Capacity autocorrelation characteristic of MIMO systems over Doppler spread channels

To avoid excessive overhead, some MIMO systems adopt simple feedback that does not provide detailed channel state information (CSI) but also indicates the state of channel capacity utilization. According to the utilization information, transmitter can perform adaptive coding and modulation. The reliability of the feedback signal with delay Δt is studied in this paper in terms of the capacity autocorrelation characteristic, and impacts of antenna numbers and vehicle speed on the required delay are derived.