**Before the**

**Federal Communications Commission**

**Washington, D.C. 20554**

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| In the matter of                 | *  | ET Docket No. 03-237         |
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| Establishment of an Interference | ** |                              |
| Temperature Metric to Quantify   |    |                              |
| and Manage Interference and to   | *  |                              |
| Expand Available Unlicensed      | *) |                              |
| Operation in Certain Fixed,      | ** |                              |
| Mobile and Satellite Frequency   |    |                              |
| Bands                            | *  |                              |
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**NOTICE OF INQUIRY**

**AND**

**NOTICE OF PROPOSED RULEMAKING**

**Adopted: November 13, 2003 Released: November 28, 2003**

**Comment Date: \[75 days from publication in the Federal Register\]**

**Reply Comment Date: \[105 days from publication in the Federal
Register\]**

By the Commission: Chairman Powell and Commissioner Copps issuing
separate statements. Commissioner Adelstein approving in part,
concurring in part and issuing

> a separate statement.

# INTRODUCTION

1.  By this action, the Commission seeks comment on a new "interference
    temperature" model for quantifying and managing interference. This
    new concept could shift the current method for assessing
    interference which is based on transmitter operations, to an
    approach that is based on the actual radiofrequency (RF)
    environment, taking into account the interactions between
    transmitters and receivers. The interference temperature model could
    represent a fundamental paradigm shift in the Commission's approach
    to spectrum management by specifying a potentially more accurate
    measure of interference that takes into account the cumulative
    effects of all undesired RF energy, *i.e.*, energy that may result
    in interference from both transmitters and noise sources, that is
    present at a receiver at any instant of time. This new approach
    could provide radio service licensees with greater certainty
    regarding the maximum permissible interference, and greater
    protections against harmful interference that could be present in
    the frequency bands in which they operate. In addition, to the
    extent that the interference temperature limit in a band is not
    reached, there could be opportunities for other transmitters,
    whether licensed or unlicensed, to operate in the band at higher
    power levels than are currently authorized. In such cases, the
    interference temperature limit for the band would serve as an upper
    bound or "cap" on the potential RF energy that could be introduced
    into the band. We therefore seek comment on the potential of this
    new approach to interference control and management to promote more
    efficient use of the spectrum and to possibly create opportunities
    for new and additional use of radio communications by the American
    public.

2.  The interference temperature concepts introduced in this proceeding
    were initially developed as part of the Commission's Spectrum Policy
    Task Force's (Task Force) work on means for improving the management
    of the radio spectrum to increase the public benefits derived from
    use of the spectrum resource.[^1] In its Report, the Task Force
    observed that interference management has become more difficult
    because of the greater density, mobility, and variability of RF
    transmitters and because users have been granted increased
    flexibility in using the spectrum.[^2] The Task Force presented
    several recommendations for improving interference management in
    this changed environment, one of which was for the Commission, as a
    long term strategy, to shift its paradigm for assessing interference
    towards an approach that uses real-time adaptation based on actual
    RF environments, and in particular to adopt a new "interference
    temperature" metric to quantify and manage interference.[^3] In
    response to the Task Force Report, a number of parties expressed
    general support for further analysis and study of the interference
    temperature concept.[^4] Other parties oppose the interference
    temperature concept as impractical and unworkable.[^5] We further
    note that the Commission's Technical Advisory Committee has
    concluded that introduction of the interference temperature concept
    is a reasonable approach to defining harmful interference as a
    function of how the spectrum is actually being used and the designs
    and margins of particular receivers.[^6]

3.  In the Notice of Inquiry (Inquiry) phase of this proceeding, we are
    requesting comment, information, and research on a number of issues
    relating to the development and use of the interference temperature
    metric and for managing a possible transition from the current
    transmitter-based approach for interference management to the new
    interference temperature paradigm. In particular, we are posing
    questions concerning the development of the interference temperature
    metric, including the determination of interference temperature
    limits for specific frequency bands, and an assessment of the
    cumulative noise and interference environment in radiofrequency
    bands, including standard methodologies for making assessments, to
    support the selection of those limits. We are also requesting
    responses on issues concerning the process that would be involved in
    possible transitioning to the new interference control methods in
    the various frequency bands.

4.  A general implementation of the interference temperature approach
    would involve planning, study of existing RF noise and interference
    levels and other factors, and transition processes that would take a
    substantial amount of time to complete. We seek comment on several
    steps we could possibly take prior to a general implementation that
    would bring elements of this new paradigm into use in the near term
    and thereby provide a test bed for this model that can be studied
    and evaluated before any broader implementation is considered.
    Therefore, in the instant Notice of Proposed Rule Making (NPRM)
    phase, we seek comment on technical rules that would establish
    interference temperature limits and procedures for assessing the
    interference temperature in specific frequency bands used by fixed
    satellite uplinks and by terrestrial fixed point-to-point links. We
    seek comment on whether the operating circumstances of these
    facilities would allow for simple and reliable measurement of the
    interference temperature at a variety of receive sites under diverse
    situations and circumstances. If we ultimately adopt new technical
    rules, we seek comment on whether unlicensed devices should be
    allowed to operate at higher power levels than currently allowed by
    the rules, so long as they do not cause the interference temperature
    to exceed the established limits.

    **BACKGROUND**

5.  The Commission's policies and rules for managing the radio spectrum,
    including its efforts to promote spectrum efficiency, traditionally
    have relied principally on approaches that manage interference by
    controlling the emissions and locations of transmitters and the
    frequencies used by specific types of radio operations. Under this
    model, the Commission has established operational parameters in
    portions of the spectrum in which the patterns of radio signals,
    both geographically and technically, are well understood and
    generally predictable by equipment manufacturers and licensees. In
    the past, this model generally served well to control interference
    and to facilitate effective use of the spectrum in environments in
    which the specific services and operating technology were stable and
    well defined. However, the dramatic increases in the overall demand
    for spectrum based services, rapid technical advances in radio
    systems, in particular the introduction of various advanced
    modulation technologies, the increased use of spectrum for mobile
    services, and the need for increased access to the limited supply of
    spectrum in recent years are straining the effectiveness of the
    Commission's longstanding spectrum policies in dealing with some
    allocations and applications.[^7]

6.  These changes are prompting the Commission to revisit its
    traditional model and evolve its spectrum management policies to
    consider more flexible and market-oriented approaches that can
    provide incentives for users to migrate to more technologically
    innovative and economically efficient uses of the spectrum. We need
    to provide opportunities for an ever increasing array of new digital
    radio technologies and services and to allow licensees to implement
    and modify these new technologies and services in accordance with
    the demands of market forces without having to wait for the
    completion of lengthy ad hoc rule makings or resolution of
    individual proceedings that hinge on disputes over interference. To
    meet these needs, we have implemented new licensing schemes under
    which bands of spectrum are assigned to licensees on a geographic
    basis and those licensees are provided flexibility to determine the
    type of services and the technologies and technical implementation
    designs used to provide those services. The primary restrictions we
    apply to technical operations under these licenses are those
    necessary to ensure that interference is not caused to services
    operating in adjacent geographic areas or in adjacent or nearby
    frequency bands. These restrictions typically take the form of
    limits on signal strength at the edge of a licensee's service area
    and limits on maximum transmitter power, antenna height and
    out-of-band emissions. These restrictions, in turn, tend to convey
    certain rights on the other neighboring or nearby licensees which
    are protected by such rules.

7.  To address the challenges of managing interference in radio
    environments that are increasingly being characterized by flexible
    service offerings with a multitude of signal waveforms and by high
    densities of low power RF transmitters with small signal ranges, the
    Task Force recommended that, as a long term strategy, where
    feasible, the Commission shift its paradigm for assessing
    interference to an approach that uses real-time measurements of
    actual spectrum use and adapt the responses of transmitters and
    receivers to these measurements.[^8] It observed that quantitative
    standards reflecting real-time spectrum use would provide users with
    more certainty and, at the same time, would facilitate enforcement.
    Noting that it is the ability of a receiver to select and receive a
    particular signal that determines whether a signal has been degraded
    by interference, the Task Force stated that the environment in which
    a receiver operates should be considered, *i.e.*, RF power generated
    by transmitters and RF noise sources that is present at the
    receiver. It further stated that the Commission's rules should
    specify a more accurate measure of interference that takes into
    account all the undesired RF energy available to be captured by a
    particular receiving antenna. To achieve this objective and provide
    for transition of interference management to more accurate real-time
    measurements, the Task Force recommended that the Commission adopt a
    new "interference temperature" metric to quantify and manage
    interference. To obtain data on the condition of the RF environment
    in each frequency band that would be used in setting temperature
    limits, the Task Force recommended that the Commission undertake a
    systematic study of the RF noise floor. It further recommended that
    the Commission adopt a standard methodology for measuring the noise
    floor and create a public/private partnership for a long-term noise
    (interference temperature) monitoring network and for the archiving
    of data, for use by the FCC and the public. Finally, the Task Force
    recommended that the Commission consider the use of receiver
    standards, especially voluntary standards, to further address
    interference,[^9] and a NOI released earlier this year by the
    Commission considers the likely costs and benefits of this potential
    tool for interference management.[^10] The Commission's
    consideration of an interference temperature is another step in this
    ongoing effort to develop a comprehensive and effective approach to
    interference management.

# 

# Discussion

8.  As part of our efforts to revise our spectrum management policies to
    address the changes in RF operations and environments that have
    occurred in recent years, we are now investigating alternative
    approaches for managing interference. We seek comment on whether it
    would be necessary to shift our current paradigm for assessing
    interference from approaches based primarily on transmitter
    operations towards new approaches that focus on the actual RF
    environment and interaction between transmitters and receivers, such
    as the interference temperature metric.[^11] Such new approaches
    could better allow the Commission to enable future uses of the
    spectrum, while possibly providing a greater degree of certainty to
    incumbents regarding the RF environment in which they will continue
    to operate. In the Inquiry portion of the discussion that follows,
    we first present a description of the interference temperature
    concept and how interference temperature limits could be used to
    manage interference. We then discuss and request comment,
    information, and research on issues relating to possible approaches
    for a general implementation of interference temperature limits,
    including questions concerning the development and implementation of
    the interference temperature metric, the means and criteria by which
    devices would comply with the interference temperature limits to
    provide real-time interference protection to licensed services, and
    methodologies for measuring the cumulative "background noise" and RF
    interfering signal levels in specific frequency bands and across the
    radio spectrum. In order to begin our exploration of the process
    that would be involved in a transition to an interference
    temperature regime, we seek comment on specific technical guidelines
    in the NPRM portion of our discussion that could be implemented in
    the near future for selected frequency bands prior to any possible
    general implementation of interference temperature limits and
    real-time adaptation of transmitters to the interference temperature
    environment.

9.  We seek comment on whether the Commission's approach for managing
    interference should be changed from its current methodology in order
    to address the changes in spectrum demand and RF operations and
    environments that have occurred in recent years. The *Task Force
    Report* recommended that the Commission evolve its spectrum policy
    toward more flexible and market-oriented spectrum policies that will
    provide incentives for users to migrate to more technologically
    innovative and economically efficient uses of spectrum.[^12]
    Although no single regulatory model can or should be applied to all
    spectrum to achieve these goals, the *Task Force Report* highlighted
    certain key elements. One such element is the provision of maximum
    feasible flexibility of spectrum use by both licensed and unlicensed
    users, subject only to those rules that are necessary to afford
    reasonable opportunities for access by other spectrum users and to
    prevent or limit interference among multiple spectrum uses.[^13] We
    seek comment on whether unrealized opportunities exist for
    unlicensed, low-power users to access spectrum, and whether changes
    to the Commission's approach for managing interference would enhance
    access to the spectrum by such users. We also seek comment on
    whether changes to the present method of interference management
    would reduce uncertainty that may exist for current licensees in
    terms of how much interference they will experience in their bands.

    A. Notice of Inquiry

10. *The Interference Temperature Metric and Interference Management*.
    For purposes of this new interference management paradigm, we define
    interference temperature as a measure of the RF power generated by
    undesired emitters plus noise sources that are present in a receiver
    system (I+N) per unit of bandwidth.[^14] More specifically, it is
    the temperature equivalent of this power measured in units of
    "Kelvin" (K).[^15] The emissions from undesired transmitters could
    include out-of-band emissions from transmitters operating on
    adjacent frequencies or in adjacent frequency bands as well as from
    transmitters operating on the same frequency as the desired
    transmitter. In principle, interference temperature measurements
    would be taken at various receiver locations and these measurements
    would be combined to estimate the real-time condition of the RF
    environment. The degree of certainty of the estimates would depend
    on such factors as the transmitter signal ranges, the uniformity of
    signal levels over an area, the density and location of temperature
    measuring devices and the sharing of the data taken by nearby
    devices; *e.g.,* through "*ad hoc* cooperative wireless networks."
    Measuring devices could be designed with features that include or
    exclude the energy contributions of particular signals with known
    characteristics; for example, the emissions of operations licensed
    to use the subject spectrum in a given geographic area.

11. For an interference temperature limit to function effectively on an
    adaptive or real-time basis, a system would be needed to measure the
    interference temperature in the band and communicate that
    information to devices subject to the limit, and a response process
    would also be needed to restrict the operation of devices so as to
    maintain the interference temperature at or below the level of the
    limit. In the simplest case, the entire process would take place
    within an individual device. That is, the device would measure the
    interference temperature at its location and make a transmit/not
    transmit decision based on this measurement plus the device's own
    contribution of RF energy. If the result of this analysis were below
    the interference temperature limit set for that location, the device
    would transmit. Another approach would be for the receive sites of a
    licensed service to measure the temperature and communicate those
    measurements to a central site, where the interference temperature
    profile for the region would be computed. A message could then be
    broadcast indicating the temperature values over that region and
    perhaps whether devices would or could not transmit on particular
    frequencies. This scenario may be appropriate in services such as
    those involving fixed point-to-point operations where there are
    relatively few receive sites in a given area.

12. A third more general case, might be to establish a grid of
    monitoring stations that would continuously examine the RF energy
    levels in specified bands, process that data to derive interference
    temperatures, and then broadcast that data to subject transmitters
    on a dedicated frequency, again perhaps with instructions how to
    respond. The transmitted temperature data from this monitoring
    system could also include the frequency and geographic location of
    the interference temperature measurement(s) and the measurement
    bandwidth so that an individual device could compute the rise in
    temperature due to its own contribution and make a decision to
    transmit. A somewhat simpler version of the monitoring grid concept
    might be to equip all transceivers on a network operating with
    interference temperature "thermometers" and GPS receivers so that
    they could measure and transmit temperature data on a real-time
    basis.

13. There are several actions that could be taken in the event that a
    device determines that its transmissions would cause the
    interference temperature limit to be exceeded. One approach would be
    to select a different transmitting frequency or, if none were
    available, to cease transmitting until the RF environment changed to
    a state in which a transmission would no longer cause an
    unacceptable temperature level. Another approach would be to reduce
    the transmitter power and/or change the direction or shape of the
    transmit antenna pattern. These capabilities could be implemented by
    equipping devices with technology such as automatic transmitter
    power control (ATPC) or with the ability to electrically re-shape
    antenna patterns. Combining these approaches, a single device could
    be designed to scan the range of potential operating frequencies
    before transmitting, compute an estimate of the amount that their
    operation would add to the interference temperature on each
    frequency, and select among the frequencies that would allow
    compliant operation. The device would monitor the interference
    temperature and if the observed level began approaching or exceeded
    the limit, could lower its power, switch to another frequency, make
    an antenna adjustment, or cease transmitting as conditions might
    warrant.

14. More complex responses than those described above could be taken
    when considering a coordinated monitoring system. In such a
    scenario, responses could range from a requirement that all
    undesired transmitters cease transmitting, to limitations on the
    number of devices that could operate or the permitted transmitter
    power, or to restrictions on the operation of unlicensed devices to
    specific areas. Any of these limitations could be imposed
    separately, in tandem, and/or on a priority basis. In cases where
    devices subject to the temperature cap were not equipped to respond
    on a real-time basis, actions to ensure the environment remained in
    compliance with the temperature limit could involve restrictions on
    sales of additional devices if the temperature approached the limit.
    Alternatively, a process might be established whereby users
    registered their devices with an appropriate agent who could then
    inform them to take actions to reduce the interference temperature
    if needed. In addition, devices could be built to automatically
    respond to messages distributed through the local mass media
    services. Two possible examples include messages that could be
    embedded in the subsidiary communications authority (SCA) subcarrier
    transmissions of FM radio stations or within the ancillary data
    services of broadcast TV signals. Many other variations and options
    are possible for optimizing the monitoring and response process to
    avoid exceeding the temperature cap.

15. Figure 1 shows how the interference temperature limit approach could
    be beneficial to licensees.[^16] This figure shows the signal of a
    radio station designed to operate out to a range at which the
    received power approaches the level of the noise floor that existed
    at the time the system was built. As additional interfering signals
    appear, the noise floor has increased at various points within the
    service area, as indicated by the peaks above the original noise
    floor.[^17] As a result, the station's service reliability and
    signal coverage have been reduced. The establishment of an
    interference temperature limit would fix the amount of new
    interference that the station could experience. That is, the station
    would be assured of providing service at all locations where its
    signal exceeded the level of the interference temperature cap.[^18]
    This would assure that the licensed operation would not experience
    any further degradation or loss of service from new interference,
    and thereby provide incumbents greater certainty regarding the
    maximum permissible level of interfering RF energy in the bands in
    which they operate. Interference temperature limits could also serve
    as a "worst" case characterization of the RF environment that would
    provide benchmarks of the operating environment for equipment and
    system designers. This could aid designers in balancing the numerous
    technical and economic tradeoffs involved in radio system planning.

16. This approach could also be beneficial for users of unlicensed
    devices. In areas where the interference temperature would not have
    been exceeded, opportunities would exist for additional operation by
    "underlay" transmitters equipped to monitor the interference
    temperature and to control their operations so that they do not
    contribute to a condition where the interference temperature cap
    would be exceeded. Thus spectrum access for unlicensed users and
    devices would be increased.

17. We also inquire as to the potential costs and benefits of a policy
    establishing an interference temperature. In particular, we seek
    comment on the likely costs and benefits to licensees, equipment
    manufacturers and other potentially affected entities that could
    result from the use of the interference temperature approach or
    other interference management tools. How would the costs and
    benefits of an interference temperature approach compare to the
    costs and benefits under the Commission's current spectrum policy?
    In addition, we seek comment on whether and how the interference
    temperature approach could change the current legal framework,
    regulatory process and general enforcement of rules designed to
    prevent harmful interference. As we have experienced in recent
    proceedings involving interference disputes, we recognize that this
    new approach to interference management could also present issues of
    competing rights and interests. However, the Task Force Report
    suggested that clearly defined rights and responsibilities for all
    spectrum users, particularly with respect to interference and
    interference protection, should be considered and established to the
    extent possible and practical.[^19] We seek comment as to how the
    Commission can accomplish this objective and avoid long, drawn out
    interference disputes without detrimentally affecting reasonable
    expectations of all interested parties, including expectations
    regarding the Commission's use of its authority to impose
    conditions, modify licenses and take other steps to promote greater
    access to, and more efficient use of, the spectrum.

18. *Issues Concerning the General Implementation of Interference
    Temperature Limits*. We request comment on using interference
    temperature limits to manage interference. In this inquiry, the
    Commission views as two key considerations the potential for
    unrealized opportunities for unlicensed, low-power users to access
    spectrum, and the need to provide greater certainty for licensees in
    terms of how much interference they will experience. Interested
    parties are invited to submit suggestions for enhancing or modifying
    the general plan presented above or for alternative approaches.
    Noting that the Spectrum Task Force indicated that this approach may
    not be feasible in all bands, commenters are also encouraged to
    present plans that would tailor interference temperature to specific
    services. We also request comment and suggestions on how to
    implement such a plan so as to maximize the benefits for all
    parties, that is, to protect licensees from interference, provide
    meaningful benchmark information for equipment and system
    designers/manufacturers, and opportunities for new operations,
    including those of unlicensed devices. Commenting parties are also
    asked to submit information, to the extent it may be available, on
    the value of these benefits to the respective affected parties.

19. We realize that an approach that uses real-time adaptation based on
    actual RF environments has not been done in the past and therefore
    represents a fundamental shift in spectrum management. Although it
    would be ideal to test this new approach in a frequency band without
    incumbent services, this is not possible. As technology advances to
    higher and higher frequencies, investments in infrastructure
    communications, such as point-to-point systems, point-to-multipoint
    systems and satellite systems, have to keep ahead of the low-cost
    technology that is the back-bone of consumer electronics. As a
    result there are no unoccupied frequency bands within the range of
    frequencies where low-cost consumer applications can be easily
    manufactured. Therefore, this new approach must be tried in
    frequency bands where a significant investment in incumbent
    communication systems already exists. We request comment on how this
    concept could be used to promote more efficient provision of service
    on a licensed basis and how this should be done. More specifically,
    how could this approach be used with licensing approaches that make
    spectrum available on 1) an exclusive basis and 2) a coordinated
    (shared) basis? Also, what approaches would best allow the
    Commission to transition to spectrum management by the interference
    concept in existing occupied spectrum bands?

20. In addition to seeking comment in this Notice on the feasibility of
    using this new concept as a general approach to spectrum management,
    we seek comment on two frequency bands in which it is more feasible
    for unlicensed devices to be expanded without causing undue
    interference to the incumbent licensees. With respect to these bands
    we ask some general questions:

-   Is there is a general metric that can be used to gauge the success
    of the introduction of the interference temperature devices into a
    new frequency band?

-   Is there a simple metric that can be used to gauge the effect of
    these unlicensed devices upon the incumbent services?

-   Should the introduction of interference temperature devices be done
    in stages to ensure that the incumbent services do not suffer undue
    interference?

-   If the introduction were to be done in stages how should we limit
    the initial introduction of interference temperature devices to
    protect the incumbent systems?

21. We request comment on what technological factors should be
    considered in setting interference temperature limits. In general,
    we would expect that licensees would prefer to see the interference
    temperature limits in the bands they use set low, while
    manufacturers and users of unlicensed devices would prefer to see
    these limits set high. In this regard, we request comment on the
    following questions:

-   What elements should the Commission consider in setting temperature
    limits for different bands and locations? The Task Force suggested
    that some of the factors to be considered in setting temperature
    limits for a band include: 1) the extent of current use; 2) the
    types of services being offered; 3) the types of licensees (for
    example, public safety); 4) the criticality of services and their
    susceptibility to interference; 5) the state of development of
    technology; and 6) the propagation characteristics of the band. We
    request comment on whether these factors are appropriate as well as
    whether other criteria also should be addressed.

-   In addition, commenters should address what, if any, technical
    factors (*e.g.*, power, field strength at boundary areas, antenna
    requirements, etc.) should be considered in determining the
    interference temperature limits for a given service, frequency band
    and geographic area.

-   What applications are expected to be filled by unlicensed devices
    operating under the interference temperature metric?

-   Should factors not specified by the Commission's rules, such as
    typical modulation types for a given service, be considered? If so,
    commenters should identify these factors and the rationale for
    including them.

-   How should the factors identified be used to determine interference
    temperature limits? That is, should each factor be considered
    equally or are some more important than others? Can an equation be
    developed that uses the identified factors to calculate a
    temperature?

-   Should all the identified factors be used in all cases? Should some
    factors only be used in some cases? Commenters should provide
    detailed explanations for including or excluding specific factors in
    various analyses.

-   In bands where several services share the spectrum on a primary or
    secondary basis, should the interference temperature limit be based
    on all the licensed services or only on the service most susceptible
    to interference? How would this be determined? Is the I+N of a
    primary service meaningful to a secondary service?

-   Are there minimum receiver performance criteria that should be
    considered as a reference in setting interference temperature
    limits? If so, how should the specifications for such a reference
    receiver be developed? Or should the Commission use the worst
    receiver available for a service, or an average receiver, in
    determining temperature limits? How would such a receiver be
    identified?

-   To what extent should noise and emissions from existing licensed and
    unlicensed transmitters be a factor in setting interference
    temperature limits? Should the highest current level of I+N be used
    as a minimum meaningful level for the interference temperature limit
    or some other statistical representation of measured values?

-   What entities should be parties to the process of setting
    interference temperature limits? What process should these entities
    follow in determining the temperature limit for a specific band
    (*e.g*., each entity gets an equal vote, some entities' votes have
    more weight than others, etc.)?

-   Should the Commission allow private agreements between licensed and
    unlicensed users to set interference temperature limits for specific
    bands and frequencies? If so, are there incentives the Commission
    could/should provide to licensees to increase the temperature limit
    over that set by the Commission?

-   How often should interference temperature limits be reviewed?

-   What processes should the Commission establish for modifying
    interference temperature limits? In such cases, what criteria should
    the Commission consider, how should it weigh those criteria, and who
    should be parties to modification processes?

-   Are there some services or bands for which the Commission should
    continue to use the current interference protection procedures?

22. We also request comment on the approaches to be used for measuring
    interference temperature on a real-time basis and, in the case of
    temperatures derived from measurements at multiple sites,
    communicating that information to devices that are required to
    protect the limit. In this regard, we ask commenting parties to
    address these questions and issues:

-   How should the Commission decide on the type of interference
    temperature monitoring to be required to provide real-time
    interference control? Commenters should identify the costs and
    benefits of the three monitoring approaches discussed above and how
    they relate to different services. Commenters are also encouraged to
    identify other monitoring approaches.

-   Should certain monitoring schemes be specified for certain services?
    Or should this be solely up to the incumbent licensees?

-   How would monitoring systems be funded and who would be responsible
    for their establishment, operation, and maintenance? Commenters
    should consider vendors or operators of unlicensed devices and
    network services, users of such equipment and services, and perhaps
    licensees.

-   What principles/criteria would be used to choose the location of
    monitoring sites?

-   How often should the spectrum be monitored? How large a band should
    be monitored? How should monitoring differ with the type of
    incumbent services present in a band? What bandwidth should be used
    for monitoring (*e.g*., should measurements be taken with a
    resolution bandwidth of 1 megahertz)?

-   What detection functions, e.g., root mean squared (RMS), peak or
    average, should be applied in performing noise measurements? What
    integration or averaging time should be employed with these
    measurements? What measurement bandwidths are appropriate?

-   How would the information from monitoring sites be used to determine
    real-time interference temperature values for a specific band in a
    given geographic area and whether established limits were exceeded?

-   What spectrum resources should be used to convey monitored
    temperature information to devices subject to temperature limits?
    Should dedicated frequencies be used for this purpose?

23. We further request comment on the actions that devices subject to
    compliance with interference temperature limits should take if the
    applicable interference temperature limit is exceeded. In
    particular, we seek comment on the state of development of sensory
    and control equipment that could appropriately govern the action of
    emitters in response to real-time interference temperature data,
    *e.g.*, automatic transmitter power control systems. In addressing
    the following questions, commenters should seek to balance the
    requirement that the temperature limits are not exceeded against the
    need for devices to maintain communications.

-   What response should a device take if it determines that exceeding
    an established interference noise temperature limit, *e.g.*, change
    frequency, reduce power or place itself in a stand-by mode? Should
    this response be different if the offending device is a stand-alone
    device or a device designed to respond to a monitoring system?

-   Should a graduated response system be used (*i.e.*, should a device
    iteratively take measures to bring the interference temperature back
    into the compliant range or should the strongest measures be taken
    first)?

-   If many devices are operating, is it possible to assign
    responsibility to specific devices if the temperature limit is
    exceeded and have those devices take measures to ensure that the
    temperature is brought back to a compliant level?

-   Once an offending device takes measures to bring the temperature
    back to a compliant level, what protocols should be used to
    determine when that device may resume operating?

-   How should noise temperature limits be enforced? Has technology
    progressed to the level that the limits could be self-enforced by
    the radio emitters?

24. *Noise Floor Measurements*. The effective functioning of
    interference temperature limits as a useful tool for managing
    interference depends on an understanding of the condition of the RF
    environment, *i.e.*, the noise floor. For purposes of the
    interference temperature metric, we believe noise ("N") should be
    defined as the cumulative environmental RF energy that is generated
    by sources external to an operator\'s receiving equipment and
    generally present in the area around the receiver's antenna.[^20]
    This noise is generally produced by atmospheric conditions, galactic
    sources, and man-made incidental and unintentional radiators.[^21]
    Specifically excluded from this measure would be all emissions from
    intentional radiators, *i.e.*, transmitters, as the emissions from
    such devices can more properly be termed "interfering signals"
    ("I"), rather than sources of background noise.

25. Noise floor data is useful for assessing the amount of background
    noise and interference a service is receiving in an area and the
    variability of those energy sources over both time and location.
    This information can then be compared to the operating power and
    receiver performance characteristics of the licensed services to
    estimate service ranges and the service margin. These estimates can
    be used to determine whether a service operation is relatively
    fragile (low margin) or robust (high margin). These estimates of
    margin can provide an indication of whether a given operation can
    tolerate additional undesired RF energy from new unlicensed devices
    or other sources. Where a service has a high service margin, we
    would generally expect that the interference temperature could be
    set relatively high (*i.e.*, a significant amount above the noise
    floor). Conversely, where a service has a low service margin, we
    would expect that the interference temperature would be set low.

26. We request comment on how to define the noise floor and whether
    there are considerations that would justify using slightly different
    definitions for different bands and/or services. We also request
    comment, information, and research on the levels of the noise floor
    in the various frequency bands and how those levels vary over time
    and across geographic regions. While noise floor information is
    useful in administering our interference temperature limits, we also
    recognize that measuring and monitoring the noise floor is a
    substantial, time-consuming, and, in most cases, resource intensive
    undertaking. We therefore request comment and suggestions for
    methods to collect this information on a timely, cost effective
    basis or to develop acceptable estimates of this information from
    methods other than continuous direct measurement and monitoring. We
    further request comment and suggestions for standard methodologies
    for collecting and estimating reliable noise floor data that would
    be consistent with our goals of obtaining this data on a timely and
    cost effective basis. Commenters should be specific regarding the
    techniques used to measure the noise floor (*e.g*., providing
    information regarding spectrum analyzer settings, amount of time
    monitored, location, etc.).

27. *Determining Harmful Interference*. It is essential to quantify
    harmful interference in order to develop specific interference
    temperature levels. Once a level of harmful interference is
    determined for a specific service, then an interference temperature
    limit can be set such that any normal increases in the noise floor
    would not rise to that level. It is important to note, however, that
    harmful interference is defined by our rules as interference that
    causes serious detrimental effects as opposed to interference that
    is merely a nuisance or annoyance that can be overcome by
    appropriate measures.[^22] Furthermore, it is a fundamental reality
    that every radio communication system must work in the presence of
    some amount of RF noise and interference. Consequently,
    communication system designers typically incorporate some built-in
    operational margin that maintains reasonable performance in the face
    of variables such as anticipated interference/noise levels,
    component degradation over time, temperature-related circuit
    fluctuations, the impact on signal levels from the weather, and the
    like. In other words, the system design must include some reasonable
    margin for acceptable performance in a changing environment.
    Ultimately, however, harmful interference cannot occur if the
    interference is below a system's threshold of operation. Thus, we
    seek comment on whether a modest rise in the noise floor, such as
    envisioned by the interference temperature concept, would generally
    not cause harmful interference as defined under our rules.

28. More generally, interference can be characterized as an emission
    from a transmitter that impedes reception of a desired signal to a
    given recipient. However, as noted above, interference is only
    considered harmful if it rises to a certain level. In this context,
    we ask commenters to address the following questions:

-   For a given service in a given frequency band, how much interference
    can be tolerated before it is considered harmful? If the
    determination of harmful interference would be based on specific
    quality of service levels, we request comment on the rationale used
    to justify the recommended constraints. The commenting parties
    should note the specific frequency bands and services to which their
    comments apply.

-   When performing interference studies, what assumptions should be
    made regarding operating scenarios? For example, commenters should
    address the duty cycle to be assumed for the desired and undesired
    transmitters. What assumptions should be made about whether and/or
    what percentage of antennas might be aligned under typical operating
    conditions such that there is main beam coupling between undesired
    transmitters and desired receivers?

-   Can interference from a transmitter be distinguished from naturally
    occurring noise?

-   Can a statistical approach to developing temperature limits be
    developed? If so, what parameters need to be developed? How would
    such an approach be applied?

-   Should the interference temperature limit be set at level that
    quantifies "harmful interference" or some other benchmark, or
    "safe-harbor" level that would constitute less than harmful
    interference?

B. Notice of Proposed Rule Making

29. *Introduction*. As explained above, we seek comment on whether the
    interference temperature concept potentially could offer many
    benefits for management of the radio spectrum. We recognize,
    however, that it will take a significant period to develop the
    underlying information, analyses and policy plans needed to fully
    implement the interference temperature concept across all feasible
    frequency bands. In this regard, the study of noise floors in the
    various frequency bands, the establishment of interference
    temperature levels and related policies, and the development of
    transition processes will require substantial effort and time to
    complete. Furthermore, additional time will be needed to develop and
    implement the monitoring networks, technologies, and devices such as
    those described above for detecting and relaying interference
    temperature information to central control stations that would
    forward this information to transmitters to control the level of RF
    emissions.

30. Nonetheless, we also seek comment on whether it may be feasible and
    desirable to begin the process of introducing the interference
    temperature approach on a limited basis now in selected bands, even
    as we begin the study and development activities that will support
    the more general implementation of this new paradigm. In this
    regard, we seek comment on if it is possible to first introduce the
    interference temperature concept on a limited basis without full
    implementation of real-time monitoring of the interference
    temperature or feedback control of transmitters and prior to
    completion of our studies of the noise floor. The approach used in
    this first step would establish an "interference temperature" or
    equivalent metric based upon the communications margins needed by
    the existing licensed operations and apply restrictions on
    unlicensed devices that would minimize the likelihood that their
    operation would result in an increase in interference temperature
    that could exceed the necessary operating margin of the licensed
    services. The proposed restrictions on unlicensed devices would
    include limiting the transmitter output power and requirements to
    use transmit power control (TPC) and dynamic frequency selection
    (DFS). In addition, other requirements that might prove beneficial
    could include limits on the number of unlicensed devices, as well as
    duty cycle restrictions that would insure that these initial
    interference temperature experiments do not cause harmful
    interference to licensed services. As noted above, we seek comment
    on how these first steps could provide additional opportunities for
    operation of unlicensed devices and, perhaps more importantly,
    provide valuable information and experience to guide our formulation
    of approaches in the next phases of this effort.

31. *Discussion*. As discussed more fully below, we propose to apply the
    new interference temperature approach described herein to unlicensed
    operation within the fixed (FS) and fixed satellite service (FSS)
    uplink band at 6525-6700 MHz and the FS, FSS, and BAS/CARS band at
    12.75-13.25 GHz (excluding 13.15-13.2125 GHz). These bands were
    chosen because we believe they offer the possibility to implement in
    a simplified way the interference temperature concept and approach.
    We seek comment on the appropriateness of these bands and whether
    additional frequency bands could be suitable for testing the concept
    of interference temperature.

32. In this regard, we believe that it is beneficial to look at
    frequencies where FSS satellite uplinks are the predominant use. In
    those instances, the licensed receiver being protected is located on
    the satellite in space. Consequently, the receiver would not be
    located in close proximity to any potentially interfering unlicensed
    device. Given the significant distances involved and the typical
    satellite antenna characteristics, the satellite receiver would
    "see" the cumulative effect of the RF signals from all unlicensed
    devices on the ground. Therefore, it is possible to develop a
    simplified interference temperature approach for the satellite
    receiver and FSS uplink operations by aggregating the interference
    contributions of a large number of unlicensed devices over a wide
    geographic area.

33. More specifically, as indicated in the Notice, interference
    temperature is a measure of the RF power generated by undesired
    emitters plus noise sources that are present at the input of a
    receiver system (I+N) per unit of bandwidth.[^23] In the case of
    satellite receivers, we note that the typical receiver noise
    temperature is a known parameter that can be used to determine an
    interference temperature threshold. Indeed, this parameter is the
    basis of the ∆T/T criterion used by the International
    Telecommunications Union (ITU) to determine whether coordination
    between systems is required.[^24] Furthermore, as noted above, since
    a satellite-based receiver will generally \"see\" large geographic
    areas of the CONUS, it is possible to analytically aggregate the
    impact of a large number of unlicensed devices on the ∆T/T
    criterion. \[See Appendix B\] Given this knowledge of the satellite
    receiver's noise temperature characteristics, it is possible to
    examine, as we do below, what number and power levels of unlicensed
    operations could be accommodated without, in the aggregate,
    resulting in a ∆T/T value for the satellite receiver that exceeds a
    selected interference threshold. In other words, in scenarios where
    protection of satellite receivers is of concern, we believe that use
    of a ∆T/T criterion could serve as a reasonable mechanism for
    approximating a first-step "interference temperature" limit - but
    without relying upon adaptive, real-time monitoring that would be
    used in a full-fledged approach.

34. We also believe that bands used for certain terrestrial fixed
    operations would be suitable for our first-step implementation of
    the interference temperature concept. The key simplifying benefit of
    dealing with fixed operations is the fact that such operations are
    generally static and well-defined such that reasonable assumptions
    can be made about their locations and technical characteristics. In
    these bands, fluctuations in the interference temperature can be
    compared to fluctuations in C/(I+N) or (S/I). Given a knowledge of,
    for example, the S/I characteristics of typical receivers, it is
    possible to examine what maximum power levels could be accommodated
    for an unlicensed device without exceeding the signal margins
    required for satisfactory operation and therefore without causing
    interference to such services. Once a value for the interference
    threshold of a typical licensed receiver is established through
    consideration of the required signal margins, it is possible to
    utilize a measurement of the ambient fixed signal levels to
    determine whether operation of an unlicensed device of known
    characteristics would exceed the "interference temperature" signal
    threshold for a licensed receiver. This transmit/not transmit
    decision could be made in real-time by unlicensed devices that
    incorporate DFS.[^25] As implemented here, the DFS threshold of an
    unlicensed device would be adjusted so that the device would not
    transmit if the detected fixed signal level exceeds an established
    threshold. In this manner, the DFS threshold is functionally
    equivalent to the interference temperature limit. Consequently, the
    transmit/not transmit decision made by the DFS feature ensures that
    the S/I or other chosen metric for licensed receivers is not
    adversely impacted.

35. *Proposed Bands*. Using the concepts described above for a ∆T/T
    limit for satellite uplink operations and a DFS threshold for other
    services, we propose to apply the new interference temperature
    approach described herein to unlicensed operation within the FS and
    FSS uplink band at 6525-6700 MHz and the FS, FSS, and BAS/CARS band
    at 12.75-13.15 GHz and 13.2125-13.25 GHz.[^26] This action could
    enable higher power and more diverse unlicensed operations in these
    bands and create opportunities for new technologies. For example, we
    believe that these bands could be useful for many consumer and
    business unlicensed applications, such as high-speed data and video.
    Further, we believe that the incumbent operations in these bands can
    tolerate an expansion of unlicensed operation, both in number of
    devices and their power without suffering harmful interference.

36. *Incumbent Operations in the Proposed Bands*. The 6525-6700 MHz band
    is allocated internationally and domestically to FS and FSS
    (Earth-to-space) operations on a primary basis for non-Federal
    Government use. However, this band is predominantly used for FS
    operations. These FS operations consist of the Domestic Public Fixed
    Radio Services, the International Fixed Public Radiocommunication
    Services, and the Fixed Microwave Services under Parts 21, 23, and
    101, respectively, of our regulations. The services in this band are
    typically provided by, among others, industrial, governmental and
    transportation related licensees. Finally, we note that the
    6650-6675.2 MHz segment of this band is used by the radio astronomy
    service.[^27] The 12.75-13.25 GHz band is allocated internationally
    and domestically to FS, FSS (Earth-to-space), and mobile services on
    a primary basis for non-Federal Government users.[^28] In addition,
    this band is assigned and coordinated through the Interdepartment
    Radio Advisory Committee (IRAC) for Federal and non-Federal
    Government use for space research (deep space) (space-to-Earth) on a
    secondary basis.[^29] The band currently supports a variety of
    different systems operating pursuant to each of these allocations.
    These systems include both geosynchronous orbit (GSO) and Non-GSO
    (NGSO) satellite systems under Part 25 of our rules, broadcast
    auxiliary systems (BAS) under Part 74 of our rules, cable TV relay
    systems (CARS) under Part 78 or our rules, and fixed microwave
    systems under Part 101 of our rules. Because of the extensive
    sharing of high power systems already present in these bands, we
    believe that additional unlicensed devices, even those operating
    above the current Part 15 power limits, will be able to successfully
    share spectrum with incumbent users using this new interference
    temperature approach. [^30]

37. The technical rules for these bands vary by service. In broad terms,
    fixed stations operating in the 6525-6700 MHz band as well as BAS,
    CARS, and FS stations operating in the 12.75-13.25 GHz band may
    operate at power levels up to 85 dBm equivalent isotropic radiated
    power (EIRP).[^31] These stations are required to employ directional
    antennas. FSS satellite uplinks have no limit on transmitted power
    in the direction of the satellite, but must limit EIRP toward the
    horizon.[^32] Mobile stations can operate with EIRPs as high as 75
    dBm.[^33] In contrast, the current rules limit unlicensed operation
    in the 6525-6700 MHz and 12.75-13.25 GHz bands to emissions of
    -41.25 dBm, which is 126.5 dB lower than the maximum emission level
    permitted for fixed BAS, CARS, and FS stations.[^34] Therefore, in
    light of the great disparity in magnitude between permissible
    emission levels for licensed versus unlicensed devices, sound
    engineering judgment intuitively suggests that the 6525-6700 MHz and
    12.75-13.25 GHz bands can support expanded unlicensed operations
    enabled by an interference temperature approach without detrimental
    impact to incumbent operations.

38. *Use of ΔT/T Limit for FSS Operations in the 6525-6700 MHz and
    12.75-13.25 GHz Bands*. With regard to the protection of licensed
    FSS uplink operations and satellite receivers, we believe that
    establishing a ΔT/T threshold as described generally above could
    serve as an effective "interference temperature" limit. In
    particular, our preliminary analysis indicates that a large number
    of unlicensed devices operating with EIRP emission levels possibly
    as high as 30 dBm to 36 dBm (1 W to 4 W) could be accommodated
    without exceeding a reasonable ΔT/T "interference temperature"
    threshold that might be established for FSS systems.[^35] A sample
    link budget analysis that illustrates the potential for these bands
    to accommodate additional uses is presented in Appendix B. We note
    that the results obtained are based on an assessment of an
    acceptable level of aggregate interference threshold of 5% for
    ΔT/T.[^36] This particular interference value was chosen because it
    is less (i.e., more conservative - or more protective) than the 6%
    ΔT/T figure used by the ITU for requiring coordination between
    satellite systems, recognizing the generally lower regulatory status
    of Part 15 devices.[^37] We seek comment on an appropriate
    interference temperature threshold that will afford sufficient
    protection to licensed satellite operations, and in particular on
    whether the 5% value used in Appendix B, or another value of ΔT/T,
    for example 3% or 1%, would be more appropriate. We also seek
    comment on the various assumptions made in the link budget analyses
    appearing in Appendix B, particularly concerning the power emission
    distributions and other technical characteristics of hypothetical
    unlicensed operations in the band.

39. We also believe that FSS sharing with unlicensed operations is
    facilitated by the way licensed satellite facilities operate in
    these bands. As mentioned above, the use of these bands is limited
    to international systems for GSO satellite systems and to gateway
    stations for NGSO satellite systems. We request comment on our
    assumptions and general analysis regarding sharing between
    high-powered unlicensed devices and satellite uplinks. If commenters
    believe that the analysis is flawed or should be conducted
    differently or by using different assumptions, we request detailed
    technical explanations and accompanying analysis to support these
    claims. In addition, we do not believe that our proposals will be
    detrimental to the space research operations at Goldstone, CA.[^38]
    Because Goldstone is located in a rural location with natural
    shielding by virtue of its location in a valley, very few, if any,
    unlicensed devices would be operated in locations that could impact
    its operation. We request comment on this tentative conclusion.

40. *Use of DFS Threshold for FS Operation in the 6525-6700 MHz and
    12.75-13.25 GHz Bands*. With respect to terrestrial fixed systems in
    these bands, a number of considerations support our belief that
    establishing a DFS threshold for unlicensed operations as described
    generally above could serve as an effective \"interference
    temperature\" limit. First, we note that significant sharing among
    licensed FS operations currently exists at the much higher power
    levels previously cited. More specifically, we believe that the use
    of relatively large, high-gain antennas in the 6525-6700 MHz and
    12.75-13.25 GHz bands by existing licensees makes such operations
    highly immune to interference -- especially from the relatively low
    power unlicensed devices contemplated by this proceeding. Second,
    due to the generally isolated siting of fixed point-to-point receive
    antennas, it is expected that the likely minimum separation distance
    between the antenna of a fixed point-to-point receiver and an
    unlicensed device would typically be relatively large, perhaps on
    the order of one hundred meters or more. Thus, the emissions from
    any unlicensed transmitter could be expected to be greatly
    attenuated before reaching an FS receive antenna. For example, if an
    unlicensed transmitter operating at 6600 MHz is located 100 meters
    from the fixed station receiver, the unlicensed emission will be
    attenuated by approximately 89 dB before it reaches the

fixed station receiver.[^39] Similarly, if an unlicensed transmitter
operating at 13 GHz is located 100 meters from the fixed station
receiver, the unlicensed emission will be attenuated by approximately 95
dB before it reaches the fixed station receiver. Third, we believe that
the divergent path geometries that are likely to occur between a
typically sited FS antenna and a close-proximity, ground-based,
unlicensed transmitting antenna will result in most unlicensed devices
being located considerably farther than 20 degrees off-axis from the
centerline of any FS receive antenna. At an off-axis angle of 20 to 30
degrees, fixed stations operating in the 6525-6700 MHz band are required
to attenuate emissions by 32 to 36 dB and stations operating in the
12.75-13.25 GHz band are required to attenuate emissions by 30 to 36 dB,
depending on the antenna category.[^40] We also recognize that it is
possible that an unlicensed transmitter could be located, for example,
within a building and that a fixed station receiver could be located on
top of that building. Under these circumstances, the straight-line path
length between the licensed and unlicensed antennas in this latter
example could be relatively short. However, the high level of shielding
of the unlicensed emission provided by the building and the expected
high angular off-axis location of the unlicensed emitter from the fixed
station receiving antenna should provide sufficient attenuation to the
unlicensed emission to prevent it from causing harmful interference.

41. We believe that our assumptions above regarding minimum separation
    distances and off-axis locations from the FS receive antenna are
    conservative. It is likely that greater separation distances would
    occur under actual operating conditions. Further, we recognize that
    unlicensed devices would not all be in operation at the same time;
    would not have their emissions intentionally directed towards the
    fixed service receiver; and could have different path attenuations
    due to varying intervening objects between them and the FS receiver.
    We also believe that the unwanted emissions received by the FS
    receiver will be dominated by the emissions from the closest device
    and that the real-world antenna off-set attenuation values will be
    greater than the minimum values required under our regulations.
    Accordingly, we believe that our assumptions are conservative and
    represent worst case, as opposed to typical, conditions. We seek
    comment on the validity of these general assumptions. More
    specifically, using these figures as a proposed starting point, we
    seek comment on what amount of attenuation and assumed minimum
    typical separation distance would provide an appropriate baseline
    for deriving interference temperature values to protect licensed
    services from harmful interference.

42. We also note that the minimum signal to interference (S/I) ratio
    necessary to prevent harmful interference to a fixed station is
    dependent on the type of modulation employed by the fixed station.
    Some systems, especially those employing error correction codes and
    other interference mitigation techniques are highly robust and can
    operate in the presence of an undesired signal that is considerably
    higher than the level of the desired signal without experiencing
    harmful interference. In view of the typical usage by FS stations of
    low modulation indices and/or amplitude modulation, our general
    experience indicates that a S/I ratio in the range of 30 dB to 50 dB
    should be more than sufficient to ensure that harmful interference
    is not caused to a fixed service operation.[^41] Comments are
    requested on the appropriate minimum S/I value to use and under what
    circumstances. Comments supporting particular minimum S/I values
    should provide examples of the necessary minimum S/I of existing
    systems in their analysis. We also ask that commenting parties
    include a description of how the appropriate choice for an S/I
    threshold might vary with changes in the type of modulation employed
    by the undesired emissions as well as any supporting test data.

43. For illustrative purposes, combining these assumptions in a link
    budget analysis indicates that an unlicensed emitter 100 meters away
    from a 6525-6700 MHz FS receiver should be able to transmit at a
    power level of as much as much as 91 dB to 71 dB higher than the
    level it receives from an FS transmitter without causing harmful
    interference to the associated FS receiver.[^42] Similarly, an
    unlicensed emitter 100 meters away from a 12.75-13.25 GHz FS
    receiver should be able to transmit with a power level of as much as
    95 dB to 75 dB higher than that received from the FS transmitter
    without causing harmful interference to the associated FS receiver.
    [^43] Thus, if the FS signal level at the unlicensed device is -77
    dBm, the unlicensed devices should be able to transmit with a
    minimum signal level of 14 to -6 dBm in the 6525-6700 MHz band and
    18 to -2 dBm in the 12.75-13.25 GHz band without causing harmful
    interference to FS reception. This would hold true even if the
    unlicensed transmitter is operating on a channel currently in use by
    a fixed station. We seek comment on the merits of this tentative
    result as well as on the validity of our rationale. Commenters may
    wish to explore whether other approaches could be used to derive
    appropriate values for an interference temperature limit in this
    band.

44. Furthermore, if unlicensed devices were designed to first monitor
    (*e.g.*, listen-before-talk, or "sniff") the authorized spectrum to
    determine the levels of existing RF emissions, they could employ DFS
    to adjust their frequency of operation to ensure that operation
    occurs on unoccupied channels.[^44] The detection threshold employed
    within the DFS could be adjusted to accommodate the overhead margins
    for unlicensed operations calculated above to ensure that the
    emissions from the unlicensed emitter do not exceed the interference
    threshold at the fixed receiver. We seek comment on requiring a
    minimum DFS detection threshold of -64 dBm for unlicensed devices
    operating at output levels equal to or exceeding 23 dBm and -62 dBm
    for unlicensed devices operating at output levels below 23 dBm. We
    further propose that the detection threshold is the received power
    averaged over 1 millisecond referenced to a 0 dBi antenna. We note
    that these values generally are consistent with our proposals for
    DFS employed with UNII operation proposed in the 5470-5725 MHz band
    and believe these levels would provide adequate protection to FS
    operations at 6 and 13 GHz.[^45] We seek comment on the merits of
    and potential problems that might arise from using this real-time
    monitoring approach. Comments are also sought on alternative methods
    that could be employed to monitor the RF spectrum signal levels and
    to control the interference temperature.

45. By employing TPC and DFS and by permitting unlicensed operation at
    very modest power levels (as indicated above, we envision maximum
    unlicensed EIRPs possibly in the range of 30 dBm to 36 dBm), we
    believe that sharing between unlicensed devices and these incumbent
    systems is feasible. We observe that these systems have been able to
    share in the past by conducting frequency coordination prior to
    operation. We believe that the use of TPC and DFS can automatically
    mimic this function, but in real time as opposed to manual human
    coordination activities. We further observe that the significant
    power difference between incumbent terrestrial systems and proposed
    unlicensed devices puts the unlicensed devices at considerably more
    risk of receiving interference than of causing interference. We
    request comment on these observations and seek proposals for
    appropriate technical criteria. Specifically, we seek comment on the
    proper detection thresholds that should apply for DFS. Should the
    threshold be referenced to the received power averaged over one
    millisecond referenced to a 0 dBi antenna? Or should some other
    reference be used? Detailed technical comments should be submitted
    to support commenters\' positions. Comments also are requested on
    the bandwidth and time period over which we should require that the
    spectrum be monitored prior to operation. Also, commenters should
    provide details regarding how often the spectrum should be monitored
    after transmission begins. We also request comment whether the TPC
    capability should be required to reduce power by more than 6 dB
    below the maximum power? If so, to what level? What are the limits
    of current technology for TPC?

46. We request comment on these observations and seek proposals for
    appropriate technical criteria for operation in this band.
    Specifically, we seek comment on the proper detection thresholds
    that should apply for DFS. Should the threshold be referenced to the
    received power averaged over one millisecond referenced to a 0 dBi
    antenna? Or should some other reference be used? Detailed technical
    comments should be submitted to support commenters\' positions.
    Comments also are requested on the bandwidth and time period over
    which we should require that the spectrum be monitored prior to
    operation. Also, commenters should provide details regarding how
    often the spectrum should be monitored after transmission begins. We
    also request comment whether the TPC capability should be required
    to reduce power by more than 6 dB below the maximum power? If so, to
    what level? What are the limits of current technology for TPC?

47. *General In-band Considerations*. We also seek comment on the
    general in-band technical requirements that would be appropriate for
    unlicensed operations in the 6525-6700 MHz and 12.75-13.25 GHz bands
    under an interference temperature paradigm. For example, Section
    15.402 of the Rules sets forth various limits on the maximum
    transmit power, the maximum spectral power density, and other
    related technical limits for unlicensed network information
    infrastructure (U-NII) devices in various frequency bands.[^46] In
    addition, these rules require systems using directional antennas
    with a gain greater than 6 dBi required to reduce both the maximum
    transmit power and the maximum power density. We have found those
    criteria to be effective, and seek comment on adopting similar
    technical requirements for unlicensed operations under our
    interference temperature rules in the 6525-6700 MHz and 12.75-13.25
    GHz bands. In this regard, we again note that our initial analysis
    indicates that a reasonable interference temperature limit in this
    band might support unlicensed operations with maximum transmit
    powers possibly in the range of 24 dBm to 30 dBm and EIRPs in the
    range of 30 dBm to 36 dBm. We seek comment on the merit of this
    tentative conclusion. We also encourage commenters to suggest
    specific alternative technical limits and to include detailed
    supporting analysis. Such analysis should minimally include thorough
    link budget analyses along with discussions of the advantages and
    disadvantages of various options and alternatives.

48. We request comments on whether any portion of the bands discussed
    above that are allocated for fixed operation should be excluded from
    consideration under this proposal and why. For example, is it
    necessary to preclude unlicensed operation in the 6650-6675.2 MHz
    portion of this band to protect radio astronomy operations or can
    suitable technical standards be developed to ensure that harmful
    interference is not caused? Is it necessary to preclude unlicensed
    operation in the 13.15-13.2125 GHz band to protect mobile operations
    or are the proposed standards sufficient to ensure that mobile
    systems will not receive harmful interference from unlicensed
    operations?

49. *Out-of-band Emissions*. We recognize the need to assure that
    increased operation of unlicensed devices enabled under the
    interference temperature concept in these bands will not result in
    harmful out-of-band interference. To that end, we propose that such
    operations should comply with an undesirable emission limit such as
    that set forth in Section 15.407(b)(1) of the Rules. This rule
    requires that all out-of-band emissions from U-NII devices operating
    in the 5.15-5.25 GHz band not exceed an EIRP of -27 dBm/MHz. Our
    experience to date has shown that this limit has served well in the
    context of its current application to U-NII in this band. Based on
    that experience, we seek comment on whether a similar requirement
    will be beneficial when applied to the out-of-band emissions of
    unlicensed operations in the 6525-6700 MHz and 12.75-13.25 GHz
    bands. We request comment on whether the nature and value of the
    emission limit we propose herein would be appropriate. Commenters
    should discuss whether other out-of-band emission limits should be
    considered as well and whether additional limits should be specified
    immediately outside of the operating channel. For example,
    commenters might wish to address whether another single value limit,
    or alternatively, multiple value limits graduated by frequency
    offset would be more appropriate.

50. *Satellite Monitoring of Spectrum Occupancy.* The Inquiry describes
    a number of approaches to adaptive or real-time interference
    temperature measurement by which monitored information regarding
    spectrum occupancy could be transmitted back to individual devices.
    As an additional example, it could be possible for satellites to
    monitor and make available real-time measured data such as ΔT/T,
    I/N, C/I, C/(I+N) and I that could then be used by individual
    devices to adjust their operation to ensure that they do not
    interfere with other licensed operations. This capability would
    appear to be feasible since satellites are already being used for
    real-time, remote monitoring of geophysical, meteorological and
    environmental conditions on the surface of the earth.

51. We request comment on the utility and potential benefits of such a
    real-time monitoring approach in the two bands discussed above, as
    well as in any other bands where the interference temperature
    concept could be applied. We request comment on how the monitored
    information could be acquired by unlicensed devices. For example,
    the information might be provided via broadcast signals (possibly
    through a subscription service) or other means. One possibility
    could be that unlicensed equipment operating in this manner would
    consist of systems controlled by centralized transmitting stations
    that relay this information. More generally, commenters should
    indicate whether they believe there is interest in such a system and
    specify how they envision such a system might work. We also request
    comment on the state of current technology and whether such a system
    is technically feasible today. If such a system were to exist, what
    data should be provided to unlicensed devices? Who should operate
    such a system?

# PROCEDURAL MATTERS

52. As required by the Regulatory Flexibility Act, see 5 U.S.C. § 603,
    the Commission has prepared an Initial Regulatory Flexibility
    Analysis (IRFA) of the possible significant economic impact on small
    entities of the proposals suggested in this document. The IRFA is
    set forth in Appendix A. Written public comments are requested on
    the IRFA. These comments must be filed in accordance with the same
    filing deadlines as comments filed in this Notice of Proposed Rule
    Making ("Notice"). Comments must have a separate and distinct
    heading designating them as responses to the IRFA.

53. This is a permit-but-disclose notice and comment rule making
    proceeding. *Ex parte* presentations are permitted, except during
    the Sunshine Agenda period. *See generally* 47 C.F.R. §§ 1.1200(a),
    1.1203, and 1.1204(b).

54. Pursuant to Sections 1.415 or 1.419 of the Commission\'s rules, 47
    C.F.R. §§ 1.415, 1.419, interested parties may file comments on
    before **75 days after publication in the Federal Register**, and
    reply comments on or before **105 days after publication in the
    Federal Register**. Comments may be filed using the Commission\'s
    Electronic Comment Filing System (ECFS) or by filing paper copies.
    *See Electronic Filing of Documents in Rulemaking Proceedings*, 63
    Fed. Reg. 24,121 (1998).

55. Comments filed through the ECFS can be sent as an electronic file
    via the Internet at \<http://www.fcc.gov/e-file/ecfs.html\>.
    Generally, only one copy of an electronic submission must be filed.
    If multiple docket or rulemaking numbers appear in the caption of
    this proceeding, however, commenters must transmit one electronic
    copy of the comments to each docket or rulemaking number referenced
    in the caption. In completing the transmittal screen, commenters
    should include their full name, Postal Service mailing address, and
    the applicable docket or rulemaking number. Parties may also submit
    an electronic comment by Internet e-mail. To get filing instructions
    for e-mail comments, commenters should send an e-mail to
    ecfs@fcc.gov, and should include the following words in the body of
    the message, \"get form \<your e-mail address\>.\" A sample form and
    directions will be sent in reply.

56. Parties who choose to file by paper must file an original and four
    copies of each filing. If more than one docket or rulemaking number
    appears in the caption of this proceeding, commenters must submit
    two additional copies for each additional docket or rulemaking
    number. All filings must be sent to the Commission\'s Secretary,
    Marlene H. Dortch, Office of the Secretary, Federal Communications
    Commission, The Portals, 445 Twelfth Street, S.W., Washington, D.C.
    20554.

57. Filings can be sent by hand or messenger delivery, by commercial
    overnight courier, or by first-class or overnight U.S. Postal
    Service mail (although we continue to experience delays in receiving
    U.S. Postal Service mail). The Commission\'s contractor, Natek,
    Inc., will receive hand-delivered or messenger-delivered paper
    filings for the Commission\'s Secretary at 236 Massachusetts Avenue,
    N.E., Suite 110, Washington, D.C. 20002. The filing hours at this
    location are 8:00 a.m. to 7:00 p.m. All hand deliveries must be held
    together with rubber bands or fasteners. Any envelopes 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 mail, Express Mail, and Priority Mail
    should be addressed to 445 12th Street, S.W., Washington,
    D.C. 20554. All filings must be addressed to the Commission\'s
    Secretary, Marlene H. Dortch, Office of the Secretary, Federal
    Communications Commission.

58. Parties who choose to file by paper should also submit their
    comments on diskette. Such a submission should be on a 3.5-inch
    diskette formatted in an IBM compatible format using Microsoft Word
    or compatible software. The diskette should be accompanied by a
    cover letter and should be submitted in "read only" mode. The
    diskette should be clearly labeled with the commenter's name,
    proceeding (including the lead docket number, type of pleading
    (comment or reply comment), date of submission, and the name of the
    electronic file on the diskette. The label should also include the
    following phrase \"Disk Copy -- Not an Original.\" Each diskette
    should contain only party's pleading, preferably in a single
    electronic file. In addition, commenters must send diskette copies
    to the Commission's copy contractor, Qualex International, Portals
    II, 445 12th Street, SW, Room CY-B402, Washington, DC, 20554.

59. Alternative formats (computer diskette, large print, audio cassette
    and Braille) are available to persons with disabilities by
    contacting Brian Millin at (202) 418-7426, TTY (202) 418-2555, or
    via e-mail to Brian.Millin@fcc.gov. This *Notice* can also be
    downloaded at <http://www.fcc.gov/oet>.

60. The proposed action is authorized under Sections 4(i), 301, 302,
    303(e), 303(f), 303(r) and 307 of the Communications Act of 1934, as
    amended, 47 U.S.C. Sections 154(i), 301, 302, 303(e), 303(f), 303(r)
    and 307.

61. The Commission's Consumer and Governmental Affairs Bureau, Reference
    Information Center, SHALL SEND a copy of this Notice, including the
    IRFA, to the Chief Counsel for Advocacy of the Small Business
    Administration.

62. For further information regarding this Notice of Inquiry and Notice
    of Proposed Rulemaking, contact Gary Thayer, Office of Engineering
    and Technology, (202) 418-2290, e-mail <gary.thayer@fcc.gov>, or
    John Reed, Office of Engineering and Technology, (202) 418-2455,
    e-mail <john.reed@fcc.gov>, or Ahmed Lahjouji, Office of Engineering
    and Technology, (202) 418-2061 e-mail ahmed.lahjouji@fcc.gov.

> FEDERAL COMMUNICATIONS COMMISSION
>
> Marlene H. Dortch
>
> Secretary

**Appendix A**

**Initial Regulatory Flexibility Analysis**

As required by the Regulatory Flexibility Act,[^47] the Commission has
prepared this Initial Regulatory Flexibility Analysis (IRFA) of the
possible significant economic impact on small entities by the policies
and rules proposed in this Notice of Proposed Rule Making
*("*Notice*")*. Written public comments are requested on the IRFA.
Comments must be identified as responses to the IRFA and must be filed
by the deadlines for comments on the Notice provided in paragraph 54 of
this item. The Commission shall send a copy of this Notice, including
the IRFA, to the Chief Counsel for Advocacy of the Small Business
Administration. In addition, the Notice and the IRFA (or summaries
thereof) will be published in the Federal Register.[^48]

**A. Need for, and Objectives of, the Proposed Rules.**

This rulemaking proposal is initiated to obtain comments regarding
proposed changes to the regulations for radio frequency devices that do
not require a license to operate. The Commission seeks to determine if
its standards should be amended to permit the expanded operation of
unlicensed devices in the 6525-6700 MHz and 12.75-13.25 GHz bands. We
believe that it may be necessary to shift our current paradigm for
assessing interference from approaches based primarily on transmitter
operations towards new approaches that focus on the actual RF
environment and interaction between transmitters and receivers, such as
the interference temperature metric. In order to begin our exploration
of the process that would be involved in a transition to an interference
temperature regime, we seek comment on specific technical guidelines in
the NPRM portion of our discussion that we believe can be implemented in
the near future for selected frequency bands prior to any general
implementation of interference temperature limits and real-time
adaptation of transmitters to the interference temperature environment.

**B. Legal Basis.**

The proposed action is taken pursuant to Sections 4(i), 301, 302,
303(e), 303(f), 303(r), and 307 of the Communications Act of 1934, as
amended, 47 U.S.C. Sections 154(i), 301, 302, 303(e), 303(f), 303(r),
and 307.

**C. Description and Estimate of the Number of Small Entities to Which
the Proposed Rules Will Apply.**

The RFA directs agencies to provide a description of, and where
feasible, an estimate of the number of small entities that may be
affected by the proposed rules, if adopted.[^49] The RFA generally
defines the term "small entity" as having the same meaning as the terms
"small business," "small organization," and "small governmental
jurisdiction."[^50] In addition, the term "small business" has the same
meaning as the term "small business concern" under the Small Business
Act.[^51] A "small business concern" is one which: (1) is independently
owned and operated; (2) is not dominant in its field of operation; and
(3) satisfies any additional criteria established by the Small Business
Administration (SBA).[^52] Nationwide, there are approximately 22.4
million small businesses, total, according to the SBA data.[^53]

A small organization is generally "any not-for-profit enterprise which
is independently owned and operated and is not dominant in its
field."[^54] Nationwide, as of 1992, there were approximately 275,801
small organizations.[^55] The term "small governmental jurisdiction" is
defined as "governments of cities, towns, townships, villages, school
districts, or special districts, with a population of less than fifty
thousand."[^56] As of 1997, there were about 87,453 governmental
jurisdictions in the United States.[^57] This number includes 39,044
county governments, municipalities, and townships, of which 37,546
(approximately 96.2%) have populations of fewer than 50,000, and of
which 1,498 have populations of 50,000 or more. Thus, we estimate the
number of small governmental jurisdictions overall to be 84,098 or
fewer.

The SBA has developed a small business size standard for wireless firms
within the two broad economic census categories of Paging[^58] and
Cellular and Other Wireless Telecommunications. [^59] Under both SBA
categories, a wireless business is small if it has 1,500 or fewer
employees. For the census category of Paging, Census Bureau data for
1997 show that there were 1320 firms in this category, total, that
operated for the entire year.[^60] Of this total, 1303 firms had
employment of 999 or fewer employees, and an additional 17 firms had
employment of 1,000 employees or more.[^61] Thus, under this category
and associated small business size standard, the majority of firms can
be considered small. For the census category Cellular and Other Wireless
Telecommunications firms, Census Bureau data for 1997 show that there
were 977 firms in this category, total, that operated for the entire
year.[^62] Of this total, 965 firms had employment of 999 or fewer
employees, and an additional 12 firms had employment of 1,000 employees
or more.[^63] Thus, under this second category and size standard, the
majority of firms can, again, be considered small.

The SBA has established a small business size standard for Radio and
Television Broadcasting and Wireless Communications Equipment
Manufacturin*g*. Under this standard, firms are considered small if they
750 or fewer employees.[^64] Census Bureau data for 1997 indicate that,
for that year, there were a total of 1,215 establishments in this
category.[^65] Of those, there were 1,150 that had employment under 500,
and an additional 37 that had employment of 500 to 999. Thus, under this
size standard, the majority of establishments can be considered small.

*Satellite Telecommunications* The SBA has developed a small business
size standard for Satellite Telecommunications Carriers, which consists
of all such companies having \$12.5 million or less in annual
receipts.[^66] In addition, a second SBA size standard for Other
Telecommunications includes "facilities operationally connected with one
or more terrestrial communications systems and capable of transmitting
telecommunications to or receiving telecommunications from satellite
systems," [^67] and also has a size standard of annual receipts of
\$12.5 million or less. According to Census Bureau data for 1997, there
were 324 firms in the category Satellite Telecommunications, total, that
operated for the entire year.[^68] Of this total, 273 firms had annual
receipts of \$5 million to \$9,999,999 and an additional 24 firms had
annual receipts of \$10 million to \$24,999,990.[^69] Thus, under this
size standard, the majority of firms can be considered small. In
addition, according to Census Bureau data for 1997, there were 439 firms
in the category Satellite Telecommunications, total, that operated for
the entire year.[^70] Of this total, 424 firms had annual receipts of
\$5 million to \$9,999,999 and an additional 6 firms had annual receipts
of \$10 million to \$24,999,990.[^71] Thus, under this second size
standard, the majority of firms can be considered small.

As no party currently is permitted to market or operate equipment under
the proposed standards, there will be no immediate impact on any small
entities. The Commission does not have an estimated number for the small
entities that may currently be capable of producing such products but
believes that there are only a few in existence.

**D. Description of Projected Reporting, Recordkeeping and Other
Compliance Requirements for Small Entities.**

Part 15 transmitters are already required to be authorized under the
Commission\'s certification procedure as a prerequisite to marketing and
importation. The reporting and recordkeeping requirements associated
with these equipment authorizations would not be changed by the
proposals contained in this *Notice*. These changes to the regulations
would permit the introduction of an entirely new category of radio
transmitters.

**E. Steps Taken to Minimize the Significant Economic Impact on Small
Entities, and Significant Alternatives Considered.**

The RFA requires an agency to describe any significant, specifically
small business, alternatives that it has considered in reaching its
proposed approach, which may include the following four alternatives
(among others): "(1) the establishment of differing compliance or
reporting requirements or timetables that take into account the
resources available to small entities; (2) the clarification,
consolidation, or simplification of compliance and reporting
requirements under the rule for such small entities; (3) the use of
performance rather than design standards; and (4) an exemption from
coverage of the rule, or any part thereof, for such small
entities."[^72]

As noted, in order to begin our exploration of the process that would be
involved in a transition to an interference temperature regime, we seek
comment on specific technical guidelines in the NPRM portion of our
discussion that we believe can be implemented in the near future for
selected frequency bands prior to any general implementation of
interference temperature limits and real-time adaptation of transmitters
to the interference temperature environment. Currently, no party is
permitted to market or operate equipment under the proposed standards,
so there will be no immediate impact on any small entities. One
alternative to our proposal is reflected in our request for comments on
whether it is necessary to preclude expanded unlicensed operation in the
650-6675.2 MHz band to protect radio astronomy operations or whether
suitable technical standards can be developed to ensure that
interference is not caused. We invite small entities to comment on this
alternative.

**F. Federal Rules that May Duplicate, Overlap, or Conflict with the
Proposed Rule.**

None.

**Appendix B**

**Satellite Link Budget Analyses**

This appendix illustrates sample link budget analyses that suggest the
approximate potential number of unlicensed devices that could be
permitted to operate simultaneously within CONUS without causing harmful
interference to the incumbent satellite systems.

We made the following assumptions for the purpose of simplification in
order to roughly characterize hypothetical unlicensed operations in the
band.

-   10% duty cycle for mobile unlicensed devices, *i.e.,*
    Wireless-LAN-based devices with a 30 dBm (1 W) maximum EIRP;

-   100% duty cycle for fixed systems with up to a 36 dBm (4 W) maximum
    EIRP;

-   Equal number of devices operating indoors and outdoors;

-   10 dB signal attenuation to account for indoor signal loss;[^73]

-   Omnidirectional antenna for mobile devices, *i.e.*, attenuation in
    the direction of the satellite is, on average, 6 dB lower than the
    main signal;

-   Directional antennas for fixed devices that provide, on average,
    attenuation of 22 dB relative to the main lobe in the direction of
    the satellite;[^74] at angles ranging between 30 and 100‑degrees
    off-axis from the transmission centerline; and

-   Satellite interference threshold criterion, ΔT/T, of 5%.[^75]

> The spectral power distribution of unlicensed emission levels was
> hypothesized according to Table 1.
>
> **Table 1. Unlicensed devices Power distribution**

+--------------------+-----+-------+-------+-------+-------+-------+
|                    | **  |       |       |       | **    |       |
|                    | Mob |       |       |       | Fixed |       |
|                    | ile |       |       |       | Devi  |       |
|                    | Dev |       |       |       | ces** |       |
|                    | ice |       |       |       |       |       |
|                    | s** |       |       |       | **100 |       |
|                    |     |       |       |       | %     |       |
|                    | **  |       |       |       | Duty  |       |
|                    | 10% |       |       |       | Cy    |       |
|                    | D   |       |       |       | cle** |       |
|                    | uty |       |       |       |       |       |
|                    | C   |       |       |       |       |       |
|                    | ycl |       |       |       |       |       |
|                    | e** |       |       |       |       |       |
+--------------------+-----+-------+-------+-------+-------+-------+
| **EIRP (mw)**      | 50  | 100   | 200   | 1000  | 2000  | 4000  |
+--------------------+-----+-------+-------+-------+-------+-------+
| **Device           | 30  | 35    | 20    | 5     | 5     | 5     |
| Distribution %**   |     |       |       |       |       |       |
+--------------------+-----+-------+-------+-------+-------+-------+
| **% simultaneous   | 3.0 | 3.5   | 2.0   | 0.5   | 5     | 5     |
| transmissions at   |     |       |       |       |       |       |
| specified EIRP**   |     |       |       |       |       |       |
+--------------------+-----+-------+-------+-------+-------+-------+

The following sample link budget analyses are based on the assumptions
above.

  -------------- ---------------------------------------- ----------- ---------------- -----------------
                 **Item**                                 **Units**   **Ext. C**       **Ext. Ku**

                                                                                       

  Uplink                                                  GHz         6.613            13
  Frequency Band                                                                       

                 Lower Band limits                        MHz         6525             12750

                 Upper Band limits                        MHz         6700             13250

                 Wavelength                               m           0.05             0.02

                 Effective Area Isotrope                  dBm\^2      -37.9            -43.7

                                                                                       

  FSS System                                                                           
  Parameters                                                                           

                 Percent of CONUS in one beam             \%          75               100

                 FSS Satellite Uplink Antenna Gain        dBi         32.3             31.1

                 Typical Satellite Receive Temperature    K           500              625

                 FSS Satellite Transmission Gain          dB          -5.0             5.0

                 Typical Earth Station Receive            K           90.0             100.0
                 Temperature                                                           

                 Equivalent Satellite Link Noise          K           248              2076
                 Temperature                                                           

                                                                                       

  Allowable Part                                          \%          5.0              5.0
  15 Device                                                                            
  (Delta T/T)                                                                          

                                                                                       

  Satellite                                                                            
  System                                                                               
  Parameters                                                                           

                 Allowable Increase in Eq. Sat. Link      K           12.41            103.82
                 Noise Temp                                                            

                 FSS Satellite Transmission Gain          dB          -5.0             5.0

                 Allowable Increase in Sat. Noise Temp    K           39.2             32.8

                 Boltzman Constant                        dBW/Hz K    -228.6           -228.6

                 Allowable Interference Pwr @ Output of   dBW/Hz      -212.7           -213.4
                 Sat. Ant.                                                             

                 FSS Satellite Uplink Antenna Gain        dBi         32.3             31.1

                 Nominal Free Space Loss                  dB          -200..3          -206.1

                 Allowable Interference at Earth Surface  dBW/Hz      -44.7            -38.4

                                                                                       

  Interference                                                                         
  Temperature                                                                          
  System                                                                               
  Parameters                                                                           

                 Transmit EIRPs from Aggregate            dBW         -24.08           -24.08
                 Interfering Devices                                                   

                 Assumed Transmit Bandwidth               kHz         20000            20000

                 Part 15 Gain toward Sat                  dBi         0.0              0.0

                 Part 15 Power density toward Sat         dBW/Hz      -97.1            -97.1

                                                                                       

                 Allowable Interference at Earth Surface  dBW/Hz      -44.7            -38.4

                 Part 15 Power density toward Sat         dBW/Hz      -97.1            -97.1

                 Allowable Emitters per Beam in RLAN BW   dB          52.3             58.7

                 Allowable Emitters per Beam in RLAN BW   \#          171544           739832

                                                                                       

  Allowable                                                                            
  Emitters                                                                             

                 Allowable number of emitters/satellite   \#          171544           739832
                 beam                                                                  

                 Available Bandwidth per satellite beam   MHz         175              500

                 Part 15 Reuse Bandwidths in FSS Band     MHz         11.67            25.00

                 Alternate Polarizations                  \#          2                2

  **Total number                                                      **53,369,095**   **369,916,129**
  of unlicensed                                                                        
  systems within                                                                       
  CONUS**                                                                              
  -------------- ---------------------------------------- ----------- ---------------- -----------------

**SEPARATE STATEMENT OF**

**CHAIRMAN MICHAEL K. POWELL**

*Re: Establishment of Interference Temperature Metric to Quantify and
Manage Interference and to Expand Available Unlicensed Operation in the
Fixed, Mobile and Satellite Frequency Bands;*

> *ET Docket No. 03-237.*

The introduction of a new "interference temperature" model has the
potential to tremendously improve radio spectrum management. Rather than
assess interference based solely on transmitter operations, the
interference temperature model introduced in the Commission's Spectrum
Policy Task Force Report takes into account the cumulative effects of
all undesired radio frequency energy. The marketplace demands for
spectrum require that we explore new ways to use this resource more
efficiently.

The Notice of Inquiry seeks comment on various technological factors and
the process for managing the transition to a new interference
temperature paradigm. The Notice of Proposed Rulemaking seeks comments
on technical rules that would establish proper limits and procedures for
assessing interference temperature. Moreover, the NPRM proposes to begin
experimenting with the interference temperature approach on a limited
basis in select frequency bands and recommends imposing restrictions on
unlicensed devices that would include limiting the transmitter output
power and requirements to use transmit power control (TPC) and dynamic
frequency selection (DFS).

I fully support consideration of this new approach to interference
control and spectrum management. It promises to promote more efficient
use of spectrum and encourage new and innovative uses of this important
resource for the benefit of the American public.

SEPARATE STATEMENT OF

COMMISSIONER MICHAEL J. COPPS

*Re: Establishment of an Interference Temperature Metric to Quantify and
Manage Interference to Expand Available Unlicensed operation in Certain
Fixed, Mobile and Satellite Frequency Bands;*

*ET Docket No. 03-237.*

I'm excited to see the beginning of the examination of whether we can
put the spectrum temperature concept into practice. As I've said before,
I think that the idea has great promise, if we use it as a tool to
increase the efficiency with which spectrum resources are put to use, as
is our statutory responsibility.

I hope that commenters will use the NOI to address an issue that is of
particular concern to me. While the interference temperature metric may
be a good new way to measure interference, we do not have an adequate
way to determine what the right interference temperature is for a given
band. The only tools we have for this job are the ill-fitting and
ill-defined "interference" and "harmful interference" concepts. The
inappropriateness and inadequacy of these concepts for the job of
prospectively setting interference temperature will make this new metric
very hard to use predictably and non-arbitrarily in the real world.

So I think that the Commission must work to improve the standard we use
to determine permissible levels of interference, whether using the
interference temperature metric or some other metric. And I believe that
an important side benefit of the added predictability that a better
standard would bring is that incumbent spectrum users would be more
comfortable with the interference temperature metric. This NOI is the
perfect vehicle to start the process.

**SEPARATE STATEMENT OF**

**COMMISSIONER JONATHAN S. ADELSTEIN**

**APPROVING IN PART, CONCURRING IN PART**

*Re: In re Establishment of an Interference Temperature Metric to
Quantify and Manage Interference and to Expand Available Unlicensed
operation in the Fixed, Mobile and Satellite Frequency Bands; ET Docket
No. 03-237*

I commend the Spectrum Policy Task Force and its members for their 2002
report and for bringing to the Commission's attention a new interference
temperature approach to spectrum management. The Task Force noted that
the "increasing demand for spectrum-based services and devices are
straining longstanding, and outmoded, spectrum policies." I could not
agree more. The reality is that we cannot produce more spectrum. We need
to foster a framework for innovation that enables new technologies to
come forward to meet demand more efficiently -- in both the private and
public sectors.

Most significantly, the Task Force report offered specific findings and
recommendations that have been very useful in stimulating debate in the
area of spectrum management. The concept of interference temperature is
a particularly significant recommendation, and I very much look forward
to a full and vigorous discussion on this challenging issue. I recognize
that this is one of the more controversial proposals to come out of the
report, but believe that it is entirely appropriate for the Commission
to seek comment on new approaches to spectrum management. Whatever the
outcome, the deliberation process makes us a better, more informed
agency, and I encourage all interested parties to file comments in this
proceeding.

I have previously noted my belief that the Commission should strive to
push the boundaries to accommodate new technologies provided that they
do not cause harmful interference. Indeed, a little noticed provision of
the Communications Act, Section 157, reads that "It shall be the policy
of the United States to encourage the provision of new technologies and
services to the public." If an interference temperature model for
quantifying and managing interference can be developed so that it truly
prevents real harmful interference and allows for the provision of new
technologies and services, then we should encourage its development. I
do not know if we are there yet, but I very much look forward to the
debate.

Finally, while I support the discussion in the item considering the
application of the interference temperature approach to unlicensed
operations in the 6525-6700 MHz and 12.75-13.25 GHz bands, I do not
believe that this portion of the item should be styled as a Notice of
Proposed Rule Making, as opposed to remaining part of the Notice of
Inquiry. I think it is very clear that we are exploring an entirely new
concept in the interference temperature model, and it is quite premature
to actually discuss proposed rules when the Commission has not even
engaged in a preliminary discussion on the interference temperature
approach as a whole.

I am not sure what the rush is and am not convinced that moving this
discussion to the NOI portion of the item somehow holds back our
consideration of the interference temperature approach. I think the
licensees in these bands deserve better. For this reason, I can only
concur to the NPRM portion of this item.

[^1]: *See* *Spectrum Policy Task Force Report* (*Task Force Report*),
    ET Docket No. 02-135, November 15, 2002, at p. 1. On November 25,
    2002, the Commission issued a public notice FCC 02-322, inviting
    public comment on the Task Force report. Twenty-eight parties filed
    comments specifically addressing the issue of the interference
    temperature concept.

[^2]: *Id*. at 25-27.

[^3]: The Task Force's other principal recommendation for improving
    interference management was for the Commission to incorporate
    receiver interference immunity performance into its spectrum
    policies. *Task Force Report*, at 31. Pursuant to that
    recommendation, the Commission recently adopted a *Notice of
    Inquiry* (*Inquiry*) in a related proceeding to begin consideration
    of incorporation of receiver interference performance specifications
    into its spectrum policy on a broader basis. *See Notice of Inquiry*
    in ET Docket No. 03-65, adopted March 13, 2003, FCC 03-54 (released
    March 24, 2003). In that *Inquiry*, the Commission observed that if
    the receivers used with a radio service are designed to provide a
    certain degree of immunity to, or tolerance of, undesired RF energy
    and signals, more efficient and predictable use of the spectrum can
    be achieved, as well as greater opportunities for access to the
    spectrum. It asked for comment, information and research on a wide
    range of issues concerning the interference immunity performance
    capabilities of existing receivers, possibilities for improving the
    level of receiver interference immunity in the various radio
    services, possible approaches by which desired levels of performance
    could be achieved, and the potential positive and negative impacts
    of receiver standards on innovation and the marketplace.

[^4]: *See* National Association for Amateur Radio (ARRL) comments at 8,
    Agilent Technologies, Inc. comments at 7, HYPRES, Inc. comments at
    3-4, Motorola comments at 14, and Wireless Communications
    Association International, Inc. comments at 10-12.

[^5]: *See* Agere comments at 6, AT&T comments at 12-14, Cingular
    comments at 18-19, and Verizon Wireless comments at 10-12.

[^6]: *See* Report of the Second Meeting of the FCC Technological
    Advisory Council III held on July 7, 2003 at
    http://www.fcc.gov/oet/tac/.

[^7]: *Task Force Report* at 11-15.

[^8]: *Id* at 27.

[^9]: *Id.* at 31.

[^10]: *See* *Interference Immunity Performance Specifications for Radio
    Receivers*, ET Docket No. 03-65, 18 FCC Rcd 6039 (2003).

[^11]: As recommended by the Task Force at 27.

[^12]: *Task Force Report* at 15.

[^13]: *Id*. Parties have expressed a desire for flexibility and for
    certainty regarding operating environment. See Report of the
    Spectrum Rights and Responsibilities Working Group, Spectrum Policy
    Task Force at 27.

[^14]: The concept of an interference temperature as a measure of the
    undesired RF power in a particular band and location is essentially
    the same as the concept of an "antenna temperature" as described by
    Wolfram Research. *See*, for example, Wolfram Research at
    <http://scienceworld.wolfram.com/physics/AntennaTemperature.html>.
    Under this concept, antenna temperature is a component of the total
    noise temperature of a receiver system, which also includes the
    thermal noise generated within the receiver.

[^15]: Interference temperature, expressed in units of Kelvin, can be
    calculated as the power received by an antenna in watts divided by
    the associated RF bandwidth in Hertz and a term known as "Boltzman's
    constant" (the value of this constant is 1.38 x 10^-23^ watt-sec/K,
    also note that 1 K = - 272.15° Celsius). Alternatively, interference
    temperature can be calculated as the power flux density (e.g.,
    microWatts/m^2^ over a bandwidth) multiplied by the antenna capture
    area in meters squared divided by both the associated RF bandwidth
    in Hertz and Boltzman's constant. An "interference temperature
    density" can also be defined as the interference temperature per
    unit area, expressed in units of Kelvin per meter squared, and
    calculated as the interference temperature divided by the effective
    capture area (aperture) of the receiving antenna. This quantity
    could be measured for particular frequencies using a reference
    antenna and, thereafter, would be independent of receiving antenna
    characteristics.

[^16]: This figure is taken form the *Task Force Report*. *See* *Task
    Force Report*, Figures 2 and 3.

[^17]: Note that unlicensed devices can operate successfully across a
    frequency band occupied by a higher level signal only if the
    bandwidth occupied by such devices is greater than that of the
    higher level signal (which is reasonable to assume in the case of
    direct sequence digital spread spectrum systems and digital
    transmission systems that have similar spectrum occupancy
    characteristics).

[^18]: More specifically, stations would be able to provide service at
    locations where their signal would exceed cumulative levels of
    interfering signals and noise by some margin above which their
    receivers need to operate. Such operating margins over
    noise/interference levels are common in radio services, and for this
    reason most stations would not actually be able to provide service
    out to a range where the level of their signal equals the level of
    noise plus interference. Conceptually, the required margin could be
    included in the formulation of the interference temperature limit
    for a given service and/or frequency band.

[^19]: *See, e.g., Task Force Report* at 3.

[^20]: This value does not include the noise generated by the receiver
    itself. The level of noise produced by the receiver is not a
    significant contribution to the noise floor if the level of noise
    produced by external sources combined with the level of interfering
    signals is at least 6 to 10 dB greater than the level of the noise
    produced by the receiver.

[^21]: Atmospheric noise is generally produced by weather phenomena and
    is most common on frequencies below 30 MHz. This type of noise is
    usually sporadic in nature, varying with the season, weather
    conditions, and time of day. The major source of atmospheric noise
    is lightning. Galactic noise is produced by solar, cosmic and other
    extraterrestrial phenomena and generally exceeds atmospheric noise
    in the VHF spectrum and above. In recent years, man-made noise from
    both incidental and unintentional radiators can exceed both
    atmospheric and galactic noise at all frequencies.

    An incidental radiator is a device that generates RF energy in the
    course of its operation although the device is not intentionally
    designed to generate or emit such energy. Examples of incidental
    radiators include DC motors, automobile ignitions, mechanical light
    switches, fluorescent lights, and electric power transmission lines,
    *see* 47 C.F.R. 15.3(n). An unintentional radiator is a device that
    intentionally generates RF energy for use within the device, or that
    sends radio frequency signals by conduction to associated equipment,
    but which is not intended to emit RF energy by radiation or
    induction. Examples of unintentional radiators include computers,
    radio receivers, and other electronic equipment. *See* 47 C.F.R. §
    15.3(z).

[^22]: *See* 47 C.F.R. § 2.1 (c).

[^23]: *See* ¶ 10, *supra.*

[^24]: The trigger for coordination with co-primary satellite services
    used by the ITU is 6% ∆T/T.

[^25]: DFS is a feature that dynamically instructs the transmitter to
    switch to another channel whenever a particular switching threshold
    condition (such as, for example, the prevailing ambient interference
    level - or any other specified criterion) is met.

[^26]: We are not proposing to permit unlicensed operation in the
    13.15-13.2125 GHz band at this time as that band is allocated
    predominantly for BAS/CARS mobile operations.

[^27]: *See* 47 C.F.R. § 2.106, note 5.149

[^28]: *See* 47 C.F.R. § 2.106.

[^29]: *See* 47 C.F.R. § 2.106, note US251. The footnote states that the
    band is allocated to the Federal and non-Federal Government space
    research (deep space and space-to-Earth) service for reception only
    at Goldstone, CA.

[^30]: FSS systems in geosynchronous orbit (GSO) in this band are
    limited to international systems. *See* 47 C.F.R. § 2.106, note
    NG104. Non-GSO FSS systems in this band are limited to gateway
    stations. See 47 C.F.R. § 25.202. A gateway earth station is an
    earth station complex consisting of multiple interconnecting earth
    station antennas supporting the communication routing and switching
    functions of a non-geostationary satellite orbit fixed-satellite
    service (NGSO FSS) system as a whole. See 47 C.F.R. § 25.201.

[^31]: *See*, *e.g*., 47 C.F.R. § 74.636. Typically, BAS and CARS
    stations operate with EIRPs 10 to 15 dB below the maximum
    permissible limits.

[^32]: *See* 47 C.F.R. § 25.204(a). Earth stations must limit emissions
    to 70 dBm in any 4 kHz band for θ = 0^o^ and to 70+3θ dBm in any 4
    kHz band for 0^o^ \< θ ≤ 5^o^; where θ is the angle of elevation of
    the horizon viewed from the center of radiation of the antenna of
    the earth station and measured in degrees as positive above the
    horizontal plane and negative below it.

[^33]: *See*, *e.g*., 47 C.F.R. § 74.636.

[^34]: *See* 47 C.F.R. § 15.209. The limit specified for frequencies
    above 960 MHz is 500 uV/m and is measured at 3 meters using a 1 MHz
    resolution bandwidth. This is equivalent to an EIRP of -41.25
    dBm/MHz. It also is possible to operate intermittent unlicensed
    systems at slightly higher power levels under 47 C.F.R. § 15.231,
    which allows periodic use above 70 MHz. The 126.25 dB difference
    expressed above does not take into account different FS bandwidth
    characteristics which could increase or decrease this value.

[^35]: We note, for example, that the sample analysis in Appendix B
    suggests that approximately 53 million unlicensed devices could
    operate in the 6525-6700 MHz band and 370 million unlicensed devices
    could operate in the 12.75-13.25 GHz band.

[^36]: The interference threshold ΔT/T is a measure of the amount of
    interference that can be tolerated by the satellite system. ΔT/T is
    related to the increase in system noise temperature and corresponds
    to the interference-to-noise ratio, I/N.

[^37]: *See* n. 24, *supra*.

[^38]: Goldstone is operated by the Jet Propulsion Laboratory, part of
    Cal Tech., and funded as the NASA deep space research center.

[^39]: Free space attenuation over a line-of-sight path equals 20 log
    \[(4 π D)/λ\] dB where D is the distance in meters and λ is the
    wavelength in meters. The wavelength can be determined by dividing
    the speed of light, 3.00 x 10^8^ meters/second, by the frequency of
    the emission in Hertz. It should be noted that free space
    propagation provides a conservative estimate of the attenuation of
    the emission and that it is likely that the emission levels from an
    unlicensed device would attenuate more rapidly with distance than
    shown by these calculations.

[^40]: *See* 47 C.F.R. §§ 74.641 and 101.115. We used the lower values
    for the purpose of our illustrative analysis herein.

[^41]: The signal level from the unlicensed device that is received by
    the fixed receiver, S~U~, relative to the signal level of the
    desired signal, S~D~, equals the S/I which must exceed 30 to 50 dB,
    *i.e.*, S~D~(dBm) -- S~U~(dBm) = 30 to 50 dB. It is also assumed
    that the received desired signal level is sufficiently above the
    thermal noise floor of the receiver that this noise level may be
    excluded from the calculations. It also should be noted that our
    reference to S/I is independent of fade margins.

[^42]: This result assumes that an unlicensed device receives a signal
    from the fixed station transmitter with approximately the same free
    space path loss as the signal path between the fixed station
    transmitter and receiver. Thus, assuming no variation in other
    propagation variables, the level of received power at the fixed
    receiver would be approximately equal to that measured by the
    unlicensed device with the addition of the gain of the fixed station
    antenna. That is, antenna off-axis attenuation (-32 dB) plus typical
    propagation loss (-89 dB) plus desired S/I (30 to 50 dB) produces an
    unlicensed margin overhead of 91 to 71 dB. We note that this value
    could be useful in determining the sensitivity of the DFS used with
    the unlicensed system and seek comment in that regard.

[^43]: Similarly, an antenna off-axis attenuation (-30 dB) plus typical
    propagation loss (-95 dB) plus desired S/I (30 to 50 dB) produces an
    unlicensed margin overhead of 95 to 75 dB. We note that this value
    could be useful in determining the sensitivity of the DFS used with
    the unlicensed system and seek comment in that regard.

[^44]: The method used to monitor the RF levels and the sensitivity of
    the monitoring system employed would directly impact how an
    unlicensed system would adjust its output frequency. Emission levels
    could be detected by individual unlicensed devices, which would then
    adjust their output frequencies based on the level of the detected
    RF emissions, or they could be detected by centralized control
    stations which would then cause the operating frequencies of their
    satellite stations to be adjusted.

[^45]: Note that the Commission proposed a shorter averaging duration
    for UNII devices.

[^46]: 47 C.F.R. § 15.402. U-NII devices operate on frequencies in the
    5.15-5.825 GHz region of the spectrum.

[^47]: *See* 5 U.S.C. § 603.

[^48]: 5 U.S.C. § 603(a).

[^49]: 5 U.S.C. § 603(b)(3).

[^50]: 5 U.S.C. § 601(6).

[^51]: 5 U.S.C. § 601(3) (incorporating by reference the definition of
    "small-business concern" in the Small Business Act, 15 U.S.C. §
    632). Pursuant to 5 U.S.C. § 601(3), the statutory definition of a
    small business applies "unless an agency, after consultation with
    the Office of Advocacy of the Small Business Administration and
    after opportunity for public comment, establishes one or more
    definitions of such term which are appropriate to the activities of
    the agency and publishes such definition(s) in the Federal
    Register."

[^52]: 5 U.S.C. § 632.

[^53]: *See* SBA, *Programs and Services*, SBA Pamphlet No. CO-0028, at
    pg. 40 (July 2002).

[^54]: 5 U.S.C. § 601(4).

[^55]: U.S. Department of Commerce, Bureau of the Census, 1992 Economic
    Census, Table 6 (special tabulation of data under contract to the
    Office of Advocacy of the U.S. Small Business Administration).

[^56]: 5 U.S.C. 601(5).

[^57]: U.S. Census Bureau, Statistical Abstract of the United States:
    2000, Section 9, pgs. 299-300, Tables 490 and 492.

[^58]: 13 CFR § 121.201, NAICS code 513321 (changed to 517211 in October
    2002).

[^59]: 13 C.F.R. § 121.201, NAICS code 513322 (changed to 517212 in
    October 2002).

[^60]: U.S. Census Bureau, 1997 Economic Census, Subject Series:
    Information, "Employment Size of Firms Subject to Federal Income
    Tax: 1997," Table 5, NAICS code 513321 (issued Oct. 2000).

[^61]: *Id*. The census data do not provide a more precise estimate of
    the number of firms that have employment of 1,500 or fewer
    employees; the largest category provided is "Firms with 1,000
    employees or more."

[^62]: U.S. Census Bureau, 1997 Economic Census, Subject Series:
    Information, "Employment Size of Firms Subject to Federal Income
    Tax: 1997," Table 5, NAICS code 513322 (issued Oct. 2000).

[^63]: *Id*. The census data do not provide a more precise estimate of
    the number of firms that have employment of 1,500 or fewer
    employees; the largest category provided is "Firms with 1,000
    employees or more."

[^64]: 13 C.F.R. § 121.201, NAICS code 334220.

[^65]: U.S. Census Bureau, 1977 Economic Census, Industry Series:
    Manufacturing, "Industry Statistics by Employment Size," Table 4,
    NAICS code 334220 (issued August 1999).

[^66]: 13 C.F. R. § 121.201, North American Industry Classification
    System (NAICS) code 517410 (formerly 513340).

[^67]: *Id*. NAICS code 517910 (formerly 513390).

[^68]: U.S. Census Bureau, 1997 Economic Census, Subject Series:
    Information, "Receipt Size of Firms Subject to Federal Income Tax:
    1997," Table 4, NAICS code 517410 (issued Oct. 2000).

[^69]: *Id*.

[^70]: U.S. Census Bureau, 1997 Economic Census, Subject Series:
    Information, "Receipt Size of Firms Subject to Federal Income Tax:
    1997," Table 4, NAICS code 517910 (issued Oct. 2000).

[^71]: *Id*.

[^72]: 5 U.S.C. § 603(c)(1) -- (c)(4).

[^73]: We recognize that the signal loss due to building attenuation at
    12.75-13.25 GHz should be considerably higher than 10 dB. However,
    we wish to approach this expansion of unlicensed devices
    conservatively.

[^74]: This assumes that, in general, fixed transmitters do not point at
    the geostationary arc and instead point at receivers that are
    relatively close in height. Further, this assumes the use of a class
    B antenna which attenuates signals at angles between 30 and 100
    degrees off-axis from the transmission centerline by at least 32 dB.
    It is likely that emissions at these angles will be in the direction
    of the geostationary arc. We note however that to be conservative in
    our analysis, we assumed an attenuation of only 21 dB.

[^75]: The interference threshold ΔT/T is a measure of the amount of
    interference that can be tolerated by the satellite system. ΔT/T is
    related to the increase in system noise temperature. ΔT/T
    corresponds to the interference-to-noise ratio, I/N (*e.g.*, 10 log
    (ΔT/T = 0.05 (5%)) = -13.01 dB). Coordination is required for a ΔT/T
    greater or equal to 6%. Our conservative analysis is based on a ΔT/T
    threshold equal to 5 %.

    Using the 5% ΔT/Ts interference criterion, the allowable increase in
    the equivalent satellite link noise temperature, due to external
    interference sources, is calculated, for the values of Ts = 248 K (
    or 23.94 dB‑K), and Ts = 2076 K (or 33.17 dB-K), as follows:

    Given a ΔT/Ts= I/N, where Ts: equivalent satellite link noise
    temperature, and ΔT: allowable increase in Ts.

    For the Ext. C band, Ts = 248 K, and ΔT = (ΔT/Ts)\*Ts = 0.05 \* 248
    = 12.41 K or 10.93 dB‑K

    For the Ext. Ku band, Ts = 2076 K, and ΔT = (ΔT/Ts)\*Ts = 0.05 \*
    2076 = 103.82 K or 20.16 dB‑K

    Accordingly, the aggregate interference noise temperature power from
    all unlicensed devices in either of these bands must be 13.01dB
    below the corresponding equivalent satellite link noise temperature.
    Refer to the link budget table for information on how these
    parameters are used to calculate the maximum number of unlicensed
    devices that can operate within CONUS at the acceptable interference
    temperature threshold.