There are many access
point vendors now with products on the market, leaving you with a tough
decision on which one to use. Some of these access points barely satisfy the
802.11 standard, making them most suitable for homes and small offices. Others
have rich features that extend well beyond the standard, which are ideal for
higher-end, enterprise-wide solutions.
If you're deploying a small wireless LAN, then you'll likely search online
for the least expensive access point using a site like WirelessCentral.net or purchase them
at your local office supply or home electronics store. For enterprise solutions,
you need to spend some time comparing access points to make the best decision
based on requirements.
Features that seem insignificant in a smaller wireless LAN often have tremendous
payoffs in larger ones.
Selection criteria to consider
Standards. There are two primary standards for access points today:
802.11a and 802.11b. Carefully
decide on which standard to use before shopping for access points. If
you opt for 802.11a, the list of available vendors will be smaller. Not many
are offering 802.11a yet.
Interoperability. To guarantee interoperability, choose products
with WECA (Wireless Ethernet Compatibility Alliance) Wi-Fi
certification. This maximizes cross-vendor interoperability: Wi-Fi-certified
radio NICs will interface effectively with a Wi-Fi compliant access point.
Keep in mind, however, that Wi-Fi uses 802.11b as a basis. WECA is still working
on Wi-Fi5, which focuses on 802.11a product interoperability.
You should also ensure that the 802.11b access point vendor has a migration
path to 802.11a in case the future dictates needs for higher bandwidth.
Some companies solve this problem by offering dual slots in the access point
or replaceable Mini-PCI wireless NICs. Interoperability will become less
of an issue as multimode
radio NICs and access points become available, but that won't occur
until late 2002.
Upgradeability. Because wireless LAN standards are evolving rapidly,
the access point should support firmware upgrades. It's also advantageous
if the firmware upgrade can be done from a central access point, which then
automatically distributes the upgrade to the other access points on the network.
Ruggedness. If the access point will reside in an office, plastic
casing should suffice; however, warehouses and manufacturing plants will likely
require the more rugged, aluminum casing. Thus, consider the operating environment
and select an access point that is tough enough.
Regulatory. Vendors must certify access points with the appropriate
regulatory body before offering them for sale in a particular country. This
is a slow and tedious process. As a result, be sure the vendor has products
available for the applicable country, especially if you'll be deploying the
wireless LAN outside of the U.S.
Operating Temperatures. Access points don't have any problems operating
within typical office environments where temperatures are comfortable for
humans. A warehouse or manufacturing plant, however, can have temperatures
that are very hot or cold depending on the local climate. Consequently, ensure
the access point can withstand extreme temperatures if requirements call for
these types of locations.
Security. The 802.11 standard offers wired equivalent privacy (WEP)
for encrypting data sent between wireless stations. Many sources, nevertheless,
have shown the vulnerabilities of WEP. As a result, vendors offering enterprise-grade
access points generally include enhanced security features, such as IEEE
802.1X along with dynamic key allocation and management. Carefully assess
needs for security, and choose an access point having adequate security mechanisms.
Range. Access points with range enhancements are beneficial to minimize
the number and overall costs of access points. In general, longer range reduces
overall costs because of the need for fewer access points. Be careful, though,
when comparing access point specifications from different vendors. One vendor
may boast long range capability, but they may be using a higher gain antenna.
Other access points, if using this higher gain antenna, may offer the same
or better range. The idea here is to read the test specifications carefully.
Installation and Support Tools. For enterprise wireless LANs, installation
and support tools become an important aspect when choosing access points.
In general, most access points will have various methods, such as Telnet and
HTTP, for support staff to configuration and management purposes.
Be cognizant of other enhanced features that can reduce installation and
support headaches. For example, installers must choose proper radio channels
when installing multiple access points within close proximity to minimize
inter-access point interference, which can degrade the performance of a
wireless LAN. Some access point vendors make life much easier by offering
automatic channel selection. The access point senses the presence of other
access points and attempts to adjust to a quieter channel.
Transmit Power. Most access points will transmit at different power
levels, such as 30 and 100 Milliwatts. Some applications may require relatively
lower power levels, such as when deploying access points close together to
boost capacity. If you need extremely low power levels, your list of potential
access point vendors will be much smaller. Some access points will go as low
as one milliwatt, but not many do.
Antennas. Even though the antenna
is a passive device, it's a vital element of a wireless LAN. Various access
points have non-removable antennas, and some have external connectors to provide
flexibility in choosing antenna types. Those that support external antennas
provide the most flexibility, which is especially important for enterprise
solutions. Vendors generally sell different types of antennas, or you can
buy through a third party company specializing in antennas.
Price. Price obviously plays an important role when making a decision
on what products to purchase. An access point with a higher price, though,
could be the best one to choose. As a result, carefully consider the installation
and support tools that a higher priced access point may include. It could
be worth the extra money if the higher priced access point saves considerable
time when installing and supporting the wireless LAN.
Availability. Even though a vendor may have a particular access point
on the market, they may have difficulty fulfilling your order in time. This
is especially true if you're purchasing a new model. Allow some padding in
time estimates for new products, and consider availability when comparing
vendors.
You can use the above criteria to produce a list of the top several access
point vendors and possible select a preferred vendor for satisfying your requirements.
For larger projects, however, also consider evaluating several of the products
through testing before making a final decision. For example, you could install
a small prototype in a lab setting to compare and contrast security mechanisms
and performance of your top three vendors. There's nothing better than a live
comparison, but be sure to judge them equally using common test criteria.
Jim Geier provides independent consulting services to companies
developing and deploying wireless network solutions. He is the author of the
book, Wireless LANs
(SAMs, 2001), and regularly instructs workshops on wireless LANs.
He's a speaker at the 802.11 Planet Conference
& Expo in Philadelpha, June 10 - 12, 2002.
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