Transmit Beamforming Optimization for Integrated Sensing and Communication
Haocheng Hua, Jie Xu, Tony Xiao Han
Abstract
This paper studies the transmit beamforming in a downlink integrated sensing and communication (ISAC) system, where a base station (BS) equipped with a uniform linear array (ULA) sends combined information-bearing and dedicated radar signals to simultaneously perform downlink multiuser communication and radar target sensing. Under this setup, we minimize the radar sensing beampattern matching errors, subject to the communication users' minimum signal-to-interference-plus-noise ratio (SINR) requirements and the BS's transmit power constraints. In particular, we consider two types of communication receivers, namely Type-I and Type-II receivers, which do not have and do have the capability of cancelling the interference from the a-priori known dedicated radar signals, respectively. Under both Type-I and Type-II receivers, the nonconvex beampattern matching problems are globally optimally solved via applying the semidefinite relaxation (SDR) technique. It is shown that at the optimality, dedicated radar signals are not required with Type-I receivers under some specific conditions, while dedicated radar signals are always needed to enhance the performance with Type-II receivers. Numerical results show that by exploiting the capability of canceling the interference caused by the radar signals, the case with Type-II receivers results in better sensing performance in terms of beampattern matching error than that with Type-I receivers and other conventional designs.