Wireless LAN Buyers Guide (2003)

Wireless LAN Buyers Guide
I recently went to Fry’s to buy more wireless LAN equipment for my home office. With nearly 100
SKUs to choose from, representing each version of the IEEE 802.11 standard known as Wi-Fi, I
wondered how consumers might ever make sense of it all. While I pondered my purchase, I
overheard two college kids ask a sales associate to for help. The sales rep offered some advice,
but it was clear that his knowledge was limited, so I introduced myself as a wireless consultant
and answered some of their basic questions. Our casual discussion evolved into a 20-minute
WLAN course that attracted about a dozen onlookers who also bought wireless products. The
father of one young man thanked me for condensing so much information into such a timeframe,
and that fun experience convinced me to write this article and explain the tradeoffs that can help
you make your own WLAN decisions.

If you plan to jump on the Wi-Fi bandwagon, you must choose among several 802.11 standards
that are evolving at a fast rate and have different features and benefits. The table below gives a
quick overview of the tradeoffs, which can change over time. The rest of this article adds detail
for each standard and each decision criteria so you can get maximum value from your purchase.

TRADEOFFS 802.11b 802.11g 802.11a Dual Band
Frequency Band 2.4 GHz 2.4 GHz 5 GHz 2.4 & 5 GHz
1 1
Spectrum Allocation 83.5 MHz 83.5 MHz 300 MHz 300 + 82.5 MHz
2
Rated Speed 11 Mbps 54 Mbps 54 Mbps 54 Mbps
3
Actual Throughput 4.5 Mbps 7-16 Mbps 54 / 27 54 / 27
Range (typical maximum) 1500' 200' 1500' 1500'
Reliability (RF Interference) usually OK usually OK much better best
# of Available RF Channels 4 4
11 (3) 11 (3) 12 (8) 11 (3) + 12 (8)
(Non-overlapping Channels)
48-, 64-, 128- 48-, 64-, 128- 48-, 64-, 128-, 48-, 64-, 128-,
Security (encryption)
bit WEP bit WEP 152-bit WEP 152-bit WEP
Size / Form Factor smallest smaller smaller small
Battery Life best better often OK often OK
Compatibility good better OK & improving best
Quality of Service none none none none
Ease of Purchase, Setup, varies by varies by varies by varies by
5
Use, Upgrade vendor, appl. vendor, appl. vendor, appl. vendor, appl.
Investment Protection shortest long long longest
Vendor Brand / Asthetics personal personal personal personal
6
Street Price
$29/49 $39/$69 $49/$79 $69/$99
(Access Point / NIC)

NOTES:
1 - Recent U.N. conference expands allocation to 455 MHz worldwide
2 - proprietary turbo modes can double speed to 22 Mbps and 108 Mbps
3 - throughput decreases with distance as signal strength weakens
4 - U.N. conference expands this to 24 channels in U.S. and 19 in Europe
5 - varies greatly by vendor and application (e.g. SOHO vs. enterprise)
6 - estimated retail price after rebate, as of July 2003

Wireless LAN Buyers Guide.doc Copyright (©) CAZITech Consulting, 2003

Introduction
Because wireless LANs eliminate Ethernet wiring and add mobility, Wi-Fi networks have
exploded into over 11 million U.S. households, according to Gartner Group. Most allow PC users
to share a high-speed Internet connection, but Wi-Fi also lets them roam about, moving either
from one room to another in the home, or between the home and the office or public hotspot.

Wi-Fi service providers (WISPs) are busy extending broadband Internet access to hotels and
conference facilities, airline terminals, coffee shops, and your local McDonalds. Even the
ubiquitous pay phone could become an access point, giving you wireless access to DSL
connections.

European research firm, ARCChart, predicts there will be over 91,000 of these public hotspots
worldwide by the end of 2003 and 203,000 by the end of 2007. And just as with cellular phone
networks, WISPs are forming roaming agreements with each other.

The Tradeoffs
As prices fall and the price difference between products using different standards shrinks, price
becomes a less important decision criterion. Because it’s more important to focus on Value and
consider other buying criteria, I will discuss Price as the last of the tradeoffs.

Frequency Band
WLAN products operate in license-free frequency bands at 2.4 GHz or 5 GHz, or a combination
of the two. The choice of band is a tradeoff that can affect price, performance, range, and
reliability, so consider your application requirements and operating environment.

2.4 GHz – The 802.11b and .11g standards use 2.4 GHz, a band that is available worldwide
without a license, so products based on these standards are naturally less expensive and more
pervasive. If you roam about – between homes, offices, and hotspots, or between countries –
then you may prefer the ubiquity of 2.4 GHz., which also covers longer distances. But 2.4 GHz is
prone to RF interference that can slow, or even shut down, a wireless network.

5 GHz – The 802.11a standard uses 5 GHz, a band that has more spectrum available for higher
performance and is also cleaner with less RF interference. But operating in the 5 GHz band can
result in slightly larger and more complex silicon chips, somewhat higher costs, and decreased
battery life. So far, products based on this standard are not as pervasive, but this could change
as prices fall. If you want to run demanding multimedia applications such as HDTV video
streaming, or if you live and work in an environment where RF interference is an issue, then
consider 5 GHz.

Multi-mode – Can’t decide? Why not pay a bit more and buy multi-mode products that operate in
either frequency band and can automatically sense and adapt to whatever network is available.
That’s the future, and early products are available today, although at premium prices.

Spectrum Allocation
Regulatory bodies like the FCC allocate radio spectrum (bandwidth) to each type of application,
including the unlicensed 2.4 GHz and 5 GHz bands. Since there’s more bandwidth available at 5
GHz, it’s possible to build faster networks in that band.

2.4 GHz – 802.11b and .11g are allocated 83.5 MHz of radio spectrum, and this same spectrum
is available worldwide. That means companies can make products for global markets, thus
driving volumes up and prices down.


5 GHz – 802.11a has been allocated more spectrum, with 300 MHz available in the U.S. That’s
why it’s faster, and products using this standard can support HDTV video streaming. Actual
allocation varies, however, between countries. Since manufacturers currently need different
versions of their 802.11a products for different markets, prices are generally higher. Thankfully,
delegates at a recent World Radio Communication Conference, which was hosted in June by the
U.N., agreed to standardize on spectrum allocation at 5 GHz and increase it to 455 MHz. Once
ratified by their respective countries, this will help improve performance and sales volumes,
driving prices down.

Rated Speed
Since manufacturers advertise maximum rated speed, most people rely on this as their primary
comparison, but it can be misleading. Actual throughput depends on other factors, as described
in the next section.

802.11b – 11 Mbps is the rated speed of the most popular and mature version of 802.11, which
uses DSSS (direct sequence spread spectrum) technology. Some vendors also offer a turbo
mode that substitutes PBCC modulation to double that performance to 22 Mbps, but to use these
proprietary extensions, you should get all of your network gear from the same manufacturer.

802.11g – 54 Mbps is the rated speed of this newer and backward-compatible version of 802.11.
To increase performance, .11g uses OFDM (orthogonal frequency division multiplexing)
technology instead of DSSS.

802.11a – 54 Mbps is the current rated speed, but more should be possible with pending
increases in 5 GHz spectrum allocation. Some vendors also offer a turbo mode that uses more
RF channels (more bandwidth) to increase performance to 108 Mbps.

Throughput
Because networks have overhead related to software and media access control (MAC), actual
throughput is always less than rated speed, and that’s what is important to your applications. A
general rule-of-thumb is that throughput is half of rated speed, even with wired Ethernet, but this
depends on the amount of overhead imposed.

802.11b – Even though the rated speed is 11 Mbps, actual throughput is more like 4.5 Mbps.

802.11g – Rated speed is 54 Mbps, but the relatively high overhead of OFDM lowers the
maximum throughput to 7-16 Mbps. The slower 7 Mbps speed is due to backwards compatibility
features and results when mixing 802.11b and 802.11g devices in the same network.

802.11a – Because there is more bandwidth (more channels) available at 5 GHz, 802.11a can
achieve a higher maximum throughput of about 27 Mbps, from its 54 Mbps rated speed.

Distance – In all cases, throughput diminishes with distance and barriers such as walls that
impact signal strength. When pushing their 802.11b products, vendors often cite the longer range
of 2.4 GHz products as an advantage over .11a, but remember that .11a starts out faster, so you
may still get faster performance throughout your house with .11a.

How much throughput do you need? It depends on your application, and all versions of 802.11
can handle simple needs, including email, printer sharing, Internet access, and even streaming of
audio and compressed video. If you want to stream HDTV programs, however, your only choice
is 802.11a due to the need for 20 Mbps of throughput. To find out more, refer to my HomeToys
article, “Bandwidth: How Much is Needed, and How Much is it Worth?”


Range
The same laws of physics affect radio signals and sound, where loudness (signal strength)
diminishes with distance and when going through materials like windows and walls. As with
sound, radio signals using lower frequencies (2.4 GHz vs. 5 GHz) have less attenuation problems
(signal loss) with distance. Likewise, higher frequencies are more able to punch through noisy
environments (RF interference).

For sound, this explains why foghorns on ships use low frequencies so they are heard over long
distances. And when you pull up next to a teen’s car at a stoplight, you may only hear the bass
from his sub-woofer. As it turns out, car horns include both a high and low sound – one for
country driving (long distance) and one for city (punch through traffic noise).

For radio, this explains why the comparison grid shows longer range for products using 2.4 GHz.
Note, however, that there are various ways to extend range. The most obvious way is to use
more power (shout louder), but regulators limit the amount of transmit power that can used.
Other ways to extend range include using more sensitive receivers and high-gain antennas (like
hearing aids with the power turned up), directional antennas (like a cheerleader’s megaphone),
steerable antennas, repeaters, and mess networks.

For more information on this concept, refer to my HomeToys article on “Wireless in 2003: CES
Shows Consumers the Way.”

Reliability (RF Interference)
802.11 standards all use digital spread-spectrum technologies to help handle RF interference, but
this problem is more severe and difficult to resolve in the crowded 2.4 GHz band, and it can slow
down a wireless network or shut it down entirely. That’s because so many neighboring devices
use the same 2.4 GHz band, including nearby WLANs, Bluetooth devices, microwave ovens,
some baby monitors, 2.4 GHz cordless phones, and even energy-saving bulbs in stadium lights.
Because radio signals can pass through walls, this interference can come from outside and make
related network problems difficult to identify.

As the WLAN market grows, along with Bluetooth and multi-handset cordless phone markets, RF
interference between neighboring apartments, homes, and business offices will become a bigger
problem and unavoidable with 802.11b or .11g, which each have only three non-overlapping
channels. But as long as you get adequate throughput and the network density in and around
your building is not expected to change, 802.11b (or .11g) can be a reliable solution

Over time, however, the market will shift to 802.11a and multi-mode solutions. That’s because
802.11a is faster, uses the less crowded 5 GHz band, and has more RF channels to choose from
(currently 12 in the U.S. and expected to increase to 24), thus making it easier to avoid
interference entirely.

Available RF Channels (Non-overlapping Channels)
Available spectrum for wireless networks is divided into
different frequency channels, which are set in the access
point. Wi-Fi cards then locate the access point with the
strongest signal and tune their transceiver to that frequency.

The cards periodically scan and reattach, allowing them to
change channels as they roam about between access
points. To minimize RF interference, network administrators
set nearby access points to different channels. Both
802.11b and .11g lets them choose between three non-
overlapping channels so they can setup a mini cellular-style


network as shown in the illustration.

Channels can be reused when they are far enough apart, but it takes quite a bit of wireless
networking skill to determine the number of access points needed, the distance they should be
from each other, and the channels that should be assigned. As a PC user, you shouldn’t have to
worry about this unless you live in an apartment or home with nearby neighbors that have their
own Wi-Fi network.

If you have many neighbors, including ones who live above or below you, you may run out of
channels with just three to choose from, and that would be a good reason to choose 802.11a
since it offers 8 non-overlapping channels in the U.S. today, with even more planned for the near
future. If neighbors aren’t an issue, then don’t worry about this.

Security (encryption)
Securing wireless networks is difficult since signals go through walls, and most solutions are way
too complex for consumers, so they aren’t used. Each 802.11 standard includes a basic
encryption algorithm called WEP (wired equivalent privacy), but it was never part of the product
certification process, so most products ship with WEP turned off. That way, consumers don’t
need to choose an encryption key, it’s easier for them to roam into public hotspots, and the added
encryption overhead doesn’t slow performance.

For most consumers, basic WEP security is adequate, but you must first turn it on, and it’s
surprising how many people have never done that. You can increase security beyond basic WEP
by choosing a longer encryption key, but for home use, that may not be necessary for two
reasons. (1) The information stored there is less valuable to hackers. (2) And the amount of
network traffic is much less, so it takes longer to accumulate data enough to break WEP
encryption.

For business use, however, WEP is widely criticized as not being secure enough since it’s too
easy to break. 802.11b defines a 48-bit encryption key, and many manufacturers also support
64- and 128-bit keys. The 802.11a standard goes farther by defining an optional 152-bit key
that’s harder to break, and standards groups are working on even more exotic solutions. But
since the participants come from large enterprises, the solutions are enterprise-centric, and
neither consumers nor small businesses have the network administration skills or the
authentication servers required to take advantage of these emerging security standards.

Size / Form Factor
Semiconductors keep getting smaller, which is good since size and weight are especially
important to the success of portable devices, especially handhelds. But sometimes to get into a
small size, you must give up other things, like larger batteries and antennas. So, there’s a
tradeoff.

Products using all popular 802.11 standards are available in the PC Card format for notebook
PCs and handhelds, but only 802.11b products are available in the smaller Compact Flash,
Secure Digital, and Sony Memory Stick formats. If you want your handheld to have WLAN
access, your only choice may be 802.11b. Eventually, we’ll see .11a, .11g, and multi-mode
products available in these smaller form factors too.

Battery Life
Since portable devices use battery power and are useless when the battery dies, designers must
either manage battery life or provide easy ways to recharge. Of the WLAN choices, 802.11b
consumes the least amount of battery power, followed by .11g (because of OFDM), .11a
(because of OFDM and 5 GHz), and multi-mode.


How important is battery life to you and your applications? If you primarily use a notebook PC to
move between different locations and plug in when you get there, it’s not an issue. And other
factors, besides which version of 802.11 you use, can improve battery life. You can reduce the
brightness of your backlit display or change system settings to shut down the disk or cycle back
the clock rate during periods of inactivity. Intel’s new Pentium M processor, which is part of its
Centrino chipset, also contributes to longer battery life.

Compatibility (including Roaming)
Compatibility is not an issue when you buy the same type of network gear from one vendor for
use in your home, but it can be a big issue if you use the same PC in your corporate offices or
while traveling. That’s when you must know that your products are Wi-Fi certified to work with
similar products in the same 2.4 GHz or 5 GHz band.

To make sure that the Wi-Fi products you buy are compatible with those you may
find elsewhere in your travels, look for the Wi-Fi compatibility mark but know that
it doesn’t distinguish between 802.11b, .11g, or .11a, so pay close attention to
what’s printed on the box.

Your employer might be using 802.11a because of its faster performance, ability to support more
users, and easier network administration, but most of the public hotspots only support 802.11b.
And you might think of choosing 802.11g at home for faster performance and backward
compatibility with .11b, but consider multi-mode as a way to get the best of all three standards.
Since both 802.11a and .11g use OFDM, products with multi-mode radios can easily support both
standards.

Quality of Service (QoS)
Quality of Service is not usually an issue for data applications such as email, printing, and Web
browsing, since short delays are seldom noticed. It’s critical, however, when transmitting time
sensitive information such as voice, audio, and video.

Acceptable performance with those applications requires that data packets arrive on time, and
QoS is a measure of how well that is accomplished. QoS is influenced by bandwidth, latency,
jitter, and packet error rate.

• Bandwidth available for one application can suffer with network congestion other applications
that consume bandwidth. Without a way to prioritize traffic, downloading large files can
consume so much capacity that there’s not be enough left for video streaming.

• Latency is the amount of time between when a packet is sent and received, and delays can
be noticed in wireless voice conversations using voice over IP (VoIP).

• Jitter is the perceived distortion that results when packets arrive out of sequence or with
delays, and it is particularly damaging to multimedia traffic.

• Packet Errors are common with RF interference and multi-path reflections, and mechanisms
to reduce the packet error rate include automatic error correction and packet retry, but this
can cause delays that are noticeable in multimedia applications.

Since Wi-Fi is essentially wireless Ethernet and lacks standards for QoS, some vendors have
added their own proprietary QoS technology. The IEEE has started work on a standards-based
QoS solution called 802.11e that will eventually make it easier for Wi-Fi to support multimedia
applications, even when faced with the challenges mentioned above. I expect 802.11e to be
ratified by the end the year. It will take many years, however, for its effect to be felt in the market,
since all devices on the network must obey the QoS rules, and if older products don’t, then they
destroy QoS benefits for all others.


Ease of Purchase, Setup, Use, and Upgrade
Beyond the early adopters, most
consumers need products that are easy
to buy, install and use, and some
vendors do a better job with these
issues than others. Microsoft, for
example, makes it easy to buy a Wi-Fi
network by bundling the networking
components into a kit. Shown here is
one that includes an access point and
USB adapter for desktop PCs.

Linksys, which is also known for easy
setup and use, is partnering with Intel to improve that process even more. Future
PCs with Intel’s Centrino chip will more easily find Linksys access points, and they
plan to introduce a “Verified with Intel Centrino Mobile Technology” certification
mark, which promises even more than the Wi-Fi mark.

Please don’t treat these product mentions as endorsements since many other vendors offer Wi-Fi
products designed for consumer markets, with easy setup and use. Possibly a more important
characteristic is the ability to apply firmware upgrades to take advantage of future enhancements
to security (coming in 802.11i), QoS (in 802.11e), power management (in 802.11h), and other
enhancements to the standards. Usually a product’s upgrade abilities is described on the box.

Investment Protection
By selecting products that meet both your current and future needs, or that can be enhanced to
support them, you help extend the life of your investment, so don’t just focus on purchase price.

802.11b is the most popular, most mature, and least expensive wireless standard today, so
companies making products based on newer standards bend over backwards to ensure
compatibility with that large installed base. By the end of 2004, however, you may not even be
able to buy 802.11b products since the newer ones will support .11g, which is backwards
compatible, or multi-mode, for both 2.4 GHz and 5 GHz operation. I can make that prediction
with confidence because of what happened with Ethernet. Even the cheapest Ethernet products
support both 10 and 100 Mbps, and the newest ones are described as 10/100/1000baseT,
scaling automatically from 10 Mbps to 1 Gbps. It’s hard to even find a 10baseT product to buy.

Vendor Brand / Aesthetics
You might be more comfortable with one trusted brand over another, maybe
because of previous experience with wired network products, and that’s OK
since it’s such a personal choice. Or you might be attracted to one vendor’s
products because you like their design aesthetics. That’s OK too and just
another tradeoff.

Street Price
You can already get a complete WLAN kit with NIC (network interface card) and AP (access
point) for less than $100, and the street prices are falling fast, especially after rebates are applied.
With prices this low, there should be no reason to wait, but you may still want to shop around for
the best deal. Consider the tradeoffs discussed in this article, however, because the best deal is
not necessarily the lowest price. The Tradeoffs grid at the beginning of this article listed some
estimated street prices at the time I am writing this, but you may be able to do much better.


What did I end up buying on my trip to Fry’s?
Because I live in a 3,000 square foot home in an Austin, Texas neighborhood with small lots and
many technologists living nearby, I was concerned with RF interference at 2.4 GHz. There was a
good chance that they may have their own WLAN or 2.4 GHz cordless phone system, if not now
then sometime later on. So, I specifically looked for 802.11a for its faster speed and its ability to
avoid potential interference problems. Instead, I found some dual-band products at a great price
after rebate, and I found that they weren’t much more expensive than the older 802.11 products.

Here’s what I bought:

• Netgear WAB102 Dual-band Wireless Access Point ($129.90 - $50 rebate = $79.90)

• Netgear WAB501 802.11 a/b Dual-band Wireless PC Card ($79.90 - $50 rebate = $29.90)

I’ve been quite happy with my purchase. Setup was easy, and I made sure to enable WEP
security. Rather than specify a specific frequency, I let the products determine whether it’s best
to run at 2.4 GHz or 5 GHz, and I let them operate in turbo mode.

I positioned the access point high on a shelf in the home office, which is at the top of the spiral
staircase in the middle of the house. PCs in the home office are connected with cat.5 cabling and
Ethernet 100baseT. The Netgear Wireless PC Card went into an extra notebook, which I can
now use anywhere in and around the house – in the living room or family room downstairs, in the
master bedroom upstairs, or outside on the deck when the sun isn’t so bright that it washes out
the screen. In my worst-case scenario, radio signals only have to travel through one floor and
one wall with the longest distance being less than 100 feet.

Signal strength has been consistent at about 60% throughout the house, and this gives me about
72 Mbps of transmit performance and 12 Mbps of receive performance. I have had no problems
opening my largest PowerPoint presentations (over 30 MB) or streaming video, and I’ve noticed
no network degradation due to interference, even with my 2.4 GHz Siemens Gigaset phone and
Motorola SimpleFi wireless digital audio receiver, which uses the HomeRF standard at 2.4 GHz.

So to summarize, shop around and compare prices but focus on value and consider other
tradeoffs too. You may even want to take this article with you, and potentially share it with the
sales rep.


Wireless LAN Buyers Guide (2003)

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