Doubly Selective Channel Estimation for OFDM Systems

We propose a new pilot-aided algorithm for estimating doubly selective fading channels in OFDM systems. Our approach is valid for time varying channel, which occur for example, in mobile WiMAX and DVB-T. For time invariant channels, our scheme yields perfect estimates. The proposed algorithm is based on the principle of basis expansion and relies on Legendre polynomials as bases functions. We are using the block-type pilot structure in our algorithm, in which a complete OFDM symbol is dedicated to pilots before transmitting the data symbols, which my vary in number according to channel conditions. Numerical simulations illustrate the gain in the performance, bandwidth, power efficiency, and complexity gains achieved by our schemes at high Doppler frequencies. Our approach does not require any prior statistical channel information.