Cooperative Diversity with Fast HARQ for Delay-Sensitive Flows

This work addresses the problem of a fast hybrid automatic-repeat-request (HARQ) scheme intended for transporting delay-sensitive flows in a cooperative diversity (CD) environment. This CD with fast HARQ scheme allows the retransmission for only one time via the cooperating user (i.e. partner) or via both the sender and the partner simultaneously. A complementary link packet is used for retransmissions. The retransmission policy can be adjusted based on the qualities of channels among the sender, the partner, and the receiver and the application layer protocol data unit size by using the application throughput as the objective. For this presented scheme, we completely derive the application throughput formulas, which are then validated via simulations. Next, the CD with optimized fast HARQ scheme is shown able to achieve better throughput than effective throughput of other CD with ARQ schemes in various Nakagami-m slow-fading environments. As a result, the fast HARQ scheme should be an excellent ARQ mechanism for the real-time multimedia transport in CD environments.