Introducing User Grouping to Counteract Channel Correlation in IRS-Assisted ISAC

Intelligent reflective surface (IRS) assisted integrated sensing and communications (ISAC) is a promising technology for future mobile communications. However, high channel correlation, which may significantly degrade the performance of ISAC, has been overlooked. This letter addresses the issue by introducing user grouping to IRS-assisted ISAC. We design a novel user grouping scheme to minimize intra-group channel correlation. We also derive the asymptotically optimal number of user groups. Moreover, for any user group, we provide a joint base station and IRS beamforming design by applying the alternative optimization strategy, together with the weighted minimum mean squared error and discrete phase shift optimization techniques. Simulation results demonstrate substantial performance enhancement brought by user grouping to IRS-assisted ISAC.