Joint Radar-communication System Research Articles

Optimized Resource Allocation for Distributed Joint Radar-Communication System

Optimized Resource Allocation for Distributed Joint Radar-Communication System

Optimum Waveform Selection for Target State Estimation in the Joint Radar-Communication System

Optimum Waveform Selection for Target State Estimation in the Joint Radar-Communication System

AoI-Aware Waveform Design for Cooperative Joint Radar-Communications Systems with Online Prediction of Radar Target Property

AoI-Aware Waveform Design for Cooperative Joint Radar-Communications Systems with Online Prediction of Radar Target Property

Closed-Form Model for Performance Analysis of THz Joint Radar-Communication Systems

As an enabler technology in future network, terahertz (THz) joint radar-communication (T-JRC) has been envisioned as a solution to overcome the challenges in THz communications. Recent works on JRC mainly emphasize either performance tradeoffs or mutual benefits between radar and communication functionalities. Unable to characterize both benefit and tradeoff relationships, existing metrics and models are inapplicable to performance analysis on T-JRC systems. In this paper, a closed-form T-JRC performance model are proposed to explore the relationship between radar and communication metrics. To begin with, a novel T-JRC system model concerning random mobility and THz beam tracking is put forward. Next, the performance bounds of T-JRC performance in terms of communication rate and a proposed radar rate are acquired in three different integration cases. Furthermore, the expression of communication rate by radar rate in T-JRC is obtained theoretically, which is the first time to derive the closed-form relationship considering both benefits and tradeoffs to the best of our knowledge. Finally, numerical results validate the proposed model as well as closed-form expression, showing that the model succeeds in benefit and tradeoff relationship characterization in T-JRC systems and the fitting bounds are applicable in non-extreme scenarios.

Secure Transmission Scheme Based on Joint Radar and Communication in Mobile Vehicular Networks

Vehicle-to-vehicle (V2V) communication applications face significant challenges to security and privacy since all types of possible breaches are common in connected and autonomous vehicles (CAVs) networks. As an inheritance from conventional wireless services, potential eavesdropping is one of the main threats to V2V communications. In our work, the anti-eavesdropping scheme in CAVs networks is developed through the use of cognitive risk control (CRC)-based vehicular joint radar-communication (JRC) system. In particular, the supplement of off-board measurements acquired using V2V links to the perceptual information has presented the potential to enhance the traffic target positioning precision. Then, transmission power control is performed utilizing reinforcement learning, the result of which is determined by a task switcher. Based on the threat evaluation, a multiple armed bandit problem is designed to implement the secret key switching procedure when it is needed. Through constant perception-execution loops (PELs), the security and confidentiality is improved for the authorized vehicles in their behavioral interactions with the illegal eavesdropper. Numerical experiments have presented that the developed approach has anticipated performance in terms of some risk assessment indicators.

Receiver Design in Full-Duplex Joint Radar-Communication Systems

Full-duplex (FD) integrated sensing and communication (ISAC) has great potential in future vehicular networks. However, the FD requirement and the ISAC functions make the receiver processing extremely complicated, particularly when multiple transmissions are uncoordinated. In this paper, we study frequency-hopping (FH) based receivers in an FD ISAC system, where the arrivals of backscattered signals from one node may overlap with those of signals from another node. To mitigate the interferences caused by the overlapping signals, we consider two receiver options based on either conventional communications or frequency-modulated continuous-wave radars, and two signal modulations based on either fast FH or un-slotted ALOHA FH. Based on the different signal modulations, we develop two parameter estimation schemes via using FH-decoding and dechirp operations, respectively. To further improve the sensing accuracy, we proceed to propose an iterative algorithm, which refines the estimates of all parameters via using short-time-Fourier transform and maximizing the received power in desired frequency bands. After obtaining all channel parameters in sensing, bilateral communications between two nodes are realized by differential phase-shift keying. Finally, simulation results are provided and verify that the proposed FD ISAC can obtain parameters in high resolution and realize robust communication links.

Waveform Optimizations Using Virtual Arrays in Broadband Radar Communications

This letter proposes a virtual-array-based waveform optimization scheme for broadband joint radar-communication systems. We first formulate a problem of minimizing Cramér-Rao bound (CRB) of radar subject to communication constraints. To reduce the high complexity of directly solving the problem, we allocate the virtual arrays to users according to their communication thresholds and minimize the largest eigenvalue of the CRB matrix. Then, the optimization problem can be solved by semi-definite programming but the solutions are not always available. We finally propose a low-complexity solution that minimizes the CRB first and then transforms the optimization results to meet the constraints on communications. Simulation results are provided and verify the effectiveness of the proposed scheme.

Radar Sensor and Data Communication System Based on OFDM Without Cyclic Prefix

The high data rate and large bandwidth of orthogonal frequency division multiplexing(OFDM) modulations have made the integrated waveform design using OFDM-based signals a popular research topic in recent years. However, OFDM signals are sensitive to the Doppler frequency bias and multipath effects, which are traditionally accommodated by cyclic prefixes (CP) inserted before each OFDM symbol. Since the CP is the partial copy of the OFDM symbol, it not only loses energy in communication systems but also forms false targets after radar signal processing. To address the shortcomings of conventional OFDM, this paper proposes a modified CP-free OFDM joint radar communication system(JRCS). It transmits the OFDM pulse signal to certain targets and/or communication systems and receives echoes in the pulse repetition interval. By removing CP, the radar system can compress the echoes without ghost targets. Through reasonable sampling which should be designed significantly, the communication systems demodulate the OFDM pulse to extract information without intersymbol interference in multipath channels. Furthermore, the constraints of the time, frequency, and sampling on the system are analyzed in detail and an illustrating system under an air-to-ground scenario is constructed. Simulation results show that the proposed signal design and processing method has a better performance compared to conventional OFDM signals.

Chaotic waveform for optimal joint radar communication systems

Due to the increased spectrum congestion, there has been a tremendous interest in radar and communication devices operating on a shared platform. Therefore, the waveform design for joint radar communication (JRC) systems has recently gained significant attention. Despite several efforts, most state-of-the-art waveforms are far from achieving ideal radar and communication performance. To address this issue, we design a family of chaotic maps whose output yields waveforms with optimal JRC features. We adopt the antipodal chaos shift keying (ACSK) scheme, where the segments of the chaotic signal are multiplied by ±1 to encode the binary information. This ACSK waveform is further used for the JRC system transmission. Once the synchronization between the receiver and transmitter is established, the information is recovered by cross-correlating the received and the synchronized waveforms. This technique yields bit error rates (BER) similar to the theoretical values of the BPSK waveform. The same transmitted waveform results in a thumb-tack ambiguity function which is essential for high-resolution radar imaging. The variance analysis of the ambiguity function shows that the proposed waveform is comparable to the noise-modulated waveforms. We also show that the multiplexed ACSK waveforms yield similar optimal behavior. Furthermore, we demonstrate the potential of the family of chaotic maps for multiple-input, multiple-output (MIMO) JRC systems.

Joint Radar Communication With Novel GCC Preamble and Point-Wise Minimum Fusion

In this paper, a new preamble waveform design and a corresponding minimum-point processing algorithm at receiver are proposed to perform radar sensing of communication signal echoes. In our design, we consider the millimeter wave (mmWave) 802.11ad/802.11ay communication frame format as a reference. Our proposed new preamble replaces the second pair of single-carrier (SC) Golay complementary code (GCC) used in the preamble of IEEE 802.11ad/802.11ay by orthogonal frequency-division multiplexing (OFDM) GCC waveform, resulting in a SC-OFDM GCC preamble waveform. At the receiver, a point-wise minimum operation is performed on the separate radar ambiguity functions (AF) of the SC-GCC and OFDM-GCC to improve the overall quality of the preamble AF. Furthermore, point-wise minimum processing is applied to fuse the communication data AF and the preamble AF, so as to further enhance the radar sensing quality of the entire communication frame. In addition, theoretical analysis of the performance gain of such radar AF fusion is provided. Both theoretical analysis and simulation results demonstrate that the newly proposed SC-OFDM GCC preamble design and the minimum-point fusion of data AF and preamble AF provide a significant performance improvement for automotive radar sensing. Specifically, the proposed SC-OFDM GCC preamble with minimum-point processing algorithm improves the peak-to-max-sidelobe ratio (PMSR) of radar AF over the conventional 802.11ad/802.11ay preamble. Moreover, the proposed preamble-data AF fusion technique further enhances the PMSR as well as the Doppler resolution over the existing joint radar communication systems (which process either the preamble echo or the data echo only). Finally, the proposed minimum-point processing and data AF fusion are extended from single-frame to multi-frame processing to further improve the Doppler resolution.

A Spatial–Temporal Joint Radar-Communication Waveform Design Method with Low Sidelobe Level of Beampattern

A joint radar-communication (JRC) system utilizes the integrated transmit waveform and a single platform to perform radar and communication functions simultaneously. Admittedly, the multibeam waveform design approach could transmit the assigned waveforms in different beams with the aid of spatial and temporal degrees of freedom. However, a high sidelobe level (SLL) in the beampattern reduces energy efficiency and expands exposure probability. In this study, we propose a novel spatial–temporal joint waveform design method based on the beamforming algorithm to form a low SLL beampattern. Waveform synthesis constraints are considered to synthesize desired radar and communication waveforms at designated directions. Furthermore, we impose the constant modulus constraint to lessen the impact of the high peak-to-average ratio (PAPR). The optimization process of the whole model can be summarized as two stages. First, the covariance matrix is created by convex optimization with respect to the minimum SLL. Second, the integrated transmit waveform is tuned through an alternating projection algorithm. Based on the simulation findings, we demonstrate that the proposed method outperforms the traditional methods in terms of low SLL and waveform synthesis. Meanwhile, we validate the effectiveness of the proposed method using semi-physical experiment results.

Photonic super-resolution millimeter-wave joint radar-communication system using self-coherent detection.

A millimeter-wave (MMW) joint radar-communication (JRC) system with super-resolution is proposed and experimentally demonstrated, using optical heterodyne upconversion and self-coherent detection downconversion techniques. The point lies in the designed coherent dual-band constant envelope linear frequency modulation-orthogonal frequency division multiplexing (LFM-OFDM) signal with opposite phase modulation indexes for the JRC system. Then the self-coherent detection, as a simple and low-cost means, is accordingly facilitated for both de-chirping of MMW radar and frequency downconversion reception of MMW communication, which circumvents costly high-speed mixers along with MMW local oscillators and, more significantly, achieves the real-time decomposition of radar and communication information. Furthermore, a super-resolution radar range profile is realized through the coherent fusion processing of dual-band JRC signals. In experiments, a dual-band LFM-OFDM JRC signal centered at 54 GHz and 61 GHz is generated. The two bands feature an identical instantaneous bandwidth of 2 GHz and carry an OFDM signal of 1 Gbaud, which helps to achieve a 6-Gbit/s data rate for communication and a 1.76-cm range resolution for radar.

A Cooperative SAR-Communication System Using Continuous Phase Modulation Codes and Mismatched Filters

The electromagnetic congestion due to the continuous growth of spectral demand has been skyrocketing for the past years. Joint radar-communication systems are, thus, attracting attention as they can alleviate spectrum occupancy by using the same bandwidth to perform both applications. In this context, a cooperative radar-communication system, which is a specific category that uses communication codes to both transmit information and perform radar missions, can be considered. Continuous phase-modulated (CPM) codes are considered in this article in order to generate high-resolution radar images from airborne radar. Since mitigating the sidelobe level energy is essential for good image quality, we resort here to optimized mismatched filters (MMFs). A fast algorithm is proposed to minimize the computational time of these filters. Simulated data are generated, as well as resynthesized synthetic aperture radar (SAR) images, and reconstructed from real chirp-based data using CPM codes and MMFs. Their performance is evaluated using different comparison tools and shows that the use of mismatched filtering and different messages embedded in the phase of each transmitted code provides enhanced image quality.

Monostatic Sensing With OFDM Under Phase Noise: From Mitigation to Exploitation

We consider the problem of monostatic radar sensing with orthogonal frequency-division multiplexing (OFDM) joint radar-communications (JRC) systems in the presence of phase noise (PN) caused by oscillator imperfections. We begin by providing a rigorous statistical characterization of PN in the radar receiver over multiple OFDM symbols for free-running oscillators (FROs) and phase-locked loops (PLLs). Based on the delay-dependent PN covariance matrix, we derive the hybrid maximum-likelihood (ML)/maximum a-posteriori (MAP) estimator of the deterministic delay-Doppler parameters and the random PN, resulting in a challenging high-dimensional nonlinear optimization problem. To circumvent the nonlinearity of PN, we then develop an iterated small angle approximation (ISAA) algorithm that progressively refines delay-Doppler-PN estimates via closed-form updates of PN as a function of delay-Doppler at each iteration. Moreover, unlike existing approaches where PN is considered to be purely an impairment that has to be mitigated, we propose to exploit PN for resolving range ambiguity by capitalizing on its delay-dependent statistics (i.e., the range correlation effect), through the formulation of a parametric Toeplitz-block Toeplitz covariance matrix reconstruction problem. Simulation results indicate quick convergence of ISAA to the hybrid Cramér-Rao bound (CRB), as well as its remarkable performance gains over state-of-the-art benchmarks, for both FROs and PLLs under various operating conditions, while showing that the detrimental effect of PN can be turned into an advantage for sensing.

Dual-Blind Deconvolution for Overlaid Radar-Communications Systems

The increasingly crowded spectrum has spurred the design of joint radar-communications systems that share hardware resources and efficiently use the radio frequency spectrum. We study a general spectral coexistence scenario, wherein the channels and transmit signals of both radar and communications systems are unknown at the receiver. In this dual-blind deconvolution (DBD) problem, a common receiver admits a multi-carrier wireless communications signal that is overlaid with the radar signal reflected off multiple targets. The communications and radar channels are represented by continuous-valued range-time and Doppler velocities of multiple transmission paths and multiple targets. We exploit the sparsity of both channels to solve the highly ill-posed DBD problem by casting it into a sum of multivariate atomic norms (SoMAN) minimization. We devise a semidefinite program to estimate the unknown target and communications parameters using the theories of positivehyperoctant trigonometric polynomials (PhTP). Our theoretical analyses show that the minimum number of samples required for near-perfect recovery is dependent on the logarithm of the maximum of number of radar targets and communications paths rather than their sum. We show that our SoMAN method and PhTP formulations are also applicable to more general scenarios such as unsynchronized transmission, the presence of noise, and multiple emitters. Numerical experiments demonstrate great performance enhancements during parameter recovery under different scenarios.

Photonic-aid dual-formats LFM signals generator for joint radar-communication system

(Objective) A photonic-aid approach to generate dual-formats linearly frequency modulation (LFM) signals for a joint radar-communication (JRC) system is proposed and verified by simulation. (Methods)In this scheme, a polarization division integrated modulator is employed to perform double sideband modulation to a driving RF signal with both sub-MZMs biased at the maximum transmission point. A driving LFM signal is applied to a followed Mach-Zehnder modulator (MZM) to achieve frequency multiplication. Then, the generated optical signal is fed to a polarization modulator (PolM) to perform data modulation. By changing the passband of the optical filter (OF) and polarization rotation of the polarization controller (PC), frequency quadrupled chirp polarity modulated or binary phase shift keying (BPSK) LFM signals of each format can be obtained. (Results) A simulation is carried out, and dual-formats LFM waveforms with chirp ranges of 16–24 GHz, 20–26 GHz, and 32–36 GHz are generated. Applications on both radar and communication are demonstrated, and the range resolution of the generated signal is improved by 3 times. By using chirp polarity modulation, triangular wave frequency modulation (FM) signal is produced to achieve moving target detection. The efficiency of anti-jamming communication is also verified. For BPSK-LFM waveforms, optical de-chirping operation and coherent demodulation are successfully performed. The trade-off between radar and communication performance is also studied. A BPSK-LFM signal with its communication rate improved by over 28 times while SSR of optical de-chirping only descended by 6.52 dB is obtained via intra-pulse coding, a minor phase difference of BPSK modulation and DSSS technology.

Joint radar communication system design based on filter bank multicarrier modulation scheme

Since orthogonal frequency division multiplexing (OFDM) signals are sensitive to Doppler shift, OFDM signals with cyclic prefix (CP) not only reduce the communication rate but also result in symmetric pseudo peaks in the ambiguity function of the radar, which eventually lead to the degradation of the performance of the joint radar communication system (JRCS). In this study, a novel JRCS is proposed based on the filter bank multicarrier (FBMC) waveform for the inverse synthetic aperture radar (ISAR) imaging and communication system. On the one hand, FBMC waveforms are capable of low orthogonality between subcarriers, which can counter Doppler and multipath effects. On the other hand, FBMC waveforms do not require CP, so the false targets can be avoided and spectral efficiency can be improved. The influence of multipath effect and Doppler shift on FBMC waveform in an integrated system is analysed in detail, and a Doppler compensation algorithm suitable for FBMC-integrated waveform is proposed. The phase error caused by target motion can be iteratively compensated to obtain a well-focussed ISAR image. Finally, considering the ISAR image entropy after motion compensation as the evaluation metric, extensive simulation experiments verify the noise robustness and effectiveness of the proposed algorithm. Compared with the conventional OFDM and CP-OFDM schemes, the simulation verifies that the proposed waveform design and processing method has better performance in the ISAR imaging and communication integrated system.

Transmit beampattern design for joint radar-communications system with circulating code array

A new transmit beampattern design method is proposed for the joint radar-communications (JRC) systems with circulating code array. Each array element of the designed JRC system transmits the same basic waveform with different starting time, multiple beams towards the radar targets and the communication receivers are formed. For circulating code array, there is a certain relationship between the spectrum band of the transmitted signal and the coverage of the synthesized beampattern. By implementing spectrum planning according to the desired beampattern, flexible beampattern synthesis can be realized. Phase modulation term is attached to the phase of the transmitted signal in the corresponding communication spectrum band, and it is used to carry communication information. Unlike previous works, benefiting from the use of circulating coed array, multiple wide beams and narrow beams can be synthesized simultaneously in this paper without solving optimization problems. The effectiveness of the designed method is validated by numerical results.

Optimization of Network Throughput of Joint Radar Communication System Using Stochastic Geometry

Recently joint radar communication (JRC) systems have gained considerable interest for several applications such as vehicular communications, indoor localization and activity recognition, covert military communications, and satellite based remote sensing. In these frameworks, bistatic/passive radar deployments with directional beams explore the angular search space and identify mobile users/radar targets. Subsequently, directional communication links are established with these mobile users. Consequently, JRC parameters such as the time trade-off between the radar exploration and communication service tasks have direct implications on the network throughput. Using tools from stochastic geometry (SG), we derive several system design and planning insights for deploying such networks and demonstrate how efficient radar detection can augment the communication throughput in a JRC system. Specifically, we provide a generalized analytical framework to maximize the network throughput by optimizing JRC parameters such as the exploration/exploitation duty cycle, the radar bandwidth, the transmit power and the pulse repetition interval. The analysis is further extended to monostatic radar conditions, which is a special case in our framework. The theoretical results are experimentally validated through Monte Carlo simulations. Our analysis highlights that for a larger bistatic range, a lower operating bandwidth and a higher duty cycle must be employed to maximize the network throughput. Furthermore, we demonstrate how a reduced success in radar detection due to higher clutter density deteriorates the overall network throughput. Finally, we show a peak reliability of 70% of the JRC link metrics for a single bistatic transceiver configuration.

Joint Radar-Communication Systems: Modulation Schemes and System Design

The joint radar-communication (RadCom) concept has been continuously gaining interest due to the possibility of integrating radar sensing and communication functionalities in the same radio frequency hardware platform. Besides a number of challenges in terms of hardware design and signal processing, the choice of suitable modulation schemes plays a significant role in driving the performance of RadCom systems. In this sense, this article presents an overview of state-of-the-art modulation schemes for RadCom systems, namely, chirp sequence, phase-modulated continuous wave, orthogonal frequency-division multiplexing, and orthogonal chirp-division multiplexing. For each of them, a detailed system model is outlined, and parameters for quantifying both radar and communication performances are presented. Finally, a comparative analysis of the aforementioned RadCom modulation schemes is carried out to illustrate the presented discussion.