Integration of hybrid ARQ and space-time coding through embedded quasi-orthogonal block codes

This work presents a novel use of the quasi-orthogonal space-time coding structure to greatly enhance the scalability and efficiency of wireless communication systems through the integration of ARQ and space-time block codes. The key concept is to integrate space-time coding with hybrid ARQ by utilizing joint receivers upon ARQ retransmissions. Our objective is to reduce the retransmission bandwidth when network conditions are suitable. The joint detection scheme requires standard maximum likelihood algorithms. To achieve low complexity, Alamouti codes and quasi-orthogonal codes are adopted. We have found that for moderate channel conditions, 39 percent of the retransmission bandwidth can be saved with very little performance or complexity penalty.