Decoupled Mean Filtering for Calibrated MUSIC Spectrum With Phase-Rotation Precoding Under Cooperative ISAC Systems – From Interference Suppression Perspective

Integrated sensing and communication (ISAC) represents a critical scenario in the sixth-generation (6G) mobile communication, requiring systems to deliver both excellent communication and high-accuracy sensing capabilities. The requirement for high-accuracy sensing presents a major concern in scenarios with a single ISAC base station (BS). While a multi-BS collaborative ISAC system offers substantial improvements in sensing accuracy, mutual interference among BSs introduces a critical issue for implementation. In this work, we model the mutual interference in the process of multi-BS collaborative sensing and investigate the impact of these interferences on sensing accuracy across different modulation schemes. Based on this, we present a decoupled mean filtering (DMF) algorithm to mitigate interference, which performs effectively at low signal-to-interference-plus-noise ratios (SINRs) but shows limited effectiveness at high SINRs. Consequently, we propose an enhanced DMF integrated with the phase rotation precoding (PRP) tailored to various modulation types. The simulation results demonstrate that the proposed DMF-PRP algorithm effectively suppresses the sensing mutual interference and exhibits superior sensing accuracy compared to the existing schemes.