Design And Implementation Of Embedded Communication Terminal Software Based On SIP Protocol

With the development of network technology, a variety of means of communication has emerged. However every single means of communication can not meet all requirements of users, so users will often use a variety of means of communication. But use a variety of means of communication at the same time can bring a great deal of inconvenience and inefficiencies to customers. In order to solve the above problem, the subject efforts to design a terminal equipment that can provide audio, video and data communications and have both wire line and wireless transmission systems.The core technology of this terminal communications equipment is IP Video Phone based on SIP protocol. This paper describes the software design and implementation of IP Video Phone base on SIP.Firstly, this paper outlines the development trend and some key technologies about IP telephony, and the research emphasis is on the SIP signaling technology, media negotiation technology and real-time transmission technology. Then the framework design of terminal considering the common system architecture is proposed, including hardware and software part. Subsequently, this paper discusses the design and realization of the SIP signaling module and the media session module which are two important modules of IP video phone software modules in detail. This paper presents two important ideas in the part of software design. In the signaling control part, a kind of user-agent structure based on the transaction state machine is designed to solve the complexity problem on the signaling control. That is achieved by analyzing the user state migration process and defining a series of process interface. In the part of audio and video communication, taking procedural structure, portability and functional expansion into account, Pipeline design idea is proposed. Pipeline can realize the audio and video communication by defining and packaging the processors of three sub modules of the media session module, then forming and running the handling link including all the processors.Finally, this paper tests the communication of this terminal equipment with other IP Telephony based on SIP, the test results show that terminal can provide right control for SIP Signal, satisfying quality for audio and video communication and good compatibility.