Voice over GPRS?

[Paul Wouters]

On Fri, 2 Feb 2007, Robert Michel wrote:

> Does anybody has experiances/ideas about Voice over GPRS?

See: http://www.cl.cam.ac.uk/~rc277/globe02.pdf

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.

Paul