A Brief Introduction on Joint Radar and 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 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) 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.

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

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.

In this paper, we investigate the physical layer security of multiuser multi-input single-output (MU-MISO) communication and colocated multi-input multi-output (MIMO) radar coexistence systems, in which the strong radar signals are exploited as inherent jamming signals to disrupt mali-cious receptions. The transmit beamformers of communication and radar systems are jointly designed to ensure the secure transmission by minimizing the maximum eavesdropping signal-to-interference-plus-noise ratio (SINR) on multiple legitimate users, while satisfying the quality-of-service (QoS) of legitimate transmission, the requirement of radar target detection, and the transmit power constraints of radar and communication systems. An efficient fractional programming (FP) and semi-definite relaxation (SDR) based algorithm is proposed to solve the non-convex optimization problem. Simulation results verify the advancement of the proposed joint transmit beamforming on secure transmission for radar and communication coexistence systems and the effectiveness of the associate design algorithm.

In this paper, we propose a dynamic spectrum allocation approach for the coexistence of a radar system with a communications system whose operating frequency ranges overlap. We develop a combined mutual information criterion for the joint waveform and power spectrum design to optimize the performance of the radar and communications systems. The performance is evaluated in terms of the minimum separation distance between the coexisting systems under the constraint that a predefined operational SINR must be achieved for both systems. Significant performance gains close to 3.5 dB for the communication system and 1 dB for the radar system are observed in terms of the minimum separation distance compared to the scenario when the waveform with equal power allocation across the frequency bandwidth is used.

In this paper, we consider the problem of finding how a joint radar and communication system should divide its effort between supporting the radar and communication objectives when the system operates in an environment with hostile interference. Our model explores the uncertainty of the jammer’s location by assuming the joint system knows only the a priori probabilities of jammer’s positions. The underlying problem is formulated and solved as a Bayesian game involving the joint radar/communication system and a jammer. We then explore how irrational behavior by the rivals can affect the equilibrium strategies by using prospect theory (PT). It is shown that the PT system strategy is not sensitive to the jammer’s probability weighting parameter, while jammer’s strategy is sensitive to probability weighted parameters of both rivals.

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

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.

In response to the urgent demand for the development of future radar application platforms from single radar functionality toward integrated multifunctional systems, we show an advanced microwave photonic waveform editing method that enables the editing of arbitrary radar waveforms, equipping them with the capability to perform spectrum sensing. This, in turn, expands single-function radar systems into joint radar and spectrum-sensing systems. We theoretically define and calculate the accumulation function of an arbitrary waveform after passing through a specific dispersive medium and utilize this accumulation function to further design a corresponding binary sequence for editing the waveform. After editing, the accumulation function of the edited waveform approximates that of a linearly frequency-modulated (LFM) signal matching the specific dispersive medium. Thus, the edited waveform can be compressed into a narrow pulse after passing through the dispersive medium, realizing the frequency-to-time mapping (FTTM) for achieving frequency measurement or time–frequency analysis. The concept is verified through both simulation and experiment. Using a dispersion-compensating fiber (DCF) with a total dispersion of −6817 ps/nm, arbitrary waveforms, including a 7-bit Barker phase-coded waveform, an LFM waveform, a nonlinearly frequency-modulated (NLFM) waveform, and a waveform with an “E” time–frequency diagram, are edited and further used for microwave frequency measurement and time–frequency analysis in an ultra-wide bandwidth of 36.8 GHz. The temporal resolution and frequency resolution are 2 ns and 0.86 GHz, respectively.

Coexisting radar and communication (CRC) systems on the same spectrum band have been recently recognized as a promising approach to solve the spectrum scarcity problem. Additionally, with the new requirements of achieving higher energy efficiency and restoring the consumed power, an initiative has been exploited to embed both information and energy within the same signal. Motivated by that, this paper presents a unified model to implement the concept of simultaneous wireless information and power transfer (SWIPT) in the coexistence environment between radar and communication systems. Specifically, we propose a novel energy harvesting based CRC model (CRCEH), in which the signals transmitted from both the communication and radar transmitters are precoded towards their conventional targets, communication receiver and radar targets respectively, as well as to an energy harvesting receiver. This system is capable of solving the spectrum scarcity problem as well as supporting low power devices with their energy requirements from the energy harvested at the energy harvesting receiver. The design problem is formulated as maximizing the radar detection probability subject to communication capacity and energy harvesting constraints. However, directly processing the data from the radar receiver requires high computational complexity and hardware costs. In order to circumvent this issue, this paper also proposes to deploy lens antenna array (LNA) to CRCEH system to sharply direct the signals to the energy harvesting receiver together with their respective destinations. Since LNA is able to focus the signal power on a subset of antennas, we may only deal with the data from the selective antenna subset associated with the maximal power. Numerical results show that the proposed method is able to achieve improved performance in terms of radar detection under communication capacity constraints compared to the conventional approaches besides the great benefit of harvesting the energy to feed some limited energy devices.

The high peak to average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals challenge the efficiency of joint radar and communication system. In this paper, we propose a simple PAPR reduction method with a compressive sensing algorithm to help signals recovery. First, the PAPR of OFDM signals is reduced by clipping at the transmitter. Second, we can restore the clipped signals at the receiver with the proposed method. Simulation results reveal the bit error rate (BER) performance can be improved with the proposed PAPR reduction method compared to the traditional clipping method. In addition, the radar performance for the PAPR-reduced system is observed to around be the same as that original OFDM system.

This paper derives the performance of the joint radar and communication system (JRCS). Firstly, for the radar application of the JRCS, we derive the mutual information (MI) between target and received signal in additive Gaussian noise. For communication, we derive the communication data rate that the JRCS can achieve. Then, under partial coexistence between radar and communication bands, the MI and communication data rate for the JRCS are derived. In terms of the overlap between the received radar and communication signals, the successive interference cancellation (SIC) scheme is adopted. Finally, the provided numerical results demonstrate the performances for the JRCS.