Lower Bound of SNR Fall Caused by ICI Based on All Phase OFDM Systems

This paper discusses the effects of frequency offset on the performance of all phase orthogonal frequency division multiplexing (AP-OFDM) digital communications. There are two deleterious effects caused by frequency offset; one is the reduction of signal amplitude in the output of the filters matched to each of the carriers and the second is introduction of intercarriers interference (ICI) from the other carriers which are now no longer orthogonal to the filter. lower bound of SNR fall caused by ICI has been obtained through numerical method. It is shown, and implemented by simulation, that to maintain signal-to-interference ratios of 20 dB or greater for the OFDM carriers, offset is limited to 15% or less of estimate frequency offset using an all phase estimator. Its performance computed and compared with the conventional OFDM simulation results. Since the ICI energy and signal energy both contribute coherently to the estimator, the algorithm generates extremely accurate estimates even when the offset is far too great to demodulate the data values.