Performance of Reduced-Bandwidth 16 QAM with Decision-Feedback Equalization

This paper presents and investigates the performance of a reduced-bandwidth 16 QAM (RB-16 QAM) signaling technique which employs severe narrow-band filtering and decision-feedback equalization in the receiver to compensate for the resulting intersymbol interference. The overall filtering is designed so as to provide the spectral efficiency of 64 QAM. RB-16 QAM is compared to 64 QAM in terms of its performance on additive white Gaussian noise channels, in multipath fading environment, as well as in terms of its sensitivity to modem imperfections including carrier and timing phase errors, filter imperfections, nonlinear distortion and sinusoidal interference. The results show that depending on the spectral shaping filters and the equalizer used, RB16 QAM can be significantly more advantageous than 64 QAM. A most interesting finding is that while RB-16 QAM is comparable to 64 QAM in terms of its spectral efficiency, its robustness against system imperfections is very much like that of conventional 16 QAM.