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.

3 thoughts on “The Gigabyte Per Hour Call”

  1. 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.

  2. 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?

  3. 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…

Comments are closed.