How much data does a voice call use?
 

I've asked this before, but can't remember or find the answer. With roaming data rates really becoming MUCH CHEAPER, at least w. U.S. carriers, at some point it would be cheaper to use a wifi/data connection than a voice connection to make calls.

Eg. of lower rates:
In the U.S. the 2 biggest carriers (ATT and Verizon) used to charge about $20/Mb for data. Now they charge about $25-$30 for 130Mb of data. IOW, you now get about one hundred times more data for the same price.

you see different estimates,
e.g. https://support.skype.com/en/faq/FA1...y-mobile-phone
Skype claims about 1MB/min if calling a land/mobile number, 3MB if Skype to skype (on voice).
Other sites claim around 0.7MB/min.
so yes, this is often best with cheap data.

if you want landline-like quality usually VoIP uses the G.711 codec - which needs 80kbps up&down. That is 160kbps = 20kbyte/second = 1.2 MB/min

If you want cellphone like quality you can use the GSM codec which has roughly 15kbps up&down, 30kbps = 4kbyte/sec = 0,24MB/min

In normal VoIP clients you can set which codecs you want to use (this also depends which codecs your VoIP provider supports).

The betamax/finera brands for example support the following codecs:
G.711 (64 kbps)
G.726 (32 kbps)
G.729 (8 kbps)
G.723 (5.3 & 6.3 kbps)
GSMFR (13.2 kbps)
(calculate ~30% overhead for IP headers to the kbps rates)

I would be making use of T-Mobile's (U.S.) UMA wifi calling. I would create a "hotspot" with a data SIM in my Samsung Android tablet.


130Mb for $35 = 27¢/mb Which is Now the approximate roaming cost for data from U.S. carriers.

Using the figure - 1 minute of voice 1Mb of data - that would = 27¢ a minute which is a lot cheaper than the U.S. carriers charge for voice roaming. They charge $1/min in most EU and some other countries $2-$3/min. in places like China.

Eg. You can buy a 3Gb data SIM in China which works on a 3G network for $70. That's only 2¢/Mb. That means you could make calls at 2¢/min.!!
With the T-Mobile service - calls to/from U.S. numbers would not be additional. Calls to other countries would be charged at the usual T-Mobile rate for intl calls from the U.S. - but I would route those few calls via Google Voice - which can be done almost automatically.

Am I missing something?

Latency? Voice circuits are guaranteed a certain minimum speed and latency. Data circuits are not.

My wife is in Kuwait and is calling me every day VOIP over 3g over my Asterisks server. I am using the GSM codec and the call quality is very good. Most of the calls are completely over my server and never connect to the public phone network.

As far as i could find on google T-Mobile UMA is using the GSM codec anyway, so you will be at 0,24 MB/minute.

Chris

GREAT. The voice quality via UMA (assuming wifi is half way decent), is usually as good as via cell tower. TM's voice quality is as good as landline 90% of the time, hee.