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Wireless LANs
Wireless LANs
An
introduction to wireless networking hardware
October 30, 2001
Author:
Using the
Internet Guide (Communication and Collaboration):
Eric Leland |
Wireless networking products have become more popular in the
last few years due to an increase in competition among
manufacturers and the emergence of a more dominant wireless
technology standard. This report looks at the benefits and
drawbacks of wireless networking and provides further resources
for research into wireless products.
Definition: Wireless Networking
Wireless networking refers to hardware and software combinations
that enable two or more appliances to share data with each other
without direct cable connections. Thus, in its widest sense,
wireless networking includes cell and satellite phones, pagers,
two-way radios, wireless LANs and modems, and Global Positioning
Systems (GPS).
Definition: Wireless LAN
Wireless LANs enable client computers and the server to
communicate with one another without direct cable connections.
Generally, a wireless LAN is connected to an existing wired LAN,
although they can exist without a wired LAN (in this case, users
will only be able to communicate with other users on the same
subnet).
Components of a Wireless LAN
Necessary components include an Access Point, Client LAN
adaptors and the wired LAN. The Access Point is a device that
translates between the wired LAN and the wireless LAN. The
Client LAN Adaptors are PC cards, PCI or ISA boards that plug
into laptop or desktop computers equipped with radio
transceivers to communicate with the Access point. Other
components to a wireless LAN can include Extension Points and
Directional Antennas. Extension Points are devices similar to
the Access Point, but not connected to the wired LAN. Extension
points serve to extend the range of the wireless network by
relaying signals from client computers to the Access point.
Directional Antennas serve to connect wireless networks located
at a greater distance from one another. Each network would have
an antenna targeted at each other (known as a "line of site"
connection).
Technology Standards
Manufacturers have adopted many competing standards for
implementing wireless communication. Interoperability between
different communications standards is currently not available.
It is important to evaluate, with any wireless LAN networking
system, the technology it uses, the features it provides and the
industry support it has. Below are common standards available:
| Standard |
Coverage |
Speed |
Access Point |
Network Card |
| 802.11b |
150 feet |
11Mbps |
$200 |
$100 |
| 802.11a |
50 feet |
50Mbps |
$300 |
$200 |
| Bluetooth |
30 feet |
1Mbps |
N/A |
$50 |
| UWB (no consumer products yet) |
100 feet |
40-1000Mbps |
$100 |
$100 |
| HomeRF |
150 feet |
1.6-10Mbps |
$200 |
$100 |
- IEEE 802.11b is sometimes referred to as "Wi-Fi".
Currently this open standard, developed by the Wireless Local
Area Networks Standards Working Group, is the most widely used
wireless LAN system. Large technology companies such as
Linksys, Apple, SMC, and 3Com have adopted it for their
product lines. This technology uses radio waves in the 2.4-GHz
frequency band (same as many other appliances such as cordless
phones and microwaves) and has the potential for interference.
Speed ranges from 1-11Mbps (newer products are most often
specified at 11Mbps).
- IEEE 802.11a is a standard that many believe will
replace 802.11b in five years - vendors are scheduling its
release in 2002, but widespread adoption will come some years
later. Speed can reach 54 Mbps and travels on the less
congested 5GHz band, reducing the potential for interference.
Range is limited to 50 feet. More speed but likely more Access
Points required. Some vendors are producing Access Points that
will adapt to both the 11b and 11a standards as well as other
standards (Enterasys Networks, Proxim and Agere are examples).
- Bluetooth is an inexpensive, very low-powered and
short-range frequency-hopping radio system that would link
your pagers, personal access devices, cell phones, and laptops
(designed for small, mobile devices). The potential for
interference (shares 2.4 GHz frequency), particularly to the
low-powered Bluetooth, remains an open problem. Range is only
30 feet but line of sight is not necessary - the distance
limitation is a problem for serious LAN implementation, and
not many Bluetooth LAN systems have been developed as a
result. Named after the 10 centuryDanish King Harald,
"Bluetooth" is the English translation of his last name "Blatand."
King Harald was famous for uniting the kingdoms of Denmark and
Norway and for his extensive travels; like King Harald,
Bluetooth unites separate entities (peripherals, laptops,
PDAs, Cellphones, cameras, etc).
- Ultra Wide Bandwidth is an emerging technology that
promises much higher bandwidth speeds at low costs. Inventor
Larry Fullerton created UWB transmission as a radically
different approach to data transmission. Instead of data being
transferred within a given frequency (such as radio stations,
who have one frequency on which to broadcast), UWB broadcasts
its signal across the spectrum, using different patterns and
combinations, avoiding the whole signal switching process that
confines signals to certain frequencies. What about all those
radio stations, will UWB interfere? Fortunately, the UWB
signal is detected as noise by most radio receivers and is
easily filtered out, although there is discussion among
sectors that rely on low powered radio signals as to UWB's
potential for interference.
The speed of the transmission depends on the center of the
spectrum on which the signal is transmitted. Plans are to
initially roll out products at speeds of 40Mbps in 2002 (the
PulseON chip developed by Time Domain of Alabama), then as the
hardware size can be reduced in manufacturing, increasing this
to 1GHz or more. Look for cheaper and faster wireless
networking products over the next year!
- HomeRF provides four high-quality voice
transmission channels as well as a 1- to 5-Mbps data
transmission channel. Designed more for the home network as it
includes support for telephony together with data, lower costs
and supports shorter range signals. Pushed by Intel but not an
open standard, and speed is less than 802.11b (1.6 Mbps). Just
released as of this writing is the new improved HomeRF that
promises up to 10 Mbps. See
http://www.homerf.org for more details.
How a Wireless LAN works
In a typical wireless LAN configuration, the Access Point
connects to the wired network from a fixed location using
standard cabling. The access point receives and transmits data
between the wireless LAN and the wired network infrastructure. A
single access point can support a small group of users and can
function within a range of less than one hundred to several
hundred feet. End users access the wireless LAN through the
wireless-LAN adapters installed in their computers.
Benefits of Wireless LANs
Cost: Wireless LANs can cost less to implement than wired
LANs, especially in situations where implementing a wired LAN
requires extensive labor and materials to install the wiring and
drops. For environments that are difficult to wire (such as
schools or temporary spaces) a wireless network can be more
cost-effective in the long run than a wired one.
Simple/flexible to Install: Wireless LANs eliminate the
time needed with wired LANs for laying and pulling wires, and
can reach places that cannot be reached by wires.
Portability: Wireless LAN systems can move physical
locations much easier than wired LANs, reducing total cost of
ownership for organizations that are on the move.
Mobility: Wireless LAN systems can provide LAN users with
access to network information anywhere in their organization.
Scalability: Wireless LAN systems can be configured for
small offices and large, with peer-to-peer systems or large
established LANs, specific to the localized need of a workgroup
or across the whole enterprise. Wireless LAN systems grow easily
with the need by adding more access points, client LAN adaptors
and extension points. Wireless can be a good solution if you
need to connect several buildings without installing a wired
connection. Wireless LAN bridges can extend LANs that are
typically one to five miles apart. These wireless bridges span
multiple-building LANs without incurring the monthly costs of a
T1 or higher speed lines.
Drawbacks of Wireless LANs
Cost: In environments with installed wiring or less
demanding wiring needs, the up front costs of adopting a
wireless LAN system can be more expensive than with wired LANs.
Interoperability: There are several competing
technologies used by wireless LAN vendors to communicate data
between hardware, with no ability for communication directly
between systems using these different standards.
Interference: Most of the wireless devices today operate
on 2.4-GHz radio bands, which are also used by cordless phones
and most microwave ovens. The potential for interference when
used near other devices sharing the same frequency band.
Speed: Most commonly used wireless LAN products are rated
for a maximum 11Mbps throughput, and in practice see speeds
about 80% less than this - some wireless LAN products are rated
for speeds much less than this (HomeRF systems for example).
Still quite speedy for most network needs and for broadband
Internet sharing, but for larger offices with high network
traffic and demands for speed, this should be taken into
consideration.
Wireless LAN Products
Simple wireless LAN systems provide an Access Point that is
plug-and-play when connected to an existing wired network. They
may or may not include client LAN adaptors. More advanced
solutions function as stand-alone networking systems that often
provide cable/dsl router, switch, DHCP and firewall technology
together with an Access Point. As of this report, prices for
Access Points range from $250 to $1500 each, and client LAN
adaptors cost from $80-$200 each. When networking Macintosh
systems, it is important to consider whether the product comes
with macintosh drivers for the Access Point and the client LAN
adaptors, and if there is a Macintosh version of the supporting
administration software. If you've decided that a wireless LAN
is the right networking solution for your organization, here are
a few products that we recommend...
For the small office, D-link offers a wireless Access Point
using the 802.11b specification plus two USB client LAN adaptors
for $500 (kit with two PC cards for laptops costs $450). This
unit has DHCP built in and can be used with or without an
existing wired network. D-Link also offers an inexpensive stand
alone Access Point (DI-713) for $200. PC only. See
http://www.dlink.com for more
details.
For larger systems, Orinoco AP-1000 offers a wireless Access
Point with an array of features, including the ability to
upgrade radio technology by swapping in new PC cards - thus if
Orinoco decides to adopt a new radio standard, the Access Point
can still be used. Also has load balancing, support for voice
transmission, uses 802.11b standard, supports wired and fully
wireless setups and more. Access Point costs around $900 and
each client LAN adaptor costs around $150. Mac and PC. See
http://wavelan.com/template.html?section=m58&page=103&envelope=94
for more details.
Apple Airport offers a wireless solution geared primarily toward
Macintosh networks comparable to the D-link option ($300 for
each access point, $100 for each LAN adaptor). One unique
feature of the Airport is that HP makes a device capable of
wirelessly sharing printers with the Airport Access Point
($300). Thus the printer does not have to be connected via wires
to a server computer. Check out
http://www.apple.com/airport/specs.html for information on
the Airport.
Further Resources
Comparison of Several Wireless LAN Products (May 2001)
http://www.pcworld.com/reviews/article/0,aid,50415,pg,8,00.asp
Reviews of Wireless LAN products (Feb 2001)
http://www.zdnet.com/products/stories/reviews/0,4161,2685770,00.html
Apple Airport Access Point (popular Mac wireless networking
product)
http://www.apple.com/airport/specs.html
TechRepublic: Wireless LAN Articles and discussion
http://www.techrepublic.com/article.jhtml?src=search&id=r00720010330bla01.htm
Good introduction on how wireless LANs function and their
benefits
http://www.wirelesslan.com
Gartner Wireless LAN whitepaper (January 2001)
http://www.techrepublic.com/download_item.jhtml?id=dr00620000616ang13.htm
Gartner Bluetooth whitepaper (August 2000)
http://www.techrepublic.com/download_item.jhtml?src=search&id=dr00520000817ggr01.htm
HomeRF Standard Homepage
http://www.homerf.org/
Universal Client Wireless LAN Adaptors
http://www.breakfree-technologies.com/images/aironet/uc4845.pdf
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