Study On Frequency Offset Estimation Of In-train Repeaters For High-speed Railway

Nowadays, the construction of high-speed railway has obtained a rapid growth inchina. With the number of inter-city railway increases, there is a trend that an increasingnumber of people would like to choose high-speed railway for travelling. However,because of the mobile signals deteriorate with the speed of the train increases, traditionalmobile communication network can no longer support the communication in thehigh-speed railway environment. As a result, a new challenge of the networkinfrastructure has been brought to the operators.This thesis analyses the research status of high-speed railway communicationcoverage and the solutions of major equipment vendors at home and abroad in the firstplace, and then studies the propagation characteristics of the channel in high-speed railenvironment, and also analyzes the penetration loss, Doppler shift, fast switching channel,rapid fading, etc. Solution of in-train repeater with automatic frequency control (AFC)module is proposed in this thesis to improve the quality of the mobile signal coverage.This thesis focuses on frequency offset estimation algorithm and implementation.First of all, frequency offset estimation algorithm is theoretically deduced and thensimulated based on maximum likelihood estimation algorithm. Frequency offsetestimation algorithm is then applied to the AFC module. Finally, the in-train repeater withAFC module is simulated and tested. The final result shows that the in-train repeater withAFC module can improve the quality of voice and data communication significantly.Therefore, installing repeaters with AFC module in the train is a feasible solution forhigh-speed railway communication.