Spectrum waste and digital must-carry

Thu, 07/31/1997 - 8:00pm
Walt Ciciora

His approach was very confrontational, not at all polite, and "in your face." He insisted that the NAB's position is that "must-carry" applies to digital television, and that there is no compromise on this.

What about viewers' (My!) rights?

I couldn't contain myself I had to ask a question. I asked about my rights as a viewer. I told him that must-carry forced out several of the channels on my cable system that I wanted, and instead, gave me two of each of the networks, and three of the public broadcasting stations. I told him that as a viewer, I was alarmed that he wanted to squeeze out even more of the channels I want, and put on digital signals which I can't even receive until I buy a very expensive receiver. And that receiver will cost me around $5,000 sometime around Christmas 1998, estimates Gary Shapiro of the Consumer Electronics Manufacturers' Association (CEMA), of the Electronic Industries Association (EIA). Because I use a VCR a lot (I have five of them), I'll need one or more digital VCRs as well. So until I'm willing to spend all that money on receivers, I will lose channel capacity. I asked Dr. Sherman who was looking out for my interests as a viewer in this regard. His response was that this was a complicated issue, and he'd be willing to talk to me afterwards. I told him I'd rather he answer the question during the session. He refused!

I also told Dr. Sherman that I thought must-carry has created a new monopoly. The broadcaster has carriage independent of user satisfaction with his product. In fact, the discipline of the marketplace is circumvented. No matter how poor the programming, no matter how few the viewers, carriage is guaranteed! While it is true that poor programming might cause the loss of viewers and even sponsors, it will not lose cable carriage. Even if the broadcaster's programming only serves to warm up terminating resistors, it must be carried!

This all seems like an incredible waste of cable spectrum space and the exclusion of programming viewers want. This offends my sense of fair play.

Robust digital signals

I dropped in at the end of another session called "The Great Modulation Debate," for a paper by Gary Sgrignoli titled, "ATSC Transmission System: Field Tests Results." These actual field tests dramatically demonstrated that digital signals can be much more robust than analog signals. Sgrignoli said that anywhere there was a usable, though very poor, analog signal, there was a perfect digital signal. Of 169 receive sites, Channel 6 in analog yielded satisfactory reception in only 36.6 percent of the locations, while the digital signal was satisfactory in 81.7 percent of the sites. Of 199 receive sites, Channel 53 in analog yielded satisfactory reception in 76.4 percent of the locations, while the digital signal was satisfactory in 91.5 percent of the sites. Now this is serious food for thought!

The ATSC Digital Television standard has two modulation formats: 8-VSB and 16-VSB. The 8-VSB format is intended for broadcast purposes and can carry one high definition TV(HDTV) program, or several (four or more, depending on video quality trade-offs) Standard Definition TV (SDTV) programs. The 16-VSB format is intended for cable carriage. It has double the program capacity, but not double the capacity for carrying bits. How is this possible? The answer is instructive. The cable spectrum is cleaner and has fewer distortions and sources of interference. So the number of signal levels can be increased, while the amount of digital error protection is reduced. Even though the total number of bits has not doubled, the number of them which are available for the carriage of programming has doubled. Fewer are required for error protection. So cable can carry two HDTV signals in 6 MHz, while the broadcast signal can carry just one. Also, cable can carry eight to 10 SDTV programs (even more with statistical multiplexing), while the broadcast signal can carry just four or five.

Now this is an argument that can be played in the other direction! When we consider SDTV, and look at the ATSC Transmission System, we see that there is defined a 4-VSB and even a 2-VSB format. These formats are even more robust than the 8-VSB. They can provide perfect digital signals in places where the analog signal is absolutely useless! The trade-off? Fewer programs! Maybe two SDTV signals or even just one but perfect in areas where no analog signal can go!

The rabbit ears solution

This leads logically to an alternate approach to the carriage of digital signals. If broadcasters utilize the full power of digital techniques, they can provide one or two standard definition TV signals to on-set antennas what we used to call rabbit ears in more locations than could have been served by roof-top antennas. That is, anyone who could have received an analog signal with a roof-top antenna, will be able to receive a perfect digital signal with rabbit ears, if the broadcaster utilizes the full power of digital signal protection rather than trying to cram in as many programs as possible. A significant benefit to the perceptive broadcaster: portable reception like never before. This portability is an advantage cable will likely never enjoy.

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