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. Roberto Corvaja was born in Padova (Italy) in 1967. He graduated at the Universisty of Padova in Electronic Enginering on 1990 and got his Ph.D. at the Univeristy of Padova in 1994. Since 1994 he is with the Dipartimento di Elettronica e Informatica of the University of Padova as a researcher and assistant professor on digital communications. Between 1994 and 1995 he spent 8 months at Hewlett-Packard Laboratories, Bristol (UK), working on equalization for a DECT receiver. His research activity in the past has regarded optical fibre communications systems and now is devoted to wireless communication systems. Silvano Pupolin was born in Venice, Italy, on February 17, 1947. He received the Laurea degree in Electronic Engineering from the University of Padova, Padova, Italy, in 1970. Since then he joined the Dipartimento di Elettronica e Informatica of the Universita' di Padova, where he currently is a Full Professor of Electrical Communications. He spent the summer 1985 at AT&T Bell Laboratories on leave from Padova, doing research on digital radio systems. He has been actively engaged in researches on digital communication systems since 1970. The topics covered has been: performance of baseband digital comunication systems, line encoding for spectral shaping, timing extraction, direct detection fiber optic system, spread spectrum communication systems, digital radio communications, with emphasis to the adaptive linearization of the High-Power-Amplifier. Actually, he is actively engaged in researches on digital radio, spread s pectrum systems, packet radio networks, personal communication systems and Cellular access to broadband systems for interactive communications. He is also National Project leader for a research on Personal Communication Systems. Dr. Pupolin is a Senior Member of IEEE and Member of AEI.