T-Mobile 600 MHz study shows LTE can share channels with nearby TV stations

T-Mobile US (NYSE:TMUS) says its research shows that LTE networks could operate side by side with co-channel, broadcast TV signals even in some of the nation's most densely populated areas.

LTE services can operate "in the presence of co-channel, over-the-air television operations in geographically nearby market areas, even in a region as densely populated as the northeastern United States when sufficient terrain and distance separation exists," said T-Mobile in an ex parte filing with the FCC.

The filing referenced a Dec. 13 meeting involving T-Mobile legal and technology policy executives Kathleen Ham, Steve Sharkey and Chris Wieczorek, They met with numerous FCC leaders from the Incentive Auction Task Force, Wireless Telecommunications Bureau, Office of Engineering and Technology, and Media Bureau. Also participating were representatives of technical consulting firm Roberson and Associates, which prepared the study for T-Mobile.

The point of the meeting was to examine T-Mobile's research regarding co-channel and adjacent channel interference and consider ways the FCC might open up spectrum for cellular communications even when in-market TV stations are operating on nearby airwaves. T-Mobile's test results appear to support use of market variability in the band plan being designed the upcoming 600 MHz incentive auctions of TV broadcast spectrum. Market variability could come into play if the FCC recovers different amounts of TV broadcast spectrum in different markets.

T-Mobile's co-channel analysis looked at some 10,000 cell sites and 18 television stations in and around New York in a total of 19 Economic Areas (EAs). The operator said its analysis revealed that while "most broadband LTE cell sites in the New York EA would experience interference from in-market television stations, LTE cell sites outside of the New York EA would exhibit considerably less interference."

T-Mobile LTE TV station signal overlap

FCC service contours of 18 TV stations near New York City. (Source: T-Mobile / Roberson and Associates)

In fact, the operator found that cell sites in the majority of markets outside of the New York EA would be largely or entirely unimpaired as a result of co-channel TV operations inside the New York EA.

T-Mobile suggested it may be possible to "accommodate a small number of different regional band plan variations, where regional EA clusters have the same bandplan (sic)." The operator said this is not the most desirable scenario but may be necessary "if insufficient spectrum is recovered nationally in the incentive auction."

Some broadcasters have opposed the market variability approach, saying it would entail a host of engineering challenges and could produce harmful interference to broadcasters as well as wireless operators because the two groups would end up sharing channels in adjacent markets.

In comments and a presentation submitted last summer to U.S. Rep. Henry Waxman (D-Calif.), Rick Kaplan, executive vice president of Strategic Planning of the National Association of Broadcasters, contended that if channel 47 were licensed to a high-power TV broadcaster in New York and also licensed to a wireless operator in Philadelphia or New Haven, Conn., there could be significant interference between the services unless "significant mitigation techniques" such as large geographic separation between the services, were undertaken.

However, Preston Padden, executive director of the Expanding Opportunities for Broadcasters Coalition, said his group supports market variability. The coalition consists of more than 70 auction-eligible stations.

Although T-Mobile discussed licensing services based on EAs and regional EA clusters, the ultimate 600 MHz band plan might offer licenses for even smaller geographic areas. The Wireless Telecommunications Bureau is considering an approach advocated by the Competitive Carriers Association, which wants 600 MHz licenses to be issued for Partial Economic Areas (PEAs) rather than the larger EAs. The bureau is soliciting public input with comments and replies due next month.

For more:
- see this T-Mobile filing and this presentation
- see this CommLawBlog article

Related articles:
Stephenson: AT&T would accept limits to spectrum purchases during incentive auctions
FCC pushing 600 MHz broadcast incentive auction to mid-2015
FCC's Wheeler signals intent to let smaller carriers get more spectrum
Sprint, T-Mobile, Dish and others urge FCC's Wheeler to let them get 600 MHz spectrum
FCC's Wheeler promises to work with broadcasters ahead of incentive auctions
FCC's Wheeler to encourage competition, but mum on auction rules
T-Mobile, Verizon join forces on 600 MHz auction band plan

Article updated Dec. 29, 2013, to include input from the Expanding Opportunities for Broadcasters Coalition.

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