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Digital trunked systems provide secure, reliable and high-speed voice and data communications, and are being developed rapidly in the whole world. So it is significant to develop digital trunked systems with independent intellectual property rights of our country.Circuit Mode Control Entity protocol stack in digital trunked switch takes charge in the function of call setup, call maintainance, call disconnection, transmission of short messages and supplement services. The basic services of individual call and group call in digital trunked switch are implemented by the protocol control module and call control module of Circuit Mode Control Entity protocol stack. Therefore, Circuit Mode Control Entity protocol stack is the key of the research and development in digital trunked switch.First of all, the developing situation of digital trunked switch at home and abroad is summarized in this paper, and based on analyzing the protocol stack of digital trunked mobile communication system, the structure and services offered by Circuit Mode Control Entity protocol stack in digital trunked switch are further researched. Then, individual call set-up scenario using on/off hook signaling, individual call set-up scenario using direct set-up signaling, group call set-up phase, request-to-transmit phase, end of transmission phase, mobile request-to-disconnect phase and switch request-to-disconnect phase in individual call and group call service of digital trunked switch are in details described, and the static design is implemented for the architecture and interface of Circuit Mode Control Entity protocol stack in digital trunked switch, and the dynamic design is implemented for the protocol control module and call control module. Next, the individual call set-up procedure, group call set-up procedure, call maintenance procedure, mobile call disconnection procedure and switch call.disconnection procedure in the individual call and group call function of digital trunked switch are implemented by using Telelogic Tau G2software and by programming of UML and C languages. At last, the protocol consistent tests are implemented for the program of individual call set-up procedure, group call set-up procedure, call maintenance procedure and call disconnection procedure, and the results satisfy the design requirements.
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