Cooperation-based Type-Ⅰ Hybrid ARQ

Hybrid ARQ technology (HARQ) combined with both the merits of FEC and ARQ can make full use of retransmission and correction, also can provide the high reliability. As the relay nodes of cooperative networks, the performance of the overall networks can be strengthened a lot. In this paper, we try to introduce HARQ into the cooperative networks to increase the throughput of HARQ.According to the two retransmission protocols implemented in cooperative networks-AF and DF, this paper proposes AF cooperative strategy based on Type-I HARQ and DF cooperative way based on Type-I HARQ. In AF strategy, the relay nodes can amplify the received signals, and then forward to the destination node. When the destination node fail in error correction, source would be responsible of retransmission, and the relay nodes only take charge of amplifying and forwarding. However, in DF strategy, the relay nodes would first correct errors, then encode the message and last forward to the destination. When the relay nodes fail in error correction then source is responsible for retransmission. While the relay nodes success in decoding, the retransmission process is only related to the relay nodes.In this paper, we deduce the HARQ throughput formulas for these two cooperative strategies and compare with non-cooperative networks in throughput and bit-error rate. We further consider the positions of relay nodes and the power distribution then put forward the power distribution based on different weight. The results show that, the place of relay nodes in cooperative channel can affect the throughput largely. While the choice of power distribution is linear with AF strategy and emphasis on the first hop with DF strategy, the throughput is not sensitive to the place of relay nodes, which is useful in practical utilization. The results of data calculations and simulation results show that compared with non-cooperative HARQ, the HARQ throughputs of AF and DF are increased obviously, and so is reliability.Between the two cooperative strategies of HARQ, the performance of DF is better than that of AF, but AF requires lower complexity about relay nodes. So we should choose the mechanism based on the practical condition.