Computer Networks 4th Ed Andrew S. Tanenbaum [Electronic resources] نسخه متنی

Chapter 2. The Physical Layer

In this chapter we will look at the lowest layer depicted in the hierarchy of Fig. 1-24. It defines the mechanical, electrical, and timing interfaces to the network. We will begin with a theoretical analysis of data transmission, only to discover that Mother (Parent?) Nature puts some limits on what can be sent over a channel.

Then we will cover three kinds of transmission media: guided (copper wire and fiber optics), wireless (terrestrial radio), and satellite. This material will provide background information on the key transmission technologies used in modern networks.

The remainder of the chapter will be devoted to three examples of communication systems used in practice for wide area computer networks: the (fixed) telephone system, the mobile phone system, and the cable television system. All three use fiber optics in the backbone, but they are organized differently and use different technologies for the last mile.