yet another fantasy idea: nextel-like walkie talkie feature?

Mikko Rauhala mjrauhal at
Wed Dec 13 21:06:01 CET 2006

ke, 2006-12-13 kello 10:26 -0800, michael at kirjoitti:
> I suppose everyone is familiar with the Nextel feature that behaves a bit like
> a walkie-talkie. In summary, you can contact anyone within certian groups in a
> half-duplex (meaning only one talks at a time) push-to-talk like environment.

There's an S60 program and associated service that's in relatively wide
use; see eg.

> But given the data network, and our own community of brilliant and motivated
> developers, would it be possible to implement something like this?

But of course. The real question is, can we interoperate with Nokia's
offering, which would be nice. They apparently license the technology to
operators and they might be rather jealous of it. You know Nokia's
love-hate-relationship with openness...

Of course, even without interoperability with an installed base this is
a good idea. May often be cheaper and more practical than calling.

> Off the top of my head, one way to do this might be: Implement a server to
> keep track of phones using this service and their IP address. Phones check in
> with the server when their IP address changes. Then when someone wants to talk
> to someone else, they select the recipient and press "talk". Code on the phone
> connects to the server, gets the IP address of the recipient, opens a data
> connection to the recipient (either directly or through some proxy if
> necesary), and establishes the appropriate half-duplex voip connection.

That's pretty much it, except "voip" may be overstating it a bit; I
associate voip with real-time voice communications; as said, this is
more a voice message, and as such should be treated as a file. (Perhaps
one could transfer the files using HTTP, though the signaling might be a
bit kludgish; ah well.)

Also, one should facilitate the transfer of arbitrary other files in
this way as well (including, ta-dah, text messages, since SMS are
generally ridiculously priced). Also, a client should be able to set a
size limit on incoming data thinking of non-flat GPRS fees. Perchance
even have the option to store the bigger files/messages on the server to
be downloaded on demand.

And then there's the option of encrypting the files with gnupg while in

> Oh, and we reprogram the cool audio chip to reduce sound quality and thus
> bitrate to save bandwidth and decrease delays.

Rather use a generic low-bandwidth codec on the host CPU; Speex is free
and can go down to a mere 2kbps while giving the option of higher
bandwidths for higher quality when that is called for. (Or, if
interoperability with Nokia's thingy is an option, whatever they use...)
For latency, start transmitting the codec's output as soon as any is

Mikko Rauhala   - mjr at     - <URL:>
Transhumanist   - WTA member     - <URL:>
Singularitarian - SIAI supporter - <URL:>

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