A Secure And Real-time Voice Transmission System: Design And Implementation

With the rapid development of network technologies, the use of multimedia data transmission system over network has become more and more popular. However,most of these systems have following limitations: Low voice quality, limited ways of data communication, unsafe transmission of data. Therefore, a total solution which can be applied to various network environments, supporting real-time transmission and guaranteeing security of data communication is in great demand. In this article we design and implement a secure and real-time voice transmission system. This system supports variety of audio (voice) compression protocols, including G.729A, G.722.1, MP3, and various ways of data communication, such as LAN, ADSL, MODEM. We use real-time transmission technologies and information security technologies to satisfy system's demand of real-time and safety.Our research work includes following aspects:1. Analyze the research background and user requirements; Clarify the functional and Non-functional requirements.2. Research on system related theory and key technologies, including audio coding technologies, real-time transmission technologies, transmission control technologies and information security technologies.3. Do preliminary design and detail design. Design voice transmission device based on embedded technology. Design central data collection platform based on C/S and B/S mixed structure. Use RTP/RTCP to realize real-time transmission of voice data over IP network. Apply jitter control, congestion control and error control to guarantee QoS of voice transmission. Encrypt voice data with SRTP/MIKEY. 4. Impletment communication server program and client program with VC++. Use JRTPLIB to realize RTP/RTCP .Use source code from Ericsson to realize SRTP and MIKEY. Implement decoding of G.722.1 and G.729A based on ITU-T's source code, and decoding of MP3 based on mpglib.5. Do functional test and performance analysis. Test and analyze system delay and voice quality in various conditions, such as different voice coding protocols, different ways of transmission and encryption.The study result of this article can be applied to fields which have special demand of real-time and safety (for example, Army, Public Security, etc). After being continually improved, this system has a wide application prospect.