Design Of A Kind Of Inaudible Acoustic Communication Method And Its Testing On Android Platform

With the rapid population of intelligent terminal,the demand for information acquisition and sharing at short distance is more and more strong.Thus,there are more and more requirements on near field wireless communication technology.Among all kinds of near field wireless communication technologies,acoustic wireless communication is the most potential one and deserves further research because it is easy to use and it has the minimum hardware requirements and the widest application scope.In this thesis,we combine digital communication theory with software development technology and introduce a new kind of near field wireless communication system which is based on acoustic transmission.This system can overcome the deficiency of traditional acoustic wireless communication system which is based on frequency identify technology.The frequency of sound wave adopted in this system is pretty high so human beings are difficult to detect it.Therefore,this system can also be named inaudible acoustic communication system.Firstly,in this thesis we start with the background,research significance and research progress at home and abroad of acoustic communication and generally introduce the way of information transmission by sound wave.This can help to point out the necessity of further study of applying it in air channel and implementation on Android platform.Secondly,in this thesis we analyze the requirements of inaudible communication system from three aspects namely the appropriate application scenario,functions to be realized and goals to be achieved.Then,we make the overall design of this system referring to the general model of digital communication system and the architecture of Android platform.This can help to make the basic framework and parameters of this system clear.Then,in this thesis we measure the acoustic channel and get the power delay profile.We get the static result of fading and the most time delay of multipath from the power delay profile.According to the measured result,we simulate the key algorithms in this system on Matlab platform including synchronization,channel coding and equalization.The simulation results are the basis of algorithm selection.Next,in this thesis we make the detail design from four aspects namely communication system model,transmitter,receiver and design patterns.Then we introduce the implementation of key algorithms on Android platform using the flow diagram referring to the basic theory.Finally,in this thesis we test and validate this system from two aspects namely function and availability according to the demand analysis.Compared with traditional acoustic wireless communication system,the system designed and realized in this thesis has more functions and performance is better.Ears are hard to detect the sound wave and this system supports functions of parameters configuration and signal spectrum display.The transmission efficiency is improved significantly and it can transmit 122 English characters or 61 Chinese characters in one frame.The transmission distance is improved significantly and the receive accuracy of this system must be greater than 98% for excellent user experience.In half duplex mode,the transmitter has an external speaker and the most transmission distance is 5m.In simplex mode,Android terminal is the transmitter and the most transmission distance is 20 cm.