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21 Wireless Local Area Networks
The following are a few advantages of deploying WLANs:
Mobility improves productivity with real-time access to information, regardless
of worker location, for faster and more effi cient decision making
Cost-effective network setup for hard-to-wire locations such as older buildings
and solid wall structures
Reduced cost of ownership, particularly in a dynamic environment requiring
frequent modifi cation due to minimal wiring and installation costs per device
and per user
However, there are several issues that should be considered in deploying the
WLAN including:
Frequency allocation:
Operation of a wireless network requires that all
users operate in a common frequency band. The frequency band must be
approved in each country.
Interference and reliability:
In a wired LAN, one hears only the terminals
connected to the network. In a WLAN, interference is caused by simultaneous
transmission of information in the shared frequency band and by multipath
fading. The reliability of a communication channel is measured by bit error
rate (BER). Automatic repeat request (ARQ) and forward error correction
(FEC) techniques are used to increase reliability.
Security:
Radio waves are not confi ned to the boundary of buildings or
campuses. There exists the possibility of eavesdropping and intentional
interference. Data privacy over a radio medium is usually accomplished by
using encryption.
Power consumption:
WLANs are typically related to mobile applications.
In these applications, battery power is a scarce resource. Therefore, the
devices must be designed to be energy effi cient.
Mobility:
One of the advantages of a WLAN is the freedom of mobility.
The devices should accommodate handoff at transmission boundaries to
route data calls to mobile users.
Throughput:
To support multiple transmissions simultaneously, spread
spectrum techniques are often used.
