As evidenced by comments to the FCC’s inquiry on the use of spectrum above 24 GHz, there’s a lot of interest in this spectrum from just about every segment of the communications industry—except from broadcast and public safety/land mobile representatives.
Originally it was thought this spectrum would not be suitable to reach indoor devices. If you are wondering how such spectrum could be useful for mobile communications, comments on the FCC's “Spectrum Frontiers Notice of Inquiry” (NOI)—which have been posted on the commission's Electronic Comment Filing System (ECFS)—
from the New York Polytechnic University and attachments outline their research showing how it worked in Manhattan and Brooklyn. Comments from Samsung highlight that company's research and studies on sharing and compatibility between mobile broadband and fixed systems using the bands above 24 GHz.
At the 2015 CES, the word was that 5G deployments could start in 2020, only five years from now. There is some debate about what constitutes 5G; some see it as multi-Gbps data using spectrum above 10 GHz while others see it as an assortment of technologies that will include spectrum below 3 GHz. Obviously, how 5G is defined will determine how the rollout date is determined.
Looking at the comments filed in the NOI, I have a hard time seeing how any widespread commercial deployment can begin five years from now, although I don't doubt we will see some initial trials in a few markets soon after 2020. If the regulators and industry groups can actually provide what is essentially unlimited wireless bandwidth to consumers, it will have a huge impact not only on the wireless business but media distribution businesses such as cable companies and broadcasters. Most of the commenters say lower frequency (and, consequently, lower bandwidth/data rate) wireless networks will still be needed for wide area coverage. Perhaps there will be a role for broadcasters' wide area coverage, but it may be a lot different than TV or radio today.
Ericsson's comments urge the FCC to maintain focus on bands below 24 GHz as well as considering bands above 24 GHz for 5G. They state that in the near term, as mobile broadband evolves towards 5G, it will be deployed in spectrum below 3 GHz. Ericsson sees the bands from 10 to 30 GHz as more appropriate for the initial expansion of 5G beyond 6 GHz, noting that while research is underway to develop 5G technology for millimeter wave (mmW) bands, much work remains to be done.
Qualcomm's comments state, “These millimeter wave bands can be used as part of the 5G solution, but 5G services will encompass much more than just operations in these bands. Qualcomm envisions 5G services using low-band, mid-band, and high-band spectrum, all in concert with one another to deliver unparalleled forms of connectivity, not just in terms of capacity, data rates, and latency, but also in terms of the mode of connectivity (i.e., device to device, mesh, etc.), and the support of new device types, including drones, robots, and other industrial machines.”
CTIA, “the Wireless Association” representing wireless carriers, in its filing recommended use of an exclusive licensing framework as much as practicable. “Exclusive use licensing has proven to attract investment in mobile broadband while also sparking wide-spread innovation.” CTIA said that where spectrum is not easily used for mobile wireless services, it could be made available on an unlicensed basis. CTIA also asked the FCC to adopt out-of-band emission (“OOBE”) rules that are technology neutral and do not penalize carriers for using wider bandwidth technologies. “Establishing technology neutral rules will encourage a wide variety of services and technologies throughout the spectrum.” CTIA's filing did not include recommendations for specific frequency bands.
The Consumer Electronics Association, whose members are often competing for the same spectrum, outlined the basic principles the FCC should take in considering usage of the mmW bands in its comments. They note, “While the NOI mostly focuses on identifying mmW spectrum for licensed mobile broadband services, the Commissions should not foreclose the wide range of licensed and unlicensed uses for which the mmW bands are appropriate.” “The FCC should provide adequate protection to incumbents. CEA applauded the FCC for committing not to attempt to define, standardize or specify the characteristics of 5G service. CEA states, “There is no reason for the Commission to abandon its reliance on the marketplace particularly where, as here, technology development is in its early stages.”
CEA said the FCC must continue to play an active role as facilitator in the further development of mmW technology. “Waiting to issue a Notice of Proposed Rulemaking until industry is ready to deploy mmW technologies risks foreclosing opportunities. Consumer demand is growing too fast to have such a reactive approach and its associated delay. At the same time, given the rapid pace of development, the unique nature of the bands and the wide variety of anticipated uses, the FCC should refrain from foreclosing options too soon.” Like many of the commenters, CEA said international harmonization is crucial to enabling the most efficient deployment of next generation technology. CEA urged developing an ITU-R agenda item for the WRC-18/19 conference at this year's WRC-15, noting that while there is wide support for an agenda item to identify spectrum for 5G mobile services, the focus has been on spectrum below 6 GHz.
Domestically, CEA said service rules and licensing regimes should reflect the best use of the mmW bands and developing technology. CEA noted that mmW spectrum serves a supplemental role for service providers in urban areas and said it may have a role to play in service models that reach less densely populated areas as well. The realities of the band should dictate both the geographic scope of licenses and performance requirements. “Reliance on the marketplace and physics, rather than ungrounded regulatory requirements, will lead to the best uses of the available spectrum.”
Comments from the Fixed Wireless Communications Coalition (FWCC) point out “The implementation of '5G' services and the growing use of small cell technologies for data delivery will only further demand for Fixed Service wireless backhaul solutions.” Fixed Service wireless backhaul is already being utilized in millimeter wave (mmW) bands.” The comments point out that 71-76 GHz and 81-86 GHz bands are well suited for wireless backhaul and are already being used nationwide. FWCC also points out that FWCC filed a Petition for Rulemaking and revision requesting Fixed Service rules at 42-43.5 GHz band. FWCC notes, “In urban settings, backhaul antennas often must be small enough for installation on crowded building tops and towers. The 42/43 GHz band, with its short wavelength and correspondingly small antennas, is ideal for this application through a link-by-link licensing scheme with prior frequency coordination.”
The National Cable & Telecommunications Association urged the FCC to “ explicitly propose to permit unlicensed operations in a variety of bands above 24 GHz because: (1) unlicensed users are well-positioned to share with incumbents and new mobile licensees; (2) the millimeter wave bands have the potential to help existing networks meet growing demand and ease congestion; and (3) new unlicensed frequencies will foster new innovations and generate value for the U.S. economy.” NCTA is careful to point out that spectrum above 24 GHz would be an addition, not a replacement, for access to unlicensed spectrum at lower frequencies.
The WI-FI Alliance makes the case for extending the existing Part 15 rules to operations in the 64-71 GHz band and to add authorization for Part 15 devices to operate in the 70, 80, and 90 GHz bands and in the bands above 95 GHz where consistent with international allocations. The Alliance notes that there is work underway by an IEEE 802 task group to study the development of technologies that would target the use of 100 Gbps wireless communications for a variety of applications in the 60 GHz to 300 GHz frequency range, including server-to-server communications in data centers, wireless backhaul and front haul, chip-to-chip communications for multi-chip modules, and closed proximity point-to-point applications such as kiosk downloading and file exchange. See the Comments of IEEE 802 for more information the work IEEE is doing at mmW frequencies.
In its comments, the European Satellite Operators Association (ESOA) outlined why the FCC should focus on spectrum above 31 GHz for 5G mobile, away from the Ka-band spectrum used by satellite operators. ESOA noted that satellites often provide broadband access technologies. “Billion dollars of investment have already been spent on these satellite networks particularly in the Ka-band frequencies between 24 and 31 GHz. Regulatory certainty is required by Ka-band satellite operators and their service providers to enable sustainable and viable access to Ka-band spectrum. Similarly, access to 40-75 GHz V-band frequencies that are already allocated by the ITU to satellite services on a primary or co-primary services ought to be preserved.”
The ESOA comments include graphs from the European METIS that show more opportunities exist for future mobile 5G services in spectrum above 31.0 GHz than in the lower sub-mmW bands between 6.0 and 31.0 GHz. See the Comments of the Satellite Industry Association (SIA) for details on use of the spectrum above 24 GHz by satellites today and what's proposed for the future. SIA notes that “The satellite industry heavily uses the identified satellite bands today and will need these bands even more tomorrow.”
4G Americas notes that “global harmonization will be key in 5G deployment.” 4G Americas takes a close look at the challenges involved in 5G deployment in spectrum above 24 GHz, carefully noting that lower frequency spectrum is still required for wide area coverage and will be a key part of 5G. 4G Americas said “the FCC and NTIA must continue to collaborate with the industry to make more spectrum available in the mid-bands of 1-6 GHz.” It added that the industry will continue to invest substantial amounts in LTE networks and these 4G networks “have a robust roadmap of technological innovation available in the years ahead.” “Wherever feasible,” the comment say, “features being discussed as 5G requirements should be implemented as LTE-Advanced extensions, to enable the industry to provide services at the maximum efficiency and continuity for the consumer. The Commission should be aware that there will be ongoing enhancements in LTE-Advanced that will continue through 2018, and that significant breakthroughs in new radio transmission interfaces may be accompanied by a break in backward compatibility.”
ARRL, the national association for Amateur Radio, filed comments show the mmW bands allocated to the Amateur Service around the world. They also highlight Amateur Radio use of this spectrum, noting two point-to-point distance records at 75 GHz were established as recently as June 2014 and the amount of propagation research worldwide by Amateur Radio operators in the mmW bands is on the increase. ARRL urged international harmonization of mobile allocations in the mmW bands and “utilization of the ample current mobile allocations above 24 GHz.” This “will contribute to avoiding incompatibility between incumbent services and new 5G mobile services.”
ARRL suggested that “the mmW bands allocated to the Amateur Services are inappropriate for shared 5G mobile service as Amateur experimental operation in the mmW bands is largely itinerant, temporary fixed operation using exceptionally sensitive receivers and high gain, narrow beamwidth antennas in bands typically shared with other incumbent services.”
I've only discussed a few of the comments submitted in the NOI. To view comments from ViaSat, Verizon, Intel, EchoStar Alcatel-Lucent, Nokia, Google, O3b and others, see the FCC's Electronic Comment Filing System – Proceeding Number 14-177 filings.
The FCC has a lot of work to do before new spectrum can be allocated for 5G services.
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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