A maximum likelihood fine timing estimation for wireless OFDM systems

Abstract

Timing synchronization is a critical issue for orthogonal frequency division multiplexing (OFDM) systems. Compared to the time-domain correlation schemes for OFDM timing synchronization, frequency-domain schemes can provide better performance due to their ability to resolve channel multipath. Employing a complex Gaussian model for the estimated OFDM channel impulse response (CIR), this paper derives the Cramer-Rao lower bound (CRLB) and a maximum likelihood estimate (MLE) for the timing offset parameter. The MLE is further simplified to be implementable with a delay locked loop (DLL) fine timing structure based on channel power delay profile (PDP). Using this scheme, the mean-square error of the symbol timing estimation can be reduced by orders of magnitude, when compared with the peak-finding fine timing schemes under multipath fading channels.