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<DIV><FONT face=Arial size=2>some new self-organizing technology
forms!!</FONT></DIV>
<DIV><FONT face=Arial size=2>this came viaPlexus Institue - Harrison - I believe
you made contact with them at one point?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Meg Salter</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>MegaSpace Consulting<BR>(416) 486-6660<BR><A
href="mailto:meg@megsalter.com">meg@megsalter.com</A><BR></FONT><BR></DIV>
<DIV class=Section1>
<DIV align=center>
<TABLE class=MsoNormalTable
style="mso-cellspacing: 0in; mso-padding-alt: 0in 0in 0in 0in" cellSpacing=0
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<TBODY>
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<TD
style="PADDING-RIGHT: 0in; PADDING-LEFT: 0in; PADDING-BOTTOM: 0in; WIDTH: 469.15pt; PADDING-TOP: 0in"
width=626>
<P class=MsoNormal><FONT face=Arial size=3><SPAN
style="FONT-SIZE: 12pt; mso-bidi-font-family: Arial">Can't read your
Plexus TCP? Click </SPAN><SPAN class=MsoHyperlink><FONT face=Arial
color=blue><SPAN style="mso-bidi-font-family: 'Times New Roman'"><A
href="http://www.plexusinstitute.org/TCP/110903.txt"
font="airal">here</A></SPAN></FONT></SPAN></FONT><SPAN
style="mso-bidi-font-family: Arial"> to view
instead.<U1:P></U1:P><o:p></o:p></SPAN></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P></TD></TR>
<TR style="mso-yfti-irow: 1">
<TD
style="PADDING-RIGHT: 0in; PADDING-LEFT: 0in; BACKGROUND: white; PADDING-BOTTOM: 0in; WIDTH: 469.15pt; PADDING-TOP: 0in"
vAlign=top width=626 bgColor=white>
<P class=MsoNormal
style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial size=3><SPAN style="FONT-SIZE: 12pt"><IMG id=_x0000_i1025
height=55 src="cid:008f01c37b27$20cdb900$1702a8c0@orionsecurities.ca"
width=350 border=0></SPAN></FONT></P></TD></TR>
<TR style="HEIGHT: 0.75in; mso-yfti-irow: 2" height=72>
<TD
style="PADDING-RIGHT: 0in; PADDING-LEFT: 0in; PADDING-BOTTOM: 0in; WIDTH: 469.15pt; PADDING-TOP: 0in; HEIGHT: 0.75in"
vAlign=bottom width=626 height=72>
<H3><B style="mso-bidi-font-weight: normal"><FONT face=Arial color=#085299
size=5><SPAN style="FONT-SIZE: 20pt"><SPAN
style="mso-bidi-font-size: 13.5pt">Thursday Complexity
Post</SPAN></SPAN></FONT></B></H3></TD></TR>
<TR style="mso-yfti-irow: 3">
<TD
style="PADDING-RIGHT: 0in; PADDING-LEFT: 0in; PADDING-BOTTOM: 0in; WIDTH: 469.15pt; PADDING-TOP: 0in"
width=626>
<H2><CSOBJ region="0" format="LongDate" locale="00000409" t="DateTime"
h="16" w="284"><!--[if supportFields]><span
style='mso-element:field-begin'></span><span
style='mso-spacerun:yes'> </span>DATE \@ "MMMM d, yyyy" <span
style='mso-element:field-separator'></span><![endif]--><SPAN
style="mso-no-proof: yes">September 11, 2003</SPAN><!--[if supportFields]><span
style='mso-element:field-end'></span><![endif]--></H2></TD></TR>
<TR style="HEIGHT: 1in; mso-yfti-irow: 4" height=96>
<TD
style="PADDING-RIGHT: 0in; PADDING-LEFT: 0in; PADDING-BOTTOM: 0in; WIDTH: 469.15pt; PADDING-TOP: 0in; HEIGHT: 1in"
width=626 height=96>
<H2><B style="mso-bidi-font-weight: normal"><FONT face=Arial color=#085299
size=5><SPAN style="FONT-SIZE: 17pt">Wireless Networking Hits
</SPAN></FONT></B><st1:City><st1:place>Boston</st1:place></st1:City>
Rooftops</H2></TD></TR>
<TR style="mso-yfti-irow: 5">
<TD
style="PADDING-RIGHT: 0in; PADDING-LEFT: 0in; PADDING-BOTTOM: 0in; WIDTH: 469.15pt; PADDING-TOP: 0in"
vAlign=bottom width=626>
<P
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><U1:P></U1:P><U1:P></U1:P><U1:P></U1:P><FONT
face=Arial size=3><SPAN
style="FONT-SIZE: 12pt; mso-bidi-font-family: Arial">This week’s TCP
features a piece that can be viewed on-line from MIT’s <I
style="mso-bidi-font-style: normal"><SPAN
style="FONT-STYLE: italic; mso-bidi-font-style: normal">Technology
Review</SPAN></I>.<SPAN style="mso-spacerun: yes"> </SPAN>Special
thanks go to Jeff Johnston for pointing out this
article.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><FONT face=Arial
size=3><SPAN style="FONT-SIZE: 12pt; mso-bidi-font-family: Arial">The
piece addresses some rather interesting new attempts to connect people
wirelessly with one another to an internet gateway through a collection of
rooftop antennae.<SPAN style="mso-spacerun: yes"> </SPAN>The
project, called <SPAN class=SpellE>Roofnet</SPAN>, is an unmanaged group
of computers running Linux and a <SPAN class=SpellE>Wi-Fi</SPAN> card,
which self-organizes itself.<SPAN style="mso-spacerun: yes">
</SPAN>It is a self-configuring collection of computers that functions
more efficiently for data packets to move around, hopping from rooftop to
rooftop. The overall topology of the wireless network is constantly
changing, but functions in a way that allows a data packet to find its way
from one node in the network to the next, constantly re-evaluating old and
new links, in more effective ways than other types of
networks.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><FONT face=Arial
size=3><SPAN style="FONT-SIZE: 12pt; mso-bidi-font-family: Arial">We want
to encourage you to continue discussing this and other TCP's or topics of
interest to you with other Plexus Listserv members. If you would like to
engage with others on the list, please send your comments, observations or
questions to the group. Just click <A
href="mailto:USPlexus@PlexusInstitute.org">here</A>. We'd also like to
hear from you. If you have a piece you'd like to see appear in an upcoming
TCP, send it our way with your own thoughts. Send in your comments to the
<A
href="mailto:PlexusInstitute@PlexusInstitute.org?subject=TCP%20Comments...">TCP</A>.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><FONT face=Arial
size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P></TD></TR>
<TR style="mso-yfti-irow: 6">
<TD
style="PADDING-RIGHT: 0in; PADDING-LEFT: 0in; PADDING-BOTTOM: 0in; WIDTH: 469.15pt; PADDING-TOP: 0in"
vAlign=top width=626>
<P style="MARGIN-RIGHT: 9.2pt"><FONT face=Arial size=3><SPAN
style="FONT-SIZE: 12pt"><IMG id=_x0000_i1026 height=50
src="cid:009001c37b27$20cdb900$1702a8c0@orionsecurities.ca" width=150
border=0></SPAN></FONT></P></TD></TR>
<TR style="HEIGHT: 1in; mso-yfti-irow: 7; mso-yfti-lastrow: yes" height=96>
<TD
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<H2 style="MARGIN-RIGHT: 9.2pt"><B
style="mso-bidi-font-weight: normal"><FONT face=Arial color=#085299
size=5><SPAN style="FONT-SIZE: 17pt">Networking from the
Rooftop</SPAN></FONT></B></H2>
<H2 style="MARGIN-RIGHT: 9.2pt"><B><I><FONT face=Arial color=#085299
size=5><SPAN style="FONT-SIZE: 17pt; FONT-STYLE: italic">MIT Technology
Review </SPAN></FONT></I><SPAN
style="mso-bidi-font-style: italic">Article</SPAN></B></H2></TD></TR></TBODY></TABLE></DIV><FONT
face=Arial size=3><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: Arial; mso-bidi-font-family: 'Times New Roman'; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><BR
style="PAGE-BREAK-BEFORE: always; mso-special-character: line-break"
clear=all></SPAN></FONT>
<P class=MsoNormal><FONT face=Arial size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P><U1:P></U1:P>
<DIV align=center>
<TABLE class=MsoNormalTable
style="mso-cellspacing: 0in; mso-padding-alt: 0in 0in 0in 0in" cellSpacing=0
cellPadding=0 border=0>
<TBODY>
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<TD
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<P
style="MARGIN-BOTTOM: 5pt; MARGIN-LEFT: 37.15pt; MARGIN-RIGHT: 36.2pt; TEXT-ALIGN: center; mso-margin-top-alt: 5.0pt"
align=center><I style="mso-bidi-font-style: normal"><FONT face=Arial
size=3><SPAN
style="FONT-SIZE: 12pt; FONT-STYLE: italic; mso-bidi-font-style: normal"><o:p> </o:p></SPAN></FONT></I></P>
<P
style="MARGIN-BOTTOM: 5pt; MARGIN-LEFT: 0.25in; MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: center; mso-margin-top-alt: 5.0pt"
align=center><I style="mso-bidi-font-style: normal"><FONT face=Arial
color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; FONT-STYLE: italic; mso-bidi-font-family: Arial; mso-bidi-font-style: normal">…
“<SPAN class=GramE>chimney</SPAN> connection” is part of MIT’s <SPAN
class=SpellE>Roofnet</SPAN>, a project to create a self-organizing
wireless network in which an amorphous, unmanaged collection of cheap
Linux computers equipped with <SPAN class=SpellE>Wi-Fi</SPAN> cards
collaborate to efficiently route data packets. Each computer and
roof-mounted antenna at students’ apartments and MIT buildings is a node
on the network and the arrangement in which they are connected to each
other—the topology of the network—is constantly changing. “We want
to understand how a whole bunch of computers with short-range radios can
self-configure a network, forming order out of chaos,” says computer
science professor Robert Morris, who coordinates the
project.<o:p></o:p></SPAN></FONT></I></P>
<P
style="MARGIN-BOTTOM: 5pt; MARGIN-LEFT: 0.25in; MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: center; mso-margin-top-alt: 5.0pt"
align=center><I style="mso-bidi-font-style: normal"><FONT face=Arial
color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; FONT-STYLE: italic; mso-bidi-font-family: Arial; mso-bidi-font-style: normal"><o:p> </o:p></SPAN></FONT></I></P>
<P
style="MARGIN-BOTTOM: 5pt; MARGIN-LEFT: 0.25in; MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: right; mso-margin-top-alt: 5.0pt"
align=right><FONT face=Arial size=3><SPAN
style="FONT-SIZE: 12pt; mso-bidi-font-family: Arial">- <A
href="http://www.technologyreview.com/articles/print_version/wo_guizzo082903.asp">Networking
from the Rooftop</A></SPAN></FONT></P>
<P
style="MARGIN-BOTTOM: 5pt; MARGIN-LEFT: 0.25in; MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: right; mso-margin-top-alt: 5.0pt"
align=right><FONT face=Arial size=3><SPAN
style="FONT-SIZE: 12pt; mso-bidi-font-weight: bold"><SPAN
style="mso-spacerun: yes"> </SPAN>by <SPAN class=SpellE>Erico</SPAN>
<SPAN class=SpellE>Guizzo</SPAN>, <I
style="mso-bidi-font-style: normal"><SPAN
style="FONT-STYLE: italic; mso-bidi-font-style: normal">Technology Review
</SPAN></I></SPAN><BR><SPAN
style="mso-bidi-font-weight: bold"><BR></SPAN></FONT><st1:date Month="8"
Day="29" Year="2003"><SPAN style="mso-bidi-font-weight: bold">August 29,
2003</SPAN></st1:date><SPAN
style="mso-bidi-font-weight: bold"><o:p></o:p></SPAN></P></TD></TR>
<TR style="HEIGHT: 1in; mso-yfti-irow: 1; mso-yfti-lastrow: yes" height=96>
<TD
style="PADDING-RIGHT: 0in; PADDING-LEFT: 0in; PADDING-BOTTOM: 0in; WIDTH: 469.15pt; PADDING-TOP: 0in; HEIGHT: 1in"
vAlign=bottom width=626 height=96>
<P style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><FONT face=Arial
size=3><SPAN style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P>
<P style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><FONT face=Arial
size=3><SPAN style="FONT-SIZE: 12pt"><A
href="http://www.technologyreview.com/articles/print_version/wo_guizzo082903.asp"><SPAN
style="mso-bidi-font-family: 'Times New Roman'">http://www.technologyreview.com/articles/print_version/wo_guizzo082903.asp</SPAN></A></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">A few
weeks ago, MIT graduate student Shan <SPAN class=SpellE>Sinha</SPAN>
canceled his broadband Internet service. Now his Net connection comes
through the chimney. From a computer in the living room of his
</SPAN></FONT><st1:place><st1:City><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Cambridge</SPAN></FONT></st1:City><FONT
color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">,
</SPAN></FONT><st1:State><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">MA</SPAN></FONT></st1:State></st1:place><FONT
color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">,
apartment, a few blocks from the MIT campus, a cable goes into the
fireplace up to the roof, where it is attached to an antenna. From there,
data packets hop to another roof-mounted antenna at a nearby student’s
apartment. That way, from roof to roof in multiple hops, <SPAN
class=SpellE>Sinha’s</SPAN> data packets finally reach a gateway—a
computer connected to the fixed Internet—at MIT’s computer science
building. “We can’t use the fireplace,” he says, “but that’s the cost of
free Internet.” <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><SPAN
class=SpellE><FONT face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Sinha’s</SPAN></FONT></SPAN><FONT
color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">
“chimney connection” is part of MIT’s <SPAN class=SpellE>Roofnet</SPAN>, a
project to create a self-organizing wireless network in which an
amorphous, unmanaged collection of cheap Linux computers equipped with
<SPAN class=SpellE>Wi-Fi</SPAN> cards collaborate to efficiently route
data packets. Each computer and roof-mounted antenna at students’
apartments and MIT buildings is a node on the network and the arrangement
in which they are connected to each other—the topology of the network—is
constantly changing. “We want to understand how a whole bunch of
computers with short-range radios can self-configure a network, forming
order out of chaos,” says computer science professor Robert Morris, who
coordinates the project. The network has now more than 30 nodes in a
4-square kilometer area surrounding the MIT campus. “We hope to reach a
hundred nodes within a few months,” he says. <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Research
groups at universities such as Carnegie Mellon, Rice, UCLA, and the
</SPAN></FONT><st1:place><st1:PlaceType><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">University</SPAN></FONT></st1:PlaceType><FONT
color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial"> of
</SPAN></FONT><st1:PlaceName><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Illinois</SPAN></FONT></st1:PlaceName></st1:place><FONT
color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial"> at
Urbana-Champaign, and at companies such as Nokia, Intel, and Microsoft are
developing similar systems. In each case, data packets are routed through
geographically dispersed and wirelessly connected nodes that can be fixed
in a building or moving with a user or vehicle. Applications of these
so-called multi-hop mesh networks include systems to connect people
carrying <SPAN class=SpellE>PDAs</SPAN>, tanks on a battlefield, or a
large number of sensors in a factory plant. And community mesh networks
such as <SPAN class=SpellE>Roofnet</SPAN>, which are much cheaper to
deploy than DSL or cable hookups, are a promising way to overcome the
“last mile” barrier and bring high-speed Internet access to a large number
of people, especially those who live in rural areas or other places where
the infrastructure for wired broadband access is not
available.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Community-owned
wireless networks have appeared in several places in
</SPAN></FONT><st1:State><st1:place><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">New
York</SPAN></FONT></st1:place></st1:State><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">,
</SPAN></FONT><st1:City><st1:place><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">San
Francisco</SPAN></FONT></st1:place></st1:City><FONT color=black
size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">,
</SPAN></FONT><st1:City><st1:place><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Seattle</SPAN></FONT></st1:place></st1:City><FONT
color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">,
</SPAN></FONT><st1:City><st1:place><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">London</SPAN></FONT></st1:place></st1:City><FONT
color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">, and
other cities. These networks usually consist of a few interconnected base
stations—known as wireless access points—located in windows and rooftops
providing Internet connectivity in public spaces. The new <SPAN
class=GramE>generation of mesh networks such as <SPAN
class=SpellE>Roofnet</SPAN> cover</SPAN> wider areas and are much more
dynamic in the way they route data. Their nodes are not permanently
connected; instead, they constantly revaluate the existing links and form
new ones. As a result, data follows much more tortuous
paths to reach the fixed Internet. And with tens or hundreds of
nodes—some of them joining and leaving the network in a random fashion and
thus constantly changing its topology—a difficult problem arises: how
should data in these multi-hop wireless nets be routed? What paths in this
labyrinth of rooftop and window antennas optimize the flow of
packets?<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><B><FONT face=Arial
color=black size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Distance
Matters</SPAN></FONT></B><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">
<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Most of
the routing protocols now being proposed by mesh network researchers
borrow the shortest-path strategy used in the fixed Internet. These
protocols try to find the route with the fewest number of intermediate
nodes between sender and destination. For the wired Internet—with its
nearly static topology and reliable links—this scheme has been working
pretty well: our e-mails hop from router to router and reach the other
side of the world in a few seconds.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">But it
turns out that this shortest-path strategy might not be adequate for
sending packets through the air. In a wireless network, according to the
MIT group, distance matters: the longer the signal has to travel, the more
it will degrade. Moreover, the link quality between nodes varies
unpredictably due to such transient phenomena as trucks driving by,
moisture in the air, or a pigeon sitting on the antenna. The result is a
considerable amount of packet loss, transmission errors, and connections
that simply appear and disappear throughout the day. A routing protocol
that minimizes the number of hops ends up choosing longer distances for
each hop—and therefore sending data over low-quality wireless links.
<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">The MIT
group realized that new routing strategies were necessary when they
deployed an initial version of <SPAN class=SpellE>Roofnet</SPAN> last
spring. They tried to implement some of the proposed routing protocols
discussed by the Internet Engineering Task Force, the organization
governing the Internet's technical standards. But while these protocols
work well in theory—and are generally tested in computer simulations or
small-scale, laboratory networks—they don’t take into account many
unpredictable factors involved in radio communication. The protocols
usually assume, for example, that when one node can detect one
nearby, it can communicate well with its neighbor. But that turns out not
always to be true. The MIT researchers and other groups have found that
many times two nodes can “hear” each other by exchanging small probe
packets, but when they try to send real data, communication collapses due
to inadequate bandwidth. Morris and his group decided that the best way to
develop robust wireless routing protocols was to test them with a
real network, real users, and real traffic. <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Other
mesh network researchers say the MIT work represents an important advance
for debugging these routing schemes. “Their work is grounded in real
system building,” says Victor <SPAN class=SpellE>Bahl</SPAN>, a senior
researcher who leads the networking group at Microsoft Research in
Redmond, WA. “The insight that you get out of building things is a lot
more than you’ll ever get if you just simulate things.” Demonstrating that
such networking is viable in a real, large-scale implementation, he says,
is a crucial step toward attracting more industry attention to the
technology's potential.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Deploying
such a network became possible because <SPAN class=SpellE>Wi-Fi</SPAN>
technology has gotten so cheap. A few years ago, Morris says, the price of
the wireless cards would have made the project prohibitively expensive.
Each <SPAN class=SpellE>Roofnet</SPAN> node uses an 802.11b wireless
networking card installed on a cheap PC running Linux and the routing
software. A coaxial cable connects the wireless card to an <SPAN
class=SpellE>omnidirectional</SPAN> antenna. The user then connects the PC
to the <SPAN class=SpellE>Roofnet</SPAN> node. The total cost of the
equipment for each node is $685. <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">To
deploy the network quickly, the MIT group distributes free
self-installation kits to students who want to participate in the project.
For these students, getting the <SPAN class=SpellE>Roofnet</SPAN> node
running is part of the fun. “Our antenna was put up by a friend of mine
who does rock climbing,” says graduate student <SPAN
class=SpellE>Roshan</SPAN> <SPAN class=SpellE>Baliga</SPAN>, who lives in
a two-story building with no easy roof access. “He scaled the side of the
apartment to get to the roof, installed the antenna, and then rappelled
down.”<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">MIT
students are happy to participate in the project, especially because they
can save some money. “We compared a broadband cable connection to <SPAN
class=SpellE>Roofnet</SPAN> and couldn’t tell the difference, so we
cancelled the cable,” says MIT senior Walt Lin, who installed the antenna
on his sloped roof.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><B><FONT face=Arial
color=black size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">The
Road Ahead</SPAN></FONT></B><FONT color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">
<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">With
students surfing the Web, downloading music files, and working on problem
sets on remote servers, the network is running with real traffic. Now
Morris and the four graduate students working with him full time on the
project can test different routing strategies that better adapt to the
hostile wireless environment. <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Their
idea to cope with the unpredictable environmental disruptions is to figure
out not just whether two nodes can hear each other, but also measure how
well they can communicate. Instead of finding the shortest path between
two nodes, their protocols try to find the best path—the one in which data
packets won’t get stuck or corrupted along the way. This requires a
constant monitoring of the links. Roughly once per second, each node sends
out a small “hello” broadcast packet. All the other nodes record whether
they receive this probe, keeping a history of the last 10 probes. So if,
say, node A has sent out 10 probes and node B received 8 and node C
received 4, then the routing software knows that the path A-B is better
than path A-C. Also, every 15 seconds, every node sends a broadcast
message that lists the nodes it knows how to reach—and the link quality
for each associated path. That way, all nodes have a complete, continually
updated, routing map of the entire network—and know the optimal routes for
reaching one another. <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">In
building <SPAN class=SpellE>Roofnet</SPAN>, the MIT researchers found many
things they didn’t expect. For example, the range of the 802.11b cards and
antennas vary considerably. “We’re now skeptical about what manufacturers
say,” says John <SPAN class=SpellE>Bicket</SPAN>, one of the grad students
working on the project. “We found nodes that couldn’t talk across the
street, but others could talk half a kilometer apart.” The cause might be
local environmental conditions or even multiple reflections of the same
signal that cancel themselves out. Another surprising phenomenon is the
lack of symmetry in the link transmission quality: it is not uncommon for
node A to be able to send data to node B easily, while node B can’t
reciprocate. Such anomalies complicate the development of routing schemes.
<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">By
debugging and fine-tuning their routing schemes, the MIT researchers
hope they will be able to use them in even more complicated systems. One
such situation would be when nodes are not static in rooftops, but
moving at different speeds in all directions—a scenario not far in
the future, as more and more people carry personal digital assistants
and cars are beginning to be equipped with computers. “It’s a matter of
tuning the protocol so that it can handle mobility,” says <SPAN
class=SpellE>Sanjit</SPAN> <SPAN class=SpellE>Biswas</SPAN>, another
student involved in the project. <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Ultimately,
Morris says the group plans to release the <SPAN
class=SpellE>Roofnet</SPAN> routing software as a freely <SPAN
class=SpellE>dowloadable</SPAN> open source program. That means that
anyone with a computer and a <SPAN class=SpellE>Wi-Fi</SPAN> card would be
able to install the routing software and become a node in the network.
Other people in other areas could also download the software and create
their own rooftop community networks.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">Of
course, many problems still need to be addressed. First, MIT can’t provide
Internet access to non-MIT affiliates; the network would
therefore eventually have to find other gateways to the fixed
Internet. But that raises another complicated issue: most Internet service
providers don’t want their users sharing their bandwidth. Also, the
community networking technology needs to guarantee a certain level of
security and privacy. With users literally sending their data through the
air, via other people's nodes, some sort of encryption will probably be
necessary to avoid eavesdropping. It is also necessary to guarantee a
fair, balanced used of the system, to avoid that a single user sucks all
the bandwidth and clogs the network. Finally, the system needs to be
robust enough to resist some more pragmatic problems—such as when snow
forms in the antennas.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT
face=Arial color=black size=2><SPAN
style="FONT-SIZE: 11pt; COLOR: black; mso-bidi-font-family: Arial">When
the day comes, what will happen? Again, the MIT group wants to learn by
doing. “We’ll see,” says Morris.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN-RIGHT: 9.2pt; TEXT-ALIGN: justify"><FONT face=Arial
size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P></TD></TR></TBODY></TABLE></DIV>
<P class=MsoNormal><U1:P></U1:P><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman'"><o:p> </o:p></SPAN></FONT></P></DIV></BODY></HTML>
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