Improved parametric families of intersymbol interference-free Nyquist pulses using inner and outer functions

In this article, the authors introduce and study the performance of two novel parametric families of Nyquist intersymbol interference-free pulses. Using only two design parameters, the proposed pulses yield an enhanced performance compared to the sophisticated flipped-inverse hyperbolic secant (asech) filter, which was recently documented in the literature. Although the construction of parametric families originates from the work of Beaulieu and Damen, the authors´ approach is based on the concept of ´inner´ and ´outer´ functions and for this reason a higher flexibility in the choice of the family members is achieved. The proposed pulses may decay slower than the original raised-cosine (RC) pulse outside the pulse interval, but exhibit a more pronounced decrease in the amplitudes of the two largest sidelobes and this accounts for their improved robustness to error probabilities. It is clearly shown, via simulation results, that a lower bit error rate (BER), compared to the existing pulses, can be achieved for different values of the roll-off factor and timing jitter. Moreover, a smaller maximum distortion as well as a more open-eye diagram are attained which further demonstrate the superiority of the proposed pulse shaping filters.