Research On And Implement Of VoIP Terminal

With the continuous development of network and voice compression technology,it becomes a reality to transform the voice information, which requires the high performance of real time, in the IP networks. VoIP terminal adopts the technology of IP packet exchange, improve the utilization of line and reduce the cost of the communication. At the same time, VoIP terminal can implement many kinds of Value-added business and combine with the multimedia technology. Additionally, with the rapid development of information processing and IC technology, the price of DSP which is the core component in the VoIP terminal greatly reduced. These factors all contribute the preparation of the practical VoIP terminal. Additionally, the integration of three networks is forward to the direction of IP network evolution. These all make the VoIP have the advantage in the domain of communication. This also can account for the radical reason of the wide prospect in the VoIP.In the base of analyzing the basic theory and the key technology of VoIP,and considering the presence and developing tendency,it put forward an VoIP terminal scheme based on the LAN in this paper. The core of the voice processing component is an AC48801 chip specified in the Voice processing. It is controlled through the HPI by the DS80C400.The IP phone directly connect the LAN through the 10/100 Ethernet interface of the DSTIm400 Evaluation Board. At the same time, this scheme has many peripheral components,for example,PCM codec chip, key board ringing circuit etc.Firstly, the background of VoIP technology and the research presence at home and abroad are briefly introduced. Secondly the function and the performance of the VoIP terminal are explained. And the standard which it comply to is also illustrated. Thirdly, on the basis of reading and investigating work,many system schemes are comprehensively considered,and the feature of each scheme is introduced respectively,then the final scheme is confirmed. The independent IP phone scheme is selected. As for this scheme,different kinds of solutions are considered. The advantages and disadvantages in the different kinds of solutions are compared. Comprehensively Weighing the cost, the difficulty of implementing and the performance,one VoIP terminal solution is confirmed. This project combines the voice processing component and DSTIm400 Evaluation Board (control management unit).The key chips of this project compose a specific voice processing DSP AC48801.and a MCU DS80C400.The modularization method is adopted in the hardware designing. The voice processing part is made PCB independently, and then the auxiliary functions of the IP phone (power supply, key board, ringing circuit) are implemented.In the software designing part of the VoIP terminal, on the basis of comparing several typical open source protocol stacks, the oSIP is selected to implement the SIP stack. A thorough analysis of the oSIP stack is made first. On the basis of that, the entire software structure is put forward. And then the three modules of this software (terminal control module,User Agent module and voice session/transmisson module) are all implemented respectively.Finally, the basic calling function and performance of this terminal are tested. The testing results are analyzed, and the further works and improvements are put forward.