Video Calling and Upstream Bandwidth
by Leslie Ellis // October 11 2010
I’m not big on predictions, but one thing really does seem clear: Very shortly, we will all have the option, probably within arm’s reach, of talking on the phone while seeing each other.
Think about it: More and more PC monitors and laptops come with a built-in webcam. More and more smart phones come with cameras on the front.
Chances are high that even your mother has heard about, and probably used, Skype.
Then, last week, Cisco introduced a residential version of its “tele-presence” line, called “Umi” (pronounced “you me”). If you’ve seen the enterprise version, you know that it’s freakishly high in video quality. (As in, forget about multi-tasking during that long video conference call.)
Putting aside the matter of whether we really want to see each other every time we talk on the phone, there’s another consideration: Upstream bandwidth.
A brief refresher: Cable bandwidth is segmented into two chunks: Upstream and downstream. So far, the big work in bandwidth optimization is far more focused on the downstream path (toward homes) than the upstream (from homes.)
This makes sense, especially when you consider how many different ways operators need to carry the same networks. ESPN, for instance, might be carried in analog, standard definition digital, and high definition. It’s entirely likely that mainstream networks will be carried linearly in IP, too. So that’s each big network, potentially being carried four ways.
The good news is, optimizing downstream bandwidth is comfortably provisioned with options. These days, operators needing more shelf space (name me one that isn’t) respond by harvesting analog channels, recycling bandwidth using digital video switches, or building more bandwidth on the top (1 GHz.)
No such panoply of options exists for the upstream path, which represents about five percent of total available bandwidth. It’s completely hemmed in between 5-42 MHz.
This upstream squeeze issue isn’t new. Twenty years ago, a lot of the engine room talk was about building a second upstream path, way up high, around 1 GHz.
Today, the options to optimize the upstream are still pretty much the same as they were in the early ‘90s: Figure out a better modulation scheme that can survive down there (it’s noisy in the 5-42), move the spectral boundary above 42 MHz, or build a second path.
And with all these gadgets coming that let us see each other from far away, it’s probably time to dust off the options and try again.
This column originally appeared in the Platforms section of Multichannel News.