A single-carrier quasi-orthogonal transmission scheme for asynchronous cooperative relay networks

A single-carrier quasi-orthogonal distributed block space-time coding scheme for a wireless collaborative network with one relaying stage composed of four nodes is proposed. This block quasi-orthogonal design can attain full diversity and maximum rate, and is based on simple amplify-and-forward processing at the relay nodes. A cyclic prefix is introduced into the block transmission to overcome channel delay mismatches in the paths through the four relays. In single-carrier operation, these delays are shown to introduce inter-symbol-interference (ISI) in the destination signal. A linear pre-processing scheme is therefore designed to mitigate this ISI through maximizing signal-to-interference-plus-noise ratio (SINR) at the receiver in combination with iterative equalization. To reduce the computational complexity of this scheme the underlying interference matrices are rendered sparse by the pre-processing operation. Simulation studies confirm the improvement in SINR of the proposed approach as compared to one which only uses rectangular pre-windowing.