Linköping University Electronic Press

Every oscillator used in bandpass communication suffers from an instability of their phase (a.k.a. phase noise) that; if left unaddressed; can lead to great degradation of the system performance. In this paper; we tackle the problem of minimising the effect of oscillator phase noise on the coherent detection of a quadrature phase shift keying (QPSK) modulation operating on an Additive White Gaussian Noise (AWGN) channel. The phase noise process is modeled as a Wiener-Levy (random walk) process. Our approach uses maximum likelihood (ML) estimation of phase noise. Thorough analysis and derivation for Decision Directed (DD); Non-Data Aided (NDA); used with and without symbol differential encoding; and pilot based estimators are presented. We compare these estimators with respect to their main features and evaluate their bit error rate (BER) performances throught simulations. Results show that for low signal to noise ratio (SNR) applications; the use of differential encoding along with the proposed DD or NDA estimator yields performances with an SNR penalty below the two dB imposed by the non coherent detection methods; while pilot based estimation using wiener interpolation makes it possible to detect a QPSK modulation with SNR penalty around two dB.