Design And Simulation Of Wireless Data Transmission System Based On DQPSK

With the deterioration of the electromagnetic environment,a wireless data transmission system of higher stability and reliability is required.A wireless data transmission system based on DQPSK/DSSS-DQPSK is researched and designed for aerospace engineering demands.Around multiple sites with high-speed relative motion,stable and reliable wireless data transmission is realized in this system,with anti-interference,anti-Doppler effect and channel error correction capability.In addition,communication parameters such as working mode and rate according to the communication environment can be selected adaptively.This research has important theoretical significance and practical value.Firstly,the basic principles of DQPSK,DSSS,and non-integer multiple spread spectrum are introduced.And the detailed design schemes of DQPSK system,DSSS-DQPSK system and adaptive transmission system based on genetic algorithm are proposed,which enable the wireless data transmission system to satisfy two basic working modes of high speed and low speed.Moreover,it can achieve adaptive selection of communication parameters in different channel environments.Secondly,the synchronization module of the system is designed and improved according to the hardware implementation requirements.The FFT algorithm is used to estimate the large Doppler shift.The Costas tracking loop is used to extract the carrier.The Gardner symbol synchronization method is used for timing decision.For the non-integer multiple direct sequence spread spectrum system,the pseudo-code acquisition is difficult under large Doppler frequency offset.Due to this,based on the partial matched filter combined with the fast Fourier transform algorithm(PMF-FFT),an improved algorithm using quadruple frequency processing is proposed,which eliminates the phenomenon of symbol flipping during the integration period.In addition,the system is optimized by zero-padding and batching FFT algorithms,which reduces the scallop loss,improves the accuracy of carrier frequency estimation,and reduces hardware resource consumption.Then an adaptive data transmission system scheme based on genetic algorithm is designed,which can select and adjust the communication parameters adaptively by the intelligent decision module according to the estimated SNR and Doppler frequency shift value.The scheme further improves the adaptability of the system to different channel environments and ensures the transmission quality of the wireless link.Finally,according to the requirements of the project,the DQPSK system,DSSS-DQPSK system and adaptive data transmission system are simulated and analyzed,which verifies the effectiveness of the scheme design.Based on the designed scheme,the hardware implementation of the data transmission simulatorproduct has been completed by the project team,which further verifies the rationality and feasibility of the scheme design.