900MHz packet radio?

Dieter Spaar spaar at mirider.augusta.de
Thu Sep 1 07:59:31 UTC 2011

Hello Paul,

On Thu, 1 Sep 2011 13:41:11 +0930, "Paul Gardner-Stephen" <paul at servalproject.org> wrote:
> So, as the open-source group with the most experience reprogramming
> baseband radios, what is the feasibility of creating a
> proof-of-concept using the types of phones you already work with to
> send and receive arbitrary data packets without reliance on a cell
> tower (even for time synchronisation)?

It depends a lot on what you want to use on the lower layers
(e.g. Modulation). The TI Calypso based phones have a built-in
GMSK hardware modulator, so it is GMSK. Also the symbolrate is
fixed to the one used by GSM.

Then there is the DSP which does the signal processing work. Its
again tied to the GSM standard (format of the burst and length).
It might be possible to put something else into the relativ small
RAM inside the DSP, but this could be a huge effort.

Besides that you have to modify the hardware of the phone (remove
a filter) so that the phone can receive another phone. But this
is probably the smallest problem of all.

Best regards,
Dieter Spaar, Germany                           spaar at mirider.augusta.de

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