Joint Transceiver Design and Mode Selection for NOMA-ISAC in NAFD Cell-Free mMIMO Systems

Integrated sensing and communication (ISAC) has garnered considerable attention for its capacity to simultaneously communicate and sense the surrounding environment. To enhance ISAC systems, non-orthogonal multiple access (NOMA) can be leveraged to mitigate interference between communication and sensing functions. This paper explores the transceiver design and mode selection for NOMA-ISAC in network-assisted fullduplex (NAFD) cell-free massive multiple-input multiple-output (mMIMO) systems. We firstly derive expressions for both the data rates of communication users and the sensing signal-to-interference-plus-noise ratios (SINRs) of radar targets. Subsequently, we formulate a joint optimization problem aimed at maximizing the sum sensing SINR while respecting communication constraints. To address this, we propose an algorithm based on sequential convex approximation (SCA) coupled with simulated annealing (SA) to obtain the optimal solution. Simulation results demonstrate the efficacy of our proposed algorithm in significantly enhancing system performance.