Published at [http://www.nycwireless.net/tiki-read_article.php?
articleId=23]
Mesh-based networks are wireless networks, based on Wi-Fi technology,
where each wireless "node" or Access Point connects with a number of
other wireless nodes. Information flows from node to node, winding up
either at its destination or the internet in general. Internet
connections, in a mesh-based network, are provided by one or more
nodes that connect to the internet directly (referred to as "backhaul").
^"Robust and reliable, mesh wireless systems offer multiple points of
connection to the network and no central tower. Mesh users can bypass
obstacles like hills and trees by using different signal paths. Mesh
networks are easily expandable at very low cost, and they have no
single point of failure. Mesh networks also feature shorter distances
between nodes, which means each antenna can broadcast at lower power,
creating less interference and allowing more users to communicate
simultaneously." (from [http://www.freepress.net/wifi/guide2.php])^
The benefits of mesh technology are many:
*self-organized, dynamic routing and connection
*little or no centralized configuration
*each node is interchangeable with every other node
*overlapping wireless coverage areas ensure that no node is a point
of failure
*no wires are necessary, as the network is entirely wireless
*organic build-out of the entire network is possible
*multiple separate networks can be built independently and grow into
a single cohesive network
*redundant paths to backhaul
*easy/seamless addition of additional backhaul
The alternative for wireless networks are "hub-and-spoke" networks,
so called because they resemble bicycle wheels in their architectural
diagrams. In hub-and-spoke networks there is one central distribution
node with which all client nodes communicate. This centralized
architecture is like the cell phone networks: even when client nodes
are close to one another, they must route through the central tower
in order to communicate. This creates a single point of failure, and
requires significant infrastructure at these tower nodes.
Mesh networks are designed to survive the failure of a single node
(and sometimes more than single node). Like the internet itself, mesh
networks have significantly more resiliency built in. Its untrue that
they are more likely to go down than non-mesh networks; This is like
saying that cars with airbags are more likely to crash. The fact is
that mesh networks have extra safeguards from failure, and reduce the
likelihood of network failure.
Furthermore, since there is built in overlap between the service area
of neighboring mesh nodes, if one should go down, service should
still be available in its coverage area (albeit at a possibly lower
data rate). Because mesh nodes are interchangeable, servicing the
network is as simple as plugging in a new node where one has failed.
This isn't nearly so easy to do with a non-mesh network, even one
that has a centralized network management system. Mesh networks need
no such network management infrastructure, since their management
intelligence is built into each node, and is spread dynamically
throughout the entire network.
So, what does this mean for New York City? Let's look at a couple of
examples, which [http://www.nycwireless.net/|NYCWireless] has had the
opportunity to investigate:
!In Building Wireless Network
New York City has a plethora of apartment buildings, many of which
date from the early or mid parts of the 1900's (and some even
earlier). These buildings have electrical and phone systems, but even
cable networks are an add on. Creating an additional network is both
expensive and difficult for these buildings, since it often requires
significant construction to create a complete wired network
infrastructure that is safe from the elements. This is the reason why
Wi-Fi has been so popular with New Yorkers--cable and DSL modems
don't often reside where people want to use their computers.
Using a mesh-based wireless network, such buildings are easy to
"light up". Traditional hub-and-spoke wireless networks rely on a
distributed wired infrastructure (like cable and DSL networks),
whereas the only requirement for a mesh network is electricity. Using
a centralized backhaul located in one or a few places in the
building, and inexpensive mesh wireless devices, an entire building,
servicing 100's of units, can be brought merely by plugging in the
nodes at appropriate locations (3-10 per floor, on average).
Since most buildings have thick walls separating apartments or
floors, if there is a spot in the building where the wireless signal
is weak, just add another mesh node nearby. And since the nodes are
usually powerful enough to communicate between adjacent floors, the
network will have multiple routes up and down the building, ensuring
that even if part of the network goes down, the rest of the network
will still work.
Distributing a wired backhaul (T1 or fiber internet connection)
throughout a building is cost effective, but it may not even be
necessary all of the time. If there is another nearby building with
lots of available bandwidth--like a school, library, or even
business--setting up a higher-powered mesh node at that location will
enable the extra network capacity to be wirelessly beamed into the
building through the windows. With this type of network, there might
not even be any wired internet at all within the building!
!Business District Network
New York City is filled with Business Districts. Whether you live on
the south side of Staten Island, Central Harlem, or along Northern
Boulevard in Queens, there are plenty of areas where small businesses
(and sometimes large ones) line the streets for blocks on end.
Especially for small businesses, bringing in an internet connection
can be both costly and time consuming (waits of months for a T1 are
not unheard of). Considering that many small businesses would rather
place their resources into running and building their shops, spending
all of that time and money, month over month, on simple internet
access can be a wasteful investment.
Creating a wireless hotspot all along a business district benefits
residents, businesses, and visitors to that area. This is the primary
reason why the [http://www.downtownny.com|Alliance for Downtown New
York] partnered with [http://www.nycwireless.net/|NYCWireless] to
help create its [http://www.downtownny.com/?sid=49|wireless network
in downtown Manhattan], and why other Business Improvement Districts
(BID) and Parks have worked with [http://www.nycwireless.net/|
NYCWireless] in similar capacities. Creating a hotspot that exists
outside (throughout the cold New York winter) is hard enough.
Creating a hotspot, using traditional non-mesh wireless technologies,
that is larger than a standard City block is even harder. Consider
that such a hotspot likely needs more than one DSL connection, that
its hardware must be mounted outdoors, and that if a local business
is a participating host for all or part of the network, that the
network becomes dependent upon that business staying in that location
for years on end.
All of these difficulties are easily solved by using a mesh network.
Instead of mounting the hotspot access point and large antenna on the
top of a short building, the multiple nodes of the mesh network can
be mounted inside or next to local storefronts, lining the street.
Backhaul can reside inside of a building where it is easy to get to,
and more DSL lines can be added as needed. Since there are more mesh
nodes than the few traditional access points, coverage is better.
The best part of this architecture is that the business district
network no longer is reliant on one or a couple of businesses.
Instead, the backhaul can be provided by a long-standing resident of
the area--most likely a BID or City organization--and the network can
flow down the street. As local businesses come and go, the BID can
merely unplug a mesh node from a departing business, and plug it in
next door. The network continues to operate, and service never has to
go down for more than a few minutes (if even that). In this type of
community architecture, a traditional hub-and-spoke network would be
unmanageable.
!City-wide Network
New York City represents a great challenge for any wireless network.
The dense metropolitan area covers about 240 square miles, and much
of that area is covered by buildings 20 or more stories in height.
New York is truly a huge, three dimensional city.
Creating a large scale wireless network throughout New York
represents a great challenge--one that [http://www.nycwireless.net/|
NYCWireless] would love to help solve. In all likelihood, any
solution that makes this endeavor tractable will need to make use of
multiple network technologies, and combine network deployments from a
number of providers. To be sure, New York will require more ingenuity
than that of Philadelphia's, San Francisco's, and Boston's wireless
city plans.
Here again, mesh networks can play multiple roles. Nodes can disburse
wireless internet backhaul from the city's dark fiber and existing
excess bandwidth via a mesh network mounted on lamp posts. That
network can feed separate mesh networks that draw the internet up
into and throughout a building like a tree drinks water. And people
and businesses can move their lives and their livelihoods from
building to building without causing network disturbances.
With the help of mesh networks, New York can become a living, organic
city, whose lifeblood is the packets of information that flows freely
from point to point, person to person, bouncing around automatically
finding its way to and from the internet.
Dana Spiegel
Executive Director
NYCwireless
[EMAIL PROTECTED]
www.NYCwireless.net
+1 917 402 0422
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