Refined Bounds for Inter-Carrier Interference in OFDM Due to Time-Varying Channels and Phase Noise

Inter-carrier interference (ICI) due to time-variations of the channel and phase noise is a critical issue in current orthogonal frequency division multiplexing (OFDM) systems. For the discrete-time formulation of OFDM and the general case of partially occupied contiguous subcarriers, we present exact expressions for the average ICI power at each subcarrier. These lead to insightful lower and upper bounds for the bandwidth-averaged ICI power, which bring out the combined impact of Doppler spread and phase noise statistics. The bounds are tighter than those in the literature, which employ a tractable, but less accurate, continuous-time formulation and assume infinitely many subcarriers.