Extrapolation of Time-Varying MIMO Channels for an E-SDM System

Multiple-input multiple-output (MIMO) systems using eigenbeam space division multiplexing (E-SDM) perform well and have increased channel capacities. However, channel state information (CSI) is required at a transmitter, and the performance of the systems depends much on the accuracy of the CSI at a transmitter and a receiver. In time-varying fading environments, the channel change between the transmission weight matrix determination time and the actual data transmission time causes the system performance to degrade. To compensate for the channel error, a linear extrapolation method has been proposed for a time division duplexing system. Unfortunately, the performance still deteriorates as the maximum Doppler frequency increases. Here, two new techniques of channel extrapolation are proposed. One is second order extrapolation, and the other is exponential extrapolation. Simulation results for 4tx 4rx MIMO systems show that using the proposed methods, E-SDM system performs better in a higher Doppler frequency region.