Subject: RE: Geo-routing & radio

From: "Groten, D." <[email-masked]>
Date: Fri, 17 Nov 2000 09:20:36 +0100

Hi,
It is important to realise that at this moment, GPS in not working well
indoors. The GPS receivers needs to be in direct line of sight with the
satelites, and therefore only work properly outdoor. This is a major
drawback of GPS right now. There are developments under way to improve this,
but that comes down to equipping buildings with GPS enabling facilities
(relay antennas e.g.).

Dirk.
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Dirk Groten	      	       KPN Research		
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P. O. Box 421		       Tel: +31 6 53747220
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-----Original Message-----
From: Chip Elliott [mailto:[email-masked]]
Sent: Thursday, November 16, 2000 11:59 AM
To: Li Li
Subject: Geo-routing & radio

>
>It seems to me if GPS is available. Routing algorithm that exploit GPS
>should be used (the one you cited here) instead of using AODV which is
not
>designed explicitly with GPS in mind. Protocols like DREAM, LAR and
GPSR
>will perform better if GPS is available.  The evaluation of GPSR vs.
DSR in
>the GPSR papers show this. Any counter arguements?
>

Li,

The basic problem with geo-routing schemes is that
geographic proximity is often not a good predictor
of RF pathloss.

This is especially true in "urban canyons",
within buildings, etc, but is also true in the
great outdoors. Often these RF propagation maps
look like someone sneezed on a map.

Thus the "shortest path" between two RF network nodes
may well look nothing like a geographic great circle.

In addition, of course, if the routing is in
any way load- or RF-dependent (eg tries to route
around interference), geographic routing must be
augmented or supplemented by these additional
criteria.

For an experiment, I'm trying to attach a fairly
realistic pathloss map (jpeg) that I found on the web.
It's at: http://www.qsl.net/fara/dxcluster/propo/overview2.html.
This particular model employs a Longley-Rice propagation model
that factors in terrain, the antenna pattern, propagation
loss at the designated frequency, receive sensitivity,
transmit ERP, receiver antenna height, and transmit antenna height.

Best wishes,

Chip Elliott
Principal Engineer
Mobile Networks, BBN

---

From: Rex Buddenberg <[email-masked]>
Date: Fri, 17 Nov 2000 08:35:51 -0800

GPS uses L-band signals which are pretty much line of sight.  If 
you're getting a usable signal indoors at all, it's got so much 
multipath pollution that it won't be very accurate -- multipath is 
often good in communications but never in radionav.

  You should remember that GPS isn't the only radionav system out 
there; Loran is very much alive and provides complete US and western 
European coverage.  It uses 100kHz frequency and penetrates much 
better ... indeed I I've heard from cavers who use Loran for cave 
mapping.

-- 
b