Capacity of OFDM systems in Nakagami-m fading channels: The role of channel frequency selectivity

In this paper, we analyze the capacity of orthogonal frequency division multiplexing (OFDM) systems with carrier frequency offset (CFO) in frequency-selective Nakagami-m fading channels. Previous work on this topic has not taken into account the frequency selectivity of the channel. In this work, we have explicitly attributed the effect of channel frequency selectivity, i.e. frequency domain correlations, in evaluating the OFDM system performance in the presence of CFO. A closed-form expression is derived of the probability density function (PDF) of the signal-to-interference-and-noise ratio (SINR) in terms of CFO and channel correlation vector. Capacity is evaluated using numerical integration. The frequency-flat fading scenario and the perfectly frequency-selective fading (uncorrelated subcarriers) scenario form the two extremes, i.e. bounds, of the achievable OFDM capacity in the presence of CFO in Nakagami-m fading channels.