Channel estimation for MC-CDMA with compensation of synchronization errors

In this paper, we investigate channel estimation for MC-CDMA in the presence of time and frequency synchronization errors. Channel estimation in MC-CDMA requires transmission of pilot tones, based on which MMSE interpolation or FFT-based interpolation algorithms are applied. Most channel estimation methods in the literature assume perfect synchronization. However, this condition is not guaranteed in the actual case, and channel estimators are always expected to work as a fine synchronizer which has some ability to compensate synchronization errors. Multicarrier systems are very sensitive to synchronization errors. Uncorrected errors cause intercarrier interference (ICI) and degrade the performance significantly. In this paper, we analyze the effect of synchronization errors on the performance of pilot-aided channel estimators, and propose low complexity methods to compensate the residual timing and frequency offset respectively. We estimate the timing offset in the frequency domain by a single frequency estimation technique, and iteratively search the frequency offset based on the interference power at the certain set of subcarriers. Simulation results show that our methods improve the performance of channel estimators considerably in imperfect synchronization conditions.