Resource-Efficient ISAC Scheduling for mmWave IoT Networks with Multi-Target Sensing Constraints

Millimeter-wave IoT deployments, such as smart factories and automated warehouses, require both wireless connectivity and environmental awareness. Integrated sensing and communication (ISAC) offers a practical path to meeting both needs on a shared hardware and spectrum platform. This paper studies downlink rate maximization in a single-BS, single-downlink-user mmWave IoT-ISAC system with periodic multi-target sensing under strict per-frame detection constraints. We focus on a communication-centric setting in which sensing functionality is dedicated to object detection, and resources are shared to satisfy sensing requirements without drastically degrading the downlink rate. A sensing slot is reserved in each frame, where PRBs are shared between sensing and communication, and sensing PRBs are assigned to targets under a frequency-division multiple access (FDMA) constraint. The resulting problem couples binary PRB-target assignments with continuous power variables, forming a combinatorial optimization problem. We propose C-SAFE (Communication-aware Sensing Assignment with Feasibility Enforcement), a low-complexity greedy framework that constructs feasible sensing assignments, enforces detector-driven sensing requirements via power allocation, and allocates residual power to communication PRBs via water-filling. Simulations show that C-SAFE achieves an average rate gain of approximately 43% over the time-domain baseline and 1.2% over the sensing-greedy baseline.