Re: ot: android VOIP over 3g ?

On Mon, May 16, 2011 at 15:20, Voytek Eymont <[email protected]> wrote:
>
> is anyone using VOIP over 3G ? successfully ?

Probably, and probably not; 3G networks are *not* well suited to this,
especially in the area of data latency.

> I've only had the Aphone (Atrix) a short time, and, trying to achieve a
> useable SIP VOIP over 3G, with less than stellar results.
>
> in limited testing, Skype (to PC, not landline) seems to work quite well
> (but I'd rather SIP than Skype)

So, like Google Voice, they typically route voice through the voice
channel, and only use data for signalling; the mobile service provider
then has the right equipment to package and ship voice to the Skype
infrastructure, and it handles the rest of the data moving.  (Until it
hits a mobile at the other end, using the reverse of the process. :)

> 3G codec preference:
> g729, g711a, g711u
>
> (not used)g727,gsm
> packet time 30ms
>
> should I try to increase the 30ms ?

It wouldn't hurt, but it wouldn't address the (problems I understand
to be) fundamental issue of data latency over 3G.

> 3G: 7500-4500kbps, 1200-800, 80-120ms

Yah, ouch.  The audible level for delay is on the order of 20 to 30
ms, end to end, and you have three times that on the 3G hop alone.

> is speednet test a reasonable way to 'asses' 3g quality, what else to use?

Not really, but it isn't worse than anything else.

> any tips appreciated, or tell me I'm wasting my time
> or do I forget SIP and just Skype ?

Mostly the later, unless your mobile service provider has SIP support
using the same sorts of shims.  FWIW, LTE/4G is supposed to be much
better designed for data latency, and to route all voice traffic over
the data layer, so it should be much better when you finally get
there.  (Theoretically.)

Daniel
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