Low Rate VoSat Key Technology Based On Code Excitation Linear Prediction

Due to large communication range,high stability and low deployment cost,satellite mobile communication system plays a significant role in disasters prevention,counter-terrorism and border patrol.However,because the satellite communication systems of China are mainly manufactured by the foreign counties,a lack exists in the information security and communication resource guarantee.Researching the key technology and constructing an independent satellite mobile communication network of China is highly demanded.VoSat(voice over satellite)is the basic service of satellite mobile communication network.Because of the narrow bandwidth and high interference,DP-CELP(distributed pulse code excitation linear prediction)codex is applied as the voice compression scheme of VoSat.To improve the service quality of VoSat,LOVQ(logarithmic orthoplex vector quantization)algorithm is proposed in this contribution and the independence between quantization performance and source distribution and the optimal bit allocation scheme is deduced.LOVQ is applied to improve the LSF parameter of DP-CELP codex and quantization signal-to-noice ratio of LOVQ,spectrum distortion of LSF parameters and the objective MOS(mean opinion score)of VoSat are simulated.Codex is the basic core of VoSat.In this thesis,the principle of DP-CELP is firstly introduced.LOVQ algorithm and VoSat voice quality improvement scheme are presented.Due to theoretical analysis and algorithm improvement,the quality of output voice is improved as the simulation shows.