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In recent years, VoIP technology is developing rapidly. As the combination of IP technology and voice processing technology, it shows powerful vitality, and has become the focus of people’s concern. On the one hand, it has economic advantage of consuming less network resource. On the other hand, it’s a technology which can absorb new technology easily. It fits for the trend of combining voice network and data network together. In view of these advantages above, we combine VoIP technology and emergency communication application together, research on VoIP based emergency communication system, aiming at developing a emergency wireless broadband terminal system that keep in line with the current domestic and international development direction of emergency communication technology, the system developed should have the transfer function of short messages, documents and voice.The key technology for the VoIP based emergency wireless broadband terminal system is analyzed in the first part of the paper, including the research and comparison of VoIP mainstream signaling standards H.323 and SIP, and the research of the key technology of IP telephony. And then, the overall structure of the emergency wireless broadband system is designed, with practical application as the background, the overall system is divided into two parts named the control center and the system terminal, the structure and function of different parts of the system is carried out in detail. And the third,the communication protocol is analyzed and designed, we make predigestions to H.323’s system structure, use SIP’s text-based signaling frame, and draw on H.323 and SIP’s media control mechanisms, design the configuration of the communication protocol and communication process in particular. The analysis and implementation of system’s software is achieved in the end, we make analysis to different modules of the software first, and then develop the software by Visual C++ 6.0, achieve the transfer functions of short message, documents and audio data. At the same time, to improve the quality of voice communication, we do tests on audio data transmission based on UDP, and then, give solutions to those problems discovered in these experiments. With the widely applied of VoIP technology as the background, combines today’s society needs of digital emergency communications system, this paper realized a VoIP based emergency wireless broadband terminal system, achieved the requirements of the task through LAN testing, and has great theoretical and practical significance for further more researches on related fields.
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