Hi all,
Does anyone know of a cheap mobile long distance (20+ miles) data
communication service that would work in a large city environment?
I'm looking into communication of prognostic data on vehicles.
Basically a bunch of vehicles would be traveling around within a
certain range of a main building. They would each send data back (say
once every 5 min) for processing.
Cost is a main factor. I've looked into cell modems, but I'm not aware
of any service without a substantial recurring cost. (For example $30/
month for 200 vehicles adds up fast). Radio modems can operate in
license free bands, but I'm worried about the amount of noise as well
as the distance that would be achievable in a city.
Any thoughts / relevant experiences would be appreciated.
Thanks
Andy
Hey Andy,
uS "gEeKs" over here at RadioSchlock built something very similar to
what you have
described as a technology demo for some petroleum transport folks.
We had hacked up some embedded processor cards for use in a vehicle,
then added
GPS, RTCM Corrections, OBD II port, J1850 Bus support, Flowmeter
Interface,
read some valve switches, stuck on an LCD message terminal with some
canned
status keys and voila!
Folks could pick what engine and drive train messages they wanted to
display and or
trigger emails on, as well as, ping the driver about being late!
Back when we put that system into operation there were only CDPD
modems available
which worked well in most places but, were fairly expensive to operate
when applied to
a large numbers of vehicles.
So we rigged up our own chicken wireless data system to go around the
problem. It took
a lot of help money wise from some very forward looking business types
and a bunch of
calculation, design, build a few, install at good sites after much
propogation modeling,
and then test the heck out of it type stuff.
Hmmm. Guess this was about 1997 or 98 but we did get the sort of
ranges that you
are talking about here in the Phoenix area without too much problem.
Around 22 miles
or so with reliable data links. Data was usually 100 percent
correctable (Good FEC) with
very little retransmission.
About 13 percent per 100KB worst case if memory serves?
Shoot! It is not easy to circumvent the wireless carriers, and do your
own thing.
In essence, that's what you are really asking about.
Unfortunately in most areas of the Eastern U.S. seasonal ground cover
will eat your lunch
when it comes to the number of fixed sites needed to replicate the
sort of wireless
network coverage and QOS that todays common carriers can provide, but
it can be done.
Now as you may have noticed I haven't told you how to do it... Why?
Because I can't.
Trade secrets, patents, non-disclosures, Big Brother, etc. You get the
picture.
But I can help you by telling you what will not work which might be
more valuable..
And possibly, depending on what you are really up to?
I can tell you about some fairly simple approaches that may work out
for you,
but were impractical for our projects.
Out here in the Southwest it is comparatively easy... Back East, Not
so easy...
P.S. send me a phone number and best time to call.
I will call you so that we might discuss what you are attempting to
do. It sounds fun!
All the best,
dE"gEeKs"
RadioSchock Labs
Phoenix, Az
Out here, just get a few good hill tops and away you go!
