Monday, August 14, 2006

Getting the IPTV Jitters

AT&T U-verse set-top box Apparently AT&T is having some problems rolling out its U-verse IPTV service (Light Reading - Video - AT&T Still Has IPTV 'Jitters' - Telecom News Analysis).  They are experience a loss of a couple of IP packets every minute which manifests itself as a short screen freeze or some pixelation.  It is not surprising that they are experiencing such problems with new technology comprised of a very complex delivery mechanism. 

Microsoft, their IPTV middleware provider, suggests modifying the UDP protocol that includes a resend mechanism if the set-top box detects a missing packet.  Won't that make UDP like TCP?  It seems that this non-standard workaround will not solve the problem unless signals are delayed even more than the quarter second that they are today.  If multiple requests for a resend are sent back to the headend at the same time, then this flood of traffic may create even more congestion problems.

The solution that AT&T engineers are pursuing seems a bit more pragmatic.  They are adding forward error correction (FEC) near the encoders to repair the damaged packets.  Whatever solution is chosen, the question remains as to the scalability of IPTV in large deployments.  End-to-end error free transmission through many network elements must be ensured for a high-quality picture to come through.

There is no doubt that the industry will figure out a solution, but implementing a solution in this multi-vendor environment will take some time.  Scaling IPTV nationwide is a very challenging engineering feat similar to the roll-out of nationwide long distance phone service.