The Design And Implementation Of IP Phone Based On WLAN

The continuous development of information technology makes our exchange of information become increasingly easy, and has more and more ways to communicate with each other. As an Internet application, VoIP (Voice over Internet Protocol) is one of means of communication. And with the advancement of Internet technology, the improvement of VoIP technology, Internet telephony will also play an important role in the future's information communication.Internet telephony is a product of combining voice technology and Internet technology, referring to transmit voice data over the Internet. It has some key technologies include codec technology, real-time data transmission technology and signaling technology. In which the voice codec technology processes the local multimedia information, the real-time data transmission is responsible for information transmission, and the signaling is responsible for processing the user's call requisitions. The three complement each other to complete telephony applications. Together with other related technologies, these constitute the today's VoIP.In this paper, the principle of VoIP communications and key technologies are studied, and on this basis, a wireless telephone communication terminal, using in wireless network environment, is designed and implemented. It's called the wireless IP phone.Internet telephony is a relatively large and complex system, so this article studies the structure of VoIP and basic communication principles in the modern network environment. It includes the form of Internet telephony application in the Internet environment and the usage of combination with telecommunication network and Internet. At the same time, it discusses the basic communication theory of Internet telephony, a series of processing of information, from collecting information, coding and decoding voice date and packaging voice date, to transmitting packages to network. And it also studies the key technologies such as VoIP voice codec technology, real-time data transmission technology, signaling technology and WLAN (Wireless Local Area Network) technology.After the related theory, this paper then discusses the design and implementation of a terminal device, a wireless IP phone in VoIP system. In hardware, the task includes the core processor module design, voice processing module design, network transmission module design, power module and other related circuits design. In the software, the task includes transplanting voice module drive, network transmission module drive and operating system. Then, related protocols stacks of VoIP are transplanted, including SIP (Session Initiation Protocol), RTP (Real-time Transport Protocol) and so on. After transplantation has finished, a software phone used on the target platform is transplanted to achieve the IP-based wireless network telephone terminal.Finally, this paper introduces the method to build a basic VoIP system, and in this system, the wireless IP phone is tested. Through the analysis of communication data and testing of talk, the result shows that the design of wireless IP phone can complete the whole call process in accordance with the requirements of call signaling protocol, and the call quality is satisfactory. Wireless IP phone combining the advantages of wireless and IP phone has a good value.