Research On The Railway Mobile Communication System Based On OFDM-SFCN

With the rapid development of railway transport, the railway mobile communication and the information and communication technology have been put forward higher requirements by transportation production command system, the railway communication system needs to reflect communication real-time and reliability more than any other system. Railway mobile communication system should not only provide independent and specific mobile communication system for the railway department, but also meet the future communication business demand of the rail industry. At present the GSM-R communication system can meet the needs of high-speed railway communication in practice, but there are still some defects in the aspects of the system implementation complexity and handoff.Orthogonal Frequency Division Multiplexing (OFDM) technology, with characteristics of high spectrum efficiency and strong anti-interference, can be implemented in wireless channel with high data transmission speed. Single Frequency Network (SFN) is composed of a number of synchronization state radio transmitters in different locations, at the same time, launching the same signal with the same frequency, in order to achieve reliable coverage of a certain service area. The technology has been widely applied and made good effects in Digital Audio Broadcasting (DAB), digital terrestrial television broadcasting (DVB-T) and Digital Terrestrial Multimedia Broadcast (DMB-T) and other systems.In this paper, the characteristics of OFDM's anti-multipath delay and Single Frequency Network are considered, the OFDM-SCFN system is formed by OFDM combined with Single Frequency Cellular Network (SFCN), which is applied to railway mobile communication system to constitute the railway mobile communication synchronous single frequency cellular network (OFDM-SFCNR). In this paper, we do further research on the theory of OFDM-SFCNR network level, build simulation model and simulate with the OPNET software, by comparison with GSM-R, proving that OFDM-SFCNR is better than GSM-R in the handoff performance.Firstly, it analyses the domestic and international development of mobile communication and the railway communication, describes in detail the GSM-R railway digital mobile communication system and applications in domestic, and analyzes the GSM-R technical advantages and disadvantages in high-speed railway mobile environment. Secondly, it introduces the OFDM-SFCN communication, aiming at the communication interruptions in GSM-R handoff, describes the advantages of technical in detail, proposing the OFDM-SFCNR system with the OFDM-SFCN application in Railway Communication. Furthermore, it studies the theory of OFDM-SFCNR, establishes network simulation model including speech business model and movement model, and uses the OPNET software to simulate the GSM-R system and OFDM-SFCNR system. The simulation results show that the OFDM-SFCNR has technology superiority in Average Packet Lost Rate, New Blocking Rate, Call Dropping Rate and Handoff Conut, and that OFDM-SFCNR railway communication system can overcome the communication interruptions caused by handoff in GSM-R has the feasibility of practical application. Finally, it discusses radio wave propagation model based on the small-scale multi-path fading, including the forming principle and influence factors, a multi-path channel model of high-speed railway environment is established, and applied to OFDM-SFCNR simulation system which takes DAB as reference. Through MATLAB experiment, it proves the feasibility that the radio wave propagation model can be applied to OFMD-SFCNR.