Chapter 4 Wireless Technology
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CSMA/CA is used because of the way wireless networks communicate as
opposed to the way wired networks communicate. When communicating on a wired
network, all devices in the same collision domain can hear each other when they
are communicating. The idea is that each device waits for when the cable is clear of
communication before it communicates on the cable. When a collection of wireless
devices are connected as a network, not all devices will always be within the range
of all other devices. This causes a problem because a wireless device may not be
aware when other devices are communicating. This is why a wireless network system
requires CSMA/CA to access the network media, the wireless network area.
CSMA/CA is designed to make the WAP in charge of all communication.
The WAP permits wireless devices to communicate or denies wireless devices to
communicate. The WAP is centrally located and can communicate with all the
devices in the wireless network. The WAP hears all communication. A device
sitting at the edge of the wireless network cannot hear the devices farthest from
it, but the WAP can. If CSMA/CD was used as the access method, the devices
would not take turns as permitted by the WAP and the result would be too
many communication collisions on the network caused by two or more devices
attempting to communicate at the same time.
Adding more Wireless Access Points can expand the geographic area covered
by a wireless network, Figure 4-22. Connecting several WAPs with cable can
also enlarge a wireless LAN. Figure 4-23 shows several WAPs joined by copper
core cable. This connection allows multiple WAPs to be spread over a large area
Figure 4-22.
The range of a
wireless network
can be extended by
adding additional
Wireless Access
Points (WAPs).