Non-coherent and mismatched-coherent receivers for distributed STBCs with amplify-and-forward relaying

Cooperative diversity is a transmission technique where multiple nodes in a network cooperate to form a virtual antenna array realizing the benefits of spatial diversity in a distributed fashion. The coherent scenario considered in most existing work on cooperative diversity assumes the availability of perfect channel state information at the relay and destination terminals and is highly unrealistic in practical applications. In this paper, we investigate non-coherent and mismatched-coherent receivers for a cooperative diversity scheme assuming both quasi-static and time-varying fading channels for the underlying cooperative links. Specifically, we consider a distributed spacetime block coded (STBC) system in a single-relay scenario operating in the amplify-and-forward relaying mode. Exploiting the orthogonal structure of distributed STBC, we first derive a non-coherent decoding rule which can be implemented in practice by a Viterbi-type algorithm. Although this decoding rule has been derived assuming quasi-static channels, its inherent channel tracking capability allows its deployment over time varying channels with a promising performance as a sub-optimal solution. As a possible alternative to non-coherent detection, we investigate the performance of mismatched-coherent receiver (i.e., coherent detection with imperfect channel estimation) within the considered relay-assisted transmission scenario. We further compare the performance of non-coherent and mismatchedcoherent receivers to reveal their robustness under various mobility scenarios.