The effects of phase noise in COFDM

The reception of a COFDM signal is analyzed here for the case where phase noise has been added to the signal, e.g. by a receiver local oscillator. Two effects are distinguished: common phase error (a rotation of the signal constellation) and inter-carrier interference (similar to additive Gaussian noise). It is shown that the amounts of these effects can be deduced from the spectrum of the phase noise using a pair of weighting functions. Use of these weighting functions simplifies the process of computation; it also makes it easier to visualize the consequences of any modifications to the phase-noise spectrum. Some illustrations are given of the two phase-noise effects on the constellation of a DVB-T digital television signal, along with some practical observations on receiver implementation.