[ILUG] Help needed with VOIP & Digital Phone

[Colin Rooney]

Kevin Brennan wrote:
> We made some preliminary tests using vodafone's USB dongle and VoIP was
> perfect.
> 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 speech.
> 
> 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.
> 
> /KB
> 
> 
> 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, but
>>>> the quality was pretty bad alright.  I could hear them fine, but the
>>>> other
>>>> side said that there was a delay and terrible echo.  Is it the e270
>>>> or the
>>>> o2 connection that you think the problem might lie with?
>>>>
>>>> Alan
>>>>     
>> 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!
> 

As someone who is condemned to mobile broadband for use at home, I can
agree that, from experience, voip on mobile is possible though not
reliable.  Now it might work great and in an hours time you cannot stay
connect for longer than 20 secs.  But it certainly can work and for long
periods with no issues.

Now I haven't read the terms and conditions for a while but I can
remember when I began using mobile 3g (with vodafone initially), the
terms and conditions of that contract explicitly forbade the use of
VoIP. I guess the mobile companies did not want to lose revenue from
potential mobile calls!?  Orperhaps the traffic from voip is to heavy?
I don't know, but the point I wanted to make was that while it may work,
if you plan to rely on it for your business then it may be prudent to
check your terms & conditions of use to ensure it is allowable.  As I
said it's been a while since I read these myself (I'm with o2 now) but
it was definitely not allowed in the early days of mobile 3g.

Colin