Research and Implementation of SIP Protocol Stack and Wireless Terminal

With the development and popularization of WLAN (Wireless LAN), people prefer IP phone over WLAN for its economy, so it is necessary to research and develop WLAN IP phone terminal. SIP (Session Initiation Protocol) is capable of supporting mobility naturally. Compared with other signaling protocol, SIP is characterized by its simplicity, extendibility, flexibility, mutual operation and reusability. Because of these merits, SIP has become the preferable signaling protocol of embedded mobile terminal. This article is aimed to implement an efficient and flexible SIP protocol stack as well as to develop user agent application with the function of register and call, and ultimately to realize WLAN IP phone terminal. To achieve simplicity, flexibility and high efficiency, the SIP protocol stack is designed by using modularization model and implemented by using C language. Then, this article proposes a general design scheme and expounds respectively from hardware and software the implementation of User Agent, which is provided with register and fundamental call function