Wireless Network Hardware
The network hardware used in wireless computer
networks performs the same functions as the equipment used in wired networks:
it connects the computers and other hardware to a common network. Network
adapters, hubs, and routers are used in wireless networks, just as in wired
networks. In addition, special devices—access points and bridges—are used for
wireless data transmission over various distances.
Network Adapters
A wireless adapter is a unique interface designed
for hardware devices—computers, servers, printers and scanners. Hardware
devices communicate with each other in the computer network using the network
adapters. Each hardware device needs its own wireless network adapter to
connect to a wireless network. Hardware devices with wireless network adapters
can communicate directly with each other provided that they are within the
operating range of the network adapters. Such communications is called “ad
hoc” or “peer-to-peer” networking. For example, three network adapters (one
for each device) are needed for two computers and a printer to communicate in
an ad hoc network. An ad hoc network is the simplest and least expensive
network for small home networks and networks in small companies. Network
adapters are divided into internal adapters (also called "wireless network
cards" since they are built into the hardware device or inserted into an
internal port in the hardware device) and external adapters (connected to an
external port on the hardware device).
Access Points
Wireless access points are used for networks
consisting of a large number of computers, and where the capacity or operating
range of a network must be expanded. An access point in a wireless network
performs the same function as a telephone exchange or switchboard in a
telephone network. Just as telephone exchanges or switchboards are used to
connect distant telephones, the access points are the wireless communications
nodes for the hardware devices in the computer network. The hardware devices
equipped with network adapters establish communications with the access point,
and can communicate and exchange data with other devices in the network via
this access point. A network configuration in which devices communicate with
each other through an access point is called an “infrastructure mode”. The use
of several access points makes it possible to significantly expand the
operating radius of an office network where hardware devices are located on
different floors of a building or in different buildings on the company
premises. Access points can also be used as routers to create hybrid networks
where wireless networks connect to existing wired LANs or to the Internet.
Bridges
So-called “bridges” are used where two or more
remote sites need a wireless connection to each other. At least two access
points equipped with antennas pointed at each other are needed to create a
bridge. For example, a bridge may be needed if independent LANs located at
geographically remote offices of a company need to be connected. A bridge is
also needed to connect networks in different buildings on the company
premises. Like highway or railway bridges, wireless bridges may be single-span
or multispan bridges. Access points operating in repeater mode to relay the
signal from adjacent access points are used to support bridges for long-range
communications and to connect individual segments in multispan bridges.
Antennas
Access points equipped with powerful directional
antennas that significantly increase the operating range of the radio signal
are used to create bridges. The antennas differ in directivity, gain, radio
signal frequency supported, shape, and design.
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