【作者】 王华颖；

【导师】 侯春萍；

【作者基本信息】 天津大学 ， 通信与信息系统， 2005， 硕士

【摘要】 无线通信是未来信息和网络技术发展的必然趋势。由于摆脱了有线连接的束缚,无线局域网具有移动性好、成本低和不会出现线缆故障等特点。随着无线网络技术优势的逐渐显现和消费类电子产品的日益升温,“Wi-Fi”设备制造商在家庭无线网络市场展开了激烈的竞争。WLAN技术在家庭中的应用将主要集中在各种家庭娱乐产品的无线影音传输上。会话发起协议SIP是互联网工程任务组(IETF)提出的一个在IP网络中建立会话的信令协议,它和现有的IETF的其他协议协同工作,可以实现不同计算机、电话、电视和软件之间的通信。本文在对SIP协议进行深入研究的基础上,分析了在SIP用户代理(UA)之间建立多媒体会话的实现方法,并重点研究了在网络拥塞的情况下,SIP消息的重传机制,提出了实现200ok应答信号及其ACK重传的方法。并通过实际的程序运行,证明了所提出的200ok应答信号及其ACK的重传机制符合SIP协议的规定,从而验证了程序和方法的正确性。此外,本文还探讨了SIP协议以及SIP用户代理应用向uClinux系统移植的具体实现方法。在SIP用户代理之间建立多媒体会话的实现基于开源的SIP协议栈。在比较了几种具有代表性的开源SIP协议栈功能的基础上,本文根据项目的要求选用了合适的协议栈,并将选定的协议栈和应用程序一起移植到了采用uClinux操作系统的Motorola公司M5249C3开发平台上,较完整地实现了SIP用户代理之间的会话建立和终止过程。更多还原

【Abstract】 Wireless communication is the consequential tendency of future informationtechnology and network technology. WLAN features mobility, low cost and freedomof wire line failure because of no limit of wire line entity. With the gradual emergenceof WLAN advantages and the increasing attention to consumer electronic products,Wi-Fi manufacturers have taken up rigorous competition in the market of HomeWLAN. The household application of WLAN technology will mainly focus onwireless audio-visual transmission of various household amusement products.Session Initiation Protocol (SIP) is a signaling protocol for creating sessions in IPnetwork and is a specification sponsored by Internet Engineering Task Force (IETF).SIP interoperates with a number of other IETF protocols and enables disparatecomputers, phones, televisions and software to communicate.Based on the in-depth study and analysis of the SIP protocol, this paper proposesa practical way to realize the creation of multimedia sessions between SIP UserAgents (UAs). Much effort also focuses on the research of retransmission mechanismof SIP messages in case of network jam. Then a method is brought forward toimplement the retransmission of 200ok response and ACK for it. The resultsgenerated by the program prove that the implementation of the retransmission of200ok response and ACK for it satisfies the retransmission mechanism stipulated bySIP and also validates the correctness of the method and the program. What’s more,this paper makes some explorations into the realization of porting SIP protocol andSIP UA application to uClinux system.Implementation of creating multimedia sessions between SIP UAs is based onOpen Source SIP protocol stacks. After comparing and evaluating functions of severalrepresentative open source SIP protocol stacks, we chose an appropriate one which isin accord with the requirements of our task. Then we port the stack and theapplication program to the uClinux system of Motorola M5249C3 platform andrealize a whole process of the session creation and termination between SIP UAs.更多还原