Research Of Synchronization And Interference Detection Techniques Based On OFDM System

With the development of communication technology,the demand for information,especially wireless multi-media and for high transmission speed is increasing day by day,which makes the wideband wireless communication technology become more and more mature and widely applicable in various fields.As a multi-carrier transmission technology,Orthogonal Frequency Division Multiplexing(OFDM),with the advantage of easy realization and high spectrum efficiency,can strongly combat multi-path and inter symbol interference,so it has become one of the most promising key technology in kinds of high-speed wideband wireless communication systems,including Digital Video Broadcasting(DVB),Wireless Local Area Network(WLAN)and 4G LTE.Meanwhile,the electromagnetic environment where exist various type of interference become increasingly complicated due to the rising number of communication equipment.In order to improve the anti-interference ability of OFDM system and guarantee the reliable data transmission,this paper will study the countermeasure technology of the OFDM system from two major aspects: anti-interference synchronization algorithm and interferen ce detection algorithm.To improve the performance of the synchronization in OFDM systems in the presence of interference,a new synchronization algorithm based on scrambl ing sequence is proposed in this paper,which redesigns the training sequence used in the algorithm with the constant amplitude zero auto-correlation(CAZAC)sequence and an extra scrambling operation.The new synchronization algorithm can still maintain the sharper correlation peak,and achieve accurate symbol timing estimation and carrier frequency offset estimation in the interference environment,with a lower out-of-band energy of the spectrum due to a new scrambling sequence.Furthermore,owing to the particularity of the component elements from scrambling sequence,a low complexity implementation structure is presented here to realize the correlation function of the proposed algorithm with less hardware resources.Finally,this paper does the research on the interference detection algorithm in the frequency domain,in which the principle of consecutive mean excision(CME)and forward consecutive mean excision(FCME)algorithms are analyzed in detail.Then through the simulation,this paper respectively discuss the influence of several factors(window functions,JNR and the length of the da ta)on the detection performance of these two algorithms.To reduce the time complexity of the FCME algorithm,we improve the data processing method in the initialization period and propose a new detection algorithm based on FCME,this new algorithm can ac hieve the same performance as FCME algorithm but with lower ti me complexity.