At 05:59 p.m. 24/08/00 +0100, you wrote:
>Hello Miguel Angel,
>
>you could also implement DAMA protocol in your packet transmissions. DAMA
>means
>that all stations logged in get polled cyclically, so one station is something
>like a "master" calling the shots. This way most airtime collisions of aignals
>can be avoided.

Sound good, Ill consider it.



>But.....what the (...) do you need to let your poor guys transmit 10 numbers
>every 6 seconds?? Don't they have something else to do?? What kind of
>application are you considering?

Actually it will be something like 10 numbers every minute, with high-rate
times about the midday.
Its like collecting survey data.


>Apart from that, dedicated links in Germany use different data rates up to
>57.600 presently, but on bands above 440 MHz. The 2.45 GHz ISM band would give
>the needed capacity. Then all your worries about data rate are over. There are
>some cheap controllers available for these data rates, German Hams use them
>plenty...


Heehehe, i guess we dont have pretty the same technology in Mexico and,
even if we import it, the need to be cheap I dont think that it apply here.
Thanks for the info.


>Greetings to the list,
>
>Jochen Feldhaar


Thank you Jochen, a lot.


>"If it starts to work, it's no fun any more"
>
>Miguel Angel Heredia Moreno schrieb:
>
> > At 10:56 p.m. 23/08/00 -0500, you wrote:
> > >On Wed, 23 Aug 2000, Miguel Angel Heredia Moreno wrote:
> > >
> > > > for the FM transmission first post ... consider this :
> > > >
> > > > 1) You got 50-100 people around a city working office-time jobs
> > > > 2) Each one of them collect about 20 numbers every minute
> > > > 3) They mut send this and verify they were received well and store them
> > > locally
> > > > 4) They need this units to be mobile (no car)
> > >
> > >Tall order, especially if you need it done cheaply.
> > >
> > > > theres another way to do this than packet radio ?
> > >
> > >Sure.  Does it **HAVE** to be done in real time?  I bet not.
> >
> > No, I can afford a little delay, lets say : the guy is in the street with
> > his unit and put the numbers in and it say : "wait, busy" and then he
> > retries till its ready, lets say about really 10 numbers per minute.
> >
> > >If it's got to be done in real time, you're looking at possibly 100 * 20 =
> > >2000 messages, plus ACK packets, for a total of 4000 packets per minute,
> > >or roughly 67 packets per *second*, assuming no retries or collisions. To
> > >say that would be difficult to engineer would be an understatement.  You
> > >would need to be running very high data rates on UHF with several Watts at
> > >the very least, and I doubt even that would work.  The battery to keep a
> > >radio delivering that kind of duty would be heavy, too.
> > >
> > >If it's got to be fast but not real-time, you could store up X amount of
> > >messages from a remote and send them in a batch.  You would still wind up
> > >with a pretty busy channel.  Send a packet every five minutes, maybe.
> > >Then you could get away with 1200BPS at VHF, and 1200 is a *lot* easier to
> > >get working reliably than 9600 or higher.
> >
> > I was taking this in account too, to upload the data in the evenings but,
> > Wouldn be more problems if ALL them send ALL their data around a time ? it
> > wouldnt be better if they upload piece-by-piece bytes of data every few
> > minutes ?
> >
> > >If it doesn't have to be real time, why not a small, portable, non-radio
> > >device to store the information during the day and uplink it via modem, or
> > >even by packet radio, at night?  If real-time is not a requirement, I
> > >would trade lots of on-board RAM and occasional uplinks for the complexity
> > >and cost of a radio solution.
> >
> > >Just some ideas for you.  I love radios.  I love working solutions even
> > >better, though.
> > >
> > >Dale
> >
> > Thank you Dale, a lot! :)
> >
> > >---
> > >The most exciting phrase to hear in science, the one that heralds new
> > >discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
> > >                 -- Isaac Asimov
> > >
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