Iterative Equalization for OFDM Systems Over Wideband MSML Channels
OFDM suffers from Inter-Carrier Interference (ICI) when the channel is time varying. This paper 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 the authors 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.