Research And Implementation Of Embedded VoIP's Key Technology

The fast development of VoIP applications and embedded system exploitation technology has already made implementation of VoIP on embedded system become the developing trend of VoIP product. This article is based on the"FreePP"project being carried out in Shanghai Gemtek-Systems Corporation. The main task of the project is to design and implement the PPBox, which is an update VoIP user terminal product using the smartest techniques. In this article, firstly the embedded exploitation platform of PPBox is analyzed, and then the PPBox's architecture is implemented in this exploitation platform. What is more, several key functional modules'design and programming are completed, including call-state controller module, UTD detection module, subscriber's ring controller module, FXO line-state module and so on. Finally, the PPBox voice coding technology is analyzed in detail as well as some relevant problems that will influence the quality of voice. Also, the NAT-crossing theory and technology are deeply researched. Through effective improvement of PPBox NAT-crossing methods, some quite satisfactory performance is retained.The research and manufacture of PPBox involves vast technological fields and kinds of software and hardware exploitation platforms, which is therefore quite complicated. The research work completed in this article will fully advance the practical application of PPBox. At present PPBox has passed product experiment and entered commercial operation in FreePP network.