The Research On The Timing And Frequency Synchronization Of OFDM

The research on the next mobile communications(4G) technology has been paidmore and attention as the globally applicable Technical Specifications and TechnicalReports for the 3rd Generation Mobile System(3G) are produced by 3GPP . OFDM(orthogonal frequency division multiplexing) splits a high-rate datastream into anumber of lower rate streams that are transmitted simultaneously over a number ofsubcarriers and become a key technology for 4G because of its high spectrumefficiency and robust capability of decreasing multipath interference .But OFDM system is very sensitive to timing errors and frequency offset for itmust keep the orthogonality between the subcarriers. The main task of this researchis to research on the timing and frequency synchronization techniques.First of all, this paper introduces briefly the basic principles of the OFDM systemand analyses thoroughly the effects of relevant nonideal transmission conditions suchas: symbol frame offset, carrier and sampling clock frequency offset and phase noise;then Cadence SPW software system is introduced .The two traditional algorithms areintroduced :one is based on the CP(cyclic prefix),the other is based on the trainingsymbols.In this paper, there are three innovations: the fore feedback structure is used tooptimize for the ML algorithm which is based on independent symbol;two-stepcompensation algorithm is used to combat the in the stage of integral frequencyoffset estimating;the average of training symbols is used to timing so as to combat themultipath channel fading.