Design And Realization Of Voice Intercom System Based On SIP Protocol

With the development of network technology, the communication industry has changed dramatically. The traditional Public Switch Telephone Network cannot satisfy the requirements of today’s flexible communication. Smartphone which has independent operating system and supported hardware powerful is gradually replacing the traditional communication equipment. Voice over Internet Protocol technology which translates the analogue signals into the digital signals and then transmits the real-time IP packages over the internet has been recognized gradually. A varity of applications on the VoIP protocol also have gained rapid development. H.232standard published by ITU Telecommunication Union Telecommunications Standardization Organization in1966is the most developed IP phone standards. In2002, Internet Engineering Task Force released Session Initiation Protocol standard. SIP has come into being soon after wards and was selected as control protocol for all IP network multimedia subsistems for the3rd-generation mobile communication technology. The objective of this thesis is to design two different client (PC and Android mobile) platforms and to enable real-time, free voice intercom over Wireless Local Area Networks.First, the thesis analyzed the SIP protocol functions, technical characteristics, the message, the user agent and also introduced the Real-time Transport Protocol which used to transmit real-time voice. Second, on the basis of the system requirements, oSIP protocol which used to establish SIP signal connection, specifically, the architecture of stack, the important data structures, and the working principle of the oSIP is discussed in detail. The communication framework and the overall functional objectives of present system are designed. Then, the various functional modules of the system were designed. The system includes user agent module, voice processing module, the voice transmission module and user management module. The detailed design and implementation of the various functional modules have been completed based on the overall design ideas. Finally, the voice intercom system was tested. The test results show that the client can complete the functions of the system well.