Adaptive soft-output detection in MIMO systems

In this paper, we investigate soft-output detection for multiple-input multiple-output (MIMO) systems over wireless fading channels. Considering the list sphere decoder (LSD) algorithm and taking advantage of the temporal correlation in a Rayleigh fading MIMO channel, an adaptive method is proposed to reduce the complexity of the list detector for evaluating the log-likelihood ratio (LLR) values. The list of best candidates at the channel output is adaptively updated from the past channel information by employing a measure that offers an appropriate performance/complexity tradeoff. Moreover, the lists are centered around a low complexity near maximum likelihood (ML) point which is also adaptively estimated.