[ILUG] Help needed with VOIP & Digital Phone
alan at codecrunchers.ie
Fri Mar 6 22:17:08 GMT 2009
I'll have to give that another read to really get the details, but it sounds
very positive. I see those Thompson boxes are pretty reasonable, I'll have
to give it a shot now anyhow. I'll report back on my findings.
Thanks again for the depth of detail.
2009/3/6 Kevin Brennan <kevin.brennan at redsquared.com>
> We made some preliminary tests using vodafone's USB dongle and VoIP was
> USB dongle was connected to a router which accepts USB card which was to a
> Thompson Speedtouch 716 acting as an ATA.
> The far end voip device was a grandstream GXP2000 connected to a BT DSL
> line, codec was G729 - VoIP was peer to peer meaning we did not bring RTP
> stream onto our network.
> As I mention these were very preliminary, we only tested VoIP to VoIP calls
> (and to be honest I was very surprised at quality) we will be doing some
> more rigorous testing to see if we can consistent results.
> VoIP phones have built in echo cancellation (as do mobile phones) and calls
> to PSTN are likely to be very echo sensitive unless VoIP/PSTN gateways use
> aggressive hardware echo cancellation (which costs). You tend to get echo
> problems (to analogue phones) when ping times go over 50ms, in the TDM
> world national calls don't need echo cancellation as the round trip time
> would be sub 20ms, international destinations normally have echo
> cancellation as a longer round trip time is expected. It's different in the
> IP world where switches introduce delay and local call latency is dependent
> your hops to the ITSP you are using. My point here is that if the VoIP
> network is prepared for high latency then echo should not really be an
> issue, and the only symptom of the large round trip time is some delay in
> Packet loss and jitter are another thing, for the moment you will probably
> find hot-spots which can support VoIP well, but coverage will be limited.
> It's early days for VoIP over mobile broadband and I would expect we will
> see big improvements as demand heightens and networks improve with HSUPA,
> HSOPA etc..
> Anyway, I think it's a milestone when you can currently make a VoIP call
> over vodafone and quality is crystal clear with a package that only costs
> 25/month -even if it's limited in coverage. I think everyone (except the
> mobile operators) would welcome days when you could have free calls on your
> mobile with no roaming costs (yes, you can pick up a SIM in each country and
> keep the phone number) and keep your home phone number.
> Michael Watterson wrote:
>> Alan Ryan wrote:
>>> 2009/3/5 Alan Ryan <alan at codecrunchers.ie>
>>>> Hi Joerg,
>>>> The e270 is up and running, pretty reliable. Used a softphone today,
>>>> the quality was pretty bad alright. I could hear them fine, but the
>>>> side said that there was a delay and terrible echo. Is it the e270 or
>>>> o2 connection that you think the problem might lie with?
>>> The problem is Mobile Internet, not specifically O2 or the Modem.
>> It has 100ms to 2000ms latency, typically 150ms
>> High Jitter
>> speed varies from 0.050Mbps to 5Mbps +
>> Packet loss can be high or OK.
>> It's inherently unsuitable for VOIP. If more than about 10 people are
>> using your sector it's likely to be poor.
>> It's possible to get more consistent VOIP on 40Kbps dialup!
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