Digital modulation and pulse shaping

Abstract

Depending on the channel conditions, radio frequency hardware cost and properties, allowed complexity, required data rate, available bandwidth, and desired levels of performance some will provide a better fit than others. This chapter discusses some of these popularly used digital modulation and pulse-shaping techniques. When selecting a suitable modulation scheme, one needs to understand the requirements of the system as the choice of the modulation impacts the performance and complexity of the system significantly. Baseband pulse-shaping filtering is used in digital modulation to limit bandwidth and reduce inter-symbol interference (ISI). Square pulse shapes are not practical to be used in wireless communication systems as they require significant amount of bandwidth. In global system for mobile communications, because of the ISI caused by the pulse shaping filtering, at the receivers equalizers are needed even if the channel is frequency flat.