Orthogonal frequency division multiplexing (OFDM) is a bandwidth efficient transmission technique which easily handles time dispersion of channel. It has been adopted by the IEEE 802.11a standard as the transmission technique for high-rate wireless local area networks (WLANs). See the supplement to IEEE standard for Information Technology Telecommunications And Information Exchange Between Systems—Local And Metropolitan Area Networks Specific Requirements. Part 11: wireless LAN Medium Access Control (MAC) and Physical Layer (PHY), IEEE Std 802.11a, December 1999. The data packet of the IEEE 802.11a standard consists of two parts: the preamble and the data. The preamble includes short and long pilots which are used, e.g., for synchronization, frequency offset and channel estimation. Pilot-aided OFDM channel estimation is discussed in O. Edfors, M. Sandell, J. V. D. Beek, S. Kate and P. O. Borjesson, “OFDM Channel Estimation By Singular Value Decomposition,” IEEE Trans. Commun., vol. 46, no. 7, pp. 931-939, July 1998. Frequency offset corrections have been presented in many papers, including P. H. Moose, “A Technique For Orthogonal Frequency Division Multiplexing Frequency Offset Correction,” IEEE Trans. Commun., vol. 42, pp. 2908-2914, October 1994; and in M. A. Visser and Y. Bar-Ness, “OFDM Frequency Offset Correction Using An Adaptive Decorrelator,” CISS'32, Princeton, N.J., pp. 483-488, March 1998. However, Wiener phase noise, the effect of which has also been examined in T. Pollet, M. V. Bladel and M. Moeneclaey, “BER Sensitivity Of OFDM Systems To Carrier Frequency Offset And Wiener Phase Noise,” IEEE Trans. Commun., vol. 43, no. 2, pp. 191-193, February 1995, proves to be a much more complex phenomenon than frequency offset. In the present invention what is termed a phase noise suppression (PNS) algorithm is used to eliminate the effect of this noise.
USPTO Backgrounds
USPTO Backgrounds