Wow, the last chapter, which is about something that came first. Before there were digital communications, before there were source coding and channel coding and digital modulation and equalization, there were analog communications.
I will not go into the details of analog communications in this book, because in most cases it is being quickly replaced by powerful digital communication techniques. But, because some of what currently exists in the world today was built when there was only analog, it is important to have a basic understanding of it.
12.1 Modulation–An Overview
An analog communication system, roughly speaking, looks like what is drawn in Figure 12.1. You can see that the information signal x(t) ...