A robust and low complexity adaptive algorithm for MIMO Eigenmode transmission system with experimental validation

Adaptive MIMO eigenmode transmission system is a promising candidate for future high data rate wireless systems. However under practical conditions when channel state information (CSI) is imperfect, the eigenbeams lose their orthogonality and inter-eigenmode interference occurs. No work so far has attempted to consider the effects of inter-eigenmode interference on the adaptive signaling algorithm which is essential in ensuring a practical and robust adaptive system. Thus in this paper, we will propose an adaptive algorithm that account for CSI imperfections and practical operating conditions explicitly, namely imperfect channel estimation at receiver, delayed quantized feedback to transmitter and a spatially correlated continuous fading channel. A metric for the SINR of each eigenmode under the above practical conditions is identified and this metric is used in the adaptive signaling to ensure a robust adaptive algorithm. Both simulation and experimental results showed that the proposed algorithm is robust and superior to conventional schemes under practical operating conditions. Furthermore. a low complexity Look Up Table-based computation method is also devised.