Instantaneous Capacity of OFDM on Rayleigh-Fading Channels

For a power limited orthogonal frequency-division multiplexing (OFDM) system transmitting a large number N of subcarriers over a Rayleigh-fading channel, the distribution of the instantaneous capacity is shown to be approximately Gaussian. The mean and variance of the approximating distribution are derived. It is also shown that, in the limit as Nrarrinfin, the capacity approaches a constant value equal to the capacity of the infinite-bandwidth Gaussian channel