THE PUBLIC INTEREST SPECTRUM COALITION GHz...Wi-Fi offloads the vast majority mobile network data...
Transcript of THE PUBLIC INTEREST SPECTRUM COALITION GHz...Wi-Fi offloads the vast majority mobile network data...
Before the
Federal Communications Commission
Washington, DC 20554
In the Matter of )
)
Unlicensed Use of the 6 GHz Band ) ET Docket No. 18-295
)
Expanding Flexible Use in Mid-Band Spectrum ) GN Docket No. 17-183
Between 3.7 and 24 GHz )
To: The Commission
REPLY COMMENTS OF
THE PUBLIC INTEREST SPECTRUM COALITION
NEW AMERICA’S OPEN TECHNOLOGY INSTITUTE
PUBLIC KNOWLEDGE
AMERICAN LIBRARY ASSOCIATION
SCHOOLS, HEALTH & LIBRARIES BROADBAND (SHLB) COALITION
BENTON INSTITUTE FOR BROADBAND AND SOCIETY
CoSN – CONSORTIUM FOR SCHOOL NETWORKING
NATIONAL HISPANIC MEDIA COALITION
TRIBAL DIGITAL VILLAGE NETWORK
INSTITUTE FOR LOCAL SELF-RELIANCE
NEXT CENTURY CITIES
COMMON CAUSE
ACCESS HUMBOLDT
X-LAB
July 27, 2020
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Table of Contents
I. Introduction and Summary 3
II. The Record Clearly Supports an Increased Power Level for Indoor-Only Devices 5
III. The Record Reflects Strong Support for Authorizing Client-to-Client Connections 10
IV. The Record Shows Strong Support for the Authorization of Very Low Power
Devices Across the Entire 6 GHz Band at Power Levels Up to at Least 14 dBm 12
V. The Record Supports the Authorization of Mobile Standard-Power Operations in
the 6 GHz Band 16
VI. The Commission Should Authorize the Use of Directional Antennas 18
VII. The Commission Should Not Impose a Preclusive Out-Of-Band Emissions
Restriction for the 5.9 GHz Band 18
VIII. Conclusion 21
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Before the
Federal Communications Commission
Washington, DC 20554
In the Matter of )
)
Unlicensed Use of the 6 GHz Band ) ET Docket No. 18-295
)
Expanding Flexible Use in Mid-Band Spectrum ) GN Docket No. 17-183
Between 3.7 and 24 GHz )
To: The Commission
REPLY COMMENTS OF
THE PUBLIC INTEREST SPECTRUM COALITION
The Public Interest Spectrum Coalition (“PISC”) – comprising New America’s Open
Technology Institute, Public Knowledge, the American Library Association, the Schools, Health
& Libraries Broadband (SHLB) Coalition, National Hispanic Media Coalition, CoSN–
Consortium for School Networking, Benton Institute for Broadband and Society, Next Century
Cities, the Institute for Local Self-Reliance, Tribal Digital Village Network, Common Cause,
Access Humboldt and X-Lab – hereby submits Reply Comments in response to parties filing in
response to the Further Notice of Proposed Rulemaking (“FNPRM”) in the above-captioned
proceedings.1
1 Unlicensed Use of the 6 GHz Band; Expanding Flexible Use in Mid-Band Spectrum Between
3.7 and 24 GHz, Report and Order and Further Notice of Proposed Rulemaking, ET Docket No.
18-295 and GN Docket No. 17-183, FCC 20-51 (rel. Apr. 24, 2020) (“Report and Order” or
“FNPRM”). All citations to comments below were filed in this docket on June 29, 2020, unless
otherwise noted.
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I. Introduction and Summary
In April, the Commission took a historic first step toward enabling the next generation of
Wi-Fi technology that will accelerate the availability and affordability of 5G-quality applications
and services to all Americans in every part of the country. With the right set of rules the
Commission can ensure the 6 GHz band is used to its fullest potential, creating both the world’s
most robust 5G wireless ecosystem and helping to bridge the digital divide. Accordingly, in these
reply comments, PISC describes how the record supports a number of additional provisions:
First, and most critically, the record reflects clear support for authorizing low-power,
indoor-only (LPI) devices at a power spectral density of 8 dBm/MHz across all 1200 megahertz
in the 6 GHz band. A wide variety of stakeholders joined PISC in observing that the technical
studies in the record clearly establish that a PSD limit of up to 8 dBm/MHz will not create a
substantial risk of harmful interference to incumbent operations. Authorizing LPI devices to
operate at this modestly higher power level across the entire 6 GHz band is necessary to ensure
that the public interest benefits of next generation Wi-Fi—including multi-gigabit capacity and
low-latency—is fully available and affordable in every home, business, school and library in the
country. Maintaining a PSD limit of 5 dBm/MHz will almost certainly deny the benefits of next
generation Wi-Fi to the typical home and small business.
Second, the record reflects support for the authorization of client-to-client connectivity.
Client devices should be allowed to intercommunicate when they are both within range of an
authorized 6 GHz access point. Doing so will unlock a wide range of important use cases for 6
GHz Wi-Fi, including for education, health care, industrial and mobile workforce use cases.
When clients are both sufficiently close to the access point, client-to-client connectivity is
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extremely unlikely to cause harmful interference to incumbents, especially indoors, due to the
close proximity between the clients interconnecting for these sorts of applications.
Third, the record demonstrates overwhelming support for the Commission to authorize
the use of Very Low Power (VLP) devices across the entire 6 GHz band. However, merely
authorizing this new class of VLP devices is meaningless if the technical rules are not robust
enough to facilitate the potential innovation and consumer welfare possible in a 5G wireless
ecosystem. PISC urges the Commission to authorize a power level of 21 dBm EIRP – but in any
case a power limit no lower than 14 dBm EIRP (1 dBm/MHz power spectral density).
Fourth, the record shows strong support for the Commission to support mobile standard-
power operations. Authorizing mobile access points under the control of an AFC is no more
technically difficult than for fixed APs. Conceptually, the rules can parallel those the
Commission has proposed for TV white space devices (“WSDs”). The record supports an
authorization for mobile standard-power operations with an EIRP limit of 36 dBm.
Fifth, the record demonstrates strong support for the use of directional antennas. The
Commission should both permit and encourage AFCs to take account of antenna directionality in
order to make the most efficient use of this spectrum. The directional characteristics of antennas
can readily be incorporated into AFC calculations. Controlling the interference footprint of usage
can significantly increase the capacity of the band for both directional and non-directional users.
Finally, the Commission should reject proposals to increase the out-of-band emissions
(OOBE) limit at the bottom of the 6 GHz band. PISC strongly objects to any reconsideration of
this issue. The Commission considered and decided this matter in the Report and Order and did
not seek comment on a change. The auto industry’s proposal reinforces the need to relocate
future auto safety applications, particularly C-V2X, to another band such as the lightly-used 4.9
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GHz public safety band. C-V2X should not be wedged between the current and future most
valuable and intensely used bands for high-capacity Wi-Fi. Relocating future auto safety
communications would achieve a win-win-win for broadband users, the automotive industry, and
5G mobile carriers.
II. The Record Clearly Supports an Increased Power Level for Indoor-Only Devices
The record shows strong support for increasing the power spectral density (PSD) limit for
LPI devices from 5 dBm/MHz to 8 dBm/MHz across all 1200 megahertz in the 6 GHz band. As
PISC stated in its Comments,2 a wide variety of stakeholders observed that the technical studies
in the record clearly establish that a PSD limit of up to 8 dBm/MHz will not create a substantial
risk of harmful interference to incumbent operations in the band.3 Authorizing LPI devices to
operate at this modestly higher power level is necessary to ensure that the public interest benefits
of next generation Wi-Fi—including multi-gigabit capacity and low-latency—is fully available
and affordable in every home, small business, school, and library in the country.4
Wi-Fi is the circulatory system for broadband connectivity in the United States and an
input into the productivity of virtually every other industry. The availability and affordability of
gigabit-fast Wi-Fi 6 connectivity is also essential to supporting high-speed internet connections
2 Comments of the Public Interest Spectrum Coalition at 14-15 (“Comments of PISC”). 3 See Comments of Dynamic Spectrum Alliance (“Comments of DSA”); Comments of NCTA—
The Internet & Television Association (“Comments of NCTA”); Comments of Microsoft
Corporation; Comments of Qualcomm Incorporated (“Comments of Qualcomm”); Comments of
Apple Inc., Broadcom Inc., Cisco Systems, Inc., Facebook, Inc., Google LLC, Hewlett Packard
Enterprise, Intel Corporation, Microsoft Corporation, NXP Semiconductors, Qualcomm
Incorporated, and Ruckus Networks, a Business Segment of CommScope (“Comments of RLAN
Group”); Comments of Wireless Broadband Alliance (“Comments of WBA”); Comments of Wi-
Fi Alliance. 4 Comments of Microsoft at 4-7; Comments of the Wi-Fi Alliance at 14-15; Comments of DSA
at 6-10; Comments of NCTA at 8-14; Comments of Qualcomm at 5-8; Comments of WBA at 7-
8; Comments of RLAN Group at 56-61.
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in homes, schools, workplaces, and public spaces. This is particularly true indoors where more
than 80 percent of mobile device data is consumed. Wi-Fi offloads the vast majority mobile
network data traffic, a share that is expected to increase again substantially as consumers
transition to the higher-bandwidth applications and services that characterize 5G.
The high-tech industry coalition—Apple, Broadcom, Cisco, Facebook, Google, Hewlett
Packard Enterprise, Intel, Microsoft, NXP Semiconductors, Qualcomm, and Ruckus Networks—
are among the diverse range of parties that describe why this modest difference in PSD is so
important to end users: “The key differences between a 5 dBm/MHz and 8 dBm/MHz PSD limit
are (1) coverage area, (2) throughput in the covered area, and (3) a tendency to force traffic onto
the widest channels when narrower channels are sufficient.”5 According to technical findings
these companies put in the record, a PSD limit of 5 dBm/MHz would have serious adverse
consequences for households and small businesses in particular. They found that the lower PSD
limit reduces coverage range by 31-to-43% and throughput by 53-to-63%, on average.6 As a
result, “[u]nnecessarily limiting Wi-Fi coverage range means that users either cannot access Wi-
Fi in certain parts of their home, small office, or school, or that they must purchase, install, and
manage additional coverage extenders or access points.”7
For end users, the enormous social and economic benefits of Wi-Fi accrue
overwhelmingly to indoor use, especially at home. LPI connectivity will become the core value
proposition for next generation Wi-Fi only if the Commission chooses to authorize a functional
power level. PISC concurs with Microsoft’s prediction that LPI connectivity is much more likely
to be “deployed in residences and smaller businesses. Larger businesses and campuses which
5 Comments of RLAN Group at 57-58. 6 Ibid. 7 Ibid.
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currently rely on some form of managed IT services, either internally or externally provided,
may want to utilize standard power access points and clients. At first, though, until one or more
AFCs are developed and certified by the Commission, all entities may have a need to operate
LPI devices.”8
Accordingly, PISC fully agrees with the Wi-Fi Alliance that “[s]ufficient PSD for LPI
devices is necessary to ensure that American consumers realize the full benefits of the 6 GHz
band.”9 The Wi-Fi Alliance correctly explains why a PSD below 8 dBm/MHz would deprive
consumers—and especially lower-income families—of the full benefits of next generation Wi-
Fi: “Power levels enable the enhanced throughput and capabilities of Wi-Fi 6 to reach beyond
one or two rooms without the need for signal extenders or additional equipment. In contrast,
reduced PSD below 8 dBm/MHz, will lead to two main problems for consumers and businesses
who rely on Wi-Fi. First, those consumers and businesses will experience a loss of coverage
area. In particular, 5 dBm/MHz reduces coverage range by 31-to-43%. Second, they will
experience reduction in throughput in the area that remains covered. A 5 dBm/MHz limit reduces
throughput by 53-to-63%.”10
PISC also strongly agrees with the Dynamic Spectrum Alliance (DSA), which explains
that a PSD limit of 5 dBm/MHz for LPI devices would undermine future Wi-Fi use cases if there
are “locations within a residence or business where an indoor client device may not be able to
successfully communicate with the indoor access point to close the link, let alone with the
minimum throughput necessary for a high-performance application. Either consumers must
accept that certain parts of their residence or business can’t be used for 6 GHz Wi-Fi or they will
8 Comments of Microsoft at 5. 9 Comments of the Wi-Fi Alliance at 14-15. 10 Ibid.
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have to incur additional costs for purchasing and installing additional access points or extenders
to achieve the same WiFi performance that have come to expect today.”11
Some commenters argue that the threat of harmful interference is a reason for the
Commission to maintain a very restrictive low power for indoor use. However, as PISC and
other parties explained, the technical studies in the record establish that these fears are
misplaced. Most notably, the study submitted into the record by CableLabs clearly demonstrates
that a PSD limit of 8 dBm/MHz for LPI devices would not cause harmful interference to
incumbent operations in the 6 GHz band.12 In addition, in response to the FNPRM, CableLabs
filed the results of an additional technical study “that accounts for physical layer attributes of FS
links and looks at the impact to FS link SINR and link availability of introducing Wi-Fi
operating at a PSD of 8 dBm/MHz.”13 CableLabs specifically analyzed AT&T “Link 5,” which
the Commission found to be a more challenging case for LPI coexistence with incumbent fixed
links. This additional simulation demonstrated an “extremely low probability of FS SINR
dropping below the desired link level,” even when conservatively omitting variables regarding
FS operations that would further reduce the potential for harmful interference to FS from LPI
Wi-Fi at an 8 dBm/MHz PSD.14
As the Commission authorizes shared use to unlock unused spectrum capacity in
underutilized bands, incumbents predictably insist on absolute protection from even the most
remote chance of harmful interference. Even if 6 GHz incumbents had purchased exclusive
licenses at auction, rather than coordinating into this shared band at no cost, their claim that they
11 Comments of DSA at 7-8. 12 See CableLabs Dec. 20, 2019 Ex Parte; CableLabs Feb. 14, 2020 Ex Parte at 5-7; Comments
of DSA at 7-9; Comments of Microsoft at 6-7; Comments of RLAN Group at 59-61. 13 Comments of NCTA at 23-25. 14 Ibid.
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must be spared even the most remote risk of interference from more productive use of the band is
misplaced. The Commission itself acknowledged this in the 6 GHz Report and Order, noting that
the agency “is not required to refrain from authorizing services or unlicensed operations
whenever there is any possibility of harmful interference. Indeed, such a prohibition would rule
out virtually all new services and unlicensed operations, given that there is virtually no type of
RF-emitting device that does not have the potential for causing such interference if used
incorrectly.”15
Broadband users and our economy would be deprived of the enormous benefits of new
wireless technologies, such as Wi-Fi 6, if incumbents are allowed to insist on virtually no risk
rather than on an appropriate policy balance that also recognizes—in the 6 GHz band in
particular—that incumbent fixed wireless operators and broadcasters do not have exclusive
licenses and never paid for use of the spectrum.
Further, the Commission has the authority and capacity to address any instances of actual
harmful interference that might arise.16 PISC concurs with NCTA on this point:
In the unlikely event that harmful interference did occur, the Commission’s
existing Part 15 rules provide a process through which a licensee can raise and
resolve the issue, . . . Such concerns are routinely resolved today under the
existing process. To the extent that incumbents experience harmful interference
from LPI unlicensed devices in the 6 GHz band, the rules are clear that the
operator must “cease operating the device upon notification by a Commission
representative that the device is causing harmful interference,” and may not
resume operations “until the condition causing the harmful interference has been
corrected.”17
15 Report and Order at ¶ 146; Comments of NCTA at 25-26. 16 Comments of Nokia at 4-5; Comments of the Utilities Technology Council, American Public
Power Association, National Rural Electric Cooperative Association, America Gas Association,
and American Water Works Association at 9-11; Comments of AT&T at 11; Comments of CTIA
at 6-7; Comments of the National Association of Broadcasters at 2-5. 17 Comments of NCTA at 26-27, citing 47 C.F.R. § 15.5(c).
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III. The Record Reflects Strong Support for Authorizing Client-to-Client
Connections
The record reflects strong support for the authorization of client-to-client connectivity at
a sufficient power level to fuel the next-generation of connected devices such as immersive
technologies.18 Client devices should be allowed to intercommunicate when they are both within
range of an authorized 6 GHz access point. The record shows that doing so would unlock a wide
range of important use cases for 6 GHz Wi-Fi. When clients are both sufficiently close to the
access point, client-to-client connectivity is extremely unlikely to cause harmful interference to
incumbents, especially indoors, due to the close proximity between the clients interconnecting
for these sorts of devices and operations.
PISC agrees with Apple, Broadcom, Google, and Microsoft that client-to-client device
connections will be a practical necessity to realize the benefits of many important use cases for
LPI in particular. Prohibiting client-to-client communications would preclude a number of very
important and innovative use cases. This is notably the case for emerging digital education and
instructional applications that represent the next frontier of connected learning. The companies
note that the operations would “enable an instructor to stream high definition content directly to
students’ devices in a classroom setting and interact in real time. Such applications can
significantly benefit from a client-to-client topology so that they can be seamlessly deployed
without creating dependencies on a school’s installed AP infrastructure and without dramatically
increasing the traffic loads on that infrastructure.”19 End users should also be able to control, for
example, AR headsets from their smartphone while tethered to their home Wi-Fi router.
18 Comments of Qualcomm, Comments of Facebook, Comments of Apple, Broadcom, Google,
and Microsoft. 19 Comments of Apple, Broadcom, Google, and Microsoft at 11-12.
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Further, client-to-client inter-communication will need to play a major role in enabling a
robust AR/VR landscape that could be enormously productive in industrial, healthcare and other
settings outside the home. Apple, Broadcom, Google and Microsoft note that if the Commission
were to adopt rules that requires “all traffic to be routed through fixed AP infrastructure
unnecessarily,” it would force “companies deploying AR/VR/MR applications to purchase not
only an AR/VR/MR solution, but also fixed APs compatible with that solution.”20 This would
inevitably slow innovation, raise prices, and reduce the utility of peripherals for both mobile
workers and other end uers. As the Wi-Fi Alliance notes: “There are multiple use cases that
require client-to-client indoor connectivity (e.g., screencasting, wearables, monitoring, etc.) and
the current rule already provides for a regulatory mechanism that can ensure that all client
devices remain in close proximity to indoor access points (i.e., indoors). Specifically, client
devices are enabled to detect access point transmission in order to initiate probe requests.”21
The record supports a presumption that the very nature of client-to-client communication
makes it extremely unlikely to increase the risk of actual harmful interference for incumbent
operations. As Qualcomm explains: “Authorizing client-to-client communications indoors also
would allow clients a few meters away from each other to directly communicate at lower
transmit power levels, lowering any interference risk and conserving precious device battery
resources, and, at the same, allow the serving AP to conserve power, lower system interference,
and improve spectral efficiency by not requiring the AP to carry the communications between
the two clients.”22
20 Id. at 12. 21 Comments of the Wi-Fi Alliance at 19-20. 22 Comments of Qualcomm at 7.
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Even if the Commission remains concerned that a client device could move outdoors,
mitigation measures are feasible. Apple, Broadcom, Google, and Microsoft suggest that the
Commission could implement rules that authorize client devices using the 6 GHz band to
transmit data to a separate client device only if both devices receive a signal from a 6 GHz AP
enabling the transfer.23 In this scenario, if the client device receives an enabling signal, that
device would be allowed to transmit data using the same channel as the AP from which it
received that signal, and at the same power limit as a client device associated with that AP.24 As
the companies conclude: “Thus, two-way communications between client devices would only be
permissible if both clients receive such enabling signals or are associated with 6 GHz APs.”25
PISC concurs that this mitigation, if necessary at all, should be sufficient to ensure there is no
increased risk of harmful interference to incumbents.
IV. The Record Shows Strong Support for the Authorization of Very Low Power
Devices Across the Entire 6 GHz Band at Power Levels Up to at Least 14 dBm
The record reflects strong support among a diverse range of stakeholders for the
Commission’s proposal to authorize very low power (VLP) unlicensed devices to operate both
indoors and outdoors across the band’s entire 1200 megahertz unburdened by any requirement to
be under the control of an Automated Frequency Control (AFC) system.26 As PISC stated in our
Comments, it is crucial for VLP devices “to operate across all four 6 GHz sub-bands, both
23 Comments of Apple, Broadcom, Google, and Microsoft at 13-14. 24 Ibid. 25 Id. at 14. 26 See, e.g., Comments of the Consumer Technology Association at 5 (“Comments of CTA”);
Comments of the Wi-Fi Alliance at 3-9; Comments of DSA at 4-6; Comments of Wi-Fi Alliance;
Comments of Facebook; Comments of RLAN Group.
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outdoors and indoors . . . [in order] to ensure that the next-generation of 5G- and Wi-Fi-powered
use cases are able to thrive and benefit consumers.”27
PISC agrees with the Consumer Technology Association (CTA) that authorizing the use
of VLP devices across the entire 6 GHz band “would enable many exciting new innovations that
are on the cusp of market entry,” including “immersive AR/VR technologies with wide-ranging
use cases” and “important peer-to-peer use cases.”28 Commenters describe a wide range of
potential use cases that include not just enhanced information, communication and
entertainment, but also enhanced health care and disability applications. Facebook describes how
AR technology “has the potential to revolutionize how medical patients are diagnosed (and
ultimately treated)” and can also “provide transformative benefits to those with hearing or vision
impairments.”29 The Wi-Fi Alliance similarly observes that VLP devices can help “healthcare
information technology managers [to] meet the growing connectivity demands presented by both
healthcare staff and patients and their families.”30
However, merely authorizing this new class of VLP devices is meaningless if the
technical rules are not robust enough to facilitate the potential innovation and consumer welfare
possible in a 5G wireless ecosystem. Recognizing this, a similarly broad and diverse range of
stakeholders propose that the Commission should authorize VLP devices to operate at power
levels up to no less than 14 dBm EIRP (1 dBm/MHz power spectral density).31 Absent
affirmative evidence of any probability of harmful interference to incumbent operations, the
27 Comments of PISC at 5. 28 Comments of CTA at 5-6. 29 Comments of Facebook at 3. 30 Comments of the Wi-Fi Alliance at 3-9. 31 See, e.g., CTA Comments at 6-7; Comments of the Wi-Fi Alliance at 9-13; Comments of DSA
at 4-6; Comments of Facebook at 3-6; Comments of RLAN Group at 10-32; Comments of
Qualcomm at 3-5; Comments of Microsoft at 2-3 and 7-8.
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Commission should not consider adopting rules that limit the maximum allowed power to less
than 14 dBm for VLP devices in the 6 GHz band or jeopardize the future efficiency of this
spectrum band. PISC fully agrees with DSA that “[t]his very low power level combined with
factors such as body loss, itinerancy of VLP devices, and environmental clutter will allow the
small percentage of VLPs that are expected to actually operate outdoors at any given time to
share spectrum with incumbent services without causing harmful interference.”32
The record shows that a minimum power limit of 14 dBm is essential because body loss
is a significant source of attenuation for VLP devices.33 The high-tech industry coalition, for
example, demonstrates in a study by the Wireless Research Center that the total dynamic
position path loss between AR glasses and a user’s mobile handset in a 160 megahertz channel in
the 6 GHz band ranges from 26 to 96 dB.34 At the same time, a VLP device operating at 14 dBm
provides little risk of harmful interference to high-powered fixed links or other incumbents in the
band. As Facebook observes, a series of Monte Carlo simulations conducted by RKF
Engineering (the “RKF Report”), in conjunction with other technical analyses, “demonstrate that
VLP devices at power levels of at least 14 dBm EIRP will not cause harmful interference to 6
GHz licensed services.”35
32 Comments of DSA at 4. 33 See, e.g., Comments of Facebook at 4-6; Comments of Apple, Broadcom, Google and
Microsoft at 4-5; Comments of Wi-Fi Alliance at 11. See also Letter from Paul Margie, Counsel
to Apple Inc. et al. to Marlene Dortch, Secretary, FCC attachment at 5, ET Docket No. 18-295,
GN Docket No. 17-183 (Nov. 12, 2019); Letter from Paul Margie, Counsel to Apple Inc. et al. to
Marlene Dortch, Secretary, FCC at 1-2, attachment at 6, ET Docket No. 18-295, GN Docket No.
17-183 (Dec. 9, 2019). 34 See Comments of 6 USC, attachment B, Koichiro Takamizawa et al., On-Body Channel Model
and Interference Estimation at 5.9 GHz to 7.1 GHz Band, Wireless Research Center of N.C. at 1,
3 (June 2020) (the “Wireless Research Center Report”). 35 Comments of Facebook at 7, noting that the Commission has relied on Monte Carlo
simulations as a credible predictor in this proceeding. See 6 GHz Report and Order and FNPRM
at ¶ 127 (noting that “an approach based on Monte Carlo simulations would give a more reliable
prediction of the likelihood of interference”).
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The United Kingdom’s regulator, Ofcom, reached this same conclusion. In its final order
released on July 24, Ofcom authorized VLP for use outdoors and indoors at a maximum power
of 25 mW (14 dBm) EIRP in the 5925-6425 MHz band. The agency also authorized LPI in the
band at a higher power level (250 mW).36 Ofcom conducted its own interference modeling,
based on Monte Carlo simulations, to support this outcome. Ofcom “undertook coexistence
analysis (see Annex 2) to understand the possible impact of future RLAN devices in the 6 GHz
(5925-6425 MHz) band on existing fixed links in the UK.”37 Ofcom stated that although it
"found from our modelling that there may be some scenarios where the fixed link interference
criteria could be exceeded, most likely from a single high-power device located either indoors or
outdoors close to the fixed link receiver,” it concluded that “these scenarios are very unlikely to
arise in practice for several reasons.”38 Among those reasons is the reality that both proximity
and line-of-sight transmission into an incumbent receiver would be rare: “Higher clutter losses
from buildings, trees and other obstacles in populated areas would further reduce the chances of
interference unless the RLAN was located very close to the fixed link receiver.”39
PISC groups are concerned that even 14 dBm may not be adequate to support the
innovations possible on portable devices with Wi-Fi 6 connectivity. Accordingly, PISC urges the
Commission to go further and consider authorizing VLP device use at power levels up to 21
dBm. As Apple, Broadcom, Google and Microsoft detail, this modestly higher power level
would allow “portable devices to communicate with an associated device at higher modulations,
and thus higher throughputs and lower latencies, keeping the distance between devices
36 Ofcom, Improving Spectrum Access for Wi-Fi: Spectrum Use in the 5 GHz and 6 GHz Bands,
Statement, at 1, 31 (rel. July 24, 2020), available at
https://www.ofcom.org.uk/__data/assets/pdf_file/0036/198927/6ghz-statement.pdf. 37 Id. at 15. 38 Ibid. 39 Id. at 16.
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constant.”40 A higher limit would also permit “devices to maintain a minimum throughput or
latency level at farther distances or with additional clutter or attenuation.”41
V. The Record Supports the Authorization of Mobile Standard-Power Operations
in the 6 GHz Band
The record reflects strong support for the Commission to authorize mobile standard-
power operations with an EIRP limit of 36 dBm.42 PISC agrees with the high-tech industry
associations and other stakeholders that to optimize unlicensed use of the 6 GHz spectrum band,
the Commission should authorize standard-power access points for mobile applications under the
control of an AFC. Conceptually, there is no question that AFC’s are capable of calculating areas
that are safe for mobile access points under rules similar to those the Commission has proposed
for higher-power TV white space devices (WSDs) on mobile platforms.
PISC agree with Apple, Broadcom, Cisco, et al. that allowing mobile standard-power
APs to operate in the UNII-5 and U-NII-7 band segments “can unleash a wave of near term
innovation, from next-generation communications for commuters and students while in transit, to
vehicle-area networks that enable sophisticated data gathering and analysis, to providing
connectivity on demand in areas where deploying fixed APs may be impractical.”43 The
companies detail how authorizing mobile standard-power operations in the two bands would
promote next-generation connected services for internet access on public transit, unlicensed
mobile connectivity uses for the agriculture and construction industries, and mobile Wi-Fi mesh
40 Comments of Apple, Broadcom, Google, and Microsoft at 5. 41 Ibid. 42 Comments of the Wireless Broadband Alliance at 3; Comments of DSA at 10-19; Comments
of Microsoft at 12-16; Comments of the Wi-Fi Alliance at 15-17; Comments of RLAN Group at
32-56; Comments of ACT—The App Association at 7. 43 Comments of RLAN Group at 33.
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systems for a wide range of uses such as mining, oil and gas, and other operations covering large
areas.44 Microsoft elaborates on how the higher EIRP level permitted for a standard power
access point can fuel mobile enterprise use cases such as “providing connectivity on campuses,
farms, construction sites, maritime ports, airfields, rail yards, and buses routes.”45
The record shows strong evidence that the Commission should not worry about harmful
interference from mobile standard-power operations due to the ability of an AFC to map
protection areas that ensure incumbents are as safe from interference as they would be vis-à-vis a
static AP. PISC agrees with the Dynamic Spectrum Alliance that “[a]n AFC system will ensure
that mobile standard power access points present a minimal risk of harmful interference to the
microwave fixed link receivers operating in the U-NII-5 and U-NII-7 bands.”46 PISC agrees with
Apple, Broadcom, Cisco, et al. that there is precedent for relying on a geolocation database:
The Commission has already authorized personal/portable white space device use
not only on frequencies allocated to broadcast television, but also on frequencies
allocated for public safety and other mobile licensed use based on the
Commission’s “high degree of confidence that the databases can reliably protect
[these] operations,” because “[p]ersonal/portable devices [that] rely on database
access to determine their list of available channels … can protect [incumbents] in
the same manner as fixed devices.”47
PISC also agrees with Microsoft that because “there are important technical and operational
differences between personal/portable WSDs and the services envisioned for mobile standard
power access points, only the relevant portions of the personal / portable WSD rules should be
considered.”48
44 Id. at 33-44. 45 Comments of Microsoft at 12. 46 Comments of DSA at 11-12. 47 Comments of 6 USC at 44-45. See Amendment of Part 15 of the Commission’s Rules for
Unlicensed Operations in the Television Bands, Repurposed 600 MHz Band, 600 MHz Guard
Bands and Duplex Gap, and Channel 37, Report & Order, 30 FCC Rcd. 9551 ¶ 88 (2015). 48 Comments of Microsoft at 13.
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VI. The Commission Should Authorize the Use of Directional Antennas
The record reflects strong support for the use of directional antennas in the 6 GHz band.
PISC urges the Commission to both permit and encourage AFCs to take account of antenna
directionality in order to make the most efficient use of this spectrum. As the Dynamic Spectrum
Alliance opined: “Indeed, the Commission should not only permit directional antenna usage, the
regulations should encourage this use where possible. Controlling the interference footprint of
usage can significantly increase the capacity of the band for both directional and non-directional
users.”49
PISC broadly agrees with the Wireless Internet Service Providers Association (WISPA)
that the directional characteristics of antennas can readily be incorporated into AFC calculations:
The AFC should not treat all point-to-point or sector antennas as if they were
omnidirectional. That would be factually incorrect and spectrally inefficient and
could potentially preclude other point-to-point or even point-to-multipoint
operations from being approved by the AFC even thought there would be no
potential for harmful interference.50
VII. The Commission Should Not Impose a Preclusive Out-Of-Band Emissions
Restriction for the 5.9 GHz Band
The Commission should reject proposals to increase the out-of-band emissions (OOBE)
limit at the bottom of the 6 GHz band. 5GAA and Qualcomm contend that the Commission’s -27
dBm/MHz OOBE limit is insufficient.51 5GAA claims its “real-world testing” has shown that
“certain VLP unlicensed operations in and near a vehicle can cause harmful interference to C-
49 Comments of DSA at 21. 50 Comments of Wireless Internet Service Providers Association at 3. 51 Comments of 5GAA at 4-7; Comments of Qualcomm at 9-10.
19
V2X Direct receivers,” and that the organization has shown the Commission these
demonstrations in the past.52
PISC strongly objects to any reconsideration of this issue in the context of the FNPRM.
The Commission did not seek comment on a change in the OOBE limit. It considered and
decided this matter in the Report and Order: “We believe that a limit of -27 dBm/MHz is
necessary to protect services outside the U-NII-5 and U-NII-8 bands, including the Intelligent
Transportation Service below the U-NII-5 band and federal government operations above the U-
NII-8 band.”53 5GAA presents no new evidence to suggest that the Commission’s conclusion
was incorrect, yet it goes even further to claim that “[c]ertain projections regarding the expected
proliferation of outdoor VLP unlicensed devices reinforce the danger of permitting these
unlicensed operations in the lower portions of the 6 GHz band” with no supporting citation or
proof to substantiate this claim.54
The FNPRM is not an appropriate venue for reconsideration. Moreover, the issue is
relevant for review, if at all, in the context of the Commission’s pending 5.9 GHz proceeding
that will decide what auto safety communications technologies, if any, to authorize for continued
operation in the top 30 megahertz of that band.
PISC urges the Commission not to undermine the historic progress it has made to enable
the future of Wi-Fi in both the 6 GHz band and the 5.9 GHz band central to the availability and
affordability of 5G-quality applications and services. The connected future of the country’s
homes, schools and small businesses should not be diminished due to unsubstantiated fears of
harmful interference that have already been investigated and addressed.
52 Comments of 5GAA at 4. 53 See Report and Order at ¶197. See 47 U.S.C § 15.407(b)(5) (effective July 27, 2020). 54 Comments of 5GAA at 6.
20
Moreover, the arguments 5GAA and others make regarding potential interference to the
industry’s hypothetical auto safety service reinforces the rationale for moving at least Cellular
V2X operations out of the 5.9 GHz band entirely. As the Open Technology Institute, Public
Knowledge and other groups in PISC have argued previously, there is no reason future C-V2X
services need to be housed in the 5.9 GHz band other than an ill-fated decision 20 years ago to
require DSRC in the band.55 Today the ITS band is wedged between the current and future most
valuable and intensely used bands for high-capacity Wi-Fi: the UNII-3 band (5725-5850 MHz)
and the U-NII-5 band (5925-6425 MHz).
The 5GAA proposal suggests that C-V2X is being designed to be far more fragile and
susceptible to interference than DSRC is today. Rather than degrade the value of Wi-Fi in the
lower portion of the 6 GHz band, as 5GAA proposes, the Commission should look at other bands
that could offer C-V2X and other automotive communications operations more spectrum and
more insulation from intensively-used adjacent bands. The 4.9 GHz band, itself grossly
underutilized, could present an opportunity for the Commission to move these services as a win-
win-win for the automotive industry, the wireless industry, and for consumers. OTI and PK made
the case for this previously in comments,56 as has the Dynamic Spectrum Alliance.57 OTI
recently detailed this proposal in its recent paper: The 5.9 GHz Band: Removing the Roadblock to
Gigabit Wi-Fi.58
55 See Comments of New America’s Open Technology Institute and Public Knowledge, ET
Docket No. 19-138, RM-11771 (March 9, 2020). 56 Ibid. 57 Ex Parte Filing of the Dynamic Spectrum Alliance, Amendment of Part 90 of the
Commission’s Rules, WP Docket No. 07-100, ET Docket No. 19-138 (June 11, 2020) (the
Commission should “seek[] comment on relocating one or both of the [ITS] technologies
contemplated for the upper portion of the 5.9 GHz band to a portion (20 megahertz or more) of
the 4.9 GHz public safety band”). 58 Michael Calabrese and Amir Nasr, “The 5.9 GHz Band: Removing the Roadblock to Gigabit
Wi-Fi,” New America (July 9, 2020), https://www.newamerica.org/oti/reports/59-ghz-band/.
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VIII. Conclusion
The Commission should ensure that the rules governing the 6 GHz band promote the
most efficient and effective use of this spectrum. The record shows strong support for increasing
the power limit for LPI device operations in the 6 GHz band, for allowing client-to-client
communications, for authorizing a new category VLP devices across the entire band, as well as
mobile standard-power operations and directional antennas. All of these additional steps will be
necessary to achieve the robust, world-leading, and affordable 5G wireless ecosystem that the
Commission envisioned in its historic Report and Order.
Respectfully submitted,
NEW AMERICA’S OPEN TECHNOLOGY INSTITUTE
PUBLIC KNOWLEDGE
AMERICAN LIBRARY ASSOCIATION
SCHOOLS, HEALTH & LIBRARIES BROADBAND (SHLB) COALITION
BENTON INSTITUTE FOR BROADBAND AND SOCIETY
CoSN – CONSORTIUM FOR SCHOOL NETWORKING
NATIONAL HISPANIC MEDIA COALITION
TRIBAL DIGITAL VILLAGE NETWORK
INSTITUTE FOR LOCAL SELF-RELIANCE
NEXT CENTURY CITIES
COMMON CAUSE
ACCESS HUMBOLDT
X-LAB
/s/ Michael Calabrese
Amir Nasr
New America’s Open Technology Institute
740 15th Street NW, Suite 900
Washington, D.C. 20005
July 27, 2020