Key Technologies Research And Erification Of High Precision Sychronization Wireless Waveform

Timing synchronization and carrier synchronization is a key technique of wireless digital communication system.The whole system is guaranteed by time synchronization to work at the same time status.If the time synchronization failed,the signal-to-noise ratio of spread spectrum system will be decayed and the orthogonality between OFDM symbols will be destroyed.Carrier frequency synchronization guarantees there is no deviation in carriers.If the frequency synchronization failed,the demodulation of spread spectrum system will fail because of the phase accumulation error and the subcarrier orthogonality of OFDM system will be destroyed.Both Time and frequency synchronization are significant.Considering the excellent autocorrelation of CAZAC sequence,a time and frequency synchronization algorithm has been designed in this literature,which can effectively resist large frequency shift in low SNR,and implement on FPGA,based on cyclic CAZAC sequence.Firstly,the impaction of propagation loss and frequency shift of communication system has been analyzed,performance index of the system was then put forward based on research requirement,and frame structure was designed based on direct sequence spread spectrum and time and frequency synchronization algorithm based on CAZAC sequence was designed.Secondly,the communication link was simulated under AWGN channel after improving traditional time and frequency synchronization.It was showed in the result that,the time synchronization error was limited within ±1?4 chip time,and frequency synchronization accuracy was limited in ±1Hz,and finally frequency shift estimation ranged over ±63kHz.The bit error was less than10^-5when SNR upper than-25 dB.Thirdly,the implementation on FPGA of time and frequency synchronization was expressed particularly,including the ports constraints and treatment scheme of submodule,while designed top-down.Finally,this time and frequency synchronization software was tested under laboratory and outdoor environment.It was implied in the result that,this software reach the goal of time and frequency synchronization 、 RF-power control and information reporting.Furthermore,this software also work when SNR under-24 dB,and bit error is less than 10^-5when SNR under-22 dB.