mobile data comm

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

Reply to
awk2861
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Use local datastorage and burst transmission when close to some locations or the home location. That way you can wait for the right conditions to appear. Wifi at a few spots with max level protection would do nicely, and require only a few licenses.

Reply to
Sjouke Burry

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!

Reply to
RadioSchlock

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