RIS-Aided ISAC Design With Low-Resolution DAC/ADC and Discrete Phase Shifters

Abstract

Reconfigurable intelligent surface (RIS)-aided integrated sensing and communications (ISAC) systems are promising for next-generation wireless networks, enabling high spectral efficiency and seamless coverage. However, large-scale deployment is constrained by the complexity and cost of high-precision hardware components. Although low-resolution architectures provide a cost-effective alternative, existing studies lack a comprehensive system-level design tailored to low-resolution RIS-aided ISAC. This paper proposes a full-chain low-resolution framework that jointly optimizes the transmit waveform, receive beamforming, and RIS reflection coefficients under low-resolution DAC/ADC constraints and discrete phase-shifter limitations. A closed-form expression for the signal-to-quantized-clutter-plus-noise ratio (SQCNR) is derived, and the symbol error rate (SER) of symbol-level precoding (SLP) with PSK/QAM modulation is analyzed. Both sensing and communication metrics are then unified into a joint optimization framework that explicitly balances sensing and data transmission performance. An Alternating Projection (AP) strategy is employed to decouple the transmit waveform and RIS phase-shift design, and the resulting subproblems are solved via Majorization–Minimization using convex surrogate relaxations. Simulation results validate that the proposed framework achieves superior joint sensing–communication performance compared with existing benchmark schemes.