Beamforming Design for Near-Field Integrated Sensing and Communications.

In order to meet the increasing demand for communication and sensing performance, integrated sensing and communications (ISAC) systems are developed towards using larger scale antenna arrays and higher/wider frequency bands, which will bring significant near-field effect. In this case, the electromagnetic (EM) wave must be accurately modeled as the spherical wave, which leads to new challenges and opportunities in the design of ISAC systems. This paper aims to investigate the beamforming design for near-field ISAC. Joint beamforming of both communication symbols and sensing waveforms is optimized to minimize the mean square error (MSE) between the desired and generated beam pattern under constraints of transmit power and communication quality of service (QoS). Due to the non-convexity of the proposed optimization problem, the majorization-minimization (MM) algorithm is leveraged to convert the problem and solve it iteratively. A two-dimensional beam pattern is demonstrated to visually verify the advantage of the proposed beamforming design in the near-field scenario. In addition, simulation results numerically illustrate the trade-offs between the sensing and communication performance of the design.