Iterative equalization for OFDM systems over wideband Multi-Scale Multi-Lag channels
1 Delft University of Technology, Mekelweg 4, Delft, 2628CD, The Netherlands
2 TNO, Oude Waalsdorperweg 63, The Hague, 2597 AK, The Netherlands
EURASIP Journal on Wireless Communications and Networking 2012, 2012:280 doi:10.1186/1687-1499-2012-280Published: 31 August 2012
OFDM suffers from inter-carrier interference (ICI) when the channel is time varying. This article seeks to quantify the amount of interference resulting from wideband OFDM channels, which are assumed to follow the multi-scale multi-lag (MSML) model. The MSML channel model results in full channel matrices both in the frequency and time domains. However, banded approximations are possible, leading to a significant reduction in the equalization complexity. Measures for determining whether a time-domain or frequency-domain approach should be undertaken are provided based on the interference analysis, and we propose to use the conjugate gradient (CG) algorithm to equalize the channel iteratively. The suitability of a preconditioning technique, that often accompanies the CG method to accelerate the convergence, is also discussed. We show that in order for the diagonal preconditioner to function properly, optimal resampling is indispensable.