Devices and methods for integrated sensing and communication in a mobile network

Abstract

An integrated sensing and communication, ISAC, transmitter device (110) comprises a communication interface (113) configured to transmit one or more data communication signals for data communication with an ISAC receiver device (120) using a subset of a plurality of time and frequency resources of a time-frequency grid. Moreover, the ISAC transmitter device comprises processing circuitry (111) configured to allocate a plurality of pilot signals to a further subset of the plurality of time and frequency resources based on a measure indicative of the importance of a sensing performance relative to a data communication performance of the ISAC transmitter device. The communication interface is further configured to transmit the plurality of pilot signals to the ISAC receiver device and / or to a further ISAC receiver device. Thus, the ISAC transmitter device allows adjusting pilot signal allocation depending on the data communication performance relative to the sensing performance.

Description

[0001] DEVICES AND METHODS FOR INTEGRATED SENSING AND COMMUNICATION IN A MOBILE NETWORK

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to wireless communications. More specifically, the present disclosure relates to devices and methods for integrated sensing and communication, ISAC, in a mobile network, in particular a 3GPP network.

[0004] BACKGROUND

[0005] Existing wireless communication networks have been designed for reliable data transmission by using, for instance, optimized waveforms, modulation and coding, MIMO processing, or power and pilot signal allocation schemes. Radio signals may also be used to determine certain physical parameters related to the environment, such as localization of a transmitting or receiving device, detecting the presence of a passive object, classifying a passive object based on characteristic features of the reflected signal, or estimating the range and velocity based on a delay and Doppler shift. Each of these sensing tasks usually requires a different structure of the transmit signal for achieving the best performance.

[0006] Future wireless communication systems are envisioned to provide also sensing functionalities in order to provide new services, which is known as integrated sensing and communication (ISAC) or joint sensing and communication (JSC). Different levels of integration are possible, e.g. (a) combination of separate dedicated sensing and communication hardware in one device, (b) using the same hardware for sensing and communication on different time-frequency resources, and (c) using the same signals for sensing and communication.

[0007] The last option provides the best performance, as the available resources are used most efficiently. However, it is in general not possible to achieve the optimal sensing and communication performance at the same time, primarily because of the following two fundamental trade-offs. While communication signals need to be random in order to convey information that is not alreadv known at the receiver, sensing signals should preferably be deterministic in order to provide good correlation properties like a narrow mainlobe or low sidelobes. The optimal power allocations for sensing and communication are usually different. In particular, the transmit power directed towards the communication receiver may not be useful to detect or track targets in other locations, and vice versa.

[0008] SUMMARY

[0009] It is an objective of the present disclosure to provide improved devices and methods for integrated sensing and communication (ISAC) in a mobile network, in particular a 3GPP network, for providing an optimized trade-off between sensing and communication.

[0010] The foregoing and other objectives are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

[0011] According to a first aspect an integrated sensing and communication, ISAC, transmitter device is provided. The ISAC transmitter device according to the first aspect comprises a communication interface configured to transmit one or more ISAC data communication signals for data communication with at least one ISAC receiver device using a subset of a plurality of time and frequency resources of a time-frequency grid (herein also referred to as resource elements of the timefrequency grid). Moreover, the ISAC transmitter device according to the first aspect comprises processing circuitry configured to allocate a plurality of ISAC pilot signals, in particular for sensing and / or channel estimation, to a further subset of the plurality of time and frequency resources of the time-frequency grid based on a measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device according to the first aspect. The communication interface of the ISAC transmitter device according to the first aspect is further configured to transmit the plurality of ISAC pilot signals, in particular for sensing and / or channel estimation, to the ISAC receiver device and / or to a further ISAC receiver device. Thus, depending on whether the sensing performance or the communication performance is more important the ISAC transmitter device according to the first aspect may adjust the allocation of the plurality of ISAC pilot signals.

[0012] In a further possible implementation form, the processing circuitry of the ISAC transmitter device according to the first aspect is configured to generate the measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device based on a first objective function indicative of the data communication performance of the ISAC transmitter device and a second objective function indicative of the sensing performance of the ISAC transmitter device.

[0013] In a further possible implementation form, the processing circuitry of the ISAC transmitter device according to the first aspect is configured to generate the measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device as a weighted sum of the first objective function indicative of the data communication performance and the second objective function indicative of the sensing performance of the ISAC transmitter device. The weights of the weighted sum may depend on the measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device according to the first aspect. In a further possible implementation form, the first objective function is based on the mutual information.

[0014] In a further possible implementation form, the second objective function is based on the Fisher information.

[0015] In a further possible implementation form, the processing circuitry of the ISAC transmitter device according to the first aspect is configured to allocate the plurality of ISAC pilot signals, in particular for sensing and / or channel estimation, to the further subset of the plurality of time and frequency resources of the time-frequency grid such that the majority of the plurality of ISAC pilot signals are located at or near the edges of the time-frequency grid, e.g. at or at least in the vicinity of the lower and upper time and / or frequency boundaries of the time-frequency grid.

[0016] In a further possible implementation form, the processing circuitry of the ISAC transmitter device according to the first aspect is configured to allocate the plurality of ISAC pilot signals, in particular for sensing and / or channel estimation, to the further subset of the plurality of time and frequency resources of the time-frequency grid such that the frequency difference between respective pilot signals being neighbors in frequency in the time-frequency grid increases or decreases with frequency. In other words, the frequencies of the subcarriers containing the pilot signals (also referred to as pilot subcarriers) may be determined by a non-linear function, for instance, a quadratic function.

[0017] In a further possible implementation form, the processing circuitry of the ISAC transmitter device according to the first aspect is configured to allocate the plurality of ISAC pilot signals, in particular for sensing and / or channel estimation, to the further subset of the plurality of time and frequency resources of the time-frequency grid based on the following pilot allocation function:

[0018] fc = a^ n + a2n2+ a3k' + A, wherein k denotes a frequency index of a respective resource element of the time-frequency grid, k' denotes an index from 0 to N-l (wherein N corresponds to the number of pilot signals, i.e. pilot subcarriers), A denotes an offset and a1;a2, a3denote configuration parameters.

[0019] In a further possible implementation form, the processing circuitry of the ISAC transmitter device according to the first aspect is configured to allocate a power to each of the plurality of pilot signals and / or to each of the plurality of data communication signals based on the measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device. Thus, depending on whether the sensing performance or the communication performance is more important the ISAC transmitter device according to the first aspect may adjust the power allocation of the plurality of ISAC pilot signals and / or the plurality of ISAC data communication signals.

[0020] In a further possible implementation form, the processing circuitry of the ISAC transmitter device according to the first aspect is configured to allocate a higher power to each of the plurality of ISAC pilot signals than to the plurality of ISAC data communication signals.

[0021] In a further possible implementation form, the processing circuitry of the ISAC transmitter device according to the first aspect is configured to allocate a power to each of the plurality of pilot signals and / or each of the plurality of data communication signals based on the measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device.

[0022] In a further possible implementation form, the processing circuitry of the ISAC transmitter device according to the first aspect is configured to allocate the power to each of the plurality of pilot signals based on the following power allocation function:

[0023]

[0024] wherein pkdenotes the k-th allocated power, fkdenotes the frequency, gkdenotes normalized channel gains, acdenotes a weighting factor indicative of the importance of the data communication performance and asdenotes a weighting factor indicative of the importance of the sensing performance.

[0025] In a further possible implementation form, the communication interface of the ISAC transmitter device according to the first aspect is further configured to send to the ISAC receiver device and / or the further ISAC receiver device information indicative of the allocation of the plurality of ISAC pilot signals to the plurality of time and frequency resources of the timefrequency grid.

[0026] In a further possible implementation form, the communication interface of the ISAC transmitter device according to the first aspect is further configured to send to the ISAC receiver device and / or the further ISAC receiver device information indicative of the allocation of power to the plurality of pilot signals and / or the plurality of data communication signals. In a further possible implementation form, the communication interface of the ISAC transmitter device according to the first aspect is configured to transmit the plurality of ISAC pilot signals, in particular for sensing and / or channel estimation, to the ISAC receiver device and / or to a further ISAC receiver device together with the one or more ISAC data communication signals, i.e. substantially concurrent with the one or more ISAC data communication signals.

[0027] According to a second aspect a method for operating an integrated sensing and communication, ISAC, transmitter device is provided. The method according to the second aspect comprises: transmitting one or more ISAC data communication signals for communication with an ISAC receiver device using a subset of a plurality of time and frequency resources of a time-frequency grid;

[0028] allocating a plurality of ISAC pilot signals, in particular for sensing or channel estimation, to a further subset of the plurality of time and frequency resources based on a measure indicative of the importance of the sensing performance relative to the communication performance of the ISAC transmitter device; and

[0029] transmitting the plurality of ISAC pilot signals to the ISAC receiver device and / or a further ISAC receiver device.

[0030] The method according to the second aspect can be performed by the ISAC transmitter device according to the first aspect. Thus, further features of the method according to the second aspect result directly from the functionality of the ISAC transmitter device according to the first aspect as well as its different implementation forms described above and below. According to a third aspect, a computer program product is provided, comprising a computer-readable storage medium for storing program code which causes a computer or a processor to perform the method according to the second aspect, when the program code is executed by the computer or the processor.

[0031] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

[0032] BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In the following, embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which:

[0034] Fig. la shows a schematic diagram illustrating a wireless network including an ISAC transmitter device according to an embodiment in communication with an ISAC receiver device according to an embodiment;

[0035] Fig. lb shows a schematic diagram illustrating a wireless network including an ISAC transmitter device according to an embodiment in communication with an ISAC receiver device according to a further embodiment;

[0036] Figs. 2a, 2b show schematic diagrams illustrating a waterfilling power allocation scheme;

[0037] Figs. 3a, 3b show schematic diagrams illustrating two pilot allocation schemes;

[0038] Figs. 4a, 4b show schematic diagrams illustrating a power allocation scheme for delay estimation for two SNRs; Figs. 5a, 5b show two examples illustrating a power allocation implemented by an ISAC transmitter device according to an embodiment;

[0039] Figs. 6a, 6b and 6c show time-frequency grids illustrating different pilot allocation schemes implemented by an ISAC transmitter device according to an embodiment;

[0040] Fig. 7 shows a signaling diagram illustrating the exchange of information between an ISAC transmitter device according to an embodiment and an ISAC receiver device according to an embodiment; Fig. 8 shows a flow diagram illustrating a method of operating a wireless transmitter device according to an embodiment for ISAC in a mobile network.

[0041] In the following, identical reference signs refer to identical or at least functionally equivalent features.

[0042] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the present disclosure or specific aspects in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and / or aspects described herein may be combined with each other, unless specifically noted otherwise.

[0044] Figure la shows a schematic diagram illustrating a mobile network 100 configured to provide mobile communication services. In an embodiment, the mobile network 100 may be a current or future 3rd Generation Partnership Project (3GPP) mobile network 100, for instance, a 5G or a 6G network. The mobile network 100 comprises one or more integrated sensing and communication, ISAC, transmitter devices, such as the ISAC transmitter device 110 shown in figure la, for sensing and data communication with one or more ISAC receiver devices, such as the ISAC receiver device 120 shown in figure la. In an embodiment, the ISAC transmitter device 110 may be implemented as a base station 110 or a distributed radio unit 110 and the ISAC receiver device 120 may be implemented as a user equipment, UE, 120.

[0045] As illustrated in figure la, the ISAC transmitter device 110 comprises processing circuitry 111 and a communication interface 113, for instance, a transceiver unit 113. The processing circuitry 111 may be implemented in hardware and / or software. The hardware may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or one or more general-purpose processors. Moreover, the ISAC transmitter device 110 may comprise a memory 115 configured to store executable program code which, when executed by the processing circuitry 111, causes the ISAC transmitter device 110 to perform the functions and operations described herein.

[0046] Likewise, the ISAC receiver device 120 may comprise processing circuitry 121 and a communication interface 123, for instance, a transceiver unit 123. The processing circuitry 121 may be implemented in hardware and / or software. The hardware may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or one or more general-purpose processors. Moreover, the ISAC receiver device 120 may comprise a memory 125 configured to store executable program code which, when executed by the processing circuitry 121, causes the ISAC receiver device 120 to perform the functions and operations described herein.

[0047] As will be described in more detail below, the ISAC transmitter device 110 is configured to implement improved pilot allocation schemes and, in an embodiment, power allocation schemes. Before describing more detailed embodiments of the ISAC transmitter device 110 in the following some technical background on pilot allocation schemes will be described. Several power allocation algorithms for communication have been extensively studied. Considering K parallel AWGN channels with normalized channel gains gk, it is well known that the mutual information with Gaussian input signals I = X fc= i l°g( l + 9k ' Pk) ismaximized if the powers are determined according to the waterfilling solution pk=

[0048] max(0 — l / gk, 0), where 6 is chosen such that the average power constraint is fulfilled with equality.

[0049] As illustrated in figures 2a and 2b, waterfilling allocates more power to strong channels with large normalized channel gains gk. At low signal-to-noise ratio (SNR), weak channels with small normalized channel gains gkmay be switched off, whereas waterfilling converges to an equal power allocation at high SNR.

[0050] There are also many power allocation algorithms for more practical settings. For example, mercury / waterfilling maximizes the mutual information for arbitrary input constellations. Other bit and power loading algorithms consider uncoded bit or symbol error rates for adaptive modulation. All these power allocation schemes have in common that the powers pkonly depend on the normalized channel gains gk, but not on the location of the subchannel in the time-frequency grid, which may be suboptimal for sensing.

[0051] The optimized power allocation between pilot and data symbols for coherent receivers with pilot-aided channel estimation has also been studied. It turns out that the number of pilot symbols should be minimized for a certain target channel estimation quality in order to maximize the available resources for data transmission, but the power of pilot symbols should be increased compared to the data symbols. This is also referred to as pilot boosting.

[0052] For block fading channels, where the channel remains approximately constant within a certain block of time-frequency resources, the location of the pilot symbols within a block is irrelevant. However, for dispersive channels, where the channel gain varies over time and / or frequency, the pilot symbols should be preferably uniformly spread across the time-frequency grid (as illustrated in figure 3a). If the channel varies only slowly in time, the pilots may be placed close to the beginning of the transmitted block (as illustrated in figure 3b) in order to reduce the decoding delay at the receiver. Such pilot allocations are in general not optimal for specific sensing tasks.

[0053] For sensing, suitable performance criteria need to be chosen depending on the objective (e.g., target detection, object recognition, or parameter estimation). The Cramer-Rao bound (CRB) may serve as a lower bound for the mean squared error (MSE) of an unbiased estimator. Considering an OFDM system with 2K subcarriers at frequencies fkand symmetric power allocation p_k= pkfor f_k= —fk, the CRB for delay estimation is given by MSET> CRB

[0054]

[0055] case, it is optimal to allocate all available power to the outermost subcarriers. However, this results in large sidelobes of the autocorrelation function, which may only be acceptable as long as integer ambiguities can be resolved (e.g., in tracking applications that use a-priori information from previous measurements).

[0056] The Ziv-Zakai bound (ZZB) enables a more accurate prediction of the MSE, as it takes large errors due to outliers into account. The optimal waveform then provides a tradeoff between the width of the main lobe of the autocorrelation function and the size of the side lobes. At high SNR (illustrated in figure 4b), outliers can be mostly neglected, and the resulting optimal power allocation is similar to that minimizing the CRB (i.e., allocating most of the available power to the outermost subcarriers). On the other hand, outliers caused by large sidelobes are dominating at low SNR (illustrated in figure 4a), so more power should be allocated to the inner subcarriers, which results in a faster decay of the side lobes. Similar results hold for the power allocation in the time domain for Doppler estimation, which is the frequency-domain dual to delay estimation. In summary, the requirements regarding the pilot and power allocation differ significantly for communication and sensing. For communication, the number of pilot symbols should be as small as possible, and the power allocation depends on the normalized channel gains gk. On the other hand, deterministic pilot symbols are preferable for sensing in order to control the correlation properties of the transmit signal, and the optimal power allocation depends on the sensing objective and the location in the time-frequency grid. A separate design of communication and sensing as in current systems is highly suboptimal, as it does not make efficient use of all available resources.

[0057] For communicating with the at least one ISAC receiver device 120 the communication interface 113 of the ISAC transmitter device 110 is configured to transmit one or more ISAC data communication signals to the ISAC receiver device 120 using a subset of a plurality of time and frequency resources 602 of a time-frequency grid 600 (herein also referred to as resource elements 602 of the time-frequency grid 600 illustrated in figures 6a-c), in particular a OFDM time-frequency grid 600. As will be appreciated, each resource element 602 of the OFDM time-frequency grid 600 may be defined, for instance, by a subcarrier frequency and a time slot or OFDM symbol number.

[0058] The processing circuitry 111 of the ISAC transmitter device 110 is configured to allocate a plurality of ISAC pilot signals 601 , in particular for sensing and / or channel estimation, to a further subset of the plurality of time and frequency resources 602 of the time-frequency grid 600, i.e. to resource elements 602 of the OFDM time-frequency grid 600 not occupied by the ISAC data communication signals. As will be described in more detail below, the processing circuitry 111 of the ISAC transmitter device 110 is configured to allocate the plurality of ISAC pilot signals 601 based on, i.e. depending on a measure indicative of the importance of the sensing performance of the ISAC transmitter device 110 relative to the data communication performance of the ISAC transmitter device 110. In other words, depending on whether the sensing performance or the data communication performance is more important the ISAC transmitter device 110 may adjust the allocation of the plurality of ISAC pilot signals 601. The communication interface 113 of the ISAC transmitter device 110 is configured to transmit the plurality of ISAC pilot signals 601 allocated in the way described above to the ISAC receiver device 120. Thus, the ISAC transmitter device 110 may use the same transmit signals for both communication and sensing. The transmit signals may be radiated from one or multiple antennas of the communication interface 113 of the ISAC transmitter device 110.

[0059] According to a variant illustrated in figure lb, the communication interface 113 of the ISAC transmitter device 110 is configured to transmit the ISAC data communication signals to the ISAC receiver device 120, while the plurality of allocated ISAC pilot signals 601 transmitted by the ISAC transmitter device 110 may be received (for instance, after a reflection by a passive target object) by a further ISAC receiver device 130 co-located with the ISAC transmitter device 110. In other words, in the embodiment shown in figure lb the ISAC transmitter device 110 and the ISAC receiver device 130 are components of a single entity, such as a base station. Thus, the communication and sensing receivers may belong to the same or different entities. For example, for bi- or multi-static sensing the sensing receivers may be located at different positions, while for mono-static sensing the sensing receiver is co-located with the transmitter. As will be appreciated, due to the broadcast nature of wireless channels, both data communication signals and pilot signals are received (and may be processed) by all receivers. In particular, the communication receiver implemented by the ISAC receiver device 120 may use the pilot signals to estimate the communication channel, while the sensing receiver implemented by the ISAC receiver device 130 may also use the known data signals for sensing. In the embodiment shown in figure lb, the sensing receiver 130 is co-located with the ISAC transmitter 110 (e.g., in a BS or UE) in order to perform a specific sensing task (e.g., target detection or tracking, or gesture recognition), while the communication receiver 120 (e.g., a UE or a BS) is located at a different position. As will be appreciated, there may also be multiple communication receivers, which are served using a suitable multiple access scheme (e.g., TDMA or FDMA, where different time of frequency resources are allocated to the receivers, or SDMA, where signals may be separated through beamforming). This may apply, e.g., to scenarios, where UE devices (e.g., cars, drones, or robots) want to communicate with each other or the network while simultaneously sensing their environment or their relative positions.

[0060] In an embodiment, the processing circuitry 111 of the transmitter device 110 is further configured to allocate a power to each of the plurality of pilot signals 601 and / or to each of the plurality of data communication signals based on the measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device 110.

[0061] Thus, as the optimal pilot and power allocations for communication and sensing may be very different, the ISAC transmitter device 110 may implement adaptive pilot and power allocation schemes for ISAC depending on the communication and sensing requirements.

[0062] In an embodiment, for the power allocation, an objective function may be used that provides a tradeoff between communication and sensing performance measures. In an embodiment, the processing circuitry 111 of the ISAC transmitter device 110 may implement a linear combination:

[0063] / (P) = «c- fc(p + as' fs(.P).

[0064] whereinc(p) is an objective function for communication, fs(p) is an objective function for sensing, and acand asare weighting factors related to communication and sensing, respectively.

[0065] In an embodiment, the processing circuitry 111 of the ISAC transmitter device 110 may select the objective functions fc(p) and fs(p) based on the measure indicative of the importance of the sensing performance of the ISAC transmitter device 110 relative to the data communication performance of the ISAC transmitter device 110, for instance, based on the selected communication scheme (including, e.g., waveform, modulation, channel coding) and the selected sensing task (e.g., target detection or tracking), respectively. As will be appreciated, a large ratio aclasassigns higher priority to communication, while a small ratio aclasassigns higher priority to sensing.

[0066] Based on the objective function, an optimized power allocation function may be obtained. For example, using the mutual information / c(p) =

[0067]

[0068] log(l + 9k ' Pk)asthe communication objective and the scaled Fisher information fs(p) = .k=ifk ' Pk- which corresponds to the inverse of CRBTfor delay estimation, as the sensing objective, the optimal power allocation implemented by the processing circuitry 111 of the ISAC transmitter device 110 may be given by:

[0069]

[0070] where 6 is chosen such that the power constraint fc= i P / < = P is fulfilled.

[0071] An example for equal channel gains gk= 1 is shown in figure 5a. At low SNR (i.e., for small transmit power P), all power is allocated to the outermost subcarrier pB, which is optimal for the delay estimation according to CRBT(for communication, the power allocation is arbitrary in this case). For increasing SNR, additional subcarriers are activated in order to increase the mutual information for communication. At high SNR, again a large portion of the power is allocated to p8. This demonstrates the impact of the SNR on the tradeoff between communication and sensing.

[0072] Another example for linearly decreasing channel gains gk= 2 — 2 / 9 • k is shown in figure 5b. At low SNR, all power is allocated to the strongest subcarrier p1;which is optimal for communication. For increasing SNR, additional subcarriers are activated according to their channel gains, which is similar to the waterfilling solution. However, at high SNR, again a large portion of the power is allocated to the outermost subcarrier pB. This demonstrates the impact of the channel gains on the tradeoff between communication and sensing.

[0073] As alreadv described above, the processing circuitry 111 of the ISAC transmitter device 110 is configured to allocate the ISAC pilot signals 601, in particular for sensing and / or channel estimation, to a subset of the plurality of time and frequency resources 602 of the time-frequency grid 600. Conventionally, pilots used for communication only are usually distributed uniformly at approximately equidistant positions in the time-frequency grid in order to achieve a good channel estimation accuracy. According to an embodiment the processing circuitry 111 of the ISAC transmitter device 110 is configured to allocate the ISAC pilot signals 601 in a non-uniform fashion to locations in the time-frequency grid 600 that are most important for a certain sensing task. For example, for delay / Doppler estimation, more pilot symbols may be allocated at the edges of the allocated resources in the frequency / time domain, as illustrated by the different cases shown in figures 6a-c. More specifically, as illustrated in figure 6a, for delay estimation the processing circuitry 111 of the ISAC transmitter device 110 may be configured to allocate the ISAC pilot signals 601 to resource elements 602 being close to the lower and upper frequency boundaries of the time-frequency grid 600 but being adjacent in time. As illustrated in figure 6b, for Doppler estimation the processing circuitry 111 of the ISAC transmitter device 110 may be configured to allocate the ISAC pilot signals 601 to resource elements 602 being close to the lower and upper time boundaries of the time-frequency grid 600. As will be appreciated, the allocation illustrated in figure 6c is a combination of the allocations illustrated in figures 6a and 6b. As will be appreciated, replacing random data symbols by deterministic pilots reduces the fluctuations of the sensing errors and thus helps to achieve a guaranteed sensing performance, which may be especially important for time-critical sensing applications. In an embodiment, the ISAC transmitter device 110 is configured to signal the locations of the ISAC pilot symbols 601 in the time-frequency grid 600 to the ISAC receiver device 120, as will be described in more detail below. As defined in 3GPP TS 38.211 (Physical channels and modulation), conventionally the demodulation reference signal (DMRS) is mapped to physical resources according to:

[0074] <

[0075]

[0076] where k and I denote the frequency and time index of a resource element, respectively. This corresponds to a uniform assignment of (groups of) DMRS pilot symbols at equal distances in the frequency domain.

[0077] In order to obtain a non-uniform pilot allocation, according to an embodiment the processing circuitry 111 of the ISAC transmitter device 110 is configured to implement the subcarrier assignment using a nonlinear function, e.g., k = a^ n + a2n2+ a3k' + A. The type of the function may be configured by the radio resource control (RRC) parameter dmrs.DMRSConfigurationType, which is currently restricted to values {1, 2} and may be extended to further type values, while parameters of the nonlinear function may be either pre-defined or configured by an additional RRC parameter, e.g., dmrs.DMRSConfigurationParameters = [a1;a2,a3,...]. It is also possible to store pre-configured sets of parameters in a table, which are then selected, e.g., by RRC signaling or downlink control information (DCI).

[0078] According to a further embodiment additional DMRS configuration types may be introduced for specific sensing tasks, e.g., delay or Doppler estimation. These may be combined with existing or new resource mapping functions that have been optimized for communication, e.g., using an extended RRC parameter dmrs.DMRSConfigurationType = [t1;t2], The resource elements used for pilot signals then correspond to the union of resource elements selected by the different configuration types t, and t2, which may also be extended to more than two configuration types. It should be emphasized that the communication and sensing receivers can exploit all pilot signals in order to obtain the best performance. Similar modifications are possible for other pilot signals, e.g. channel state information reference signals (CSI-RS), sounding reference signals (SRS), and / or synchronization signals (SS).

[0079] Conventional power control is specified, e.g., in 3GPP TS 38.214 (Physical layer procedures for data), where the power or energy per resource element (EPRE) is assumed to be constant over the assigned time-frequency resources. The only degree of freedom consists in assigning different powers to pilot and data signals. This is in general sufficient for communication, but may be suboptimal for sensing.

[0080] According to an embodiment, similar to the pilot allocation the processing circuitry 111 of the ISAC transmitter device 110 may be configured to implement the power allocation using a nonlinear function, that may depend on the estimated channel, the location of a resource element, and other parameters. In an embodiment, the processing circuitry 111 of the ISAC transmitter device 110 may be configured to implement the following power allocation function:

[0081]

[0082] This function may be selected based on the sensing task from a set of pre-defined functions using RRC signaling. The subcarrier frequencies fkare related to the location of a resource element and depend on the chosen numerology and the allocated resources. The channel gains gkmay be obtained through CSI feedback or, assuming that channel reciprocity holds, from previous measurements of the reverse channel. As already described above, the parameters acand as, which indicate the priorities of communication and sensing, or their ratio aclasmay be selected by either RRC or DCI signaling. The parameter Q may then be determined by the IS AC transmitter device 110 based on a power constraint.

[0083] There may be different power allocation functions for pilot and data signals. These functions may be independent or depend on each other. For example, a first function may be used to allocate power for data symbols, and a second function may allocate the power to be used for pilot symbols depending on the first function.

[0084] An example of the signaling for the downlink of a wireless communication system is shown in figure 7. The ISAC transmitter device 110 in the form of a base station 110, e.g. gNB 110 informs the ISAC receiver device 120 in the form of a UE 120 about the power allocation that it used for the subsequent transmission on the physical downlink shared channel (PDSCH), which enables the UE 120 to properly estimate the channel and perform certain sensing tasks. More specifically, in a step 701 of figure 7 the ISAC transmitter device 110, e.g. gNB 110 uses RRC signaling to the UE 120 for configuring the power allocation function. In a step 703 of figure 7 the ISAC transmitter device 110, e.g. gNB 110 uses DCI signaling to the UE 120 for selecting the parameters of the power allocation function. In a step 705 of figure 7 the ISAC transmitter device 110, e.g. gNB 110 makes a PDSCH transmission to the UE 120 based on the selected power allocation function with the selected parameters. In a step 707 of figure 7 the UE 120 performs channel estimation and sensing based on the selected power allocation function with the selected parameters. Figure 8 shows a flow diagram illustrating a method 800 for operating an integrated sensing and communication, ISAC, transmitter device, such as the ISAC transmitter device 110 shown in figures la and lb. The method 800 comprises a step 801 of transmitting one or more ISAC data communication signals for communication with an ISAC receiver device, such as the ISAC receiver device 120 of figure la or the ISAC receiver device 120 of figure lb, using a subset of a plurality of time and frequency resources of a time-frequency grid. Moreover, the method 800 comprises a step 803 of allocating a plurality of ISAC pilot signals, in particular for sensing or channel estimation, to a further subset of the plurality of time and frequency resources based on a measure indicative of the importance of the sensing performance relative to the communication performance of the ISAC transmitter device, as already described in detail above. The method 800 further comprises a step 805 of transmitting the plurality of ISAC pilot signals to the ISAC receiver device 120 and / or a further ISAC receiver device 130.

[0085] The method 800 can be performed by the ISAC transmitter device 110. Thus, further features of the method 800 result directly from the functionality of the ISAC transmitter device 110 as well as the different embodiments thereof described above and below.

[0086] The person skilled in the art will understand that the "blocks" ("units") of the various figures (method and apparatus) represent or describe functionalities of embodiments of the present disclosure (rather than necessarily individual "units" in hardware or software) and thus describe equally functions or features of apparatus embodiments as well as method embodiments (unit = step).

[0087] In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described embodiment of an apparatus is merely exemplary. For example, the unit division is merely a logical function division and may be another division in an actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.

[0088] The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

[0089] In addition, functional units in the embodiments of the disclosure may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units may be integrated into one unit.

Claims

CLAIMS1. An integrated sensing and communication, ISAC, transmitter device (110), comprising:a communication interface (113) configured to transmit one or more data communication signals for data communication with an ISAC receiver device (120) using a subset of a plurality of time and frequency resources (602) of a time-frequency grid (600); andprocessing circuitry (111) configured to allocate a plurality of pilot signals (601 ) to a further subset of the plurality of time and frequency resources (602) based on a measure indicative of the importance of a sensing performance relative to a data communication performance of the ISAC transmitter device (110);wherein the communication interface (113) is further configured to transmit the plurality of pilot signals (601) to the ISAC receiver device (120) and / or to a further ISAC receiver device (130).

2. The ISAC transmitter device (110) of claim 1, wherein the processing circuitry (111) is configured to generate the measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device (110) based on a first objective function indicative of the data communication performance of the ISAC transmitter device (110) and a second objective function indicative of the sensing performance of the ISAC transmitter device (110).

3. The ISAC transmitter device (110) of claim 2, wherein the processing circuitry (111) is configured to generate the measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device (110) as a weighted sum of the first objective function indicative of the data communication performance and the second objective function indicative of the sensing performance of the ISAC transmitter device (110).

4. The ISAC transmitter device (110) of claim 2 or 3, wherein the first objective function is based on the mutual information.

5. The ISAC transmitter device (110) of any one of claims 2 to 4, wherein the second objective function is based on the Fisher information.

6. The ISAC transmitter device (110) of any one of claims 1 to 5, wherein the processing circuitry (111) is configured to allocate the plurality of pilot signals (601 ) to the further subset of the plurality of time and frequency resources (602) of the time-frequency grid (600) such that the majority of the plurality of pilot signals (601) are located at or near the edges of the time-frequency grid (600).

7. The ISAC transmitter device (110) of any one of claims 1 to 5, wherein the processing circuitry (111) is configured to allocate the plurality of pilot signals (601 ) to the further subset of the plurality of time and frequency resources (602) of the time-frequency grid (600) such that the frequency difference between respective pilot signals (601) being neighbors in the time-frequency grid (600) increases or decreases with frequency.

8. The ISAC transmitter device (110) of claim 7, wherein the processing circuitry (111) is configured to allocate the plurality of pilot signals (601 ) to the further subset of the plurality of time and frequency resources (602) of the timefrequency grid (600) based on the following pilot allocation function:fc = a^ n + a2n2+ a3k' + A,wherein k denotes a frequency index of a respective resource element (602) of the time-frequency grid (600), k' denotes an index from 0 to N- 1 , A denotes an offset and a , , a2, a3denote configuration parameters.

9. The ISAC transmitter device (110) of any one of the preceding claims, wherein the processing circuitry (111) is configured to allocate a power to each of the plurality of pilot signals (601 ) and / or to each of the plurality of data communication signals based on the measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device (110).

10. The ISAC transmitter device (110) of any one of the preceding claims, wherein the processing circuitry (111) is configured to allocate a higher power to each of the plurality of pilot signals (601) than to the plurality of data communication signals.

11. The ISAC transmitter device (110) of any one of the preceding claims, wherein the processing circuitry (111) is configured to allocate a power to each of the plurality of pilot signals (601 ) and / or each of the plurality of data communication signals based on the measure indicative of the importance of the sensing performance relative to the data communication performance of the ISAC transmitter device (110).

12. The ISAC transmitter device (110) of any one of the preceding claims, wherein the processing circuitry (111) is configured to allocate the power to each of the plurality of pilot signals (601) based on the following power allocation function:wherein pkdenotes the k-th allocated power, fkdenotes the frequency, gkdenotes normalized channel gains, acdenotes a weighting factor indicative of the importance of the data communication performance and asdenotes a weighting factor indicative of the importance of the sensing performance.

13. The ISAC transmitter device (110) of any one of the preceding claims, wherein the communication interface (113) is further configured to send to the ISAC receiver device (120) and / or the further ISAC receiver device (130) information indicative of the allocation of the plurality of pilot signals (601 ) to the plurality of time and frequency resources (602) of the time-frequency grid (600).

14. The ISAC transmitter device (110) of any one of the preceding claims, wherein the communication interface (113) is further configured to send to the ISAC receiver device (120) and / or the further ISAC receiver device (130) information indicative of the allocation of power to the plurality of pilot signals (601 ) and / or the plurality of data communication signals.

15. The ISAC transmitter device (110) of any one of the preceding claims, wherein the communication interface (113) is configured to transmit the plurality of pilot signals (601) to the ISAC receiver device (120) and / or the further ISAC receiver device (130) together with the one or more data communication signals.

16. A method (800) of operating an integrated sensing and communication, ISAC, transmitter device (110), wherein the method (800) comprises:transmitting (801) one or more data communication signals for communication with an ISAC receiver device (120) using a subset of a plurality of time and frequency resources (602) of a time-frequency grid (600);allocating (803) a plurality of pilot signals (601) to a further subset of the plurality of time and frequency resources (602) based on a measure indicative of the importance of the sensing performance relative to the communication performance of the ISAC transmitter device (110); andtransmitting (805) the plurality of pilot signals (601 ) to the ISAC receiver device (120) and / or to a further ISAC receiver device (130).

17. A computer program product comprising a computer-readable storage medium for storing program code which causes a computer or a processor to perform the method (800) of claim 16 when the program code is executed by the computer or the processor.

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