Joint Beamforming and Scheduling for Integrated Sensing and Communication Systems in URLLC: A POMDP Approach
Xiaoyu Zhao, Ying–Jun Angela Zhang · IEEE Transactions on Communications · 2024
Integrated Sensing and Communications (ISAC) is an emerging 6G technology to address the increasing demands for ubiquitous sensing and communication. Achieving Ultra-Reliable and Low-Latency Communication (URLLC) with ISAC has been relatively under-investigated in the existing literature. In this paper, we investigate joint beamforming and scheduling for an ISAC-enabled system to fulfill URLLC requirements. We focus on a typical URLLC scenario where periodic and aperiodic traffic flows coexist. Specifically, the aperiodic traffic is triggered by sensing the stochastic environment. We propose a joint beamforming and scheduling scheme to sense the environment and transmit traffic simultaneously, where efficient scheduling is obtained by exploiting sensing results. To analyze the latency and reliability performance of the proposed scheme, we first describe the system as a Partially Observable Markov Decision Process (POMDP). Then, we analytically express the latency and reliability performance as the probability of successful transmission within the latency constraint. Based on this, we formulate an optimal performance tradeoff for the periodic and aperiodic traffic and obtain an optimal tradeoff by a Dynamic Programming (DP)-based algorithm. Furthermore, we reveal some insightful properties of the optimal tradeoff and the optimal policy. Simulation results show that the optimal tradeoff outperforms other tradeoffs of benchmark algorithms.