Average capacity of Rayleigh-fading OFDM link with wiener phase noise and frequency offset

We derive the average capacity for an OFDM radio link that is impaired by phase noise and carrier frequency offset at both transmitter and receiver side. It is well known that, for OFDM, phase noise and frequency offset cause intercarrier interference (ICI). We first notice the dependency of the instantaneous capacity on the ICI power and on the fading channel. Using a Taylor series approximation, we show that the ICI power can be well represented in a quadratic form whose probability density function we derive. Using the derived distribution and assuming a Rayleigh-fading channel, we derive analytical expressions of average capacity. Different test cases are presented to study the sensitivity of the capacity on phase noise and frequency offset. The main observations suggest that, for reasonable phase noise levels, the capacity is practically insensitive to the frequency offset.