Phase noise spectral limits in OFDM systems

OFDM is recognized to be one of the best transmission techniques for wideband wireless communication systems. However, it exhibits two main drawbacks: its large amplitude fluctuation and its sensitivity to phase noise. Here we consider the phase noise impairments, taking care of the phase noise spectrum, which diverges form the classical Wiener model as the carrier frequency increases. Moreover, we show that the phase noise distortion can be decomposed in two terms, one dependent on the symbol under detection and the other dependent on the symbols of adjacent subcarriers, so that the performance degradation depends on both the constellation used in each subcarrier and the phase noise spectrum. As a consequence of this new results, the penalty due to phase noise expressed in terms of the average signal/noise plus interference ratio is not applicable in the case of modulations with non-constant amplitude constellations, such as 16- or 64-QAM. The method proposed here achieves a good accuracy, while keeping a low computational complexity, and it is confirmed by simulations.