At the NAB Show in Las Vegas this week it was clear mobile DTV (MDTV) in the United States has made the move from an exciting new technology concept to a proven standard with real products for broadcasters. Last year Axcera, Grass Valley, Harris, and Rohde and Schwarz showed complete MDTV systems based on the proposed standard. This year they and other manufacturers, including Larcan and Screen Services, were showing complete MDTV systems compliant with the A/153 standard adopted in October. Unlike last year, most are available now.
Although ATSC is working on a standard that would allow an exciter from one company to work with another manufacturer's ATSC A/153 mobile DTV multiplexer, that isn't the case now. Transmitter manufacturers, in addition to the exciter, have to provide the multiplexer and many were showing encoders and signaling equipment as well, allowing "one-stop shopping" for everything needed to put a mobile DTV signal on the air. Broadcasters shouldn't have a problem finding a way to begin transmitting MDTV.
Every single-transmitter DTV station, unless the coverage area is flat with no high buildings, is going to have some areas where the signal will be too weak. For fixed TV sets, that isn't a problem – viewers can purchase cable or satellite subscriptions to view the signal. That isn't an option for MDTV, so it will be important to make sure viewers fill in coverage holes where there is significant population or where viewers are likely to want to view TV on their cellphones, smartphones, tablets or netbooks.
Filling in these coverage holes will require a distributed transmission system (DTS), a DTV translator or an on-channel digital repeater. While DTS is a proven technology, last year I found few ATSC MDTV echo-canceling digital on-channel repeaters (ECDOCR) at the show. This year there were several options. Axcera had a unit at NAB and Linear was showing a relatively low cost ECDOCR. Hutech had a wide range of products using ETRI echo-canceling technology. Of particular interest was their 60 mW "Pico Repeater" that could be mounted outdoors and repeat up to 5 channels – perfect for underground train stations and smaller shopping malls. Antenna manufacturers showed antennas to improve coverage, both high power and low power.
If consumers don't have a way to watch MDTV programs, what's the point in transmitting it? At the Mobile DTV Marketplace, a wide range of MDTV receivers was on display, ranging from USB dongles with dual ATSC and ATSC MDTV tuners to some beautiful handheld devices from Dell with 3.5- and 5-inch displays. With a screen size bigger than an iPhone in a more convenient package than the iPad, Dell's Mini-5 should be a hot product when it is released. I've reported on MDTV products from LG (USB dongles, cellphones, portable viewers, DVD players and netbooks) and Samsung (the "Moment" smartphone) before. Exhibitors told me some of these products would be hitting store shelves as soon as June, so we need to move quickly to get MDTV signal on the air!
I'll have more on this year's NAB, with a focus on antennas and on-channel repeaters, in my next RF Technology column in TV Technology magazine.
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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