asterisk users - May 2004 - GSM v iLBC for low bandwidth connections

Hi All,

I've been playing with GSM and iLBC over low bandwidth connections
(central Asterisk box with 2mbps, to ADSL users on 512/256) and both 
seem to perform well. Based upon what I've read in the archives and
at voip-info.org iLBC should perform a little better if packets are 
lost, than compared to GSM. Do you find this to be true in practice, 
or is GSM just as robust?

Whilst I'm asking questions, in terms of sound quality would there be
a significant benefit in switching to g.729?

Regards,
Nathan.

> I've been playing with GSM and iLBC over low bandwidth connections
> (central Asterisk box with 2mbps, to ADSL users on 512/256) and both
> seem to perform well. Based upon what I've read in the archives and
> at voip-info.org iLBC should perform a little better if packets are
> lost, than compared to GSM. Do you find this to be true in practice,
> or is GSM just as robust?
I believe that iLBC has better MOS in lossy environments than all other 
protocols, period.  I use it exclusively now with the VOIP providers I use 
for LD.
> Whilst I'm asking questions, in terms of sound quality would there be
> a significant benefit in switching to g.729?
I have had *zero* voice quality issues with iLBC.  I have had voice quality 
issues due to links that were full, but that's not iLBC's fault.  The
only
reason I can see using g.729 these days is for low-bandwidth interoperability 
with commercial VOIP equipment that doesn't use iLBC.  Seriously.  The 
difference between 11-13kbps for an iLBC conversation vs 8kbps for g.729 is 
negligable to me.  Maybe if you had a thousand calls pumping out your 
connection, but then again the $10k you spent on g.729 licenses can probably 
buy a slightly faster link.  :-)

Regards,
Andrew

http://www.bkw.org/~brian/iax-gsm-vs-sip-g729.gif

Just an FYI

bkw
> -----Original Message-----
> From: asterisk-users-admin@lists.digium.com [mailto:asterisk-users-
> admin@lists.digium.com] On Behalf Of nathan
> Sent: Friday, May 14, 2004 6:32 AM
> To: asterisk-users@lists.digium.com
> Subject: [Asterisk-Users] GSM v iLBC for low bandwidth connections
>
> Hi All,
>
> I've been playing with GSM and iLBC over low bandwidth connections
> (central Asterisk box with 2mbps, to ADSL users on 512/256) and both
> seem to perform well. Based upon what I've read in the archives and
> at voip-info.org iLBC should perform a little better if packets are
> lost, than compared to GSM. Do you find this to be true in practice,
> or is GSM just as robust?
>
> Whilst I'm asking questions, in terms of sound quality would there be
> a significant benefit in switching to g.729?
>
> Regards,
> Nathan.
>
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