Digital transmission of information has sufficiently overwhelming advantages that it increasingly dominates the design of communication systems. In computer-to-computer communication, the information to be transported is inherently digital, so digital transmission is the only practical alternative. But computer communication is still a small fraction of the world of digital communication. A much larger fraction is devoted to transmitting inherently analog signals, such as voice and images. Such signals can be (and traditionally have been) transmitted in analog form. Why would they be transmitted digitally? Doesn’t digital transmission squander bandwidth? Doesn’t it require more expensive hardware? After all, a voiceband data modem (for digital transmission over a telephone channel) costs ten times as much as a telephone and (in today’s technology) is incapable of transmitting voice signals with quality comparable to an ordinary telephone. This sounds like a serious indictment of digital transmission for analog signals, but for most applications, the advantages outweigh the disadvantages, and the communication world is going digital. In this chapter, we outline the reasons.
KeywordsPhysical Medium Analog Signal Video Signal Telecommunication Network Packet Switching
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