Detection ordering in tree search detection for MIMO wireless systems

An optimal log-likelihood ratio (LLR) ordering algorithm used in the tree search algorithm is presented. A simplified LLR ordering scheme employed in uncoded systems and an exact LLR ordering scheme employed in coded systems are proposed. The proposed ordering algorithm utilizeds not only the channel state information, but also the receives signal as well as a priori information from the decoder, thus the transmitted signals are detected in the order of their reliability information. Simulation shows that LLR ordering algorithms achieve significant performance gain in uncoded systems and a faster convergence in coded systems.