Joint Processing and Transmission Energy Optimization for ISAC in Cell-Free Massive MIMO with URLLC
This work addresses energy-efficient integrated sensing and communication (ISAC) in cell-free massive MIMO downlink systems under joint ultra-reliable low-latency communication (URLLC) and multistatic sensing constraints. Method: It proposes the first end-to-end energy-saving optimization framework jointly modeling both sensing processing energy consumption and communication transmission energy consumption. To tackle the non-convex joint optimization of transmit power and transmission blocklength, two efficient algorithms are developed—based on feasible point pursuit-successive convex approximation (FPP-SCA) and concave–convex procedure (CCP)—with fractional programming incorporated to handle the energy-efficiency ratio objective. Contribution/Results: The proposed joint design significantly reduces total energy consumption compared to conventional decoupled approaches. Numerical results show that increasing the number of access points raises sensing energy consumption; raising the sensing SINR threshold enlarges total energy consumption while narrowing the performance gap between the two algorithms.