Research On Wide-Band Speech Of Wireless VoIP System

VoIP(Vioce over Internet Protocol) is highly challenging and practical new technology inrecent years.The data package is sent to destination via IP network,then we can realize thereal-time communicate with each other. In the course of VoIP development,quality of voicehas been a main factor of holding back its further process.The research of high quality highlyeffective speech code technology is the foundation, also is the first choice way.The speech coding is the process of converting speech into digital bit streams foreffciently digital storage and transmission over band-limited channels.It is now widely used indigital mobile and computer-related voice communications. With the bandwidth incommunications becoming largely broadened, peopel will no longer be satisfied with just theclearness of the voice in video and audio. More information about the speaker should beprovided,like emotion and background music.That is to say,people are pursing face-to-facespeech quality. Consequently, the bandwidth of the conventional speech coding is not enoughfor providing high quality reconstructed speech, and thus the research on wideband of thespeech coding is necessary.CELP technology has had the mature algorithm in the narrow band speech coding, thebiggest merit of drawing this technolog into wideband speech coding may guarantee thevoice quality imultaneously reduce the transmission code rate, and enhance the compressionratio.In view of the traditional algorithm insufficiency, this article proposes a new CELPspeech coding method based on the autoregressive moving average predictive model.The newmethod use the model to model the short-term correlation of speeches and the gradient descentaglorithm to obtain an optimal estimation of coding parameters,and it can effectively improvethe speech quality.Then through the research on wide band speech code method, weproposes one kind wide band pronunciation code scheme based on the CELP.We designthe QMF filter to divide the wide band speech into two subbands, and code the lower bandwith CELP narrowband algorithm, and the higher band was coded using ADPCM algorithm.Finally we introduce the design of the voice transmitting software which can simulate VoIPwith LAN environment,and have a further understanding of the VoIP system structure.