Research And Implementation Of Voice Distribution Function In TETRA Digital Trunked System

TETRA digital trunked communication system is a kind of private mobile communication system which is mainly used in police department, transportation and electricity sectors. The functions such as channel assignment, voice port assignment and voice bearer are achieved in voice distribution module, which is an important part of voice service in TETRA digital trunked system. Therefore, the research and development of the voice distribution function is one of the key technologies in TETRA digital trunked development.First of all, the development situation of voice distribution in domestic and foreign communication systems is summarized in this paper. Based on analysing the structure of TETRA digital trunked system and the function of voice distribution module, signaling procedures of individual call in same voice mode, individual call in different voice mode, group call in same voice mode and group call in different voice mode are detailed described. Then, the structure of voice distribution module, the MA interface between MGC module and mobile link entity(MLE), the MB interface between MGC module and MG module, the MC interface between MG module and base station(BS), SIP gateway or dispatcher server are designed, the channel allocation signaling, the channel release signaling, the fields of circuit mode, packet data service mode and teminal service message are defined, and the processing procedure of MGC receiving signal from MLE, MGC receiving signal from MG, MG receiving signal from MGC, and MG receiving signal from BS, SIP gateway or dispatcher server are designed. Next, the main program of voice distribution module, the MGC module and the MG module are developed by using C programming language in the Linux operation system, the voice distribution functions such as channel assignment, voice port assignment and voice bearer are achieved in individual call and group call services. Finally, the procedures of individual call in same voice mode, individual call in different voice mode, group call in same voice mode and group call in different voice mode are tested, the test results show that the voice distribution function of TETRA digital trunked system is implemented by voice distribution module, and the results satisfy the design requirements.