| Through constant development and innovation,high-speed railway in China has become the world's most extensively used and longest high-speed rail network,along with the most sets of rolling stock,and some of them are designed for.the highest commercial operation speed.The increase of the passenger and goods traffic,as well as the speed of commercial service has brought great challenges to China Train Control System(CTCS),since more and more essential information is transferred through radiocommunication systems between train and trackside,such as train control,voice dispatching,command,operational information as well as the monitoring data.However,the electromagnetic environment of high-speed train is quite complex,where weak-current and strong-current devices survive together.Under such circumstance,radio transmission link of CTCS-3 is prone to surrounding electromagnetic disturbances,thus it has been a major threat to RSTT,and may result in critical security issues for railway transportation and even passengers.Therefore,to guarantee the safety of train operation,the interference effect of radio transmission link in CTCS-3 has become a critical issue to the information transmission between on-board radio equipment and the related radio infrastructure located along the tracksideDuring the train operations,the electromagnetic disturbance in the environment is quite stochastic and bursty.In the meantime,numerous radiocommunication technologies have been used for railway operational applications and various modulation and coding schemes have been adopted.Thus the quantitative relationship is difficult to be established between electromagnetic disturbance and the performance of the wireless link.In order to ensure the performance of wireless communication links in the complex application scenario like high-speed rail,it is necessary to evaluate the interference effects of wireless communication links using different modulation and coding schemes under pulse disturbances,so as to propose appropriate anti-interference methods to reduce the impact of pulsed disturbances.In this thesis,considering the main disturbance sources in the high-speed rail environment affecting the wireless link of the CTCS-3 train control system,a statistical parameter model of pulsed electromagnetic disturbances is established by analyzing the time-domain statistical characteristics of typical pulsed electromagnetic disturbance signals.Then,the instantaneous effect is achieved through the statistical parameters of the disturbance,as well as the long-time equivalent,thus the the quantitative relationship is established between electromagnetic disturbance and the error performance of the data link(including different modulation and coding schemes).Moreover,in view of the burst of pulsed disturbance,from the perspective of improving the immunity of sensitive equipment,methods to disperse short-term performance degradation is proposed to solve the electromagnetic compatibility problem of the wireless link of the CTCS-3 level train control system.Finally,a multi-statistical parameter synchronous measurement system based on a virtual instrument platform was built,to achieve accurate measurement of the statistical parameters of electromagnetic disturbance in the presence of useful signals,and the effectiveness of the evaluation method of wireless link interference effect is verified through the platform.The main innovations of this thesis are as follows:(1)In order to study the interference effect of wireless links using different modulation methods,the quantitative relationship is established between the upper bound of the error performance of wireless link using different modulation shemes and the statistical parameters of electromagnetic interference signal,through the bit-level interference effect evaluation model of the modulated signal based on the interference statistical parameters.Since it provides an upper bound of performance criteria,it can offer a theoretical reference of the limit to the radiation emission.(2)In order to study the interference effect of wireless links using different coding methods,through effective signal-to-noise ratio mapping algorithm,the relation between the error performance of radio transmission with channel coding scheme and the joint statistical parameters of electromagnetic interference is established.It provides the theoretical reference to coding performance of radio link under time-varying disturbance,and it is more flexible and accurate than the numerical simulation method.(3)In order to solve the electromagnetic compatibility problem of wireless information transmission caused by pulsed disturbance in the high-speed rail environment,according to the electromagnetic interference troubleshooting principles and general methods of the high-speed rail signal system,from the perspective of improving the anti-interference performance of sensitive equipment,The methods are proposed of discretization the burst interference effect from time domain,frequency domain and space domain respectively,they can be used to improve the interference immunity of the radio link of the CTCS-3 train control system and ensure the reliability of train control information transmission.The research on the wireless link interference effects establishes the relationship between the error performance of wireless transmission and the statistical characteristics of disturbance,so as to provide a theoretical basis for standardizing the emission limit of statistical parameters of electromagnetic disturbance.At the same time,because the evaluation method in this article is suitable for complex scenarios where various harassment coexists,and does not require prior information about disturbance,it is suitable for practical applications in high-speed rail environments,such as real-time supervising,risk analysis and early warning in the future. |
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