// Network Computing Mobile Observer Weekly Newsletter
\\ Your Mobile and Wireless Resource
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// Wednesday, August 29, 2006
Network Computing's Strategic Security supplement examines the business and
technical issues that companies must consider when crafting an enterprisewide
security strategy. We cover topics including risk mitigation, policy setting and
enforcement, business continuity, customer data privacy and information access
management.
http://www.networkcomputing.com/strategicsecurity/
Look for our next Network Computing Mobile Observer newsletter on
Wednesday, September 6, 2006.
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In This Issue:
1) Wireless Propagator: A Wireless Repeater to Switch Transition? -- Part 4
2) Mobile & Wireless Commentary
3) Mobile & Wireless News, Opinion and Analysis
5) Mobile & Wireless Product Watch
5) @ NWC.COM
6) Resource Tools
7) Subscription Information
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1) Wireless Propagator: A Wireless Repeater to Switch Transition? -- Part 4
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By Frank Bulk (mailto:fbulk@nwc.com)
In my last three columns I discussed the challenges of dense wireless
deployments and some of the ways they can be addressed. In the first column, I
focused on channel design and selection. In the second column, I looked at the
poly-radio APs (access points) from Meru and Xirrus that facilitate dense
deployments by dramatically increasing the number of radios available for
clients. In the third column, I examined some non-metro Wi-Fi antenna and radio
technologies more applicable to the consumer space, with some possible
enterprise applications. In this fourth and final column, I'll touch on what
some radio and receiver vendors that target the metro Wi-Fi space are doing to
decrease deployment costs, enhance coverage and increase throughput and link
stability.
More metro Wi-Fi projects are in planning and trial phases than deployed in the
United States. But those actually in production, such as Chaska, Minn., St.
Cloud, Fla. and Mountain View, Calif., were installed with approximately 16, 20
and 33 Tropos nodes per square mile, respectively. It's important to note that
this list is ordered from the oldest to the most recent deployment. Although
it's perhaps risky to tease out a pattern from such a short list as this,
apparently cities are installing more nodes per square mile than before.
A few months ago, the Chicago Tribune wrote a story on the Chaska deployment (
http://www.duluthsuperior.com/mld/duluthsuperior/business/14976371.htm ).
According to a former member of that project, performance and coverage issues
plagued the system until more nodes were brought in to boost link stability and
fill the gaps. The node count was bumped up from 16 to almost 23 mesh nodes per
square mile. In St. Cloud, the news (
http://www.mercurynews.com/mld/mercurynews/news/breaking_news/14411895.htm )
was the lack of good indoor coverage. Mountain View may have unique terrain that
requires an even higher density, but its high watermark count of 33 nodes per
square mile may be indicative that cities have learned from past coverage and
service problems and are now designing denser deployments.
Beyond these specific examples, the generally accepted number is roughly 25
nodes per square mile to provide the necessary 95-percent outdoor 802.11
coverage and 85 percent of indoor rooms that have an outside-facing wall. With
nodes at roughly $3,000 a pop, $75,000 per square mile adds up quickly. Even if
you apply volume discounts to the mesh hardware, there's still wireless backhaul
equipment, pole rental and installation. Currently, with low penetration and
standard access rates that border sub-DSL speeds, metro Wi-Fi deployments will
be able to focus on minimum coverage requirements for quite some time. In fact,
if the link budget (that is, the difference in signal strength between what is
transmitted and what is received) can be increased, then lower densities will
likely be architected to drive down deployment costs.
Link budgets are not automatically symmetrical in nature. FCC regulations state
that access points or nodes in certain configurations are allowed to transmit at
significantly higher levels than the clients (downstream). This means that even
if the clients can interpret the transmitted signal, the nodes--even with a
well-developed receiver and good sensitivity--may not be able to demodulate the
response (upstream). Because the majority of consumer traffic is downstream,
optimizing that aspect of the link is valuable; higher link connection rates
result in a better subscriber experience and a more efficient use of the air
time, which in turn increases overall capacity. Of course, if the access point
or node can't hear the return signal, it's all for naught.
Cohda Wireless addresses the currently asymmetric nature of metro Wi-Fi
installations. One of the challenges with OFDM technology in outdoor settings is
that long distances and multiple objects introduce long delay spreads between
symbols (a discrete potion of a wireless signal). That is, one symbol may come
in 'long' after the next. Cohda uses a receiver technology that processes the
whole signal, even for delay spreads 10 times longer than normal. All this leads
to an approximately 10 dB gain in link budget. Because of its ability to deal
with long and changing delay spreads, Cohda's receiver technology also robustly
supports mobility--even if the client moves quickly and the delay spreads change
rapidly. According to Cohda, if its technology is on both ends, the metro Wi-Fi
solution should require two-thirds fewer nodes, but if it's only on the mesh
node, a more realistic proposition is about 20 percent to 25 percent fewer
nodes. A graphic on Cohda's marketing material documents one-third of the nodes
but twice the coverage in comparison to a leading enterprise wireless AP.
Go Networks also targets the metro Wi-Fi market but performs adaptive
beam-forming, the act of sending out a signal with different phase and amplitude
weightings. Although the signal may be disjointed on the transmitting side, the
client receives a coherent signal. In a similar manner, the received signal can
be more easily demodulated over multiple antennas and radios, despite the
multipath (the different paths that signals can travel because of signal
spreading and subsequent reflections). Go Networks' micro-base station uses
three 120-degree sectorized antennas. The company claims that its xRF technology
allows a 50-percent reduction in the number of nodes while still increasing link
quality, throughput and coverage.
Wavion is the last vendor. Using six radios and an equal number of
omni-directional antennas in a fixed configuration, the company also uses
beam-forming to top out at FCC-restricted EIRP levels. Wavion just released its
WS410, an outdoor AP, but the company will target the mesh market through OEM
partners. According to Wavion's chief scientist, the company's technology
delivers up to a 10 dB gain in both directions, which extends coverage as well
as raises link rates and indoor coverage. This promises lower deployment costs
because only one-third to one-fourth of the number of nodes is required for
comparable service. Future releases of the software will support SDMA (Space
Division Multiple Access), which is the ability to send multiple signals to
different users simultaneously. This, too, will increase capacity.
Although metro Wi-Fi networks remain a coverage rather than a capacity play,
these antenna and receiver technologies will lower the cost for municipal
operators to enter more towns and cities where the financial model was not that
attractive the first time around. And any developments along these lines, while
not so obviously applicable to WLAN products in the carpeted enterprise market
at this stage, can only lead to further innovations in link stability and
performance for all types of wireless connections.
Frank Bulk is a contributing editor to Network Computing Magazine covering
wireless and mobile technologies and works for a telecommunications company
based in the Midwest.
For more analysis and opinion from Frank Bulk.
http://www.networkcomputing.com/channels/wireless/
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2) Mobile & Wireless Commentary
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a) Air Time: A Wireless Education
By Dave Molta
Laptops and multipurpose cell phones are rapidly becoming the norm among
students on campus. To support all these wireless devices and technology,
however, schools must start offering serious network infrastructures rather than
a few random hotspots.
http://www.networkcomputing.com/channels/wireless/showArticle.jhtml?articleID=19
2203439
More mobile and wireless commentary can be found at:
http://www.networkcomputing.com/channels/wireless
http://www.unstrung.com
http://www.techweb.com
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3) Mobile & Wireless News, Opinion and Analysis
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a) Taking Advantage of Wide-Area Wireless
Your users are demanding mobile broadband to help them perform their jobs more
efficiently, but the complexity of deployment leaves most IT managers confused.
Here's how to take advantage of rapidly evolving and improving wide-area
wireless.
http://www.networkcomputing.com/channels/wireless/showArticle.jhtml?articleID=19
2203038
b) Motorola to Develop Mobile WiMax Chipsets
Motorola Inc. has announced a strategic initiative to develop mobile WiMax
chipsets for the company's next-generation WiMax devices.
http://www.eetimes.com/showArticle.jhtml?articleID=192400121
c) Wi-Fi Gets High
As questions continue to arise about large-scale mesh Wi-Fi deployments in big
cities, the technoscenti have begun to ask: Is there a better way?
http://www.unstrung.com/document.asp?doc_id=102402&f_src=techweb
d) First Nationwide Mobile WiMax Is Targeted for Ghana
Network deployment is underway, with initial operation to begin in the capital
city of Accra.
http://www.networkcomputing.com/channels/wireless/showArticle.jhtml?articleID=19
2300812
More mobile and wireless news.
http://www.networkcomputing.com/netnews
http://www.unstrung.com
http://www.techweb.com
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4) Mobile and Wireless Product Watch
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a) Ekahau's Site Survey 2.2
By Lee Badman
Wireless shouldn't be a guessing game, and Site Survey 2.2 provides a multitude
of answers for wireless site surveys and support.
http://www.networkcomputing.com/channels/wireless/showArticle.jhtml?articleID=19
2202550
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5) @ NWC.COM
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a) NWCReports.com--Better Than Ever
NWC Reports offers free PDF versions of all our features and select departments
so you can download individual stories as they appear in the magazine. We're
also making NWC Reports the exclusive home of our in-depth comparative reviews
and RFIs, too.
http://www.nwcreports.com
b) Remote Office Management
Join us in Boston, New York City, Chicago and San Francisco for one-day events
focused on architectural strategies to manage remove offices in today's
decentralized enterprise.
http://www.nwc.com/events/remote
c) Beyond Print: Getting Your Message Out
Join NWC's Mike DeMaria for his new podcast series dedicated to new media and
new Web technologies such as blogs, podcasts, social-networking and Web
syndication. Mike and his guests discuss how these and other mediums are
impacting the enterprise and changing business strategies.
http://www.networkcomputing.com/blog/dailyblog/archives/messaging_and_collaborat
ion/index.html
d) Submit to the Next Top 11
This week, we're looking for the Top 11 (Mis)uses for flammable/exploding laptop
batteries. Here are a few ideas to get you 'cooking':
1. Save them for the Holidays ("Chestnuts roasting on an A1061")
2. Skip the charcoal, grill some burgers over your iBook
3. Save on house heating costs this year, keep a couple of these bad boys around
http://www.networkcomputing.com/lastmile/
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6) Resource Tools
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a) Mobile and Wireless Channel
Find mobile and wireless news and commentary by our industry experts.
http://www.networkcomputing.com/channels/wireless
b) Read More Mobile and Wireless Stories on TechWeb
http://www.techweb.com/tech/mobile
c) Missed an Issue of NWC's Mobile Observer Newsletter?
Have no fear. We've created an archive of back issues for your reading
pleasure.
http://www.networkcomputing.com/mobile/index.jhtml
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7) Subscription Information
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