Abstract：Research purposes: The voice group call service (VGCS) isused for the railway dispatching operation and its quality is essential to the dispatching operation. At present there are still some blanks inGSM -RA Interface for testing specification of VGCS protocols, and it heavily affects the project acceptance. The A Interface protocol flow is the importantmethod andmeans ofdescribing the process of voice group call service. Based on "China Railway GSM –R Co-operating Test", this paper discusses the realization process of VGCS with A interface protocol to provide the basis forworking out the test specification for the VGCS.
Research conclusions:According to the different resource distribution mode, different announcement mode and different group call end and releasemodes, the discussions and descriptions are made for the different time of setting up group call and the occupation ofdifferentGSM -R resources aswell as the detailed flowsof setting up group call, the callend and call release with A Interface protoco.l In real test, selection of which resource allocation to the corresponding equipment should be careful on the basis of consideration of network resource situation, network co-operating situation and the actual demands of railway dispatching operation.
2009, Vol. 26 
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