2025/12/22 by Jung, Seongkyu, Lee, Namyoon, Park, Jeonghun
#FOS: Electrical engineering #Signal Processing (eess.SP) #electronic engineering #information engineering
paper · doi:10.48550/arxiv.2512.19013
This paper studies precoder design for secure MIMO integrated sensing and communications (ISAC) by introducing the MIMO-ME-MS channel, where a multi-antenna transmitter serves a legitimate multi-antenna receiver in the presence of a multi-antenna eavesdropper while simultaneously enabling sensing via a multi-antenna sensing receiver. Using sensing mutual information as the sensing metric, we formulate a nonconvex weighted objective that jointly captures secure communication (via secrecy rate) and sensing performance. A high-SNR analysis based on subspace decomposition characterizes the maximum achievable weighted degrees of freedom and reveals that a quasi-optimal precoder must span a "useful subspace," highlighting why straightforward extensions of classical wiretap/ISAC precoders can be suboptimal in this tripartite setting. Motivated by these insights, we develop a practical two-stage iterative algorithm that alternates between sequential basis construction and power allocation via a difference-of-convex program. Numerical results show that the proposed approach captures the desirable precoding structure predicted by the analysis and yields substantial gains in the MIMO-ME-MS channel.