Joint Beamforming and Frame Structure Design for ISAC Networks Under Imperfect Synchronization

The integrated sensing and communication (ISAC) technology is becoming more and more attractive when applying multiple-input multiple-output (MIMO) technique on millimeter wave (mmWave) bands in the beyond the fifth generation (B5G) wireless networks. This paper considers the joint design on beamforming and frame structure to minimize the square position error bound (SPEB) of the localization in an ISAC mmWave MIMO system under transmission rate requirement constraints. Firstly, an uplink-downlink two-way communication framework is formulated to study the tradeoff between localization accuracy and transmission rate considering the imperfect synchronization between the base station and users. Then, a joint frame structure and beamforming optimization scheme is proposed to maximize the localization accuracy while ensuring the uplink and downlink transmission rates with imperfect synchronization. Simulation results show the proposed method can reduce the error by 36.2% compared to the one-way algorithm concerning the localization accuracy, and can reach the balance between localization and communication.