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.
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