. MUCH OF HIS DISCOVERIES RELATED TO ELECTROMAGNETISM WERE BASED...

1879). Much of his discoveries related to electromagnetism were based on research done

by Michael Faraday (1791 to 1867) and Andre-Marie Ampere (1775 to 1836), who were

researchers that came before him. Heinrich Hertz (1857 to 1894) built on the discoveries

of Maxwell by proving that electromagnetic waves travel at the speed of light and that

electricity can be carried on these waves.

Although these discoveries are interesting, you might be asking yourself how they relate

to wireless local-area networks (WLANs). Here is the tie-in: In standard LANs, data is

propagated over wires such as an Ethernet cable, in the form of electrical signals. The dis-

covery that Hertz made opens the airways to transfer the same data, as electrical signals,

without wires. Therefore, the simple answer to the relationship between WLANs and the

other discoveries previously mentioned is that a WLAN is a LAN that does not need ca-

bles to transfer data between devices, and this technology exists because of the research

and discoveries that Herschel, Maxwell, Ampere, and Hertz made. This is accomplished

by way of Radio Frequencies (RF).

With RF, the goal is to send as much data as far as possible and as fast as possible. The

problem is the numerous influences on radio frequencies that need to be either overcome

or dealt with. One of these problems is interference, which is discussed at length in

Chapter 5, “Antennae Communications.” For now, just understand that the concept of

wireless LANs is doable, but it is not always going to be easy. To begin to understand how

to overcome the issues, and for that matter what the issues are, you need to understand

how RF is used.

How Bandwidth Is Achieved from RF Signals

To send data over the airwaves, the IEEE has developed the 802.11 specification, which de-

fines half-duplex operations using the same frequency for send and receive operations on a

WLAN. No licensing is required to use the 802.11 standards; however, you must follow the

rules that the FCC has set forth. The IEEE defines standards that help to operate within

the FCC rules. The FCC governs not only the frequencies that can be used without li-

censes but the power levels at which WLAN devices can operate, the transmission tech-

nologies that can be used, and the locations where certain WLAN devices can be

deployed.