Quantitative Analysis And Research On Electromagnetic Susceptibility Of The Digital Wireless Communication Systems

Nowadays, the digital wireless communication systems play a crucial role in railways. DMR (Digital Mobile Radio) has been applied to the railway shunting system. In addition, International Union of Railways (UIC) has proposed the evolution of the railway control system from GSM-R to a broadband communication system based on LTE (LTE-R). However, the digital wireless communication systems are susceptible to electromagnetic interference, which may lead to a decrease in the wireless transmission quality, thus affecting the communication of railway. Therefore, quantitative analysis on the electromagnetic susceptibility of the digital wireless communication systems in high speed railway is of great significance.Firstly, the thesis discusses the property of TD-LTE and DMR, then analyzes the potential interference sources for them. Based on the performance indicators of receiver, the thesis comes up with the modeling approach of quantitative analysis. Taking the Exponent Effective SINR Mapping (EESM) algorithm into account, the thesis discusses the quantitative algorithm of electromagnetic susceptibility based on the selectivity and sensitivity of receiver. The thesis establishes the BER quantitative evaluation model based on the sensitivity and selectivity of receiver, realizing the quantitative analysis of electromagnetic susceptibility.Secondly, the link simulation model and electromagnetic simulation model of DMR and TD-LTE has been established. The simulation result shows that the electromagnetic interference which comes into the band will result in the BER degradation of system. By verifying the algorithm with link simulation model, the thesis finds out that the algorithm can make accurate assessment quantitatively of the degradation of BER, realizing the quantitative analysis of the electromagnetic susceptibility. The simulation result is in accordance with the theoretical analysis.Finally, taking DMR as an example, the thesis verifies the algorithm with the digital wireless communication test platform for DMR. The theoretical data is about11.75dB, and the experimental data is about13-14dB. What makes a gap between the experimental data and theoretical data may be the experimental error such as non-ideal properties of receiver and the bandwidth of the Gaussian noise. The small variance and a gap in the acceptable range, indicating that this algorithm has certain feasibility and accuracy, and can be applied to the analysis of field test.