Research On Robust Voice Transmission Over The Internet

Following the fast growth of the Internet in recent years, the research of the real time voice transmission over the Internet has been popularized very much. But because the Internet nowadays based on Ipv4 only provides a best effort service, and no QoS guarantees provided, the network congestion and delay will result in dramatically decrease of perceived voice quality.In this thesis, we research the problems on the robust voice transmission over the Internet in the application level based on existing network condition. The main contributions of this thesis are as follows:1) A series of Internet traffic experiments are presented to reveal the behavior of packet voice over the Internet. The results are analyzed and the factors influencing the perceived voice quality are discussed in details, such as bit errors, packet losses, packet delay, delay jitter and so on. Understanding the loss and delay behavior of Internet traffic is essential in designing an efficient robust voice transmission scheme.2) A new index assignment technique is proposed to reduce the impact of the bit errors to the perceived voice quality. The new technique resolves the index assignment problem by means of codebook construction. Experimental results show that it can get superior performance in large codebook than the classic binary switch algorithm based on simulated annealing technique.3) A packet loss recovery technique based on parity-based piggybacked forward error correction technique is proposed. It can recover consecutive packet losses caused by network congestion efficiently. Moreover, a new method for recover packet losses using (2,1,m) convolutional codes is proposed. Compare to classic packet loss recovery...