ML frequency synchronisation for OFDM systems in the presence of overlapped narrow band transmission systems

Abstract

AbstractSpectrum‐overlay scenarios for wideband orthogonal frequency division multiplexing (OFDM) systems bring along new technical challenges that must be considered during the system design. In such a scenario, the receiver has to perform actions, such as channel estimation and synchronisation, in the presence of possibly strong in‐band interference. In this paper, we derive the data‐aided maximum likelihood (ML) fractional frequency estimator in the presence of narrow band interference (NBI) signals. Based on the ML algorithm which has a high complexity, we propose a number of simplifications to develop a lower complexity algorithm. The susceptibility of the simplified estimator to NBI signals is investigated in an analytical way. The analytical results are verified by means of simulations. Although the simplified estimator turns out to be essentially independent of the bandwidth and the location of the interferers, the performance of the estimator is very sensitive to the signal‐to‐interference ratio and the number of interferers. In contrast with the simplified estimator, simulation results indicate that the exact ML estimator is independent of the NBI signals. Copyright © 2008 John Wiley & Sons, Ltd.