Dimitrios-Alexandros Toumpakaris

Optimum symbol timing estimation with various performance measures for OFDM systems

This paper presents blind symbol timing estimators in orthogonal frequency division multiplexing (OFDM) systems for the additive white Gaussian noise (AWGN) channel. Depending on the performance measure, different optimal estimators can be devised. The existing maximum likelihood estimator is optimal in the sense that it maximizes the probability that the symbol timing estimation error is zero, but it does not guarantee that the error will be small when the estimate is incorrect. When maintaining small error magnitude is critical, the minimum mean square error estimator can be developed with the objective of minimizing the mean square error. In some practical scenarios, the estimation error needs to be defined as the distance between the starting point of the fast-Fourier transform window and the region consisting of the cyclic prefix samples and the first useful sample. With this modified definition of the estimation error, the minimum failure probability estimator and the minimum modified mean square error estimator can be derived. The performance of the proposed estimators is compared with that of the maximum likelihood estimator using simulation.