Linear maximum likelihood decoding of space-time block coded OFDM systems for mobile communications

A new linear decoder for space time block codes is presented, which enables linear maximum-likelihood decoding in scenarios beyond those described by block-fading models. The new decoder employs linear combinations of received signals With weights designed so as to yield orthogonal estimates for all encoded symbols regardless of channel variations within the block transmission, provided that the channel is known. The combination weights are scalar functions of the channel estimates, obtained through systematic rotations over the decoding matrices of the linear maximum-likelihood decoder for the block-fading case. The proposed decoder yields good performance with low-complexity and is therefore suitable for low-cost portable receivers supporting space time transmit diversity at the downlink of high data-rate wireless mobile communication systems. Combined With OFDM technology, the technique yields a low-complexity receiver that is effective in combating both time and frequency selectivities, and provides a tool to add flexibility to wireless local area network systems and to offer high data-rate services with support to mobility.