Research And Implementation Of Diversity And Error Correction Technology In Shortwave Data Communication

Shortwave wireless communication technology is highly valued by many countries and has a rapid development trend due to its strong anti-destructive ability,high geographical adaptability,low operation cost,and long communication distance.However,due to the short-wave propagation through the ionosphere,multipath effects,Doppler shift and fading are prone to occur,which affects the performance of shortwave transmission.The ultimate goal of software radio is to provide a communication platform that is compatible,open,and scalable,and maximize the flexibility of the system.Software radio technology has been applied in many fields,such as China's third generation mobile communication system.The software radio idea and short-wave wireless communication are connected through the programming language to realize the organic combination of the two,and promote the development of shortwave communication technology to digital,network and broadband.This design is based on the Windows operating system,design and implement the short-wave communication system sender and receiver software.The system applies the software radio idea at the time of design,software the receiving process,modularize the modem function and the encoding and decoding function.Firstly,the modulation mode of the system is time-frequency modulation,and the error correction code is RS-Turbo concatenated code.Secondly,in the system test,the test data is obtained by performing diversity processing on the demodulated data.Finally,the simulation of the Rayleigh channel is completed using the simulation software,and the message sequence processed by the different channel parameters is output.The main work of this thesis is the realization of the transmission and reception functions of the shortwave communication system,including data protocol assembly,TFSK modulation and demodulation,error correction code compilation and decoding,and diversity test.A new communication protocol was designed for shortwave communication,and the packaging of the four-layer data format was completed.The encoding and decoding functions of the error correcting code RS-Turbo code are implemented,wherein the RS code is an outer code and the turbo code is an inner code.The principle and structure of the error code of the error correction code are analyzed and deduced in detail.A block equal gain combining method based on equal gain combining is designed to effectively improve the anti-fading performance of the system.In the whole software implementation process,two functions are designed to save and display waveform data for system debugging.Finally,the sender software and the receiver software were tested,and the test results were analyzed and compared.A large number of test results show that the software can operate normally;the error rate of the demodulated signal after diversity processing is lower than that of the non-diversity processing,and the performance of the RS-Turbo code is better than single channel code performance;The performance of the short-wave data communication system is good.