Constant Modulus Waveform Design with Space-Time Sidelobe Reduction for DFRC Systems

Abstract: Dual-function radar-communication (DFRC) is a key enabler of location-based services for next-generation communication systems. In this paper, we investigate the problem of designing constant modulus waveforms for DFRC systems. We consider the joint optimization of the spatial beam pattern and space-time correlation levels for better separating multiple targets in different angle and delay bins. In particular, we use the space-time correlation function to quantify the correlations between different angle and delay bins and formulate integrated sidelobe levels (ISLs). To serve communication users, we employ constructive interference (CI)-based precoding to modulate information symbols, which leverages distortion induced by multiuser multiple-input multiple-output (MU-MIMO) and radar transmission. We propose two solution algorithms based on the alternating direction method of multipliers (ADMM) and majorization-minimization (MM) principles, which are effective for small and large block sizes, respectively. The proposed ADMM-based solution decomposes the nonconvex formulated problem into multiple tractable subproblems, each of which admits a closed-form solution. To accelerate convergence of the MM-based solution, we propose a novel majorizing function for complex quadratic functions. After majorization, we decompose the approximated problem into independent subproblems for parallelization, mitigating the complexity that increases with block size. We evaluate the performance of the proposed algorithms in comparison to the existing DFRC algorithm. Simulation results demonstrate that the proposed methods can substantially enhance the detection and estimation performance due to reduced space-time correlation levels.