Research Of The Influence On GPRS By Communication Blind Area Of GSM-R

The GSM-R communication technology is a dispatching communication system designed specially for the railway. It's based on the GSM cellular communication system, which adds the elements of train dispatching function and fits for high speed environment. How to apply GPRS into the GSM-R network nowadays is a hot problem in the field of railway communication. Meanwhile, the application on the railway focuses on the following problems: how to ensure that the packet data can be transmitted in a safe and reliable way on the railway; and how great the blind area will influence the performance of GPRS in GSM-R network.First of all, the thesis introduced the application of the packet data service in the GSM-R network and the solution of transmission. Then the mobility management and the session management of the GPRS MS are analyzed, as well as the related timer involved. Secondly, based on the the laboratory of GPRS network, the various situations of MS entering to the blind area and backing to the coverage was simulated. With the signal message in the Gb interface, the theoretical time was got for detecting the doff from network, when MS enters to the blind area and the time for recovering the transmit of data when MS come backs to the coverage.After the comparison between the theoretical values and the actual values, the time about MS being in the blind area, cell reselection, and route updating can be calculated. Thus, the longest interrupt time of the data transmission can be figured. Analyzing the reasons for the set of scheduling command interval and considering the time that blind area can caused, the thesis discusses the unreasonable fact of the interval during data retransmission and brings up a solution to improve it. And then, by using the relevant data of Qinghai-Tibet line, the thesis analyses the feasibility and rationality of this improved solution. The solution can make good utilization of the GPRS channel resources, which ensures the safe and in credible transmission of message.