The Gigabyte Per Hour Call

Yes, bandwidth requirements are rising, especially when you have a big screen and lots of GHz available for things like high resolution video telephony. I use Skype video telephony quite often these days and when the other end also has a multi-megabit per second uplink available and a good camera, the video quality is just awesome and the stream easily exceeds one megabit per second in each direction. In other words, during a 60 minute video call, over 1 GB of data is exchanged.

Let's compare that to a mobile voice (only) call that uses a 12.2 kbit/s bearer for its codec over the air interface. 2 * 12.2 kbit/s * 60 seconds * 60 minutes / 8 bit = 11 MByte per hour. There's two orders of magnitude of difference here, i.e. a single high quality Skype video call uses the same bandwidth as 100 mobile voice calls! In fixed line networks, voice calls are usually transported in 64 kbit/s channels but the difference is still 1:20. And I imagine video telephony in full-HD resolution is not too far away anymore pushing the numbers even further.

Comments

[David H Deans]

Martin, do you believe that video communication will create demand for improved uplink speeds?

Currently, most broadband networks are optimized for downlink speeds. Even in wireline networks, symmetrical broadband access is rare -- perhaps the Asia-Pacific market being the exception.

[David Boettger]

Does this take into account the mobile device's screen size? Sure, if it's a notebook, then the screen size would be large, but if 12.2 voice is the benchmark, then isn't a handset-sized screen the proper normalizer? I'd guess that this would reduce the 1 Gbyte figure to something much less.

Another thought: DTX, AMR, and the fact that voice users don't usually talk at the same time would tend to make the average voice bit rate lower, driving the 1:20 ratio up much higher.

Maybe net-net, on a handset, the ratio is indeed something like 1:20?

[bernard]

Hi Martin,

Fair point regarding the difference in magnitude between mobile calls and video skype, but - do you think that all calls (in "the future") will be video calls?

I still wonder if people will want to have video-calls as default.

Either way, yes, bandwidth requirement are rising - I'm just not sure if they are rising for voice communications...