Controlling Clutter Modulation in Frequency Hopping MIMO Dual-Function Radar Communication Systems

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.

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.

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

Dual-function radar-communication (DFRC) system has recently been proposed to enable the co-design of radar and wireless communications, which in turn alleviates the increased spectrum congestion crisis. DFRC system exploits the transmit beamforming technique and waveform diversity, the combination of which enables the system to embed information in radar emission. In this paper, directional modulation (DM) based on dual-function radar communication system is proposed. To achieve the security of information transmission, a beam weight vector set is established. The reference beam weight vector is initially designed and the remaining weight vectors are derived from it, by minimizing the differences between them. The transmitting beams shaped by the designed weight vectors are almost the same in radar main lobe, but differ in the amplitudes and phases towards the direction of intended communication receivers. The communication receivers decode the data based on its radiated beam. The proposed communication process is secure against intercept from directions other than the pre-assigned communication directions. Simulation results are provided for performance evaluation and to demonstrate the effectiveness of the proposed scheme.

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.

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.

The dual-function radar communication (DFRC) system is an important means to alleviate spectrum congestion. In this paper, we propose an information-embedding DFRC scheme through combining group frequency hopping (FH) code selection with phase-shift keying (PSK) modulation. Concretely, in each radar sub-pulse, first, all the FH codes are grouped and allocated to each antenna in turn. In order to make the distribution of FH codes in one antenna be more uniform, the allocation pattern between groups and transmit antennas performs cyclic shift from one sub-pulse to another. Second, each transmit antenna selects one active FH code from the allocated group according to the transmitted communication symbols. Third, given the FH code per antenna, the FH signal is further modulated by PSK to convey additional information. Moreover, a low-complexity two-stage method is presented to decode the FH code and PSK symbol separately. Simulation results are provided to demonstrate the effectiveness of the proposed information-embedding scheme.

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.

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.

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.