Joint channel and phase noise estimation in OFDM using KL expansion

In mobile orthogonal frequency division multiplexing (OFDM) systems, time-varying channels result in severe intercarrier interference (ICI). At the same time, random phase noise introduced by the oscillator also causes two effects: the common phase error (CPE), and the ICI. The upper two factors together greatly degrade the OFDM system performance. However, the existing ICI reduction method is only aimed at a single interference source, i.e., either time-varying channels or phase noise. So, it cannot solve the actual case. In this paper, we analyze the ICI generated by the two factors together and propose a pilot-aided joint time-varying channel and phase noise estimation algorithm based on Karhunen-Lòeve basis expansion model (KL-BEM). The model is optimal in the minimum mean square error (MMSE) sense. So, it can make ICI reduction more effective. Simulation results confirm our theoretical results and illustrate that the proposed algorithm is capable of jointly estimating time-varying channels and phase noise.