A simple quasi-orthogonal space-time scheme for use in asynchronous virtual antenna array enabled cooperative networks

In this paper we present a novel full-rate and full-diversity quasi-orthogonal space-time block coding scheme for use in asynchronous cooperative relay networks. A variant of orthogonal frequency division multiplexing (OFDM) is implemented at the source node to mitigate the effects of random delays at the relay nodes, which operate in a simple amplify-and-forward mode. Utilizing a feedback channel, a simple phase rotation is applied at the relay nodes to extract full order diversity. A simple feedback quantization approach which reduces the overhead in the feedback channel for practical systems is also proposed. Average bit error rate simulations confirm the utility of the schemes.