Radar Coexistence Research Articles

Communications and Radar Coexistence in the Massive MIMO Regime: Uplink Analysis

This paper considers the uplink of a massive MIMO communication system using 5G New Radio-compliant multiple access, which has to co-exist with a radar system using the same frequency band. A system model taking into account the reverberation (clutter) produced by the radar system onto the massive MIMO receiver is proposed. In this scenario, several receivers for uplink channel estimation and data detection are proposed, ranging from the simple channel-matched beamformer to the zero-forcing and linear minimum mean square error receivers for clutter disturbance rejection, under the two opposite situations of perfectly known and completely unknown clutter covariance. A theoretical analysis is also provided, deriving a lower bound on the achievable uplink spectral efficiency and the mutual information between the input Gaussian-encoded symbols and the observables available at the communication receiver of the cellular massive MIMO system: regarding the latter, in particular, it is shown that, in the large antenna number regime, and under the assumption of perfect channel state information (CSI), the effect of radar clutter at the base station is suppressed and single-user capacity may be restored. Numerical results, illustrating the performance of the proposed detection schemes, confirm the findings of the theoretical analysis, and permit quantifying the system robustness to clutter effect for increasing number of antennas at the base station.

Time modulated array sideband suppression for joint radar-communications system based on the differential evolution algorithm

To satisfy the need of electronic system integration in civil and military, and mitigate the tension of spectrum resource, the demand for coexistence of radar and communication systems is increasing rapidly. As an important branch of radar-communications integration, the time modulated array (TMA) based coexistence method has been proposed recently. The TMA has an inherent drawback that there are many undesired sideband signals generated simultaneously. However, the existing TMA sideband suppression algorithms do not suit the radar-communications integration scenarios. In this paper, a time modulated array sideband suppression method for joint radar-communications system based on the differential evolution (DE) algorithm is proposed. We first introduce some facts of the time modulated array. Then, the radar-communication coexistence strategy is presented, and the form of integration signal is derived. Moreover, combined with a positive and negative alternating periodic modulation function, the TMA sideband suppression for radar-communications coexistence scenarios based on the DE algorithm is proposed. The sideband patterns of the TMA can be significantly lowered by optimizing the opening and closing moments of each element. Finally, the validity of the theoretical derivations is demonstrated via simulations.

Power optimisation of simultaneously transmitted communication and radar waveforms from a common array

Synthesising radar and communication waveforms in different directions using a common array is a hardware-saving solution for the coexistence of communication and radar in competitive spectrum environments. Here, the authors establish the problem of designing array probing signal to maximise power of the synthesised communication and radar waveforms, given array transmitting power, under no-waveform-error constraint and unit-modular-array-probing-signal constraint. Alternating direction method of multipliers (ADMM) is used to solve this problem. The results of numerical experiments show that, by solving this problem with ADMM, error of the synthesised waveforms can be completely eliminated, and the power of synthesised waveforms is almost optimal.

Sparse transmit array design for dual-function radar communications by antenna selection

Dual-function radar communications (DFRC) systems have recently been proposed to enable the coexistence of radar and wireless communications, which in turn alleviates the increased spectrum congestion crisis. In this paper, we consider the problem of sparse transmit array design for DFRC systems by antenna selection where same or different antennas are assigned to different functions. We consider three different types of DFRC systems which implement different simultaneous beamformers associated with single and different sparse arrays with shared aperture. We utilize the array configuration as an additional spatial degree of freedom (DoF) to suppress the cross-interference and facilitate the cohabitation of the two system functions. It is shown that the use of sparse arrays adds to improved angular resolution with well-controlled sidelobes on DFRC system paradigm. The utilization of sparse arrays in DFRC systems is validated using simulation examples.

Joint radar-communications design based on time modulated array

The demand for coexistence of radar and communication systems is increasing rapidly in recent years. In this paper, we propose a joint radar-communications design based on time modulated array (TMA) to satisfy the need of electronic system integration in civil and military, and mitigate the tension of spectrum resource. First, we investigate the basic characteristics of the TMA. Then, we present a TMA-based waveform design algorithm for joint radar-communications. By using the derived results, a dual-function radar-communication (DFRC) system is established, which can detect targets in a large scanning range and maintain the communication direction static simultaneously, while avoiding the mutual interference. Moreover, the communication direction can be adjusted easily as needed. The validity of the theoretical derivations is demonstrated via simulations.

Joint System Design for Coexistence of MIMO Radar and MIMO Communication

This paper considers the joint design of a multiple-input multiple-output (MIMO) radar with co-located antennas and a MIMO communication system. The degrees of freedom under the designer's control are the waveforms transmitted by the radar transmit array, the filter at the radar array and the code-book employed by the communication system to form its space-time code matrix. Two formulations of the spectrum sharing problem are proposed. First, the design problem is stated as the constrained maximization of the signal-to-interference-plus-noise ratio at the radar receiver, where interference is due to both clutter and the coexistence structure, and the constraints concern both the similarity with a standard radar waveform and the rate achievable by the communication system, on top of those on the transmit energy. The resulting problem is nonconvex, but a reduced-complexity iterative algorithm, based on iterative alternating maximization of three suitably designed subproblems, is proposed and analyzed. In addition, the constrained maximization of the communication rate is also investigated. The convergence of all the devised algorithms is guaranteed. Finally, a thorough performance assessment is presented, aimed at showing the merits of the proposed approach.

Robust MIMO Beamforming for Cellular and Radar Coexistence

In this letter, we consider the coexistence and spectrum sharing between downlink multi-user multiple-input-multiple-output (MU-MIMO) communication and an MIMO radar. For a given performance requirement of the downlink communication system, we design the transmit beamforming such that the detection probability of the radar is maximized. While the original optimization problem is non-convex, we exploit the monotonically increasing relationship of the detection probability with the non-centrality parameter of the resulting probability distribution to obtain a convex lower-bound optimization. The proposed beamformer is designed to be robust to imperfect channel state information (CSI). Simulation results verify that the proposed approach facilitates the coexistence between radar and communication links, and illustrates a scalable tradeoff between the two systems' performance.

Spectral Coexistence of MIMO Radar and MIMO Cellular System

This paper details designing the precoder of a MIMO-radar spectrally-coexistent with a MIMO cellular system. Spectrum sharing with zero or minimal interference is achieved by using, respectively, the conventional switched null space projection (SNSP) or the newly proposed switched small singular value space projection (SSSVSP). Loss in radar target localization capability due to precoding can be compensated by using SSSVSP instead of SNSP to some extent but increasing the number of radar antenna elements is more effective.

Feasibility of Cellular Networks and Radar Coexistence in S Spectrum Band

Feasibility of Cellular Networks and Radar Coexistence in S Spectrum Band

Coexistence of Outdoor Wi-Fi and Radar at 3.5 GHz

Coexistence between radar and outdoor wireless fidelity (Wi-Fi) needs thorough study since the IEEE 802.11 working group (WG) opposed the latest rules in 3550–3700 MHz (the 3.5 GHz band) that require “exclusion zones.” This letter proposes a method that suppresses Wi-Fi-to-radar (WtR) interference, in which a Wi-Fi transmitter (TX) is selected to avoid beam angles toward the victim radar. It is distinguished from prior schemes since it ensures that the Wi-Fi remains operable while suppressing the WtR interference.