Joint MIMO channel iracking and symbol decoding using Kalman filtering

In this paper, the problem of channel tracking is considered for multiple-input multiple-output (MIMO) communication systems where the MIMO channel is time-varying. We consider a class of MIMO systems where orthogonal space-time block codes are used as the underlying space-time coding schemes. For such systems, a two-step MIMO channel tracking algorithm is proposed. As the first step, Kalman filtering is used to obtain an initial channel estimate for the current block based on the channel estimates obtained for previous blocks. Then, in the second step, the so-obtained initial channel estimate is refined using a decision-directed iterative method. We show that, due to specific properties of orthogonal space-time block codes, both the Kalman filter and the decision-directed algorithm can be significantly simplified. Simulation results show that the proposed tracking method can provide results in a symbol error rate performance that is 1 dB better than that of the differential receiver.