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Chapter 7 Telecommunications, the Internet, and Wireless Technology 309

physically in the transmitters, and Bluetooth has saved FedEx $20 million
per year.

Wi-Fi and Wireless Internet Access
The 802.11 set of standards for wireless LANs and wireless Internet access is
also known as Wi-Fi. The first of these standards to be widely adopted was
802.11b, which can transmit up to 11 Mbps in the unlicensed 2.4-GHz band and
has an effective distance of 30 to 50 meters. The 802.11g standard can transmit
up to 54 Mbps in the 2.4-GHz range. 802.11n is capable of transmitting over
100 Mbps. Today’s PCs and netbooks have built-in support for Wi-Fi, as do the
iPhone, iPad, and other smartphones.
In most Wi-Fi communication, wireless devices communicate with a wired
LAN using access points. An access point is a box consisting of a radio receiver/
transmitter and antennas that links to a wired network, router, or hub. Mobile
access points such as Verizon's Mobile Hotspots use the existing cellular net-
work to create Wi-Fi connections.
Figure 7.14 illustrates an 802.11 wireless LAN that connects a small number
of mobile devices to a larger wired LAN and to the Internet. Most wireless
devices are client machines. The servers that the mobile client stations need to
use are on the wired LAN. The access point controls the wireless stations and
acts as a bridge between the main wired LAN and the wireless LAN. (A bridge
connects two LANs based on different technologies.) The access point also con-
trols the wireless stations.

FIGURE 7.14 AN 802.11 WIRELESS LAN

Mobile laptop computers equipped with network interface cards link to the wired LAN by
communicating with the access point. The access point uses radio waves to transmit network signals
from the wired network to the client adapters, which convert them into data that the mobile device
can understand. The client adapter then transmits the data from the mobile device back to the access
point, which forwards the data to the wired network.

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