A New Relay Assisted Hybrid ARQ Scheme

The concept of cooperative communication is based on relay channel model and inspired by MIMO technique. Cooperative communication can bring many merits such as improving the system throughput, decreasing the outage probability and so on. It also might bring an evolution in wireless communication. As a new technique, cooperative communication has been viewed as a key technique in 4G system. HARQ as an effective error control scheme has been used widely. The relay assisted HARQ scheme which combines HARQ and cooperative communication is a really hot research direction now.In this thesis, we introduced cooperative diversity, HARQ technique and the cooperative communication system. Then the classical relay HARQ schemes are analyzed. Based on the above studies, a novel relay assisted HARQ scheme is proposed in the point of making full use of space diversity between the source and relay. Our works mainly include:1. We proposed a new single relay assisted HARQ scheme, in which, retransmission of relay is a superposition transmission. It means the source can transmit new code while the relay is retransmitting the old code. So we can make full use of space diversity brought by the source and relay.2. We proposed the idea that relay operates retransmission at a scheduled time to cope with inter symbol interference caused by superposition retransmission. Simulations show that the proposed scheme improved the system throughput obviously, especially with longer schedule time. Simulation also gives the optimal location for relay.3. Chapter 4 continues the idea of superposition retransmission and proposed a multi-relay assisted HARQ scheme with the aim of modeling a general and simple cooperative HARQ scheme. The multi-relay cooperative system focuses on the cooperation among relays and source. We also considered the protocol and timing.