In the land grab for spectrum, the most frightening specter is bandwidth-heavy media apps such as Netflix and YouTube. But as carriers launch their LTE networks and the devices that run on them, I’m concerned about their marketing efforts around HD video — both AT&T and Verizon are pitching it on their networks despite the fact that mobile video consumption can cause network congestion.
Video requires a lot of bits to make the moving pictures in such fine detail, and it’s also sensitive to latency and packet loss. Unlike an email that can be reassembled piecemeal at the end of its journey across the pipes and routers that make up the web, video packets generally have to travel in a preordained order. Adaptive streaming technologies can help break down video into smaller chunks to compensate for network quality, but video content is a essentially a linear stream. So with a lot of bits and a need for those bits to arrive in line, ISPs, be they wired or wireless, have to dedicate enough bandwidth to make sure the streams aren’t interrupted.
On wireless networks where bandwidth is limited by an operator’s spectrum holdings (you can always add more backhaul for a price, but spectrum is more challenging) video delivery can clog a cell site with only a few users. How few? Thanks to Steven Crowley, a networking engineer and consultant, I learned of a Motorola study that shows that a cell site could support up to 5 users that require a 1 Mbps stream. Halving the bit rate to 512 kbps supports 20 users, but as Crowley point out, ” but that’s not HD by any standard or convention of which I’m aware.”
So why are Verizon and AT&T (even MetroPCS) pitching HD video on mobile networks? The physics of the spectrum doesn’t support it, and from an economic perspective, the current pricing plans offered for cellular data make it expensive for consumers. And since I don’t see those pricing going down anytime soon, I’m puzzled. Joseph Ambeault, director of media and entertainment services for Verizon, told me that given the on-demand nature of video on mobile devices he believes that the network can handle it — especially given some technical tweaks that Verizon can offer.
For a look at those technical tweaks, Crowley offers a primer on cellular versus broadcast spectrum use– and notes that LTE supports broadcast technology. He also explains that the broadcasters are reworking their over the air transmission standard and may adopt a different technology. However, since most broadcasters are planning to use their existing airwaves for mobile television, and the FCC wants some of that spectrum back the technology built to support HD video suddenly becomes a matter of hot debate. So the question may become, which is the best way to deliver what consumers want when it comes to mobile video?
Related content from GigaOM Pro (subscription req’d):
- Mobile Q1: All Eyes on Tablets, T-Mobile and AT&T
- In Q4, Data Was Mobile’s Hot Spot
- Mobile Wrap-up: Q1 2009
