Spectrally efficient digital modulation using new pulse shapes

Linear modulation schemes such as phase shift keying (PSK) and quadrature amplitude modulation (QAM) are inherently spectrally efficient. The authors seek enhanced spectral efficiency by designing new spectrally efficient pulse shapes for such digital modulations. The pulses designed are of finite duration and exhibit zero intersymbol interference when received through an additive white Gaussian noise (AWGN) channel. The authors show that the resulting communications signals have optimal spectral roll-off while maintaining optimum bit error ratio performance when received via an AWGN channel. The bandwidths and power spectral densities of communications signals using these pulses are compared with traditional spectrally efficient communications signals.