Soft iterative interference cancellation with successive over relaxation for digital transmission schemes based on multiple sets of orthogonal spreading codes

Employing multiple sets of orthogonal spreading codes a bandwidth and power efficient digital transmission scheme can be realized. On each of the resulting subchannels antipodal transmission is used. Increasing the number of spreading codes, on the one hand, increases the data rate and thus the bandwidth efficiency of the transmission. On the other hand the interference between the subchannels is increased as well. This unavoidable interference resulting from non-orthogonal codes must be removed by an iterative vector detection algorithm (soft-decision iterative interference cancellation). We show, that these iterative methods can be improved with respect to convergence and convergence speed by applying the method of successive over relaxation.