The k-Dimensional Distribution of Combined GFSR Sequences

We develop an efficient method for analysis of the fc-dimensional distribution of combinations of several GFSR sequences by bitwise exclusive-or operations. First, we introduce the notion of a resolution-wise lattice structure for GFSR sequences, and show that by applying a theorem of Couture to this type of lattice, we obtain a precise description of A;-dimensional distribution of combined GFSR sequences in the same way as for combined Tausworthe sequences. Finally, we apply this method to the combination of two different Twisted GFSR generators, which were recently proposed by Matsumoto and Kurita, and investigate the order of equidistribution of the combined sequence.