Consecutive Ofdm Signal Demodulation Synchronization Technology

OFDM is a promising technology for its high spectral efficiency and robustness to frequency selective fade, it is used more and more broadly in martial wireless communication. So there exist a problem of ferret receiving the signals which based on OFDM, and synchronization is the key point during ferret receiving the signals.On the basis of researching the influence of synchronization error to OFDM system performance, the synchronization of symbol-timing, carrier-frequency and sampling- clock in DVB-T system are investigated in both collaboration communication and the third party receiver, main work is completed as follows.Firstly, based on the frame structure of DVB-T signal, synchronization can be gotten by continued and scattered pilots of OFDM symbol in the collaboration communication. That is, symbol coarse timing and fraction carrier frequency offset can be gotten by traditional maximum likelihood estimation algorithm. Integral carrier frequency offset can be gotten by the continued pilots in two continue OFDM symbols. Sampling clock synchronization can be gotten by scattered pilots. Phase-offset can be adjusted by continued and scattered pilots. Simulation displays these selecting algorithms are thinkable in multi-paths channel.Secondly, in the third party receiver, the emphasis is puted on discussion of the estimation of carrier-frequency offset. That is, carrier-frequency offset can be estimated accurately by taking advantage of the inherent orthogonality among OFDM subchannels, the joint-estimation algorithm of carrier-frequency offset and sampling-clock offset can be gotten by the cross correlation of CP and the counterpart data in the end of OFDM symbol, integral carrier-frequency offset can be gotten by energy checking algorithm, and the phase offset can be compensated by the algorithm which mapping the constellation of receiving signal to the first quadrant, correct synchronization can be gotten in the condition of definite bit error rate.Thirdly, Matlab codes are translated to C codes, and the demonstrated platform of soft-demodulation is redacted. By the platform, the signal source afforded by the collaborator can be demodulated correctly. The process of synchronization demodulation can be displayed visually through the platform.