As the world races toward 5G, it's hard to argue with NYU Wireless' assertions that the FCC should move quickly to allocate new spectrum in the millimeter wave (mmW) radio bands. But the satellite industry, in particular, is raising concerns in the FCC's Notice of Inquiry (NOI) on the subject. It's worried about the Ka-band, for one.
Are their concerns enough to derail the proceeding? I asked Ted Rappaport, founder of NYU Wireless and a pioneer in mmW research, about that. "I don't see anything there to be a show stopper for the FCC to move forward aggressively with 5G mobile service rules," he told FierceWirelessTech earlier this week.
NYU Wireless acknowledges that satellite services do need to be considered and existing operations should be protected. There are many instances where sharing between mobile and satellite services can be managed. According to Rappaport, this is easy to do at mmWave frequencies, where antenna directionality will be used in both mobile and satellite services.
Rappaport points out some things to consider. First, satellite systems generally use very highly directional antennas because they need to overcome the slant path losses of rain and atmosphere, which can be many kilometers through the sky. This amounts to enormous power reductions at mmW frequencies, necessitating very highly focused high gain antennas at the satellite and ground station, he said. Therefore, satellite services use very directional antennas from space and use very directional antennas at the ground stations that are looking up at the orbiting satellite.
"This is very different from terrestrial mobile, where directional antennas will be beaming on the horizon, will use down-tilt at the base station, will have obstructions to the sky due to buildings and foliage, and will have beam patterns focused on the ground, and not beaming up toward the sky," he said. "The interference issues will be minimal, and very easy to manage at mmWave, since beam patterns will be in different, orthogonal directions for the two different services."
Secondly, Rappaport said, the distances involved with satellite communications require very directional antennas for satellites to use. The interference zones are well defined for incumbent satellite operators. "We know where they need to point and operate, both in spectrum and in space," he said.
In its comments, SpaceX is asking the FCC to be sure to consider future satellite networks--it's talking about launching some 4,000 small non-geostationary orbit satellites. These types of systems, however, will be way too spectrally inefficient for mobile use and will have to be used for broadcast or backhaul or feeder links, according to Rappaport. "These again will require very, very narrow beams for any non-geo satellite to be able to communicate to earth through all kinds of weather events," he said. "Again, the directional nature of the earth to satellite link, and satellite to earth link, make interference relatively easy to quantify for satellite systems."
He suggests that backhaul or feeder ground stations for satellite systems could be located in rural locations, where mmWave mobile user density would be light, providing further insurance beyond the orthogonal beams of the two services, and further assuring that no potential serious interference could exist between terrestrial mobile and satellite systems.
NYU Wireless notes that no commenting parties in the FCC's proceeding have given a cogent reason why the commission should move away from the 1987 precedent of not requiring technical standards other than interference-related ones. Such a policy was instrumental in making Qualcomm a major manufacturer in the world market, even though most standards groups did not think CDMA was practical, and look what happened to that company--clearly, a wireless industry success story if there ever was one.
It's possible that by opening up the mmW spectrum, the FCC could encourage new, innovative entrepreneurs in the U.S. market. According to its FCC filing, Angie Communications USA, a Netherlands-based privately held limited liability company, is considering investing about $18.5 billion in capex by 2021 to build three distinct, yet converged infrastructures: a 4G mobile broadband network covering 95 percent of the U.S. population; a 5G access network covering 85 percent of the U.S. population; and a 1 or 10 Gbps FTTP network providing 5 million connections throughout the U.S.
That little whopper of a network could get lost if the FCC shifts its spectrum policies from an unlicensed or light-licensed policy to one where it's all about selling spectrum at the highest price. "A shift in licensing/cost policy by the FCC could lead Angie to partly or even fully abandon its plans for the USA," CEO Neal Lachman wrote in the filing.
For the record, I haven't spoken with Lachman, so I don't know the pertinent details about Angie's plans. But there are other good reasons for the FCC to step on the gas pedal here.
In its reply comments, AT&T points out that there is no formal U.S. 5G initiative, whereas the European Union, China, Korea and Japan all have national 5G programs. The FCC has taken one step by initiating the NOI, but to aid the domestic creation of a 5G program, the commission should implement an effective spectrum regime that provides some certainty for investors.
Unlike 2G, 3G and 4G air interfaces, 5G will be a heterogeneous environment of networks relying on a variety of spectrum bands and technologies, AT&T noted.
International harmonization would be nice to have, but it's impractical to wait for it. The UK's Ofcom already started a proceeding with its Jan. 16 "call for input" on spectrum above 6 GHz for future mobile communications, a proceeding that is somewhat analogous to the FCC's NOI. Ofcom expects early decisions and actions will occur in the second quarter of 2015.
Asked how fast the FCC could make spectrum above 24 GHz available under a best-case scenario, Rappaport told FierceWirelessTech that he believes the commission can and should follow the model of Ofcom and set decisions and the framework for mmW spectrum availability by the third quarter of 2015. The FCC could at least move to allow incumbents to have immediate flexible use of their existing spectrum to try new mobile services within the next few months, he said.
I've said previously that the U.S. needs to step up to the plate and demonstrate a leadership positon when it comes to 5G. Yes, there are a lot of other big, looming issues, not the least of which is that gigantic thing known as net neutrality that's hitting the ground today. But if we don't move expeditiously, it's going to be too little, too late.--Monica