Optimizing Uplink Multi-user Performance in ISAC System with RFID Backscatter

This paper investigates an uplink multi-user integrated sensing and communication (ISAC) framework incorporating RFID backscatter communication, where a base station (BS) simultaneously receives data from multiple uplink users and performs sensing to detect an RFID tag within its beam coverage. We formulate a novel joint beamforming optimization problem to maximize the cumulative uplink rate across all users, subject to stringent minimum Quality of Service (QoS) thresholds for both the RFID tag sensing accuracy and each user’s data transmission. To address the inherent non-convexity due to complex interdependencies among variables, we employ a Lagrangian dual transformation method to decouple the objective, followed by an alternating optimization (AO) algorithm for efficient and reliable convergence. The proposed algorithm’s efficacy is substantiated through extensive numerical simulations, which demonstrate its performance across varying system parameters such as BS antenna array configuration, power budgets of the BS and uplink users, and minimum QoS demands. Additionally, we quantify the impacts of user density and channel dynamics, offering insight into practical system design considerations for ISAC setups in dense and heterogeneous network environments.