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Doug Lung Picks Apart Latest FCC Spectrum Analysis

ALEXANDRIA, VA.: Doug Lung, a well-respected veteran television engineer and long-time contributor to TV Technology this week combed through the FCC’s latest technical paper on reclaiming broadcast spectrum. The commission presented the paper to further its case for reallocating 120 MHz of broadcast spectrum for use in a national wireless broadband network. Lung came away underwhelmed...

“I have great respect for the engineers whose names are on the report. During the 40 years I’ve been involved with broadcasting, FCC reports were, with few exceptions, unbiased, accurate and complete,” he wrote in his weekly RF Report. “That is why upon critical reading I was so disappointed to find this attractively presented paper to be biased, incomplete, and, in some ways, inaccurate.

“Critical information is missing and conclusions are presented as fact when data doesn’t support them. The analysis glosses over data that refutes the National Broadband Plan’s recommendation for taking away broadcast spectrum and makes unjustified assumptions to support them.

“I’ll highlight a few examples, but urge you to read the document and draw your own conclusions.

“The paper notes that the FCC staff and contractors have been developing a new Allotment Optimization Model (AOM) to achieve the NBP’s goal of taking 120 MHz from the 294 MHz (240 Mhz) after removing three channels for land-mobile and television Chs. 2 through 6 currently assigned for TV broadcasting. Not surprisingly, when the model was used to see how much spectrum could be recovered by repacking existing full-power stations, only 6 to 42 MHz of spectrum was found to be available for reallocation, depending on inclusion or exclusion of border restrictions.

“The scenario did not move UHF stations to VHF or VHF stations to UHF. Cellular technology is briefly discussed but the only supporting data is Appendix A, which includes a graph showing 650 MHz versus 1900 MHz rural cell areas plotted against maximum allowable path loss in dB.

“It’s an example of the document’s tendency to present impressive-looking data with little relevance to the real world. In this case, multipath and self-interference are ignored, and the table is intended for rural areas, where there is less demand for both wireless spectrum and broadcast spectrum.

“Appendix D is a cut-and-paste of parts of FCC OET Bulletin 69, with half a page devoted to a now out-of-date table showing desired-to-undesired interference ratios for analog TV. A close look indicates that only three lines apply to DTV-into-DTV interference.

“Before you argue that many analog LPTV and Class A TV stations are broadcasting analog, that doesn’t matter in this report.

“There is a small section on LPTV stations, but as far as I can tell, they were not included in the studies. The paper repeats the NBP suggestions for ways to accommodate LPTV stations, but notes: ‘To the extent that a reallocation compresses the broadcast TV bands, non-Class A LPTVs may be forced to move, and therefore incur relocation costs, and they may find fewer available channels slots which they can occupy.

“Regarding wireless microphones and TV white space devices, the document says they must be considered, but states a consideration of any potential effects and solutions would be ‘beyond the scope of this paper,’ as it is intended to address ‘particular considerations’ that apply to full-power TV. In my opinion, with no available TV channels where most people live, the options for LPTV stations and wireless microphone users would appear to be limited at best.

“In fairness to the authors, there is some relevant and useful information in the document’s other Appendices. As an example, ‘Appendix C: Optimization Model Formulation’ provides details on the AOM used to determine the amount of spectrum reclaimed from repacking and channel sharing.

“One thing I found interesting was that ‘the model does not incorporate terrain conditions to determine the minimum allowable spacing between stations.’ Users can selectively relax spacing restrictions between pairs of stations in a DMA ‘based on an assessment of terrain or other considerations.’ No details are provided on how that would be applied objectively.

“Based on the results from the AOM repacking study, the paper suggests one way to clear half the broadcast channels would be to put two stations on one channel. Exhibit G shows the result of this study. If border restrictions are ignored, the Exhibit indicates that 120 MHz of spectrum can be taken from broadcasting if 204 stations share a channel. That may not sound like much, but is an example of where insufficient data is presented for readers to get a true understanding of the impact.

“Only 12 percent of the country’s stations sharing channels doesn’t sound like much, but the percentage would have to be higher in markets like Los Angeles and in areas in the Northeast where some stations had trouble finding a suitable channel for DTV after Chs. 52-69 were reallocated. In the scenario, some 707 stations--41 percent--would have to change channels. In addition, more than half of the stations would lose some service area.

“What is interesting is that if the amount of spectrum taken from broadcasting is reduced to 72 MHz--enough to protect active border allotments--only 38 stations would have to share a channel and another 392 would have to change channels.

“Without more data, it’s impossible to determine where those 38 stations would be located. The Exhibit shows that the portion of the viewers that would gain service from stations improving coverage is larger than the number of viewers losing service from stations with reduced coverage.

“Again, the limited data makes it hard to visualize what the real impact is. The stations gaining population may be those with limited power now, while the ones likely to be losing population could be the higher power, major market network affiliates--the ones also likely to have the most viewers.

“Look at these columns again, the ‘Without Border Restrictions’ numbers are a red herring. It seems unlikely the FCC would be able to ignore active border allotments when repacking the TV band. Unless the commission is suggesting that 120 MHz may be too much to take from TV broadcasting--which doesn’t seem to be the case--the ‘Active Allotments’ column is also a red herring.

“Where will the other 48 MHz come from?... (See the rest of Doug’s Most Excellent RF Reporting on the FCC’s “Spectrum Analysis: Options for Broadcasting OBI Technical Paper No. 3” at TV Technology. Scroll about halfway down the page to the break where this story continues.)