Beamforming Design of ISAC System for Enhancing Sensing Distance

In this paper, a dual-functionality base station (BS) integrated sensing and communication (ISAC) is exploited to sense one intended target and communicate with multiple users simultaneously. Meanwhile, rate splitting multiple access (RSMA) technology is used to improve communication quality. We formalize a problem aimed at maximizing sensing distance by optimizing the beamforming design of the BS and the allocation of common rate portions, where the signal to interference plus noise ratio (SINR) gain constraint of sensing echo signal and the individual communication rate requirements of each user are satisfied. Due to the non-convexity of the formulated problem, a successive convex approximation (SCA)-based algorithm is proposed to tackle it. Simulation results manifest that as the transmit power increases, the achievable sensing distance increases, and as the SINR threshold of the sensing echo signal increases, the achievable sensing distance decrease. Furthermore, it indicates that the RSMA-based protocol offers superior sensing distance gain compared to the SDMA-based protocol. This performance advantage becomes more pronounced when the communication rate threshold is high, resulting in a relatively large performance gap between the two protocols.