Hardware Reference
In-Depth Information
Wireless repeaters/range extenders —A repeater can stretch the range of an existing
wireless network. Some can also serve as access points or wireless bridges.
Specialized antennas —The “rabbit ears” antennas used by most access points and
routers are adequate for short distances, but longer distances or problems with line-
of-sight reception can be solved by attaching high-gain replacements for the originals,
or by attaching more specialized directional antennas, possibly on extension cables to
mount them higher for greater range.
Signal boosters —In addition to or as an alternative to replacement antennas, some
vendorsalsosellsignalboostersthatpiggybackontoanexistingaccesspointorrouter.
Note that, in most cases, these signal boosters are vendor specific.
Wireless Network Logical Topologies
Wirelessnetworkshavedifferenttopologies,justaswirednetworksdo.However,wireless
networks use only two logical topologies:
Star —The star topology, used by Wi-Fi/IEEE 802.11-based products in the infra-
structuremode,resemblesthetopologyusedby10BASE-TandfasterversionsofEth-
ernet that use a switch (or hub). The access point takes the place of the switch because
stations connect via the access point, rather than directly with each other. This meth-
od is much more expensive per unit but permits performance in excess of 10BASE-T
Ethernet speeds and has the added bonus of being easier to manage.
Point-to-point —Bluetooth products (as well as Wi-Fi products in the ad hoc mode)
use the point-to-point topology. These devices connect directly with each other and
require no access point or other hub-like device to communicate with each other, al-
though shared Internet access does require that all computers connect to a common
wireless gateway. The point-to-point topology is much less expensive per unit than a
startopology.Itis,however,bestsuitedfortemporarydatasharingwithanotherdevice
(Bluetooth) and is currently much slower than 100BASE-TX networks.
Figure 17.19 shows a comparison of wireless networks using these two topologies.
Figure 17.19 A logical star topology (left) as used by IEEE 802.11-based wireless Ethernet in infrastruc-
ture mode compared to a point-to-point topology as used by Bluetooth and 802.11 in ad hoc mode (right).
 
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