Timing recovery for OFDM transmission

摘要

Orthogonal frequency division multiplexing (OFDM) is an effectivenmodulation technique for high-rate and high-speed transmission overnfrequency selective fading channels. However, OFDM systems can benextremely sensitive and vulnerable to synchronization errors. In thisnpaper, we present a scheme for performing timing recovery that includesnsymbol synchronization and sampling clock synchronization in OFDMnsystems. The scheme is based on pilot subcarriers. In the scheme, we usena path time delay estimation method to improve the accuracy of thencorrelation-based symbol synchronization methods, and use a delay-lockednloop (DLL) to do the sampling clock synchronization. It is shown that bynusing this scheme, the mean square values of the symbol timingnestimation error can be decreased by several orders of magnitudencompared to the common correlation methods in both the AWGN andnmultipath fading channels. In addition, the scheme can track the symbolntiming drift caused by the sampling clock frequency offsets