A General 3D GBSM for 6G ISAC Systems Toward 3GPP Standardization Verified by Channel Measurements

In this paper, a general three-dimensional (3D) geometry-based stochastic model (GBSM) for the sixth-generation (6G) integrated sensing and communication (ISAC) systems is proposed. The monostatic sensing, bistatic sensing, and communication channels are considered in the proposed ISAC GBSM. Sensing targets are specifically modeled, incorporating radar cross section (RCS) and single-point/multi-point scattering properties. The proposed model also incorporates shared clusters between the target and background channels, as well as between the sensing and communication channels, while addressing non-stationarities in space-time-frequency (STF) domains through cluster birth-death processes. Based on the proposed channel model, statistical properties in STF, delay, angular, and Doppler domains are comprehensively investigated, including the STF correlation function (CF), delay/angular/Doppler spread, coherence distance/time/bandwidth, and stationary distance/time/bandwidth. Statistical properties of the sensing and communication channels are compared. Also, the impacts of monostatic and bistatic sensing configurations and different target types on statistical properties are thoroughly investigated. These investigations show that the correlation of sensing channels in the STF domain decreases with the increasing target RCS, and that the communication channel exhibits higher correlation than sensing channels.