Joint MIMO Communications and Sensing with Hybrid Beamforming Architecture and OFDM Waveform Optimization

Abstract

In this article, we consider a multiple-input multiple-output (MIMO) transceiver performing joint communications and sensing (JCAS) using fifth-generation New Radio (5G NR) standard-compliant orthogonal frequency-division multiplexing (OFDM) waveforms. Communication links are maintained with users having multiple spatial data streams over frequency-selective non-line-of-sight channels while simultaneously transmitting separate spatial data streams to different sensing directions, where a portion of the communication data streams’ power is reallocated to the sensing data streams. The received reflections from the environment due to all transmit (TX) streams are used to obtain range–velocity and range–angle maps. Through optimizing the TX precoding and receive combining, inter-user, intra-user, and radar–communications interference are also canceled. In addition, streams transmitted in the sensing directions are optimized to minimize the lower bounds of direction-of-arrival and delay estimates jointly, and the solution is analytically derived. The simulation results illustrate that the JCAS system can reliably perform target detection while minimizing lower bounds compared with a communications-only scenario. Further, the detection probability and estimation errors of sensing can be improved while also controlling the communications capacity of the OFDM waveform, thereby indicating the need to appropriately choose the optimization parameters to obtain an optimal trade-off.