A relaxed maximum likelihood approach to blind channel estimation and symbol detection in MIMO systems with orthogonal space-time block codes

We present a novel approach to blind symbol detection in multiple-input multiple-output (MIMO) systems that use orthogonal space-time block codes. Our approach is based on a relaxed maximum likelihood (ML) joint channel and symbol estimation. The proposed technique has a simple closed-form solution and is free of most of the shortcomings of the previously presented blind receivers. In particular, there is no signal-to-noise ratio (SNR) penalty, as in differential encoding techniques, provided that the coherence time of the channel is large enough. Moreover, our approach does not use any pilot symbols as some other (semi-)blind techniques do.