Research And Optimization Of Changsha High-speed Railway GSM Networks

In April 2007 China railway high-speed (CRH) finished the sixth speed acceleration. The speed of CRH train in Changsha has also reached 150 km/h. The great penetration loss and high speed of CRH train resulted in deterioration of GSM network quality. The signal coverage rate,call completion rate,call drop rate and voice quality of GSM network degraded substantially, and so that it could not meet the basic need of mobile communications and could not satisfy the customers. It is a tough topic faced by telecommunication operators to improve the quality of GSM netwok in the situation of CRH.This thesis analyzes the topics as below:It analyzes the essential reasons of GSM network deterioration in the situation of CRH in detail. It comes to a conclusion that the the essential reasons of this problem are that the original GSM network could not accommodate to the great penetration loss and the original cell reselection, and the handover policy can not meet with requirement of the high speed movement.It brings up a solution of the problem in three sections:coverage enhancement, sufficient capacity supply and wireless parameters optimization. Especially about coverage, it takes the theory of pathloss and propagation model tuning in practice. More important, it gives new suggestions on coverage enhancement, such as splitting the fourth cell, cell combination, using special antenna, digital fiber optic repeater applied to dedicated network. It proposes methods of voice service prediction and data service.predition. Parameter optimalization on cell-reslect and handover process is also suggested.It also gives suggestions to improve the call completion rate and the call drop rate. And then, the solutions are applied to CRH GSM network optimization of Changsha, the result of comparison between pre-optimization and after-optimiztion proves that the GSM network quality of CRH train can achieve a satisfactory level by using the methods proposed by this thesis.