Phase Noise Suppression for OFDM Systems Over Fast Time-Varying Channels

This paper derives a phase-noise suppression scheme for orthogonal frequency division multiplexing (OFDM) systems. This scheme is a maximum likelihood approach that exploits the pilot subcarriers that exist in almost all practical OFDM systems. Compared with existing work, the proposed scheme has the following features: (a) we focus on phase-noise suppression for time-varying environments, which also cause intercarrier interference (ICI) along with phase noise. Most of the existing work considers quasi-static channels and tries to suppress the common phase error (CPE). As will be shown in this paper, in more realistic fast time-varying channels, the CPE term becomes much more complex and might significantly degrade the performance of estimators that assume a time-invariant channel, (b) the proposed algorithm is applicable for the two most common types of local oscillators: phase-locked and free-running, which have different phase-noise characteristics, (c) the proposed phase-noise suppression scheme does not require perfect channel equalization, whereas in some of the existing work the channel is assumed to be known a priori, and (d) doubly-selective fading is considered rather than assuming a time-invariant and/or flat- fading channel.