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'[PIC]: RF protocol, repeaters and PICs'
2002\10\08@104646 by oyalhi

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Any ideas on the rf repeater design?  Although it seems easy at first,
it is kind of complicated I think.  Let's say there is a transmition at
point A to point D.  However since the distance between point A and D is
long the signal can't make it.  So I put two repeaters between point A
and point D, namely at points B and C.

 A              B               C                 D

Now, B transmits whatever it receives (it is a repeater) so the
transmittion from A received by B, again trasmitted by B.  Now, A and C
receives these signals and again C transmits and this time B and D
receives these signals.

We are happy because the signal is transmitted to point D, but also
transmitted to point B.  Since at point B we have a repeater, it will
send the info again.  This will be like ping pong between B and C.
Imagine if we have more repeaters together!

Are there any info on repeater protocol? Or RF protocol that includes
repeaters?  Any help is greatly appricated.


Ömer YALHI
spam_OUToyalhiTakeThisOuTspamteksan.com.tr
http://www.teksan.com.tr
Tel : +90 212 613 22 00
Fax: +90 212 544 70 35

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2002\10\08@105900 by Wagner Lipnharski

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Ömer Yalhý wrote:
{Quote hidden}

Isn't it marvelous that you can tune different FM radio stations?
Isn't it marvelous that even hearing my own voice I don't mix up thinking
is somebody else talking?

VV46NER

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2002\10\08@112910 by Dale Botkin

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Take a look at how AX.25 packet radio works.  Digipeaters and all.

Dale
---
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Fusistance is retile.
Your ass will be laminated.

On Tue, 8 Oct 2002, [iso-8859-9] Ömer Yalhý wrote:

> Are there any info on repeater protocol? Or RF protocol that includes
> repeaters?  Any help is greatly appricated.

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2002\10\08@173223 by David Duffy

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At 05:48 PM 8/10/02 +0300, you wrote:
>Any ideas on the rf repeater design?  Although it seems easy at first,
>it is kind of complicated I think.  Let's say there is a transmition at
>point A to point D.  However since the distance between point A and D is
>long the signal can't make it.  So I put two repeaters between point A
>and point D, namely at points B and C.
>
>   A              B               C                 D
>
>Now, B transmits whatever it receives (it is a repeater) so the
>transmittion from A received by B, again trasmitted by B.  Now, A and C
>receives these signals and again C transmits and this time B and D
>receives these signals.
>
>We are happy because the signal is transmitted to point D, but also
>transmitted to point B.  Since at point B we have a repeater, it will
>send the info again.  This will be like ping pong between B and C.
>Imagine if we have more repeaters together!

Can you add an address byte that gets incremented at each repeater?
That way, only the intended recipient will pass the packet down the line.
The other way is to transmit & receive on different frequencies but that's
not practical if you're using simple pre-built modules.
David...

___________________________________________
David Duffy Audio Visual Devices P/L
U8, 9-11 Trade St, Cleveland 4163 Australia
Ph: +61 7 38210362 Fax: +61 7 38210281
New Web: http://www.audiovisualdevices.com.au
___________________________________________

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2002\10\08@184820 by Nate Duehr

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Digitial repeaters of this sort need an addressing scheme.  Source and
destination, and then who actually transmitted a particular
transmission, at the very least.  
Then you can do things in software to "quench" round-robin packets. Timers and fun.  Say A transmits to D... B retransmits to everyone, A
ignores it, C retransmits it.  If B can put a bit of info in the packet
to say it's already been through B, then B can ignore the retransmission
it hears from C.  This type of network is very "chatty" and noisy. Having some intelligence in the routing helps.

If the devices can check to see "who can hear who" early on in the power
up sequence (assuming they're stationary) you can build a "route table"
and distribute it (similar to the old RIP protocols of the Internet) and
then update it if a route appears to not work for a period of time...
this is a "link-state" protocol.  
"Distance-vector" type protocols can also be used as another example...
there's lots of examples of this out there, some work better than others
over RF which typically suffers from interference from time to time, and
state changes more than most wired networks.

Nate
On Tue, 2002-10-08 at 08:48, Ömer Yalhý wrote:
{Quote hidden}

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2002\10\09@023716 by oyalhi

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I am planning to use the same frequency for all communications and every
device will also act as a repeater.  It won't be fixed, so I cannot give
the route information, I would like the system to be flexible.  If two
devices are too far to talk to each other, I just want to throw a
repeater between them and that's it!  (I hope I can do that though)

Now at least I know where to start about this.  How about power saving?
I could put the pic to sleep but the receiver???  I am thinking at some
point I ping the network and all the devices synchronize their clocks,
and I do this at power up and every week(?) and blah blah.  But this is
not a very good solution.  How could I make the receiver/transceiver to
sleep and wake up automatically?  Is there such a thing?

Thank you for all the help, I had no idea to where to look now I have a
place to start.


Regards,


Ömer YALHI
spamBeGoneoyalhispamBeGonespamteksan.com.tr
http://www.teksan.com.tr
Tel : +90 212 613 22 00
Fax: +90 212 544 70 35

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2002\10\09@023801 by Vasile Surducan

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Omer, I'm happy you have evoluted to RF ! :)
I think you have to switch the frequency to every repeater because you
will not be able to built and mount such good antennas to avoid the "biting
effect" between reception and transmision. I suggest for your application
( if it's the same ) to check also the X10. It might work for appartments
supplied from the same mains phase.
Replicating your transmitter on 3 phases, I think will work. Anyway X10
repeaters are cheapers than whole authorisations you might need for wireless.

best regards and success !
Vasile
http://www.geocities.com/vsurducan


On Tue, 8 Oct 2002, [iso-8859-9] Ömer Yalhý wrote:

{Quote hidden}

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2002\10\09@034909 by oyalhi

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Hi Vasile,

Nice to hear from you again.  The reason I am considering RF is because
it is a lot cheper and less complicated than the cable alternative and
less risky.  After we have talked I have postponed the project and
research a better and hopefully cheaper alternative.  The company
(company that puts the parts on the pcb's I don't know what they are
called) we work with here is going to provide me the transievers very
(VERY!) cheap so that it makes the cable mess not worth while.  However
I think I will run into trouble with the interferance.

Regards,

Ömer YALHI
oyalhiEraseMEspam.....teksan.com.tr
http://www.teksan.com.tr
Tel : +90 212 613 22 00
Fax: +90 212 544 70 35



Omer, I'm happy you have evoluted to RF ! :)
I think you have to switch the frequency to every repeater because you
will not be able to built and mount such good antennas to avoid the
"biting effect" between reception and transmision. I suggest for your
application ( if it's the same ) to check also the X10. It might work
for appartments supplied from the same mains phase. Replicating your
transmitter on 3 phases, I think will work. Anyway X10 repeaters are
cheapers than whole authorisations you might need for wireless.

best regards and success !
Vasile
http://www.geocities.com/vsurducan

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2002\10\09@042230 by Vasile Surducan

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On Wed, 9 Oct 2002, [iso-8859-9] Ömer Yalhý wrote:

> Hi Vasile,
>
> Nice to hear from you again.  The reason I am considering RF is because
> it is a lot cheper and less complicated than the cable alternative and
> less risky.  After we have talked I have postponed the project and
> research a better and hopefully cheaper alternative.  The company
> (company that puts the parts on the pcb's I don't know what they are
> called) we work with here is going to provide me the transievers very
> (VERY!) cheap so that it makes the cable mess not worth while.  However

 If the module are soo cheap, are you interested to send me for free,
two transiever modules, just to consolidate the friendship relation
between us ? :)

Thanks, and best wishes, any answer will be,
Vasile











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2002\10\09@052814 by oyalhi

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Vasile,

Apperantly the company is waiting for some parts to finish it.  I am
waiting for them also and have not tested them yet.  He told me he has 5
on hand, and he will make more.  As soon as he makes more, hopefully
within couple of weeks, I will let you know and send you for free.  (I
even have put a reminder for 21st of October so I don't forget)

Regards,

Ömer YALHI
EraseMEoyalhispamteksan.com.tr
http://www.teksan.com.tr
Tel : +90 212 613 22 00
Fax: +90 212 544 70 35

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2002\10\09@104356 by Jim

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> Any ideas on the rf repeater design?  Although it seems easy
> at first,

How do you mean?

Actual 'repeating' of the RF (through suitably designed amplifier
chains and separate appropriately-spaced antennas engineered to
operate in-band and on-channel) or just the modulation content
(certain or all information content)?

I ask because there *are* techniques that amplify the 'raw',
if you will, RF as opposed to first demodulating it *then*
retransmitting it ...

'Repeating' of the information content (using a series of
receivers, data processors/routing analyzers and transmitters)
delves into a different and slightly more complex field of
issues ...

RF Jim



{Original Message removed}

2002\10\09@105403 by john

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you would most likely need a "routing" protocol at least .... or have
different frequencies on each "cell"

split your frequencies up as if you were putting them on cells of a
hexagonally shaped network object

J
On Wednesday 09 October 2002 04:40 pm, Jim wrote:
{Quote hidden}

> {Original Message removed}

2002\10\09@111440 by Jim

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----- Original Message -----
From: "John Ward" <RemoveMEjohnEraseMEspamEraseMEAGENT-J.COM>
To: <RemoveMEPICLISTspam_OUTspamKILLspamMITVMA.MIT.EDU>
Sent: Wednesday, October 09, 2002 9:42 AM
Subject: Re: [PIC]: RF protocol, repeaters and PICs


> you would most likely need a "routing" protocol at least .... or have
> different frequencies on each "cell"

Both these techniques are done routinely and with ease (simply
demonstrating that this not an insurmountable obstacle but rather
more of an exercise).

Even same-frequency 'repeater' designs are VERY do-able as
in-band/on-channel such as active 'cell-extenders' manaufactured
by half a dozen different vendors. This style 'RF Repeater' DOES
require adequate care in laying out so-called  1) donor and
2) coverage antennas however ...

You would be surprised what a broadband amplifier capable of
60 to 70 dB of gain in conjucntion with a pair of simple yagis
(or a yagi and an omni) can do ...

Parsing the original poster's question "Any ideas on the rf repeater
design?" sparks additional questions in my mind as to whether he
is seeking an entirely RF solution to his problem or a deeper
'system-level design' solution involving some intelligent
"message-passing" and routing protocols ...

RF Jim


>
> split your frequencies up as if you were putting them on cells of a
> hexagonally shaped network object
>
> J
>

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2002\10\09@123222 by Dale Botkin

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I would again point to the AX.25 protocol and RSPF routing as an example,
but for a simpler scheme:

Each station has an address.

Each message has source and destination addresses, plus a variable length
list of digipeater addresses, as part of its header.

Any station receiving a message checks for its own address in the
destination or digipeater list, and if present it does NOT repeat the
message.

If the station doesn't see its own address in the destination or
digipeater list it adds its own address to the digipeater list and repeats
that message after a random delay, or beter yet a delay determined by its
own address.

Crude, but simple.  Of course if you have lots of digipeaters or long
addresses the packet may eventually grow too large to be practical, but if
you limit it to say 16 digis it should be workable.  You'd probably also
want a message number so the recipient could "remember" that it's already
seen a particular message if it gets digipeated by seveal other stations,
in whch case you may see it several times.

Lacking a routing protocol and other features, this would be extremely
"chatty".  I'd only recommend it for very low packet rate applications,
like a packet every couple of seconds or less if there will be many
stations involved.

Dale
---
We are Dyslexia of Borg.
Fusistance is retile.
Your ass will be laminated.

On Wed, 9 Oct 2002, [iso-8859-9] Ömer Yalhý wrote:

{Quote hidden}

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2002\10\09@123431 by Dale Botkin

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And having just sent the last message I realize I forgot to trim teh
original text.  Mea culpa, I'll be sure to send myself a nastygram about
that.  8-)

Dale
---
We are Dyslexia of Borg.
Fusistance is retile.
Your ass will be laminated.

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2002\10\09@124750 by Alan B. Pearce

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>And having just sent the last message I realize I forgot to trim teh
>original text.  Mea culpa, I'll be sure to send myself a nastygram about
>that.  8-)

And should it not also be moved to [EE]: ???

The thread lost it's PICness a while ago :)))

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