiner 606 performs combining of the time-aligned receive signals provided by the delays 602-0 to 602-3 in a manner similar to precoding, just done on the receiver side instead of the transmitter side, which is only possible in this consecutive multiantenna transmission. As stated earlier, the combining at receiver 600 is only equivalent to true transmit beamforming with respect to clutter illumination but not with respect to link budget improvement. Further details regarding the precoding at the transmitter 500 and the combining at the receiver 600 are provided below after a discussion of other parts of the present disclosure. Figure 7 illustrates an example embodiment of the sensing signal s(t) transmitted by the transmitter 500 and the time-aligned receive signals (rx0 signal, rx1 signal, etc.) output by the delays 602-0 to 602-3 at the receiver 600. Note that an arbitrary clock offset ^^^^has been included in the description to indicate that the receiver 600 might not know the absolute delays perfectly, due to for example imperfect synchronization between the transmitter 500 and the receiver 600 or due to the propagation time from the transmitter 500 to the receiver 600 and to make the filter causal (i.e., to avoid a negative delay). In Figure 7, original sensing signal s(t) is shown in in the first row, where the switching times are also shown as vertical densely dotted lines. In operation, the transmitter 500 transmits different delayed versions of the sensing signal s(t), where the sensing signal that has a time duration T, i.e., it is time-limited to an interval from t=0 to t=T. In other words, the sensing signal is non-zero in the interval from t=0 to t=T and otherwise zero or approximately zero (i.e., in reality, a signal may not be truly at zero but be at a level that is understood to be zero). If precoding is done at the transmitter 500 via the precoder 502, precoding is applied to the sensing s(t) to create one signal for each antenna 510. If receiver side combining is done instead, the signal s(t) is instead just copied to create one copy of the sensing signal s(t) for each antenna 510. These signals are delayed, via the delays 504, by different delays τ₀ < τ₁ <…, where the difference between the delays is larger than the time duration T, i.e. T < τ ^ – τ^₋₁ for all i. By adding up these delayed signals via the combiner 506, a bursty signal is created that is zero just before the time instants τ₀, τ₁, … At these time instants, the transmit antenna switch 508 switches between the different antennas 510, i.e., at τ₀, antenna 510-0 is selected, at τ₁ antenna 510-1 is selected, etc. In one embodiment, the time duration ^^ coincides with an Orthogonal Frequency Division Multiplexing (OFDM) symbol duration including the cyclic prefix (CP). If the antenna switchingis very fast, this switching may happen within a fraction of the CP, in this case ^^^^ ൌ ^^^^, or moregenerally ^^^^ ൌ ^^^^ is an integer multiple of ^^. This would allow transmissions in consecutiveOFDM symbols. Note that, in 3rdGeneration Partnership Project (3GPP) New Radio (NR) (andlikely 6th Generation (6G)), the CP structure is slightly irregular, therefore, ^^^^ ൌ ^^^^ may bemodified to align the switching time instants with symbol boundaries and to account for the time- varying CP. If link budget permits, the time duration ^^ can also be shorter than an OFDM symbol duration; in this case multiple transmit antennas can transmit within one OFDM symbol duration. At the receiver 600, the received sensing signal (i.e., the desired sensing signal component of the received signals which also contain, e.g., interference and noise) has the same time duration T as the transmitted sensing signal plus delay spread ^^, where ^^ is the delay spread of the channel. Delay-spread is the difference in delay of the two taps with the largest and smallest delays. The delay-spread is therefore a measure of how much longer time-duration a signal has after it has travelled over the channel. If the delay-spread is d and the transmit signal is time limited to an interval of width T, the received signal is time limited to an interval of width T+d, where d can be small compared to T. Specifically, a desired sensing signal component of each received sensingsignal (from each Rx antenna) is time-limited to a respective time interval of ^^ ൌ ^^^^ ^ ^^ to ^^ ൌ^^^^ ^ ^^ ^ ^^ ^ ^^, where ^^ is a delay of a first channel tap, ^^ ^ ^^ is a delay of a last channel tap, ^^is a delay spread of a channel between the receiver 600 and the transmitter 500, and ^^ is the predefined time duration discussed above. Note that while the same duration T is used at the receiver side in the embodiments described herein, the receiver 600 may use a shorter duration T’<T of the desired sensing signal component of the received signal but where no significant part of the desired sensing signal component is outside of that duration of time. Conversely, a time duration T’’ > T may be used to compensate for the delay spread of the channel, e.g., when the delay spread is significant. In another embodiment, if the delay spread of the channel is large, the parameter T should also account for the spread, i.e. T should be the time duration of the individual sensing signal pulse plus a constant compensates for the delay spread of the channel. The delays 602 at the receiver 600 delay the signals received in the intervals delimited by the time instants τi+1 - τ^ so that the delays applied at the transmitter 500 are reversed and the signals align in time. If the transmitter 500 did not do precoding, the signals of the different time intervals are combined in a way similar to what would have been done in regular transmit precoding (w.r.t. target illumination), and the combined signal is the output of the receiver 600. If the transmitter 500 did precoding, the signals are, in one embodiment, added together and the sum is the output of the receiver 600. Alternatively, if the transmitter 500 did precoding, the signals may be weighted (e.g., with receive beamforming weights) and summed, and the resulting combined signal is the output of the receiver 600. The output of this receiver 600 will be equivalent with respect to clutter illumination to a signal that has undergone regular transmit beamforming. The whole transmission, i.e., from the transmission from the first antenna 510-0 to the transmission from the last antenna 510-3, must take place in a time interval whose duration is sufficiently short that the environment can be viewed as static during that interval. The target should thus not have moved a significant distance in that interval. The “significant distance” is here taken to mean that the distance travelled must be only a fraction of a wavelength. At 3 Gigahertz (GHz), a wavelength is 10 centimeters (cm), and it would take approximately 3 milliseconds (ms) to travel that distance at 30 meters per second (m / s). That means that the complete transmission cycle must be finished in a time much shorter than 3ms for the antenna switching to be transparent to the sensing process. Since an OFDM symbol at 30 kilohertz (kHz) subcarrier spacing is approximately 30 microseconds (μs) long, and assuming the switching time is 100 nanoseconds (ns), one could fit approximately 10 OFDM symbols and switches into 0.3 ms (which is much shorter than 3 ms). In this example, it is therefore safe to assume that the whole transmission cycle can be made within a time duration over which the channel can be considered static. Note that the switching time in a 5thGeneration (5G) User Equipment (UE) has to be shorter than a guard period set in 3GPP Technical Specification (TS) 38.214 (see, e.g., V18.2.0), Table 6.2.1.2-1. For 30kHz subcarrier spacing, the guard period is one OFDM symbol long, i.e., approximately 30μs long. Since this is an upper bound on the switching time, actual switching times might be faster, like in the example above. If a sensing system should support sensing of both slow and fast moving targets, the virtual beamforming might only be applied in scans for slow moving targets. The decision to enable virtual transmit beamforming can therefore depend on the velocity of the expected targets. For example, if the velocity of the expected targets is less than a threshold velocity, then virtual beamforming as described herein may be used; otherwise, it used. Note that the receiver 600 might be part of the same device or node as the transmitter 500. The system is then a monostatic sensing system. While there are challenges to implementing monostatic sensing using communication hardware, e.g. self-interference, full-duplex etc., embodiments of the present disclosure could be applied in a monostatic system too. Regarding the use of either transmit precoding or receiver combining, note that, in a conventional transmit precoding system, where all antennas transmit concurrently, the transmitted signal would be precoded (same as “beamformed” in this context). Linear precoding is done by weighting the transmitted signal differently for different antennas. For example, if the signal s(t) is precoded, the signal s^(t) = w^ s(t) is transmitted from antenna i, where w^ is the complex weight of transmit antenna i. In full generality, the weighting can also be a filter. The transmit signal of antenna i is then s^(t) = (w^(τ) ⋆ s(τ))(t), where ⋆ denotes convolution and w^(τ) is the impulse response of the precoding weight of antenna i. The proposed system can be implemented in analogy to this, where the signal is precoded in the same way as in the regular system, but the signal of each antenna is instead transmitted one after another, as described above. The advantage of this implementation is that it can be done more like a direct replacement of the regular system in a device where only one antenna can be active at the same time. The proposed system could also be implemented without the precoding at the transmitter 500, where instead the “precoding” would be done at the receiver 600. In this case, in the combiner 606, the received signals from the delays 602 are weighted in the same way as the signals at the transmitter in the regular system would have been weighted, and the weighted signals are then summed to provide the output signal. When the precoding is done at the receiver 600, it is referred to herein as combining rather than precoding, since the prefix “pre” would be misleading. This feature, that the precoding / combining can be done at the receiver 600 instead of at the transmitter 500, lends itself to the possibility to do transmit beam sweeping without using more transmissions than the proposed system requires (one transmission per antenna). If the transmitter 500 decides the transmit beamforming weights (as the transmitter does in classical transmit beamforming), these weights are conveyed to the receiver 600, resulting in additional overhead. Here, it is again important to note that the single-transmit beamforming with combining at the receiver 600 is equivalent to “true” transmit beamforming only with respect to clutter illumination but not link budget gains. Figure 8 is a flow chart that illustrates the operation of the transmitter 500, in accordance with embodiments of the present disclosure. steps are represented by dashed boxes. As illustrated, the transmitter 500 provides sensing signals (s0(t), s1(t), …, sN-1(t)) having differentdelays (^^^^, ^^^^, … , ^^^^ି^^) (step 800). Each sensing signal si(t), for ^^ ൌ ^^,^^, … ,^^െ ^^, is time-limited to (e.g., non-zero during) a respective time interval of ^^ ൌ ^^^^ to ^^ ൌ ^^^^ ^ ^^ (e.g., non-zero interval of ^^ ൌ ^^^^ to ^^ ൌ ^^^^ ^ ^^ and otherwise zero or approximatelyzero), where ^^ is a predefined time duration. In some embodiments, denoted in Figure 8 as “Option A”, precoding is performed at the transmitter 500. More specifically, in order to generate thesensing signals (s0(t), s1(t), …, sN-1(t)) having different delays (^^^^, ^^^^, … , ^^^^ି^^), the precoder 502applies precoding weights or filters to an initial sensing signal (s(t)) to provide a precoded sensingsignal for each antenna 510 (step 800A-1). The delays (^^^^, ^^^^, … , ^^^^ି^^) are applied to theprecoded sensing signals, respectively, to thereby provide the sensing signals (s0(t), s1(t), …, sN-1(t)) having different delays (^^^^, ^^^^, … , ^^^^ି^^) (step 800A-2). In some denotedin Figure 8 as “Option B,” precoding is not performed at the transmitter 500. More specifically,in order to generate the sensing signals (s0(t), s1(t), …, sN-1(t)) having different delays (^^^^, ^^^^,… , ^^^^ି^^), the different delays (^^^^, ^^^^, … , ^^^^ି^^) are applied to respective copies of the initialsensing signal s(t) to thereby provide the sensing signals (s0(t), s1(t), …, sN-1(t)) having differentdelays (^^^^, ^^^^, … , ^^^^ି^^) (step 800B-1). The sensing signals (s0(t), s1(t), …, sN-1(t)) having different delays (^^^^, ^^^^, … , ^^^^ି^^) areprovided to the antennas 510-0 to 510-(N-1), respectively (step 802). In one example embodiment,the sensing signals (s0(t), s1(t), …, sN-1(t)) having different delays (^^^^, ^^^^, … , ^^^^ି^^) to provide a combined sensing signal (step 802A), and the Tx switch 508 outputs the combinedsensing signal to the antennas 510-0 to 510-(N-1) such that, for each time ^^ ൌ ^^^^ to ^^ ൌ^^^^ ^ ^^ for ^^ ൌ ^^,^^, … ,^^െ ^^, the combined sensing signal is output to an i-th antenna 510-I (step802B). Further details regarding the operation of the transmitter 500 are described above and are equally applicable to the corresponding steps of Figure 8. Figure 9 is a flow chart that illustrate the operation of the receiver 600, in accordance with embodiments of the present disclosure. Optional steps are represented by dashed boxes. As illustrated, the receiver 600 receives a sensing signal (i.e., the combined sensing signal transmitted by the transmitter 500) via the antenna 604 of the receiver 600 (step 900). The receiver appliesdifferent delays (^^^^ െ ^^^^, ^^^^ െ ^^^^, … , ^^^^ െ ^^^^ି^^) to the received sensing signal to thereby providedifferent delayed versions of the received signal in which the desired sensing signal components corresponding to the different delays used at the transmitter 500 are time-aligned (step 902). Note that ^^^^is a known or predefined or constant value and is greater than or equal to^^^^ି^^ . As discussed above, the different െ ^^^^, ^^^^ െ ^^^^, … , ^^^^ െ ^^^^ି^^) are such that theN individual sensing signals contained within the received (combined) sensing signal are time-aligned. In this regard, after the different delays (^^^^ െ ^^^^, ^^^^ െ ^^^^, … , ^^^^ െ ^^^^ି^^) to the receivedsensing signal are applied at the receiver 600, the resulting received sensing signals are referred to herein as being “time-aligned” (i.e., the desired sensing signal components in the received sensing signals output by the delays are time-aligned). The receiver 600 then combines the different delayed versions of the received (combined) sensing signal to provide an output sensing signal (step 904). In some embodiments (e.g., where there is precoding at the transmitter 500), the combining of step 904 is simply summing the different delayed versions of the received (combined) sensing signal. In other embodiments (e.g., where there is no precoding at the transmitter 500), the combining in step 904 includes applying beamforming weights or filters to the different delayed versions of the received (combined) sensing signal and then summing the resulting signals. Note that, in some embodiments, the transmitter 500 and the receiver 600 in the sensing system are at different wireless nodes. In this case, signaling between the two nodes may beperformed to indicate, from the transmitter 500 to the receiver 600, the different delays (^^^^, ^^^^,… , ^^^^ି^^) used by the transmitter 500. Figure 10 illustrates one example embodiment of suchsignaling. As illustrated, the procedure of Figure 10 involves a first wireless node 1000-1 (e.g., a wireless communication device such as, for example, a UE) and a second wireless node 1000-2 (e.g., a network node such as, for example, a base station or other Radio Access Network (RAN) node in a 3GPP system). The transmitter 500 is at (i.e., part of) the first wireless node 1000-1, and the receiver 600 is at (i.e., part of) the second wireless node 1000-2. As illustrated, the first wireless node 1000-1 sends, to the second wireless node 1000-2, information that indicates at least one ofthe different delays (^^^^, ^^^^, … , ^^^^ି^^) used by the transmitter 500 (step 1001). For example, theinformation signaled in step 1001 may include the values of all of the delays (^^^^, ^^^^, … , ^^^^ି^^).As another example, the information signaled in step 1001 may include the values of only delays^^^^, … , ^^^^ି^^, where ^^^^ is known (e.g., known to be zero). As yet another example, the signaled in step 1001 may include a delta value and optionally a reference delay value, where thevalues of the delays ^^^^, … , ^^^^ି^^ can then be determined by the second wireless node 1000-2 basedon the reference value and the delta value. For instance, the reference value may be a signaledvalue of ^^^^ or known (non-signaled value of ^^^^ (e.g. ^^^^ ൌ ^^), and the values of the remainingdelays may be calculated as ^^^^ ൌ ^^^^ ^ ^^ ∙ ∆ for ^^ ൌ ^^, … ,^^ െ ^^. Alternatively, the reference valuemay be unknown and estimated by the receiver 600, but the time difference (i.e., the delta value) is signaled to the second wireless node 1000-2. In addition or alternatively to signaling theinformation indicative of at least one of the (^^^^, ^^^^, … , ^^^^ି^^), the first wireless node 1000-1 may send, to the second wireless node 1000-2, information that indicates the precoding weights applied by the precoder 502 of the transmitter 500. The transmitter 500 transmits a combined sensing signal as described above with respect to Figure 8 (step 1002), and the receiver 600performs the procedure of Figure 9 using the indicated delays (^^^^, ^^^^, … , ^^^^ି^^) used by thetransmitter 500 to thereby generate the output sensing signal (step 1004). The second wireless node 100-2 may then perform sensing based on the output sensing signal by the receiver 600 (step 1006). As mentioned above, while a single antenna 604 at the receiver 600 is illustrated in Figure 6, there may be more than one antenna at the receiver side. For example, conventional receive combining can be added on top of the proposed receiver structure as shown in the example embodiment of Figure 11. Figure 11 illustrates an example of a receiver 1100 with M antennas1102-1 to 1102-M. For each i-th antenna 1102-i, different delays (^^^^ െ ^^^^, ^^^^ െ ^^^^, … , ^^^^ െ ^^^^ି^^)are applied to the received signal from the i-th antenna 1102-i via delays 1104-i,0 to 1104-i,3 tothereby provide M delayed versions of the received signal. The different delays (^^^^ െ ^^^^, ^^^^ െ ^^^^,… , ^^^^ െ ^^^^ି^^) essentially undo the delays applied at the transmitter side such that the sensingsignal, if present, in each of the delayed version of the received signal are time-aligned. A TX combiner 1106-i then operates like the combiner 606 above. More specifically, if precoding is applied at the transmitter 500, then the TX combiner 1106-i simply sums the delayed versions of received signal from the delays 1104-i,0 to 1104-i,3 to thereby provided a combined receive signal from the i-th antenna 1102-i. Conversely, if precoding was not performed at the transmitter 500, then the TX combiner 1106-i applies weights or filters to the delayed versions of received signal from the delays 1104-i,0 to 1104-i,3 and then sums the resulting weighted signals to provide the combined receive signal for the i-th antenna 1102-i. An RX combiner 1108 combines (e.g., sums in this case) the M combined receive signals for the M antennas 1102—to 1102-(M-1) to thereby provide an output sensing signal. Note that while TX switching is utilized at the transmitter 500 in the embodiments described above, the same switching technique could also be applied on the receiver side if the receiver 600 or 1100 had fewer receiver chains than antennas. The total number of time slots needed to sense all links is then the multiplication between the number of transmitter antennas and receiver antennas. Technical Specification Impact In some implementations, of the present disclosure may be implemented in a 3GPP system (e.g., a 5G or 6G system) and, as a result, certain changes may be needed to 3GPP specifications. If the sensing is performed between two nodes (e.g., a UE as the transmitter and a network node (e.g., RAN node) as the receiver), the receiver needs to know the format of the transmitted signals, like time-frequency resources, sensing sequence, etc. In addition, the receiver needs to know which transmissions it should combine to obtain a signal that has been virtually beamformed by the transmitter. The receiver needs to know how many transmissions it should combine (four transmissions in the example of Figure 5 and 6) as well when the transmissions occur. One example embodiment is to signal the timing of the first transmission as well as the delta time that occurs between all other transmissions (assumed to be the same). Another possibility would be to signal the timing of the first transmission and multiple delta times (assuming that not all transmissions are separated by the same delta time). Yet another embodiment is to specify the absolute transmission timing of each transmission. In case of a system that uses a symbols grid (e.g. OFDM-based symbols), the transmission timings can be expressed in symbol numbers. The signaling could include the symbol number of the first transmission (e.g., symbol number in a slot or subframe or radio frame) as well a (one or more) deltas (expressed in symbols, potentially together with slots or subframes) between transmission. Also here, the deltas could be the same or different. Alternatively, the timing of all transmissions is specified using absolute (e.g., symbol number in a slot or subframe or radio frame) symbol number. In case one symbol contains two or more transmissions, this must be signaled to the receiver as well, the transmission timings within a symbol and / or how many transmissions occur within a symbol (assuming equal spacing, the receiver can then derive the timing of each transmission within a symbol). In case the system is a monostatic one, the required information would already be present at the receiver (which is the same device as the transmitter) and no such signaling is needed. Still, the system might need to obtain permission to transmit if it uses a shared time—frequency resource. Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processors (DSPs), special-purpose digital logic, and The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according to one or more embodiments of the present disclosure. While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.). Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

Claims

Claims 1. A wireless transmitter (500), delay circuitry (504) configured to provide a plurality of sensing signals (s0(t), s1(t), …, sN-1(t)) having different delays (^^^^, ^^^^, … , ^^^^ି^^), wherein each sensing signal (si(t)), for ^^ ൌ^^,^^, … ,^^െ ^^, is time-limited to a respective time interval of ^^ ൌ ^^^^ to ^^ ൌ ^^^^ ^ ^^, where ^^ is apredefined time duration; andcircuitry (505) configured to provide the plurality of sensing signals (s0(t), s1(t), …, sN-1(t))having different delays (^^^^, ^^^^, … , ^^^^ି^^), respectively, to a plurality of antennas (510-0 to 510-(N-1)).

2. The wireless transmitter (500) of claim 1, wherein the circuitry (505) comprises: summing circuitry (506) configured to combine the plurality of sensing signals to provide a combined sensing signal; and switching circuitry (508) configured to receive the combined sensing signal and output the combined sensing signal to the plurality of antennas (510-0 to 510-(N-1)) such that, for each timeinterval of ^^ ൌ ^^^^ to ^^ ൌ ^^^^ ^ ^^ for ^^ ൌ ^^,^^, … ,^^ െ ^^, the combined sensing signal is output to ani-th antenna (510-i) of the plurality of antennas (510-0 to 510-(N-1)).

3. The wireless transmitter (500) of claim 1 or 2, further comprising a precoder (502) configured to receive an initial sensing signal and apply a plurality of different precoding weights or filters to the initial sensing signal to thereby provide a plurality of precoded signals, respectively; wherein the delay circuitry (504) is configured to apply the different delays (^^^^, ^^^^,… , ^^^^ି^^) to the plurality of precoded signals, respectively, to thereby provide the plurality ofsensing signals (s0(t), s1(t), …, sN-1(t)).

4. The wireless transmitter (500) of claim 3, wherein the plurality of different precoding weights or filters correspond to a desired beamform.

5. The wireless transmitter (500) of any of claims 1 to 4, wherein the predefined time duration^^ is less than ^^^^ െ ^^^^ି^^ for all values of ^^ ൌ ^^, … ,^^െ ^^.

6. The wireless transmitter (500) of any of claims 1 to 5, wherein the wireless transmitter (600) is comprised in a first wireless node (1000-1) configured to transmit information indicativeof at least one of the different delays (^^^^, ^^^^, … , ^^^^ି^^) to a second wireless node (1000-2).

7. The wireless transmitter (500) of any of claims 1 to 5, wherein the wireless transmitter (600) is comprised in a first wireless node (1000-1) configured to transmit information indicative of a timedifference between any two adjacent delays ^^^^െ, ^^^^ି^^ for , ^^ ൌ ^^,^^, … ,^^െ ^^.

8. The wireless transmitter (500) of claim7, wherein the second wireless node (1000-2) is a network node in a radio access network of a cellular communications system.

9. The wireless transmitter (500) of any of claims 6 to 8, wherein the first wireless node (1000- 1) is a wireless communication device.

10. A method performed by a wireless transmitter (500), the method comprising: providing (800) a plurality of sensing signals (s0(t), s1(t), …, sN-1(t)) having different delays(^^^^, ^^^^, … , ^^^^ି^^), wherein each sensing signal (si(t)), for ^^ ൌ ^^,^^, … ,^^ െ ^^, is time-limited to arespective time interval of ^^ ൌ ^^^^ to ^^ ൌ ^^^^ ^ ^^, where ^^ is a predefined time duration; andproviding (802) the plurality of sensing signals (s0(t), s1(t), …, sN-1(t)) having differentdelays (^^^^, ^^^^, … , ^^^^ି^^) to a plurality of antennas (510-0 to 510-(N-1)), respectively.

11. The method of claim 10, wherein providing (801) the plurality of sensing signals (s0(t),s1(t), …, sN-1(t)) having different delays (^^^^, ^^^^, … , ^^^^ି^^) to a plurality of antennas (510-0 to 510-(N-1)), respectively, comprises: summing (802A) the plurality of sensing signals to provide a combined sensing signal; and providing (802B) the combined sensing signal to the plurality of antennas (510-0 to 510-(N-1)) such that, for each time interval of ^^ ൌ ^^^^ to ^^ ൌ ^^^^ ^ ^^ for ^^ ൌ ^^,^^, … ,^^െ ^^, thecombined sensing signal is output to an i-th antenna (510-i) of the plurality of antennas (510-0 to 510-(N-1)).

12. The method of claim 10 or claim 11, wherein providing (800) the plurality of sensingsignals (s0(t), s1(t), …, sN-1(t)) having different delays (^^^^, ^^^^, … , ^^^^ି^^) comprises :applying (800A-1) a plurality of different precoding weights or filters to an initial sensing signal to thereby provide a plurality of precoded signals, respectively; and applying (800-2) the plurality of different delays (^^^^, ^^^^, … , ^^^^ି^^) to the plurality ofprecoded signals, respectively, to thereby provide the plurality of sensing signals (s0(t), s1(t), …, sN-1(t)).

13. The method of claim 12, wherein the plurality of different precoding weights or filters correspond to a desired beamform.

14. The method of any of claims 10 to 13, wherein the predefined time duration ^^ is less than^^^^ െ ^^^^ି^^ for all values of ^^ ൌ ^^, … ,^^െ ^^.method of any of claims 10 to 14, wherein the wireless transmitter (500) is comprisedin a first wireless node, and information indicative of the different delays (^^^^, ^^^^, … , ^^^^ି^^) istransmitted from the first wireless node to a second wireless node.

16. The method of claim 15, wherein the second wireless node is a network node in a radio access network of a cellular communications system.

17. The method of claim 15 or claim 16, wherein the first wireless node is a wireless communication device.

18. A wireless receiver (600), comprising: delay circuitry (602) configured to apply a plurality of different delays (^^^^ െ ^^^^, ^^^^ െ ^^^^,… , ^^^^ െ ^^^^ି^^) to a sensing signal received via an antenna (604) of the wireless receiver (600) toprovide a plurality of received sensing signals that are time-aligned, wherein ^^^^is a constant value greater than or equal to ^^^^ି^^.

19. The wireless receiver (600) of claim 18, further comprising combiner circuitry (606) configured to sum the plurality of received sensing signals to provide a combined sensing signal.

20. The wireless receiver (600) of claim 18, further comprising combiner circuitry (606) configured to combine the plurality of received sensing signals using a plurality of precoding weights or filters, respectively, to provide a combined, beamformed sensing signal.

21. The wireless receiver (600) of any of claims 18 to 20, wherein a sensing signal component of each received sensing signal is time-limited to a respective time interval having a duration of^^ ^ ^^, where ^^ is a delay spread of a channel between the wireless receiver (600) and acorresponding wireless transmitter (500) and ^^ is a predefined time duration.

22. The wireless receiver (600) of claim 21, wherein the predefined time duration ^^ is less than^^^^ െ ^^^^ି^^ for all values of ^^ ൌ ^^, … ,^^െ ^^.

23. The wireless receiver (600) of any of claims 18 to 22, wherein the wireless receiver (600) is comprised in a second wireless node (1000-2) configured to receive, from a first wireless node(1000-1), information indicative of different delays (^^^, ^^^, … , ^^ேି^) used by a transmitter.

24. The wireless receiver (600) of any of claims23, wherein the wireless receiver (600) is comprised in a second wireless node (1000-2) configured to receive, from the first wireless node (1000-1), information indicative precoding weights or filters used by the transmitter.

25. The wireless receiver (600) of claim 23 or 24, wherein the second wireless node is a network node in a radio access network of a cellular communications system.

26. The wireless receiver (600) of any of claims 23 to 25, wherein the first wireless node is a wireless communication device.

27. The wireless receiver (600) of any of claims 18 to 26, wherein the wireless receiver (1100) comprises a plurality of antennas (1102) and the delay circuitry (602) is first delay circuitry (1104- 0) from a plurality of delay circuitries (1104-0) to 1104-(M-1)) coupled to a first antenna (1102-0) from the plurality of antennas (1102).

28. The wireless receiver (600) of claim 27, further comprising: at least one additional delay circuitry (1104-1) configured to apply a plurality of differentdelays (^^^ െ ^^^, ^^^ െ ^^^, … , ^^^ െ ^^ேି^) to an additional sensing signal received via an additionalantenna (1102-1) of the wireless receiver (600) to provide an additional plurality of received sensing signalstime-aligned.

29. The wireless receiver (600) of claim 28, further comprising: first combiner circuitry (1106-0) configured to sum or combine the plurality of received sensing signals output by the first delay circuitry (1104-0) to provide a first combined sensing signal;at least one additional combiner (1106-1) configured to sum or combine the plurality of received sensing signals output at least one additional delay circuitry (1104-1) to provide at least one additional combined sensing signal; and further combiner circuitry (1108) configured to sum or combine the first combined sensing signal and the at least one additional combined sensing signal to provide an output sensing signal.

30. A method performed by a wireless receiver (600), the method comprising: receiving (900) a sensing signal via an antenna (604) of the wireless receiver (600); and applying (902) a plurality of different delays (^^^ െ ^^^, ^^^ െ ^^^, … , ^^^ െ ^^ேି^) to the sensingsignal received via the antenna (604) of the wireless receiver (600) to provide a plurality of received sensing signals that are time-aligned.

31. The method of claim 30, further comprising summing (904) the plurality of received sensing signals to provide a combined sensing signal.

32. The method of claim 30, further comprising combining (904) the plurality of received sensing signals using a plurality of precoding weights or filters, respectively, to provide a combined, beamformed sensing signal.

33. The method of any of claims 30 to 32, wherein a sensing signal component of each receivedsensing signal is time-limited to a respective time interval having a time duration of ^^ ^ ^^, where^^ is a predefined time duration and ^^ is a delay spread of a channel between the wireless receiver (600) and a corresponding wireless transmitter (500).

34. The method of claim 33, wherein the predefined time duration ^^ is less than ^^^ െ ^^^ି^ forall values of ^^ ൌ 1, … ,^^ െ 1.

35. The method of any of claims 30 to 34, wherein the wireless receiver (600) is comprised in a second wireless node (1000-2), and the method further comprises receiving (1001), from a firstwireless node (1000-1), information indicative of at least one of the different delays (^^^, ^^^,… , ^^ேି^) used by an associated transmitter (500).

36. The method of any of claims 30 to 35, wherein the wireless receiver (600) is comprised in a second wireless node (1000-2), and the method further comprises receiving (1001), from a firstwireless node (1000-1), information indicative of precoding weights or filters used by an associated transmitter (500).

37. The method of claim 35 or claim 36, wherein the second wireless node is a network node in a radio access network of a cellular communications system.

38. The method of any of claims 35 to 37, wherein the first wireless node is a wireless communication device.

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