Method and system for radar sensing

Abstract

A method of radar sensing is provided. The method includes: obtaining a first received communication signal and a second received communication signal received by a radar antenna system, whereby the first received communication signal is received via a direct channel from a communication signal transmitted by a communication antenna to the radar antenna system and the second received communication signal is received via a radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from an object; sampling each of the first and second received communication signals based on beat frequency sampling to obtain sampled first and second received communication signals; determining a cross correlation of the sampled first and second received communication signals; and determining a distance between the radar antenna system and the object and / or a displacement of the object based on the cross correlation of the sampled first and second received communication signals. There is also provided a corresponding system for radar sensing and an integrated communication and sensing (ICAS) system.

Description

METHOD AND SYSTEM FOR RADAR SENSINGCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority of Singapore Patent Application No.10202500764W filed on 24 March 2025, the content of which being hereby incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] The present invention generally relates to a method of radar sensing, and a system thereof, and more particularly, for integrated communication and sensing (ICAS).BACKGROUND

[0003] Traditionally, wireless communications and radar sensing work separately. They conduct and optimize respective functions independently. Both wireless communications and radar sensing occupy precious radio frequency (RF) spectrum, which becomes more and more crowded along with increasing demands on high-speed information transmission and dense sensing. To be sustainable and to enhance practical applications, integrated communication and sensing (ICAS) is desired. ICAS may also be interchangeably referred to as integrated sensing and communication (IS AC) or joint radar and communication (JRC) Besides saving the precious RF spectrum, ICAS also has the potential to save the hardware resource and so on. ITU-R (International Telecommunication Union Radiocommunication Sector) has listed ISAC as one of six usage scenarios for IMT-2030 (international mobile telecommunications 2030) and beyond.

[0004] Carlos Baquero Barneto, et al., “Full-Duplex OFDM Radar With LTE and 5G NR Waveforms: Challenges, Solutions, and Measurements”, IEEE Transactions on Microwave Theory and Techniques, Volume: 67, Issue: 10, 2019 (hereinafter referred to as the Barneto reference) studied radar sensing with orthogonal frequency division multiplexing (OFDM) based waveforms, with particular focus on 4G Long-Term Evolution (LTE) and 5G-NR standard waveforms. The problem stemming from the unused subcarriers within the LTE and NR transmit signal passbands and their impact on frequency-domain radar processing is addressed. In particular, a computationally efficient interpolation approach is disclosed to mitigate the effects of such empty subcarriers in the radar processing. The Tx-Rx self-leakageproblem, to which RF canceller and baseband canceller are required to address, is discussed. This is a challenging task in the real system.

[0005] Sahan Damith Liyanaarachchi, et al., “Optimized Waveforms for 5G-6G Communication with Sensing: Theory, Simulations and Experiments”, IEEE Transactions on Wireless Communications, Volume: 20, Issue: 12, 2021 considered a monostatic JCAS system (hereinafter referred to as the Liyanaarachchi reference), where the full-duplex radar transceiver and the communication transmitter are the same device, and pursue orthogonal frequencydivision multiplexing (OFDM) waveform optimization by jointly minimizing the lower bounds of delay and Doppler estimation. This is attained by filling the empty subcarriers within the OFDM frame with optimized samples while reallocating a proportion of the communication subcarriers’ power to control the fairness between the two functionalities (communications and radar sensing). Both communication and filled radar subcarriers are used for radar processing. The peak-to-average power ratio of the waveform is also minimized along the optimization process. The trade-off between communication and sensing is investigated, which indicates that the lower bounds can be improved at the cost of the communication capacity. Moreover, the real over-the-air RF measurements are carried out with unoptimized and optimized 5GNR (new radio) waveforms at the 28GHz mm-wave band. However, such a JCAS system still suffers from Tx-Rx self-leakage interference issue.

[0006] Ojas Kanhere, et al., “Target Localization using Bistatic and Multistatic Radar with 5G NR Waveform”, IEEE 93rd Vehicular Technology Conference (VTC2021-Spring) 2021 (hereinafter referred to as the Kanhere reference), proposes a JCAS system with mmWave 5G-NR waveform. Different from the Bameto and Liyanaarachchi references discussed above, a bistatic radar configuration is considered. In particular, a theoretical metric that characterizes how the target location estimation error varies as a function of the bistatic geometry and measurement errors is derived. It is shown that with FR2 (frequency range 2) mmWave 5G-NR waveform, the bistatic configuration can achieve a location accuracy of 10.0 cm over a bistatic range of 25 m, which can be further improved by deploying a multistatic radar configuration. The bistatic and multistatic structures avoid the issue in the Bameto and Liyanaarachchi references discussed above. However, such a JCAS system needs a phased array to detect direction of arrival (DoA), which indirectly obtains the range and location information of the radar target

[0007] All of the Barneto, Liyanaarachchi and Kanhere references discussed above use a high sampling rate to obtain a sufficient range resolution, which has a high hardware complexity with a large power consumption and is limited by fabrication technology capability.

[0008] A need therefore exists to provide a method of radar sensing, as well as a system for thereof, that seeks to overcome, or at least ameliorate, one or more deficiencies in conventional radar sensing methods, and more particularly, with improved efficiency and effectiveness, such as enabling a lower sampling rate and / or addressing the Tx-Rx self-leakage interference issue. It is against this background that the present invention has been developed.SUMMARY

[0009] According to a first aspect of the present invention, there is provided a method of radar sensing comprising:obtaining a first received communication signal and a second received communication signal received by a radar antenna system, wherein the first received communication signal is received via a direct channel from a communication signal transmitted by a communication antenna to the radar antenna system and the second received communication signal is received via a radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from an object,sampling each of the first and second received communication signals based on beat frequency sampling to obtain sampled first and second received communication signals, determining a cross correlation of the sampled first and second received communication signals; anddetermining a distance between the radar antenna system and the object and / or a displacement of the object based on the cross correlation of the sampled first and second received communication signals.

[0010] According to a second aspect of the present invention, there is provided a system for radar sensing comprising:at least one memory; andat least one processor communicatively coupled to the at least one memory and configured to:obtain a first received communication signal and a second received communication signal received by a radar antenna system, wherein the first received communication signal is received via a direct channel from a communication signal transmitted by a communicationantenna to the radar antenna system and the second received communication signal is received via a radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from an object;sample each of the first and second received communication signals based on beat frequency sampling to obtain sampled first and second received communication signals; determine a cross correlation of the sampled first and second received communication signals; anddetermine a distance between the radar antenna system and the object and / or a displacement of the object based on the cross correlation of the sampled first and second received communication signals.

[0011] According to a third aspect of the present invention, there is provided an integrated communication and sensing (ICAS) system comprising:a communication antenna for transmitting communication signals for wireless communications;a radar antenna system for receiving communication signals from the communication antenna via a direct channel and a radar reflection channel; anda system according to the above-mentioned second aspect of the present invention communicatively coupled to the radar antenna system for performing radar sensing.

[0012] According to a fourth aspect of the present invention, there is provided a computer program product, embodied in one or more non-transitory computer-readable storage mediums, comprising instructions executable by at least one processor to perform the method of radar sensing according to the above-mentioned first aspect of the present invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments of the present invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings, in which:FIG. 1 depicts a schematic diagram of a method of radar sensing, according to various embodiments of the present invention;FIG. 2 depicts a schematic block diagram of a system for radar sensing, according to various embodiments of the present invention;FIG. 3 depicts a schematic block diagram of a radar sensing system, according to various embodiments of the present invention;FIG. 4 depicts a schematic block diagram of an integrated communication and sensing (ICAS) system, according to various embodiments of the present invention;FIG. 5 depicts a schematic block diagram of an ICAS system, according to various example embodiments of the present invention;FIG. 6 depicts a schematic drawing illustrating an example beat frequency sampling, according to various example embodiments of the present invention;FIG. 7 depicts a flow diagram of an example method of radar sensing according to various example embodiments of the present invention;FIG. 8 shows simulation results of radar target range estimation with standard communication waveform of 5G-NR: OFDM signal; 1024 subcarriers; 1024 random 256-QAM symbols; signal bandwidth 100MHz;FIG. 9 shows displacement / vital sign detection with 5G-NR waveform (target 1 at 1m with ±2.5mm perturbation in speed of 0.2 Hz;FIG. 10 shows an example orthogonal time frequency and space (OTFS) waveform generation,FIG. 11 shows simulation results of OTFS waveform for radar sensing (OTFS signal; M=1024 in delay domain, N=1024 in Doppler domain, random 256-QAM at each point in delay-Doppler domain; signal bandwidth 100MHz; Guard band=5MHz; radar targets 1 meter and 15 meters);FIG. 12 shows displacement / vital sign detection with OTFS waveform (target 1 at 1 meter with ±2.5mm perturbation in speed of 0.2 Hz); andFIG. 13 depicts a schematic block diagram of an example experimental prototype with a software defined radio platform.DETAILED DESCRIPTION

[0014] Various embodiments of the present invention generally relate to a method of radar sensing, and a system thereof, and more particularly, for integrated communication and sensing (ICAS). ICAS may also be interchangeably referred to as integrated sensing and communication (ISAC) or joint radar and communication (JRC).

[0015] As discussed in the background, conventional radar sensing methods suffer from various technical problems, such as requiring a high sampling rate to obtain a sufficient range resolution and suffering from a Tx-Rx self-leakage interference issue. The high sampling rate undesirably results in a high hardware complexity with a large power consumption. In thisregard, various embodiments of the present invention provide a method of radar sensing, as well as a system thereof, that seeks to overcome, or at least ameliorate, one or more deficiencies in conventional radar sensing methods, and more particularly, with improved efficiency and effectiveness, such as enabling a lower sampling rate and / or addressing the Tx-Rx self-leakage interference issue.

[0016] FIG. 1 depicts a schematic diagram of a method 100 of radar sensing, according to various embodiments of the present invention. The method 100 comprises obtaining (at 106) a first received communication signal and a second received communication signal received by a radar antenna system. The first received communication signal is received via a direct channel from a communication signal transmitted by a communication antenna (of a communication transmitter) to the radar antenna system (of a radar receiver). The second received communication signal is received via a radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from an object (which may also be referred to as a target). In other words, the communication signal transmitted by the communication antenna is received by the radar antenna system via the direct channel (as the first received communication signal) and via the radar reflection channel (as the second received communication signal) after being reflected by the object. The method 100 further comprises sampling (at 108) each of the first and second received communication signals based on beat frequency sampling to obtain sampled first and second received communication signals. That is, the first received communication signal is sampled using beat frequency sampling to obtain a sampled first received communication signal, and the second received communication signal is sampled using beat frequency sampling to obtain a sampled second received communication signal. The method 100 further comprises: determining (at 110) a cross correlation of the sampled first and second received communication signals; and determining (at 112) a distance between the radar antenna system and the object and / or a displacement of the object based on the cross correlation of the sampled first and second received communication signals. In this regard, in various first embodiments, a distance between the radar antenna system and the object (which may also be referred to as a range of the object) may be determined based on the cross correlation of the sampled first and second received communication signals. In various second embodiments, a displacement of the object may be determined based on the cross correlation of the sampled first and second received communication signals.

[0017] The method 100 of radar sensing advantageously has improved efficiency and effectiveness. Firstly, the range or displacement of the object is advantageously determined based on a cross correlation of the sampled first and second received communication signals that have each been sampled based on beat frequency sampling. This advantageously enables a lower sampling rate, thereby reducing hardware complexity and power consumption, while still being able to effectively perform radar sensing. Furthermore, the method 100 is configured to simply listen in on communication signals transmitted by the communication transmitter via both the direct channel and the radar reflection channel, thereby advantageously enabling passive radar sensing without dedicated radar emission, and thus, eliminating or addressing the Tx-Rx self-leakage interference issue. Accordingly, the method 100 of radar sensing advantageously has improved efficiency and effectiveness, which also enhances practical applications. These advantages or technical effects, and / or other advantages or technical effects, will become more apparent to a person skilled in the art as the method 100 of radar sensing, as well as the corresponding system for radar sensing, is described in more detail according to various embodiments and example embodiments of the present invention.

[0018] In various embodiments, based on the beat frequency sampling, each of the first and second received communication signals is sampled based on a sampling interval that is a predefined duration longer than a symbol interval of the communication signal transmitted by the communication antenna. It will be appreciated by a person skilled in the art that the difference between the sampling interval and the symbol interval of the communication signal (i.e., the above-mentioned predefined duration longer, which may also be referred to as the sample-symbol interval difference Δ) may be set or configured as appropriate for beat frequency sampling and the present invention is not limited to any specific or particular difference. In various embodiments, the sampling interval may be set to be slightly longer than the symbol interval of the communication signal. In various embodiments, the sample-symbol interval difference Δ may be configured or set based on a desired beat frequency and a symbol interval (e.g., based on a predefined relationship with the beat frequency and the symbol interval). In various embodiments, the sample-symbol interval difference Δ may be configuredor set to configure or set the number of times the received communication signal must at leastbe sampled in order to recover or reconstruct one symbol of the received communication signal.For example, Δ = 0.1T results in 10 times the received communication signal must be sampled in order to recover or reconstruct one symbol of the received communication signal, and thus results in 10 equivalent symbol samples (i.e., these 10 symbol samples collectively areequivalent to one symbol (to recover or reconstruct one symbol)) after 10 symbols have passed (e.g., symbol level sampling).

[0019] In various embodiments, based on the beat frequency sampling, each of the first and second received communication signals is sampled at least a determined number of times. In this regard, the determined number of times is determined based on a beat frequency between a symbol rate of the communication signal transmitted by the communication antenna and a sampling rate corresponding to the sampling interval. In this regard, one complete symbol of a communication signal can be recovered or reconstructed after the received communication signal has been sampled the predetermined number of times.

[0020] In various embodiments, the sampling rate is at symbol level, which may also be referred to as symbol level sampling. That is, in various embodiments, the sampling rate is one sample per symbol. Accordingly, in various embodiments, the sampling rate is advantageously significantly reduced to symbol level, thereby significantly reducing hardware complexity and power consumption, while still being able to effectively perform radar sensing.

[0021] In various embodiments, the sampled first received communication signal comprises (or is) a first received signal vector comprising a sequence of first symbol samples obtained from the above-mentioned sampling the first received communication signal based on the beat frequency sampling for the determined number of times. Similarly, the sampled second received communication signal comprises (or is) a second received signal vector comprising a sequence of second symbol samples obtained from the above-mentioned sampling the second received communication signal based on the beat frequency sampling for the determined number of times. For example, the sequence of first symbol samples may be referred to as a sequence of first equivalent symbol samples as these first equivalent symbol samples obtained from sampling the first received communication signal the determined number of times are collectively equivalent to one symbol (to recover or reconstruct one symbol) of the first received communication signal. Similarly, for example, the sequence of second symbol samples may be referred to as a sequence of second equivalent symbol samples as these second equivalent symbol samples obtained from sampling the second received communication signal the determined number of times are collectively equivalent to one symbol (to recover or reconstruct one symbol) of the second received communication signal.

[0022] In various embodiments, the method 100 further comprises determining a peak of the cross correlation of the sampled first and second received communication signals corresponding to the object. In this regard, the distance between the radar antenna system andthe object or the displacement of the object is determined based on the determined peak of the cross correlation corresponding to the object (e.g., radar target). For example, in the case of one radar target reflection, the peak of the cross correlation may be a global maximum thereof

[0023] In various first embodiments, the above-mentioned determining (at 112) a distance between the radar antenna system and the object comprises: determining a path delay of the second received communication signal associated with the object based on the determined peak of the cross correlation corresponding to the object; and determining the distance between the radar antenna system and the object based on the path delay associated with the object.

[0024] In various first embodiments, the above-mentioned second received communication signal is received via the radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from a plurality of objects. In this regard, the method 100 further comprises determining, for each of the plurality of objects, a peak of the cross correlation of the sampled first and second received communication signals corresponding to the object. Furthermore, for each of the plurality of objects, the above-mentioned determining at (112) a distance between the radar antenna system and the object comprises: determining a path delay of the second received communication signal associated with the object based on the determined peak of the cross correlation corresponding to the object; and determining the distance between the radar antenna system and the object based on the path delay associated with the object. Accordingly, in various first embodiments, in the case of multiple radar target reflections, the method 100 may determine multiple distances to multiple objects, respectively, based on multiple peaks of the cross correlation of the sampled first and second received communication signals determined / located corresponding to the multiple objects, respectively.

[0025] In various second embodiments, the above-mentioned determining (at 112) a displacement of the object comprises: determining a phase change of the cross correlation of the sampled first and second received communication signals at the determined peak corresponding to the object over time; and determining the displacement of the object based on the phase change of the cross correlation at the determined peak corresponding to the object (e.g., radar target) over time. For example, in the case of one radar target reflection, the peak of the cross correlation may be a global maximum thereof. As an illustrative example, by determining (or measuring) the displacement of an object over time, for example, a vital sign of a subject may be measured, such as the subject’s breathing. For example, the displacement of the object may be determined (or measured) continuously over time or over a predefinedtime period as desired or as appropriate without going beyond the scope of the present invention.

[0026] In various second embodiments, the second received communication signal is received via the radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from a plurality of objects. In this regard, the method 100 further comprises determining, for each of the plurality of objects, a peak of the cross correlation of the sampled first and second received communication signals corresponding to the object. Furthermore, for each of the plurality of objects, the above-mentioned determining (at 112) a displacement of the object comprises: determining a phase change of the cross correlation of the sampled first and second received communication signals at the determined peak corresponding to the object over time, and determining the displacement of the object based on the phase change of the cross correlation at the determined peak corresponding to the object over time. Accordingly, in various second embodiments, in the case of multiple radar target reflections, the method 100 may determine multiple displacements of multiple objects, respectively, over time based on the cross correlation of the sampled first and second received communication signals at multiple peaks determined / located corresponding to the multiple objects, respectively.

[0027] In various embodiments, the method 100 further comprises determining whether the determined distance between the radar antenna system and the object satisfies a predefined distance threshold condition. In this regard, the above-mentioned determining a displacement of the object is performed based on determining that determined distance between the radar antenna system and the object satisfies the predefined distance threshold condition. Accordingly, in various embodiments, various first and second embodiments are combined whereby, for each of the plurality of objects, the above-mentioned determining a displacement of the object is performed if the determined distance between the radar antenna system and the object satisfies a predefined distance threshold condition. It will be appreciated by a person skilled in the art that the present invention is not limited to any specific or particular distance threshold condition for determining whether to proceed with determining a displacement of the object, which may be defined or set as desired or as appropriate, such as and not limited, based on a specific distance value (e.g., if the determined distance is larger than or equal to the defined distance value) or a range of threshold values (e g, if the determined distance is within the defined range of distance values).

[0028] In various embodiments, the radar antenna system (of a radar receiver) comprises: a first radar antenna arranged for receiving the first received communication signal via the direct channel from the communication signal transmitted by the communication antenna; and a second radar antenna arranged for receiving the second received communication signal via the radar reflection channel from the communication signal transmitted by the communication antenna.|0029| In various embodiments, the communication antenna (of a communication transmitter) and the radar antenna system (of a radar receiver) are collocated for ICAS. Furthermore, the radar antenna system is of a passive radar receiver. That is, the radar receiver is a passive radar receiver, that is, only listens in on communication signals without dedicated radar emission. In various embodiments, the communication transmitter may be a communication transceiver, and thus, the communication antenna may be a communication transmitter or transceiver antenna.

[0030] It will be appreciated by a person skilled in the art that the present invention is not limited to any particular or specific type of communication signals (e.g., any particular or specific type of modulation), as long as they are radio frequency (RF) communication signals, such as but limited to, 5G-NR signals, Orthogonal Time Frequency Space (OTFS) signals or Orthogonal Frequency-Division Multiplexing (OFDM) signals. Accordingly, it will be appreciated by a person skilled in the art that the communication signals utilized or employed in the method 100 may be conventional communication signals known in the art or may be a new type of communication signals (e.g., a new type of modulation) developed in the future without going beyond the scope of the present invention. Accordingly, various wireless communication techniques are known in the art and thus need not be described herein for clarity and conciseness.

[0031] FIG. 2 depicts a schematic block diagram of a system 200 for radar sensing, according to various embodiments of the present invention, corresponding to the above-mentioned method 100 of radar sensing as described hereinbefore with reference to FIG. 1 according to various embodiments of the present invention. The system 200 comprises: at least one memory 202; and at least one processor 204 communicatively coupled (e.g., connected) to the at least one memory 202 and configured to perform the method 100 of radar sensing according to various embodiments of the present invention. Accordingly, the at least one processor 204 is configured to: obtain a first received communication signal and a second received communication signal received by a radar antenna system, wherein the first receivedcommunication signal is received via a direct channel from a communication signal transmitted by a communication antenna to the radar antenna system and the second received communication signal is received via a radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from an object; sample each of the first and second received communication signals based on beat frequency sampling to obtain sampled first and second received communication signals; determine a cross correlation of the sampled first and second received communication signals; and determine a distance between the radar antenna system and the object and / or a displacement of the object based on the cross correlation of the sampled first and second received communication signals.

[0032] It will be appreciated by a person skilled in the art that the at least one processor 204 may be configured to perform various functions or operations through set(s) of instructions (e.g., software modules) executable by the at least one processor 204 to perform various functions or operations. Accordingly, as shown in FIG. 2, the system 200 may comprise: a communication signal obtaining module (or a communication signal obtaining circuit) 206 configured to obtain a first received communication signal and a second received communication signal received by a radar antenna system, wherein the first received communication signal is received via a direct channel from a communication signal transmitted by a communication antenna to the radar antenna system and the second received communication signal is received via a radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from an object; a beat frequency sampling module (or a beat frequency sampling circuit) 208 configured to sample each of the first and second received communication signals based on beat frequency sampling to obtain sampled first and second received communication signals; a cross correlation determining module (or a cross correlation determining circuit) 210 configured to determine a cross correlation of the sampled first and second received communication signals; and a distance / displacement determining module (or a distance / displacement determining circuit) 212 configured to determine a distance between the radar antenna system and the object and / or a displacement of the object based on the cross correlation of the sampled first and second received communication signals.

[0033] It will be appreciated by a person skilled in the art that the above-mentioned modules are not necessarily separate modules, and two or more modules may be realized by or implemented as one functional module (e g., a circuit or a software program) as desired or asappropriate without deviating from the scope of the present invention. For example, two or more of the communication signal obtaining module 206, the beat frequency sampling module 208, the cross correlation determining module 210 and the distance / displacement determining module 212 may be realized (e.g., compiled together) as one executable software program (e.g., embedded control firmware), which for example may be stored in the at least one memory 202 and executable by the at least one processor 204 to perform the corresponding functions or operations as described herein according to various embodiments of the present invention.

[0034] In various embodiments, the system 200 for radar sensing corresponds to the method 100 of radar sensing as described hereinbefore with reference to FIG. 1, therefore, various operations, functions or steps configured to be performed by the least one processor 204 may correspond to various operations, functions or steps of the method 100 of radar sensing described hereinbefore according to various embodiments, and thus need not be repeated with respect to the system 200 for radar sensing for clarity and conciseness. In other words, various embodiments described herein in context of methods (e.g., the method 100 of radar sensing) are analogously valid for the corresponding systems or devices (e.g., the system 200 for radar sensing), and vice versa. For example, in various embodiments, the at least one memory 202 may have stored therein the communication signal obtaining module 206, the beat frequency sampling module 208, the cross correlation determining module 210 and / or the distance / displacement determining module 212, which respectively correspond to various operations, functions or steps of the method 100 of radar sensing as described hereinbefore according to various embodiments, which are executable by the at least one processor 204 to perform the corresponding operations, functions or steps as described herein.

[0035] A computing system, a controller, a microcontroller or any other system providing a processing capability may be provided according to various embodiments in the present invention. Such a system may be taken to include one or more processors and one or more computer-readable storage mediums. For example, the system 200 for radar sensing described hereinbefore may include at least one processor 204 and at least one computer-readable storage medium (or memory) 202 which are for example used in various processing carried out therein as described herein. A memory or computer-readable storage medium used in various embodiments may be a volatile memory, for example a DRAM (Dynamic Random Access Memory) or a non-volatile memory, for example a PROM (Programmable Read Only Memory), an EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), or a flashmemory, e.g., a floating gate memory, a charge trapping memory, an MRAM (Magnetoresistive Random Access Memory) or a PCRAM (Phase Change Random Access Memory).

[0036] In various embodiments, a “circuit” may be understood as any kind of a logic implementing entity, which may be special purpose circuitry or a processor executing software stored in a memory, firmware, or any combination thereof Thus, in an embodiment, a “circuit” may be a hard-wired logic circuit or a programmable logic circuit such as a programmable processor, e.g., a microprocessor (e.g., a Complex Instruction Set Computer (CISC) processor or a Reduced Instruction Set Computer (RISC) processor). A “circuit” may also be a processor executing software, e.g., any kind of computer program, e.g., a computer program using a virtual machine code, e.g., Java Any other kind of implementation of various functions or operations may also be understood as a “circuit” in accordance with various other embodiments. Similarly, a “module” may be a portion of a system according to various embodiments in the present invention and may encompass a “circuit” as above, or may be understood to be any kind of a logic-implementing entity therefrom.

[0037] Some portions of the present disclosure may be explicitly or implicitly presented in terms of algorithms and functional or symbolic representations of operations on data within a computer memory. These algorithmic descriptions and functional or symbolic representations are the means used by those skilled in the data processing arts to convey most effectively the substance of their work to others skilled in the art. An algorithm may be, and generally, conceived to be a self-consi stent sequence of steps leading to a desired result.

[0038] The present specification also discloses a system (e.g., which may also be embodied as one or more devices or apparatuses), such as the system 200 for radar sensing, for performing various operations, functions or steps of various methods described herein. Such a system may be specially constructed for the required purposes or may comprise a general purpose computer system selectively activated or reconfigured by a computer program stored in the computer system. In general, various algorithms that may be presented herein are not limited to being implemented or executed by any particular computer system. Alternatively, the construction of more specialized computer system to perform various operations, functions or steps of various methods described herein may be provided as desired or as appropriate without going beyond the scope of the present invention.

[0039] In addition, the present specification also at least implicitly discloses computer program(s) or software / functional module(s), in that it would be apparent to a person skilled in the art that various operations, functions or steps of various methods described herein may beput into effect by computer code. The computer program(s) is not intended to be limited to any particular programming language and implementation thereof, and it will be appreciated by a person skilled in the art that a variety of programming languages and coding thereof may be used to implement the computer program(s). Moreover, the computer program(s) is not intended to be limited to any particular control flow as there are a variety of programming languages which can use different control flows. It will be appreciated by a person skilled in the art that a computer program may be stored on any computer-readable storage medium (non-transitory computer-readable storage medium), such as but not limited to, a magnetic disk, an optical disk or a memory chip. For example, a computer program stored on a computer-readable storage medium may be loaded and executed on a computer system to implement various operations, functions or steps of various methods described herein according to various embodiments of the present invention.

[0040] Accordingly, in various embodiments, there is provided a computer program product, embodied in one or more computer-readable storage mediums (non-transitory computer-readable storage medium), comprising instructions (e.g., the communication signal obtaining module 206, the beat frequency sampling module 208, the cross correlation determining module 210 and / or the distance / displacement determining module 212) executable by one or more computer processors to perform a method 100 of radar sensing as described hereinbefore with reference to FIG 1 according to various embodiments of the present invention. Accordingly, various computer programs or software modules described herein may be stored in a computer program product receivable by a system therein, such as the system 200 for radar sensing as shown in FIG. 2, for execution by at least one processor 204 of the system 200 to perform various operations, functions or steps of various methods described herein according to various embodiments of the present invention.

[0041] It will be appreciated by a person skilled in the art that various modules described herein (e g., the communication signal obtaining module 206, the beat frequency sampling module 208, the cross correlation determining module 210 and / or the distance / displacement determining module 212) may be software module(s) realized by computer program(s) or set(s) of instructions executable by a computer processor to perform various functions or operations. Various modules described herein (the communication signal obtaining module 206, the beat frequency sampling module 208, the cross correlation determining module 210 and / or the distance / displacement determining module 212), together with the at least one processor 204 and the at least one memory 202, may also be implementedas hardware module(s) being functional hardware unit(s) designed to perform various functions or operations. More particularly, in the hardware sense, a module is a functional hardware unit designed for use with other components or modules. For example, a module may be implemented using discrete electronic components, or it can form a portion of an entire electronic circuit such as an Application Specific Integrated Circuit (ASIC) or a Field Programmable Gate Array (FPGA). Numerous other possibilities exist. It will also be appreciated by a person skilled in the art that a combination of hardware and software modules may be implemented. Furthermore, various operations, functions or steps of various methods described herein may be performed in parallel rather than sequentially as desired or as appropriate (e g., as long as it does not render the method(s) inoperable or unsatisfactory for its intended purpose).

[0042] In various embodiments, a radar sensing system may be provided. The radar sensing system comprises a radar antenna system and the system 200 for radar sensing as described hereinbefore according to various embodiments of the present invention. FIG. 3 depicts a schematic block diagram of a radar sensing system 300 according to various embodiments of the present invention. The radar sensing system comprises a radar antenna system 312 for receiving communication signals from a communication antenna via a direct channel and a radar reflection channel (after reflecting from one or more objects), and a system 200 as described hereinbefore according to various embodiments of the present invention communicatively coupled (e.g., connected) to the radar antenna 312 for radar sensing. As shown in FIG. 3, the radar antenna system 312 may comprise a first radar antenna 312-1 arranged for receiving the first received communication signal via the direct channel from the communication signal transmitted by the communication antenna; and a second radar antenna 312-2 arranged for receiving the second received communication signal via the radar reflection channel from the communication signal transmitted by the communication antenna. For example, the radar sensing system 300 may also be referred to as a radar receiver. In various embodiments, as described hereinbefore, the radar receiver 300 may be a passive radar receiver.

[0043] FIG. 4 depicts a schematic block diagram of an integrated communication and sensing (ICAS) system 400 according to various embodiments of the present invention. The ICAS system 400 comprises: a communication antenna 322 for transmitting communication signals for wireless communications; a radar antenna system 312 for receiving communication signals from the communication antenna via a direct channel and a radar reflection channel (after reflecting from one or more objects); and a system 200 as described hereinbeforeaccording to various embodiments of the present invention communicatively coupled (e.g., connected) to the radar antenna system 312 for radar sensing. As described hereinbefore, the radar antenna system 312 may comprise a first radar antenna 312-1; and a second radar antenna 312-2. In various embodiments, the system 200 is further communicatively coupled to the communication antenna 312 and further configured to perform wireless communications. In various other embodiments, the wireless communications functions / operations may be controlled / operated using a different computing system / device from the radar sensing functions / operations. For example, the ICAS system 400 may further comprise at least one memory; and at least one processor communicatively coupled to the at least one memory and the communication antenna 322 and configured to perform wireless communications. Importantly, according to various embodiments, the ICAS system 400 is configured to share the same radio signal between radar sensing function / operation and wireless communications function / operation. In various embodiments, the communication antenna 322 (or the communication transmitter) and the radar antenna system 312 (or the radar receiver) are collocated for ICAS. Accordingly, in various embodiments, the system 200 is configured to perform radar sensing as described hereinbefore according to various embodiments of the present invention, as well as to perform wireless communications. Accordingly, the system 200 and the radar antenna 312 together may form or constitute a radar receiver. Furthermore, the system 200, or another computing system / device, together with the communication antenna 322 may form or constitute a communication transmitter (or a communication transceiver). As explained hereinbefore, it will be appreciated by a person skilled in the art that the present invention is not limited to any particular or specific type of communication signals (e g., any particular or specific type of modulation), as long as they are RF communication signals, such as but limited to, 5G-NR signals, OTFS signals or OFDM signals. Accordingly, it will be appreciated by a person skilled in the art that the communication transmitter (or the communication transceiver) may be configured to perform wireless communications according to any wireless communications technique as desired or as appropriate without going beyond the scope of the present invention.

[0044] It will be appreciated by a person skilled in the art that the terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0045] Any reference to an element or a feature herein using a designation such as “first”, “second” and so forth does not limit the quantity or order of such elements or features, unless stated or the context requires otherwise. For example, such designations may be used herein as a convenient way of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not necessarily mean that only two elements can be employed, or that the first element must precede the second element, unless stated or the context requires otherwise. In addition, a phrase referring to “at least one of’ a list of items refers to any single item therein or any combination of two or more items therein.

[0046] In order that the present invention may be readily understood and put into practical effect, various example embodiments of the present invention will be described hereinafter by way of examples only and not limitations. It will be appreciated by a person skilled in the art that the present invention may, however, be embodied in various different forms or configurations and should not be construed as limited to the example embodiments set forth hereinafter. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art

[0047] Both wireless communications and radar sensing occupy precious RF spectrum, which becomes more and more crowded along with increasing demands on high-speed information transmission and dense sensing. To be sustainable and to enhance practical applications, integrated communication and sensing (ICAS) is desired. In this regard, various example embodiments of the present invention provide a radar sensing method, as well as a system thereof (e.g., a radar sensing system or an ICAS system), that seek to overcome, or at least ameliorate, one or more deficiencies in conventional radar sensing methods, and more particularly, with improved efficiency and effectiveness, such as enabling a lower sampling rate and addressing the Tx-Rx self-leakage interference issue. In various example embodiments, during radar sensing, there is no dedicated radar emission except for communication signals, hence saving RF spectrum. Accordingly, there is no interruption to communications operation during radar sensing and no modification to wireless communications protocol is required. Therefore, various example embodiments advantageously enable and employ a passive radar for radar sensing (operates as passive radar mode (listening only without dedicated radaremission)), thereby eliminating the transmitter (Tx) to receiver (Rx) (Tx-Rx) self-leakage interference problem, which various conventional monostatic ICAS systems suffer from. In various example embodiments, the radar sensing method applies or utilizes entire communication signals instead of only pilot / CSI (channel state information), hence enhancing sensing performance in terms of reaction speed (real-time) and SNR (signal-to-noise ratio). Furthermore, in various example embodiments, the radar sensing method samples the received communication signals using dual-channel beat frequency sampling (i.e., both a direct channel (which may also be referred to as a reference channel) which receive the communication signal directly from the communication transmitter (communication antenna)) and a radar reflection channel (which may also be referred to as a surveillance channel) which receives the communication signal from the communication transmitter after being reflected from one or more objects) are subjected to beat frequency sampling), which advantageously enables a lower sampling rate, thereby reducing hardware complexity and power consumption, while still being able to effectively perform radar sensing. For example, the dual-channel beat frequency sampling reduces the sample rate requirement in high resolution radar detection, thereby reducing hardware complexity. Therefore, the method of radar sensing according to various embodiments of the present invention advantageously has improved efficiency and effectiveness. To demonstrate the efficiency and effectiveness of the method of radar sensing according to various embodiments of the present invention, example prototypes using 5G-NR waveform and OTFS waveform (which is a candidate 6G waveform) are constructed for radar sensing as illustrative examples and experimental results thereof will be discussed later below.

[0048] FIG. 5 depicts a schematic block diagram of an ICAS system 500 according to various example embodiments of the present invention. The ICAS system 500 comprises: a communication antenna 522 for transmitting communication signals for wireless communications; a radar antenna system 512 for receiving communication signals from the communication antenna via a direct channel and a radar reflection channel (after reflecting from one or more objects) (e g., the radar antenna system 512 comprises a first radar antenna 512-1 arranged for receiving the first received communication signal via the direct channel from the communication signal transmitted by the communication antenna and a second radar antenna arranged for receiving the second received communication signal via the radar reflection channel from the communication signal transmitted by the communication antenna); and a system 510 communicatively coupled (e.g., connected) to the radar antenna system 512 and configured for radar sensing. In this regard, the system 510 may comprise a radar sensingmodule 530 configured to perform a method of radar sensing according to various example embodiments of the present invention. In this regard, as shown in FIG. 5, the system 510 comprises at least one memory 516; and at least one processor 518 communicatively coupled (e.g., connected) to the at least one memory 516 and configured to perform the method of radar sensing according to various example embodiments of the present invention.

[0049] In various example embodiments, as shown in FIG. 5, the system 510 may further be communicatively coupled to the communication antenna 522 and further configured to perform wireless communications. In this regard, the system 510 may further comprise a communications module 540 configured to perform wireless communications. It will be appreciated by a person skilled in the art that the wireless communications functions / operations and the radar sensing functions / operations may be control led / op erated using the same computing system / device (as illustrated in FIG 5) or using different computing systems / devices. In the ICAS system 500, the communication antenna 522 (or the communication transmitter) and the radar antenna system 512 (or the radar receiver) are collocated for ICAS. In various example embodiments, the system 510 and the radar antenna system 512 (or more specifically, the radar sensing module 530 and the radar antenna system 512) together may form or constitute a radar receiver, and the system 510 and the communication antenna 522 (or more specifically, the communications module 540 and the communication antenna 522) together may form or constitute a communication transmitter (or a communication transceiver) (e.g., a standard or conventional communication transmitter).

[0050] In various example embodiments, the ICAS system 500 may further comprise another communication antenna 552 (or a communication receiver (or transceiver)) for receiving communication signals from the communication antenna 522 for wireless communications. In this regard, the communication receiver may comprise a communications module 556 configured to perform wireless communications. It will be appreciated by a person skilled in the art that the communication antenna 552 may also transmit communication signals to the communication antenna 522. As described hereinbefore, in various example embodiments, the radar receiver is a passive radar receiver that does not emit dedicated radar waveforms, and is configured to just listen in on the communication signal (via a direct channel from the communication antenna 522) and its reflection from the surrounding (via a radar reflection channel from the communication antenna 522 after reflecting from one or more objects / targets). Accordingly, the ICAS system 500 may be referred to as a passive radar based ICAS system.

[0051] Referring to the ICAS system 500 shown in FIG. 5, two received communication signals, and / ?i(t), which may be referred to as a first received communication signal and a second received communication signal, respectively, are received by the radar antenna system 512 from two receiver channels, namely, via a direct channel from a communication signal transmitted by the communication antenna 522 to the radar antenna system 512 (or more particularly, the first radar antenna 512-1) and via a radar reflection channel from the communication signal transmitted by the communication antenna 522 to the radar antenna system 512 (or more particularly, the second radar antenna 512-2) after reflecting from one or more objects / targets.

[0052] Accordingly, the first received communication signal R0(t) may be expressed as:R0(t) = h0(t) *S(t) (Equation 1) where h0(t) denotes an impulse response function of the direct channel from the communication antenna 522 (or communication transmitter) to the radar antenna system 512 (or more particularly, the first radar antenna 512-1, or in general, to the radar receiver), anddenotes a convolution operation. h0(t) is known and can be assumed as an ideal line of sight (LoS) channel, namely, h0(t) = 6(t — T0) where r0is known. Therefore, the first received communication signal R0(t) may also be expressed as:R0(t) - 8(t - T0) * S(t) = S(t - T0) (Equation 2)

[0053] The second received communication signal R1(t) (reflection signal from one or more targets received by radar receiver) may be expressed as:LRi(t) = h(t) * S(t) = alS(t - Tl)(Equation 3) where h(t) denotes the impulse response function of the radar reflection channel from the communication antenna 522 (or in general, from the communication transmitter) to the radar antenna system 512 (or more particularly, the second radar antenna 512-2, or in general, to the radar receiver), and atand r;denote the magnitude and delay of lthpath of the radar target reflection, respectively.

[0054] For example, Equations (1) and (3) may be rewritten as vector format as follows:R0= S' (Equation 4) andRx= HS (Equation 5) R1= [R1(t), ···, R1(t + (N — 1)Δ)]Tdenotes the reflection (or surveillance) channel received signal vector comprising (or having) N equivalent symbol samples with equivalent samplinginterval (sample-symbol interval difference) A (A denotes the difference between the sampling interval and the symbol interval This is because the symbol sequence has a constant symbol repetition interval. After N times of sampling, the sampling location comes back to the same location in the symbol interval, and thus, A may be referred to as the equivalent sampling interval). N denotes the number of samples and T denotes the symbol interval, where N = T / A.S = [s(t), ···, s(t + (N — 1)Δ)]Tdenotes the communication (or transmission) signal vector comprising (or having) N equivalent samples with equivalent sampling duration of A. R0= [R0(t), ···, R0(t + (N — 1)Δ)]Tdenotes the direct (or reference) channel received signal vector comprising (or having) N equivalent samples with equivalent sampling duration of A. [·]Tdenotes transpose, H denotes the channel matrix of the radar reflection channel, and A denotes the discrete time duration of the sample-symbol interval difference (i.e., sampling interval minus symbol interval).

[0055] S' is a version of S delaying K samples where K = [τ0 / Δ] (e.g., for conducting cross correlation, where K denotes the sample index and the real equivalent delay is τ0≈ KΔ). and [■] is a round-off operation, namely, S' ≈ [s(t — KΔ), ···, s(t + (N — K — 1)Δ)]T. Since R1, S and S' are known, H can be solved.

[0056] Key parameters (e g, delay and phase perturbation) in the radar reflection channel H may then be obtained through signal processing. As will be described later below, in various example embodiments, through conducting cross correlation between the received signal vector Rofrom the direct (or reference) channel, and the received signal vector Rxfrom the reflection (or surveillance) channel, various example embodiments determine the object reflection delay(s) (from which the object distance(s) can be derived by multiplying with the speed of light) corresponding to peak(s) in the cross correlation operation. Furthermore, in various example embodiments, by monitoring the phase changing of the cross correlation at a determined peak (along different samples of a determined peak), a displacement of an object can be detected (e g., the fine distance displacement for example due to human body vital sign can be detected if the cross-correlation peak is caused by a reflection from a human body).Beat Frequency Sampling

[0057] Conventionally, one of the most important considerations for radar sensing is that time resolution corresponds to range resolution. In this regard, it is conventionally understood that increasing range resolution needs higher sampling rate. However, higher sampling rate results in higher complexity or cost and higher power consumption, as well as being limited byfabrication. To address or overcome this technical problem, various example embodiments of the present invention advantageously employ or use beat frequency sampling, which significantly reduces the physical sampling rate but with equivalent high discrete time resolution. FIG. 6 depicts a schematic drawing illustrating an example beat frequency sampling of a received communication signal according to various example embodiments of the present invention. In the example beat frequency sampling, let the communication symbol interval be T (i.e., the symbol interval T of the communication signal S(t) transmitted by the communication antenna). At the radar receiver, the physical sampling interval is T + A, which is slightly longer than T, whereby A is a predefined duration that the sampling interval of the received communication signal is longer than the symbol interval of the communication signal S(t). Accordingly, based on the beat frequency sampling, each of the first and second received communication signals R0(t), R^t) is sampled based on a sampling interval T + A that is a predefined duration A longer than a symbol interval T of the communication signal S(t) transmitted by the communication antenna 522. Accordingly, the beat frequency fbbetween the symbol rate of communication signal S(t) (by the communication transmitter) and the sampling rate by the radar receiver may be expressed as:fb= 1 / T − 1 / (T+Δ) = Δ / (T(T+Δ)) (Eq1uation 7) ' It will be appreciated by a person skilled in the art that the sample-symbol interval difference A may be set or configured as appropriate for beat frequency sampling and the present invention is not limited to any specific or particular sample-symbol interval difference A. For example, an example value for A (the number of times the received communication signal must at least be sampled in order to recover or reconstruct one symbol of the received communication signal), which may be equal to T / A, may be the FFT size of the OFDM symbol for wireless communications. In particular, supposing the OFDM FFT size is N in communication, an example value of A may be T / N. However, A may be larger in case the OFDM frame is short, where the number of OFDM symbols is small. In general, the smaller the value of A, the finer the equivalent sampling interval which leads to higher resolution of range detection, and also the larger the required number of symbols in communication frame.

[0058] In various example embodiments, the beat frequency fbmay be set as follows:fb= 1 / (TN) (Equation s)

[0059] Accordingly, based on the beat frequency sampling, each of the first and second received communication signals R0(t), R1(t) is sampled at least a determined number of times A, whereby the determined number of times A is determined based on a beat frequency fbbetween the symbol rate 1 / T of the communication signal transmitted S(t) by the communication antenna 522 and the sampling rate l / ( T + A) (corresponding to the sampling interval T + A).

[0060] Therefore, one complete symbol can be recovered or reconstructed after N sampling. As a result, according to various example embodiments, N X high time resolution can be achieved with symbol level sampling. Accordingly, in various example embodiments, the sampling rate is advantageously significantly reduced to symbol level, thereby significantly reducing hardware complexity and power consumption, while still being able to effectively perform radar sensing, thereby enhancing practical applications, such as but not limited to, enabling implementation even in edge devices. In various example embodiments, the beat frequency sampling is suitable only for the communication signal parameter (waveform except information bits) having no change in at least N sequential symbols (the communication frame includes at least N sequential symbols). For example, in 5GNR, a frame contains 140 to 2240 symbols, and thus, the condition of no change in at least N sequential symbols can be easily applied in practical applications.Range Estimation

[0061] Through the beat frequency sampling of the first and second received communication signals R0(t), Rx(t), in various example embodiments, sampled first and second received communication signals Roand Rxare obtained. In this regard, in various example embodiments, sampled first and second received communication signals Roand Rx, each with N sequential equivalent samples are obtained. The adjacent time difference is A (equivalent sampling interval).

[0062] Accordingly, each of the first and second received communication signals R0(t), R1(t) is sampled based on the beat frequency sampling to obtain sampled first and second received communication signals Ro, Rx. In this regard, the sampled first received communication signal Rois a first received signal vector comprising a sequence of first symbol samples (which may be referred to as first equivalent symbol samples) obtained from sampling the first received communication signal R0(t) based on the beat frequency sampling for the determined number of times N. Similarly, the sampled second received communication signal Rxis a second received signal vector comprising a sequence of second symbol samples (which may be referred to as second equivalent symbol samples) obtained from sampling the second received communication signal R^t) based on the beat frequency sampling for the determinednumber of times N. For example, the sequence of first symbol samples may be referred to as a sequence of first equivalent symbol samples as these first equivalent symbol samples obtained from sampling the first received communication signal R0(t) the determined number of times N are collectively equivalent to one symbol (to recover or reconstruct one symbol) of the first received communication signal R0(t). Similarly, for example, the sequence of second symbol samples may be referred to as a sequence of second equivalent symbol samples as these second equivalent symbol samples obtained from sampling the second received communication signal R1(t) the determined number of times N are collectively equivalent to one symbol (to recover or reconstruct one symbol) of the second received communication signal R1(t).

[0063] In various example embodiments, a cross correlation of the sampled first and second received communication signals R0, R1is determined. For example, a cross correlation operation of the two channel signals R0, R1may be conducted as follows:CRR(x) = [S(x)R0]HR1(Equation 9) where x denotes the delay index in the cross-correlation calculation and where [-]Hdenotes conjugate transpose, androw 1 [0 0S(x) = row x 1 0 0 (Equation 10)1 0 1 0row Ni-Q Q 1- NIn Equation (10), S(x) functions as a down-shifting operator and when applied in Equation (9), it down-shifts Roby x elements. Meanwhile, S(x) pads x - 1 zeros in the upper part of the new Ro. In this regard, S(x) consists of 0’s and l’s only and has no physical correspondence for each row.

[0064] In various example embodiments, the dominant path delay rdmay be determined as follows:τd= (arg max|CRR(x)| + K)Δ (Equation 11)In Equation (11), K is a system hardware caused bias, which, for example, can be found in the system calibration by comparing the real object range and the measured object range. Since x denotes the discrete sample index, the real delay is equal to the index x equivalent sampling interval.

[0065] After finding the path delay Td, the distance D from the obj ect (or target) to the radar receiver (or more specifically, the radar antenna system 512) may be obtained by multiplyingthe path delay Tdwith the speed of light c divided by 2 (assuming that the communication antenna 522 and the radar antenna system 512 are collocated for 1CAS) as follows.D = Tdcj2 (Equation 12)

[0066] Accordingly, in various example embodiments, the distance D between the radar antenna system 512 and the object may be determined based on the cross correlation CRRo(x) of the sampled first and second received communication signals Ro, Ri. In this regard, a peak of the cross correlation CRR(x) of the sampled first and second received communication signals Ro, Rj corresponding to the object may be determined. The distance D between the radar antenna system 512 and the object may then be determined based on the determined peak xdof the cross correlation CRRo(xd) corresponding to the object. In this regard, a path delay Tdof the second received communication signal associated with the object may be determined based on the determined peak xdof the cross correlation CRRo(xd) corresponding to the object; and the distance D between the radar antenna system 512 and the object may then be determined based on the path delay rdassociated with the object.

[0067] In various example embodiments, if there are multiple radar target reflections, their corresponding path delays can be determined by finding other peaks of the cross correlation CRR(x) corresponding to other radar target reflections besides the global maximum, for example, the second local maximum (a peak corresponding to a second object), the third local maximum (a peak corresponding to a third object) and so on of the cross correlation CRR(x) corresponding to other targets / objects. In particular, for each of the plurality of targets / objects, a peak of the cross correlation CRRo(x) corresponding to the object may be determined. Furthermore, for each of the plurality of targets / objects, a path delay Tdof the second received communication signal associated with the object may be determined based on the determined peak of the cross correlation CRRo(x) corresponding to the object, and the distance between the radar antenna system 512 and the object may be determined based on the path delay Tdassociated with the object.Vital Sign Detection

[0068] In various example embodiments, a displacement of an object may be determined based on the cross correlation CRR(x) of the sampled first and second received communication signals R0, R1In this regard, a phase change of the cross correlation CRRo(d) of the sampled first and second received communication signals Ro, Rtat the determined peakxdcorresponding to the object over time may be determined, and the displacement of the object may thus be determined based on the phase change of the cross correlation CRR(xd) at the determined peak xdcorresponding to the object over time.

[0069] For example, a displacement of an object may be determined according to:v(t) = ∠CRR(xd) (Equation 13) where ∠(·) denotes phase in degree of a complex number, xddenotes the index of the peak of the CRRofunction in Equation (9) corresponding to the object. CRRo(x) is a complex number determined by its magnitude and phase. In this regard, in various example embodiments, when the absolute value of CRRo(x) (namely | CRRo(x) |) that reaches the maximum is found, the index of the peak xdis fixed, and the phase change of the cross correlation CRR(xd) at the determined peak xdis monitored over time, which corresponds to the object displacement.

[0070] If there are multiple targets / objects, their corresponding displacements can be determined by finding other peaks of the cross correlation CRR(x) corresponding to other radar target reflections besides the global maximum, for example, the second local maximum (a peak corresponding to a second object), the third local maximum (a peak corresponding to a third object) and so on of the cross correlation CRRo(x) corresponding to other targets / objects. In particular, for each of the plurality of targets / objects, a peak of the cross correlation CRR(x) corresponding to the object may be determined. Furthermore, for each of the plurality of targets / objects, a phase change of the cross correlation CRR(x) at the determined peak corresponding to the object over time may be determined, and the displacement of the object may then be determined based on the phase change of the cross correlation CRR(x) at the determined peak corresponding to the object over time.

[0071] As an illustrative example practical application and without limitation, the method of radar sensing for determining a displacement of an object may be applied to detect a human vital sign such as breathing, whereby it is necessary to detect tiny displacements. For example, there may be a distance perturbation of about ±2.5 mm at a target (human body) on its range in about 0.3Hz frequency caused by breathing.

[0072] In various example embodiments, in the radar signal processing, after detecting the peak of CRR(x) at 1 meter, the phase change may then be further monitored, which corresponds to the distance displacement.

[0073] FIG. 7 depicts a flow diagram of an example method 700 of radar sensing according to various example embodiments of the present invention. As can be seen from FIG. 7, in various example embodiments, it may be determined whether the determined distance between the radar antenna system 512 and a target (determined as described hereinbefore according to various example embodiments) satisfies a predefined distance threshold condition (e g, whether at 1 meter). In this regard, if it is determined that the determined distance between the radar antenna 512 and the target satisfies the predefined distance threshold condition, a displacement of the target may then be determined as described hereinbefore according to various example embodiments. It will be appreciated by a person skilled in the art that the present invention is not limited to any specific or particular distance threshold condition for determining whether to proceed with determining a displacement of the object, which may be defined or set as desired or as appropriate, such as and not limited to, based on a specific distance value (e.g., if the determined distance is larger than or equal to the defined distance value) or a range of threshold values (e.g., if the determined distance is within the defined range of distance values).Example ImplementationsWith 5G-NR Waveform (OFDM)

[0074] FIG. 8 shows the simulation results of radar target range estimation with standard communication waveform of 5G-NR: OFDM signal, 1024 subcarriers; 1024 random 256-QAM symbols; signal bandwidth 100MHz. Since 5MHz guard band is set on both sides, the effective bandwidth is 90MHz. The ground truth radar target ranges are 1 meter and 15 meters respectively. Therefore, FIG. 8 shows the simulation of 5G-NR waveform for radar sensing (OFDM signal; 1024 subcarriers 1024 random 256-QAM symbols; signal bandwidth 100MHz; Guard band=5MHz; radar targets Im and 15 m). From FIG. 8, two peaks can be observed, namely, at 1 meter and 15 meters, in distance axis in the radar estimation.

[0075] FIG. 9 shows the simulation of vital sign detection of the human target in 1 meter distance. The human target has a distance perturbation of ±2.5 mm. Therefore, FIG 9 shows displacement / vital sign detection with 5G-NR waveform (target 1 at Im with ±2.5 mm perturbation in speed of 0.2 Hz It can be observed that through monitoring the phase of the cross-correlation function in Equation (9) at the peak for the target at 1 meter, small displacements of the target can clearly detected.With OTFS Waveform

[0076] The orthogonal time frequency and space (OTFS) is a candidate for next-generation communication waveform having robust performance in high mobility (large Doppler shift) environments. As an illustrative example, OTFS waveform is utilized for radar sensing. The OTFS waveform generation is shown in FIG. 10, which is based on discrete Zak transformation. In particular, FIG. 10 shows the simulation results of radar target range estimation with OTFS waveform; the delay domain size M=1024 and the Doppler domain size N=1024 too. The data is random 256-QAM symbol at each point in delay-Doppler plane. Signal bandwidth 100MHz; No guard band; radar targets Im and 15 m. Because there is no guard band applied, the signal spectrum can be 100MHz. The range estimations for two radar targets are similar as than with 5G-NR signal.

[0077] FIG. 11 shows simulation of OTFS waveform for radar sensing (OTFS signal; M=1024 in delay domain, N=1024 in Doppler domain, random 256-QAM at each point in delay-Doppler domain; signal bandwidth 100MHz; Guard band=5MHz; radar targets Im and 15 m). FIG. 12 shows displacement / vital sign detection with OTFS waveform (target 1 at Im with ±2.5mm perturbation in speed of 0.2 Hz).Example Prototype

[0078] FIG. 13 depicts a schematic block diagram of an example experimental prototype with a software defined radio platform. In particular, the radar sensing method according to various example embodiments of the present invention is prototyped with a software defined radio platform for 5G-NR and OTFS waveforms. The standard 5G-NR and OFTS waveforms are used, respectively, in the setup for human body breathing detection.

[0079] While embodiments of the invention have been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

CLAIMS1. A method of radar sensing comprising:obtaining a first received communication signal and a second received communication signal received by a radar antenna system, wherein the first received communication signal is received via a direct channel from a communication signal transmitted by a communication antenna to the radar antenna system and the second received communication signal is received via a radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from an object;sampling each of the first and second received communication signals based on beat frequency sampling to obtain sampled first and second received communication signals, determining a cross correlation of the sampled first and second received communication signals; anddetermining a distance between the radar antenna system and the object and / or a displacement of the object based on the cross correlation of the sampled first and second received communication signals.

2. The method according to claim 1, wherein based on the beat frequency sampling, each of the first and second received communication signals is sampled based on a sampling interval that is a predefined duration longer than a symbol interval of the communication signal transmitted by the communication antenna.

3. The method according to claim 2, wherein based on the beat frequency sampling, each of the first and second received communication signals is sampled at least a determined number of times, wherein the determined number of times is determined based on a beat frequency between a symbol rate of the communication signal transmitted by the communication antenna and a sampling rate corresponding to the sampling interval.

4. The method according to claim 3, wherein the sampling rate is at symbol level.

5. The method according to claim 3 or 4, whereinthe sampled first received communication signal comprises a first received signal vector comprising a sequence of first symbol samples obtained from said sampling the first receivedcommunication signal based on the beat frequency sampling for the determined number of times, andthe sampled second received communication signal comprises a second received signal vector comprising a sequence of second symbol samples obtained from said sampling the second received communication signal based on the beat frequency sampling for the determined number of times.

6. The method according to any one of claims 1 to 5, further comprises determining a peak of the cross correlation of the sampled first and second received communication signals corresponding to the object, wherein the distance between the radar antenna system and the object or the displacement of the object is determined based on the determined peak of the cross correlation corresponding to the object.

7. The method according to claim 6, wherein said determining a distance between the radar antenna system and the object comprises:determining a path delay of the second received communication signal associated with the object based on the determined peak of the cross correlation corresponding to the object; anddetermining the distance between the radar antenna system and the object based on the path delay associated with the object.

8. The method according to any one of claims 1 to 5, whereinthe second received communication signal is received via the radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from a plurality of objects,the method further comprises determining, for each of the plurality of objects, a peak of the cross correlation of the sampled first and second received communication signals corresponding to the object, andfor each of the plurality of objects, said determining a distance between the radar antenna system and the object comprises:determining a path delay of the second received communication signal associated with the object based on the determined peak of the cross correlation corresponding to the object; anddetermining the distance between the radar antenna system and the object based on the path delay associated with the object.

9. The method according to claim 6, wherein said determining a displacement of the object comprises:determining a phase change of the cross correlation of the sampled first and second received communication signals at the determined peak corresponding to the object over time; anddetermining the displacement of the object based on the phase change of the cross correlation at the determined peak corresponding to the object over time.

10. The method according to any one of claims 1 to 5, whereinthe second received communication signal is received via the radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from a plurality of objects,the method further comprises determining, for each of the plurality of objects, a peak of the cross correlation of the sampled first and second received communication signals corresponding to the object, andfor each of the plurality of objects, said determining a displacement of the object comprises:determining a phase change of the cross correlation of the sampled first and second received communication signals at the determined peak corresponding to the object over time; anddetermining the displacement of the object based on the phase change of the cross correlation at the determined peak corresponding to the object over time.

11. The method according to any one of claims 1 to 10, further comprises determining whether the determined distance between the radar antenna system and the object satisfies a predefined distance threshold condition, wherein said determining a displacement of the object is performed based on determining that determined distance between the radar antenna system and the object satisfies the predefined distance threshold condition.

12. The method according to any one of claims 1 to 11, wherein the radar antenna system comprises:a first radar antenna arranged for receiving the first received communication signal via the direct channel from the communication signal transmitted by the communication antenna; anda second radar antenna arranged for receiving the second received communication signal via the radar reflection channel from the communication signal transmitted by the communication antenna.

13. The method according to any one of claims 1 to 12, whereinthe communication antenna and the radar antenna system are collocated for integrated communication and sensing (ICAS), andthe radar antenna system is of a passive radar receiver.

14. A system for radar sensing comprising:at least one memory; andat least one processor communicatively coupled to the at least one memory and configured to:obtain a first received communication signal and a second received communication signal received by a radar antenna system, wherein the first received communication signal is received via a direct channel from a communication signal transmitted by a communication antenna to the radar antenna system and the second received communication signal is received via a radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from an object;sample each of the first and second received communication signals based on beat frequency sampling to obtain sampled first and second received communication signals; determine a cross correlation of the sampled first and second received communication signals; anddetermine a distance between the radar antenna system and the object and / or a displacement of the object based on the cross correlation of the sampled first and second received communication signals.

15. The system according to claim 14, wherein based on the beat frequency sampling, each of the first and second received communication signals is sampled based on a sampling interval that is a predefined duration longer than a symbol interval of the communication signal transmitted by the communication antenna.

16. The system according to claim 15, wherein based on the beat frequency sampling, each of the first and second received communication signals is sampled at least a determined number of times, wherein the determined number of times is determined based on a beat frequency between a symbol rate of the communication signal transmitted by the communication antenna and a sampling rate corresponding to the sampling interval.

17. The system according to claim 16, wherein the sampling rate is at symbol level.

18. The system according to claim 16 or 17, whereinthe sampled first received communication signal comprises a first received signal vector comprising a sequence of first symbol samples obtained from said sampling the first received communication signal based on the beat frequency sampling for the determined number of times, andthe sampled second received communication signal comprises a second received signal vector comprising a sequence of second symbol samples obtained from said sampling the second received communication signal based on the beat frequency sampling for the determined number of times.

19. The system according to any one of claims 14 to 18, wherein at least one processor is further configured to determine a peak of the cross correlation of the sampled first and second received communication signals corresponding to the object, wherein the distance between the radar antenna system and the object or the displacement of the object is determined based on the determined peak of the cross correlation corresponding to the object.

20. The system according to claim 19, wherein said determine a distance between the radar antenna system and the object comprises:determining a path delay of the second received communication signal associated with the object based on the determined peak of the cross correlation corresponding to the object; anddetermining the distance between the radar antenna system and the object based on the path delay associated with the object.

21. The system according to any one of claims 14 to 18, whereinthe second received communication signal is received via the radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from a plurality of objects,at least one processor is further configured to determine, for each of the plurality of objects, a peak of the cross correlation of the sampled first and second received communication signals corresponding to the object, andfor each of the plurality of objects, said determine a distance between the radar antenna system and the object comprises:determining a path delay of the second received communication signal associated with the object based on the determined peak of the cross correlation corresponding to the object; anddetermining the distance between the radar antenna system and the object based on the path delay associated with the object.

22. The system according to claim 19, wherein said determine a displacement of the object comprises:determining a phase change of the cross correlation of the sampled first and second received communication signals at the determined peak corresponding to the object over time; anddetermining the displacement of the object based on the phase change of the cross correlation at the determined peak corresponding to the object over time.

23. The system according to any one of claims 14 to 18, whereinthe second received communication signal is received via the radar reflection channel from the communication signal transmitted by the communication antenna to the radar antenna system after reflecting from a plurality of objects,at least one processor is further configured to determine, for each of the plurality of objects, a peak of the cross correlation of the sampled first and second received communication signals corresponding to the object, andfor each of the plurality of objects, said determine a displacement of the object comprises:determining a phase change of the cross correlation of the sampled first and second received communication signals at the determined peak corresponding to the object over time; anddetermining the displacement of the object based on the phase change of the cross correlation at the determined peak corresponding to the object over time.

24. The system according to any one of claims 14 to 23, wherein the at least one processor is further configured to determine whether the determined distance between the radar antenna system and the object satisfies a predefined distance threshold condition, wherein said determine a displacement of the object is performed based on determining that determined distance between the radar antenna system and the object satisfies the predefined distance threshold condition.

25. The system according to any one of claims 14 to 24, wherein the radar antenna system comprises:a first radar antenna arranged for receiving the first received communication signal via the direct channel from the communication signal transmitted by the communication antenna; anda second radar antenna arranged for receiving the second received communication signal via the radar reflection channel from the communication signal transmitted by the communication antenna26. The system according to any one of claims 14 to 25, whereinthe communication antenna and the radar antenna system are collocated for integrated communication and sensing (ICAS), andthe radar antenna system is of a passive radar receiver27. An integrated communication and sensing (ICAS) system comprising:a communication antenna for transmitting communication signals for wireless communications;a radar antenna system for receiving communication signals from the communication antenna via a direct channel and a radar reflection channel; anda system according to any one of claims 11 to 19 communicatively coupled to the radar antenna system for radar sensing.

28. The ICAS system according to claim 27, whereinthe system for radar sensing is further communicatively coupled to the communication antenna and further configured to perform wireless communications, orthe ICAS system further comprises at least one memory, and at least one processor communicatively coupled to the at least one memory and the communication antenna and configured to perform wireless communications.

29. A computer program product, embodied in one or more non-transitory computer-readable storage mediums, comprising instructions executable by at least one processor to perform the method of radar sensing according to any one of claims 1 to 13.

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