WLAN Customer Considerations
 Range/Coverage
Throughput
Multipath
Effects
Integrity
and Reliability
Interoperability
with Wired Infrastructure
Interference
and Coexistence
Simplicity/Ease
of Use
Security
Cost
Scalability
Battery
Life for Mobile Platforms
Safety
While wireless LANs provide installation and configuration flexibility and
the freedom inherent in network mobility, customers should be aware of the
following factors when considering wireless LAN systems.
The distance over which RF and IR waves can communicate
is a function of product design (including transmitted power and receiver
design) and the propagation path, especially in indoor environments. Interactions
with typical building objects, including walls, metal, and even people, can
affect how energy propagates, and thus what range and coverage a particular
system achieves. IR is blocked by solid objects, which provides additional
limitations. Most wireless LAN systems use RF because radio waves can penetrate
many indoor walls and surfaces. The range (or radius of coverage) for typical
WLAN systems varies from under 100 feet to more than 300 feet. Coverage can
be extended, and true freedom of mobility via roaming, provided through
microcells.
As with wired LAN systems, actual throughput in wireless
LANs is product and set-up dependent. Factors that affect throughput include
airwave congestion (number of users), propagation factors such as range and
multipath, the type of WLAN system used, as well as the latency and bottlenecks
on the wired portions of the WLAN. Typical data rates range from 1 to 10
Mbps. Users of traditional Ethernet LANs generally experience little difference
in performance when using a wireless LAN and can expect similar latency
behavior.Wireless LANs provide throughput sufficient for the most common
LAN-based office applications, including electronic mail exchange, access
to shared peripherals, and access to multi-user databases and applications.
As Figure 9 shows, a radio signal can take multiple paths
from a transmitter to a receiver, an attribute called multipath. Reflections
of the signals can cause them to become stronger or weaker, which can affect
data throughput. Some designs and technologies are better at compensating
for multipath effects than others.
Figure 9. Radio Signals Traveling over Multiple Paths
Wireless data technologies have been proven through more
than fifty years of wireless application in both commercial and military
systems. While radio interference can cause degradation in throughput, such
interference is rare in the workplace. Robust designs of proven WLAN technology
and the limited distance over which signals travel result in connections
that are far more robust than cellular phone connections and provide data
integrity performance equal to or better than wired networking.
Wireless data technologies have been proven through more
than fifty years of wireless application in both commercial and military
systems. While radio interference can cause degradation in throughput, such
interference is rare in the workplace. Robust designs of proven WLAN technology
and the limited distance over which signals travel result in connections
that are far more robust than cellular phone connections and provide data
integrity performance equal to or better than wired networking.
The unlicensed nature of radio-based wireless LANs means
that other products that transmit energy in the same frequency spectrum can
potentially provide some measure of interference to a WLAN system. Micro-wave
ovens are a potential concern, but most WLAN manufacturers design their products
to account for microwave interference. Another concern is the co-location
of multiple WLANs. While WLANs from some manufacturers interfere with WLANs,
others coexist without interference. This issue is best addressed directly
with the appropriate vendors.
Users need very little new information to take advantage
of wireless LANs. Because the wireless nature of a WLAN is transparent to
a user's NOS, applications work the same as they do on tethered LANs. WLAN
products incorporate a variety of diagnostic tools to address issues associated
with the wireless elements of the system; however, products are designed
so that most users rarely need these tools.
WLANs simplify many of the installation and configuration
issues that plague network managers. Since only the access points of WLANs
require cabling, network managers are freed from pulling cables for WLAN
end users. Lack of cabling also makes moves, adds, and changes trivial operations
on WLANs. Finally, the portable nature of WLANs lets network managers
preconfigure and troubleshoot entire networks before installing them at remote
locations. Once configured, WLANs can be moved from place to place with little
or no modification.
Because wireless technology has roots in military applications,
security has long been a design criterion for wireless devices. Security
provisions are typically built into wireless LANs, making them more secure
than most wired LANs. It is extremely difficult for unintended receivers
(eavesdroppers) to listen in on wireless LAN traffic. Complex encryption
techniques make it impossible for all but the most sophisticated to gain
unauthorized access to network traffic. In general, individual nodes must
be security-enabled before they are allowed to participate in network
traffic.
A wireless LAN implementation includes both infrastructure
costs, for the wireless access points, and user costs, for the wireless LAN
adapters. Infrastructure costs depend primarily on the number of access points
deployed; access points range in price from $1,000 to $2000. The number of
access points typically depends on the required coverage region and/or the
number and type of users to be serviced. The coverage area is proportional
to the square of the product range. Wireless LAN adapters are required for
standard computer platforms, and range in price from $300 to $1,000.
The cost of installing and maintaining a wireless LAN generally
is lower than the cost of installing and maintaining a traditional wired
LAN, for two reasons. First, a WLAN eliminates the direct costs of cabling
and the labor associated with installing and repairing it. Second, because
WLANs simplify moves, adds, and changes, they reduce the indirect costs of
user downtime and administrative overhead.
Wireless networks can be designed to be extremely simple
or quite complex. Wireless networks can support large numbers of nodes and/or
large physical areas by adding access points to boost or extend coverage.
End-user wireless products are designed to run off the AC
or battery power from their host notebook or hand-held computer, since they
have no direct wire connectivity of their own. WLAN vendors typically employ
special design techniques to maximize the host computer's energy usage and
battery life.
The output power of wireless LAN systems is very low, much
less than that of a hand-held cellular phone. Since radio waves fade rapidly
over distance, very little exposure to RF energy is provided to those in
the area of a wireless LAN system. Wireless LANs must meet stringent government
and industry regulations for safety. No adverse health affects have ever
been attributed to wireless LANs.
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