A Lattice-Reduction Aided Max-Log List Demapper for Iterative Coded MIMO Receiver

Abstract

The max-log list demapper has been widely employed in the implementation of a coded multiple-input multiple-output (MIMO) receiver, where only a candidate-list of signal vectors is examined in the likelihood-ratio calculation to reduce complexity. Traditionally, the candidate-list is generated in the original-lattice domain which, unfortunately, results in a severe degradation in the performance of demapper if the channel is in ill-condition. In this paper, a new lattice-reduction aided max-log list demapper is proposed for iterative receivers in which the candidate-list is generated after a successive cancellation of multi-layer interference in the lattice-reduced domain. Thanks to the newly designed metric and search algorithm for the generation of the candidate-list, the proposed demapper provides significant gains over the existing methods, especially for the cases with a small list size and/or under a spatially-correlated channel. The prior information coming out of the decoder is also exploited to lower the complexity of the demapper.