SAGE algorithm for channel estimation and data detection with tracking the channel variation in MIMO system

In recent years, Multiple-Input Multiple-Output (MIMO) systems with some transmit and receive antennas have attracted much attention in radio environments. In MIMO systems, the channel estimation is important to distinguish transmit signals from multiple transmit antennas. The Space-Alternating Generalized Expectation-maximization (SAGE) algorithm is known to be good for the channel estimation and the data detection. However, the SAGE algorithm has not been applied to MIMO systems. In this paper, we propose a SAGE algorithm for the channel estimation and data detection in MIMO systems. In addition, we propose a simplified SAGE algorithm for the channel estimation and the data detection with tracking the channel variation in MIMO systems. In the simplified SAGE algorithm, we divide a transmit frame into some subblocks and apply the SAGE algorithm to each subblock, and we use the channel estimates in the previous subblock as the initial channel estimates in the current subblock. According to the division of the transmit frame, the computational complexity is decreased. In addition, the simplified SAGE algorithm can track the channel variation by using the channel estimates transferred between the subblocks.