Mobile Network Coverage&Optimize Scheme Of High-speed Railway

This thesis discusses several main issues on mobile network coverage&optimization scheme of high-speed railway, it includes: chief problems&solutions which will encountered in high speed environment, factors must beconcerned in network plan&design, network optimization principle&method, etc. An example of WCDMA network optimization along shanghaisection of Beijing-Shanghai High-Speed Railway is given in the end.Doppler shift and handover are two factors which will conspicuouslydecrease communication quality. Doppler shift causes code error at receiverand destroys the orthogonality between OFDM sub-carriers, which bringsinter-carrier interference. Technologies such as double lock loop coherentdemodulation, differential coherent receiver, diversity reception can eliminatethe impact of Doppler shift. Call often drops while train’s speed is too high,because there is no enough time to finish handover between adjacent cells. Inengineering, increasing the coverage overlap distance between adjacent cellsand optimizing system’s handover parameters should be adopted to solve theproblem.Link budget and networking scheme are the two key issues which shouldbe considered in high-speed railway mobile network planning. Businessmodel and uplink budget are listed according to model selection andcalculation principle when planning a WCDMA network along high-speedrailway. After comparing the advantages and disadvantages of public andprivate network, networking scheme and coverage strategy are proposed.After a series of optimization scheme (e.g. dual carrier&differentfrequency coverage) be implemented, the project of WCDMA networkoptimization along shanghai section of Beijing-Shanghai High-Speed Railwayachieve a complete success. Most of the network performance indexesimprove significantly.