Spreading Sequence Design Via Perfect-Reconstruction Filter Banks

"Digital transmultiplexers, i.e., synthesis/analysis filter banks, traditionally employed for TDMA to FDMA conversion and vice-versa, provide also a multirate model for channel distortion free DS-CDMA systems, with the synthesis filter impulse responses playing the role of spreading sequences. Orthogonal filter banks constitute therefore an appropriate framework for designing new orthogonal codes and have been shown to give rise to codes with improved performance compared to classical ones (Gold). This paper investigates the possibility for further improvements via exploiting the additional freedom present in biorthogonal filter banks."