Stations Ready for Mobile DTV Trials

At the same time that broadcasters are wrapping up the final pieces of their transition to digital television (DTV), they are also busy trying to create a new technical standard that will allow them to broadcast to mobile devices within their existing digital spectrum.

To a large extent, proponents of mobile DTV are working under the same deadline. Broadcasters would like to have a standard in place by Feb. 17, 2009, when analog broadcasts cease and the reclaimed spectrum is expected to be used by telcos and Internet companies to launch new wireless services.

Though it hasn't gotten as much attention as HDTV, many broadcasters see mobile DTV as a potentially lucrative new part of the business.

“Frankly, broadcast is the ultimate mobile delivery vehicle,” says Brandon Burgess, chairman of ION Media and the leader of a coalition of 800 stations that are trying to rapidly agree on a mobile DTV standard. “In some sense, doing DTV without the [mobile] component is a lot less exciting.”

True, Burgess says, getting digital signals into 113 million Nielsen homes is a technological feat, and with multicasting capabilities, the switch to digital has financial implications all by itself.

But, he says, “If you open up mobile, you open up another 400 million devices and places over the coming three to five to seven years that currently and historically have been unavailable to broadcasters. Mobile is the game-changing part of DTV.”

Field evaluations of three potential transmission systems for mobile DTV are slated to begin this week in the San Francisco/San Jose market. The three systems that will be evaluated for the performance of their transmission scheme, or “physical layer,” include MPH, developed by Harris Broadcast and LG Electronics; A-VSB, backed by Samsung, Rohde & Schwarz and Nokia; and a third system from Thomson and Micronas Semiconductor.

The field and lab evaluations, referred to as Independent Demonstration of Viability (IDOV), are part of the Advanced Television Systems Committee's (ATSC) formal process to create a new mobile and handheld standard.

But they are being conducted by the Open Mobile Video Coalition (OMVC) Burgess heads, which includes major broadcast groups such as Belo, Fox, Gannett, Gray, NBC/Telemundo, Sinclair, Tribune, Cox, Dispatch, Freedom, LIN, Meredith, Media General, Post-Newsweek, Raycom, Schurz and the Association of Public Television Stations.

The coalition, with some technical help from the Association for Maximum Service Television, will conduct field evaluations in the Bay Area into mid-March at NBC-owned KNTV, ION station KKPX and Cox-owned independent KICU. Then it will move to Las Vegas for more evaluations at three stations (yet to be determined) until the NAB show in mid-April.

The demonstration process is being overseen by Cox VP of engineering Sterling Davis, who is chairman of the OMVC's technical advisory group (OTAG). Davis doesn't consider the demonstration process to be a formal test, but instead describes it as a “big hoop for proponents to jump through” that the ATSC designed to weed out systems that only exist on paper, not in actual hardware. The ATSC is expected to conduct “full-blown” field tests later this year, he says.

But the IDOV field process is still technically rigorous. It involves hooking up prototype mobile DTV exciters to existing DTV transmitters and then using a van equipped with corresponding receivers to capture the mobile DTV stream on a data recorder. While each proponent was given a standard piece of video to encode and store on server, viewing the actual video on a prototype handheld device isn't part of the test. Instead, the data recorder will be used to measure signal strength, bit errors, equalizer performance and other transmission characteristics.

“The testing is all focused on the performance of the physical layer, and the ability to get bits from the station to a device,” says Harris Broadcast VP Jay Adrick. “There will be a receiver to watch video and listen to audio, but that's not the primary focus. They really want to capture data off the receivers, look at the signal levels and signal performance, and see how well the signal performs in terms of receiving data from the transmission point.”

The results will eventually get to the ATSC by mid-May, and that group is expected to make a decision on the transmission system for mobile DTV sometime over the summer. That keeps it on track toward specifying a complete standard by early 2009.

The Bay Area stations participating in the experiment have transmitters in three different locations, two in San Bruno and one near San Jose. The plan is for the stations to broadcast three different mobile streams simultaneously, with each mobile DTV system being evaluated for a couple of days on one transmitter and then swapped out for another one. The systems will keep rotating between the three stations over the next three weeks. Having multiple passes on each transmitter should ensure fairness by accounting for vagaries in reception that might be caused by weather or time of day, says Davis.

Of course, the IDOV evaluations have to be conducted without interfering with stations' existing digital broadcasts, which is no mean feat.

“We walk a fine line in OTAG,” says Cox's Davis. “Convincing stations to give us bandwidth gets to be pretty tricky, even on a Cox station.”