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Integrated Sensing and Communication (ISAC) refers to the design paradigm and corresponding enabling technologies that combine sensing and communication systems to utilize wireless resources efficiently and potentially avail of their mutual benefits. The rationale behind ISAC is that radio signals could simultaneously convey communication data from the transmitter to the receiver as well as be used to infer information from the physical environment. Therefore, ISAC acquires two main advantages over dedicated sensing and communication functionalities: 1) Integration Gain to efficiently utilize congested resources, and even more interestingly, 2) Coordination Gain to balance dual-functional performance or/and perform mutual assistance. That is, via the shared use of spectral and hardware resources, ISAC can be realized through a synergistic design to pursue integration gain, e.g., cohabitation strategies with interference management. Moreover, it can also be implemented from a co-design perspective, wherein the communications and sensing functionalities are simultaneously performed via unified waveforms to optimize the performance for coordination gain. Benefiting from these two attributes, ISAC has been well-recognized as a key technology for next-generation wireless networks, namely, 5G-Advanced and 6G.

This collection of Best Readings provides a panorama of ISAC, including recent advances and applications in information theory, signal processing, mobile computing, aerospace and electronic systems, and vehicular technology/intelligent transportation systems. To this end, the reading list includes four special issues and links to four web-based resources that are all dedicated to ISAC. The overview section aims to provide a systemic view for newcomers. The Best Readings then organizes the most active topics within this field into twelve categories, including fundamental theory, physical layer designs, spectrum sharing solutions, networking technologies, security aspects, applications, and demonstrations. The guest editors hope that this list will provide valuable references for all researchers working in the area of ISAC.

Issued: February 2022


Fan Liu, Southern University of Science and Technology, China
Yuanhao Cui, Beijing University of Posts and Telecommunications, China
J. Andrew Zhang, University of Technology Sydney, Australia
Weijie Yuan, Southern University of Science and Technology, China
Christos Masouros, University College London, UK
Taneli Riihonen, Tampere University, Finland

Jie Xu, The Chinese University of Hong Kong, Shenzhen, China
Tony Xiao Han, Huawei Technologies Co. Ltd.
Athina Petropulu, Rutgers University, USA
Visa Koivunen, Aalto University, Finland
Yonina C. Eldar, Weizmann Institute of Science, Israel

Editorial Staff

Matthew C. Valenti
Editor-in-Chief, ComSoc Best Readings
West Virginia University
Morgantown, WV, USA

Xianbin Wang
Associate Editor-in-Chief, ComSoc Best Readings
Western University
London, ON, Canada


F. Liu, C. Masouros, A. P. Petropulu, H. Griffiths, and L. Hanzo, Joint Radar and Communication Design: Applications, State-of-the-Art, and the Road Ahead, IEEE Transactions on Communications, vol. 68, no. 6, pp. 3834-3862, June 2020.
This paper provides an overview of radar-communication coexistence and dual-functional radar-communication (DFRC) systems, with a particularly good introduction on application scenarios and technical approaches. It also presents a novel transceiver architecture and frame structure for a DFRC base station operating in the millimeter wave band, using the hybrid analog-digital beamforming technique.

J. A. Zhang, F. Liu, C. Masouros, R. W. Heath, Z. Feng, L. Zheng, and A. Petropulu, An Overview of Signal Processing Techniques for Joint Communication and Radar Sensing, IEEE Journal of Selected Topics in Signal Processing, vol. 15, no. 6, pp. 1295-1315, November 2021.
This is a comprehensive overview of the state-of-the-art on joint communication and radar sensing (JCR) systems from the signal processing perspective. A balanced coverage of both transmitters and receivers is provided for three types of JCR systems, namely, communication-centric, radar/sensing-centric, and joint design and optimization.

C. Sturm and W. Wiesbeck, Waveform Design and Signal Processing Aspects for Fusion of Wireless Communications and Radar Sensing, Proceedings of the IEEE, vol. 99, no. 7, pp. 1236-1259, July 2011.
This is one of the earliest papers that proposes an approach for realizing communication-centric ISAC systems. Sensing parameter estimation is discussed for single carrier signals, which are primarily direct sequence spread spectrum, and for OFDM signals, in both SISO and MIMO systems. Simulation and experimental results are provided and validate the concept of communication-centric ISAC.

Y. Cui, F. Liu, X. Jing, and J. Mu, Integrating Sensing and Communications for Ubiquitous IoT: Applications, Trends, and Challenges, IEEE Network, vol. 35, no. 5, pp. 158-167, September/October 2021.
This paper systemically describes the vision and the definition of integrated sensing and communications, based on the layer in which integration is applied. The architectural evolution of ubiquitous IoT devices is discussed in detail. This paper provides a primary starting point for new researchers and offer a bird’s-eye view of existing ISAC-related advances.

D. Ma, N. Shlezinger, T. Huang, Y. Liu, and Y. C. Eldar, Joint Radar-Communication Strategies for Autonomous Vehicles: Combining Two Key Automotive Technologies, IEEE Signal Processing Magazine, vol. 37, no. 4, pp. 85-97, July 2020.
This paper reviews ISAC technologies in the scope of vehicular networks. It first discusses the characteristics of automotive radar technologies and their combination with communications from the requirements of self-driving cars. Then, both communication-centric and radar-centric signal models are reviewed, together with a brief introduction of receiver design and future research problems. The introduction to radar-centric design, particularly the frequency-agile radar and index modulation, is a highlight.

L. Zheng, M. Lops, Y. C. Eldar, and X. Wang, Radar and Communication Coexistence: An Overview: A Review of Recent Methods, IEEE Signal Processing Magazine, vol. 36, no. 5, pp. 85-99, September 2019.
This paper provides an overview of coexisting, cooperative, and joint ISAC systems, although they are named differently. The introductions on system and signal models are particularly good, and a review of related waveform design and signal processing techniques is also provided.

K. V. Mishra, M. R. Bhavani Shankar, V. Koivunen, B. Ottersten, and S. A. Vorobyov, Toward Millimeter-Wave Joint Radar Communications: A Signal Processing Perspective, IEEE Signal Processing Magazine, vol. 36, no. 5, pp. 100-114, September 2019.
This paper provides a signal processing perspective of mm-wave ISAC systems with an emphasis on waveform design. It covers both coexistence and co-design, with a focus on the latter. Both radar-centric and communication-centric waveform designs are reviewed, with detailed mathematical models presented. It presents a good comparison between phase-modulated continuous-wave and OFDM ISAC systems.

Special Issues

Special Issue on Co-operation and Joint Design of Communications and Radar Systems in a Crowded Spectrum,” Digital Signal Processing, 2018.

Special Issue on “Spectrum Sharing,” IEEE Transactions on Aerospace and Electronics Systems, June 2019.

Special Issue on “Joint Communication and Radar Sensing for Emerging Applications,” IEEE Journal of Selected Topics in Signal Processing, November 2021.

Special Issue on “Integrated Sensing and Communication,” IEEE Journal on Selected Areas in Communications, 2022.

Topic: Fundamental Theory and Performance Analysis

M. Kobayashi, G. Caire, and G. Kramer, Joint State Sensing and Communication: Optimal Tradeoff for a Memoryless Case,in Proc., IEEE International Symposium on Information Theory (ISIT), Vail, CO, USA, June 2018, pp. 111-115.
This paper investigates a basic ISAC model from an information-theoretical perspective. The radar sensing channel is modeled as a delayed feedback channel between the ISAC transmitter and the target, and the sensing performance is evaluated by a generic distortion metric. Then the optimal capacity-distortion tradeoff is characterized as the Pareto frontier between the achievable communication rate and the minimum distortion.

A. R. Chiriyath, B. Paul, G. M. Jacyna, and D. W. Bliss, Inner Bounds on Performance of Radar and Communications Co-Existence,” IEEE Transactions on Signal Processing, vol. 64, no. 2, pp. 464-474, January 2016.
This paper is the first attempt to define an information metric for the radar sensing procedure, namely the estimation rate, which is defined as the cancellation of the uncertainty in radar target estimation per second, with the Cramér-Rao bound (CRB) as the minimum achievable uncertainty. The tradeoff between estimation rate and communication rate is studied given different resource allocation strategies.

Q. He, Z. Wang, J. Hu, and R. S. Blum, Performance Gains from Cooperative MIMO Radar and MIMO Communication Systems,” IEEE Signal Processing Letters, vol. 26, no. 1, pp. 194-198, January 2019.
This paper considers a coexistence scenario between a MIMO radar and a distributed MIMO communication system, where the radar estimation CRB and the communication mutual information (MI) are derived, under the assumption that the communication and radar systems are mutually assisted by each other. Tradeoffs between radar and communication are illustrated for both cooperative and uncooperative scenarios.

S. Fortunati, L. Sanguinetti, F. Gini, M. S. Greco, and B. Himed, Massive MIMO Radar for Target Detection,” IEEE Transactions on Signal Processing, vol. 68, pp. 859-871, 2020.
This paper provides the first rigorous analysis of using a massive MIMO (mMIMO) system to detect a target. Closed-form expressions for false-alarm and detection probabilities are derived for the asymptotic regime; i.e., where the numbers of transmit and receive antennas go to infinity. The paper’s main results show that the mMIMO radar is able to reach given performance requirements with only a single snapshot, in the presence of unknown disturbance statistics.

Y. Cui, V. Koivunen, and X. Jing, A Perspective on Degrees of Freedom for Radar in Radar-Communication Interference Channel,” in Proc., Asilomar Conference on Signals, Systems, and Computers, Pacific Grove, CA, October 2018, pp. 403-408.
This paper is the first attempt to investigate the mathematical structure of the degrees of freedom (DoF) for radar. A definition of DoF for radar using Rényi information dimension is proposed. The single-user DoF upper bound is established as well.

F. Liu, Y. -F. Liu, A. Li, C. Masouros, and Y. C. Eldar, Cramér-Rao Bound Optimization for Joint Radar-Communication Beamforming,IEEE Transactions on Signal Processing, vol. 70, pp. 240-253, January 2022.
This paper reveals an interesting performance tradeoff between communication and radar sensing in an MU-MIMO downlink ISAC system, where a unified waveform is designed to minimize the Cramér-Rao Bound (CRB) for both point and extended target estimation, under individual SINR constraints for each communication user. Both theoretical analysis and numerical results show that the proposed ISAC design reaches the Pareto-optimal boundary for communication and sensing performance.

Topic: PHY: Communication-Centric Design

C. Baquero Barneto, T. Riihonen, M. Turunen, et al., “Full-Duplex OFDM Radar With LTE and 5G NR Waveforms: Challenges, Solutions, and Measurements,” IEEE Transactions on Microwave Theory and Techniques, vol. 67, no. 10, pp. 4042-4054, October 2019.
This paper studies sensing problems with OFDM LTE and 5G New Radio (NR) mobile signals. Actual subcarrier allocations are considered, and linear interpolation is introduced to obtain regular observations such that the periodogram method can be used for sensing parameter estimation. Self-interference cancellation methods are studied to enable sensing receiver collocated with the transmitter. Experimental results are provided and validate the proposed methods.

S. D. Liyanaarachchi, T. Riihonen, C. B. Barneto, and M. Valkama, Optimized Waveforms for 5G-6G Communication with Sensing: Theory, Simulations and Experiments,IEEE Transactions on Wireless Communications, vol. 20, no. 12, pp. 8301-8315, December 2021.
This paper investigates joint communication and sensing techniques with OFDM signals, where a full-duplex transceiver is leveraged both for mono-static radar sensing and wireless communications. In particular, power and phase optimization for OFDM subcarriers are considered to minimize the Cramér-Rao bound (CRB) for delay and Doppler estimation, and the peak-to-average power ratio (PAPR), respectively. Both numerical and experimental results are given to prove the effectiveness of the proposed technique.

P. Kumari, J. Choi, N. González-Prelcic, and R.W. Heath, “IEEE 802.11 ad-based Radar: An Approach to Joint Vehicular Communication-Radar System,” IEEE Transactions on Vehicular Technology, vol. 67, no. 4, pp. 3012-3027, April 2017.
This paper develops and provides an in-depth analysis of an IEEE 802.11ad-based radar system for the 60 GHz band, enabling a joint waveform for automotive radar and vehicular communications based on the mmWave local area network standard. Both single- and multi-frame radar receiver algorithms are proposed for target detection and parameter estimation.

A. Ali, N. Gonzalez-Prelcic, R. W. Heath, and A. Ghosh, “Leveraging Sensing at the Infrastructure for MmWave Communication,” IEEE Communications Magazine, vol. 58, no. 7, pp. 84-89, July 2020.
This magazine article motivates the use of the sensors mounted on infrastructure to aid the establishment and maintenance of the mmWave communication links. Numerical and measurement results are provided to demonstrate that information from these infrastructure sensors can help to reduce the antenna array configuration overhead.

M. F. Keskin, V. Koivunen, and H. Wymeersch, “Limited Feedforward Waveform Design for OFDM Dual-Functional Radar-Communications,” IEEE Transactions on Signal Processing, vol. 69, pp. 2955-2970, 2021.
This paper considers an OFDM dual-function radar-communications (DFRC) system that communicates with an OFDM receiver while simultaneously estimating target parameters using the backscattered signals. The goal is to achieve a favorable performance trade-off between radar and communications by optimizing subcarrier powers in a time-frequency region of interest, under radar similarity constraints. Simulation results show that the proposed approach provides significant performance gains and achieves a near-optimal tradeoff between radar and communications performance.

Topic: PHY: Sensing-Centric Design

G. N. Saddik, R. S. Singh, and E. R. Brown, Ultra-Wideband Multifunctional Communications/Radar System,IEEE Transactions on Microwave Theory and Techniques, vol. 55, no. 7, pp. 1431-1437, July 2007.
This paper represents the early effort to embed communication data into the radar waveform by inter-pulse modulation (slow-time coding), where the up- and down-chirp carriers are exploited for communication and radar functionalities, respectively. Thanks to the quasi-orthogonality between the up and down-chirp signals, the interference between radar and communication signals is relatively low in general.

X. Chen, X. Wang, S. Xu, and J. Zhang, A Novel Radar Waveform Compatible with Communication,in Proc., International Conference on Computational Problem-Solving (ICCP), Chengdu, China, October 2011, pp. 177-181.
This paper attempts to embed communication data into the radar waveform by inner-pulse modulation (fast-time coding). The proposed scheme modulates the communication symbols onto the chirp signal via minimum shift keying (MSK) modulation. The resultant Chirp-MSK waveform possesses the attributes of constant envelope and continuous phase, which also shows superior performance in terms of the thumbtack-like ambiguity function.

A. Hassanien, M. G. Amin, Y. D. Zhang, and F. Ahmad, Dual-Function Radar-Communications: Information Embedding Using Sidelobe Control and Waveform Diversity,” IEEE Transactions on Signal Processing, vol. 64, no. 8, pp. 2168-2181, April 2016.
This paper proposes the first spatial information-embedding scheme for MIMO radar-communication systems. The scheme detects targets using the mainlobe of the MIMO radar beampattern and transmits information through controlling its sidelobes, where various modulation formats, including ASK and PSK can be readily applied.

T. Huang, N. Shlezinger, X. Xu, Y. Liu, and Y. C. Eldar, MAJoRCom: A Dual-Function Radar Communication System Using Index Modulation,IEEE Transactions on Signal Processing, vol. 68, pp. 3423-3438, May 2020.
This paper provides a new way of embedding information into the radar waveform through index modulation. It considers a frequency-agile phased-array radar system, where the inherent spectral and spatial randomness is exploited to convey digital messages via the specific combination of antenna and frequency indices. By doing so, a reasonable communication rate is achieved without affecting the radar sensing performance.

K. Wu, J. A. Zhang, X. Huang, Y. J. Guo, and R. W. Heath, Waveform Design and Accurate Channel Estimation for Frequency-Hopping MIMO Radar-Based Communications,” IEEE Transactions on Communications, vol. 69, no. 2, pp. 1244-1258, February 2021.
In this paper, the communication functionality is implemented over a frequency-hopping MIMO radar, where the useful information is embedded into the combination of different hopping frequencies. A communication receiver is developed to accurately decode the hopping frequency sequence (HFS), as well as to estimate the timing offset and the communication channel. Satisfactory communication performance is achieved without deteriorating the ranging performance of the radar.

Topic: PHY: Joint Design

F. Liu, C. Masouros, A. Li, H. Sun, and L. Hanzo, MU-MIMO Communications with MIMO Radar: From Co-Existence to Joint Transmission,” IEEE Transactions on Wireless Communications, vol. 17, no. 4, pp. 2755-2770, April 2018.
This paper investigates joint radar-communication beamforming design under two different system settings. The first one is called separated deployment, where the antenna array is separated into radar and communication antennas, respectively, in which case mutual interference occurs between the two sub-arrays. The second one is called shared deployment, where the whole antenna array is jointly exploited for both functionalities. The paper provides convincing results showing that the shared use of the spatial resources achieves better performance than that of the spatial division scheme.

F. Liu, L. Zhou, C. Masouros, A. Li, W. Luo, and A. Petropulu, Toward Dual-functional Radar-Communication Systems: Optimal Waveform Design,” IEEE Transactions on Signal Processing, vol. 66, no. 16, pp. 4264-4279, August 2018.
This paper studies optimal DFRC waveform design for a MIMO base station (BS) that serves multiple downlink users while detecting targets at the same time. It is the first DFRC paper to deal with generic channel models, including LoS and NLoS channels for communication users.  In contrast, the prior art can only accommodate LoS channel communications. The paper addresses a wide range of DFRC waveform design problems by adopting sophisticated algorithms, most of which are at low complexities and are easily implemented on practical platforms.

S. H. Dokhanchi, B. S. Mysore, K. V. Mishra, and B. Ottersten, A mmWave Automotive Joint Radar-Communications System,” IEEE Transactions on Aerospace and Electronic Systems, vol. 55, no. 3, pp. 1241-1260, June 2019.
This paper presents a novel joint radar-communication system that adopts phase-modulated continuous wave (PMCW) and OFDM waveforms for bi-static vehicle-to-vehicle sensing and communication. Performance tradeoffs between radar and communication uses are illustrated in terms of estimation RMSE, communication SER, and throughput, providing insights into the customization of the system for specific user demands in which radar and communication have different priorities.

J. A. Zhang, X. Huang, Y. J. Guo, J. Yuan, and R. W. Heath, Multibeam for Joint Communication and Radar Sensing Using Steerable Analog Antenna Arrays,” IEEE Transactions on Vehicular Technology, vol. 68, no. 1, pp. 671-685, January 2019.
This paper proposes a novel multibeam framework for implementing radar and communication functionalities using analog antenna arrays, where a fixed sub-beam is formulated to serve the communication users. In the meantime, a packet-varying scanning sub-beam is formulated for sensing. The system architecture and transmission protocol are provided for the proposed framework, together with efficient beamforming and sensing algorithms.

X. Liu, T. Huang, N. Shlezinger, Y. Liu, J. Zhou, and Y. C. Eldar, Joint Transmit Beamforming for Multiuser MIMO Communications and MIMO Radar,” IEEE Transactions on Signal Processing, vol. 68, pp. 3929-3944, 2020.
This paper proposes the first DFRC scheme that exploits an extra beamformer dedicated to radar sensing, in addition to the joint beamformer. Benefiting from that, the degrees-of-freedom (DoFs) available for MIMO radar can be extended to its maximum, i.e., the number of transmit antennas. As a consequence, the beamforming and detection performance for the radar functionality can be significantly improved compared to the benchmark technique in [Liu et al. 2018].

Topic: Transceiver Architecture

L. Han and K Wu, “Multifunctional Transceiver for Future Intelligent Transportation Systems,IEEE Transactions on Microwave Theory and Techniques, vol. 59, no. 7, pp. 1879-1892, July 2011.
This paper proposes a joint radar sensing and radio communication transceiver for future intelligent transportation systems, where the sensing mode and the communication mode are arranged in different time slots. The radar cycle is located in a constant-frequency period. Experimental prototyping has been carried out and shows very good performance.

C. Baquero Barneto, S. D. Liyanaarachchi, M. Heino, T. Riihonen, and M. Valkama, Full Duplex Radio/Radar Technology: The Enabler for Advanced Joint Communication and Sensing,” IEEE Wireless Communications, vol. 28, no. 1, pp. 82-88, February 2021.
This paper identifies full-duplex operation as the key enabler for integrated sensing and communication systems, where a device is used simultaneously as a communication transmitter and a radar transceiver. Advanced beamforming is considered for efficiently managing the subsystems’ beams in addition to self-interference suppression.

F. Bozorgi, P. Sen, A. N. Barreto, and G. Fettweis, RF Front-End Challenges for Joint Communication and Radar Sensing, in Proc., IEEE International Online Symposium on Joint Communications & Sensing (JC&S), Dresden, Germany, February 2021, pp. 1-6.
This is the first paper that systematically studies the design requirements and challenges of the RF front-end for joint communication and radar sensing. Different building blocks within a joint transceiver are discussed, namely amplifiers and frequency synthesizers, which meet the requirements of both communications and radar sensing.

Topic: Spectrum Sharing - Coexisting Communication and Sensing Systems

H. Griffiths et al., Radar Spectrum Engineering and Management: Technical and Regulatory Issues,” Proceedings of the IEEE, vol. 103, no. 1, pp. 85-102, January 2015.
This paper explains the nature of the spectrum congestion problem from a radar perspective, including its challenges and opportunities. A number of possible approaches are described, including improvements to the spectral purity of transmitters; intelligent, cognitive approaches to dynamic frequency allocation; passive sensing based on the emissions of other RF applications; and mimicing the behavior of echo-locating animals.

M. Bica, K. Huang, V. Koivunen, and U. Mitra,Mutual Information Based Radar Waveform Design for Joint Radar and Cellular Communication Systems,” in Proc., IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Shanghai, China, May 2016, pp. 3671-3675.
This paper proposes three kinds of waveform designs for joint radar communication systems, focusing on maximizing the mutual information between received echoes and transmitted waveforms. Particularly, in this scenario, the cellular network serves as a passive sensing network that exploits the collected communication signals scattered off the detecting target. The paper emphasizes the importance of collaboration between radar and communication transceivers.

L. Zheng, M. Lops, X. Wang, and E. Grossi, Joint Design of Overlaid Communication Systems and Pulsed Radars,” IEEE Transactions on Signal Processing, vol. 66, no. 1, pp. 139-154, January 2018.
This paper firstly introduces a new metric called the compound rate, and then provide several closed-form solutions for the optimum transmit policies to address the spectrum sharing problem for both radar and communication systems. In this paper, the communication system is still considered to be a victim of the radar system. A region of the achievable communication rates is also discussed with or without radar interference.

Y. Cui, V. Koivunen, and X. Jing, Interference Alignment Based Spectrum Sharing for MIMO Radar and Communication Systems,” in Proc., IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Kalamata, Greece, May 2018, pp. 1-5.
This paper proposes a joint precoder-decoder design based on interference alignment to cancel the mutual interference between radar and communication systems, and thereby, address the spectrum sharing problem between radar and communication systems. The generalized likelihood rate test (GLRT) is employed to analyze the performance of proposed method.

B. Li, A. P. Petropulu, and W. Trappe, Optimum Co-Design for Spectrum Sharing between Matrix Completion Based MIMO Radars and a MIMO Communication System,” IEEE Transactions on Signal Processing, vol. 64, no. 17, pp. 4562-4575, September 2016.
This paper considers spectrum sharing between point-to-point MIMO communication system and a multiple-input multiple-output matrix completion (MIMO-MC) radar. Two spectrum sharing designs are proposed: 1) a design wherein the communication system transmit covariance matrix is designed to minimize the effective interference power (EIP) at the radar receiver, 2) a joint design of the communication transmit covariance matrix and the MIMO-MC radar sampling scheme which achieves better EIP reduction. The paper is a very early paper that introduces optimization technologies into the spectrum sharing problem between radar and communications.

Topic: Networking: Cellular Network

Z. Ni, J. A. Zhang, X. Huang, K. Yang, and J. Yuan, “Uplink Sensing in Perceptive Mobile Networks With Asynchronous Transceivers,” IEEE Transactions on Signal Processing, vol. 69, pp. 1287-1300, February 2021.
This paper proposes an uplink sensing scheme for perceptive mobile networks with asynchronous transceivers, making sensing possible even in small base stations. A cross-antenna cross-correlation and mirrored-MUSIC algorithm is introduced to obtain unambiguous estimates for the true values of Doppler frequencies and delays. A high-resolution algorithm is proposed to exploit all samples for angle-of-arrival estimation, even in the presence of only a small number of antennas.

M. L. Rahman, J. A. Zhang, X. Huang, Y. J. Guo, and R. W. Heath, “Framework for a Perceptive Mobile Network Using Joint Communication and Radar Sensing,” IEEE Transactions on Aerospace and Electronic Systems, vol. 56, no. 3, pp. 1926-1941, June 2020.
This paper develops a framework for the perceptive mobile networks that integrates radar sensing function into the mobile communication networks. A unified system platform is presented to enable downlink and uplink sensing, sharing the same transmitted signals with communications. Estimation techniques based on compressive sensing are introduced to extract sensing parameters from OFDM and SDMA signals, together with a recursive clutter suppression method.

J. A. Zhang, M. L. Rahman, X. Huang, Y. J. Guo, S. Chen, and R. W. Heath, “Perceptive Mobile Networks: Cellular Networks With Radio Vision via Joint Communication and Radar Sensing,” IEEE Vehicular Technology Magazine, vol. 16, no. 2, pp. 20-30, June 2021.
This paper provides an overview on how to realize ISAC in mobile networks, leading to perceptive mobile networks. System architecture and required modifications to existing networks are discussed. Detailed research problems and potential solutions are reviewed, covering performance bounds, joint waveform optimization, clutter suppression, sensing parameter estimation and pattern recognition, and networked sensing under the cellular topology.

Topic: Networking: Sensor Network

M. Gastpar, M. Vetterli, and P. L. Dragotti, “Sensing Reality and Communicating Bits: A Dangerous Liaison,” IEEE Signal Processing Magazine, vol. 23, no. 4, pp. 70-83, July 2006.
This magazine article answers a fundamental question in sensor networks: When is it sufficient to build sensor network systems that work with discrete-time and -space representations? The sufficiency of discrete space, time, and amplitude domains is investigated and illustrated.

Y. Shen and M. Z. Win, “Fundamental Limits of Wideband Localization—Part I: A General Framework,” IEEE Transactions on Information Theory, vol. 56, no. 10, pp. 4956-4980, October 2010.
This paper develops a general framework for analyzing the fundamental limits of localization and then extends the analysis to cooperative location-aware networks based on wideband communication signals. In the developed framework, the localization accuracy is characterized by the squared position error bound and the equivalent Fisher information, allowing the succinctly derivation of localization performance limits and their scaling behaviors.

Topic: Secure ISAC

N. Su, F. Liu, and C. Masouros, “Secure Radar-Communication Systems with Malicious Targets: Integrating Radar, Communications and Jamming Functionalities,” IEEE Transactions on Wireless Communications, vol. 20, no. 1, pp. 83-95, January 2021.
This article studies the physical layer security in a multiple-input-multiple-output (MIMO) dual-functional radar-communication (DFRC) system. Here, the radar targets are considered as potential eavesdroppers that might eavesdrop the information from the communication transmitter to legitimate users. It employs an artificial noise approach to ensure the transmission secrecy, while maintaining good radar tracking performance.

X. Jiao, M. Mehari, W. Liu, M. Aslam, and I. Moerman, Openwifi CSI Fuzzer for Authorized Sensing and Covert Channels, in Proc., ACM Conference on Security and Privacy in Wireless and Mobile Networks (WiSec), NY, USA, pp. 377–379, June 2021.
CSI (Channel State Information) of WiFi systems contains the environment channel response between the transmitter and the receiver, so the people/objects and their movement in between can be sensed. In this paper, the authors open sourced a CSI fuzzer to enhance the privacy and security of WiFi CSI applications. The CSI fuzzer imposes an artificial channel response to the signal before it is transmitted, so the CSI seen by the receiver will indicate the actual channel response combined with the artificial response. Only the authorized receiver, which knows the artificial response, can calculate the actual channel response and perform the CSI sensing.

Topic: Applications: Vehicular Applications

J. Choi, V, Va, N. Gonzalez-Prelcic, R. Daniels, C. R. Bhat, and R. W. Heath, Millimeter-Wave Vehicular Communication to Support Massive Automotive Sensing,” IEEE Communications Magazine, vol. 54, no. 12, pp. 160-167, December 2016.
This magazine paper provides an overview of the motivations and challenges of adopting mmWave for vehicle-to-vehicle and vehicle-to-infrastructure applications. A high-level for the key challenge, i.e., mmWave beam training is proposed by leveraging the sensing capability. This article is a good start for research on sensing-assisted communications.

F. Liu, W. Yuan, C. Masouros, and J. Yuan, Radar-Assisted Predictive Beamforming for Vehicular Links: Communication Served by Sensing,” IEEE Transactions on Wireless Communications, vol. 19, no. 11, pp. 7704-7719, November 2020.
This paper proposes a sensing-assisted beam tracking scheme in vehicle-to-infrastructure applications. The sensing parameters of the vehicles are first extracted from the radar echoes and then predicted via the vehicle state transition model using extended Kalman filtering. A multi-user power allocation scheme is developed which aims at minimizing the estimation error.

F. Liu and C. Masouros, A Tutorial on Joint Radar and Communication Transmission for Vehicular Networks, IEEE Communications Letters, vol. 25, no. 2, pp. 322-336, February 2021.
This tutorial reviews the fundamental principles of ISAC from a technical perspective and overviews the state-of-art in ISAC, with a particular emphasis on vehicular networks. The general design criteria and representative methods for signaling transmission are presented. This tutorial is a good start for readers interested in ISAC-enabled vehicular networks.

N. González-Prelcic, R. Méndez-Rial, and R. W. Heath, Radar Aided Beam Alignment in MmWave V2I Communications Supporting Antenna Diversity, in Proc., Information Theory and Applications Workshop (ITA), La Jolla, USA, pp. 1-7, January 2016.
This is a pioneering paper considering the assistance of radar for beam alignment in vehicular communications. The information from the radar is used to extract the channel information and then to adapt the beams of the vehicular communication system.

W. Yuan, F. Liu, C. Masouros, J. Yuan, D. W. K. Ng, and N. González-Prelcic, Bayesian Predictive Beamforming for Vehicular Networks: A Low-Overhead Joint Radar-Communication Approach,” IEEE Transactions on Wireless Communications, vol. 20, no. 3, pp. 1442-1456, March 2021.
This paper develops a predictive beamforming scheme for vehicular networks where the road-side unit estimates and predicts the motion parameters of vehicles based on the echoes of the ISAC signal. A message passing algorithm based on a factor graph is proposed and near optimal performance is achieved by the maximum a posteriori estimation. The beamformers are then designed based on the predicted angles for establishing the communication links.

Topic: Applications: Events and Activities Recognition

Q. Huang, Z. Luo, J. Zhang, W. Wang, and Q. Zhang, LoRadar: Enabling Concurrent Radar Sensing and LoRa Communication, IEEE Transactions on Mobile Computing, 2020. Early Access.
This paper proposes the LoRa signal-based ISAC paradigm, which enables an frequency-modulated continuous wave (FMCW) radar to communicate with a LoRa transceiver. For downlink transmission, ISAC signals are designed to preserve sensing capability. For uplink transmission, a new receiving chain design is presented. This paper also discusses several remaining issues for future research.

Y. Kim and H. Ling, Human Activity Classification Based on Micro-Doppler Signatures Using A Support Vector Machine,” IEEE Transactions on Geoscience and Remote Sensing, vol. 47, no. 5, pp. 1328-1337, May 2009.
This paper investigates the feasibility of classifying different human activities based on micro-Doppler signatures. By extracting six features from the Doppler spectrogram, a support vector machine is trained using the measurements. The classification accuracy is above 90%.

G. Wang, Y. Zou, Z. Zhou, K. Wu, and L. M. Ni, We Can Hear You with Wi-Fi!,IEEE Transactions on Mobile Computing, vol. 15, no. 11, pp. 2907-2920, 1 November 2016.
This paper presents WiHear, which uses received Wi-Fi signals to “hear” people talk. It works by detecting and analyzing fine-grained radio reflections from mouth movements. WiHear solves this micro-movement detection problem by introducing Mouth Motion Profile that leverages partial multipath effects and wavelet packet transformation. Experimental results demonstrate that WiHear can “hear” multiple people talking within the radio range, without requiring line-of-sight propagation.

F. Colone, D. Pastina, P. Falcone, and P. Lombardo, WiFi-Based Passive ISAR for High-Resolution Cross-Range Profiling of Moving Targets,IEEE Transactions on Geoscience and Remote Sensing, vol. 52, no. 6, pp. 3486-3501, June 2014.
This paper presents an effective signal processing scheme to track slow-speed moving vehicles and to obtain their cross-range profiles with a passive bistatic radar (PBR) based on the signals of opportunity emitted by a WiFi router. The paper shows how an inverse synthetic aperture radar (ISAR) scheme can be developed using the WiFi-based PBR for high-resolution cross-range profiling.

M. G. Amin, Y. D. Zhang, F. Ahmad, and K. C. D. Ho, Radar Signal Processing for Elderly Fall Detection: The Future for In-Home Monitoring, IEEE Signal Processing Magazine, vol. 33, no. 2, pp. 71-80, March 2016.
This paper overviews signal processing algorithms and techniques involved in wireless signal based elderly fall detection. This is a very early article that systematically describe related signal model, signal analysis, feature extraction and classification technologies. Several open issues and problems, including sensor placement, features characterization and activities recognition are introduced.

A. Overeem, H. Leijnse, and R. Uijlenhoet, “Rainfall Maps from Cellular Communication Networks”, Proceedings of the National Academy of Sciences, vol. 110, no. 8, pp. 2741-2745, February 2013.
This paper provides a good example of using the received signal power of cellular backhaul links for monitoring rainfall. The space–time dynamics of rainfall for an entire country (The Netherlands) was retrieved based on an unprecedented number of links (∼2,400) and a rainfall retrieval algorithm.

Topic: Demonstrations

P. M. McCormick, S. D. Blunt, and J. G. Metcalf, Simultaneous Radar and Communications Emissions From a Common Aperture, Part I: Theory,” and “Part II: Experimentation,” in Proc., IEEE Radar Conference (RadarConf), May 2017, Seattle, WA, USA, pp. 1685-1690, 1697-1702.
These two companion papers present the theory and implementation of a radio system that integrates radar and communication functionality via a designed waveform set. Herein, the communication and radar waveforms can be transmitted in a common antenna array and with the same spectral support. The multi-function waveforms were implemented on an Air Force Research Laboratory (AFRL) software-defined radar testbed comprised of four independent transmit channels.

J. Wang, X.-D. Liang, L.-Y. Chen, L.-N. Wang, and K. Li, First Demonstration of Joint Wireless Communication and High-Resolution SAR Imaging Using Airborne MIMO Radar System,” IEEE Transactions on Geoscience and Remote Sensing, vol. 57, no. 9, pp. 6619-6632, September 2019.
This paper introduces the implementation of an integrated sensing and communication system, where wireless communication and synthetic aperture radar (SAR) imaging are performed by an airborne multi-input multi-output (MIMO) radar with modified orthogonal frequency-divison multiplexing (OFDM) strategy. The proposed system is validated by laboratory and flight experiments.

P. Kumari, A. Mezghani, and R. W. Heath, JCR70: A Low-Complexity Millimeter-Wave Proof-of-Concept Platform for a Fully-Digital SIMO Joint Communication-Radar,” IEEE Open Journal of Vehicular Technology, vol. 2, pp. 218-234, March 2021.
In this paper, sensing and communication systems are integrated in a joint radar-communication proof-of-concept platform, which consists of few-bit analog-to-digital converters (ADCs), with a single-input-multiple-output (SIMO) architecture at the millimeter-wave (mmWave) band. This system is an evolution of earlier work and demonstrates the platform’s performance in the 71-76 GHz band with an additional full-duplex radar receiver and a moving antenna on a sliding rail.

Q. Zhang, H. Sun, Z. Wei, and Z. Feng, Sensing and Communication Integrated System for Autonomous Driving Vehicles, in Proc., IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), July 2020, Toronto, ON, Canada, pp. 1278-1279.
In this paper, an integrated sensing and communication system is implemented in 28 GHz mmWave band. Smart weighted grid searching based fast beam alignment and beam tracking algorithms are implemented to achieve a high data rate.

On the Web

IEEE Communications Society Emerging Technology Initiative (ETI), Integrated Sensing and Communication.

IEEE Signal Processing Society Technical Working Group (TWG), Integrated Sensing and Communication.

IEEE Wireless Communications Technical Committee, Special Interest Group on Integrated Sensing and Communication (ISAC).

1st IEEE ComSoc-SPS ISAC Webinar Series, May 2021 - August 2021.