Optimum Pulse Shaping Application of Walsh-Functions used in MSK

ABSTRACT Minimum Shift Keying (MSK) is considered to be a spectrally efficient modulation scheme, in comparison with other families of constant envelope modulation. However, its main sidelobe can be of some worry in digital data transmission, particularly over nonlinear channels. Therefore, it is practically of interest to search for efficient pulse shaping schemes, largely proposed either through baseband pulse shaping and/or filtering processing. In this paper a new pulse shaping method based on Walsh functions is proposed to be used in MSK-type signaling. A methodology is proposed for designing the optimum pulse shape; and this attains improvement in spectral efficiency (i.e., bps/Hz) over straight MSK, for the same channel bandwidth. The fractional out-of-band power is used to compare the behavior of the system under the new proposed technique. As well, error rate performance in such system is used in the evaluation of this work. Results reveal that good improvement can be attained in spectral efficiency at the expense of error rate performance when these functions are used.