Analysis of the narrowband interference effect on frequency ambiguity resolution for OFDM systems

In orthogonal frequency division multiplexed (OFDM) systems affected by carrier frequency offsets, frequency ambiguity resolution, i.e. the estimation of the part of the frequency offset corresponding to an integer times the carrier spacing is a crucial issue. The proper action of frequency ambiguity resolution algorithms can be strongly affected by the presence of disturbances, like narrowband interference (NBI). In this paper, the susceptibility of the blind and data aided maximum likelihood (ML) frequency ambiguity estimators to NBI signals, which may arise in the OFDM band as the spectrum becomes more crowded, is investigated in an analytical way. The analytical results are verified by means of simulations. Although the estimators turn out to be essentially independent of the bandwidth of the interferers and the number of interferers, the performance of the estimators is very sensitive to the positions of the interferers when the interferers are strong. Copyright (C) 2008 John Wiley & Sons, Ltd.