Google and the Wireless Internet Service Providers Association (WISPA) are touting the results of a study that shows the viability of introducing shared spectrum between satellite earth stations and point-to-multipoint broadband systems (P2MP) in the C-band.
Specifically, the results of the study, presented by Virginia Tech Professor Jeff Reed on Tuesday, demonstrate that exclusion zones of about 10 kilometers are sufficient to protect most fixed-satellite service (FSS) earth stations from harmful interference caused by properly engineered co-channel P2MP broadband systems.
Reed, who co-founded Federated Wireless, said he and his colleagues found that P2MP systems operating outside the exclusion zones could provide gigabit broadband access to more than 80 million Americans, particularly those in underserved communities.
Interestingly, Google’s spectrum engineering lead Andrew Clegg pointed to a statement made by FCC Commissioner Michael O’Rielly at the Wi-Fi Alliance event last month: “We no longer have the luxury of over-protecting incumbents via technical rules, enormous guard bands, or super-sized protection zones. Every megahertz must be used as efficiently as possible.”
Fixed satellite service (FSS) earth stations could be considered the poster child for super-sized protection zones, Clegg said. To put it into perspective, the protection zone for just one fixed satellite earth station is larger than 10 of the 50 U.S. states. The zones are based on rules that were put in place decades ago and haven’t been revisited since, he noted.
WISPA President and CEO Claude Aiken said his members are often constrained by the lack of spectrum in rural areas, and WISPA is a big fan of spectrum sharing, which is particularly applicable in the C-band. By creating more rational protection zones for these earth stations, those 80 million more Americans could be get access to faster internet services.
WISPA did some initial work with Google on the issue that showed spectrum sharing was possible and they could get even closer to existing satellite earth stations without leading to harmful interference. That led to the belief that coordinated sharing would be a good solution.
Sharing proponents note that the Federal Communications Commission (FCC) is looking at changing or expanding the use of the 3.7-4.2 GHz satellite downlink band, known as the C-band. Some portion of the band may be cleared of satellite operations and auctioned for flexible/mobile use. The remaining satellite operations will be repacked into a portion of the band that is not cleared, and the commission is considering allowing sharing between satellite earth stations and P2MP systems in this part of the band.
Part of the reason sharing is seen as so viable in the C-band is that the earth stations are fixed, so their locations are known, and a well-stocked database at the FCC could facilitate sharing relatively quickly and easily.