Interference Analysis of Filtered Multitone Modulation Over Time-Varying Frequency- Selective Fading Channels

We consider in this paper filtered multitone (FMT) modulation over frequency-selective time-varying fading channels. Due to the phase and amplitude distortion introduced by the fading channel, not only is the orthogonality among different subcarriers destroyed, but also the perfect Nyquist sampling condition of the baseband matched filters is no longer valid. Consequently, interchannel, as well as intersymbol, interference will cause distortions to the transmitted signals. In this paper, the interference caused by the channel frequency selectivity and time variance is quantified by analyzing the demodulated signals at the receiver under several different fading-channel conditions. An analysis of the average carrier-to-interference (C/I) ratio of the FMT system is provided in order to demonstrate the underlying tradeoff between spectral efficiency and system performance. For comparison purposes with other multicarrier communication systems (or modulation techniques), the C/I ratio of the conventional orthogonal frequency-division multiplexing system is also provided and compared with that of the FMT system under the same channel conditions and spectral efficiency. Finally, numerical and simulation results are given that confirm the C/I ratio results obtained.