Distributed Space-Time Code with Mutual Information Based Soft Information Relaying

In this letter, we investigate a distributed space-time coded soft information relaying. In particular, we focus on mutual information based soft forwarding (MIF) scheme with Alamouti space-time block code. In order to achieve a full diversity order, we propose a weighted amplifying factor based on average soft noise variance instead of instantaneous one. The exact analytical expression for average soft noise variance is first derived. A tight upper bound of the average soft noise variance is also derived in closed-form. It is shown that the proposed distributed MIF Alamouti scheme can achieve a full diversity order, and outperforms various distributed Alamouti schemes reported in the literature.