Digital Communication Systems
Khurshed Ahmad Shah, Brijesh Kumbhani, Raul F. Garcia-Sanchez, Prabhakar Misra · 2021
In Chapter 5 , the aspects of digital signal transmission over wireless media is discussed. We discuss various pulse-based modulation schemes as well as digital modulation schemes. The vector representation of digitally modulated signal has been discussed using Gram-Schmidt orthogonalization. Further, digitally modulated signals are represented graphically as signal constellation using constellation diagrams. The effect of noise on constellation diagrams is demonstrated and its effect on the receiver performance has been discussed. Spread spectrum technique and its immunity to noise are also discussed. Finally, the code division multiple access (CDMA) has been discussed as a technique to serve multiple users over common time frequency resources.