Directional modulation based on dual-function radar-communication system

We consider a dual-function radar communication (DFRC) system employing frequency hopping (FH) radar waveforms. Each communication symbol is represented by a phase-modulated pulse sequence that multiplies the radar hops in fast-time and transmitted from a multiple-input multiple-output radar platform. In this respect, the DFRC system considered follows the code-shift keying (CSK) signal embedding strategy. The phase modulations include phase-shift keying (PSK), derivative PSK, and continuous phase modulation. The CSK pulse sequences and the FH code are jointly designed to reduce range sidelobe levels (RSLs) and combat range sidelobes modulation. It is shown that the joint optimization using the genetic algorithm yields desired CSK sequences and FH code matrix with less computational complexity compared to the exhaustive search algorithm. The power spectral density and detection performance of various DFRC systems are analyzed, underscoring the tradeoff between RSLs and spectral sidelobe levels. The proposed DFRC system with optimum phase sequences and hopping code achieves high data communication rates by permitting frequencies to be reused in the radar hops.

Application of LFM-CPM signal into a DFRC system based on circulating code array

We present a dual-function radar communication (DFRC) system applying signal embedding through a code shift keying (CSK) strategy. The information symbol is phase encoded into a sequence and then modulated by the continuous phase modulation (CPM) before embedding into frequency hopping (FH) radar sub-pulses. The CPM modulated communication symbol phase coded sequence is multiplied with the FH radar waveforms in fast-time and transmitted through multiple-input multiple-output (MIMO) radar platforms. We address the problem of range sidelobe modulation (RSM) and propose the design of the optimum CSK sequences to reduce the degree of change in the range sidelobe levels (RSLs) of the ambiguity function (AF). It is shown that the optimum CSK sequences yield significant reduction in the RSLs of the DFRC system. They also maintain the same degree of correlation between FH sub-pulses regardless of the communication symbol sequences embedded. Additionally, the proposed DFRC system with the optimized waveform design provides good spectrum containment and achieves high communication data rates.

Dual-function radar communication (DFRC) systems can provide ubiquitous communication and sensing services on a unified platform. In environmental and drone monitoring applications, the DFRC system is often expected to monitor the target area while providing communication services. However, traditional DFRC systems are mainly based on multiple-input multiple-output (MIMO) arrays, which can only illuminate the whole specific angles, rather than a specific area. To address this, based on frequency diverse array MIMO (FDA-MIMO), this paper proposes an area monitoring and multi-user communication dual-function system. We formulate a weighted optimization problem that jointly considers the integrated mainlobe-to-sidelobe ratio (IMSR) and the communication sum rate. To solve this non-convex problem, a Riemannian manifold alternating optimization (RMAO) algorithm is developed. Specifically, the receive beamformer is derived in closed-form, and the transmit precoder is optimized via Riemannian conjugate gradient method. Numerical results illustrate that the proposed system can realize the angle–range selective area surveillance while providing communication service, which is not available in MIMO-based systems.

We consider a multiple-input multiple-output (MIMO) dual function radar communication (DFRC) system employing frequency hopping (FH) radar waveforms. The DFRC system embeds communication symbols using code-shift keying (CSK) strategy. Each symbol is represented by a phase modulated pulse code sequence which multiplies the radar hops in fast-time before transmitted from the MIMO radar platform. This strategy allows for reduced clutter modulation caused by changed radar waveforms within coherent processing interval (CPI). We analyze the effect of this communication symbol embedding scheme on range sildelobe levels (RSLs) and derive the DFRC probability of target detection. We show that the DFRC waveforms enhances target visibility leading to improved target detection compared with the FH radar without signal embedding.

A dual-function MIMO radar-communication system via waveform permutation

Optimization algorithms for transmit waveform design in radar-centric dual-function radar-communication systems

This paper addresses joint design of the transmitting waveform and the receivers of a dual-function radar-communication (DFRC) system that enables both multiple-input multiple-output (MIMO) radar sensing and multi-user multiple-input single-output (MU-MISO) communications. The proposed approach incorporates the design of the communication receiving (Rx) coefficients, in addition to the radar Rx filters. We seek to maximize the minimum radar signal-to-interference-plus-noise ratio (SINR) over multiple targets, subject to per-antenna power constraints, peak-to-average-power ratio (PAPR) constraints and a communication SINR constraint for each user. A successive convex approximation algorithm is developed to find a good solution for the resultant nonconvex design problem. Numerical results show that by incorporating the communication Rx coefficients into the joint design, the radar and communication capabilities of the DFRC system can be significantly enhanced over the state-of-the-art designs.

Joint radar and communication (JRC) technology is gradually becoming an essential approach to alleviating spectral congestion. Radar and communications systems were designed with common spectral and hardware resources to reduce size, improve performance, reduce cost, and decongest the spectrum. Various approaches have been proposed to achieve the coexistence of radar and communication systems. This paper mainly focuses on the research directions of radar communication coexistence (RCC) and dual-function radar communication systems (DFRC) in JRC technology. We summarize and analyze the existing research problems in the JRC era. According to the characteristics and advantages of JRC technology, we highlight several potentials in military and commercial applications.

Dual-function radar-communications (DFRC) systems have emerged as a promising solution for spectrum sharing problem in recent years. In this paper, we propose a novel DFRC strategy by exploiting directional power control and waveform diversity. The proposed technique ensures the highest possible magnitude of the radar main beam resulting in an improved signal-to-noise ratio for the radar operation. This maximization objective is achieved while considering the pre-allocated or adjustable transmit energy requirement for radar and communication operations. The secondary communication objective enabling multi-user access is realized by transmitting distinct amplitude levels and phases towards different communication receivers located in the sidelobe region of radar. As an example, power allocation for different orthogonal frequency-division multiplexing (OFDM) subcarriers projected towards the radar main beam and the communication receivers is discussed by considering the frequency response of target returns. Simulation results illustrate the performance of the proposed technique.

In this paper, we consider waveform design for dual-function radar-communication systems based on multiple-input-multiple-out arrays. To achieve better Rician target detection performance, we use the relative entropy associated with the formulated detection problem as the design metric. We also impose a multi-user interference energy constraint on the waveforms to ensure the achievable sum-rate of the communications. Two algorithms are presented to tackle the nonlinear non-convex waveform design problem. In the first algorithm, we derive a quadratic function to minorize the objective function. To tackle the quadratically constrained quadratic programming problem at each iteration, a semidefinite relaxation approach followed by a rank-one decomposition procedure and an efficient alternating direction method of multipliers (ADMM) are proposed, respectively. In the second algorithm, we present a novel ADMM algorithm to tackle the optimization problem and employ an efficient minorization-maximization approach in the inner loop of the ADMM algorithm. Numerical results demonstrate the superiority of both algorithms. Moreover, the presented algorithms can be extended to synthesize peak-to-average-power ratio constrained waveforms, which allows the radio frequency amplifier to operate at an increased efficiency.

In this paper, we develop a novel approach for a joint platform of radar and communication systems. The previous approaches for dual-function radar-communication systems focused only on the simultaneous transmission of radar and communications in radar active mode. To increase the throughput of communications without affecting the radar operation, we enable communication during the whole pulse repetition interval by using two generalized sidelobe cancellers. We propose two different operational modes of the dual-function radar-communications system. In active mode, the radar function is achieved through the mainlobe, and communications are achieved through the sidelobes. In active mode, only one generalized sidelobe canceller is functional. In rest mode, both the generalized sidelobe cancellers are functional. The first generalized sidelobe canceller has the mainlobe and sidelobe levels as in active mode, and the second generalized sidelobe canceller has the same mainlobe level but double the power in the sidelobes. The output is the difference between the two, in which the mainlobe is canceled, while the sidelobes have the same power, as in the case of active mode. The effectiveness of the proposed scheme is investigated in terms of the bit error rate. Moreover, the proposed system allows communication during the whole pulse repetition interval, thus, enhancing the throughput tremendously.

Recently proposed, the dual-function radar-communication (DFRC) system aims to tackle the problem of spectrum overcrowding by allowing the joint design of radar and wireless communications. This system employs the transmit beamforming technique and waveform diversity to embed information in radar transmissions. In this paper, a dual-function radar communication system based on directional modulation (DM) is proposed. A set of beam weight vectors are designed to satisfy the requirements of the DFRC system. Three improved beam weight design methods of DM, minimum beam weight difference method (MBWDM) , minimum waveform differential modulus sum method (MWDMSM) and minimum enemy beam gain method (MEBGM) , are proposed for DFRC systems to optimise the DFRC beam by increasing the phase distortion or reducing the beam gain in the non-communication direction, to enhance the security during DFRC communication. Compared to the unimproved DFRC system beam, all three DM methods design waveforms that effectively reduce the correct receive area near the receiver direction and reduce the likelihood of correctly demodulated information in that direction when eavesdropping direction is known. Waveforms generated using MWDMSM maintain high BER performance at all angles in the non-communication zone and therefore also have the ability to defend against enemies of unknown orientation.

Manifold optimization for hybrid beamforming in dual-function radar-communication system

Dual-function radar-communications (DFRC) systems implement radar and communication functionalities on a single platform. Jointly designing these subsystems can lead to substantial gains in performance as well as size, cost, and power consumption. In this paper, we propose a DFRC system, which utilizes generalized spatial modulation (GSM) to realize coexisting radar and communications waveforms. Our proposed GSM-based scheme, referred to as spatial modulation based communication-radar (SpaCoR) system, allocates antenna elements among the subsystems based on the transmitted message, thus achieving increased communication rates by embedding additional data bits in the antenna selection. We formulate the resulting signal models, and present a dedicated radar processing scheme. To evaluate the radar performance, we characterize the statistical properties of the transmit beam pattern. Then, we present a hardware prototype of the proposed DFRC system, demonstrating the feasibility of the scheme. Our results show that the proposed GSM system achieves improved communication performance compared to techniques utilizing fixed allocations operating at the same data rate. For the radar subsystem, our experiments show that the spatial agility induced by the GSM transmission improves the angular resolution and reduces the sidelobe level in the transmit beam pattern compared to using fixed antenna allocations.