GSM-R Radio Network QoS And Its Effect On CTCS-3 System On High-Speed Railways

As a specialty of digital mobile communication system designed for railway, GSM-R can provide voice and data service for railway, and is the transmission plat roof of CTCS-3 at the same time. In order to ensure the safe operation of trains, corresponding QoS indicators of GSM-R network should meet the requirements of CTCS-3 Train Control System. But only specific requirements of the value of these indicators are given according to the worldwide research backgrounds, and there is neither theoretical analysis of these values nor complete test results on High-Speed railways. So the establish theory of all the QoS indicators of GSM-R network is studied in this paper, meanwhile, factors that impact the indicators are analyzed and optimization proposals are given too. Then all the QoS indicators are verified by setting up appropriate testing environment on the Zhengzhou-Xi'an Passenger Dedicated Railway, and all the indicators meet the requirements of specifications with high and low speed, the transmission interference with High-Speed is analyzed in-depth as well.The performance of wireless channels may be unstable and time-varying, due to signal loss in the wireless environment, complex terrain and the impact of the mechanism of GSM-R network itself. So communication interruptions caused by GSM-R network QoS are inevitable, even all the QoS indicators are in line with regulatory requirements. Therefore, the impacts of GSM-R QoS to data transmission and different scenarios in CTCS-3 System are studied in this paper. Also recommended values of the parameters about train control data transmission are given under the condition of qualified QoS, as to better meet the characteristics of GSM-R network and provide guidance for engineering practice. The parameters are: communication timeout timer (T_NVCONTACT), radio link timeout timer (RLT), and maximum number of retransmission (N2), timers T1, T2, T3, and T4 on the HDLC layer.