Spectrum support remains critical for industry’s 5G plans
With channel bands of several hundred megahertz expected to support 5G deployments, government regulators will need to be creative in providing resources
Spectrum remains one of the more challenging aspects on the road to “5G” deployments. With expectations of channel widths of hundreds of megahertz, government regulators are set to have their hands full in terms of freeing up the necessary resources to enable the 5G revolution.
In a move designed to bolster the development and deployment of 5G technologies, the Federal Communications Commission recently approved plans to open up nearly 11 gigahertz of spectrum above the 24 GHz band in support of mobile telecom services. As part of its July Open Meeting, the FCC adopted new rules as part of the “Spectrum Frontiers” proceedings to bring both licensed and unlicensed spectrum to market ahead of 5G standards. The spectrum is set to include 3.85 gigahertz for licensed use in the 28 GHz, 37 GHz and 39 GHz bands, and 7 gigahertz for unlicensed use across the 64 GHz to 71 GHz bands.
“These rules balance different spectrum access approaches, including exclusive use licensing, shared access and unlicensed access, in order to meet a variety of different needs and use cases,” the FCC noted in a statement. “The commission also adopted other flexible service and technical rules to allow new technologies and innovations to evolve and flourish without needlessly prescriptive regulations.”
In touting the spectrum plan, FCC Chairman Tom Wheeler touched on what he sees as a leadership position for the country moving forward.
“With today’s order, we are repeating the proven formula that made the United States the world leader in 4G: one, make spectrum available quickly and in sufficient amounts; two, encourage and protect innovation-driving competition; and three, stay out of the way of market-driven, private sector technological development,” said Wheeler in a statement. “Today’s order will make the United States the first country in the world to identify and open up vast amounts of high frequency spectrum for 5G applications. The big game-changer is that we are using much higher-frequency bands than previously thought viable for flexible uses, including mobile. The ability to use this high-frequency spectrum opens much bigger chunks of spectrum. Current blocks of licensed low-band spectrum are usually five to 10 megahertz in width. With 5G, however, we are looking at blocks of at least 200 megahertz in width. This will allow networks to carry much more traffic per user – gigabits of throughput instead of megabits. We’re talking about fiber-like capacity to wireless users. By opening up these higher-frequency bands, we are making available over four times the total amount of licensed spectrum currently available for mobile. And we’re not done. We’re asking questions about opening up a significant number of other bands.”
Those questions included the FCC adopting a Further Notice of Proposed Rulemaking seeking further comments on plans to apply the flexible-use service and technical rules to an additional 18 gigahertz of spectrum across eight additional high-frequency bands, as well as comments on “refinements to the performance requirements and mobile spectrum holdings policies, and the sharing framework adopted for the 37-37.6 GHz band.
While there is a significant quantity of high-band spectrum set to be unleashed for 5G, the quality of that spectrum for commercial use is still up in the air. Thomas Keathley, SVP of wireless network architecture and design at AT&T, noted potential performance degradation issues connected with using the millimeter wave spectrum bands expected to be central to 5G networks.
“If you put a hand in front of a transmitter you will see degradation of performance,” the AT&T exec explained during a panel discussion at the recent CTIA Super Mobility event. “It’s going to be a very different implementation than traditional cellular networks.”
Adam Koeppe, VP of access technology planning at Verizon Communications, noted that indeed propagation characteristics of high-band spectrum will be a challenge, those “issues are not anything news.” Instead he noted what is different is the use of beamforming and beamtracking technology that allows the use of those bands in access-type deployments.
“Our trials have been to take those out of the lab and into real world scenarios,” Koeppe said of the carrier’s 5G network trials.
While high-band spectrum is expected to play a significant role in the initial launch of 5G services, long-term planning is likely to require the eventual infusion of spectrum below 6 GHz in order to provide the necessary coverage for some use cases like connected cars and autonomous vehicles. The FCC’s ongoing 600 MHz incentive auction process is seen by some as key to providing the needed low-band spectrum support for 5G.
Wheeler has repeatedly cited the 600 MHz spectrum as key for 5G work, with the timing on having that spectrum available for commercial wireless services falling in line with plans for broader 5G deployments around 2020.
In addition to the 600 MHz band, Scott Mair, SVP for technology and engineering at AT&T, said 5G deployments could tap lower-band spectrum currently held by carriers as well as potentially use the 3.5 GHz band being opened up on a shared basis by the FCC. The 3.5 GHz band, which in the U.S. is branded under the Citizens Broadband Radio Service label, could also benefit from international harmonization efforts.
“Low band is going to be very important,” said Ian Wong, senior manager at National Instruments’ Advanced Wireless Research Group. “The FCC and other regulatory bodies have taken some good steps in the process in how they are looking at the 3.5 GHz band. Even existing spectrum in terms of 700 MHz, or any sub-1 GHz with advances in technology is going to be critical.”
One challenge that still remains to be settled in terms of 5G plans is the need of a new air interface. It appears the dominant opinion is that 5G deployments using spectrum below 6 GHz will likely continue to rely on current OFDM-based methods used for LTE, though higher spectrum bands could rely on a new model.
Karri Kuoppamaki, VP of network technology, development and strategy at T-Mobile US, said OFDM looks set to be the base air interface model, but that it “might not be the best for IoT down the road.”
Wong noted current work seems to indicate OFDM could be the air interface of choice for services up to the 40 GHz band.
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For more on the 5G topic, check out the RCR Wireless News Feature Report “Breaking down the 5G future.”