Channel modeling and associated inter-carrier interference equalization for OFDM systems with high Doppler spread

We address the problem of OFDM transmission over a time-varying, frequency-selective channel with high Doppler spread. This creates situations where the channel significantly evolves over the time span of one OFDM symbol. We analyze the CP-OFDM transmission mechanism, and the impairments due to channel variations, using a decomposition of these variations over a base of sinusoid functions sampling the Doppler spectrum at subcarrier frequencies. On the one hand, this leads to a fairly parsimonious parameterization of the time-varying channel impulse response. On the other hand we show that, considering a whole CP-OFDM symbol, this leads to a duality between equalization of the delay spread of a time-varying channel in the time domain, and the equalization of the Doppler spread of a frequency selective channel in the frequency domain. Using this duality, we show that equalization in the frequency domain can benefit from all known time domain equalization methods.