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[Ham-80211] Why? (was Handoff between access point? )

Larry Cerney lcerney at viawest.net
Wed Nov 24 16:56:12 UTC 2004


Carl, et al;

Follow up on my Google search.  Check out Tom's Networking it's easy to read
and has some good examples.
http://www.tomsnetworking.com/Sections-article78-page1.php

Tom's also points to a Proxim Application note at:
http://www.proxim.com/support/techbulletins/TB-046.pdf

Here is a well written student paper (if a little sleep inducing) on
Benefits of Packet Aggregation in Ad-Hoc Wireless Network:
http://systems.cs.colorado.edu/Papers/Generated/2003_Benefits_of_Aggregat.pd
f

Read through those articles and you'll have a better understanding of what
it might take to do a citywide 802.11 network.

73....
Larry
K0ANI

"The wireless telegraph is not difficult to understand. The ordinary
telegraph is like a very long cat. You pull the tail in New York, and
it meows in Los Angeles. The wireless is the same, only without the
cat." 
-Albert Einstein (1879-1955)

-----Original Message-----
From: ham-80211-bounces at lists.tapr.org
[mailto:ham-80211-bounces at lists.tapr.org] On Behalf Of Larry Cerney
Sent: Wednesday, November 24, 2004 9:14 AM
To: 'TAPR Mailing List for Ham Radio Use of 802.11'
Subject: RE: [Ham-80211] Why? (was Handoff between access point? )

Carl,

It is doable, technically.  A citywide network would need multiple access
points spread throughout the city.  They must all be aware of their
neighbors in the network and in its simplest form be on the same subnet.  If
they are all on the same subnet, the mobile could retain the same IP address
across the city.

Each AP would need connection to the internet via some sort of VPN to go
back to a central hub subnet.

Another way would be to build a mesh network in which AP's work together to
pass data wirelessly back to a central hub.  The problem with doing this is
as the data moves to the hub it is concentrated with data from other AP and
this reduces the effective bandwidth of the network.  This might not be
critical if your only downloading email, but could bring down a network if
you kid in the back seat is watching Lord of the Rings via the internet or
down loading LL Cool J's latest CD. ;-)

Do a Google search on Wireless Distribution Service or WDS which will
explain how AP's can work together to pass data from AP to AP wirelessly.

There will be other way of doing this in the future.  There has been much
said about 802.16 wireless MAN networks which could be run under Part 97 or
might come about commercially soon (next couple of years).

As I said, it is doable, but don't expect to drive into a town and have
mobile Internet access anytime soon.  

"The only reason for time is so that everything doesn't happen at once." 
--Albert Einstein 


> 
> Carl Walthall wrote:
> 
> > Hi All
> >
> > If a person setup a large 802.11b network under part 97 city wide
with
> > multiple access points running infrastructure.  Could a person with
a
> > laptop in their car drive from one end to the other without losing
> > connection? In other words, could the network be setup to handoff
the
> > connection from access point to access point the same as a cell
phone
> > would (Mobile IP)? I am sure its not the same, but could you stay
> > connect as long as your getting a strong signal from a access point?
I
> > would also like to know the best place to read up on this subject?
> >
> > Thanks in advance
> >
> > Carl Walthall



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