[ILUG] Help needed with VOIP & Digital Phone

[Kevin Brennan]

Michael Watterson wrote:
> 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.
>>
> Did you try calls from DSL without the 3G user explicitly connecting 
> first?
no
>> 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..
>
> It will get worse as more subscribers added. All my analysis is on 
> HSPA+ aka I-HSPA, which is the next level after HSDPA and HSUPA.
This depends on network planning, consumer demand and competition. The 
argument of 500x calls v data (not to mention SMS) is not necessarily a 
valid one for the future, call prices are dropping and the revenue model 
for mobile operators is changing (slowly), there's massive potential in 
ancillary revenue by providing mobile data - even if they have not yet 
figured out how to tap the resource as well as Apple yet - do you think 
your 99c Ryan Air ticket pays for the plane and fuel (or even the 30 
quid after taxes, cc charges etc. are added) ?, no, a growing % of 
revenue comes from ancillary services (last estimate I read was €8.50 
euro's per passenger travelling). Point is, if there's large revenue 
from ancillary sources because consumers enjoy your 'broadband' 
experience then it's in your interest to supply it, and if your 
ancillary revenue is growing while your voice revenue is shrinking and 
the by product of that is VoIP works well then it's not all that bad 
..is it ?
>
> HSOPA is not 3G compatible. It's LTE now, different spectrum, 
> different handsets/Modems, different Licence and unlike HSPA, HSUPA, 
> HSDPA there is NO 3G compatibility on the air. You can't support 
> 3G/HSDPA devices on HSOPA channels.
>
Well..point is faster more efficient networks are coming .
> I've done extensive scientific tests of many Mobile Systems (HSDPA, 
> EDGE, Flash-OFDM and IPW). You need to know the distance from mast, 
> the power settings of base that controls cell size, if it's an 
> isolated cell or has adjoining cells, number of users and what they 
> are doing and where, or else all you have is an anecdote.
>
> At the minute it's slightly easier to get a workable VOIP call than 
> throw a six (about 1:5 chance). It only gets worse as customers added. 
so about the same as eircom DSL ;)

> Since Data application costs x500 the voice for the Operator, the cell 
> planning and density of subscribers per mast is based on phone usage 
> not data usage. Voice calls (3G & GSM not VOIP on HSPA/EDGE) have 
> priority.
> Your results are anecdotal and not what you can base a strategy or 
> recommendation because of the variable nature of Mobile compared with 
> Fixed Wireless, DSL, cable or Fibre broadband.
>
Absolutely
> Yes, VOIP can work on HSDPA/HSUPA/HSPA+/I-HSPA, but with NO 
> reliability or consistency. Oddly EDGE2 (which we are not likely to 
> see) can do VOIP a bit better as GSM does not have the evil cell 
> breathe of W-CDMA, the underlying air interface of UMTS 
> 3G/HSDPA/HSUPA/HSPA+/I-HSPA.
>
> The Mobile companies make a loss or at best break even on Data 
> packages. The regular phone package pays for it. At best a sector 
> could support 10 VOIP calls, a bit sad compared to 3G voice call 
> capacity, and that assumes NO voice calls or other data streaming!
>
Since I'm not a specialist on the air interface for 3G I will refer to 
the Harri Holma and Antti Toskala book 
(http://books.google.ie/books?id=-xAlDHXpzxYC&pg=PA458&lpg=PA458&dq=Harri+Holma+and+Antti+Toskala++voip+hsdpa&source=bl&ots=xSZprhlMyT&sig=MuqC33OxTOZYjyHzhLvqP_O4-Fg&hl=en&ei=yS6xSZzgOtSujAf0m_3TBQ&sa=X&oi=book_result&resnum=5&ct=result)
"the maximum number of simultaneous users per sector per 5Mhz 
carrier"...."with HSPA release 7" ...is estimated to be "120 users" 
etc..etc..
.. then more on reasons why a flat architecture is of benefit...


/KB







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