Adaptive equalization of multiple-input multiple-output (MIMO) channels

The paper proposes and investigates a new approach to adaptive spatio-temporal equalization for MIMO (multiple-input multiple-output) channels. A system with n transmit and m (m/spl ges/n) receiver antennas is assumed. A decision feedback equalizer is considered. A least squares solution is first formulated, based on which a recursive solution using Riccati recursions is proposed. The proposed solution is tested by simulating the MIMO system. It is shown that the adaptive solution achieves the same performance as the optimum least squares solution. The effect of the nondiagonal channel elements (acting as interference) on the system performance is also studied. It has been shown that in order to achieve better performance, the interference from nondiagonal channel elements needs to be minimized. This can be done by using orthogonal transmission. Moreover the proposed solution do not require channel identification and will also enable equalizer adaptation to channel changes.