# Unlicensed Use of TV Band and 600 MHz Band Spectrum

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2014-26674

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** November 21, 2014
- **Citation:** 79 FR 69710

## Text

FEDERAL COMMUNICATIONS COMMISSION
47 CFR Parts 15 and 74
[ET Docket No. 14-165; FCC 14-144]
Unlicensed Use of TV Band and 600 MHz Band Spectrum

AGENCY:

Federal Communications Commission.

ACTION:

Proposed rule.

SUMMARY:

In this document, the Commission proposes and seeks comments on rules for unlicensed operations in the frequency bands that are now and will continue to be allocated and assigned to broadcast television services after the incentive auction, including fixed and personal/portable white space devices and unlicensed wireless microphones. The Commission also proposes and seeks comment on rules for the operation of unlicensed white space devices, and licensed and unlicensed wireless microphones in the 600 MHz Band, guard bands and duplex gap that will exist after the incentive auction.

DATES:

Comments are due on or before January 5, 2015; reply comments are due on or before January 26, 2015.

FOR FURTHER INFORMATION CONTACT:

Hugh L. Van Tuyl, Office of Engineering and Technology, (202) 418-7506, email:
Hugh.VanTuyl@fcc.gov
, TTY (202) 418-2989.

ADDRESSES:

You may submit comments, identified by ET Docket No. 14-165, by any of the following methods:

Federal Communications Commission's Web site:
http://fjallfoss.fcc.gov/ecfs2/.
Follow the instructions for submitting comments.

Mail: Hugh Van Tuyl, Office of Engineering and Technology, Room 7-A162, Federal Communications Commission, 445 12th SW., Washington, DC 20554.

People with Disabilities: Contact the FCC to request reasonable accommodations (accessible format documents, sign language interpreters, CART, etc.) by email:
FCC504@fcc.gov
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.

SUPPLEMENTARY INFORMATION:

This is a summary of the Commission's
NPRM of Proposed Rule Making,
ET Docket No. 14-165, FCC 14-144, adopted September 30, 2014, and released September 30, 2014. The full text of this document is available for inspection and copying during normal business hours in the FCC Reference Center (Room CY-A257), 445 12th Street SW., Washington, DC 20554. The complete text of this document also may be purchased from the Commission's copy contractor, Best Copy and Printing, Inc., 445 12th Street SW., Room, CY-B402, Washington, DC 20554. The full text may also be downloaded at:
www.fcc.gov
.

Pursuant to sections 1.415 and 1.419 of the Commission's rules, 47 CFR 1.415 and 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://fjallfoss.fcc.gov/ecfs2/.

• Paper Filers: Parties who choose to file by paper must file an original and one copy of each filing. If more than one docket or rulemaking number appears in the caption of this proceeding, filers must submit two additional copies for each additional docket or rulemaking number. Filings can be sent by hand or messenger delivery, 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.

All hand-delivered or messenger-delivered paper filings for the Commission's Secretary must be delivered to FCC Headquarters at 445 12th St. SW., Room TW-A325, Washington, DC 20554. The filing hours are 8:00 a.m. to 7:00 p.m. All hand deliveries must be held together with rubber bands or fasteners. Any envelopes and boxes must be disposed of before entering the building.

Commercial overnight mail (other than U.S. Postal Service Express Mail and Priority Mail) must be sent to 9300 East Hampton Drive, Capitol Heights, MD 20743.

U.S. Postal Service first-class, Express, and Priority mail must be addressed to 445 12th Street SW., Washington, DC 20554.

People with Disabilities: To request materials in accessible formats for people with disabilities (braille, large print, electronic files, audio format), send an email to
fcc504@fcc.gov
or call the Consumer & Governmental Affairs Bureau at 202-418-0530 (voice), 202-418-0432 (tty).

Summary of NPRM of Proposed Rulemaking

1. The Notice of Proposed Rulemaking (NPRM) proposes and seeks comment on rules for fixed and personal/portable white space devices that would operate in: The frequency bands that are now and will continue to be allocated and assigned to broadcast television services (the “TV bands”); the 600 MHz Band Plan spectrum that, following the Incentive Auction, will be designated as guard bands (including a duplex gap); the portion of that spectrum allocated and assigned to new part 27 licensees where wireless licensees have not commenced operations; and Channel 37. It also proposes rules for unlicensed wireless microphone operations under part 15 of the rules in the TV bands and 600 MHz Band Plan spectrum, and for licensed wireless microphone operations under part 74 of the rules in the 600 MHz Band Plan spectrum. In addition, the NPRM proposes changes to the white spaces databases and changes for certifying, manufacturing and marketing white space devices and wireless microphones in the frequency bands at issue in this proceeding. In particular, the NPRM proposes rules to expand the location and frequency information in these databases so that they can be used to identify available frequencies for white space devices, including unlicensed wireless microphones, in the repurposed 600 MHz band, guard bands, and Channel 37.

2. The Commission's part 15 rules allow unlicensed devices to operate in the TV bands at locations where frequencies are not in use by licensed services. These devices, which are commonly referred to as TV white space (TVWS) devices, may be either fixed or personal/portable. The TV bands currently consist of six-megahertz channels designated 2 to 51 in four bands of frequencies in the VHF and UHF regions of the radio spectrum. TVWS devices are not permitted to operate on channel 37, which is allocated for the Radio Astronomy Service (RAS) and Land Mobile Service (the latter being limited to Wireless Medical Telemetry Service (WMTS), or on any other channel within 2.4 kilometers of protected radio observatories. To prevent harmful interference to broadcast television stations and other authorized users of these bands, TVWS devices obtain a list of available TV channels that may be used at their location from databases

administered by private entities selected by the Commission.

3. Certain entities may be issued licenses under subpart H of part 74 of the rules to operate low power auxiliary stations, including wireless microphones, in the TV bands. Because the operators of part 74 wireless microphones are licensed, they may register the times and locations of their operation in the TV bands databases to obtain interference protection from TVWS devices. The Commission also allows the operation of wireless microphones in the TV bands on an unlicensed basis under a waiver of the part 15 rules granted in the 2010. Operators of unlicensed wireless microphones are generally not permitted to register in the TV bands database, but parties operating large numbers of wireless microphones on an unlicensed basis at venues of events and productions/shows may register in the TV bands database if they meet certain criteria specified in the rules and obtain Commission approval.

4. In the
Incentive Auction R&O
, 79 FR 48442 (August 15, 2014), the Commission adopted rules to repurpose broadcast television spectrum in the UHF bands for licensed wireless services. Under these rules, full power and Class A broadcast licensees may participate in a reverse auction that will allow them to voluntarily relinquish some or all of their spectrum usage rights in exchange for financial compensation. A broadcast licensee that participates in the auction will have the option to turn in its license, move to a channel in the VHF band, or cease using its channel and share a channel with another licensee. The Commission will reorganize or repack the remaining full power and Class A television stations to clear the UHF band from channel 51 down. When the transition is completed, the TV bands will occupy a shorter frequency range than they do today and fewer channels may be available for TVWS and wireless microphone uses at any given location.

5. The Commission adopted a band plan for the repurposed 600 MHz spectrum (“600 MHz Band Plan”) in the
Incentive Auction R&O
that provides for a guard band between television spectrum and 600 MHz downlink services, a guard band between 600 MHz uplink and downlink services (a duplex gap), and guard bands between 600 MHz downlink services and channel 37. It decided to permit unlicensed devices, including unlicensed wireless microphones, to operate in the guard bands and duplex gap. The Commission also decided to permit unlicensed devices to operate on channel 37 and in spectrum reallocated and reassigned to new wireless services except in those areas where part 27 600 MHz Band wireless licensees commence operations. It stated that it planned to develop technical rules for unlicensed operation and to consider changes to the rules for TVWS devices in a separate proceeding.

A. Fixed and Personal/Portable White Space Devices

1. TV Bands

a. Permissible Frequencies of Operation

6.
Channels for white space device and microphone use.
Under the current rules, white space devices may not operate on the first two vacant TV channels above and below channel 37 to ensure that there is spectrum available for wireless microphones. In the
Incentive Auction R&O
, the Commission decided that it would no longer continue to designate up to two unused television channels in any area exclusively for wireless microphone operations. The Commission stated that in this proceeding we are initiating today, it would seek comment on ways it could update the rules for white spaces databases to provide for more immediate reservation of unused and available channels in the television bands to help ensure that licensed wireless microphone operators can obtain access to available television channels without receiving harmful interference from white space devices. It decided that it would continue to prohibit white space devices from operating on the first two vacant TV channels above and below channel 37 until such time as revised Commission rules are in effect to provide for more immediate interference protection. After that time, any available channels could be used by either wireless microphones or white space devices.

7. The Commission proposes to eliminate the prohibition on white space device operation on the first two vacant TV channels above and below channel 37 and make them available for use by white space devices when the rules proposes in this NPRM become effective. Specifically, the Commission proposes to increase the frequency at which white space devices must re-check the database, and limit the time required for a wireless microphone registration made in one white spaces database to appear in all other white spaces databases. The effect of these two proposals will ensure that a white space device ceases operation on a channel used by a wireless microphone within 30 minutes after a new microphone registration is entered into the database. The Commission seeks comment on these proposals.

8. In the
Incentive Auction R&O
, the Commission also stated that it expects there will be at least one channel not assigned to a television station in all areas of the United States at the end of the repacking process, and that it intends, after NPRM and an opportunity for public input, to designate one such channel in each area for shared use by white space devices and wireless microphones. The Commission plans to address the issue of a preserved white space channel in a separate proceeding. It is not proposing to make any changes to the white space rules with respect to a future preserved channel. Such a channel would simply appear in the white spaces database as vacant and would therefore be available for white space devices under the existing rules as well as any new or modified rules adopted in this proceeding.

9.
Operation of fixed devices on channels 3 and 4.
The current prohibition on fixed white space device operation on channels 3 and 4 may no longer be warranted. The Commission established this prohibition to protect TV interface devices and TV receivers from direct pickup interference on channels 3 and 4. The Commission did not have detailed data on the susceptibility of TV interface devices and TV receivers to direct pickup interference on channels 3 and 4, but decided to take a cautious approach due to the expected large number of TV interface devices with outputs on those channels. The number of these devices has declined significantly since 2008. The transition from analog to digital TV in 2009 spurred many consumers to replace their old analog TV receivers with digital receivers that have multiple inputs that allow the connection of external devices without requiring the use of a channel 3 or 4 input signal, including HDMI, component video and composite video inputs. Further, the price of new TV receivers has dropped significantly since that time, resulting in many more consumers replacing their old analog TV receivers. TV receivers also have been required to come equipped with digital TV tuners for a number of years, thus eliminating the need to use an external converter box to receive over-the-air signals. While we recognize that some consumers continue to use older analog TV sets with a converter box or other TV interface devices with a channel 3 or 4 output, we believe that number is significantly less than in 2008, and will continue to drop over time as older TV sets are replaced.

10. The Commission therefore proposes to eliminate the prohibition on

the use of channels 3 and 4 by fixed white space devices. This proposed action would provide an additional 12 MHz of contiguous spectrum for use by white space devices in areas where those channels are not used for authorized services. Limiting the use of these channels to fixed white space devices will reduce the likelihood of direct pickup interference to TV interface devices and TV receivers that continue use these frequencies, since a fixed white space device is less likely to be used in close proximity to a TV receiver than a portable device. The Commission seeks comment on this proposal. Specifically, it seeks comment on the extent to which consumers still use TV interface devices that operate on channels 3 and 4,
e.g.
, the estimated number and types of devices. The Commission also seeks comment on the susceptibility of TV interface devices and receivers to direct pickup interference on channels 3 and 4, particularly the signal levels at which such interference would occur as compared to the expected signal level from a nearby white space device. In addition, the Commission seeks comment on the extent to which white space device manufacturers would use TV channels 3 and 4 if they were available for fixed devices.

11.
Operation of personal/portable devices on channels 14-20 and below channel 14
. Operation of personal/portable white space devices is currently prohibited below TV channel 21. The Commission established a prohibition on personal/portable device operation on channels 14-20 to prevent possible interference to public safety and other operations in the PLMRS/CMRS that use channels in that range in certain cities and in other areas under waivers. It decided to prohibit the use of personal/portable devices on channels 14-20 nationwide since the devices could be easily transported anywhere.

12. The repurposing of spectrum for part 27 services will reduce the number of channels available for white space use, and relaxing the restrictions on the channels available for personal/portable devices could offset that reduction. We believe that it is appropriate to revisit the Commission's previous decisions to prohibit personal/portable device operation on channels 14-20 and below channel 14. Since the time the Commission made these decisions, it has designated multiple TV bands database administrators and has had extensive experience working with their databases. Based on that experience, the Commission has a high degree of confidence that the databases can reliably protect PLMRS/CMRS operations. The locations where the PLMRS/CMRS is used, both in eleven cities and in other areas where it is authorized under waiver, are already in the TV bands database since that information is used to protect those operations from fixed white space operations. Personal/portable devices rely on database access to determine their list of available channels, so they can protect the PLMRS/CMRS in the same manner as fixed devices.

13. Accordingly, the Commission proposes to remove the prohibition on personal/portable device operation on channels 14-20. This proposed action would make 42 megahertz of spectrum potentially available in locations where the spectrum is not used for the PLMRS/CMRS or other authorized services. The Commission seeks comment on the risk of interference to public safety and other PLRMS/CMRS based on the Commission's current technical rules for personal portable devices,
e.g.
, power limits and database access. It also seeks comment on any changes to the rules that would be required to minimize the risk of harmful interference if we were to allow operations on channels 14-20.

14. In addition, the Commission seeks comment on whether it should permit personal/portable devices to operate below channel 14. Allowing operation of personal/portable devices on channels 7-13 would make another 42 megahertz of spectrum potentially available for personal/portable devices. On which channels should we permit operation? Would manufacturers be interested in developing personal/portable devices that operate below channel 14 given the longer radio wavelengths at these lower frequencies?

b. Technical Rule Changes

(i) Fixed Device Operation on Adjacent Channels

15. Fixed white space devices, which can operate with a maximum power of four watts EIRP, are not permitted to operate on channels that are adjacent to occupied TV channels. They must always operate outside the defined service contours of adjacent channel TV stations by a minimum distance specified in the rules. Personal/portable devices, which can operate with a maximum power of 100 milliwatts EIRP, are generally required to operate outside the defined service contour of adjacent channel TV stations as well. However, personal/portable devices are permitted to operate within the service contour of adjacent channel TV stations if they reduce their power to 40 milliwatts EIRP. There is currently no corresponding provision in the rules that permits fixed devices to operate within the service contour of adjacent channel stations at reduced power. The requirement for fixed white space devices to avoid adjacent channel operation means that they may operate only at locations where there are three contiguous vacant TV channels, regardless of how low they reduce their operating power.

16. After the incentive auction and TV spectrum repacking, there will be fewer vacant TV channels available for white space devices. Therefore, the Commission expects that there will be fewer locations where three contiguous vacant channels exist, particularly in urban areas, thus limiting the locations where fixed devices may be used. The Commission proposes two changes to the current rules to provide fixed devices access to more vacant TV channels.

17. First, the Commission proposes to allow fixed devices to operate adjacent to occupied TV channels (
i.e.
, within their service contour), provided the operating power is reduced to 40 milliwatts EIRP. This is the same maximum power level that we permit for personal/portable devices that operate adjacent to occupied TV channels. This change would allow fixed devices to operate in locations where the spectrum is highly congested and available channels are not contiguous. The Commission also proposes to modify the table of separation distances in § 15.712(a)(2) to include co-channel separation distances for 40 milliwatt fixed devices. The current table of separation distances between fixed white space devices and co-channel television service contours was developed assuming a four watt EIRP device, so the separation distances are greater than necessary to protect TV service from a 40 milliwatt white space device. The methodology we will use for determining these distances and the proposed distances are discussed in the following paragraphs.

18. The Commission seeks comment on these proposals. In particular, it seeks comment on the appropriateness of making the rules for fixed and personal/portable white space devices consistent with respect to operation within an adjacent TV station's contour. The Commission also seeks comment on the usefulness of a 40 milliwatt power level for fixed devices and whether we could allow higher power levels without causing interference to adjacent TV stations. Parties that recommend higher power levels should submit technical justification (
e.g.
, analysis or test data) to support their recommendations.

19. Second, the Commission proposes to allow fixed devices to operate with a maximum power of four watts EIRP at locations where there are two contiguous vacant channels rather than three. When the Commission adopted the current requirement for three contiguous vacant channels, it stated that it would remain open to modifying this requirement if parties develop options that would permit operations on first adjacent channels that would not increase the potential for interference to television service and submit those for our consideration. This issue is revisited here because such operation will increase spectrum efficiency and the Commission believes, based on several studies, that operating in this manner will not increase the potential of interference to television reception. The Commission invites parties to submit information on such studies in response to this NPRM. The Commission further proposes that such operation would have to be within a six megahertz band centered on the boundary between the two vacant television channels, effectively reducing the frequency separation from six megahertz to three megahertz on each side of the white space channel. The Commission also proposes that the device would have to comply with all fixed white space requirements with respect to the six megahertz band in which it operates (
e.g.
, maximum conducted power, power spectral density and out-of-band emissions.) These changes would allow fixed devices to operate at the maximum power currently permitted under the rules in locations where they cannot operate under the current rules.

20. The Commission seeks comment on these proposals, particularly whether such operation would adequately protect television stations operating on adjacent channels. Commenters should indicate if they believe any rule changes are necessary to ensure protection of adjacent channel TV stations. For example, should we require slightly greater adjacent channel separation distances for fixed devices that operate with two vacant channels instead of three? If so, what are the appropriate distances?

(ii) Operation at Lower Power Levels

21. As proposed, there would be three power levels at which white space devices could operate: 40 milliwatts, 100 milliwatts and 4000 milliwatts EIRP. We note however, that the current table of separation distances in § 15.712(a)(2) was based on an EIRP of 4000 milliwatts which results in greater distance than necessary to protect TV reception from devices operating at 40 milliwatts or 100 milliwatts. By allowing shorter separation distances for devices operating at less than 4000 milliwatts EIRP, we can expand the locations at which they can operate.

22. In addition, we can provide even more flexibility for white space device users by defining intermediate power levels and corresponding separation distances. This will allow white space devices operating at less than the maximum permissible power to meet separation distances commensurate with their actual power and still protect over-the-air TV reception and other authorized services from harmful interference. As a result, white space devices, which must include transmit power control, would be able to operate in more locations with limited spectrum availability than available today. In crafting our proposal, we observe that the power increase from 40 milliwatts to 100 millwatts is 4 dB, and that the difference in power from 100 milliwatts to 4000 milliwatts is 16 dB. The Commission, therefore proposes a series of tables providing co- and adjacent channel separation distances from the TV contour based on intermediate power levels in uniform 4 dB steps for fixed devices. Specifically, it proposes to define separation distances for fixed devices at EIRP levels of 40 milliwatts, 100 milliwatts, 250 milliwatts, 625 milliwatts and 1600 milliwatts (
i.e.
,16 dBm, 20 dBm, 24 dBm, 28 dBm and 32 dBm, respectively) in addition to the current separation distances at 4000 milliwatts (36 dBm). The proposed separation distances and methodology for determining them are discussed below. The Commission also proposes that a device be required to indicate to the white space database the power at which it will operate when it requests a list of available channels. The Commission further proposes that when a device operates between two defined power levels, it must comply with the separation distances for the higher power level.

23. The current maximum fixed device power level of 4000 milliwatts EIRP is based on a maximum conducted power of one watt (1000 milliwatts) into an antenna with a gain of 6 dBi (a factor of four). If the antenna gain exceeds 6 dBi, the maximum conducted power must be reduced by the amount in dB that the gain exceeds 6 dBi. We propose similar requirements for fixed devices that operate at power levels less than 4000 milliwatts EIRP. Specifically, the Commission proposes to define a maximum conducted power limit for each EIRP level, which would be 6 dB lower than the EIRP. In addition, because the power spectral density (PSD) limit for fixed devices is based on the maximum conducted power limit, the Commission proposes to define a PSD limit for each of the proposed conducted power levels. The Commission further proposes to calculate the PSD limit using the same methodology described in the
White Spaces Third MO&O,
77 FR 29236 (May 17, 2012). That is, the Commission will assume that the power of a device will be confined to a 5.5 megahertz band to allow a 250 kilohertz roll-off at the upper and lower edges of a channel to meet the adjacent channel emission limits. Consistent with the current rules, the Commission also proposes to require that the maximum conducted power and PSD limits for each EIRP level be reduced by the amount in dB that the maximum antenna gain exceeds 6 dBi. In addition, the Commission proposes that if a fixed device operates between these defined EIRP levels, the conducted power and PSD limits must be interpolated between the defined values shown.

24. The Commission seeks comment on the EIRP conducted power and PSD limits in proposals in paragraph 24 of the NPRM. In particular, it seeks comment on the usefulness of operation at the power levels proposed and whether there is a need to specify protection distances at additional power levels. The Commission also seeks comment on how the information on the power level and available channels should be communicated between the device and the database. For example, a fixed device could simply supply its geographic coordinates to the database, and the database could return a list of channels that indicates the maximum power at which the device could operate on each channel. Alternatively, the device could supply its locations and maximum power level and the database could return a list of available channels corresponding to operation at that location/power level combination. Are there other combinations of parameters for information exchange that would better suit such operation? What are the benefits and drawbacks of each alternative with respect to database operation and design and to equipment design? The Commission also seeks comment on the proposed PSD limits. Do these limits provide sufficient flexibility for device design and operation? Or would different limits be more appropriate? Commenters who advocate alternative limits and methodology should provide detailed technical analysis and justification to support their position.

(iii) White Space Devices in Rural Areas

25. The Commission seeks comment on a number of possible changes that could give more flexibility to operators of white space devices that would allow them to increase coverage and provide improved service in rural areas. For purposes of these proposals only, we use the term “rural” to refer to areas where there are numerous unused TV channels, which may be areas of low population density or areas that are merely under-served by broadcast services. In these cases, the potential for harmful interference from a white space device to a broadcasting station is significantly reduced. Specifically, the Commission seeks comment on whether to increase the limit on antenna height above ground for fixed devices in rural areas. The Commission also seeks comment on whether to allow higher power by fixed and personal/portable white space devices operating in rural areas. Finally, the Commission seeks comment on an appropriate definition of rural area for purposes of these proposals.

26.
Definition of rural area.
The part 15 rules do not define what constitutes a rural area. The Commission proposes to identify rural areas for white space devices as those where at least half of the TV channels are unused for broadcast services and available for white space use. At higher power, would fixed devices need to be located at a greater distance from a broadcast station contour, or would the fixed devices need to avoid operating on first, second or third adjacent channels? How might these factors affect the number and location of unused channels in identifying a rural area? The Commission seeks comment on the appropriateness of such a criterion or whether a different definition would better meet the needs of service providers. Because white space devices rely on a database to determine their list of available channels, the database would need to determine whether a fixed white space device is located in a rural area to allow such operation. Although the Commission believes that the white space databases already have the information needed to identify a rural area under the proposed criterion (
i.e.,
the identification of vacant TV channels at a given white space device location), the Commission seeks comment on what changes might be needed to implement this proposal, including the cost and programming complexity of such changes.

27.
Fixed device antenna height above ground.
The range at which a white space device could cause interference to authorized services increases as the antenna height increases. To limit this interference potential, the Commission established maximum height limits of 30 meters above ground level (AGL) and 250 meters HAAT for fixed white space device antennas. The Commission also established minimum required separation distances between white space devices and authorized services such as broadcast television that were determined based on the antenna height above ground and average terrain. The Commission adopted the 30-meter height above ground limit as a balance between increasing the white space device transmission range and the need to minimize the impact on licensed services. A higher antenna height above ground can improve signal propagation in suburban and urban areas by raising the antenna above obstacles such as trees and buildings. However, this increased signal propagation can also have a negative impact on spectrum sharing in congested areas where there are few available channels. The Commission stated that it could revisit the antenna height above ground limit in the future if experience with TV bands devices indicates they could operate at higher antenna heights without causing harmful interference.

28. A higher antenna height above ground could be beneficial in rural areas since an antenna could be mounted on a tower or other structure at a sufficient height to clear intervening obstacles such as trees and hills that would attenuate the transmitted signal. Increasing the antenna height could increase the maximum distance at which a signal can be received. There will generally be a significant number of available white space channels in rural areas, so there will not be the same concerns in those locations as in more congested areas about multiple users competing for spectrum. Since there are fewer authorized users of the spectrum in rural areas, there is a lower likelihood that an increased antenna height above ground will cause harmful interference. Accordingly, the Commission seeks comment on whether it should allow fixed white space device antennas at a height above ground of more than 30 meters in rural areas. If so, what is the maximum height that we should allow? What interference or spectrum sharing concerns would be raised by a higher antenna height above ground? Would we need to increase the minimum required separation distances to co-channel and adjacent channel television stations since the current distances assume a maximum antenna height above ground of 30 meters? If so, what are the appropriate separation distances? Similarly, should the Commission also consider increasing the HAAT limit for rural areas or keep that limit at 250 meters, but only allow a higher antenna height above ground level? What are the implications on interference distance from a higher HAAT limit along with a higher AGL limit?

29.
Power limit for fixed devices.
In adopting the four watt EIRP limit for fixed white space devices, the Commission recognized that there would be advantages to allowing operation of white space devices at higher power levels, such as reduced infrastructure costs and increased service range. However, the Commission decided not to allow the operation of fixed white space devices at power levels above four watts EIRP due to concerns about the increased risk of interference in congested areas that could make sharing spectrum between white space device users difficult. The Commission also stated that because it did not have experience with unlicensed wireless broadband operations in the TV bands, it would take a cautious approach in setting power limits to minimize the risk of harmful interference to authorized users of the TV bands. The Commission indicated that it would explore in a future proceeding whether higher powered unlicensed operation might be accommodated in the TV white spaces in rural areas.

30. The Commission seeks comment on whether it should allow fixed white space devices in rural areas to operate with up to ten watts EIRP, which could improve broadband service coverage in these areas. The Commission expects that equipment manufacturers can achieve this higher EIRP level by using higher gain antennas (10 dBi rather than 6 dBi), with no increase in the one watt conducted power level currently permitted. The Commission believes that requiring a higher gain antenna to achieve the higher EIRP as opposed to a higher transmitter power is appropriate for several reasons. First, it will result in more efficient spectrum use because the power from a higher gain antenna will be concentrated in a narrower beamwidth, thus reducing the likelihood of interference to authorized services and to other white space device users. Also, the Commission believes that use of fixed devices at these higher power levels would be limited to point-to-point type operations as it is unlikely that lower power personal/portable devices would be able to communicate over the increased distances.

31. The Commission seeks comment on the appropriateness of a ten watt power level and the degree to which it could help rural broadband operators improve or expand their service offerings to additional areas. What is the trade-off in terms of cost and system complexity of using a single high power fixed station as opposed to several lower power stations? The Commission also seeks comment on whether it should allow higher transmitter output power (
i.e.,
greater than one watt) as an alternative to, or in addition to, higher gain antennas. In addition, if we were to adopt rules for higher power, should we provide for intermediate levels between 4 and 10 watts EIRP? If so, what are the appropriate levels? The Commission further seeks comment on the impact of these proposed changes on authorized services in the TV bands. It recognizes that allowing a higher power level for white space devices will require greater separation distances from co-channel and adjacent channel TV stations. Would the methodology described below for determining such separation distances be appropriate for higher power white space devices in rural areas? Would we need to increase the minimum separation distance from protected services such as licensed wireless microphones, registered receive sites, and the PLMRS in addition to full power and Class A television stations?

32.
Power limit for personal/portable devices.
The Commission established a lower power limit for personal/portable devices (100 milliwatts EIRP) than for fixed devices (4 watts EIRP). The Commission adopted this lower limit because it found that personal/portable devices generally pose a greater risk of harmful interference to authorized operations than fixed devices because portable devices will change locations, making identification of both unused TV frequencies and the devices themselves, if harmful interference occurs, more complex and difficult. It further stated that the significant distances at which harmful interference could occur from a personal/portable device operating at greater than 100 milliwatts would make it very difficult to identify a device that is the source of harmful interference.

33. Higher power limits for personal/portable devices in rural areas could benefit the public by enabling applications that are limited or precluded by the current rules, such as mobile communications and vehicle tracking. We recognize the Commission's previous concerns with higher power limits for personal/portable devices. However, we believe that personal/portable devices may be able to operate at higher power levels in certain limited situations without a high risk of harmful interference to authorized services. Specifically, they may be able to operate at higher power in rural areas where there are a large number of TV channels available for white space use. In that situation, the risk of harmful interference to services operating in the TV bands is lower. Further, the rules contain detailed requirements for Mode II personal/portable devices that are designed to prevent harmful interference to authorized services. Specifically, they must: (1) Be capable of determining their position to within 50 meters; (2) re-check their position every 60 seconds; (3) access a database to determine the list of available channels at their location; and (4) re-check the database whenever they move at least 100 meters from their last location.

34. The Commission seeks comment on whether it should permit personal/portable devices to operate at higher power in rural areas. If so, what should be the maximum power at which they can operate? Should we limit higher power personal/portable devices to certain types of applications? If so, what applications? If we were to allow personal/portable devices to operate at higher power, would we need to adopt any additional requirements to prevent harmful interference to authorized services? If so, what requirements? For example, should personal/portable devices be required to comply with larger separation distances from authorized services than fixed devices operating at comparable power levels?

(iv) Channel Bonding and Out-of-Band Emission Limits

35. White space devices must comply with a three part out-of-band emission limit. First, they must comply with a power limit (conducted for fixed devices and EIRP for portable devices) in the television channels immediately adjacent to the channel in which the device operates. Second, they must comply with the § 15.209 radiated emission limits at frequencies beyond the television channels immediately adjacent to the channel in which the white space device is operating. Third, they must comply with stringent out-of-band emission limits on channels 36 through 38.

36. The Commission notes that the current out-of-band emission rules were written with the assumption that a white space device would transmit on a single six megahertz TV channel and meet the appropriate out-of-band emission limits at all frequencies outside of this single channel. However, a white space device could be designed to use two or more channels simultaneously to increase its transmission bandwidth and maximum data rate. A device could use multiple non-contiguous channels,
i.e.
channel aggregation, or could use multiple contiguous channels,
i.e.
channel bonding. There is no prohibition in the rules on the use of multiple channels by a white space device. In fact, the rules already implicitly allow the use of multiple channels by a single device since they specify the maximum power limits per six megahertz of bandwidth, indicating that a device may use multiple six megahertz channels. However, because the rules do not consider cases where a white space device transmits on multiple channels simultaneously, we believe that the current out-of-band emission rules in § 15.709(c) could be modified so that users could better make use of the efficiencies associated with channel aggregation and channel bonding. Channel aggregation and channel bonding will allow the development of devices that transmit at higher data rates, thus making higher speed equipment available to consumers.

37. The Commission, therefore, proposes several rule changes with respect to channel bonding. The Commission proposes to modify § 15.709(c)(1) to specify that the adjacent channel emissions limits do not apply within an adjacent channel that is being used by the same white space device, since in such cases there would be no TV station or other authorized service to protect on the adjacent channel; that is, to operate on two adjacent channels, a device would need to receive a message from a white space database that both channels are available at its location. Instead, the Commission proposes to apply these limits within the six megahertz bands immediately above and below the edges of the band of contiguous channels used by the white space device. The Commission also proposes to require that a device must meet the § 15.209 limits at frequencies more than six megahertz above and below the edges of the highest and lowest channels used in the device. The Commission further proposes to apply these requirements to fixed devices that operate centered on the boundary of two channels as proposed above, since that is a form of channel bonding. The Commission seeks comment on these proposals. In particular, it seeks comment on whether the white space databases will need to make any adjustments to accommodate channel bonding as proposed. Would

programming changes be necessary or should the logic to bond channels reside solely within a device based on the list of available channels obtained from the white space database? How easily can existing devices accommodate these changes or would new devices need to be designed?

38. With respect to channel aggregation, the Commission proposes to modify § 15.709(c)(2) to indicate that when a white space device transmits on multiple non-contiguous channels simultaneously, it must comply with the adjacent channel emission limits in the six megahertz bands above and below each of the single channels or channel groups used by the white space device. In such cases, the white space device would have to comply with the § 15.209 limits at frequencies outside of the channels used by the device and the six megahertz bands adjacent to the channels used by the device. The Commission seeks comment on this proposal.

39.
Adjacent channel emission levels.
In addition to our proposals to modify the adjacent channel emission rules to allow for channel bonding and aggregation, we are proposing to add emission limits for fixed devices operating at the proposed new power levels that are less than four watts EIRP. The Commission further proposes to correct the method of specifying the emission limits for fixed devices using a high gain (greater than 6 dBi) antenna.

40. In the
White Spaces Third MO&O,
the Commission decided to set the adjacent channel emission limit, measured in a 100 kHz bandwidth, as 72.8 dB below the maximum permitted power measured in a 6 MHz bandwidth. This results in an adjacent channel conducted emission limit of −42.8 dBm for the maximum permissible one watt (30 dBm) conducted power for fixed devices. Because the Commission is now proposing to define additional conducted power levels for fixed devices that are less than 30 dBm, we are proposing adjacent channel emission limits corresponding to these lower power levels. These proposed limits, shown in the table in paragraph 59 of the NPRM, are calculated using the methodology in the
White Spaces Third MO&O.
The Commission proposes that a device that operates between two defined power levels must comply with the limit for the higher power level.

41. The Commission seeks comment on the appropriateness of these limits. It recognizes that we could simply adopt the −42.8 dBm level for all power levels, but by providing flexibility based on power, our rules will provide for lower power white space devices to operate closer to the TV contours than higher power devices.

42. Similarly, the rules in § 15.709(c)(1)(i) do not compensate for fixed devices with antenna gains greater than 6 dBi where the device must operate by reducing its maximum conducted power by the amount in dB that the antenna gain exceeds 6 dBi. In such situations, the adjacent channel emission limits also need to be reduced because they are calculated relative to the maximum conducted power (
i.e.,
72.8 dB lower). The Commission therefore proposes to modify § 15.709(c)(1)(i) to require that the adjacent channel emission limits for fixed devices be reduced in the same manner as the in-band power,
i.e.,
by the amount in dB that the antenna gain exceeds 6 dBi. This approach is consistent with the methodology used to determine compliance with the power spectral density limit for fixed devices. The Commission seeks comment on this proposal.

43. In light of the proposals above, the Commission seeks comment on whether it should relax the current adjacent channel emission limits. Are these limits difficult to meet and does the necessary filtering increase the cost of equipment? Commenters advocating for less stringent adjacent channel emission limits are requested to provide proposals detailing different levels along with analysis showing the effect of TV reception, the potential interference to other authorized services in the band and any effect such changes would have on the required separation distance between white space devices and adjacent channel TV stations. For example, to compensate for less stringent out-of-band requirements we could increase the adjacent channel separation distances to TV station contours. What are the benefits of adopting such rules? And what would be the effect on the white space databases? Would devices need to transmit information regarding their out-of-band emission levels to the database to be used when calculating the list of available channels? Or could information regarding the capabilities of various devices reside in the database? How would such a scheme work? Another option would be to provide a range of adjacent channel emission limits with corresponding separation distances. The Commission seeks comment on this option and what benefits such flexibility would add. Or would the added complexity introduced to both devices and the database negates any potential benefits? Finally, the Commission seeks comment on the effect that less stringent adjacent channel emission limits would have on services and uses where there are no adjacent channel separation requirements, such as on wireless microphones or on TV stations adjacent to 40 milliwatt white space devices.

(v) Calculating the Separation Distances From a TV Station Contour

44. The rules require that white space devices protect defined service contours of analog and digital full service and low power television stations. These contours are calculated using the methodology in § 73.684 of the rules and the F(50,50) and F(50,90) curves contained in § 73.699. Under the current rules, fixed white space devices must operate outside the contours of co-channel and adjacent channel TV stations at the distances specified in the table in § 15.712(a)(2). This table provides co-channel and adjacent channel separation distances for nine ranges of fixed device HAAT, up to a maximum of 250 meters. Personal/portable devices that operate with an EIRP greater than 40 milliwatts, up to the maximum of 100 milliwatts, must comply with the co-channel and adjacent channel separation distances at the lowest HAAT in the table (
i.e.,
less than 3 meters). Personal/portable devices operating at 40 milliwatts or less only need to comply with the co-channel separation distance at the lowest HAAT listed in the table.

45. The Commission described the methodology it used to determine the table of separation distances in the
White Spaces Third MO&O.
Specifically, the Commission calculated the distances assuming a fixed white space device with an EIRP of four watts. It used a D/U signal ratio of 23 dB to protect co-channel TV reception, and −33 dB to protect adjacent channel TV reception. The Commission assumed that a TV receive antenna within a TV station's protected service contour would have a front to back ratio of 14 dB as specified in the DTV planning factors of OET Bulletin 69. Using these factors, it calculated the minimum required separation distances that a white space device must operate outside a TV stations' protected contour using the F(50,10) and F(50,50) curves over the range of antenna heights and distances at which these curves are defined. For HAAT values below 30 meters and for contour distances of less than 1.5 kilometers where the F(50,50) and F(50,10) curves are not defined, the Commission used the TM 91-1 propagation model to calculate the required separation distances.

46. The Commission is proposing to amend the table of separation distances in § 15.712(a)(2) to reflect the proposals above that would allow fixed device operation at a range of power levels below four watts EIRP. Requiring shorter separation distances for fixed white space devices with power levels below four watts will permit them to operate in more locations than the current rules allow,
i.e.,
closer to a television station service contour, since the current separation distances were based on the assumption that a fixed device always operates at the maximum power level. In addition, since the separation distances for personal/portable devices were also based on an EIRP of four watts, they are greater than necessary since personal/portable devices may operate with a maximum EIRP of 100 milliwatts, or 40 milliwatts if they are on a channel adjacent to an occupied channel. Because we are calculating separation distances for fixed devices at 40 milliwatts and 100 milliwatts EIRP, we propose to apply those separation distances, based on the lowest antenna HAAT, to personal/portable devices. This proposal will increase the number of locations where personal/portable devices may operate.

47. The Commission notes that the table of separation distances will increase in size due to the inclusion of additional power levels and therefore propose to split the table into two: one for co-channel and the other for adjacent channel separation distances. It also proposes to add an entry to show which separation distances apply to personal/portable devices, see table in paragraph 66 of the NPRM. The proposed co-channel separation distance table is as follows:

48. The proposed adjacent channel separation distances are shown in paragraph 67 of the NPRM. There is no entry for 40 milliwatt (16 dBm) devices because fixed and personal/portable devices operating at this power level would not have to meet adjacent channel separation distance requirements. This proposed table would correct an error in the current rules for the separation distances at the four watt power level. The Commission determined that the current separation distances were inadvertently calculated without considering the 14 dB receive antenna front-to-back ratio that the Commission previously stated it would use in determining these distances. Therefore, they are larger than they would be if the receive antenna directivity were taken into account. All of the distances in the following table were calculated using the 14 dB receive antenna front-to-back ratio.

49. The Commission seeks comment on this proposal. In particular, it seeks comment on whether these separation distances will provide adequate protection to co-channel and adjacent channel TV stations at the power levels and antenna HAATs listed. Parties that suggest changes to these distances should provide a technical analysis explaining their rationale. The Commission also seeks comment on the validity of the calculated prediction distances at low power levels (
e.g.,
40 milliwatts) and high HAAT. Is a 40 milliwatt white space device capable of causing interference to co-channel television stations at the calculated distances (over 12 kilometers at the maximum HAAT)? Do we need to consider the HAAT of low power white space devices?

50. In addition, we note that some parties have informally advised the Commission that they believe the Commission's current table of separation distances is overly conservative in some cases, and therefore limits the amount of white space spectrum available for unlicensed devices. The Commission therefore seeks comment on whether it should make additional rule changes with respect to the following issues.

51. Alternative propagation models for calculating interference. As discussed above, the Commission requires the use of the propagation curves in the rules for calculating the protected service contours of TV stations. Digital TV service contours are calculated using the F(50,90) curves, and analog TV service contours are calculated using the F(50,50) curves. Additionally, the table of separation distances between TV station service contours and white space devices was calculated using the F(50,10) and F(50,50) curves over the range where they are defined. Some parties have suggested that the Commission use other propagation models such as the Longley-Rice methodology or the Hata models to determine where white space devices could operate without causing interference to TV reception.

52. In seeking comment on alternative propagation models, we note that we are not proposing any changes to the method of calculating the protected service contours of TV stations using the F(50,90) and F(50,50) propagation curves. This is the method specified in the part 73 rules for calculating TV service contours, and we believe it is appropriate to require unlicensed white space devices to follow the same method for determining protected TV contours. In addition, the Commission do not believe the use of the Longley-Rice methodology would be appropriate for determining whether a white space device would cause interference to TV reception as it is computationally intensive and would significantly slow the determination of available TV channels by the white spaces databases.

53. With regard to the calculation of distances in the separation table, the Commission used a combination of its own propagation curves and the TM 91-1 to calculate separation the distances. It recognizes that this may not be the only appropriate methodology for calculating separation distances. We therefore seek comment on whether the Commission should consider using other propagation models that could give a more accurate indication as to whether interference is likely occur to TV reception. For example, are the Hata models appropriate for making these calculations? Are there other models that could be used? Could the separation distances calculated using other models provide a high degree of confidence that interference to TV would not occur? How would the separation distances obtained with an alternative model differ from those calculated with the methodology previously used by the Commission? Would the differences in these distances increase the amount of available white space, and if so, by how much?

54.
Directional antenna use by white space devices.
The Commission considered the directivity of TV receive antennas in developing the table of separation distances for white space devices and assumed a 14 dB front-to-back ratio. Because a TV receive antenna located just inside the protected contour of a TV station would be pointed toward the TV station, it would therefore be pointed away from a white space device located just outside the contour. However, the Commission did not consider the directivity of a white space transmit antenna in developing the table of separation distances and assumed an omnidirectional transmit antenna with a transmit power of four watts EIRP. The Commission stated that it was desirable to minimize the complexity for compliance while providing assurance that TV stations would be adequately protected. Likewise, when the Commission modified the table of protection distances in the
White Spaces Third MO&O
to allow white space device operation at higher antenna HAAT, it did not consider the directivity of the white space device transmit antenna.

55. The directional pattern of a fixed white space device transmit antenna could affect the identification of available channels. In the case where

the transmit antenna points away from a TV station that the white space device must protect, the effect would be that the white space device has a lower EIRP in the direction of the TV station. Under such situations it may be possible to reduce the required separation distance between the white space device and the protected contour of the co-channel and adjacent channel TV stations. This change could increase the number of locations where a fixed device could operate. However, there are a number of factors that have to be considered to ensure that white space devices provide adequate protection to TV stations. For example, antenna pattern information for fixed white space devices, including the orientation of the antenna as installed in the field would be needed. This information would then have to be stored in some format in the white spaces databases. The Commission would also have to develop appropriate protection criteria for a fixed white space device that uses a directional antenna. For example, we may need to specify the minimum arc size over which the power must be reduced in the direction of a protected TV station, since reduced power over a very narrow arc may not provide adequate protection.

56. Accordingly, the Commission seeks comment on whether it should modify the rules to consider the directional antenna pattern for fixed space devices. If so, how can we assure the accuracy of antenna pattern information? Should we require the database to store detailed information, such as the antenna gain at one degree intervals, or could we define several simpler generic patterns that approximate commonly used antennas? Should the database be responsible for storing various antenna patterns or should they be transmitted to the databases by the device at power up the first time it requests a channel list? How would we specify the appropriate protection criteria for white space devices using directional antennas? For example, could the protection distances proposed above for multiple power levels be used in conjunction with directional antenna information to protect TV reception? What other criteria would we need to specify?

(vi) Location Accuracy

57. A fixed or Mode II personal/portable device must be able to determine its position and provide that information to the white spaces database, which then determines whether the device meets the minimum required separation distances from protected services. The rules currently require that a fixed or Mode II personal/portable device incorporate a geo-location capability that can determine its geographic coordinates to within ±50 meters. GPS is capable of determining coordinates to this level of accuracy, but there may be circumstances where it is not possible to receive a GPS signal, such as indoors or at outdoor locations where there are obstacles such as buildings and trees. The Commission seeks comment on whether there are other location methods besides GPS that can determine a white space device's location to within ±50 meters. If so, what are these methods? The Commission also seeks comment on whether devices need to determine their position with this level of accuracy to protect authorized services.

58. In addition, the Commission seeks comment on whether we should allow white space devices to use geo-location methods that are less accurate than the current rules require, provided they provide the same level of protection to authorized services. If so, what level of accuracy should be required? How could we assure that devices with a lower level of geo-location accuracy do not cause interference to authorized services? Could we require white space devices to operate at greater distances from authorized services to offset the increased uncertainty in a device's location? If so, should we require all white space devices to meet increased separation distances, or only those with less accurate geo-location capabilities? If we allow only some devices to use a less accurate geo-location method, how could the white space databases take into account a device's geo-location accuracy in determining the list of available channels? The accuracy of some geo-location technologies, such as GPS, is well established, but this may not be the case for geo-location technologies, some of which may be proprietary, that manufacturers wish to use for white space devices. How should the location accuracy of a device be tested? Should manufacturers be required to certify the accuracy of the location technology incorporated into a device as part of the equipment certification process? Are there any other approaches that would allow white space devices to incorporate less accurate geo-location capabilities while still protecting authorized services?

2. 600 MHz Guard Bands

59. The 600 MHz Band includes a guard band between the wireless downlink services band and the TV band that will vary in size and frequency depending on the amount of spectrum recovered in the auction. There are three possibilities for the size of this guard band: 11 megahertz, nine megahertz and seven megahertz. However, if exactly 84 megahertz of spectrum is recovered in the auction, channel 37 plus the three megahertz guard band that protects the WMTS and RAS on channel 37 will serve as the guard band between the wireless downlink services band and TV band. Therefore, there would not be a separate guard band between the TV band and the wireless downlink services band that could be made available for unlicensed use as there would be under all other spectrum recovery scenarios.

60. The Spectrum Act states that the Commission may permit unlicensed use of the guard bands, and stipulates that (a) unlicensed use shall rely on a database or subsequent methodology as determined by the Commission, and (b) the Commission may not permit any use of a guard band that the Commission determines would cause harmful interference to licensed services. The term “guard band” includes the duplex gap, and thus the Spectrum Act's requirements discussed here apply equally to the duplex gap. Fixed and personal/portable white space devices clearly satisfy the Act's stipulation that “unlicensed use rely on a database” since our rules already require that these devices access a database to identify vacant TV channels in their area that meet the interference avoidance requirements of our rules, and they may only operate on the vacant channels that the database identifies. This Commission is proposing in this NPRM to expand the information in the white space databases to include 600 MHz Band services that will be entitled to interference protection. The Commission's part 15 rules already require that unlicensed devices not cause harmful interference to and must accept interference from authorized users. In this NPRM, the Commission proposes technical and operational rules for white space devices in these bands that will satisfy the requirements of both the Spectrum Act and our rules.

61. The Commission proposes to allow fixed and personal/portable devices to operate in the guard bands and duplex gap. The current white space rules provide for two types of personal/portable devices. Mode II devices, like fixed devices, incorporate geo-location and database access capabilities which facilitate their ability to meet the required separation distances at their operating location, while Mode I devices do not. Instead, Mode I devices must obtain a list of available operating channels from a fixed or Mode II personal/portable white

space device that is within their transmission range and may only operate so long as they can receive a controlling signal from the fixed or Mode II device. Because Mode I devices are limited to a maximum EIRP of 100 milliwatts, or 40 milliwatts EIRP if they are adjacent to an occupied TV channel, they must operate relatively close to the device that provides the list of available channels. Thus, the actual location of a Mode I device is different from the device providing it a list of available channels. The Commission seeks comment from parties contemplating use of Mode I devices on the types of functions and applications they envision for these devices, and the typical and maximum operating range envisioned for these devices. It also seeks comment on any studies that address the interference potential of Mode I devices. The Commission further seeks comment on whether it should limit operation in these bands to fixed and Mode II devices only to ensure protection to authorized services in these bands. Alternatively, should we also allow Mode I devices to operate in these bands, but increase the separation distances to offset the uncertainty in the devices' locations? In addition, the Commission seeks comment on whether any limitations on the types of devices in the duplex gap would be necessary after the 39 month transition period when all television stations are moved from the spectrum that is designated as the duplex gap. The Commission asks commenters to address the effect that any limitations on the permissible types of devices in these bands may have on the development of white space services and applications.

62. A white space device operating in a guard band would have to protect two different authorized services on frequencies immediately adjacent to the guard band. Broadcast television will operate in the lower adjacent spectrum, and licensed wireless downlink services will operate in the upper adjacent spectrum. The current rules permit operation of personal/portable white space devices on a channel that is immediately adjacent to an occupied TV channel, provided the device power is reduced to 40 milliwatts. In the NPRM, the Commission is proposing to also allow fixed devices to operate on a channel immediately adjacent to an occupied TV channel at the same 40 milliwatt power level, and it is proposing to allow fixed devices to operate at 4 watts EIRP three megahertz away from an occupied TV channel. However, the Commission does not currently have rules for white space devices that address operation on a channel immediately adjacent to wireless downlink services. Therefore, the Commission must develop rules to protect wireless downlink services adjacent to the guard bands, that is, protecting the ability of handsets to receive signals from a base station. The analysis discussed applies equally to the duplex gap because white space devices operating in the duplex gap must also protect wireless downlink services in adjacent frequency bands. The Commission proposes to protect wireless handsets by limiting the power of white space devices in the guard bands and duplex gap, and by requiring a buffer between the edge of the channel used by the white space device and wireless downlink services. The proposed approach ensures against harmful interference to licensed services and promotes the public interest and benefits inherent in maximizing spectrum use.

63. The Commission considers separately the guard band sizes under each of the spectrum recovery scenarios. In each case, we assume that the white space devices could be either fixed or personal/portable, that they will transmit over a six megahertz wide bandwidth, that they could be operating at 40 milliwatts immediately adjacent to an occupied TV channel, and that their operation will be controlled through use of a database. The power limits and frequency separation needed to protect part 27 wireless services will alter the assumptions for white space devices' power limits and bandwidth in each case and, ultimately, how white space devices could use the guard bands. Based on our preliminary analysis, discussed below, we also assume a three megahertz frequency separation between the white space devices and the handset receive band to offset a worst case interference distance of less than seven meters. Our preliminary analysis is based on conservative assumptions, and intended as a starting point for purposes of developing a record on these issues. There are numerous ways to conduct interference analyses and each depends on a number of assumptions, such as filter characteristics, the propagation model and miscellaneous losses (
e.g.,
body loss, polarization mismatch, etc.). In addition, the Commission notes that there is a lack of real world testing between white space transmitters and LTE receivers, and we invite manufacturers and other interested parties to submit data and test results to the record in this proceeding. Nevertheless, we believe that under reasonable conditions white space devices can operate in the duplex gap and guard bands without causing harmful interference to LTE receivers.

64. In the Incentive Auction proceeding, Qualcomm has submitted analyses purportedly showing that unlicensed use in the guard bands and duplex gap is not feasible without extremely large frequency separations from licensed services and Broadcom has submitted analyses to the contrary. Both parties' analyses rely on the 3GPP industry standards which define the onset of blocking interference at more than a five percent degradation in throughput. While the Commission does not go into the merits of these analyses here, our preliminary analysis also relies on the 3GPP standard for frequencies closest to the 600 MHz band as a starting point. However, the Commission notes that these standards contain minimum specifications and equipment used by wireless carriers may significantly exceed these minimums.

65. This standard sets a floor of −97 dBm for LTE receiver sensitivity and an adjacent channel selectivity of 33 dB. The Commission believes it is reasonable to assume at least 25 dB of additional loss over any path loss to include an additional 10 dB for adjacent channel selectivity plus an additional 15 dB of loss due to a combination of obstructions, body loss and antenna polarization mismatch, etc. The Commission further assumes a minimum of three megahertz frequency separation between white space devices and LTE receivers, resulting in a seven dB pass band filter attenuation. The Commission calculated the required separation distances using the TM 91-1 model. In doing so, it assumes a white space device with a maximum EIRP of 40 milliwatts and an antenna height of three meters, which is the lowest antenna height the part 15 rules specify for white space devices. The Commission also assumes a 1.5 meter LTE handset height, which we believe is representative of typical wireless handset use. Based on these assumptions, our calculations show a worst case interference distance of less than seven meters.

66. While the Commission recognizes there may be concerns about the potential for interference to wireless handsets at seven meters, we emphasize that our preliminary analysis is a static, worst case analysis that does not consider many other factors that would tend to reduce this distance. For example, it does not take into account the behavior of deployed networks which manage operating channels and

handset power in noisy conditions to ensure the best possible connection, nor does it take into account the probabilistic nature of the conditions that lead to an interference situation. For example, if an LTE handset is operating at the edge of coverage on a frequency at the edge of the band closest to the guard band in very close proximity to a white space device, the white space device, which must incorporate transmit power control, will limit its operating power to the minimum necessary for successful communication, so its power will often be less than the maximum on which we based our preliminary analysis. Additionally analyses that are based on the onset of blocking may not rise to the threshold of harmful interference if one considers transmission protocols and modulation schemes which are designed to facilitate operations when conditions are less than ideal by incorporating coding, bit interleaving, and retransmission events when necessary. Finally, the Commission notes that based on device and spectrum usage evolution, manufacturers have incorporated a range of unlicensed and licensed bands into devices and we expect that this will be the case with white space devices too. Given that there is some time prior to networks being deployed, we expect manufacturers to improve filter technology and designs to ensure a minimum potential for harmful interference.

67. In the guard band scenarios discussed, the Commission is proposing to allow white space devices to generally operate in the guard bands and the duplex gap at a maximum power level of 40 milliwatts and a three megahertz frequency separation from the handset receive band. The Commission seeks comment on this proposal. The Commission invites comment on the assumptions we make for wireless broadband service to the public by both licensed services and unlicensed devices. Parties that disagree are requested to provide their own assumptions, including what frequency separations are needed to protect wireless services from harmful interference, along with justification and analysis. The Commission also ask those parties who advocate against use of the guard bands for unlicensed use to provide details on what services they believe could operate there and under what operating conditions, so that valuable spectrum does not lay fallow. Parties should address how white space use in each scenario below would satisfy the Spectrum Act's requirement that no harmful interference is caused to licensed services.

68.
Eleven megahertz guard band.
Fixed and personal/portable white space devices could operate in the lower six megahertz portion of the guard band, adjacent to broadcast TV spectrum, leaving a five megahertz separation to wireless downlink services at the upper portion of the band. In this case, under the existing white space rules, the white space devices could operate at 40 milliwatts adjacent to an operating TV station and 100 milliwatts if the adjacent station is vacant. The Commission proposes that white space devices be permitted to operate at 40 milliwatts so long as it maintains a three megahertz separation distance from the lower edge of the band where handsets will receive. Is the 40 milliwatt power level useful for unlicensed devices? Should we permit operation up to 100 milliwatts if the white space device can maintain 4 or 5 megahertz separation from the handset receive band and satisfy the conditions for protecting TV reception as well as the necessary distance separation from adjacent base stations? Would a different power level be used?

69.
Nine megahertz guard band.
The Commission proposes that fixed and personal/portable white space devices could operate at 40 milliwatts in the lower six megahertz portion of the guard band adjacent to broadcast TV spectrum, leaving three megahertz separation to wireless services. The Commission believes this would adequately protect handsets from harmful interference while providing an opportunity for unlicensed devices to operate. The Commission seeks comment on this proposal and asks if there are other operating scenarios for the nine megahertz guard band that could be adopted to provide for unlicensed device use while protecting wireless handsets.

70.
Seven megahertz guard band.
In this case, if fixed and personal/portable white space devices operated adjacent to the broadcast TV band at the lower end of the guard band, there would be only one megahertz separation to wireless downlink services at the upper end of the band. Under this situation, could we provide for 40 milliwatt white space device operation? Alternatively, could white space devices operate at reduced power with only one megahertz of separation from broadband downlinks and still protect those operations? What power level and separation distance would provide for such operation? Another option is to restrict white space devices to a four megahertz bandwidth to maintain three megahertz separation from broadband downlinks. Is the current white space equipment capable of such operation? Is there a market for operating in this manner as it would necessitate slower data rates? What parameters in terms of power and separation distance would be required to ensure operation of all services? The Commission seeks comment on the appropriate power limits and frequency separations for white space devices to protect both TV and wireless services in this case.

71.
Three megahertz plus channel 37.
In the case where 84 megahertz of spectrum is recovered in the auction, the guard band between wireless downlink services and TV spectrum will consist of channel 37 plus a three megahertz guard band. The purpose of the three megahertz guard band is primarily to protect the WMTS and RAS on channel 37 from interference from wireless downlink services, but it also would protect wireless downlink services from harmful interference from white space devices operating on channel 37. If we determine that less than three megahertz separation is needed to protect part 27 services, could fixed or personal/portable devices make use of any portion of this three megahertz band? The Commission seeks comment on whether any types of low power, narrowband devices could use this guard band without causing harmful interference to licensed services in the adjacent bands. Is so, what types of devices and at what power levels and bandwidths?

3. 600 MHz Duplex Gap

a. Types of Permitted Operations

72. The 600 MHz Band includes a duplex gap of 11 megahertz between the wireless uplink and downlink services bands to prevent harmful interference between them. The frequency range of this duplex gap will depend on the outcome of the incentive auction, but the size of the band will be the same nationwide, regardless of whether there is any market variation in the amount of spectrum recovered in certain areas. Wireless downlink services will operate in the lower adjacent spectrum to the duplex gap, and wireless uplink services will operate in the upper adjacent spectrum to the duplex gap. In the
Incentive Auction R&O,
the Commission concluded that the public interest would be served by allowing broadcasters and cable programming networks to use wireless microphones on a licensed basis in a portion of the duplex gap and to obtain interference protection from unlicensed devices at specified times and locations, on an as-

needed basis. The Commission decided that it would in a future proceeding examine how best to provide access to a portion of the duplex gap by licensed wireless microphone users, while also ensuring that unlicensed users of the duplex gap can make use of this spectrum to provide broadband services. It anticipated that the duplex gap could be partitioned such that six megahertz would be available for unlicensed broadband devices to operate under the existing white space rules for 40 milliwatt personal/portable devices, and four megahertz adjacent to the wireless downlink services band would be available for licensed wireless microphone operations. This approach would leave one megahertz available for use as a buffer to protect licensed wireless services.

73. There are several different ways to divide the duplex gap to accommodate wireless microphones and white space devices, although there are trade-offs with each one. As an initial proposal, the Commission proposes to allow unlicensed operations, including both fixed and personal/portable white space devices and unlicensed microphones, to operate in the six megahertz band segment at the upper end of the duplex gap. It also proposes to allow licensed wireless microphones to operate in the four megahertz band segment immediately below this six megahertz segment. The Commission further proposes to use the remaining portion of the duplex gap spectrum to provide a one megahertz frequency separation between licensed wireless microphones and wireless downlinks in the spectrum below the duplex gap, thereby providing an additional margin of interference protection to mobile handsets. Thus, licensed wireless microphones would be able to operate in the band between one and five megahertz above the lower end of the duplex gap, and unlicensed devices, including wireless microphones, would be able to operate in the band from five to eleven megahertz above the lower end of the duplex gap.

74. The Commission believes that providing a six megahertz band for unlicensed devices is appropriate since that is the minimum size that many parties indicated is useful for unlicensed uses, and it is consistent with the current fixed and personal/portable white space rules. Additionally, it believes that a four megahertz segment of the duplex gap will be useful for licensed wireless microphones that are used on short NPRM since it will be available nationwide. Manufacturers have indicated that as many as 16 wireless microphones can operate in a six megahertz channel, and while we are proposing a smaller channel size here, manufacturers should still be able to get a substantial number of microphones to operate in it.

75. The Commission is not proposing to provide a guard band between licensed wireless microphones and unlicensed white space devices, since white space devices must comply with low emission limits outside their channel of operation. Also, wireless microphones that operate in this spectrum use narrow (no greater than 200 kilohertz) bandwidths and many can operate close together within a six megahertz channel, so we expect their receivers to have good selectivity. Thus, the Commission believes that there is a low risk of unlicensed white space devices causing interference to licensed wireless microphones in the adjacent band.

76. The Commission seeks comment on this proposal for partitioning of the duplex gap between licensed wireless microphones and unlicensed white space devices and unlicensed wireless microphones. Our proposed split maximizes the frequency separation between a six megahertz segment of the duplex gap for unlicensed use and wireless downlink spectrum, thereby reducing the risk of interference to those adjacent band services as required by the Spectrum Act, but it does not provide any frequency separation between the six megahertz unlicensed segment and wireless uplink spectrum used for base stations. The one megahertz separation at the lower end of the duplex gap provides an additional margin of interference protection to wireless handsets from licensed wireless microphones. The Commission also seeks comment on other possible partitioning scenarios and whether other approaches would provide interference protection to adjacent wireless uplink and downlink services while maximizing use of the spectrum. For example, should the one megahertz buffer be located at the upper end of the duplex gap? Is it needed to provide increased interference protection to wireless uplink spectrum from unlicensed operations operating in a six megahertz bandwidth? If so, how would this scenario affect the operation of licensed microphones in the lower duplex gap? Could licensed wireless microphones operate in the lower four megahertz portion of the duplex gap without a one megahertz buffer to separate them from wireless downlink spectrum? Would that approach increase the interference risk to either licensed wireless microphones or wireless downlink spectrum? Do we need a buffer at both ends of the duplex gap to protect both wireless uplink and downlink services? If so, what size buffers are appropriate and how would increasing the number or size of those buffers affect the available spectrum for unlicensed white space and wireless microphone users? For example, if we were to require a one megahertz buffer at each end of the duplex gap, should we allow only three megahertz of spectrum for licensed wireless microphones at the lower end of the duplex gap and six megahertz for white space devices and unlicensed wireless microphones at the upper end? Parties should address how white space use in each scenario above would satisfy the Spectrum Act's requirement that no harmful interference is caused to licensed services.

b. Technical Rules for Fixed and Personal/Portable Operations

77. The Commission proposes to allow fixed and personal/portable white space devices to operate in the six megahertz segment of the duplex gap described above with a power level of 40 milliwatts. This is consistent with our proposal to allow 40 milliwatt white space device operation in the guard bands. The Commission does not believe that a buffer is necessary to protect wireless uplink services above the duplex gap since the receivers of interest are those in base stations, and it expects there to be a greater separation distance from base station receivers than from mobile receivers, thus reducing the likelihood of harmful interference. The Commission seeks comment on this proposal. Is the 40 milliwatt power level useful for unlicensed devices? Would the proposed power level and frequency separation adequately protect wireless uplink services in the upper adjacent band? Do we need to limit the HAAT of fixed devices to minimize the possibility of interference to licensed services outside the duplex gap and licensed wireless microphones within the duplex gap?

4. Channel 37

78. The WMTS is used for remote monitoring of patients' vital signs and other important health parameters (
e.g.,
pulse and respiration rates) inside medical facilities. WMTS includes devices that transport the data via a radio link to a remote location, such as a nurses' station, which is equipped with a specialized radio receiver. WMTS operates licensed stations on three bands, including 608-614 MHz (channel 37) in the UHF band. Health

care institutions are required to register their locations and coordinate the use of all three bands through the American Society for Health Care Engineering (ASHE) of the American Hospital Association—the designated frequency coordinator—prior to commencing operation. This process minimizes the potential of WMTS users from causing harmful interference to, and receiving harmful interference from, other WMTS devices.

79. RAS is a receive-only service that uses highly sensitive receivers to examine and study radio waves of cosmic origin. There are twelve RAS telescopes that have been using channel 37 or plan to use channel 37 in the near future. Of them, ten comprise the National Radio Astronomy Observatory's (NRAO's) Very Long Baseline Array (VLBA), which are distributed in several locations in the United States and its territories, and collect simultaneous observations that are combined to emulate a single telescope 5000 miles in diameter. The remaining two telescopes are single dish instruments. The Commission protects RAS from in-band harmful interference by imposing field strength limits on WMTS and requiring coordination of WMTS use within certain distances of RAS observatories.

80. In the
Incentive Auction R&O,
the Commission decided to permit unlicensed operations on channel 37, subject to the development of the appropriate technical parameters for such operations to protect the WMTS and RAS from harmful interference. It stated that authorizing the use of channel 37 for unlicensed operations would make additional spectrum available for unlicensed devices in areas of the country that are not in close proximity to hospitals or other medical facilities that use WMTS equipment, or to RAS sites.

81. The Commission recognizes the importance of WMTS to patient care, and will remain mindful of this critical function when developing these technical parameters. In this NPRM, the Commission proposes technical parameters below to protect the WMTS and RAS from harmful interference and will develop a full record on the issues raised in this proceeding before adopting final rules.

a. Power Limits and Separation Distances

82.
General technical requirements.
There are several different approaches that could be taken regarding the types of white space devices that we would permit to operate on channel 37. The most cautious approach would be to limit operations on channel 37 to fixed devices only and to require registration of the locations where the devices are used in the white spaces database. Fixed devices are required to register their location and operator information in the white spaces database because the rules permit them to operate at higher power than personal/portable devices. The registration requirement makes fixed devices easer to locate in the event harmful interference occurs. Another approach would be to allow both fixed and Mode II personal/portable devices to operate on channel 37. Like fixed devices, Mode II devices must incorporate geo-location and database access capabilities. Unlike fixed devices, they are not required to register with the database since their maximum permitted power is lower than that allowed for fixed devices, and their operating location changes frequently. A third approach would be to allow fixed and both Mode I and Mode II personal/portable devices to operate on channel 37. Mode I devices are not required to incorporate a geo-location capability and obtain their list of available channels from a fixed or Mode II device that is within their transmission range. Thus, the separation distances we calculate below to protect the WMTS and RAS may need to be increased if Mode I devices are permitted to operate on or adjacent to channel 37.

83. The Commission seeks comment on the types of white space devices that should be permitted to operate on channel 37. If we allow personal/portable devices to operate on channel 37, should we require them to register with the white spaces database, and if so, what registration information should be required? What interference concerns are raised by allowing personal/portable devices on channel 37, and how could these be addressed, particularly those involving Mode I devices? Are there technology solutions or other means to mitigate the risk? Would we need to specify greater separation distances for personal/portable devices than for fixed devices of comparable power levels? If we initially allow only fixed devices on channel 37, should we then allow personal/portable devices at a later date once we have confidence that they will not cause harmful interference to the WMTS and RAS? The Commission seeks comment on any studies that address the interference potential of personal/portable devices to the WMTS and RAS.

84. The Commission proposes to allow the same maximum four watt EIRP for channel 37 fixed white space devices that is allowed for fixed devices in the TV bands. If we allow personal/portable devices on channel 37, we propose that the maximum EIRP would be 100 milliwatts, consistent with the current rules for operation in the TV bands. However, as discussed, these power levels may need to be reduced depending on what devices operate in the adjacent bands. The Commission also proposes to require white space devices on channel 37 to meet the other technical requirements for white space devices, including the conducted power, antenna gain and PSD limits as appropriate. The Commission further proposes that these devices must access a database over the internet to determine if channel 37 is available at their location, meaning that the location is sufficiently far removed from all WMTS and RAS sites to avoid causing harmful interference. The required separation distances are discussed in the following paragraphs.

85.
Power limits.
The maximum power at which an unlicensed device can operate may be limited based upon the need to protect authorized services in adjacent bands, in addition to services in the same band. For example, neither the current rules nor our proposals discussed above permit fixed devices to operate at four watts in bands immediately adjacent to occupied TV channels. Currently, the adjacent spectrum bands to channel 37 (channels 36 and 38) are allocated for TV broadcasting. After the incentive auction, this situation may or may not change depending upon the amount of spectrum recovered in the auction. There are three possible scenarios. First, if less than 84 megahertz of spectrum is recovered, channels 36 and 38 will continue to be available for TV broadcasting, so there will be essentially no change from the current situation. Second, if exactly 84 megahertz of spectrum is recovered, channel 36 will continue to be available for TV broadcasting, while channel 38 will not. Instead, there will be a three megahertz guard band directly above channel 37 which will separate channel 37 from licensed wireless downlink spectrum. Third, if more than 84 megahertz of spectrum is recovered, there will be three megahertz guard bands above and below channel 37 to separate channel 37 from licensed wireless downlink spectrum.

86. Under the first scenario, channel 37 in a particular location could be treated similarly to any other television channel, provided it is sufficiently far removed from the WMTS and RAS to avoid harmful interference. The Commission therefore proposes to permit fixed white space devices to operate with an EIRP of up to four watts

on channel 37, provided channels 36 and 38 are also vacant. If we allow personal/portable device operation, we propose that the maximum EIRP would be limited to 100 milliwatts in this scenario. In locations where channel 37 is available, but both channels 36 and 38 are occupied, the Commission proposes to allow a maximum allowable power of 40 milliwatts to protect television services on the adjacent channels. In locations where channel 37 is available, but only one of the adjacent channels is occupied, the Commission proposes to allow fixed unlicensed device operation with a maximum power of 4 watts EIRP, where the device operates in the six megahertz band centered on the boundaries of channel 37 and the unoccupied channel.

87. Under the second scenario (84 megahertz recovered), the Commission proposes to allow a maximum white space device power of 40 milliwatts EIRP on channel 37 to protect wireless downlink services that will be three megahertz above channel 37 and to protect television on channel 36 if that channel is occupied. If channel 36 is vacant, a white space device could also operate at 40 milliwatts, and possibly higher, in a six megahertz band centered on the boundary of channels 36 and 37, leaving a three megahertz separation from channel 35 and a six megahertz separation from wireless downlink spectrum.

88. Under the third scenario (more than 84 megahertz recovered), we propose to allow a maximum white space device power of 40 milliwatts on channel 37 where there will be a three megahertz guard band on each side of channel 37 to protect licensed wireless downlink services in the adjacent bands.

89. The Commission seeks comment on these proposals. In particular, it seeks comment on the appropriateness of the proposed power limits for white space devices in each of these scenarios. Should these limits be lower to reduce the likelihood of harmful interference to the WMTS, RAS and wireless downlink services? Conversely, could the proposed limits be higher without a risk of harmful interference? For example, could a white space device operate at power levels higher than 40 milliwatts under the second scenario with a three megahertz separation to TV and a six megahertz separation to wireless downlink services? If so, what is the maximum power that could be used? Should we allow a fixed device power limit on channel 37 that is higher than four watts in rural areas under those scenarios where we propose a four watt limit?

90.
Determination of WMTS separation distances.
WMTS systems typically consist of small patient-worn transmitters and receive antennas located within a healthcare facility. According to GE, WMTS transmitters are frequency-division multiplexed with typical occupied bandwidth of 10 kHz and a relatively low transmit power of less than 0 dBm (1 milliwatt) to extend battery life. GE argues that, to prevent interference to the WMTS, the signal level at the perimeter of a registered WMTS facility should not exceed 10 microvolts per meter within a 100 kilohertz bandwidth on channel 37, or 20 millivolts per meter within a one megahertz bandwidth on channels 36 and 38.

91. The Commission calculated the minimum co-channel separation distances that would be required for white space devices to meet GE's recommended field strength limit for channel 37. It used the TM 91-1 propagation model and white space device power levels that range from 40 milliwatts to 4,000 milliwatts in four dB steps. The Commission assumed that the WMTS transmitter would be at 10 meter height above ground, which is the highest height specified in the ASHE/AHA database, and used the same range of HAAT currently specified in the rules for fixed white space devices.

92. The Commission calculated the minimum required adjacent channel separation distances in two different ways using the same basic methodology that we used to determine the co-channel separation distances (TM 91-1 model, WMTS height of 10 meters, same range of white space device power and HAAT). First, it calculated the distances considering receiver “blocking” using the field strength limits on channels 36 and 38 that GE recommended to avoid interference. We then considered the out-of-band emission power that would fall into channel 37 from white space devices operating on channels 36 and 38 and calculated the minimum required separation distances based on GE's recommended field strength limit on channel 37. Based on our analysis, the effect of receiver blocking is greater than the effect of out-of-band emissions, so we considered receiver blocking in determining the minimum required separation distances.

93. The calculated co-channel and adjacent channel separation distances based on our methodology are shown in the two tables in paragraph 112 of the NPRM. These are the distances that would be required between a white space device and an individual WMTS receiver, and not the total distance that would be required to protect WMTS use that relies on large distributed antenna systems throughout buildings and that may be spread out across a large facility but represented by only single point in the database. The separation distances are rounded to the nearest tenth of a kilometer. In cases where the calculated adjacent channel separation distance is less than one tenth of a kilometer, we listed a separation of one tenth of a kilometer to avoid specifying extremely small distances. If we allow personal/portable devices on channel 37, the separation distances would be those at an HAAT of less than three meters at a power level of either 40 milliwatts or 100 milliwatts, depending on which authorized services are in the adjacent frequency bands. The Commission seeks comment on the appropriateness of these separation distances for protecting the WMTS as well as our methodology used to calculate them.

94. The current ASHE/AHA database allows the registration of only a single geographic point, whereas a hospital or health care facility is often a large building or group of building on a campus. The Commission also notes that GE stated that its recommended protection criteria for the WMTS should apply at the perimeter of a facility. For these reasons, the Commission expects that it will need to increase the calculated distances listed above to compensate for the fact that a single point may not accurately represent WMTS usage that could be spread out over a large facility. If so, what is the appropriate adjustment and why? For example, should we simply add an additional distance to our calculated distances? Alternatively, as discussed in the database section, should the Commission allow a facility to specify multiple points that define a bounded area around a large facility that uses the WMTS as opposed to specifying a single point?

95. The Commission also seeks comment on any ways it can simplify the process of protecting the WMTS. For example, there are thousands of registered WMTS sites, many of which are clustered close together in urban areas. Could we define exclusion zones in urban areas where operation is prohibited on channel 37 rather than requiring the databases to consider each individual WMTS location? If so, how should we define the exclusion zones and enter this information into the white spaces databases?

96. The Commission further seeks comment on whether there are any other requirements necessary to protect the WMTS. For example, would a limit on the HAAT of fixed devices on channel 37 reduce the potential for interference

to the WMTS? Should the Commission prohibit the operation of Mode I personal/portable devices on channels 36 and 38 since they rely on another device's geo-location capability and could possibly operate slightly closer to adjacent channel WMTS locations than the device that obtained the list of available channels? Alternatively, should the Commission limit operation on channel 36 and 38 to fixed devices only?

97.
Determination of RAS separation distances.
The Commission proposes different protection criteria for the ten VLBA stations than for the two single dish radio astronomy observatories because of their differing potential to receive interference. VLBA observations are less susceptible to interference than single dish observations because interfering signals do not correlate across the multiple receivers that comprise the array. The Commission proposes to require that white space devices operating on channel 37 comply with separation requirements based on their operating power to protect the ten VLBA observatories, and that they may not operate within defined exclusion zones around the two single dish observatories that receive on channel 37.

98. The Commission proposes requirements for white space devices to protect the VLBA based on the existing requirements that protect those stations from WMTS stations operating on channel 37. Section 95.1115(a) of the rules allows a maximum WMTS field strength on channel 37 of 200 millivolts per meter measured at a distance of three meters (this equates to an EIRP of approximately 12 mW). Further, § 95.1119(b) specifies that WMTS operations within 32 kilometers of the ten VLBA sites must coordinate with those sites. Using these two requirements as a basis, we can determine the minimum distance that a white space device must be from a VLBA site to provide the same level of protection as a WMTS transmitter located just outside the 32 kilometer coordination zone. Using the WMTS criterion, we calculate the appropriate path loss exponent to be 2.53. Therefore, the Commission proposes to calculate the separation distances between fixed white space devices and VLBA sites using a propagation model with a path loss exponent of 2.53. This model considers only the power of the white space device and not its antenna height above ground or average terrain.

99. Based on the foregoing, our calculated minimum co-channel separation distances between white space devices operating on channel 37 and VLBA sites are as listed in the table in paragraph 118 of the NPRM.

100. The Commission notes that in developing this table, factors which would act to shorten the protection distance such as buildings, mountains, trees or other ground clutter were not considered. In addition, because VLBA stations require very low noise environments, most have been constructed in remote areas that have substantial natural shielding due to the fore mentioned obstructions. Also, we note that most of these distances would be beyond the radio horizon for most, if not all, paths between white space devices and VLBA sites.

101. The Commission seeks comment on these separation distances and the methodology and assumptions used to calculate them. In particular, it seeks comment on whether these separation distances are appropriate for protecting the VLBA. Do they provide adequate protection to the VLBA? Are they greater than necessary to protect the VLBA? Should we place a cap on the maximum separation distances, such as 100 kilometers, to account for the fact our analysis did not account for any factors as mentioned above that would act to shorten the required separation distances and that radio astronomy sites will be beyond the radio horizon in most instances? Are the assumptions made in our analysis reasonable? For example, would a different propagation model or different protection criteria for the VLBA be more appropriate? Is so, what model or criteria should we use to determine the minimum separation distances? Commenters on this issue should provide detailed technical criteria and analysis to justify their position.

102. The Commission also seeks comment on whether it should establish adjacent channel separation distances between white space devices operating on channels 36 and 38 and the ten VLBA observatories. Under the current rules, white space devices cannot operate on these channels because they are reserved for wireless microphones if they are not being used by television stations. However the Commission will allow white space devices to operate on these channels if they are still available for television broadcasting after the incentive auction and are not being used by a television station at a white space device's location. Under the current rules, white space devices must operate at least 2.4 kilometers away from VLBA sites, so this requirement would apply to white space devices operating on channels 36 and 38. Is this adjacent channel separation distance adequate to protect the VLBA observatories? If not, what is the appropriate separation distance and why?

103. With respect to the two single dish RAS observatories that receive on channel 37 (Green Bank Telescope and Arecibo Observatory), § 1.924 of the rules defines coordination requirements to protect them. Specifically, § 1.924(a) requires parties planning to construct and operate a new or modified station at a permanent fixed location within a specified quiet zone around the National Radio Astronomy Observatory at Green Bank West Virginia to notify the observatory in writing of the technical details of the proposed operation. Similarly, § 1.924(d) requires parties planning to construct and operate a new station at a permanent fixed location on the islands of Puerto Rico, Desecheo, Mona, Vieques or Culebra to notify the Interference Office of the Arecibo Observatory in writing or electronically of the technical parameters of the planned operation.

104. Because the Commission does not believe it reasonable for operators of white space devices to coordinate with the Green Bank and Arecibo Observatories, and because separation distances to protect these observatories would be extremely large, the Commission is proposing that white space devices not operate on channel 37 within the National Radio Quiet Zone around Green Bank or on the islands of Puerto Rico, Desecheo, Mona, Vieques or Culebra. Much of the quiet zones are in less populated areas, and the Commission expects that in these areas there will be many other channels available for white space operation in addition to spectrum in the guard bands and duplex gap. However, the Commission seeks comment on whether there are ways to allow operation of white space devices on channel 37 within these areas. For example, are there coordination procedures that white space device operators and/or white space database administrators could follow to enable operation in these areas?

105. The Commission also seeks comment on whether it could establish minimum separation distances that white space devices must meet to protect the Green Bank Telescope and the Arecibo Observatory that would affect a smaller area than the existing quiet zones. If so, what are the appropriate interference assumptions, propagation model and separation distances? Because we are proposing protection criteria for white space devices over a range of power levels and HAAT, could we establish smaller exclusion zones for white space devices that operate at lower power levels or

lower HAAT? If so, how should we determine these zones or separation distances?

b. Guard Bands Adjacent to Channel 37

106. Under certain spectrum recovery scenarios, there will be a three megahertz guard band on one or both sides of channel 37, resulting in a contiguous block of nine or 12 megahertz of spectrum. The Commission seeks comment on whether these guard bands could be combined with the six megahertz of channel 37 spectrum in areas where it is not being used for the RAS and WMTS to create a wider band for white space device use. If so, what power level, frequency separation and other technical requirements would be necessary to protect wireless downlink services adjacent to these guard bands?

c. Out-of-Band Emission Limits on Channels 36-38

107. The Commission requires white space devices to comply with out-of-band emission limits on channels 36 through 38 in addition to the adjacent channel and § 15.209 limits that white space devices must meet on other channels. The white space device out-of-band emission limit on channel 37 is significantly more stringent (approximately 25 dB lower) than the Section 15.209 limit on this channel. Manufacturers must incorporate an additional band-reject filter into white space devices to comply with the limit on channel 37. The high level of attenuation needed to meet the limit requires a sharp roll-off across channels 36 and 38, which may extend as far as channels 35 and 37, potentially precluding the use of all four of those channels by white space devices. The emission limits on channels 36 through 38 were originally recommended by GE Healthcare to protect the WMTS from interference by personal/portable white space devices that could be used in close proximity to WMTS receive antennas. The Commission adopted these recommended limits and applied them to fixed devices as well as personal/portable devices.

108. The inability of white space devices to use channels 36 and 38 was not previously a concern since the rules did not permit their use by white space devices. However, in the
Incentive Auction R&O,
the Commission decided to stop reserving two vacant channels exclusively for wireless microphones and to make them available for both white space devices and wireless microphones, provided those channels are not repurposed for licensed wireless broadband use. At the same time, we can also take steps to ensure that channels 35 and 39 can be used by white space devices, provided those channels are available after the incentive auction. Additionally, because the Commission is allowing unlicensed devices to operate on channel 37, it needs to remove the stringent emission limit that applies on that channel.

109. The Commission is proposing to remove the out-of-band emission limits that apply on channels 36 through 38 and instead require white space devices to meet either the current adjacent channel or the § 15.209 emission limits as appropriate. Our proposal to allow white space device operation on channel 37 requires that the devices access a database to ensure that they will operate sufficiently far from both WMTS and RAS sites to avoid causing interference to these services. The database will enforce both co-channel and adjacent channel separation distances from the WMTS, which will ensure that emissions that fall within channel 37 do not cause harmful interference to the WMTS. Thus, there will no longer be a need for the more stringent out-of-band emission limits on channels 36 through 38. This proposed change will eliminate the need for white space devices to incorporate additional filtering that blocks channel 37 and impacts the first and second adjacent channels, thus making channels 35, 36, 37, 38 and 39 useable by white space devices. The Commission seeks comment on this proposal.

5. Repurposed 600 MHz Band

110. The Commission is proposing technical criteria for protecting licensed wireless services that will operate in the 600 MHz Band from interference from white space device operations. These criteria will be applicable in two situations. First, the Commission decided to permit the continued operation of white space devices in repurposed spectrum except in those areas in which a 600 MHz Band licensee commences operations. It took this action because it expects that 600 MHz Band licensees will be commencing operations at different places at different times, depending on their business plans and other factors, both during and after the post-auction transition period. Some of the repurposed television spectrum may not be used for licensed wireless services in some areas for a considerable amount of time.

111. Second, the Commission decided to allow market variation in developing the 600 MHz Band Plan. Therefore, some spectrum may be assigned for broadcasting in some areas and licensed wireless services in others. The Commission decided in the
Incentive Auction R&O
to allow the continued use of white space devices on all spectrum that remains allocated for TV broadcasting, which would include that spectrum with uses that vary by market. Since both white space devices and licensed wireless services can potentially operate on the same frequencies due to market variation, we need technical requirements to prevent harmful interference between the services.

112. The current white space device rules contain protection requirements for a variety of services that operate in the TV bands, but they do not contain protection requirements for licensed wireless broadband services as such wireless services did not operate in the TV bands at the time the Commission adopted those rules. Therefore, the Commission proposes to develop appropriate protection criteria, specifically, minimum distance separations, to protect these wireless services. These criteria will be used by the white space databases to ensure that unlicensed operations no longer occur on a channel in an area in which a licensee has commenced operations. When a 600 MHz Band licensee plans to commence operations on frequencies that includes spectrum available for unlicensed operations under the rules for white space devices, that licensee can notify any of the white spaces database administrators when and where it plans to commence operations. The white spaces databases would then preclude unlicensed operations in those areas on the channels in use for wireless systems. We discuss the proposed methodology that will be used to place 600 MHz Band licensee information in the databases below.

113. Consistent with our discussion above with respect to the guard bands and duplex gap, the Commission seeks comment on whether it should allow both Mode I and Mode II personal/portable devices, in addition to fixed devices, to operate in the repurposed 600 MHz band. The Commission asks commenters to address the effect that any limitation on the permissible types of devices in this band may have on the development of white space services and applications. For commenters that believe Mode I personal/portable white space devices should be permitted in these bands, the Commission seeks comment on the typical operating range of such a device, as that range will need to be incorporated into many of the protection distances proposed in the sections that follow. With respect to Mode II personal/portable devices, the current white space rules assume

protection distances for these devices based on them not operating above three meters HAAT. Thus, for all protection criteria that follows below, we propose that protection from Mode II personal/portable devices be based on operating at that low HAAT. The Commission seeks comment on this proposal.

114. Depending on the channel used by a white space device, it could be in the same band as either wireless uplinks or downlinks. Therefore, the Commission proposes co- and adjacent channel protection criteria for both wireless uplinks and downlinks.

115.
Wireless uplinks.
Wireless uplinks are the transmissions from mobile devices to fixed base stations. The receivers of concern in developing protection criteria are therefore those in fixed base stations. The Commission proposes that 600 MHz licensees provide information to the white space databases which defines a polygon representing the outer edge of their base station deployment. Using that information, the Commission proposes to protect fixed stations by determining the minimum separation distance needed between a white space device and that polygon to prevent harmful interference. Because the amount of spectrum available for white space dev

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2014-26674. Public record. Not legal advice.