| In order to meet the requirements of high reliability of railway communication and high quality of passenger communication; faced to the problems of wireless coverage, co-channel interference, path loss, and Doppler shift; this paper propose the idea of overcoming communication difficulties by the application of wireless relay. It theoretically analyzes the applicability of wireless relay in high speed railway environment. Based on common model used in high speed railway field work, this paper analyzes interference from both large scale and small scale to amplify-forward relay mode. With the simulation and Calculation, the paper propose reasonable scheme about network planning according to the standard of China Ministry of Railway. It is when both BTS and repeater transmit signal by antennas, the distance between BTS and its adjacent repeater must be≤2.19km, in single layer cross redundancy coverage it should be≤1.68km. When two adjacent repeaters with antennas are same frequency, D should be≤2.40km, in single layer cross redundancy coverage it should be≤2.07km. It also demonstrates that in tunnel's entrance if the distance between adjacent repeaters≤1.85km, any position can fulfill the demand, in single layer cross redundancy coverage it should be≤1.80km. For decode-forward relay mode, this paper considers the models that relay is fixed on a vehicle; and propose working process about mobile relay node. And then, it innovative bases on WINNERⅡchannel model to make semi-physical simulation about indicators of communication in the speed of 360km/h. The results are the average call setup time is 11.8s, call setup success rate is 97.90%, transmitting interference FER is 7.66*10-3%, approximately 99% of receiving quality of downlink is level four or above. It proves the application advantage of wireless mobile relay in high speed movement environment, and the theory basis for its application in future. |
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