Research Of WSOLA Algorithm In VoIP Based On Wireless Networks

With the rapid development of wireless networks, various of applications based on wireless networks go into our eye. Because of its huge advantages compared to traditional telephones, realtime voice communications on the IP networks got a rapid development too. Because the wireless networks are not as stable as the wired ones, realtime voice communications are facing a lot of challenges, including packet loss and delay. And because the realtime voice communications requires a low delay, traditional ways of dealing with the instability of wireless networks, such as retransmition, seems to be unreliable. Other than various FEC codes, many kind of packet loss concealment techniques are applied to deal with the instability of wireless networks in the realtime voice communications. Because its feature of maitaining the pitch frequency and timbre, Waveform Similarity OverLap and Add(WSOLA) algorithm can always get a good result in the packet loss concealment procedure. Unfortunately, the WSOLA algorithm is lack of efficient amplitude controls, and can not get best results in some circumstances.In order to solve the problem above, this paper improved the standard WSOLA algorithm by introducing an amplitude gain into it. By this way, the standard WSOLA algorithm gets a powerful ability of amplitude control, and is able to get better results in the packet loss concealment procedure.In this paper, the work done is mainly in the following aspects:First, analyse the ways of dealing with the high packet loss rate in realtime voice communications based on wireless networks.Second, do some research in the standard WSOLA algorithm, and get an analysis on its performance. Third, introduce a gain into the standard WSOLA algorithm, in order to improve its ability of amplitude control.Fourth, do the simulations by programming, compare the standard WSOLA algorithm with the improved one, and get the conclusion.