[Federal Register Volume 86, Number 36 (Thursday, February 25, 2021)]
[Proposed Rules]
[Pages 11490-11494]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-03437]


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FEDERAL COMMUNICATIONS COMMISSION

47 CFR Part 15

[ET Docket No. 20-36; FCC 20-156; FRS 17403]


Unlicensed White Space Device Operations in the Television Bands

AGENCY: Federal Communications Commission.

ACTION: Proposed rule.

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SUMMARY: In this document, the Commission seeks comment on the use of a 
terrain-based propagation model such as Longley-Rice for determining 
white space channel availability and seeks to develop a record on 
whether or not to implement such a model. In particular, the Commission 
seeks comment on the effect use of such a model would have on 
availability of channels for white space devices, how a terrain-based 
model such as Longley-Rice could be implemented within the current 
white space device framework, the technical parameters necessary to use 
such a model for identifying available spectrum while protecting 
incumbents from harmful interference, and various database and device 
implementation issues.

DATES: Comments are due on or before March 29, 2021; reply comments are 
due on or before April 26, 2021.

ADDRESSES: You may submit comments, identified by ET Docket No. 20-36, 
by any of the following methods:
     Federal Communications Commission's Website: http://apps.fcc.gov/ecfs/. Follow the instructions for submitting comments.
     People with Disabilities: Contact the FCC to request 
reasonable accommodations (accessible format documents, sign language 
interpreters, CART, etc.) by email: [email protected] or phone: 202-418-
0530 or TTY: 202-418-0432.
    For detailed instructions for submitting comments and additional 
information on the rulemaking process, see the SUPPLEMENTARY 
INFORMATION section of this document.

FOR FURTHER INFORMATION CONTACT: Hugh Van Tuyl, Office of Engineering 
and Technology, 202-418-7506, [email protected].

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SUPPLEMENTARY INFORMATION: This is a summary of the Commission's 
further notice of proposed rulemaking (FNPRM), in ET Docket No. 20-36, 
FCC 20-156, adopted on October 27, 2020, and released on October 28, 
2020. The full text of this document is available for public inspection 
and can be downloaded at: https://www.fcc.gov/document/fcc-increases-unlicensed-wireless-operations-tv-white-spaces-0 or by using the search 
function for ET Docket No. 20-36 on the Commission's ECFS web page at 
www.fcc.gov/ecfs.

Synopsis

    1. Discussion. The Commission addresses Dynamic Spectrum Alliance, 
Wireless Internet Service Providers Association (WISPA), and Public 
Interest Spectrum Coalition arguments that the Commission should 
determine white space channel availability using a terrain-based model, 
such as the Longley-Rice Irregular Terrain Model (Longley-Rice model), 
which they assert will determine channel availability more accurately 
than the current contour-based model used by the Commission. For 
example, a terrain-based model could permit a white space device to 
deploy at a location where the television signal is shielded by a large 
hill or mountain, whereas the existing methodology does not account for 
such shielding. National Association of Broadcasters (NAB) and 
Sennheiser, however, oppose using the Longley-Rice model due to 
concerns about its accuracy in protecting TV receivers and because it 
may slow operation of the white space database.
    2. Current protection model. Under current rules, white space 
devices must generally operate outside the defined co-channel and 
adjacent channel television station protected contours. The rules 
provide a table of separation distances beyond the protected contour 
that white space devices must meet that is based on the white space 
device's equivalent isotropic radiated power (EIRP) and height above 
average terrain (HAAT). These distances are based on a desired-to-
undesired (D/U) signal ratio of 23 dB at the edge of the protected 
contour for co-channel operation, and -33 dB at the edge of the 
protected contour for adjacent channel operation, with a 14 dB 
allowance for TV receive antenna front-to-back ratio. The distances 
were calculated using the F(50,10) curves for separation distances of 
greater than 15 kilometers, the F(50,50) curves for separation 
distances of 1.5 to 15 kilometers, and the TM-91-1 model for separation 
distances of less than 1.5 kilometers.
    3. Longley-Rice model. The Longley-Rice model is used to make 
predictions of radio signal field strength using the median attenuation 
calculated as a function of distance and the signal variability in time 
and space. The model can be run in point-to-point mode where it 
examines a specific radio signal path between a transmitter and a 
receiver, or in area mode in which it predicts field strength at many 
geographic points within a specified area. Each operational mode uses a 
terrain elevation profile in making predictions; in the point-to-point 
mode path-specific parameters can be determined from the terrain 
profile between the transmitter and receiver, and in area mode the 
elevation profile between the transmitter and each specific reception 
point is examined. The model may require a large number of reception 
points to be individually examined. It also requires a large set of 
input parameters encompassing system parameters (e.g., frequency, 
polarization, antenna heights), environmental parameters (e.g., terrain 
irregularity, electrical ground constants, surface refractivity, 
climate information), deployment parameters, and statistical parameters 
(e.g., reliability and confidence level). Based on the predicted radio 
signal attenuation and using additional factors such as transmitter 
power and antenna directivity, the D/U signal ratio can be estimated 
and compared against the 23 dB co-channel and -33 dB adjacent channel 
standards used as the basis when developing the white space device 
rules to predict whether harmful interference is likely to occur to 
television reception.
    4. The Longley-Rice model can be implemented using a variety of 
methodologies. For example, the area subject to calculation can be 
divided into rectangular cells, e.g., a 1-by-1 kilometer grid, and the 
field strength predictions are calculated at a point in each cell, such 
as the geographic center or the population centroid. The Commission 
notes that as computing power has increased over the years, it is most 
common to execute the model in point-to-point mode and use a batch 
process to evaluate each grid cell within a specified area. 
Nevertheless, the Commission seeks comment on various implementations 
for white space device evaluation which include both area and point to 
point mode as it is concerned about the available processing power, 
capabilities and time requirements to run many simultaneous batch 
processes to evaluate a large number of white space devices that may 
query the database for available channel information at the same time. 
The Commission seeks comment on whether it should specify a specific 
operational mode and how the model should be implemented under a 
specific mode or both operational modes.
    5. As a threshold matter, the Commission seeks comment on whether 
using a terrain-based model, and in particular the Longley-Rice model, 
would better serve the white space device community as well as 
television broadcasters and other protected entities in the television 
bands. Commenters should specify the pros and cons of their preferred 
approach as it relates either to the Commission's existing contour 
method or other terrain-based propagation models. The Commission seeks 
comment on how the Longley-Rice model could be used to determine 
available white space channels. Would it be used only to determine if a 
white space device at a specific geographic location and power level 
meets the co- and adjacent channel D/U ratios? Or should the 
propagation model be used for wider applicability such as for 
determining separation distances necessary to ensure other protected 
entities such as licensed wireless microphones, television translator 
receive sites, cable headends, and land mobile stations do not 
experience harmful interference? In such cases, what criteria should be 
used to determine the protection distances? Should D/U ratios be used 
here too, or some other metric such as an interference-to-noise ratio? 
Commenters should provide detailed technical reasoning regarding how 
the metric they support achieves the necessary protection levels. In 
addition, the Commission seeks comment on whether the propagation model 
can be used to determine which areas are ``less congested'' and thus 
subject to more flexible rules. In this case, what criteria should be 
used as the basis for determining a ``less congested'' area as it 
relates to use of the propagation model? Could using the Longley-Rice 
propagation model for this purpose permit additional areas to be 
designated as ``less congested'' to provide more flexibility for white 
space devices? Similarly, the Commission seeks comment on whether the 
propagation model can be applied not only to fixed white space devices, 
but also to personal/portable, mobile and narrowband IoT white space 
devices. In each context, are there specific provisions required for 
how the model is implemented to account for the

[[Page 11492]]

different white space device operational modes and use cases?
    6. What mode--point-to-point or area--is appropriate for each 
situation? For fixed white space devices, it would seem intuitive to 
use the point-to-point mode to examine a specific radio path to the 
television station contour. However, the Commission seeks comment on 
what specific path should be examined--the shortest path to the contour 
or possibly a different path where the white space device and 
television contour are further apart, but due to terrain shielding 
effects, may have less attenuation. How would each path be determined 
and how many specific paths would need to be evaluated before a 
determination can be made as to whether a channel is available for 
white space device use? Or would it be better to run the propagation 
model in area mode to determine the points along the television contour 
with the highest co- and adjacent channel D/U ratios and then run the 
model again in point-to-point mode for those specific transmission 
paths? Should a D/U threshold be set to determine which paths need 
further examination? If so, how close to the 23 dB co-channel and -33 
dB adjacent channel thresholds do they need to be? And if an initial 
area mode calculation must be performed, what grid size is appropriate 
and what point within each grid cell should be used for analysis 
purposes? Using similar logic, how could the model be applied to 
determine ``less congested'' areas and operating locations for 
personal/portable, mobile or narrowband white space devices? Should it 
be run only in area mode or must additional point-to-point calculations 
also be performed? Commenters should provide detail regarding how the 
model can be applied to each of the situations likely to be encountered 
for various white space device types.
    7. The Commission also seeks comment on whether the Longley-Rice 
model would always determine the same or shorter separation distances 
from a TV contour than the current model, or whether there are cases 
where it could require greater separation distances, and therefore 
reduce white space device channel availability. How justified are the 
concerns expressed by the NAB regarding the use of the Longley-Rice 
model to protect television reception? NAB argues that the Longley-Rice 
model requires transmitter and receiver locations to be known with 
precision, while television receiver locations are not reflected in any 
database and cannot be passively detected, and that current television 
receiver protection requirements for white space devices are not overly 
conservative or based on worst-case assumptions. The Commission seeks 
comment on NAB's assertions. Commenters that favor use of the Longley-
Rice model should provide specific reasons regarding how NAB's concerns 
can be addressed.
    8. The Commission further seeks comment on whether the Longley-Rice 
model should be the exclusive means of determining white space channel 
availability, or whether it should be an optional alternative to the 
current protection model. As an alternative model, would it be more 
appropriate to use the Longley-Rice model in combination with other 
propagation models in some circumstances such as the Commission 
requires for 6 GHz unlicensed devices, where different propagation 
models are specified at different distances? Finally, the Commission 
seeks comment on whether the Longley-Rice model can or should be used 
for modeling the TV coverage itself, and therefore possibly allowing 
white space device operation within a TV protected contour as 
calculated using the F(50,90) curves so long as the minimum D/U ratios 
are met.
    9. The Commission also seeks comment on the technical requirements 
that need to be specified if the Commission permits the use of the 
Longley-Rice model. What inputs are necessary for using the model in 
either point-to-point mode or area mode for each white space device 
type, potential use situation as well as for determining ``less 
congested'' areas and protection distances for each type of protected 
entity? Which of these inputs should be specified by rule and which can 
be determined either by the white space device operator or the 
database? Commenters should be as specific as possible regarding their 
preference for input parameters and provide engineering justification 
for those preferences. What grid size and which location within each 
grid cell should be used for determining white space channel 
availability?
    10. The Commission further seeks comment on the terrain database 
that should be used with the Longley-Rice model or any alternative 
terrain-based model that the Commission specifies. Should the 
Commission require the use of a particular terrain database, such as 
one based on 3-arc second data or 1-arc second data? Should the 
Commission instead simply specify some minimum criteria for a terrain 
database, e.g., granularity, and allow the use of any terrain database 
that meets or exceeds that criteria?
    11. Model Implementation. The Commission seeks comment on the 
various implementation factors that must be considered if the 
Commission adopts rules to allow the use of the Longley-Rice model or 
another terrain-based propagation model. As an initial matter, the 
white space database administrator would need time to implement this 
change to its system. How long should the Commission provide for the 
database administrator to implement these necessary changes? What type 
of testing should be performed to ensure that a white space database 
using a terrain-based model provides accurate results? Should the 
Commission perform its own testing or should it require public testing 
as it did when initially designating white space database 
administrators? The Commission also seeks comment on any effect that 
these changes might have on database and network performance. If the 
amount of overhead data necessary to use the Longley-Rice model 
significantly increases over what is necessary under the existing 
rules, would the result be slower response times as Sennheiser 
suggests? If so, would this detrimentally affect the utility of white 
space devices? Would such changes affect the capacity of the database 
to handle large numbers of white space devices simultaneously?
    12. Are changes needed to white space devices if the database is 
modified to base channel availability on the Longley-Rice model? Does 
the information sent from white space devices to the database need to 
change from the data set currently sent? If so, could all existing 
devices be updated? If not, how should the database deal with devices 
that can send the necessary data and those that cannot? Should the 
Commission require that devices be updated within a specific time 
period? What should that time period be? Would any of the needed 
changes to a white space device affect its emissions and necessitate a 
change to its equipment authorization records?
    13. How would the database using the Longley-Rice model account for 
any device location uncertainty? What actions should be taken if the 
propagation model determines that an existing operational white space 
device on a specific channel based on current protection distances no 
longer meets the D/U ratios after performing the required calculations? 
Should that device no longer be permitted to operate on that channel at 
its current power level or could the existing separation distances 
specified in the rules be considered a safe harbor for operations?

[[Page 11493]]

    14. The operational changes and effects of implementing the 
Longley-Rice model for determining white space device channel 
availability range from technical and modelling considerations to 
specific model implementation factors to database and device matters. 
The Commission asks that commenters comprehensively examine all aspects 
of the rule changes that would be needed and the effect they would have 
if it were to modify the white space device rules to specify use of the 
Longley-Rice model rather than the current contour-based method of 
protecting television stations and other protected entities in the TV 
bands.

Procedural Matters

    15. Paperwork Reduction Act Analysis. This document contains new or 
modified information collection requirements subject to the Paperwork 
Reduction Act of 1995 (PRA), Public Law 104-13. It will be submitted to 
the Office of Management and Budget (OMB) for review under Section 
3507(d) of the PRA. OMB, the general public, and other Federal agencies 
will be invited to comment on the new or modified information 
collection requirements contained in this proceeding. In addition, the 
Commission note that pursuant to the Small Business Paperwork Relief 
Act of 2002, Public Law 107-198, see 44 U.S.C. 3506(c)(4), it 
previously sought specific comment on how the Commission might further 
reduce the information collection burden for small business concerns 
with fewer than 25 employees.
    16. Initial Regulatory Flexibility Analysis. As required by the 
Regulatory Flexibility Act, the Commission has prepared an Initial 
Regulatory Flexibility Analysis (IRFA) of the possible significant 
economic impact on a substantial number of small entities of the 
proposals addressed in this FNPRM. The Full IRFA is found in Appendix D 
at https://www.fcc.gov/document/fcc-increases-unlicensed-wireless-operations-tv-white-spaces-0. Written public comments are requested on 
the IRFA. These comments must be filed in accordance with the same 
filing deadlines for comments on the FNPRM, and they should have a 
separate and distinct heading designating them as responses to the 
IRFA. The Commission's Consumer and Governmental Affairs Bureau, 
Reference Information Center, will send a copy of this FNPRM, including 
the IRFA, to the Chief Counsel for Advocacy of the Small Business 
Administration, in accordance with the Regulatory Flexibility Act.
    17. The Commission requests written public comment on the IRFA. 
Comments must be filed in accordance with the same filing deadlines as 
comments filed in response to the FNPRM and must have a separate and 
distinct heading designating them as responses to the IRFA. The 
Commission's Consumer and Governmental Affairs Bureau, Reference 
Information Center, will send a copy of this FNPRM, including the IRFA, 
to the Chief Counsel for Advocacy of the Small Business Administration, 
in accordance with the Regulatory Flexibility Act.
    18. Ex Parte Presentations. The proceeding this FNPRM initiates 
shall be treated as a ``permit-but-disclose'' proceeding in accordance 
with the Commission's ex parte rules. Persons making ex parte 
presentations must file a copy of any written presentation or a 
memorandum summarizing any oral presentation within two business days 
after the presentation (unless a different deadline applicable to the 
Sunshine period applies). Persons making oral ex parte presentations 
are reminded that memoranda summarizing the presentation must (1) list 
all persons attending or otherwise participating in the meeting at 
which the ex parte presentation was made, and (2) summarize all data 
presented and arguments made during the presentation. If the 
presentation consisted in whole or in part of the presentation of data 
or arguments already reflected in the presenter's written comments, 
memoranda or other filings in the proceeding, the presenter may provide 
citations to such data or arguments in his or her prior comments, 
memoranda, or other filings (specifying the relevant page and/or 
paragraph numbers where such data or arguments can be found) in lieu of 
summarizing them in the memorandum. Documents shown or given to 
Commission staff during ex parte meetings are deemed to be written ex 
parte presentations and must be filed consistent with rule Sec.  
1.1206(b). In proceedings governed by rule Sec.  1.49(f) or for which 
the Commission has made available a method of electronic filing, 
written ex parte presentations and memoranda summarizing oral ex parte 
presentations, and all attachments thereto, must be filed through the 
electronic comment filing system available for that proceeding, and 
must be filed in their native format (e.g., .doc, .xml, .ppt, 
searchable .pdf). Participants in this proceeding should familiarize 
themselves with the Commission's ex parte rules.
    19. Filing Requirements. Pursuant to Sec. Sec.  1.415 and 1.419 of 
the Commission's rules, 47 CFR 1.415, 1.419, interested parties may 
file comments and reply comments on or before the dates indicated on 
the first page of this document. Comments may be filed using the 
Commission's Electronic Comment Filing System (ECFS). See Electronic 
Filing of Documents in Rulemaking Proceedings, 63 FR 24121 (1998).
     Electronic Filers: Comments may be filed electronically 
using the internet by accessing the ECFS: http://apps.fcc.gov/ecfs/.
     Paper Filers: Parties who choose to file by paper must 
file an original and one copy of each filing.
    Filings can be sent by commercial overnight courier, or by first-
class or overnight U.S. Postal Service mail. All filings must be 
addressed to the Commission's Secretary, Office of the Secretary, 
Federal Communications Commission.
     Commercial overnight mail (other than U.S. Postal Service 
Express Mail and Priority Mail) must be sent to 9050 Junction Drive, 
Annapolis Junction, MD 20701.
     U.S. Postal Service first-class, Express, and Priority 
mail must be addressed to 45 L Street NE, Washington, DC 20554.
     Effective March 19, 2020, and until further notice, the 
Commission no longer accepts any hand or messenger delivered filings. 
This is a temporary measure taken to help protect the health and safety 
of individuals, and to mitigate the transmission of COVID-19. See FCC 
Announces Closure of FCC Headquarters Open Window and Change in Hand-
Delivery Policy, Public Notice, DA 20-304 (March 19, 2020). https://www.fcc.gov/document/fcc-closes-headquarters-open-window-and-changes-hand-delivery-policy.
    20. People with Disabilities: To request materials in accessible 
formats for people with disabilities (braille, large print, electronic 
files, audio format), send an email to [email protected] or call the 
Consumer & Governmental Affairs Bureau at 202-418-0530 (voice), 202-
418-0432 (tty).

Ordering Clauses

    21. Accordingly, it is ordered, pursuant to Sections 4(i), 201, 
302, and 303 of the Communications Act of 1934, as amended, 47 U.S.C. 
154(i), 201, 302a, 303, that this further notice of proposed rulemaking 
is hereby adopted.
    22. It is further ordered that the Commission's Consumer and 
Governmental Affairs Bureau, Reference Information Center, shall send a 
copy of this further notice of proposed rulemaking, including the 
Initial Regulatory Flexibility Analyses, to the

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Chief Counsel for Advocacy of the Small Business Administration.

Federal Communications Commission.
Marlene Dortch,
Secretary.
[FR Doc. 2021-03437 Filed 2-24-21; 8:45 am]
BILLING CODE 6712-01-P