Reduced complexity decision feedback equalization for multipath channels with large delay spreads

Two modified decision feedback equalization (DFE) structures are presented for the efficient equalization of long sparse channels with strong precurso r, such as those encountered in high-speed communications over multipath ch annels with large delay spread. Unlike the conventional DFE, these structur es allow the channel's sparseness to be exploited by simple tap allocation, before the sparseness is degraded by feedforward filtering. Both structure s yield large reductions in complexity while maintaining performance compar able to the conventional DFE, hence overcoming a key computational bottlene ck when equalizers are implemented in hardware for speed. Fast channel esti mate-based algorithms for computing the modified DFE coefficients are deriv ed. Simulation results are presented for data rates and channel profiles of the type considered for the proposed North American high definition televi sion (HDTV) terrestrial broadcast mode.