The Fast Handoff Algorithm Of Broadband Wireless Communications For High Speed Train

With the development of passenger special line, the mobile communication system for railway cannot meet the needs of data transport, especial in reliability, real-time and bandwidth. Because of the poor wireless communication environment in high speed moving scenario, there are several problems existing like signal attenuation, doppler shift and fast handoff which is outstanding. In order to address these problems, the main work is introduced as follows:Firstly, to combat the question of network's coverage and capacity, a structure of wireless broadband access private network based on ROF technology is designed. Dense RAUs are laid down along the railway to slightly downsize cells and to transmit radio-frequency signal through fiber. Therefore, the communication system enables to transmit high radio-frequency signal by lower power so as to promote the transmission capacity of the network.Secondly, an optical handoff method based on moved cell is proposed to solve the frequent handoff caused by downsized cells and fast moving. The traditional handoff action was based on the data link layer and the network layer, while in this paper it has been moved to optical layer to reduce handoff latency. When it comes to handoff management, complicated signalling are replaced by simple handoff and rectification signalling. At the same time of reducing the cost of network management and improving the utilization of network, it effectively tackles the question of time delay which is produced by fast moving.Mobility handoff algorithm comes next. A mobile position technology with special position system based on Gauss-Markov prediction algorithm and simultaneous prediction method is realized. Because of simple calculation and less iterations, it is suitable for the speed prediction of fast moving train.Finally, network modeler software OPNET is used to establish optical handoff scenario based on ROF and moved cell, including the Gauss-Markov prediction algorithm and simultaneous prediction method. The experimental results demonstrate that the method can provide bandwidth service with QoS for high speed moving train, and handoff performance is superior in latency and packet loss.