Design And Realization Of VOIP Phone Terminal Based On ARM9

Computer science and network technology are developing rapidly in recent years, information network based on the multimedia communication has become the direction of intending information industry. The advancement of audio compression technologies and real-time transport control technology makes it not difficult to transmit audio data in IP network any longer. IP phone has successfully entered into the telecommunication area. VOIP (Voice over IP is the IP telephone), is one kind of technology of voice correspondence between the computer and the computer, the ordinary telephone and the ordinary telephone, or the computer and the ordinary telephone by using IP(Internet Protocol) as network layer protocol and Internet as transmission carrier. The basic principle as follows. First, it compress and codes the pronunciation data through the pronunciation compression algorithm. Then it packs these pronunciation data according to the standard network package, and sends these data packets to the receive place through the IP network. After that, it strings together these pronunciation data packets, after decoding and decompression processing, these packets become the original pronunciation signal, thus achieved the aim of transmitting the pronunciation by Internet.Relative to traditional telephone, the most advantage of VOIP is to make use of the Internet resources more sufficiently, and to provide much more higher quality service. In recent years, VOIP has developed from software product to multi-function terminal, and standards of it emerge in endlessly. The signaling technology guarantee the telephone calling realized smoothly and the voice quality, at present the VOIP control signaling system which widely accepted are ITU-T's H.323 series and IETF's SIP (Session Initiation Protocol). Comparing to H.323 protocol, SIP has the advantage of easy implementation, high flexibility, scalability and mobility. And it is taken into use by more and more equipment provider.This article introduces the design and realization process of IP telephone terminal, which takes the AT91RM9200 microprocessor as core and based on SIP protocol. The article first introduces the essential technology and protocol of VOIP. Then, it introduces the basic knowledge of embedded system, ARM microprocessor and embedded operation system, and constructs the embedded Linux development software platform. After that, it describes the design process of embedded VOIP telephone terminal based on the ARM9 platform, which including every hardware module's design principle and circuit schematic diagram, as well as the main module's detailed realization process. Finally, it points out the insufficiency of this article and the aspects which need to improve.(1) Introduced the essential technology and protocol of VOIP, especially to the application layer control protocol——SIP.(2) Introduced the design principles of all hardware modules, and gived all circuit schematic diagrams.(3) Introduced the hardware and software realization process of voice signal's sampling and playing module and network transmitting module.