Application: push-to-talk VoIP (was: Voice over GPRS)

michael at michael at
Fri Feb 2 18:33:35 CET 2007

On Fri, 2 Feb 2007, Paul Wouters wrote:

> On Fri, 2 Feb 2007, Robert Michel wrote:
>> Does anybody has experiances/ideas about Voice over GPRS?
> See:
> They discuss tcp as well as udp performance over GPRS.
>> How long is the delay? It could maybe used for asyncron
>> voice communication Talk2Talk (instead of pushing a button)
>> By using 1KB/s for audio and some overhead, let
>> us say 2 KB/s 0.24Euro/MB = 24 Cent for 500 seconds,
>> 60 seconds makes then about 3 cents. When both using
>> this 6 cents. Hmm that would be interesting when
>> the user makes often make brakes/pause in their talk.
> Using speex, you'd need 1.6kb upstream. So bandwidth is not the
> issue. Latency is. The uplink will have between 0-1 sec of latency, so
> it's not really an issue . Downlink however, commonly has 2 or 3 second
> latency, ruining voice in an "interactive" way. In other words, you are
> probably forced to use a "push to talk" style conversation, meaning
> long monologues. And that is in good conditions, with a non-mobile
> connection. Things will get much worse when travelling, especially in
> the city with many small cells, as you'll be stuck hopping from cell to
> cell without actually getting much communication done.

This sounds technically feasible, and I for one would be interested in
pursuing this application.

I had the Nextel push-to-talk feature a long time ago, and found it very
useful, even with long latency, long monologues, and breaking up while hopping
from cell to cell.

This was brought up a long time ago on this list (perhaps during the first
month or so), and there was interest. I support revival of this feature.

I'll move this topic to the devel list and I'll add it to the wiki.

Is push-to-talk VoIP a good description of this?


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