Time-Frequency Modeling and Estimation of Wireless OFDM Channels

Orthogonal Frequency Division Multiplexing (OFDM) has become a very popular method for high data rate wireless communications because of its advantages over single carrier modulation schemes on multi-path, frequency selective fading channels. However, inter-carrier interference due to Doppler frequency shifts, and multipath fading severely degrades the performance of OFDM systems. Estimation of channel parameters is required at the receiver. In this paper, we present a channel modeling and estimation method based on time-frequency representation of the received signal. The Discrete Evolutionary Transform provides a time-frequency procedure to obtain a complete characterization of the multi-path, fading and frequency selective channel. Performance of the proposed method is tested on different levels of channel noise, Doppler frequency shifts, and jamming interference powers. Key-Words: Wireless communications, OFDM, Channel estimation, Evolutionary spectrum.