Doug Lung /
12.30.2010 11:50 AM
Observations and Reckless Predictions
No year's end column would be complete without some reckless predictions for the new year. Here are a few of mine:
- • With the rollout of ATSC mobile DTV and Internet alternatives for premium cable TV content, the number of off-air viewers will increase as consumers see free broadcast TV and a fast Internet connection as a money-saving alternative to expensive cable TV and satellite plans. Tablets, such as the wildly successful Apple iPAD, will become yet another screen for viewing television programming. What remains to be seen is whether content to these devices will be transmitted via wireless broadband spectrum (multicast or unicast), or via local broadcasters' ATSC mobile DTV IP multicast. Thanks to MCV and the Mobile 500 Alliance, I think there's at least an even chance broadcasters will at least play an equal role in broadcast IP distribution.
- • Supporters of the National Broadband Plan's recommendation that 120 MHz of spectrum be reallocated from broadcast TV to wireless carriers will realize how difficult this will be from both economic (based on the AT&T/ Qualcomm spectrum deal) and engineering standpoints once they start drafting rules. Look for scaled back spectrum demands, at least in major markets. I may be an optimist, but based on more than 40 years experience in the broadcasting business, I can't see how it will work. However, I believe that broadcasters will lose spectrum, with major market LPTV licensees the most threatened. While I think there's a good chance that all TV channels above Channel 30 won't be eliminated, I'm not so sure about the channels above 40.
- • As much as the FCC would like to find a way to make DTV work on low-band VHF TV channels (so they can clear more UHF channels for wireless broadband), this won't happen in 2011. Noise levels in this band are so high and small antenna efficiency is so low, that the proposed power increases won't make a significant difference. I'm more optimistic about improving high-band VHF TV reception. However, coordinating power increases in congested markets will be difficult. One solution might be to allow VHF broadcasters to base interference calculations on the maximum power level victim stations would be allowed to operate at under the new rules, rather than their current authorized power levels. New technology, including fractal antennas and metamaterials, could allow more efficient small antennas, but the costs--at least in 2011--will be too high for consumer devices.
- • There is a move to allow use of alternative modulation for broadcast TV--see http://www.spectrumevolution.org/. I don't see this standing a chance of adoption for full power broadcast TV in 2011, and if the National Broadband Plan's recommendations are adopted, there won't be any spectrum for LPTV in the larger TV markets. While the number of households depending on off-air TV reception is small, I'm sure there are many portable TV sets that aren't being counted. Ten percent the U.S. population is still a large number. The FCC won't want to obsolete that group's television sets. Beyond 2011, should Mobile DTV become the majority user of TV broadcast spectrum, I can see a scenario in which the FCC would allow broadcasters to move to more efficient encoding technology (H.264) for off-air HD delivery, while retaining a legacy standard-definition MPEG-2 channel for viewers with older TV sets (and/or converter boxes) for some period of time. Through the use of scalable video coding (SVC), broadcasters could transmit a signal that would be receivable under difficult conditions at lower resolution on portable devices, yet have the ability to provide the additional data needed for a high-definition picture in less challenging environments. As older sets become obsolete, provisions could be made to allow reception of alternative modulation methodologies in new TV sets. Before throwing out ATSC, it's important to remember that ATSC was optimized for single transmitting antenna and wide area coverage at lower carrier-to-noise ratios than COFDM. Receiver improvements now allow ATSC to work in difficult multipath environments. Guard band intervals limit long echo rejection in COFDM systems and high power transmission is more difficult, due to the higher peak-to-average ratio of COFDM as compared to ATSC's 8-VSB.
- • Distributed transmission systems (DTS), also called single frequency networks (SFN) have been around for a few years, yet we have let to see widespread adoption of the technology. As the Mobile DTV roll-out advances, expect this to change. I'm not sure that it will happen in 2011, but I do expect to see on-channel repeaters filling in shadows in urban areas and in densely populated areas blocked by terrain. Stations wanting Mobile DTV coverage in large malls or underground train stations will also find they need to put their signal on the area's distributed antenna system (DAS). That said, I don't see large numbers of low power DTS/SFN transmitters being used to replace single high power transmission sites for provide primary coverage. The interference issues, as Charlie Rhodes has covered in his TV Technology columns, are simply too great.
- • Long time readers will recall that for a number of years I've been predicting that high-speed broadband portable Ka-band uplinks would provide a low cost substitute for conventional SNG and ENG in remote areas. So far, Ka-band satellite operators have focused on using their spectrum for distribution of HDTV content more than broadband. However, now that companies such as LightSquared are rolling out combination terrestrial/satellite 4G services, part of my prediction may come true, although on frequencies quite a bit lower (1.6 and 2 GHz).
The New Year is likely to be another busy one for those of us still working in the TV broadcast engineering field, and that's a good thing! Here's wishing all RF Report readers a busy and prosperous 2011 and a healthy, robust and growing TV broadcast business.
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