Posted on March 3, 2015 in ATSC News
The first element of the developing ATSC 3.0 standard is the Physical Layer, commonly thought of as the transmission system that a TV broadcaster will use to take advantage of the new standard’s benefits.
In his role as Chairman of the S32 Specialist Group, Luke Fay, a software systems engineer at Sony Electronics, is leading the process to evaluate the original 12 Physical Layer proposals which is now well along and working toward conclusion. Fay is also Vice-Chairman of TG-3, the Technology and Standards Group charged with developing the overall ATSC 3.0 standard.
Fay reflects on the process so far on the Physical Layer, and the next steps to reach Candidate Standard status for ATSC 3.0:
What’s happening with the Physical Layer?
We received a dozen proposals back in September 2013, and our Specialist Group has been reviewing many aspects of those proposals ever since. One thing that we’ve come to realize is that there should really be two pieces of documentation to describe the Physical Layer. We’ve named the first ingredient “System Discovery” to include a “bootstrap” signal that will act as synchronization. Future receivers will look for the bootstrap and lock on to that to determine how best to decode the channel. The bootstrap will point to other parameters and also the “preamble.”
What the heck is a “preamble”?
That’s basically a signal that describes what the frame contains, sort of a table of contents, so that that when you’re looking at a channel the system first will lock on to the bootstrap and then read the preamble to find all of the information needed to decode the payload, or program.
We’ve determined that the second ingredient is the physical layer standard itself. It has all of the details about what’s in a frame, how many physical layer pipes exist, details on the modulation order and coding rate, and other information. So the first ingredient has instructions on how to find information, and the second piece is used to decode all of the details.
Are things on track for the Candidate Standard? And what’s the difference between a Candidate Standard and a Proposed Standard?
There a lot of work underway, and I think we’re on track to move along to a Candidate Standard of the entire system later this year. Once that’s done, those who would implement the details will have a chance to build equipment and test the Candidate Standard in a real world environment. That’s where all of the poking and prodding will be done with the elements of the system. It’s a trial of new technology, and a chance to see if anything was overlooked when developing the standard. Then, the process will move to a Proposed Standard that will be balloted. Once approved, ATSC 3.0 will be done.
How many people and organizations are working on it?
There are a variety of organizations that are working on ATSC 3.0 from all aspects, with literally hundreds of volunteers from around the world. All walks of life are involved – broadcasters, universities, consumer electronics companies – all working to find the solution that works best for everyone, especially consumers.
Of course, broadcasters want a very flexible system. As we all know, the amount of available spectrum is likely getting smaller. Broadcasters want the ability to maneuver and change over time. Technology continually advances. So we’re working to strike a balance between what the CE industry can implement in the near future and enabling a path forward to longer-term evolution as technology continues to advance. Flexibility is important, but it’s a very delicate balance.
We’re all working together to make sure that something is usable. The fact that we have this “bootstrap” signal (a relatively new development) has addressed many concerns. It establishes the minimum requirements, starting with a standard definition signal and then providing a path to move up to HD or Ultra HD or to mobile.
We have many representatives involved in all our committees, and our discussions are continuously underway. Some of our subcommittees are meeting twice a week!
How does it all come together?
Well, there’s the Physical Layer specialist group that meets weekly and it’s also split into four separate ad-hoc groups –looking at the front end of ATSC 3.0, looking at framing and waveform development, and considering the core broadcast TV service and what will likely happen with coverage maps. We’re exploring how far the signal will travel, what kind of power levels will be required, and how adjacent channel interference will be addressed as channels are packed closer together. Proposals are made and new technologies are evaluated, cross-checked, and then discussed with the larger group. It is a lot of work.
And how is the process different than it was 20 years ago with ATSC 1.0?
While I wasn’t involved two decades ago, some of my Sony colleagues were. The difference now is not so much in personalities and opinions as it is with the international scope of this work. We’re no longer solely focused on the 6-MHz channel for the U.S. There are additional considerations with a more flexible standard that may find applications throughout the world. So it may sound like evaluating proposals isn’t hard to do, but in fact it takes a lot of time and a lot of work to get the job done right.
Posted in ATSC News
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