Research On Data Transmission Technology Based On Voice Channel Of Mobile Public Networks

Nowadays,the voice channel has been widely applied with the rapid development and the expansion of wireless mobile communication network.Although the high speed of data communication has been developed and utilized,the data communication which is transformed in the compressed voice channel still has a broad appeal.The reason is that the voice channel can improve the service quality better than the data channel.Besides,it will lead to the bandwidth declining and also make the transmission bandwidth and delay of data channel produce unpredictable changes along with the increase of current mobile voice services and the priority of voice channel in the gateway crowed.At present,there are three methods which are conventional modulation,speech-like synthesis and data waveform mapping for the transmission of data based on the voice channel.The method of data waveform mapping is the hotspot of current research.In this paper,several techniques which aim at the shortcomings of the existing systems are proposed to solve the problem of optimizing the code,the applicability of vocoder and the problem of synchronization.The main work and innovations are as follows:For the problems that the demodulation precision is improved and the simulation cycle of optimizing code is shortened,a method of speech-like modulation based on Genetic Algorithm(GA)is proposed.This method adopts the data waveform mapping which will let predefined waveforms replace the modulated data to join together into speech-like.The design of waveforms and the update of codes both use GA.The proposed method compared with existing methods can improve the speed of simulation and the accuracy of demodulation for the system.Experimental results show that the symbol waveforms generated by the proposed method have better performance and lower complexity of generation process than the methods of conventional modulation and speech-like synthesis.To find an algorithm of speech-like modulation which can generate some waveforms transmitted in multiple types of vocoder,the method of speech-like modulation based on corpus is proposed.First of all,it deals with the corpus to get the search space through the relevant pretreatment and uses incremental search algorithm to optimize it to generate optimal code.Besides,the optimal code is further improved so that it is better to fight voice activity detector(VAD).Experimental results show that the proposed method can make the symbol error rate(SER)can get 0% in the rate of 12.2kbps of AMR when the number of symbols is 16.In the same way,the SER of EFR vocoder and FR vocoder both can get 0%.For the problem of synchronization in actual system,this paper designs a synchronous sequences signal by using external synchronization method.The autocorrelation of this signal is good.Meanwhile,it can automatically detect the alignment marks and transmit through the lossy compression of vocoder.Experimental results show that the signal designed by the method presented in this paper can be detected at the receiving terminal and also can be jointed with the speech-like which will not produce mutual influence causing no transmission.