Characteristics and Channel Capacity Studies of a Novel 6G Non-Stationary Massive MIMO Channel Model Considering Mutual Coupling

In the sixth generation (6G) wireless communication networks, ultra-massive multiple-input multiple-output (MIMO) communication is one of the most promising technologies. In ultra-massive MIMO channels, the mutual coupling (MC) effect is more obvious when antenna elements are more closely spaced. In this paper, a novel 6G space-time-frequency (STF) non-stationary massive MIMO channel model is proposed, which jointly considers MC, antenna efficiency, and near-field steering vectors of different antenna topologies. As the Shannon capacity theorem is based on the wide-sense stationary (WSS) channel assumption and cannot be applied to non-stationary channels, we propose a novel non-stationary channel capacity calculation method that divides the non-stationary channel into WSS sub-channels. Important statistical properties and channel capacities of the proposed channel model are derived and verified by ultra-massive MIMO channel measurements and data post-processing. The results show that the simulated spatial cross-correlation function (CCF) and channel capacity considering MC and antenna efficiency are closer to measured results. It also shows that antenna topologies have an impact on channel capacities. Furthermore, channel capacities using the proposed novel calculation method match the measured channel capacities in non-stationary channels.