Code-Space-Orthogonal PMCW MIMO ISAC: Precoding-Driven Separation and Radar Improvement

Benefiting from its attractive performance in radar sensing and interference suppression, the phase-modulated continuous waveform (PMCW) has drawn considerable attention in the studies of integrated sensing and communications (ISAC). Addressing its drawbacks in communications resource efficiency, a code-orthogonal PMCW (CO-PMCW) transmission scheme was proposed, where the communication and radar signals are separated in the code domain, allowing simultaneous transmission of them. While the achievable throughput is significantly improved, the non-ideal cross-correlation function between the two signals inevitably leads to interference between them. This paper presents a multiuser multiple-input multiple-output (MU-MIMO) ISAC system design for code-space-orthogonal PMCW (CSO-PMCW), where the interference issue is further addressed in the spatial domain by customized beamforming, and the designed radar denoising and fine estimation algorithm further improves the radar dynamic range and sensing accuracy. Finally, a real-world-based channel model is constructed and employed as the simulation environment for examining the applicability of the designed system. The results demonstrate the favorable performance of the CSO-PMCW system in realistic scenarios.