Breaking the Interference Curse in Multi-Target CF-mMIMO ISAC Systems

We consider a cell-free massive multiple-input and multiple-output (CF-mMIMO) integrated sensing and communication (ISAC) system with multiple communication users and sensing targets. In this system, the transmit access points (TX-APs) send signals to communication users and sensing targets. Subsequently, the receive APs (RX-APs) are utilized to receive the reflected signals from both the sensing targets and communication users. To mitigate interference among users and targets, while maintaining satisfactory communication performance, we apply the active channel sparsification (ACS) concept to represent the ISAC system. A max-min sensing signal-to-interference-plus-noise ratio (SINR) problem, that satisfies the minimum communication SINR and the total power constraint, is proposed. To solve this NP-hard optimization problem, a two-step algorithm is proposed, including a joint beam and user selection scheme and a power control scheme. Finally, our numerical results show that the proposed algorithm achieves at least 136% higher sensing SINR compared to the considered benchmarks.