Two modified decision feedback equalization (DFE) structures are presented for the efficient equalization of long sparse channels with strong precursor, such as those encountered in high-speed communications over multipath channels with large delay spread. Unlike the conventional DFE, these structures allow the channel's sparseness to be exploited by simple tap allocation, before the sparseness is degraded by feedforward filtering. Both structures yield large reductions in complexity while maintaining performance comparable to the conventional DPE, hence overcoming a key computational bottleneck when equalizers are implemented in hardware for speed. Fast channel estimate-based algorithms for computing the modified DFE coefficients are derived. Simulation results are presented for data rates and channel profiles of the type considered for the proposed North American high definition television (HDTV) terrestrial broadcast mode.

Decision feedback equalization (DFE) structures have been proposed for the efficient equalization of wireless channels with long postcursor response, which is a bottleneck problem for high speed communications over multipath channels with large delay spread. These structures are equivalent to the conventional DFE, but remove postcursor intersymbol interference (ISI) prior to feedforward filtering. We investigate the relationship between these structures and fast equalizer coefficient computation. Based on this relationship, we obtain a fast algorithm for computing optimal DFE settings which has significantly lower complexity than other known approaches for these high speed wireless channels. An example is given for data rates and channel profiles of the type considered for the proposed North American high definition television (HDTV) terrestrial broadcast mode.