The Research On Error Control Technologies Of Multi-Hop Relay Network

The most significant characteristic of the future mobile communication is high speed data transmission, for example, the 4G mobile communication system promise to provide 1 Gbps data rate for the low speed users, and also 100Mbps for the high speed users. Meanwhile, the future mobile communication has to work at high frequence. However, the high speed data transmission and high frequence will lead to small cell coverage. The multi-hop relay technology is a promising option to solve this problem, which can achieve coverage extension and throughput enhancement. Unfortunately, introducing relays makes the interference in the cell more complicated, so we need more appropriate error control technologies for the multi-hop realy network to essure reliability.Paper reviews the various existing ARQ and HARQ techniques and their advantages and disadvantages.The existing error control techniques of multi-hop relay network are summarized and analyzed. According to the degree of involvement in the retransmission on the entire link of the relay station, the multi-hop relay error control technologies can be classified as end-to-end ARQ, hop-by-hop ARQ, relay ARQ, end-to-end HARQ and hop-by-hop HARQ. A detailed description of their operation mechanism and a comparative analysis of their performance characteristics are provided.When both ARQ and HARQ employed on a single connection, some issues especially the end-to-end latency due to multi-hop transmission need to be considered. In this paper, an ARQ and HARQ interaction mechanism is proposed. In this mechanism, messages obtained from the lower HARQ entity in the transmitter are used to dynamically adjust the ARQ_RETRY_TIMEOUT value in order to trigger the ARQ retransmission immediately without waiting for the ARQ NAK from the peer ARQ entity at the receiver, and ensure HARQ retransmission operation of an ARQ block to be completed before ARQ retransmission of the block occurs. The results of the analysis and simulation show that this mechanism improves the delay performance and avoids the wasting of radio resources. In this paper, a flexible and based-on real communication environment multi-hop relay realtime testbed is desigened and implemented. We employ the totally open source Hydra platform based on GNU Radio to implemtent the BS, RS and MS and emulate the real channel condition by Electrobit PropsimTM C8. The testbed can be used to but not limited to error control technologies researches and will be a promising option for the research and test of multi-hop relay technologies. The investigations of the perfonnance of all kinds of error control technologies in multi-hop relay system on the testbed validate our analysis and simulations.