| GSM-R system was first advanced and applied in Europe. Ten years ago, GSM-R system has been highly recognized by Chinese Ministry of Railways. After rigorous theoretic researching and technology discussion, it was confirmed as Chinese railways dispatch communication technology system. It would provide credible communication for speech service, data service, trains controlling service of Chinese railways. Now it has been successfully used in Qingzang line, Daqin line and so on, and it will be a modern commanding and dispatching communication system covering the trunk line of railways in China in the future.IOT(Inter Operability Tests) tests are the precondition of achieving large-scale network building. In China, we use many manufacturers' equipments to build the GSM-R network. So we need to do the IOT tests of A, C/D/G, E, Gb, Gr, Gn interfaces and test basic GSM functionality, VGCS, VBS, eMLPP and interface robustness. By finishing all the works above, the GSM-R network will meet the requirement of railways communication about security and reliability. IOT tests always contain lab tests and field tests, while lab tests are the main part.According to the results of the first step of lab IOT tests, this dissertation analyses the problems about service pre-emption discovered in the A interface test of China railways GSM-R IOT tests and presents optimization solutions on call priority, call setup message flow and timer setting of higher priority calls on A interface under one MSC, new resource releasing mechanism of lower priority calls. Then call setup establish information flow, resource utilizing ratio, call delay characteristic, call success ratio, complexity of the new optimization solutions are analyzed. Thirdly it discusses abnormal cases in service pre-emption A interface test of China railway GSM-R IOT tests under dynamic environment. Finally, a new design solution about A interface IOT tests specification on service pre-emption under two MSCs is proposed. |
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