Shaping of symbols for joint communication and sensing

Abstract

There is provided techniques for joint communication and sensing. A method is performed by a first radio transceiver device. The method comprises transmitting, towards a second radio transceiver device, a communication signal at least composed of data symbols and signal-shaping symbols. The signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion.

Description

[0001] SHAPING OF SYMBOLS FOR JOINT COMMUNICATION AND SENSING

[0002] TECHNICAL FIELD

[0003] Embodiments presented herein relate to methods, radio transceiver devices, computer programs, and a computer program product for joint communication and sensing.

[0004] BACKGROUND

[0005] Some wireless communication networks aim to provide sensing services in diverse application areas, such as detection, ranging and tracking of vulnerable road users, automated guided vehicles, or unmanned aerial vehicles. Making use of traditional communication signals that are transmitted from one radio transceiver device to another radio transceiver device for sensing purposes, e.g., to draw conclusions about the surroundings, is sometimes referred to as joint communication and sensing.

[0006] Different scenarios for sensing performed in third-generation partnership project (3GPP) wireless cellular communication networks using New Radio (NR) signals and protocols are schematically illustrated in Fig. 1. The suffix “-s” is short for "sensing” and indicates that the transmitted (Tx) and received (Rx) signals are for sensing rather than for communication purposes. In Fig. 1 (a) is illustrated an example of monostatic sensing of an object 400, which can be a passive object or an active object from a sensing perspective, where a radio transceiver device 200, 300 implemented in a network node transmits sensing signals (SS) that are reflected by object 400 and the reflected sensing signal (SSr) is measured by the radio transceiver device 200, 300. In Fig. 1 (b) is illustrated an example of bi-static sensing of an object, as represented by object 400, where in one example a first radio transceiver device 200 implemented in a UE transmits sensing signals that are reflected by the object 400 and the reflected sensing signal is measured by a second radio transceiver device 300 implemented in a network node. In another example first radio transceiver device 200 implemented in a network node transmits sensing signals that are reflected by the object and the reflected sensing signal is measured by a second radio transceiver device 300 implemented in a UE. In Fig. 1 (c) is illustrated an example of multi-static sensing of an object 400, where in one example a first radio transceiver device 200 implemented in a network node transmits sensing signals that are reflected by the object and the reflected sensing signals are measured by multiple receiving second radio transceiver devices 300 e.g., implemented in a network node and a UE. In another example, also illustrated in Fig. 1 (c), a first radio transceiver device 200 implemented in a UE transmits sensing signals that are reflected by the object 400 and the reflected sensing signals are measured by multiple receiving second radio transceiver devices 300 e.g. implemented in a network node and a UE.

[0007] The idea with joint communication and sensing is similar to using one of the radio transceiver devices as a radar. In this respect, existing radar signals have good sensing properties (e.g. with respect to range resolution) but offer no benefit with respect to data transfer. Communication signals, on the other hand, allow data transfer, but the sensing performance depends on the modulation format, bit pattern (random with data bits) and allocation resources. In further detail, communication signals lack the properties of carefully designed radar signals, which are designed to have good auto-correlation properties in order to promote the detection accuracy also when the reflected signal strength is weak, which happens when the target object is far away from the transmitter, or when the scattered signal is attenuated. Weak reflected signals are also expected when communication signal is beamformed from a transmitting radio transceiver device towards a receiving radio transceiver device, but the target object generally has a different location than the receiving radio transceiver device, so the target object might not be sufficiently illuminated. Furthermore, using communication signals for radar purposes has the drawback that communication signals have content that is random in nature, and their radar properties cannot be guaranteed. This can result in non-predictable performance of the sensing part of the joint communication and sensing system.

[0008] Hence, there is a need for communication signals with improved radar properties.

[0009] SUMMARY

[0010] An object of embodiments herein is to design communication signals for joint communication and sensing purposes that do not suffer from the above issues, or where the above issues at least are mitigated or reduced.

[0011] A particular object is to design communication signals for joint communication and sensing purposes that improve the sensing properties of the communication signals.

[0012] According to a first aspect there is presented a method for joint communication and sensing. The method is performed by a first radio transceiver device. The method comprises transmitting, towards a second radio transceiver device, a communication signal at least composed of data symbols and signal-shaping symbols. The signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion.

[0013] According to a second aspect there is presented a first radio transceiver device for joint communication and sensing. The first radio transceiver device comprises processing circuitry. The processing circuitry is configured to cause the first radio transceiver device to transmit, towards a second radio transceiver device, a communication signal at least composed of data symbols and signal-shaping symbols. The signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion.

[0014] According to a third aspect there is presented a first radio transceiver device for joint communication and sensing. The first radio transceiver device comprises a transmit module configured to transmit, towards a second radio transceiver device, a communication signal at least composed of data symbols and signal-shaping symbols. The signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion. According to a fourth aspect there is presented a computer program for joint communication and sensing. The computer program comprises computer code which, when run on processing circuitry of a first radio transceiver device, causes the first radio transceiver device to perform actions. One action comprises the first radio transceiver device to transmit, towards a second radio transceiver device, a communication signal at least composed of data symbols and signal-shaping symbols. The signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion.

[0015] According to a fifth aspect there is presented a method for joint communication and sensing. The method is performed by a second radio transceiver device. The method comprises receiving, from a first radio transceiver device, a communication signal at least composed of data symbols and signal-shaping symbols. The signalshaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion. The method comprises performing sensing processing using the communication signal.

[0016] According to a sixth aspect there is presented a second radio transceiver device for joint communication and sensing. The second radio transceiver device comprises processing circuitry. The processing circuitry is configured to cause the second radio transceiver device to receive, from a first radio transceiver device, a communication signal at least composed of data symbols and signal-shaping symbols. The signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion. The processing circuitry is configured to cause the second radio transceiver device to perform sensing processing using the communication signal.

[0017] According to a seventh aspect there is presented a second radio transceiver device for joint communication and sensing. The second radio transceiver device comprises a receive module configured to receive, from a first radio transceiver device, a communication signal at least composed of data symbols and signal-shaping symbols. The signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion. The second radio transceiver device comprises a sense module configured to perform sensing processing using the communication signal.

[0018] According to an eighth aspect there is presented a computer program for joint communication and sensing. The computer program comprises computer code which, when run on processing circuitry of a second radio transceiver device, causes the second radio transceiver device to perform actions. One action comprises the second radio transceiver device to receive, from a first radio transceiver device, a communication signal at least composed of data symbols and signal-shaping symbols. The signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion. . One action comprises the second radio transceiver device to perform sensing processing using the communication signal. According to a ninth aspect there is presented a computer program product comprising a computer program according to at least one of the fourth aspect and the eighth aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium.

[0019] Advantageously, these aspects provide communication signals with desired radar properties.

[0020] Advantageously, these aspects provide communication signals for joint communication and sensing purposes that do not suffer from the above issues.

[0021] Advantageously, these aspects improve the sensing properties of the communication signals.

[0022] Advantageously, these aspects can be used to reduce the stochastic-nature of the estimation performance that random-valued communication signals otherwise might showcase in a joint communication and sensing system. Advantageously, these aspects thereby enable the second radio transceiver device to improve its sensing performance, for example in terms of improved range estimation.

[0023] Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

[0024] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

[0027] Fig. 1 is a schematic diagram illustrating positioning and tracking of a UE according to an example;

[0028] Fig. 2 is a schematic illustration of communication signal according to embodiments;

[0029] Figs. 3, 6, and 7 are flowcharts of methods according to embodiments;

[0030] Fig. 4 is a schematic illustration of an auto-correlation function of a communication signal according to embodiments;

[0031] Fig. 5 shows a comparison between auto-correlation functions of different communication signals according to embodiments; Fig. 8 is a schematic diagram showing functional units of a radio transceiver device according to an embodiment;

[0032] Fig. 9 is a schematic diagram showing functional modules of a radio transceiver device according to an embodiment;

[0033] Fig. 10 is a schematic diagram showing functional units of a radio transceiver device according to an embodiment;

[0034] Fig. 11 is a schematic diagram showing functional modules of a radio transceiver device according to an embodiment; and

[0035] Fig. 12 shows one example of a computer program product comprising computer readable means according to an embodiment.

[0036] DETAILED DESCRIPTION

[0037] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional.

[0038] The embodiments disclosed herein relate to techniques for joint communication and sensing. In order to obtain such techniques there is provided radio transceiver devices, methods performed by the radio transceiver devices, a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the radio transceiver devices, causes the radio transceiver devices to perform the methods. In this respect, there could be different examples of radio transceiver devices. In some examples the radio transceiver devices are implemented in respective network nodes. In some examples both radio transceiver devices are implemented in one and the same network node. In some examples the radio transceiver devices are implemented in respective UEs. In some examples both radio transceiver devices are implemented in one and the same UE. In some examples one of the radio transceiver devices is implemented in a network node and another one of the radio transceiver devices is implemented in a UE. Examples of these different alternatives are illustrated in Fig. 1.

[0039] Further in this respect, although one radio transceiver device will be referred to as a first radio transceiver device and one radio transceiver device will be referred to as a second radio transceiver device, this does not imply that there is any hierarchical relation between the radio transceiver devices. Rather, the term first radio transceiver device is used to denote the radio transceiver device that according to the hereinafter disclosed embodiments transmits a communication signal and the term second radio transceiver device is used to denote the radio transceiver device that according to the hereinafter disclosed embodiments receives the communication signal. However, this does not exclude the possibility that both radio transceiver devices might be configured to both transmit and receive such communication signals.

[0040] At least some of the herein disclosed embodiments are based on shaping the communication signal in such a way that its auto-correlation has properties that are predictable and also improve the properties to make the communication signal better for sensing. This will improve the possibility to use the communication signals for radar and sensing purposes. By reserving some symbols in the communication signal for signal-shaping, these symbols can be used to shape the auto-correlation properties of the communication signal. Therefore, these symbols are referred to as signal-shaping symbols. Ideally, the auto-correlation function should have a clear peak around sample zero, i.e., samples outside the peak should be significantly smaller (i.e., have significantly smaller amplitude) than the peak itself. With such properties, a certain accuracy of the range estimate can be guaranteed. By reserving a number of symbols in the communication signal for signal-shaping symbols, the signal values of the signal-shaping symbols can be selected in such a way that the magnitude of the samples outside the main lobe (i.e., the sample at index zero) are small and the main lobe is narrow, leading to predictable and improved sensing performance.

[0041] The herein disclosed embodiments are applicable both for communication signals being single-carrier signals and communication signals being multi-carrier signals, such as OFDM signals. A pre-coding step can be made part of the process when the communication signal is a multi-carrier signal. Here, the term pre-coding is different from spatial precoding, where the latter refers to beamforming the communication signal. The precoding in DFT-s- OFDM (DFT spread OFDM) that is used in the uplink in the air interface of fifth generation (5G) telecommunication systems to reduce the peak-to-average ratio (also known as crest factor) of the communication signal is an example of such precoding. However, the purpose is different.

[0042] Since OFDM signaling is the prevalent signal form in cellular communication, at least some of the herein disclosed embodiments will be presented for such a communication signal. However, this does not exclude the possibility that also other types of communication signals are used.

[0043] Consider a communication signal composed of N symbols in total. For an OFDM signal, in case some subcarriers at the ends of the frequency band are set to zero, which commonly is the case to reduce out-of-band radiation, N is smaller than the number of subcarriers, and otherwise N equals the number of subcarriers. L of these symbols are allocated to signal shaping, and hence the communication signal comprises L signal-shaping symbols. The L allocated symbols do not need to have a consecutive occurrence in the communication signal but can be spread out among the N symbols. Fig. 2 illustrates an example communication signal consisting of N=8 symbols, where L=2 signal-shaping symbols have been inserted at indices n=2 and n=5. In general terms, the values of the signal-shaping symbols can be determined using a signal-shaping algorithm. In some examples, the signal-shaping algorithm is a function that takes N-L data symbols of the communication signal and outputs L signal-shaping symbols. In some examples, the signal-shaping algorithm is a function that takes N data symbols of the communication signal and outputs L signal-shaping symbols, where L of the data symbols are truncated (i.e., replaced by the L signal-shaping symbols). Regardless of which signal-shaping algorithm that is used, the values of the L signal-shaping symbols are selected such that the auto-correlation properties of the resulting communication signal are improved.

[0044] After the signal-shaping, the communication signal is thus a vector of N symbols (data symbols and signalshaping symbols). In case the communication signal is a multi-carrier signal, these symbols are precoded through a multiplication by a matrix F to produce a vector which also contains N precoded symbols. The matrix F can be chosen as the DFT matrix, as in DFT-s-OFDM precoding.

[0045] The communication signal can be modulated (such as according to regular OFDM modulation) to produce a transmit signal to be transmitted over the air.

[0046] Reference is now made to Fig. 3 illustrating a method for joint communication and sensing as performed by the first radio transceiver device 200 according to an embodiment.

[0047] As disclosed above, some symbols in the communication signal are reserved for shaping the auto-correlation properties of the communication signal

[0048] S102: The first radio transceiver device 200 transmits, towards a second radio transceiver device 300, a communication signal. The communication signal is at least composed of data symbols and signal-shaping symbols. The signal-shaping symbols have values based on values of the data symbols. The values are determined for the communication signal to fulfil an auto-correlation criterion.

[0049] Embodiments relating to further details of joint communication and sensing as performed by the first radio transceiver device 200 will now be disclosed with continued reference to Fig. 3.

[0050] As noted above, the signal-shaping symbols are inserted in the communication signal to increase the usefulness of the communication signal for sensing purposes. Hence, signal-shaping symbols need only to be included in the communication signal when the communication signal is used for sensing purposes. In some examples, the first radio transceiver device 200 is informed from another device whether or not the communication signal is to be used for sensing purposes. This so-called another device might be a network controller or a dedicated network node responsible for sensing.

[0051] In some aspects, the first radio transceiver device 200 explicitly or implicitly informs the second radio transceiver device 300 at least of the locations of the signal-shaping symbols in the communication signal. Optionally, the first radio transceiver device 200 might further, explicitly or implicitly, inform the second radio transceiver device 300 of the values of the signal-shaping symbols. Therefore, in some embodiments, the first radio transceiver device 200 is configured to perform (optional) step S104.

[0052] S104: The first radio transceiver device 200 transmits an indication to the second radio transceiver device 300 of locations of the signal-shaping symbols in the communication signal and / or the values of the signal-shaping symbols.

[0053] There could be different ways for the first radio transceiver device 200 to transmit the indication in S104. In some embodiments the indication is transmitted on a joint communication and sensing data channel. In other embodiments the indication is transmitted on a control channel.

[0054] There can be different ways to determine how many of the signal-shaping symbols to include in the communication signal. In general terms, any amount of signal-shaping symbols is possible; the more signalshaping symbols the better the auto-correlation properties can be shaped and hence the better the resulting communication signal will be for sensing purposes. The specific locations of the signal-shaping symbols in the communication signal are however of less importance since application of a precoding matrix, in full generality, might impose an arbitrary perturbation of the symbols in the communication signal. Further aspects relating to how many of the signal-shaping symbols to include in the communication signal will be disclosed next.

[0055] In some non-limiting examples, how many of the signal-shaping symbols to include in the communication signal depends on any, or any combination, of: a target quality of service (QoS) level for the data symbols, modulation and coding parameters used by the first radio transceiver device 200, amount of data symbols to be transmitted to the second radio transceiver device 300. For example, the lower the QoS level needs to be, the higher the number of signal-shaping symbols can be. For example, the lower the modulation and coding level needs to be, the higher the number of signal-shaping symbols can be. For example, the lower the amount of data symbols to be transmitted to the second radio transceiver device 300, the higher the number of signal-shaping symbols can be.

[0056] In some aspects, the number of signal-shaping symbols depends on properties of the physical environment in which the communication signal is transmitted. For example, in a difficult physical environment (e.g., characterizable by many multipath taps), a better (in terms of auto-correlation properties) sensing signal might be needed. In contrast, in a physical environment characterizable by a sparse setting, a poorer (in terms of autocorrelation properties) sensing signal might be enough.

[0057] In some aspects, the number of signal-shaping symbols depends on capabilities of the communication device that performs the sensing. The higher the capability, the lower the number of signal-shaping symbols is required to be. That is, in some embodiments, how many of the signal-shaping symbols to include in the communication signal depends on communication and / or sensing capabilities of the second radio transceiver device 300. In some aspects, the number of signal-shaping symbols is adaptively selected to allow for a trade-off between sensing performance improvement and degraded data channel performance (due to data symbols having to be sacrificed to include signal-shaping symbols in the communication signal). That is, in some embodiments, how many of the signal-shaping symbols to include in the communication signal is determined based on a tradeoff between communication performance and sensing performance.

[0058] Further, the number of signal-shaping symbols might be adaptively selected and thereby change over time. That is, in some embodiments, how many of the signal-shaping symbols to include in the communication signal is changed over time.

[0059] As disclosed above, there can be different ways in which the signal-shaping symbols are formed. As already disclosed, the signal-shaping symbols have values based on values of the data symbols. Further aspects relating thereto will now be disclosed.

[0060] As in a first example, N-L data symbols in the communication signal are processed to yield L signal-shaping symbols. That is, in some examples the communication signal that is transmitted comprises N symbols in total, where L of the symbols are signal-shaping symbols, and where the communication signal that is transmitted is based on an initial communication signal that comprises N-L data symbols. As in a second example, N data symbols in the communication signal are processed to yield L signal-shaping symbols. In this example, L of the data symbols thus need to be truncated (i.e., replaced by the L signal-shaping symbols). That is, in some examples the communication signal comprises N symbols in total, where L of the symbols are signal-shaping symbols, where the communication signal is based on an initial communication signal that comprises N data symbols, and where in the communication signal, L of the data symbols of the initial communication signal are replaced with the L signal-shaping symbols. Various combinations are also possible, for example where LO symbols are reserved for shaping, where L1 data symbols are punctured, and where there are a total of L0+L1 signal-shaping symbols.

[0061] As further already disclosed, the values are determined for the communication signal to fulfil an auto-correlation criterion. Further aspects relating thereto will now be disclosed.

[0062] In general terms, the values of the signal-shaping symbols are determined by changing, selecting, or optimizing, the values of a subset of the symbols in the communication signal for a set of data symbols, that affects the efficiency in locating a peak of the auto-correlation of the communication signal. Therefore, in some embodiments, the auto-correlation criterion specifies a relative value, the maximum absolute value, and / or the width of a peak of an auto-correlation function of the communication signal. Further, the auto-correlation criterion might specify the maximum sidelobe heights (such as the maximum absolute value or the relative maximum absolute value) of the auto-correlation function. Further, the auto-correlation criterion might target the precoded symbols, on which the auto-correlation depends, and specify a target absolute value representing the desired magnitude of all precoded symbols; a precoded symbols vector with constant absolute values results in an autocorrelation with a sharp peak and no sidelobes.

[0063] Here the term efficiency can refer to the ability to fulfil some energy constraints, the ability to enable reduced computational complexity of the sensing receiver at the second communication device 300, the ability to a reduced probability of a false detection of an object that is sensed, the ability to minimize the search space for the peak of the auto-correlation, and / or enable the auto-correlation properties to be less stochastic, and thus more reliable. An explicit optimization might include changing the value of a subset of the data symbol within a given communication signal that can be affecting the efficiency in locating peaks in the auto-correlation of the communication signal.

[0064] In some aspects, the values of the signal-shaping symbols are determined by first forming a desired signal, and then selecting the values of the signal-shaping symbols so that the communication signal has auto-correlation properties that resembles as closely as possible the auto-correlation properties of the desired signal. In some aspects, the values of the signal-shaping symbols are determined by obtaining a communication signal with (at least almost) constant envelope in the frequency domain. Therefore, in some embodiments, the values of the signal-shaping symbols are determined for the communication signal to have a constant envelope (i.e., having the same modulus) in the frequency domain. In this example, the desired correction signal c[n] after precoding can be expressed as: where s[n] represents the data symbols after precoding, and A is the desired amplitude. The signal-shaping symbols x can then be selected as the vector x that minimizes:

[0065] ||Fx - c|| according to some norm, such as the L2 norm or any other suitable norm.

[0066] In further detail, in some aspects, the values of the signal-shaping symbols are determined by forming a desired correction signal, then selecting the signal-shaping symbols so that the correction signal resembles as closely as possible a desired correction signal. In particular, in some embodiments, determining the values of the signalshaping symbols involves selecting a template signal from a set of available template signals that, out of all the available template signals, best matches the communication signal. All template signals fulfil the auto-correlation criterion. The values of the signal-shaping symbols are then determined for the communication signal to better match the selected template signal, or even for the communication signal match the selected template signal as close as possible. In some embodiments, the values of the signal-shaping symbols are determined that minimize an error signal computed as a difference between the communication signal and one of the template signals that fulfils the auto-correlation criterion. In some embodiments, the template signal has constant envelope (in the frequency domain).

[0067] In some aspects, the values of the signal-shaping symbols are determined by taking a time domain signal with signal-shaping symbols and then adapt the signal-shaping symbols such that a frequency domain signal with low amplitude variations is produced. Therefore, in some embodiments, the values of the signal-shaping symbols are determined for the communication signal to, in frequency domain, have amplitude variations below a threshold value. This is since signals with low amplitude variations in the frequency domain generally have auto-correlation properties as desired herein.

[0068] In some aspects, the values of the signal-shaping symbols are found by formulating and solving an optimization problem, where the cost function punishes communication signals with bad auto-correlation properties. That is, in some embodiments, the values of the signal-shaping symbols are determined by solving an optimization problem.

[0069] In general terms, the auto-correlation r[ / c] of a communication signal represented by a sequence of N samples y[n] can be expressed as:

[0070] In general terms, r[ / c] should have a large peak at k = 0 and only small values for other values of k. Such a property makes it easy to use the communication signal for estimating time-of-arrival and to distinguish different the time-of-arrivals of different paths in case of multi-path propagation. The values of the L signal-shaping symbols should then be selected such that r[ / c] has these desirable properties, independently of which (random) data is transmitted on the remaining N-L symbols of the communication signal.

[0071] In some non-limiting examples, the optimization problem is formulated as: where r[ / c] is the auto-correlation, which is a function of the communication signal, where f[k] is a mask representing the auto-correlation criterion, where {xnn e £} is a set of signal-shaping symbols, where £ represents the reserved indices. In some examples, when precoding is used, r[ / c] is a function of the precoded communication signal, and where k e K is the summation index. In some examples, K = {—N, In some examples, K consists only of a subset of the values from —N to N. In some examples, the value 0 is excluded from the set K. In some examples, when precoding is used, r[ / c] is a function of the precoded communication signal. The optimization here is over the £ elements xnin the vector that was allocated for signal-shaping. The mask f[k] is a mask that denotes the desired shape of the auto-correlation. An example auto-correlation function of a communication signal with signal-shaping symbols determined in this way is shown in Fig. 4 where the mask requires the auto-correlation | r [Zc] | to be zero for k = ±1, ±2. Variations of this optimization problem are conceivable, for example adding a term r[0]-2would promote a higher main lobe. Further, as noted above, K might consist only of a subset of the values from —N to N, and thus the summation does not have to run over all indices k = —N, ... , 0, ... , JV .One reason for this is that often the indices closest to zero are the most important.

[0072] A comparison between the auto-correlation function of an original communication signal and a communication signal where signal-shaping symbols have been included is shown in Fig. 5. The original communication signal consists of 100 randomly selected 16-QAM symbols and the adapted communication signal consists of the same 100 randomly selected 16-QAM symbols except the first five symbols that have been replaced by signal-shaping. The first five symbols thus have values that have been selected such that the auto-correlation has a more distinct peak at zero and small values around the zeroth sample. The values of the s signal-shaping symbols were derived using a least-squares solver. It can be seen how the ratio between the peak at zero to the level of the non-zero samples improves from around 20dB to around 10OdB.

[0073] As disclosed above, symbols for multi-carrier signals might be precoded through a multiplication by a matrix to produce a signal vector. Hence, in some embodiments, the communication signal is precoded with a matrix before being transmitted. Examples of such a matrix have been disclosed above. Precoding is necessary when the communication signal is an OFDM. As already mentioned, the precoding can be performed as DFT-s-OFDM precoding.

[0074] Reference is next made to Fig. 6 illustrating a method for joint communication and sensing as performed by the second radio transceiver device 300 according to an embodiment.

[0075] In general terms, it is assumed that the second radio transceiver device 300 receives communication signal as having been transmitted by the first radio transceiver device 200 in S102, and thus that the communication signal has properties as disclosed above.

[0076] S202: The second radio transceiver device 300 receives, from a first radio transceiver device 200, a communication signal. The communication signal is at least composed of data symbols and signal-shaping symbols. The signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion.

[0077] S206: The second radio transceiver device 300 performs sensing processing using the communication signal. In some examples, the sensing processing is performed by yet another communication device, such as a third radio transceiver device that is operatively connectable to the second radio transceiver device 300. The joint communication and sensing might then be performed by the second radio transceiver device 300 in combination with the third radio transceiver device. It is here noted that whereas the purpose of the signal-shaping symbols is for the communication signal to fulfil an auto-correlation criterion, the whole communication signal, and thus not only the signal-shaping symbols, are usable in the sensing processing.

[0078] Embodiments relating to further details of joint communication and sensing as performed by the second radio transceiver device 300 will now be disclosed with continued reference to Fig. 6.

[0079] As disclosed above, the first radio transceiver device 200 might explicitly or implicitly inform the second radio transceiver device 300 at least of the locations of the signal-shaping symbols in the communication signal. Therefore, in some embodiments, the second radio transceiver device 300 is configured to perform (optional) step S204.

[0080] S204: The second radio transceiver device 300 receives an indication from the first radio transceiver device 200 of locations of the signal-shaping symbols in the communication signal and the values of the signal-shaping symbols.

[0081] The second radio transceiver device 300 can then exclude the signal-shaping symbols from the communication signal when only the data symbols are to be processed. In general terms, the second radio transceiver device 300 has to decode the communication signal and from the decoded communication signal recover the L signalshaping symbols. To do that the second radio transceiver device 300 at least needs to know the indices (i.e., the locations of the L signal-shaping symbols). Further, in case the communication signal has been precoded, the second radio transceiver device 300 further needs to know the transformation matrix.

[0082] As further disclosed above, in some embodiments the indication is received on a joint communication and sensing data channel, whereas in other embodiments the indication is received on a control channel.

[0083] In some examples the sensing processing involves the second radio transceiver device 300 to correlate the received communication signal with its own known copy of the communication signal. In some examples the sensing processing involves the second radio transceiver device 300 to use a result of the correlation for sensing estimation in terms of range estimation, Doppler spread estimation, time-of-arrival estimation, etc. In some examples, the sensing processing involves correlating the received signal (i.e., the total received communication signal including both the communication symbols and the signal-shaping symbols) with the recovered transmitted signal. The correlator output can be used to estimate range (time of flight, time of arrival), Doppler shift (radial speed), and direction of arrival. In other examples, the received signal is used together with the known transmitted signal to produce the same estimates but through other types of radar processing, for example using the MUSIC (multiple signal classification) algorithm. One particular embodiment for joint communication and sensing as performed by the first radio transceiver device 200 and the second radio transceiver device 300 based on at least some of the above disclosed embodiments will now be disclosed in detail with reference to the flowchart of Fig. 7.

[0084] S301 : The first communication device 200 selects a desired communication and sensing QoS as well as a modulation and coding scheme.

[0085] S302: Based on the selections made in step S301, the first communication device 200 selects and reserves some of the symbols in a communication signal for signal-shaping. Locations and values of the signal-shaping symbols are thereby selected. How many signal-shaping symbols to select and which values to assign to the signalshaping symbols can be determined in accordance with any of the above-disclosed embodiments.

[0086] 5303 (optional): The first communication device 200 sends an information message to inform the second communication device 300 at least about the locations of the signal-shaping symbols. This step might not be needed if the first communication device 200 and the second communication device 300 are implemented in one and the same device, such as in one and the same network node or one and the same UE. Further, optionally, the second communication device 300 might acknowledge receipt of the information message to prevent an error in subsequent decoding of transmitted data symbols. Further, optionally, the first communication device 200 and the second communication device 300 might negotiate regarding the location and / or amount of signal-shaping symbols in the communication signal. Steps S302 and S303 might then be iteratively performed.

[0087] 5304 (optional): The first communication device 200 precodes the communication signal.

[0088] S305: The first communication device 200 selects a waveform for the (possibly precoded) communication signal.

[0089] S306: The first communication device 200 transmits the (possibly precoded) communication signal using the selected waveform.

[0090] S307: The second communication device 300 receives the communication signal, possibly after the communication signal has been reflected by a target object, as in Fig. 1 .

[0091] S308: The second communication device 300 performs sensing processing using the communication signal in accordance with any of the above disclosed examples. As noted above, in some examples, the sensing processing is performed by yet another communication device.

[0092] S309: The second communication device 300 uses the information about the location of the signal-shaping symbols when extracting the data symbols from the communication signal.

[0093] Fig. 8 schematically illustrates, in terms of a number of functional units, the components of a first radio transceiver device 200 according to an embodiment. Processing circuitry 210 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1210a (as in Fig. 12), e.g. in the form of a storage medium 230. The processing circuitry 210 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0094] Particularly, the processing circuitry 210 is configured to cause the first radio transceiver device 200 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 230 may store the set of operations, and the processing circuitry 210 may be configured to retrieve the set of operations from the storage medium 230 to cause the first radio transceiver device 200 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry 210 is thereby arranged to execute methods as herein disclosed.

[0095] The storage medium 230 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0096] The first radio transceiver device 200 may further comprise a communications (comm.) interface 220 for communications with other entities, functions, and devices, such as the second communication device 300. As such the communications interface 220 may comprise one or more transmitters and receivers, comprising analogue and digital components.

[0097] The processing circuitry 210 controls the general operation of the first radio transceiver device 200 e.g. by sending data and control signals to the communications interface 220 and the storage medium 230, by receiving data and reports from the communications interface 220, and by retrieving data and instructions from the storage medium 230. Other components, as well as the related functionality, of the first radio transceiver device 200 are omitted in order not to obscure the concepts presented herein.

[0098] Fig. 9 schematically illustrates, in terms of a number of functional modules, the components of a first radio transceiver device 200 according to an embodiment. The first radio transceiver device 200 of Fig. 9 comprises a transmit module 210a configured to perform step S102. The first radio transceiver device 200 of Fig. 9 may further comprise a number of optional functional modules, such a transmit module 210b configured to perform step S104. In general terms, each functional module 210a:210c may be implemented in hardware or in software. Preferably, one or more or all functional modules 210a:210c may be implemented by the processing circuitry 210, possibly in cooperation with the communications interface 220 and / or the storage medium 230. The processing circuitry 210 may thus be arranged to from the storage medium 230 fetch instructions as provided by a functional module 210a:210c and to execute these instructions, thereby performing any steps of the first radio transceiver device 200 as disclosed herein.

[0099] Fig. 10 schematically illustrates, in terms of a number of functional units, the components of a second radio transceiver device 300 according to an embodiment. Processing circuitry 310 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1210b (as in Fig. 12), e.g. in the form of a storage medium 330. The processing circuitry 310 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0100] Particularly, the processing circuitry 310 is configured to cause the second radio transceiver device 300 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 330 may store the set of operations, and the processing circuitry 310 may be configured to retrieve the set of operations from the storage medium 330 to cause the second radio transceiver device 300 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry 310 is thereby arranged to execute methods as herein disclosed.

[0101] The storage medium 330 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0102] The second radio transceiver device 300 may further comprise a communications interface 320 for communications with other entities, functions, and devices, such as the first communication device 200. As such the communications interface 320 may comprise one or more transmitters and receivers, comprising analogue and digital components.

[0103] The processing circuitry 310 controls the general operation of the second radio transceiver device 300 e.g. by sending data and control signals to the communications interface 320 and the storage medium 330, by receiving data and reports from the communications interface 320, and by retrieving data and instructions from the storage medium 330. Other components, as well as the related functionality, of the second radio transceiver device 300 are omitted in order not to obscure the concepts presented herein.

[0104] Fig. 11 schematically illustrates, in terms of a number of functional modules, the components of a second radio transceiver device 300 according to an embodiment. The second radio transceiver device 300 of Fig. 11 comprises a number of functional modules; a receive module 310a configured to perform step S202, and a sense module 310c configured to perform step S206. The second radio transceiver device 300 of Fig. 11 may further comprise a number of optional functional modules, such as a receive module 310b configured to perform step S204. In general terms, each functional module 310a:310c may be implemented in hardware or in software.

[0105] Preferably, one or more or all functional modules 310a:310c may be implemented by the processing circuitry 310, possibly in cooperation with the communications interface 320 and / or the storage medium 330. The processing circuitry 310 may thus be arranged to from the storage medium 330 fetch instructions as provided by a functional module 310a:310c and to execute these instructions, thereby performing any steps of the second radio transceiver device 300 as disclosed herein. The first radio transceiver device 200 and / or the second radio transceiver device 300 may be provided as a standalone device or as a part of at least one further device. A, a first portion of the instructions performed by the first radio transceiver device 200 and / or the second radio transceiver device 300 may be executed in a respective first device, and a second portion of the instructions performed by the first radio transceiver device 200 and / or the second radio transceiver device 300 may be executed in a respective second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the first radio transceiver device 200 and / or the second radio transceiver device 300 may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a first radio transceiver device 200 and / or a second radio transceiver device 300 residing in a cloud computational environment. Therefore, although a single processing circuitry 210, 310 is illustrated in Figs. 8 and 10 the processing circuitry 210, 310 may be distributed among a plurality of devices, or nodes. The same applies to the functional modules 210a:210b, 310a:310c of Figs. 9 and 11 and the computer programs 1220a, 1220b of Fig. 12.

[0106] Fig. 12 shows one example of a computer program product 1210a, 1210b comprising computer readable means 1230. On this computer readable means 1230, a computer program 1220a can be stored, which computer program 1220a can cause the processing circuitry 210 and thereto operatively coupled entities and devices, such as the communications interface 220 and the storage medium 230, to execute methods according to embodiments described herein. The computer program 1220a and / or computer program product 1210a may thus provide means for performing any steps of the first radio transceiver device 200 as herein disclosed. On this computer readable means 1230, a computer program 1220b can be stored, which computer program 1220b can cause the processing circuitry 310 and thereto operatively coupled entities and devices, such as the communications interface 320 and the storage medium 330, to execute methods according to embodiments described herein. The computer program 1220b and / or computer program product 1210b may thus provide means for performing any steps of the second radio transceiver device 300 as herein disclosed.

[0107] In the example of Fig. 12, the computer program product 1210a, 1210b is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 1210a, 1210b could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable readonly memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program 1220a, 1220b is here schematically shown as a track on the depicted optical disk, the computer program 1220a, 1220b can be stored in any way which is suitable for the computer program product 1210a, 1210b.

[0108] The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1 . A method for joint communication and sensing, the method being performed by a first radio transceiver device (200), the method comprising: transmitting (S102), towards a second radio transceiver device (300), a communication signal at least composed of data symbols and signal-shaping symbols, wherein the signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion.

2. The method according to claim 1, wherein how many of the signal-shaping symbols to include in the communication signal depends on any, or any combination, of: a target quality of service level for the data symbols, modulation and coding parameters used by the first radio transceiver device (200), amount of data symbols to be transmitted to the second radio transceiver device (300).

3. The method according to claim 1 or 2, wherein how many of the signal-shaping symbols to include in the communication signal depends on communication and / or sensing capabilities of the second radio transceiver device (300).

4. The method according to any preceding claim, wherein how many of the signal-shaping symbols to include in the communication signal is determined based on a tradeoff between communication performance and sensing performance.

5. The method according to any preceding claim, wherein how many of the signal-shaping symbols to include in the communication signal is changed over time.

6. The method according to any preceding claim, wherein the communication signal comprises N symbols in total, wherein L of the symbols are signal-shaping symbols, and wherein the communication signal is based on an initial communication signal that comprises N-L data symbols.

7. The method according to any of claims 1 to 5, wherein the communication signal comprises N symbols in total, wherein L of the symbols are signal-shaping symbols, wherein the communication signal is based on an initial communication signal that comprises N data symbols, and wherein in the communication signal, L of the data symbols of the initial communication signal are replaced with the L signal-shaping symbols.

8. The method according to any preceding claim, wherein the auto-correlation criterion specifies relative value, maximum absolute value, and / or width of a peak of an auto-correlation function of the communication signal.

9. The method according to any preceding claim, wherein the values of the signal-shaping symbols are determined for the communication signal to, in frequency domain, have amplitude variations below a threshold value.

10. The method according to any preceding claim, wherein the values of the signal-shaping symbols are determined for the communication signal to have a constant envelope in frequency domain.11 . The method according to any preceding claim, wherein the values of the signal-shaping symbols are determined by selecting a template signal from a set of available template signals that, out of all the available template signals, best matches the communication signal, wherein the set of template signals fulfil the autocorrelation criterion, and determining the values of the signal-shaping symbols for the communication signal to better match the selected template signal.

12. The method according to any of claims 1 to 10, wherein the values of the signal-shaping symbols are determined that minimize an error signal computed as a difference between the communication signal and a template signal that fulfils the auto-correlation criterion.

13. The method according to claim 11 or 12, wherein the template signal has constant envelope in frequency domain.

14. The method according to any preceding claim, wherein the values of the signal-shaping symbols are determined by solving an optimization problem.

15. The method according to claim 14, wherein the optimization problem is formulated as:where r[ / c] is the auto-correlation, which is a function of the communication signal, where f[k] is a mask representing the auto-correlation criterion, and where {xnn e £} is a set of signal-shaping symbols, where £ represents reserved indices.

16. The method according to any preceding claim, wherein the communication signal is precoded with a matrix before being transmitted.

17. The method according to any preceding claim, wherein the method further comprises: transmitting (S104) an indication to the second radio transceiver device (300) of locations of the signalshaping symbols in the communication signal and / or the values of the signal-shaping symbols.

18. The method according to claim 17, wherein the indication is transmitted on a joint communication and sensing data channel.

19. A method for joint communication and sensing, the method being performed by a second radio transceiver device (300), the method comprising: receiving (S202), from a first radio transceiver device (200), a communication signal at least composed of data symbols and signal-shaping symbols, wherein the signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion; performing (S206) sensing processing using the communication signal.

20. The method according to claim 19, wherein the method further comprises: receiving (S204) an indication from the first radio transceiver device (200) of locations of the signalshaping symbols in the communication signal and the values of the signal-shaping symbols.21 . The method according to claim 20, wherein the indication is received on a joint communication and sensing data channel.

22. A first radio transceiver device (200) for joint communication and sensing, the first radio transceiver device (200) comprising processing circuitry (210), the processing circuitry being configured to cause the first radio transceiver device (200) to: transmit, towards a second radio transceiver device (300), a communication signal at least composed of data symbols and signal-shaping symbols, wherein the signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion.

23. A first radio transceiver device (200) for joint communication and sensing, the first radio transceiver device (200) comprising: a transmit module (210a) configured to transmit, towards a second radio transceiver device (300), a communication signal at least composed of data symbols and signal-shaping symbols, wherein the signalshaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion.

24. The first radio transceiver device (200) according to claim 21 or 22, further being configured to perform the method according to any of claims 2 to 18.

25. A second radio transceiver device (300) for joint communication and sensing, the second radio transceiver device (300) comprising processing circuitry (310), the processing circuitry being configured to cause the second radio transceiver device (300) to: receive, from a first radio transceiver device (200), a communication signal at least composed of data symbols and signal-shaping symbols, wherein the signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion; perform sensing processing using the communication signal.

26. A second radio transceiver device (300) for joint communication and sensing, the second radio transceiver device (300) comprising: a receive module (310a) configured to receive, from a first radio transceiver device (200), a communication signal at least composed of data symbols and signal-shaping symbols, wherein the signalshaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion; a sense module (310c) configured to perform sensing processing using the communication signal.

27. The second radio transceiver device (300) according to claim 25 or 26, further being configured to perform the method according to any of claims 20 to 21 .

28. A computer program (1220a) for joint communication and sensing, the computer program comprising computer code which, when run on processing circuitry (210) of a first radio transceiver device (200), causes the first radio transceiver device (200) to: transmit (S102), towards a second radio transceiver device (300), a communication signal at least composed of data symbols and signal-shaping symbols, wherein the signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion.

29. A computer program (1220b) for joint communication and sensing, the computer program comprising computer code which, when run on processing circuitry (310) of a second radio transceiver device (300), causes the second radio transceiver device (300) to: receive (S202), from a first radio transceiver device (200), a communication signal at least composed of data symbols and signal-shaping symbols, wherein the signal-shaping symbols have values based on values of the data symbols and are determined for the communication signal to fulfil an auto-correlation criterion; perform (S206) sensing processing using the communication signal.

30. A computer program product (1210a, 1210b) comprising a computer program (1220a, 1220b) according to at least one of claims 28 and 29, and a computer readable storage medium (1230) on which the computer program is stored.

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