Research On Blind Synchronization For OFDM Based On PLC

OFDM modulation technology provides theory support for the power line communication (PLC) that needs high speed and reliability , but of which synchronization is actually the key . In this paper, the blind synchronization algorithms that can save the system bandwidth and improve the transmission rate are discussed and researched.At first, the research background, the status in quo of synchronization for OFDM and their principles are introduced.After the simulation for the characters of the multipath fading and variety of noises in the power-line channel, the main work is done as follows:1. On the basis of ML-type algorithms, an improved algorithm is proposed considering the Doppler frequency shift is zero in the power line communication and the delay generated by the multipath reflection is relatively stable in the power line channel, which is effective to overcome the limitations that ML-type algorithms are not fit for the power line channel and accordingly have a good performance on the estimation for the timing and frequency offset.2. An improved LS(least square) synchronization algorithm and its simplified one based on forward-backward slide window are presented considering the problem of the boundary blur when the original LS method makes timing synchronization, which improve the estimating performance .The simplified algorithm greatly reduces the computation amount but the synchronization performance decrease little.3. The second modified algorithm based on LS blind synchronization is proposed, which choose the middle one after make a queue of some timing points which have the biggest probability. The modified method not only reduces the computation amount and also improves the performance. 4. A approach of blind difference synchronization algorithm using multiple orthogonal frequency-division multiplexing (OFDM) symbols is proposed for OFDM systems on the basic of the algorithm of Kenkichi Takahashi,which has a better performance on timing synchronization.At last, in order to estimate the performance of the bit error rate of the four modified synchronization method in the realistic PLC, the whole baseband system of OFDM is simulated in the power-line channel cooperating with the knowledge of the channel coding and channel estimation and then a picture is transmitted and tested so as to have a sensible comparison.