Robust OFDM transmissions over frequency-selective channels with multiplicative time-selective effects

OFDM systems enable simple and e ective schemes to mitigate frequency selective fading channels. However, they are extremely sensitive to multiplicative uctuations induced by time-varying multipath delays, carrier o sets and oscillators' phase noise. Although the duration of OFDM symbols is chosen smaller than the channel coherence time to avoid, or reduce, channel time variations, this choice limits system eÆciency. In this paper, we propose a generalized OFDM scheme capable of estimating and then compensating channel frequency selectivity and multiplicative noise e ects using a deterministic method that exploits the redundancy added to the transmitted sequence in the form of pilot tones and null guard intervals in the frequency domain. The proposed method applies to channels modeled as the cascade of dispersive lters whose output is corrupted by both additive and multiplicative noise.