**Before the**

**FEDERAL COMMUNICATIONS COMMISSION**

**Washington, DC 20554**

+-------------------------------------+---+----------------------------+
| In the Matter of                    | ) | ET Docket No. 03-108       |
|                                     |   |                            |
| Facilitating Opportunities for      | ) | ET Docket No. 00-47        |
| Flexible, Efficient,                |   |                            |
|                                     | ) | (Terminated)               |
| And Reliable Spectrum Use Employing |   |                            |
| Cognitive                           | ) |                            |
|                                     |   |                            |
| Radio Technologies                  | ) |                            |
|                                     |   |                            |
| Authorization and Use of Software   | ) |                            |
| Defined                             |   |                            |
|                                     | ) |                            |
| Radios                              |   |                            |
|                                     | ) |                            |
+-------------------------------------+---+----------------------------+

**[COMMENTS OF THE NATIONAL TELECOMMUNICATIONS]{.underline}**

**[AND INFORMATION ADMINISTRATION]{.underline}**

Michael D. Gallagher Kathy D. Smith

Assistant Secretary for Chief Counsel

Communications and Information

Fredrick R. Wentland

Associate Administrator

Office of Spectrum Management

Edward Drocella

Mark Settle

Electronics Engineers

Office of Spectrum Management National Telecommunications and

Information Administration

U.S. Department of Commerce

Room 4713

1401 Constitution Avenue, N.W.

Washington, DC 20230

\(202\) 482-1816

February 15, 2005

**TABLE OF CONTENTS**

**[Section]{.underline}** **[Page]{.underline}**

[EXECUTIVE SUMMARY v](#executive-summary)

[I. INTRODUCTION 2](#introduction)

[II. COGNITIVE RADIO CAPABILITIES CAN BE USED TO RESOLVE SPECTRUM
SCARCITY, DEPLOYMENT, AND TECHNOLOGY TRANSITION PROBLEMS ENCOUNTERED BY
GOVERNMENT AND NON-GOVERNMENT WIRELESS SYSTEMS.
3](#cognitive-radio-capabilities-can-be-used-to-resolve-spectrum-scarcity-deployment-and-technology-transition-problems-encountered-by-government-and-non-government-wireless-systems.)

[III. HIGHER-POWERED UNLICENSED DEVICES EMPLOYING COGNITIVE RADIO
TECHNIQUES SHOULD BE PROHIBITED FROM OPERATING IN THE RESTRICTED
FREQUENCY BANDS LISTED IN SECTION 15.205 OF THE COMMISSION'S RULES.
6](#higher-powered-unlicensed-devices-employing-cognitive-radio-techniques-should-be-prohibited-from-operating-in-the-restricted-frequency-bands-listed-in-section-15.205-of-the-commissions-rules.)

[IV. THE COMMISSION'S PROPOSAL FOR HIGHER-POWERED UNLICENSED DEVICE
OPERATIONS IN THE 5725-5875 MHz BAND IS ADEQUATE TO PROTECT GOVERNMENT
RADAR SYSTEMS IF A MINIMUM TRANSMIT BANDWIDTH IS ESTABLISHED.
9](#the-commissions-proposal-for-higher-powered-unlicensed-device-operations-in-the-5725-5875-mhz-band-is-adequate-to-protect-government-radar-systems-if-a-minimum-transmit-bandwidth-is-established.)

[V. THE REDUCTION OF UNWANTED EMISSIONS FOR HIGHER POWER UNLICENSED
DEVICES SHOULD BE COMMENSURATE WITH THE INCREASED IN-CHANNEL POWER
LEVEL.
13](#the-reduction-of-unwanted-emissions-for-higher-power-unlicensed-devices-should-be-commensurate-with-the-increased-in-channel-power-level.)

[VI. GEO-LOCATION TECHNOLOGIES USED IN CONJUNCTION WITH AN ON-LINE
DATABASE HOLDS PROMISE FOR SHARING BETWEEN UNLICENSED DEVICES AND RADIO
SERVICES USING RECEIVERS AT FIXED LOCATIONS.
15](#geo-location-technologies-used-in-conjunction-with-an-on-line-database-holds-promise-for-sharing-between-unlicensed-devices-and-radio-services-using-receivers-at-fixed-locations.)

[VII. TECHNICAL, COST, AND LEGAL ISSUES, NOT THE COMMISSION'S RULES ARE
LIMITING THE IMPLEMENTATION OF SOFTWARE DEFINED RADIO AS A POTENTIAL
SOLUTION TO THE PUBLIC SAFETY INTEROPERABILITY PROBLEM.
18](#technical-cost-and-legal-issues-not-the-commissions-rules-are-limiting-the-implementation-of-software-defined-radio-as-a-potential-solution-to-the-public-safety-interoperability-problem.)

[VIII. MESH NETWORKS OPERATING AT HIGHER FREQUENCIES WILL REDUCE
INTERFERENCE TO OTHER RADIO SERVICES AND CAN FACILITATE BROADBAND
COMMUNICATIONS.
22](#mesh-networks-operating-at-higher-frequencies-will-reduce-interference-to-other-radio-services-and-can-facilitate-broadband-communications.)

[IX. GEO-ENCRYPTION TECHNIQUES CAN BE USED IN CONJUNCTION WITH EXISTING
ENCRYPTION TECHNIQUES TO PROVIDE PROTECTION OF OVER-THE-AIR SOFTWARE
DOWNLOADS.
24](#geo-encryption-techniques-can-be-used-in-conjunction-with-existing-encryption-techniques-to-provide-protection-of-over-the-air-software-downloads.)

[X. THE INITIAL IMPLEMENTATION OF UNLICENSED COGNITIVE RADIO TECHNOLOGY
SHOULD BE LIMITED TO THE INDUSTRIAL, SCIENTIFIC, AND MEDICAL FREQUENCY
BANDS AND THE FREQUENCY BANDS TRANSFERRED FROM THE FEDERAL GOVERNMENT.
26](#the-initial-implementation-of-unlicensed-cognitive-radio-technology-should-be-limited-to-the-industrial-scientific-and-medical-frequency-bands-and-the-frequency-bands-transferred-from-the-federal-government.)

[XI. SECONDARY SPECTRUM MARKET ACTIVITIES PROMISE TO INCREASE SPECTRUM
EFFICENCY BY FOLLOWING CHANGING DEMAND.
29](#secondary-spectrum-market-activities-promise-to-increase-spectrum-efficency-by-following-changing-demand.)

[XII. HIGH-SPEED DIGITAL-TO-ANALOG CONVERTERS THAT ARE MARKETED AS PART
OF RADIO SYSTEMS SHOULD BE REGULATED AS SOFTWARE DEFINED RADIOS OR
COGNITIVE RADIOS UNDER THE APPROPRIATE SECTION OF THE COMMISSION'S
RULES.
31](#high-speed-digital-to-analog-converters-that-are-marketed-as-part-of-radio-systems-should-be-regulated-as-software-defined-radios-or-cognitive-radios-under-the-appropriate-section-of-the-commissions-rules.)

[XIII. THE COMMISSION SHOULD CONSIDER REQUIRING PROTECTION PROFILES AS
PART OF THE EQUIPMENT CERTIFICATION PROCESS FOR SOFTWARE DEFINED RADIOS.
33](#the-commission-should-consider-requiring-protection-profiles-as-part-of-the-equipment-certification-process-for-software-defined-radios.)

[XIV. THE REQUIREMENT FOR APPLICANTS TO PROVIDE A COPY OF THEIR SOFTWARE
AS PART OF THE CERTIFICATION PROCESS FOR SOFTWARE DEFINED RADIOS SHOULD
BE ELIMINATED.
36](#the-requirement-for-applicants-to-provide-a-copy-of-their-software-as-part-of-the-certification-process-for-software-defined-radios-should-be-eliminated.)

[XV. MANUFACTURERS SHOULD ONLY BE REQUIRED TO DECLARE THEIR DEVICES AS A
SOFTWARE DEFINED RADIO IF THE DEVICE IS REMOTELY PROGRAMMABLE AND HAS
HARDWARE CAPABLE OF TRANSMITTING IN THE RESTRICTED FREQUENCY BANDS OR IN
FREQUENCY BANDS ALLOCATED TO THE FEDERAL GOVERNMENT ON AN EXCLUSIVE
BASIS.
37](#manufacturers-should-only-be-required-to-declare-their-devices-as-a-software-defined-radio-if-the-device-is-remotely-programmable-and-has-hardware-capable-of-transmitting-in-the-restricted-frequency-bands-or-in-frequency-bands-allocated-to-the-federal-government-on-an-exclusive-basis.)

[XVI. TECHNICAL ISSUES RELATED TO THE COMPLIANCE MEASUREMENTS OF
UNLICENSED DEVICES THAT EMPLOY COGNITIVE RADIO TECHNIQUES MUST BE
ADDRESSED PRIOR TO IMPLEMENTATION.
39](#technical-issues-related-to-the-compliance-measurements-of-unlicensed-devices-that-employ-cognitive-radio-techniques-must-be-addressed-prior-to-implementation.)

[XVII. A NEW SUBPART UNDER PART 15 OF THE COMMISSION'S RULES SHOULD BE
ESTABLISHED FOR UNLICENSED DEVICES EMPLOYING COGNITIVE RADIO TECHNIQUES.
43](#a-new-subpart-under-part-15-of-the-commissions-rules-should-be-established-for-unlicensed-devices-employing-cognitive-radio-techniques.)

[XVIII. UNLICENSED DEVICES CAPABLE OF OPERATING ON NON-PART 15
FREQUENCIES MUST INCORPORATE FREQUENCY SENSING OR GEO-LOCATIOIN
CAPABILITIES.
44](#unlicensed-devices-capable-of-operating-on-non-part-15-frequencies-must-incorporate-frequency-sensing-or-geo-locatioin-capabilities.)

[XIX. CONCLUSION 46](#conclusion)

> ASSESSMENT OF POTENTIAL INTERFERENCE TO RADAR
>
> SYSTEMS IN THE 5725-5875 MHz BAND FROM HIGHER-POWERED UNLICENSED
> DEVICES EMPLOYING DYNAMIC FREQUENCY
> SELECTION...............\......................................................APPENDIX
> A
>
> PART 15 UNWANTED EMISSION SEPARATION DISTANCE
> ANALYSIS...............\.......................................................APPENDIX
> B
>
> ISSUES RELATED TO GEO-LOCATION COGNITIVE RADIO
> TECHNIQUES............\......................................................APPENDIX
> C
>
> ISSUES RELATED TO DEVICES EMPLOYING MESH
> NETWORKING............\......................................................APPENDIX
> D
>
> GEO-LOCATION TECHNIQUES AS A METHOD TO PROTECT
>
> OVER-THE-AIR SOFTWARE DOWNLOADS...........................APPENDIX E

# EXECUTIVE SUMMARY {#executive-summary .unnumbered}

The National Telecommunications and Information Administration (NTIA)
commends the Federal Communications Commission (Commission) for
initiating this proceeding to examine issues related to the development
and deployment of cognitive radio (CR) technology. NTIA believes that CR
technology has the potential to provide more innovative, flexible, and
comprehensive use of the radio frequency spectrum, while at the same
time minimizing the risk of interference to other spectrum users. CRs
can be developed that have the technical capability to adapt their use
of the spectrum in response to information external to the radio. As a
result of this technical and operational flexibility, CR technologies
may also make it possible to use spectrum that may be available in a
particular geographic location or during a particular period of time and
would otherwise go unused. At this time, there is not a clear boundary
between CR and software defined radio (SDR) technologies. In many
instances, SDR will be used as the basic platform on which to build CR
technology. For this reason, the comments will in certain cases address
SDR issues as well as CR, since certain aspects of the SDR regulatory
framework could influence the transition from SDR to CR. NTIA offers the
following comments in response to the specific issues raised by the
Commission in the Notice of Proposed Rulemaking (NPRM).

There is little information given in the NPRM on what CR technologies
and techniques are viable today, or in the near future, and what
techniques or technologies may only be achievable with advances in
technology. NTIA believes that given the relative maturity of the
sensing and geo-location techniques proposed in the NPRM, employing them
to facilitate sharing in the restricted frequency bands is not
practical. Therefore, NTIA agrees with the Commission's tentative
conclusion that unlicensed devices employing CR techniques should be
prohibited from operating in the restricted frequency bands listed in
Section 15.205 of the Commission's Rules.

NTIA analysis indicates that when the transmit bandwidth of the
unlicensed device is greater than 6 MHz, the power levels and detection
threshold proposed by the Commission are adequate to protect government
radar systems operating in the 5725-5875 MHz band. For transmit
bandwidths less than 6 MHz, NTIA analysis indicates that the power
levels of the unlicensed device would have to be reduced below the level
proposed by the Commission to protect these government radar systems.
Since there were many technical parameters that were not included in the
Commission's proposal, NTIA considers this a preliminary assessment of
the potential interference to government radar systems operating in the
5725-5875 MHz band. If service rules are eventually adopted for
higher-powered unlicensed devices operating in the 5725-5875 MHz band
that are significantly different than those considered in the assessment
in Appendix A, NTIA would have to reassess the sharing situation.

When the level of unwanted emissions are independent of the in-channel
power, NTIA recommends that the limits specified in Sections 15.247 and
15.249 of the Commission's Rules be applied for the higher-powered
unlicensed devices as proposed by the Commission. For higher-powered
unlicensed devices where the unwanted emissions are dependent on the
in-channel power level, the unwanted emission limit should be reduced
commensurate with the increase in the in-channel power level.

NTIA believes that geo-location technology used in conjunction with an
on-line database of sites that require protection holds promise for
facilitating sharing between unlicensed devices and radio services using
receivers at fixed locations. However, there are many issues related to
the accuracy and integrity of the on-line database as well as the
integrity of the data downloaded to the unlicensed device that must be
addressed.

The lack of interoperability is the most significant problem contained
in after action reports from major public safety incidents. Arguably,
SDR and eventually CR promise to be the best long-term interoperability
solution. The Commission's Rules are not limiting the use of SDR to
facilitate the interoperability between public safety systems. However,
there still remain technical, legal, and cost issues that need to be
resolved before the full benefits of SDR can be realized as a solution
for public safety interoperability.

Mesh networks allow nodes or access points to communicate with other
nodes without being routed through a central switch point, eliminating
centralized failure, and providing self-healing and self-organization.
NTIA believes that the short range characteristics of mesh networks lend
themselves to using higher frequencies. NTIA also believes that mesh
networks have the capability to increase capacity as the number of nodes
increases, enabling them to deliver broadband data rates to support
high-speed data, video and voice applications.

Geo-encryption is an approach to location-based encryption that builds
on established cryptographic algorithms and protocols. Geo-encryption
techniques can support both fixed and mobile applications and a variety
of data-sharing and distribution policies. NTIA believes that
geo-encryption techniques can be used in conjunction with existing
encryption techniques to provide protection of over-the-air software
downloads and should be considered in future rulemakings on CR and SDR
technologies.

If the Commission contemplates expanding the implementation of
higher-powered unlicensed device operations employing CR techniques,
NTIA recommends that the frequency bands transferred from federal
government to private sector use be considered, because, at this time,
these bands have limited government or commercial use or have not been
transferred for private sector use.

NTIA supports the actions taken by the Commission to remove regulatory
barriers to the development of secondary markets. These flexible
policies will continue the evolution toward greater reliance on the
marketplace to expand the scope of available wireless services. Because
CRs can play an enabling role in the establishment of secondary markets,
the development of CR technology should also have similar, minimum
regulatory constraints.

There is no reason to regulate component parts such as digital-to-analog
converter (DAC) integrated circuits and the Commission should avoid any
regulation that would likely stifle their use. A DAC add-in card alone
does not possess the capability to act as a transmitter, and thus should
not be subject to regulation as a radio transmitter under the
Commission's Rules. If a DAC is coupled with an amplifier and antenna,
it should be considered a SDR or CR and regulated under the applicable
section of the Commission's Rules. NTIA also recommends that as
potential consumer applications of DAC based radio frequency signal
sources become better understood, the Commission consider revisiting its
regulation.

NTIA is concerned about the regulatory implications associated with
downloaded software that can reconfigure the radio functionality, which
includes frequency, power, and modulation. NTIA understands the
Commission's reluctance to adopt specific security requirements because
this may constrain the development SDR technology. However, NTIA
believes that the acceptance of SDR and eventually CR technologies
hinges on assurances that the operating parameters that can impact
electromagnetic compatibility with other systems are protected from
malicious attacks. NTIA recommends that as a long-term goal of
addressing security concerns for devices that employ SDR and CR
technologies, the Commission should consider requiring Protection
Profiles as part of the equipment certification.

NTIA agrees with the Commission that examination of software is not an
effective means of identifying where unauthorized software changes have
been made in an SDR. NTIA believes that the Commission's requirement
that certified devices must comply with their applicable technical rules
is sufficient to safeguard against unauthorized equipment modifications.
Thus, NTIA agrees with the Commission's proposal to eliminate the
existing requirement for applicants to provide copies of their software
as part of the certification process for SDRs.

NTIA believes that it would be appropriate for the Commission to require
manufacturers to declare their devices as SDRs if the device is remotely
programmable and has hardware that is capable of transmitting in the
restricted frequency bands or in frequency bands allocated to the
federal government on an exclusive basis. This would eliminate the
problems associated with incorrectly classifying commercial devices such
as land mobile radio and personal communication service as SDRs.

CR devices that are capable of changing their electromagnetic
characteristics on a near real-time basis will make the compliance
measurements more complex. NTIA believes that technological approaches
that cannot be verified in the Telecommunication Certification Bodies'
laboratories should not be relied upon for successful spectrum sharing.
NTIA recommends that the Commission resolve all of the technical issues
related to performing the compliance measurements prior to implementing
CR techniques in any frequency band. NTIA further recommends that the
compliance measurement procedures for devices employing CR technologies
be developed in an open forum, and government and non-government parties
should participate.

NTIA recommends that a new subpart within Part 15 of the Commission's
Rules be established for unlicensed devices that employ CR techniques.
This is similar to the approach used for unlicensed UWB devices, which
also did not fit into the existing Part 15 Rules. NTIA also recommends
that the Commission adopt a definition for CR in order to provide
regulatory certainty to manufacturers seeking industry investment in
devices based on these new technologies.

If the Commission adopts its proposal to certify unlicensed devices that
are capable of using non-Part 15 frequencies then it should limit this
to devices where the central controllers can control the transmit
frequencies of the client devices. As part of the device certification
process it is imperative that it be ensured that the central controllers
can only operate in the bands authorized for Part 15 operations. For
unlicensed devices that operate without a central controller, the device
should be required to incorporate geo-location capabilities, such as the
Global Positioning System, in conjunction with a database, to determine
its geographic location. The location information would then be used to
control the authorized frequencies that the unlicensed device can use.
Furthermore, if the unlicensed device is not capable of determining its
geographic location, the device must be restricted from transmitting.

NTIA agrees with the Commission regarding the significant benefits that
could be gained by employing CR technologies. The NPRM identifies
several areas where technical and regulatory issues must be addressed.
NTIA supports the Commission's initial implementation approach, limiting
CR technologies to a few frequency bands primarily used by unlicensed
devices. NTIA believes that the experience gained in these frequency
bands will help facilitate a much broader implementation of CR
technologies while ensuring that government and non-government spectrum
users are adequately protected from interference. NTIA will continue to
work with the Commission and industry to resolve the technical and
regulatory issues surrounding the successful implementation of CR
technologies.

**Before the**

**FEDERAL COMMUNICATIONS COMMISSION**

**Washington, DC 20554**

+-------------------------------------+---+----------------------------+
| In the Matter of                    | ) | ET Docket No. 03-108       |
|                                     |   |                            |
| Facilitating Opportunities for      | ) | ET Docket No. 00-47        |
| Flexible, Efficient,                |   |                            |
|                                     | ) | (Terminated)               |
| and Reliable Spectrum Use Employing |   |                            |
| Cognitive                           | ) |                            |
|                                     |   |                            |
| Radio Technologies                  | ) |                            |
|                                     |   |                            |
| Authorization and Use of Software   | ) |                            |
| Defined                             |   |                            |
|                                     | ) |                            |
| Radios                              |   |                            |
|                                     | ) |                            |
+-------------------------------------+---+----------------------------+

**[COMMENTS OF THE NATIONAL TELECOMMUNICATIONS]{.underline}**

**[AND INFORMATION ADMINISTRATION]{.underline}**

The National Telecommunications and Information Administration (NTIA),
an Executive Branch agency within the Department of Commerce, is the
President's principal adviser on domestic and international
telecommunications policy, including policies relating to the Nation's
economic and technological advancement in telecommunications.
Accordingly, NTIA makes recommendations regarding telecommunications
policies and presents Executive Branch views on telecommunications
matters to the Congress, the Federal Communications Commission
(Commission), and the public. NTIA, through the Office of Spectrum
Management (OSM), is also responsible for managing the federal
government's use of the radio frequency spectrum. NTIA respectfully
submits the following comments in response to the Commission's Notice of
Proposed Rulemaking (NPRM) in the above-captioned proceeding.[^1]

# INTRODUCTION

In the NPRM, the Commission seeks comments on ways to encourage and
remove regulatory impediments to the continued development and
deployment of cognitive radio (CR) technologies. For example,
facilitating the ability of licensed spectrum users to deploy CR for
their own use to increase spectrum efficiency, and to facilitate
secondary markets, allowing licensees to lease their spectrum access to
third parties using such technologies. The Commission seeks comment on
ways in which CR can facilitate opportunistic use of the spectrum by
unlicensed devices, while protecting incumbent licensed spectrum users
from interference; rules permitting additional flexibility, including
allowing unlicensed devices, in limited frequency bands to use higher
transmit power in rural and underserved areas; a specific technical
approach that would provide licensees, such as public safety entities,
with the ability to retain real-time access to spectrum they lease to
third parties; how CR can enhance the ability of different public safety
entities using different frequencies and formats to communicate with one
another in the event of an emergency; and specific applications of CR,
such as mesh networks and real-time frequency coordination between
non-geostationary orbit satellite systems and other services. The
Commission also proposes changes to its equipment authorization
processes to better accommodate software defined radio (SDR) and CR
systems.

At this time, there is not a clear boundary between CR and SDR
technologies. In many instances, SDR will be used as the basic platform
on which to build CR technology. For this reason, NTIA's comments will
in certain cases address SDR issues as well as CR, since certain aspects
of the SDR regulatory framework could influence the transition from SDR
to CR. For example, SDR could support interoperability by providing the
capability where the user selects the required radio configuration based
on knowledge of the users and communication content for a given region.
This SDR could evolve into a CR that senses the radio frequency (RF)
environment and automatically selects the desired radio configuration or
might even have the capability to recognize that another band is not
being used in the area of interest and thus could direct certain users
in a congested band to this alternative frequency band.

NTIA commends the Commission for initiating this proceeding to examine
issues related to the development and deployment of CR technology. NTIA
believes that CR technology has the potential to provide more
innovative, flexible, and comprehensive use of the RF spectrum, while at
the same time minimizing the risk of interference to other spectrum
users. However, there are technical and regulatory issues related to
implementing CR as well as concerns regarding potential interference to
federal spectrum users that must first be addressed. NTIA offers the
following comments in response to the specific issues raised by the
Commission in the NPRM.

# COGNITIVE RADIO CAPABILITIES CAN BE USED TO RESOLVE SPECTRUM SCARCITY, DEPLOYMENT, AND TECHNOLOGY TRANSITION PROBLEMS ENCOUNTERED BY GOVERNMENT AND NON-GOVERNMENT WIRELESS SYSTEMS.

There are a number of capabilities, such as frequency agility, adaptive
modulation, transmitter power control (TPC), location of itself and
other transmitters, and mechanisms to enable sharing on an ad-hoc or
real-time basis, that can be incorporated in CRs. The Commission seeks
comment on what other features and capabilities a CR could
incorporate.[^2]

There are several problems confronting both government and
non-government wireless communications users with respect to spectrum
use: scarcity of spectrum, deployment difficulties, and transitioning to
different technologies. The federal government agencies are placing an
increasing emphasis on SDR and using SDR as the basic platform on which
to build CR technology to resolve these problems. For example, through
research projects such as the Defense Advanced Research Projects Agency
(DARPA) neXt Generation (XG) program, the Department of Defense (DOD) is
investigating how advanced sensing, modulation, and multiple access
technologies can be used with a machine-intelligible spectrum policy
framework to enable cognitive spectrum sharing that could improve
spectrum usage efficiency by a factor of ten or more.[^3] As the
Commission points out, SDRs are likely to be the best platforms for
implementing CR, and the tactical military SDRs being developed under
the Joint Tactical Radio System (JTRS) may well be the beneficiaries of
the XG technology. The application of XG technology to JTRS has the
potential to address the spectrum scarcity and deployment issues that
could limit the military's broadband wireless end-to-end connectivity.
Like DARPA's early work on the Internet, XG-based technology will become
applicable to both military and civilian applications. The National
Science Foundation (NSF) is also exploring the technology developments
needed for enhancing spectral efficiencies of wireless networks in
support of expanding opportunities for new services in the wireless
industry. NSF's Networking Technology Systems (NeTS) program is
addressing the challenges associated with these networks.[^4]

Over the years, the development of better electronic equipment has
allowed the channel spacing employed by many radio services to be
decreased. For example, many radio services have changed channel spacing
from 100 kHz to 50 kHz, then to 25 kHz, and now radio services are
instituting even narrower channels (e.g., 12.5 kHz and 6.25 kHz in some
land mobile frequency bands). Because of the need for backward
compatibility, however, most of the radio services cannot take full,
immediate advantage of the increased spectrum use of narrower channels.
For example, legacy equipment does not have the capability to tune to
the interstitial channels. Moreover, transition of these services from
analog to digital modulation techniques, which can support a more
flexible and efficient use of the spectrum, has been difficult because
of the backward compatibility requirement. CRs could facilitate this
transition in channelization and modulation schemes. By being able to
switch modulation/detection schemes, to switch frequencies and
bandwidths of operation, and possibly, to sense the characteristics of
received signals and to institute actions based on these
characteristics, CR could operate in this transitional environment.
Since the particular service in question is largely under the control of
a single user group or entity, the transition can be planned and
implemented in an orderly fashion, possibly segmenting the band for
different operations to provide support for newer equipment (new
channelization and modulation) as well as legacy systems (old
channelization and modulation). This band segmentation would gradually
be phased-out, however, during and after the transition, the CR would be
capable of operating across the band. Because of the planned transition
of the band, the CR requirements would be fairly well defined. For
example, the Federal Aviation Administration's Next-Generation
Air/Ground Radio Communications System (NEXCOM) will be employing some
of these techniques to meet the growing need for voice services while
also providing a robust data link.[^5]

The federal government is developing CR technologies that are able to
sense, characterize, identify, distribute, and allocate spectrum use
opportunities. These CR capabilities may eventually be used to resolve
the spectrum scarcity and deployment problems encountered by government
and non-government wireless systems. CR capabilities can also be used to
resolve problems encountered when transitioning from one technology or
another within a frequency band or radio service.

# HIGHER-POWERED UNLICENSED DEVICES EMPLOYING COGNITIVE RADIO TECHNIQUES SHOULD BE PROHIBITED FROM OPERATING IN THE RESTRICTED FREQUENCY BANDS LISTED IN SECTION 15.205 OF THE COMMISSION'S RULES.

The Commission concluded that it should continue to prohibit unlicensed
devices from emitting in the designated restricted frequency bands,
which includes many bands used by the federal government. The Commission
seeks comment on this tentative conclusion.[^6]

> The restricted frequency bands in Section 15.205 of the Commission's
> Rules are used to support safety-of-life functions, such as
> aeronautical radionavigation, military satellite communications, and
> scientific observations. The federal systems that operate in the
> restricted frequency bands may be passive, such as radio astronomy, or
> active, such as satellite downlinks. The NPRM focuses on two types of
> CR techniques: sensing techniques and geo-location techniques.
> However, NTIA believes that there are potential problems with
> effectively implementing either of these CR techniques in the
> restricted frequency bands.
>
> For CR sensing techniques to be effective in facilitating sharing with
> other radio services, it must be able to detect a signal that is above
> a specified threshold. The presence of a signal above the detection
> threshold indicates that the channel is being used and the CR-enabled
> device should not transmit. If the signal is below the threshold or
> the sensitivity of the sensor receiver is not adequate to detect the
> signal, the CR-enabled device will transmit and potentially cause
> interference to other receivers operating in the band. It is difficult
> to envision how CR sensing techniques can be implemented in many of
> the restricted frequency bands since the detection thresholds would
> have to be much lower than can be supported by current technology. For
> example, due to the extremely low power of the cosmic signals studied
> by the radio astronomy and passive services, these operations are very
> susceptible to interference. The permissible interference levels in
> several radio astronomy frequency bands are shown in Table 1.[^7]

**Table 1.**

+-----------------------------------+-----------------------------------+
| > **Frequency Range**             | > **Permissible Interference      |
| >                                 | > Level**                         |
| > **(MHz)**                       | >                                 |
|                                   | > **(dBW)**                       |
+-----------------------------------+-----------------------------------+
| > 608-614                         | > -202                            |
+-----------------------------------+-----------------------------------+
| > 1400-1427                       | > -205                            |
+-----------------------------------+-----------------------------------+
| > 4990-5000                       | > -207                            |
+-----------------------------------+-----------------------------------+

These permissible interference levels would be used as the basis for
establishing the detection thresholds for CR sensing techniques, and are
believed to be outside the range of any practical sensing techniques
currently available. Therefore, NTIA does not believe that CR sensing
techniques can be implemented in the restricted frequency bands used by
the radio astronomy and passive services.

Implementing CR sensing techniques in the restricted frequency bands
used to support receive-only operations would face problems similar to
those identified for the passive services. This would apply to frequency
bands used by military satellite downlink communications or the
radionavigation satellite service (RNSS), which are capable of receiving
very weak desired signals. For example, the Global Positioning System
(GPS), which operates in the frequency bands allocated for RNSS, employs
direct sequence spread spectrum (DSSS) and receivers are capable of
processing desired signal levels below the noise floor. For an
unlicensed device employing CR sensing techniques to protect RNSS
receivers the detection threshold would have to be below the thermal
noise floor, which NTIA does not believe is feasible using existing
technology.[^8]

CR sensing techniques would also be difficult to effectively implement
in any of the restricted frequency bands where the receivers are mobile
and transmissions are non-continuous. This situation occurs in the
restricted frequency bands used by the aeronautical radionavigation
service (ARNS). In the ARNS, ground-based stations are transmitting and
receiving information from aircraft that can be located anywhere. The
desired signals at the airborne receiver can vary significantly, making
sensing techniques that protect these critical safety-of-life functions
difficult to implement. Further complicating the problem is that the
transmissions from the ground stations are non-continuous, and it would
be very difficult, if not impossible, for CR sensing techniques to
predict with any degree of certainty when the primary user activity be
initiated or resume on the channel.

When the locations of the licensed systems are known and fixed, CR
geo-location techniques hold promise for facilitating sharing with
unlicensed devices. However, many designated restricted frequency bands
are used for military satellite communications and the locations of
these receivers cannot be identified. There are also many restricted
frequency bands that are used by mobile receivers, such as those in the
ARNS and RNSS. NTIA believes that CR geo-location techniques would not
be effective in protecting the critical safety-of-life operations in
these frequency bands. The Commission needs to resolve questions
regarding accessing an on-line database on a near real-time basis, the
integrity of the data downloading process, and how the database is
maintained.

The NPRM provides little information on what technologies and techniques
are viable today, or in the near future, and what techniques or
technologies may only be achievable with potential advances in
technology in the future. NTIA believes that given the relative maturity
of the sensing and geo-location techniques proposed in the NPRM,
employing them to facilitate sharing in the restricted frequency bands
is not practical. Therefore, NTIA agrees with the Commission's tentative
conclusion that unlicensed devices employing CR techniques should be
prohibited from operating in the restricted frequency bands listed in
Section 15.205 of the Commission's Rules.

# THE COMMISSION'S PROPOSAL FOR HIGHER-POWERED UNLICENSED DEVICE OPERATIONS IN THE 5725-5875 MHz BAND IS ADEQUATE TO PROTECT GOVERNMENT RADAR SYSTEMS IF A MINIMUM TRANSMIT BANDWIDTH IS ESTABLISHED.

The Commission proposes to allow a transmitter power increase of up to
six times the current limits in the frequency bands specified in
Sections 15.247 and 15.249 of its Rules.[^9] The Commission proposes to
restrict the higher power operation to areas with limited spectrum use
and to require the unlicensed devices to sense spectrum use before
commencing transmission.[^10] The Commission seeks comment on the
potential effects of this proposal, including its CR safeguards of
federal radio operations in the 5725-5925 MHz band.[^11]

Federal government users in the 5725-5875 MHz band include fixed,
transportable, and mobile radar systems operated by the DOD. These
radars are used extensively in support of national and military test
range operations in the tracking and control of manned and unmanned
airborne vehicles.[^12] As pointed out in the NPRM, many of the
installations where these radar systems operate are located in rural
areas to avoid interference with other systems.[^13] Federal agencies
are increasingly concerned regarding potential interference to these
radar systems as their role expands in support of homeland defense. This
expanded role could result in a requirement to deploy radar systems in
areas close to cities and highways, potentially increasing interference
to the radar systems from unlicensed devices operating at higher power
levels.

Under the Commission's proposal, the higher-powered unlicensed device
operations would be limited to rural areas or areas where it is
determined that spectrum use is limited.[^14] The Commission proposed
that the unlicensed devices operating in these rural or unused areas
employ sensing techniques with a detection threshold of 30 dB above the
thermal noise floor within a measurement bandwidth of 1.25 MHz.[^15] The
potential interference between military radar systems operating in the
5250-5350 MHz and 5470-5725 MHz bands and Unlicensed National
Information Infrastructure (U-NII) devices employing a sensing technique
referred to as dynamic frequency selection (DFS)[^16] was addressed as
part of another rulemaking proceeding.[^17] The analysis performed to
develop the detection thresholds for DFS equipped U-NII devices
considered specific unlicensed device densities and power levels that
are different than those proposed by the Commission in the NPRM.
Therefore, NTIA must perform an analysis to assess whether the power
levels in conjunction with the detection threshold proposed by the
Commission are adequate to protect government radar systems operating in
the 5725-5875 MHz band.

In the NPRM, the Commission proposed a transmitter power level of 38 dBm
in the 5725-5850 MHz band and 6 dBm in the 5725-5875 MHz band to be used
in conjunction with the DFS sensing technique.[^18] As discussed
earlier, the Commission also proposed a detection threshold of -83 dBm
measured in a 1.25 MHz bandwidth.[^19] However, the proposal in the NPRM
did not identify the unlicensed device application which could have an
impact on the device density and antenna heights, the transmit bandwidth
of the unlicensed device application (e.g., narrowband or wideband), or
the type of antenna (e.g., omnidirectional or directional). All of these
parameters can have an impact on the electromagnetic compatibility of
the proposed unlicensed devices and the government radar systems.

To assess the potential interference to government radar systems from
the unlicensed devices using the higher power levels and the detection
threshold proposed by the Commission, NTIA performed an analysis. The
analysis provided in Appendix A describes the operational scenario for
the unlicensed devices and the military radar systems; technical
characteristics of the radar systems and unlicensed devices; and the
engineering algorithms used to assess the potential for interference to
the radar systems from the higher-powered DFS-equipped unlicensed
devices. The parametric analysis performed to assess the potential
interference to government radar systems considered different
combinations of the number of unlicensed devices, unlicensed device
antenna heights, and unlicensed device transmit bandwidths. Monte Carlo
techniques were employed for the unlicensed device locations,
propagation losses, antenna heights, and other non-terrain specific
losses.[^20]

The analysis indicates that when the transmit bandwidth of the
unlicensed device is greater than 6 MHz, the power levels and detection
threshold proposed by the Commission are adequate to protect government
radar systems operating in the 5725-5875 MHz band. For transmit
bandwidths less than 6 MHz, the power levels of the unlicensed device
would have to be reduced below the level proposed by the Commission to
protect these government radar systems. Since there were many technical
parameters that were not included in the Commission's proposal, NTIA's
analysis is a preliminary assessment of the potential interference to
government radar systems operating in the 5725-5875 MHz band. To support
5725-5875 MHz band service rules for unlicensed devices significantly
different than those considered in the assessment in Appendix A, NTIA
would have to re-evaluate the sharing situation.

In addition to the detection threshold, the following parameters
associated with the CR sensing technique must be defined: channel
availability check time, channel move time, non-occupancy period,
detector function (peak or average), and measurement interval.[^21]
Since the radar systems operating in the 5725-5875 MHz band are the same
as those operating in the 5250-5350 MHz and 5470-5725 MHz U-NII
frequency bands, then the values of the radar parameters associated with
the detection threshold would be the same.[^22] The Commission specifies
a measurement bandwidth of 1.25 MHz, which is consistent with the
channel width of code division multiple access PCS systems. To be
consistent with the measurements for the radars operating in other
portions of the 5 GHz band where DFS is being implemented, NTIA
recommends that a measurement bandwidth for the detection level of 1 MHz
be used instead of 1.25 MHz.

# THE REDUCTION OF UNWANTED EMISSIONS FOR HIGHER POWER UNLICENSED DEVICES SHOULD BE COMMENSURATE WITH THE INCREASED IN-CHANNEL POWER LEVEL.

The Commission proposes that unlicensed devices operating at the higher
power levels comply with the same harmonic and out-of-band emission
limits as devices operating under Sections 15.247 and 15.249 of its
Rules.[^23] The Commission seeks comment on whether the out-of-band
emission limits for equipment operating at the higher power levels
should be adjusted so that they are no greater than those permitted
under the current rules.[^24]

The emissions generated by a device can be divided into three
categories: necessary emissions generated within the channel of the
device (in-channel); out-of-band emissions generated as a result of the
modulation process; and spurious emissions such as harmonically
generated emissions. The combination of out-of-band and spurious
emissions are referred to as unwanted emissions.

The current harmonic emission limits for unlicensed devices operating
under Section 15.249 are independent of the in-channel power, while the
out-of-band emission limits are a function of the in-channel power. For
devices operating under Section 15.247 of the Commission's Rules, the
limits on out-of-band emissions that fall within the designated
restricted frequency bands are independent of the in-channel power
levels. However, under Section 15.247, the limit on out-of-band
emissions that fall outside of the restricted frequency bands are a
function of the in-channel power level.

As shown in Appendix B, the unwanted emission limits specified in Part
15 of the Commission's Rules are inadequate to protect other authorized
radio services unless either a large distance separation or additional
attenuation resulting from buildings or terrain are included in the
analysis. However, given the large number of Part 15 devices in use
today, NTIA is unaware of any reports where a compliant unlicensed
device has interfered with another authorized spectrum user. NTIA
believes that in part this can be attributed to Part 15 devices
generating unwanted emission levels that are well below those specified
in the Commission's Rules.[^25] NTIA has limited data to support this
presumption, and thus, cannot comment on whether the actual unwanted
emission levels specified in Sections 15.247 and 15.249 of the
Commission's Rules adequately protect other radio services.

The harmonic and out-of-band emission limits specified in Sections
15.247 and 15.249 fall into two categories: limits that are dependent on
the in-channel power levels, and limits that are independent of the
in-channel power levels. For harmonic and unwanted emissions that are
independent of the in-channel power (e.g., a fixed field strength
level), NTIA recommends that the limits specified in Sections 15.247 and
15.249 be applied for the higher-powered unlicensed devices as proposed
by the Commission. For higher-powered unlicensed devices where the
unwanted emissions are dependent on the in-channel power level, the
unwanted emission limit should be reduced commensurate with the increase
in the in-channel power level. In the Commission's proposal, this would
result in a reduction of 8 dB in the unwanted emission levels for the
higher-powered devices.

# GEO-LOCATION TECHNOLOGIES USED IN CONJUNCTION WITH AN ON-LINE DATABASE HOLDS PROMISE FOR SHARING BETWEEN UNLICENSED DEVICES AND RADIO SERVICES USING RECEIVERS AT FIXED LOCATIONS.

The Commission seeks comment on the positional accuracy necessary if
geo-location technology such as the Global Positioning System (GPS) were
used. Related to CR geo-location techniques, the Commission also
requests comment on how a device using geo-location would access a table
or database showing where operation is permitted; who would be
responsible for maintaining the database; should the geo-location
technology be required to be incorporated within the device; and how
would the device react if it were unable to determine its position
within a specified accuracy limit.[^26]

The positional accuracy of different GPS receiver architectures is
discussed in Appendix C. The Commission adopted accuracy and reliability
requirements for Automatic Location Identification as part of its Rules
for wireless carrier enhanced 911 (E911) service.[^27] The accuracy and
reliability requirements for E911 Phase II operations for handset-based
solutions are 50 meters for 67 percent of calls, 150 meters for 95
percent of the calls. NTIA recommends that the Commission adopt
positional accuracy requirements for CR devices employing geo-location
capabilities that are at least as stringent as the E911 requirements.
Many manufacturers are developing GPS chipsets to meet the Commission's
December 31, 2005 Phase II deadline, so the technology should be
available at a reasonable cost. The Commission's Office of Engineering
and Technology has also developed guidelines for testing and verifying
these positional accuracy requirements.[^28]

In comments filed in response to another rulemaking proceeding, the
Institute of Electrical and Electronics Engineers (IEEE) 820.18 Radio
Regulatory Technical Advisory Group stated that embedding GPS technology
in unlicensed devices is technically feasible and could be used to limit
the device so it does not transmit when located in or near an area where
interference to a fixed receiver is likely.[^29] NTIA agrees with the
IEEE that unlicensed devices that employ GPS technology in conjunction
with an on-line database of the fixed site locations can be used to
prohibit that device from operating in those areas.[^30] Issues related
to the implementation of geo-location techniques and the on-line
database are discussed in Appendix C.

NTIA also agrees with the IEEE that it is feasible to incorporate GPS
chipsets within unlicensed devices. As discussed earlier, GPS chipsets
are being incorporated in handsets to meet the Commission's E911
mandate. Incorporating the geo-location hardware in the unlicensed
device is the only practical way from an interference protection
standpoint to effectively implement geo-location technology. NTIA
recommends that if the Commission permits geo-location technology to
facilitate sharing with other fixed receivers, the position location
technology should be incorporated within the unlicensed device.

GPS signal failures can occur in urban canyons, indoors, or in shaded
areas where the received signals are too noisy, too attenuated or
distorted by multipath to be received and used reliably in ranging.
Under such conditions, demodulating the navigation data included in the
satellite broadcast becomes practically impossible.[^31] Appendix C
describes a technology that can be deployed to compensate for losses in
the satellite signal. The time between when this momentary loss of
satellite signals occurs and when the receiver can no longer provide
position information depends on the GPS receiver architecture,
application, and manufacturer implementation. Since unlicensed devices
that employ geo-location techniques require a position location to
control device transmissions, it is important to determine how much time
should be permitted after the position location is lost and when the
device must cease all transmissions. Appendix C shows that using 60
seconds after position information is no longer available as the upper
limit for unlicensed devices employing geo-location techniques to cease
transmissions seems reasonable. However, larger separation distances
between unlicensed devices and the fixed receivers could accommodate
longer periods of time when the geo-location capability is not
available.

NTIA believes that geo-location technology used in conjunction with an
on-line database of sites that require protection holds promise for
facilitating sharing between unlicensed devices and radio services using
receivers at fixed locations. NTIA believes that GPS-based technology
incorporated within the unlicensed device is capable of providing
position locations with the necessary accuracy. However, many issues
related to the accuracy and integrity of the on-line database as well as
the integrity of the data downloaded to the unlicensed device must be
addressed. If the geo-location device is unable to obtain a location, or
the database is not successfully downloaded, the unlicensed device
should not be permitted to transmit. In a separate rulemaking, the
Commission is proposing to implement geo-location techniques to permit
sharing between unlicensed devices and fixed-satellite earth station and
radar receivers operating in the 3650-3700 MHz band. NTIA believes that
the experience gained with implementing geo-location technology in the
3650-3700 MHz band can be used to address the issues related to the
unlicensed device interface with the on-line database.

# TECHNICAL, COST, AND LEGAL ISSUES, NOT THE COMMISSION'S RULES ARE LIMITING THE IMPLEMENTATION OF SOFTWARE DEFINED RADIO AS A POTENTIAL SOLUTION TO THE PUBLIC SAFETY INTEROPERABILITY PROBLEM.

The Commission seeks comment on how CR technologies can facilitate
interoperability between systems. Specifically, the Commission seeks
comment on any rule changes necessary to take advantage of these
benefits for interoperability between systems.[^32]

The Public Safety Wireless Advisory Committee (PSWAC) Final Report
defines interoperability as the ability of two or more public safety
communications systems to interact with one another and exchange
information according to a prescribed manner in order to achieve
predictable results.[^33] Interoperability between users is divided into
three categories with each having specific characteristics: day-to-day
interoperability, mutual aid interoperability, and task force
interoperability. The SAFECOM Program, managed by the Department of
Homeland Security, issued a statement of requirements for public safety
wireless communications and interoperability that delineates many public
safety wireless operational scenarios.[^34]

There are more than 18,000 law enforcement agencies and over 35,000 fire
and emergency medical service agencies across the United States.[^35]
Due to the fragmented nature of this community, most public safety
communications systems are individual systems that do not easily
communicate with one another or facilitate interoperability. Federal,
state, and local public safety communication systems operate in ten
discrete bands ranging from 30 MHz to 869 MHz and employ a number of
different air-interface protocols.[^36] As a result of the fragmentation
of frequency bands and air-interface standards, multiple agencies
converging on a single incident often cannot communicate with each other
using their radio systems. SDR and eventually CR promises to be the best
long-term interoperability solution. The real need for a public safety
officer, when responding to any situation, is to carry a radio that
offers the ability to communicate with whomever he or she needs in
real-time. That need often must be supported radio-to-radio without the
use of infrastructure for on-scene use at many incidents (e.g., the use
of portables). As already demonstrated by companies such as Thales and
Vanu Inc., SDR offers the potential of providing a multi-band platform
that supports a number of different public safety waveforms.[^37]
Equipping a field officer with a radio that supports the waveforms of
agencies in that geographic area, along with a common national
interoperability waveform, would enable that officer to have direct
interoperability without the need for enabling infrastructure. SDR also
offers the ability to download software of existing waveforms and
supports forward migration to new technologies with new waveforms.

SDR is not yet an on-the street reality. Through a contract with DOD,
Thales has developed the portable Mulitband Inter/Intra Team Radio
(MBITR) that is not yet type-certified for public safety use.[^38]
Likewise, Vanu has demonstrated the Universal Communicator, a
multi-mode, multi-band radio operating on a Compaq iPAQ platform.[^39]
Both require added waveforms to be of significant benefit to the user
community, though they have proven the SDR concept is viable. The SDR
Forum[^40] is also in the process of forming a special interest group
targeted at public safety users.[^41]

Even with the progress in SDR technology in satisfying the requirements
of public safety users, there are still significant technology hurdles
that have yet to be overcome. The development of a public safety
portable subscriber set is hindered by a number of technology
requirements, including battery capacity, antenna development, and
physical form factor. SDR processors and broadband power amplifiers
require significant power. Public safety users require a battery that
will support a radio for shifts that routinely extend 12 hours.
Currently, multi-band antennas are physically too large to carry if they
have to support a very wide range of frequency bands. All of the
hardware, including an appropriate battery, must fit in an easy-to-carry
package with an appropriate form factor that supports ease of use.
Finally, the overall product must be affordable. While agencies may be
willing to pay a premium for the features provided, all are constrained
by today's limited public safety budgets.[^42] Many of these challenges
track those identified by the PSWAC when it considered SDR as a possible
solution to the public safety interoperability problem.[^43]

In addition to the technical issues identified above, issues related to
the licensing of intellectual property (e.g., patents) could be another
impediment to fielding a useful SDR product for use by public safety
entities. Use of the major public safety waveforms, with the exception
of analog frequency modulation, involves technology licensing issues.
These issues will require negotiations with the license holders that
could introduce major delays in bringing SDR products to the marketplace
and involve added cost to the customer.[^44]

The communications equipment used by public safety agencies typically
operate within one of ten discrete radio frequency bands and use various
air-interfaces. The lack of interoperability is the most significant
problem contained in after action reports from major public safety
incidents. Arguably, SDR and eventually CR technologies promise to be
the best long-term interoperability solution, with the potential to
provide the field officer with a belt-worn subscriber unit. As with any
new technology, introduction will be slow and the initial products will
be expensive. However, the benefits obtained from the technology will
eventually drive demand up and cost down. The Commission's Rules are not
limiting the use of SDR to facilitate the interoperability between
public safety systems. Although a great deal of work has been done since
PSWAC identified SDR as a potential solution to the public safety
interoperability problem, technical, legal, and cost issues need to be
resolved before the full benefits of SDR can be realized.

# MESH NETWORKS OPERATING AT HIGHER FREQUENCIES WILL REDUCE INTERFERENCE TO OTHER RADIO SERVICES AND CAN FACILITATE BROADBAND COMMUNICATIONS.

The Commission seeks comment on the application of mesh networking
technology and possible changes needed to facilitate the use of this
technology.[^45] Specifically, how mesh network technology might serve
the Commission's efforts to facilitate broadband communication services
to consumers and any rule changes that might be necessary. The
Commission seeks comment on the impact that mesh networks will have on
the aggregate interference to licensed services.[^46] The Commission
also seeks comment on the ability of mesh network capabilities to "self
heal" to improve the reliability of operations.[^47]

In mesh networks, sophisticated digital modulation schemes, traffic
routing algorithms, and multi-hop architectures are employed that use
minimal transmission power to increase data throughput over greater
distances. With mesh networks, any node within the network can send or
receive messages and can relay messages for any one of its neighboring
nodes, thus providing a relay process where data packets travel through
intermediate nodes toward their final destination. In addition,
automatic rerouting provides redundant communication paths through the
network should any given node fail. This ability to reroute across other
links not only provides increased reliability, but also extends the
network's reach. This resilient, self-healing nature stems from mesh
networks distributed routing architecture where intelligent nodes make
their own routing decisions, avoiding a single point of failure. The
self-healing aspects of mesh networks are discussed in more detail in
Appendix D.

The IEEE 802.15.4 standard specifies a physical layer that could be used
for mesh networking devices. The physical layer defines parameters such
as the frequency, bandwidth, transmit power, and receiver sensitivity.
Given the large number of transmitters in a mesh network that can be
operating simultaneously, there is a potential risk for aggregate
interference to authorized radio services. Currently, the IEEE 802.15.4
standard is implemented in the 902-928 MHz and 2400-2483.5 MHz
Industrial, Scientific, and Medical (ISM) bands. Because these bands are
used primarily by unlicensed devices, there is no impact on federal
government operations if mesh network operations are implemented in
them. Before mesh networks can be implemented in the 5725-5850 MHz ISM
band, however, technical analysis similar to those for the U-NII devices
in the 5 GHz band would have to be performed to assess the potential
impact to government radars that also operate in this band.

Since the length of communications paths for mesh network devices are
short by design, it may be possible to implement this technology at
higher frequency bands where propagation losses are greater. Using
higher frequencies would limit the range of interfering signals within
the mesh network and substantially increase frequency reuse. This is
discussed in more detail in Appendix D.

Another aspect of mesh networks is that the capacity of the mesh
increases as more nodes are added. It may also be possible to use
technologies for the mesh nodes such as ultrawideband (UWB), which has
the potential to support data rates of 100 mega bits per second or more
at short distances. The ability of mesh networks to support higher data
rates is discussed in greater detail in Appendix D.

A mesh network allows nodes or access points to communicate with other
nodes without being routed through a central switch point, eliminating
centralized failure, and providing self-healing and self-organization.
NTIA believes that the short-range characteristics of mesh networks lend
themselves to using higher frequencies. Higher frequencies will become
continually more attractive as RF devices become cheaper and better;
denser device deployments such as mesh networks reduce the required path
length; and demand for wide bandwidths and frequency reuse increases.
Operating at higher frequencies will also reduce the potential for
aggregate interference to other radio services. NTIA believes mesh
networks that have the capability to increase capacity as the number of
nodes increases can deliver broadband data rates to support high-speed
data, video and voice applications.

# GEO-ENCRYPTION TECHNIQUES CAN BE USED IN CONJUNCTION WITH EXISTING ENCRYPTION TECHNIQUES TO PROVIDE PROTECTION OF OVER-THE-AIR SOFTWARE DOWNLOADS.

The Commission seeks comment on whether any modifications are necessary
to the security and authentication requirements in the rules.
Specifically, the Commission seeks comment on whether the current rules
provide adequate safeguards against unauthorized modifications to
SDRs.[^48]

Location-based encryption or geo-encryption refers to any method of
encryption in which ciphertext can be decrypted only at a specified
location.[^49] If someone attempts to decrypt the data at another
location, the decryption process fails and reveals no details about the
original plaintext information. The device performing the decryption
determines its location using some sort of location sensor, such as a
GPS receiver. Location-based encryption can be used to ensure that data
cannot be decrypted outside of a particular facility (*e.g.*, the
headquarters of a government agency or corporation). Alternatively, it
may be used to contain access to a broad geographic region. Time and
space constraints can also be placed on the decryption location.
Appendix E describes one implementation of geo-encryption that builds on
established security algorithms and protocols.

Geo-encryption has the potential to support both fixed and mobile
applications and a variety of data-sharing and distribution policies.
Depending on individual implementations, it can also provide strong
protection against location spoofing. NTIA believes that geo-encryption
techniques can be used in conjunction with existing encryption
techniques to provide protection of over-the-air software downloads.
NTIA recommends that the Commission explore the benefits and possible
implementation of geo-encryption techniques as part of future rulemaking
proceedings on CR and SDR technologies.

# THE INITIAL IMPLEMENTATION OF UNLICENSED COGNITIVE RADIO TECHNOLOGY SHOULD BE LIMITED TO THE INDUSTRIAL, SCIENTIFIC, AND MEDICAL FREQUENCY BANDS AND THE FREQUENCY BANDS TRANSFERRED FROM THE FEDERAL GOVERNMENT.

The Commission seeks comment on whether higher power operation should be
permitted for Part 15 devices. For example, the Commission questions
whether higher power unlicensed device operation should be permitted
under Section 15.209 of the Commission's Rules.[^50]

Section 15.209 of the Commission's Rules permits unlicensed device
operation at specified radiated emission levels, in almost any frequency
band, other than the television broadcast and certain designated
restricted frequency bands.[^51] The restricted frequency bands include
bands used to support safety-of-life functions, such as aeronautical
radionavigation, and bands employed by radio services that must
function, as a nature of their operation, using extremely low received
signal levels. However, there are many frequency bands used by critical
government and non-government radiocommunication systems that are not
included in the restricted frequency band list but also require
protection. Examples of these critical systems include the Federal
Aviation Administration's Terminal Doppler Weather Radar;[^52] the DOD
systems used to provide tracking, telemetry, and control of all military
satellite systems; the National Aeronautics and Space Administration's
Tracking and Data Relay Satellite System; the Department of
Transportation's Intelligent Transportation System;[^53] commercial
cellular and personal communication service (PCS) systems;
point-to-point microwave systems used to support the Nation's critical
infrastructure;[^54] and land mobile communications systems used to
support state, local, and federal public safety. These critical
government and non-government systems span the frequency range of 100
MHz to 7000 MHz.

The low radiated emission levels currently permitted under Section
15.209 are the primary factor that facilitates sharing between
unlicensed devices and the licensed radiocommunication systems. Before
an increase in the power level for unlicensed devices can be considered,
operational parameters (including sharing criteria) of both the licensed
services and the proposed unlicensed uses are required to adequately
determine the necessary technical characteristics of the CR technique to
be employed. An example of an appropriate methodology for conducting the
analyses to define the characteristics of the CR technique can be seen
by examining the U-NII rulemaking proceeding. The analyses used to
determine appropriate thresholds for use by U-NII devices employing DFS
took into account the technical characteristics of the radar transmitter
and receiver (*e.g.*, antenna gain patterns, bandwidth, scan/tracking
rate) as well as the technical characteristics of the unlicensed device
proposed for the radio local area networks (RLAN). For this specific
unlicensed device application, the analysis was used to determine
combinations of transmit power, antenna gain, bandwidth, and measurement
time interval that would allow successful sharing between unlicensed
RLANs and radar systems. Similar analyses would need to be conducted for
each frequency band being considered, each higher-powered unlicensed
application, and the CR techniques to be employed to facilitate sharing.
Each analysis would be unique due to differing technical characteristics
of the various licensed and various unlicensed device applications, as
well as the differing propagation characteristics in each frequency
band.

The effectiveness of the CR technique employed by the unlicensed device
to facilitate sharing with licensed users will be dependent on the
licensed service operating in the band. For example, DFS techniques hold
promise for sharing with radar systems or with other radio services
where the transmitter and receiver are at the same location and where
the propagation path from the DFS-equipped unlicensed device back to the
transmitter is the same as the path from the transmitter to the
DFS-equipped unlicensed device. However, for sharing with point-to-point
microwave systems, where the transmitter and receiver are typically
separated by tens of kilometers, the hidden transmitter problem can
exist.[^55] For sharing with point-to-point microwave systems,
geo-location CR techniques used with an on-line location database may be
more appropriate. Detection techniques such as DFS are also not very
effective when the licensed user's signal operates below the noise
floor, for example spread spectrum systems.

The Commission's proposal to permit higher-powered unlicensed device
operation when CR sensing techniques are employed includes three ISM
frequency bands: 902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz. NTIA
agrees with the Commission's current proposal to initially limit
higher-powered unlicensed device employing CR sensing techniques to the
902-928 MHz and 2400-2483.5 MHz bands. Because these frequency bands are
primarily used by unlicensed devices that must accept interference from
other unlicensed devices, compatibility analyses with government systems
are not necessary. However, in the 5725-5925 MHz frequency band, the DOD
operates fixed, transportable, and mobile radar systems and analyses
will have to be performed to assess the potential impact that the
Commission's proposal will have on these critical systems.

If the Commission is contemplating expanding the implementation of
higher-powered unlicensed device operations employing CR techniques,
NTIA recommends that the Commission consider the frequency bands
transferred from federal government to private sector use.[^56] The
transferred frequency bands represent spectrum that at this time has
limited government or commercial use. In an on-going rulemaking
proceeding, the Commission is already examining the implementation of CR
techniques in the 3650-3700 MHz band to facilitate sharing between
higher-powered unlicensed device and licensed radio services (radar
systems and satellite earth station receivers).[^57]

# SECONDARY SPECTRUM MARKET ACTIVITIES PROMISE TO INCREASE SPECTRUM EFFICENCY BY FOLLOWING CHANGING DEMAND. 

The Commission seeks comment on technical methods that might be used to
provide information necessary for leasing of spectrum and how a device
would enforce the terms of the lease. Specifically, the Commission
requests comment on whether they could reduce the uncertainties that may
inhibit leasing transactions by encouraging voluntary technical
standards for access to a licensee's spectrum. The Commission also
requests comments on what approaches to facilitate leasing transactions
could best achieve the goals of the flexible and market-driven policies
for spectrum leasing.[^58]

NTIA has, for several years, supported the development of secondary
markets as a means of promoting efficient use of spectrum.[^59] To
promote these secondary markets, it is important to maximize as much as
possible the flexibility for accommodating these markets. In permitting
secondary market activities, the Commission should not over-regulate the
leasing process or require secondary user registration or lessee
filings. NTIA advocates that licensees retain ultimate responsibility
for any activity under their lease. By making licensees responsible, the
Commission will have a mechanism for ensuring its rules are followed.
NTIA would suggest, however, that the Commission impose certain minimum
criteria for licensees to follow in entering into lease arrangements to
ensure appropriate intervention in the event of misuse by the lessee.
The Commission should require licensees to maintain on file the lease
agreement with availability to the Commission upon request; notify the
Commission upon agreement to a lease; maintain on file contact
information for any secondary users of their spectrum; have contractual
authority to terminate the lease in response to a violation; approve any
subsequent sublease; and assist in enforcement of the lease conditions
and administrative regulations.

Making the licensee responsible for any use within the scope of its
license will provide incentives for the licensee to construct the
appropriate covenants, indemnifications and limitations within its
contract to ensure appropriate use by the lessee. These basic principles
of minimum regulation of secondary markets should be extended to the
application of CRs to facilitate the establishment of secondary markets.

The Commission should consider permitting the deployment of beacon
signals and control and communication links that would aid CR systems to
identify spectrum that is available to the lessee. These beacon signals
and communication links would be restricted to the same spectral and
geographical constraints as those of the licensee. The Commission should
allow preemption of the lessee use of the spectrum by the licensee
subject to lease agreements. Licensees in cooperation with lessees
operating in the same or similar bands should also be encouraged to
develop voluntary standards for lessee equipment and operations as
required.

NTIA supports the actions taken by the Commission to remove regulatory
barriers to the development of secondary markets. These flexible
policies will continue the evolution toward greater reliance on the
marketplace to expand the scope of available wireless services. Because
CRs can play an enabling role in the establishment of secondary markets,
the development of CR technology should also have similar, minimum
regulatory constraints.

# HIGH-SPEED DIGITAL-TO-ANALOG CONVERTERS THAT ARE MARKETED AS PART OF RADIO SYSTEMS SHOULD BE REGULATED AS SOFTWARE DEFINED RADIOS OR COGNITIVE RADIOS UNDER THE APPROPRIATE SECTION OF THE COMMISSION'S RULES.

The Commission seeks comment on whether there is a need to restrict the
mass marketing of high-speed, digital-to-analog converters (DAC) that
could be diverted for use as radio transmitters and whether it can do so
without adversely affecting other uses of such computer peripherals or
the marketing of computer peripherals that cannot be misused.[^60]

DACs are finding increased use in modern communication systems and will
be a key element in the implementation of SDR and CR technologies. DAC
circuits can be used in local oscillators, clock generator blocks, and
wideband modulator circuits. The sources of spurious emissions generated
by DACs can generally be attributed to the nonlinearities associated
with the non-ideal static and dynamic transfer functions of the
DAC.[^61] Spurious emissions from the DAC can be categorized into three
types: spurious emissions caused by direct circuit nonlinearities within
the DAC; harmonically related spurious emissions caused by non-ideal
switching characteristics of the DAC; and spurious emissions caused by
noise coupling effects that can be harmonically or non-harmonically
related.[^62]

The marketing of high speed DACs and the software to make them interact
could undermine the Commission's present equipment authorization program
at the risk of increasing interference to legitimate spectrum users.
This could occur because these devices would not be subject to the
normal equipment authorization requirements. This is not presently a
problem, but the Commission is considering steps that can be implemented
now to help ensure that this scenario does not become a serious problem.

NTIA commends the Commission for addressing the potential problems of
emitters that could fall outside of the present regulatory structure as
part of this proceeding. The issue of the blurring of applicability of
specific rule sections as technology advances is but one indicator of
the problems facing the regulatory community in trying to keep pace with
technology evolution. While trying to avoid undue burden on the
introduction of innovative technology, the Commission clearly has the
responsibility to regulate spectrum use such that adverse effects to
other authorized users does not occur. The Commission has expressed
specific concern that high speed DACs might be used with high processing
speed personal computers to create software-controlled RF signal sources
that can be used as transmitters.

NTIA believes that there is no reason to regulate component parts such
as DAC integrated circuits and any regulation that would likely stifle
their use should be avoided. NTIA also believes that a radio transmitter
consists of a means to generate, amplify, and radiate a signal into the
environment. A DAC add in card alone does not possess this capability,
and thus should not be subject to regulation as a radio transmitter
under the Commission's rules. If a DAC is coupled with an amplifier and
antenna, with intent to radiate into the environment, then it should be
considered a SDR or CR and should be regulated under the applicable
section of the Commission's rules. NTIA recommends as potential consumer
applications of DAC based RF signal sources become better understood,
that the Commission should consider revisiting their regulations.

# THE COMMISSION SHOULD CONSIDER REQUIRING PROTECTION PROFILES AS PART OF THE EQUIPMENT CERTIFICATION PROCESS FOR SOFTWARE DEFINED RADIOS.

The Commission seeks comment on whether any modifications are necessary
to the security and authentication requirements in their rules.
Specifically, the Commission seeks comment on whether the current rules
provide adequate safeguards against unauthorized modifications to SDRs.
Comments are also sought on what should happen in the event that
reasonable security methods are ultimately broken and what
responsibilities do the manufacturers have if accepted industry
standards for security are followed.[^63]

The Commission's Rules require that manufacturers take steps to ensure
that only software that is part of an approved hardware/software
combination can be loaded onto an SDR.[^64] The software must not allow
the user to operate the transmitter with frequencies, output power,
modulation types or other parameters outside the range of those that
were approved. Manufacturers may use authentication codes or any other
means to meet these requirements, and must describe the methods in their
application for equipment authorization. In adopting these requirements,
the Commission stated that it may have to specify more detailed security
requirements at a later date as SDR technology develops.[^65]

NTIA shares the concerns raised by the Commission regarding the adequacy
of the current software security requirements. Recurring media reports
of security flaws in commercial software packages and operating systems
indicate that software based security mechanisms in SDR could be
vulnerable. Changes to the Commission's Rules that require the use of
specific industry standard security measures would help to remove some
ambiguity that exists in how security is implemented and how secure
these measures must be. To address problems with security, the SDR Forum
has written a document on the requirements for software downloads that
reconfigure the RF characteristics of a radio.[^66] This document
describes the security requirements for commercial wireless systems to
ensure that malicious code cannot be downloaded and activated. The
security measures are divided into six generic categories: Trusted
System Operator, Authentication, Authorization, Integrity, Privacy,
Non-Repudiation, and Auditing.[^67] All of these general security
requirements are also requirements for the more specific challenges of
SDR security. The SDR Forum has also developed security threat scenarios
and an SDR security threat model to address the different categories of
threats to downloaded software that reconfigures the RF parameters.[^68]

The SDR Forum is also considering Protection Profiles as a requirement
for SDRs. A Protection Profile is an implementation independent
statement of security requirements that is shown to address threats that
exist in a specified environment.[^69] A Protection Profile would be
appropriate for a consumer group that wishes to specify security
requirements for an application type. Protection Profiles are now
becoming a standard requirement for the Common Criteria, which is the
international mechanism for certification and accreditation of security
devices.[^70]

The main security issue that have been identified include who has the
authority to control the reconfiguration of the communications
equipment, protection of the reconfiguration signaling, privacy of the
reconfiguration information,[^71] the correctness and availability of
information on which the reconfiguration is based, and secure download
of software required for reconfiguration, and issues related to the
radio emission and associated conformance requirements of radio
equipment. NTIA is concerned about the regulatory implications
associated with downloaded software that can reconfigure the radio
functionality, which includes such parameters as frequency, power, and
modulation. The SDR Forum, which represents a large cross section of
national and international organizations, has made a great deal of
progress in addressing the areas of security, authentication, and
protection of unauthorized modifications to SDRs. NTIA understands the
Commission's reluctance to adopt specific security requirements because
this may constrain the development SDR technology. From the federal
agencies' perspective, however, NTIA believes that the acceptance of
SDR, and eventually CR technologies, hinges on assurances that the
operating parameters that can impact electromagnetic compatibility with
other systems are protected from malicious attacks. NTIA recommends that
as a long-term goal of addressing security issues related to SDR and CR
technologies, the Commission consider requiring Protection Profiles as
part of the equipment certification.

# THE REQUIREMENT FOR APPLICANTS TO PROVIDE A COPY OF THEIR SOFTWARE AS PART OF THE CERTIFICATION PROCESS FOR SOFTWARE DEFINED RADIOS SHOULD BE ELIMINATED.

The Commission proposes to delete the requirement that applicants supply
a copy of their radio software upon request. In its place the Commission
proposes to add a less burdensome requirement that applicants supply a
description and flow diagram of the software that controls the radio
operating parameters.[^72]

NTIA agrees with the Commission that examination of software is not an
effective means of identifying where unauthorized software changes have
been made in an SDR. NTIA believes that the Commission's requirement
that certified devices must comply with their applicable technical rules
is sufficient to safeguard against unauthorized equipment modifications.
Thus, NTIA agrees with the Commission's proposal to eliminate the
existing requirement for applicants to provide copies of their software
as part of the certification process for SDRs.

# MANUFACTURERS SHOULD ONLY BE REQUIRED TO DECLARE THEIR DEVICES AS A SOFTWARE DEFINED RADIO IF THE DEVICE IS REMOTELY PROGRAMMABLE AND HAS HARDWARE CAPABLE OF TRANSMITTING IN THE RESTRICTED FREQUENCY BANDS OR IN FREQUENCY BANDS ALLOCATED TO THE FEDERAL GOVERNMENT ON AN EXCLUSIVE BASIS.

The Commission requests comments on the need for a requirement that
manufacturers declare certain equipment as SDRs, including the benefits
of such a requirement in reducing interference and its possible burden
on manufacturers. Specifically, the Commission seeks comment on the type
of device to which this requirement should apply, including how the
rules should distinguish between transmitters that must be identified as
SDRs.[^73]

NTIA agrees with the concerns raised by the Commission regarding an
SDR's ability to modify its parameters. Operating outside of the
parameters approved under the rules for that device, would increase the
potential for interference to other authorized radio services.[^74]
Issues related to unauthorized users having the capability to modify or
reprogram an SDR to operate outside of its allowable parameters
continues to be a concern to many of the federal agencies. Requiring
manufacturers to declare a device as being an SDR would require that the
security mechanisms must be incorporated, which provides some assurance
that unauthorized users cannot modify the parameters of SDRs. This would
reduce the interference risk to other radio services.

The definition for SDR adopted by the Commission is extremely broad and
covers devices in which parameters such as frequency and modulation type
are determined by software.[^75] The problem is that the definition of
SDR could also apply to non-government private land mobile radios and
most commercial PCS base stations, which were not intended to be
included under the rules for SDR. The Commission's current rules do not
require manufacturers of SDRs to declare them as such when applying for
equipment authorization. A device that is not declared as an SDR does
not have to comply with the software security requirements that are
designed to ensure that only authorized software can be loaded.[^76]
NTIA recognizes the potential problem that can be encountered by
applying the broad definition for SDR. However, there is still a
potential problem with an SDR whose transmitter parameters can be
changed remotely. In this situation, large numbers of transmitters could
be modified simultaneously, thereby increasing the potential
interference to federal spectrum users.

NTIA believes that the primary concern to federal operations would come
from SDRs that are remotely programmable and have the hardware
capability to transmit in the restricted frequency bands or in other
frequency bands used by the federal government. NTIA believes that it
would be appropriate for the Commission to require manufacturers to
declare their devices as SDRs if the device is remotely programmable and
has hardware that is capable of transmitting in the restricted frequency
bands or in frequency bands allocated to the federal government on an
exclusive basis. This would eliminate the problems associated with
incorrectly classifying commercial devices, such as land mobile radio
and PCS, as SDRs and provide protection to federal users.

# TECHNICAL ISSUES RELATED TO THE COMPLIANCE MEASUREMENTS OF UNLICENSED DEVICES THAT EMPLOY COGNITIVE RADIO TECHNIQUES MUST BE ADDRESSED PRIOR TO IMPLEMENTATION.

Since devices employing CR techniques can perform functions not
envisioned at the time the current Part 15 Rules were developed, the
Commission recognizes that it will be necessary to specify additional
compliance measurement procedures. In the NPRM, the Commission proposes
a number of specific tests applicable to the following CR techniques:
interruptible radio,[^77] listen-before talk,[^78] and
geo-location.[^79] The Commission seeks comment on its proposed
compliance measurement tests and whether additional tests might be
necessary. The Commission also solicits public comment on whether it or
an industry standards organization, such as the American National
Standards Institute (ANSI), should develop the compliance measurement
procedures.[^80]

Currently, when Part 15 devices are certified, the output of the device
is tested in response to a single or limited number of input conditions
to verify that it complies with the Commission's Rules. However, for
unlicensed devices employing CR techniques, it will be necessary to test
the output in response to various inputs or various combinations of
inputs. NTIA is currently participating in a government/industry working
group that is developing compliance measurement guidelines for U-NII
devices that are equipped with DFS.[^81] In this case, the compliance
measurements must verify the DFS detection threshold, startup and
in-service monitoring times, the time to cease transmissions or move to
another channel, and the time to revisit a portion of the spectrum to
determine whether it is unoccupied.[^82] Even with this relatively
simple implementation of a CR technique, developing compliance
measurement procedures has proven to be challenging. These procedures
must be such that they can be reasonably implemented by the
Telecommunication Certification Bodies (TCBs). Furthermore, the
procedures need to be comprehensive enough to ensure that the DFS
capability adequately protects the radar systems.

NTIA agrees with many of the tests proposed by the Commission in the
NPRM for listen-before-talk or sensing CR techniques. However, NTIA
believes that there are additional factors that must be included in the
compliance measurement procedures. For example, depending on how the
listen-before-talk or sensing capability is implemented and the type of
data transmissions, the channel loading could have an impact on the
compliance measurements. If the listen-before-talk or sensing CR
techniques are implemented so that a dedicated period of time is
established for spectrum monitoring, the channel loading is not as
critical. However, if the spectrum monitoring is performed during the
quiet periods between data packet transmissions, the channel loading
becomes more critical. This is particularly true if the signal that is
to be detected has time-varying characteristics, such as a radar system
with an antenna that scans 360 degrees in azimuth. In this situation,
the detection process depends on the packet size of the data
transmissions. To simulate the channel loading, standard data files
should be developed.[^83] For Internet Protocol-based systems that
employ a variable packet length based on the file being transmitted, it
should be sufficient to stream a file that will load the system to 40 to
60 percent of its throughput capability. For frame-based systems that
employ fixed packet lengths, but vary the transmit/listen time, the
transmit/listen ratios should be set to a value that represents the
setting used during actual system deployment. Additional parameters that
need to be defined for measuring the detection level including whether
the measurement is based on peak and/or average power and the
measurement interval.[^84]

For listen-before-talk and sensing CR techniques to be effective, the
test signals used in the compliance measurements must be representative
of the signals employed by the licensed radio service in the frequency
band that is being monitored. The DFS-equipped U-NII devices are sharing
with the radiolocation service, so the test signals are defined by
representative radar characteristics such as pulse repetition frequency,
pulse width, burst length, burst period, and hopping rate (for frequency
hopping radar systems).[^85] In frequency bands in which the
characteristics of the licensed service are known and not subject to
change (*e.g.*, broadcast signals), it may be possible to use these
characteristics to assist in signal detection. However, when detecting
signals in bands where the characteristics of the licensed service vary
over a wide range or can change because of future system developments,
the detection should be based solely on received power level exceeding a
specified threshold. The actual detection threshold will vary depending
on the characteristics of the licensed radio service and the unlicensed
device application as well as the operational scenario. The compliance
measurements must verify that the signal detection is based on received
power level in these situations.

The Commission also identified tests to be included in the compliance
measurements for unlicensed devices that employ geo-location techniques.
These tests address the ability of the device to correctly identify its
location, the ability to access an on-line database of other authorized
systems, and the unlicensed device response when the position location
is lost. NTIA agrees with the Commission's proposal and recommends an
additional test to verify what corrective action will be taken (*e.g.*,
cease transmitting, reduce power, move to another frequency) when it is
determined that the unlicensed device is within the exclusion areas
around the fixed site locations in the on-line database.

NTIA believes that the compliance measurement procedures for devices
employing CR techniques need to be developed in an open forum, where
private and government entities can participate. This approach is being
employed by the government/industry working group, chaired by NTIA, that
is addressing the compliance measurement procedures for DFS-equipped
U-NII devices operating at 5 GHz. These working group meetings are open
to the public and include participants from NTIA, the FCC, the DOD,
manufacturers, and the TCBs. This working group has been successful in
developing consensus positions that are used to provide guidance to the
Commission. The Commission suggests ANSI as a possible organization for
developing the compliance measurement procedures. NTIA believes the SDR
Forum is another possible organization that can be used to develop
compliance measurement procedures for devices employing CR techniques.
The SDR Forum meetings are open to the public and have participation
from both the private sector and the government.

In the past, because of their simplicity, the compliance measurement
procedures for unlicensed devices were typically considered after the
development of the service rules. However, given that CR devices can
change their electromagnetic characteristics on a near real-time basis,
compliance measurements will be more complex. NTIA believes that the
compliance measurements are a critical element in ensuring that
unlicensed devices employing CR techniques do not interfere with
authorized spectrum users. The TCBs are experts in the area of
performing the compliance measurements and need to be actively engaged
in providing guidance on the technical issues related to device
certification for unlicensed devices employing CR techniques. NTIA
believes that technological approaches that cannot be verified in the
TCB laboratories should not be relied upon for successful spectrum
sharing. NTIA recommends that the Commission resolve all of the
technical issues related to performing the compliance measurements prior
to implementing CR techniques in any frequency band.

# A NEW SUBPART UNDER PART 15 OF THE COMMISSION'S RULES SHOULD BE ESTABLISHED FOR UNLICENSED DEVICES EMPLOYING COGNITIVE RADIO TECHNIQUES.

The ability of CR technologies to adapt a radio's use of the spectrum to
the real-time conditions of the operating environment offers regulators,
licensees, government agencies, and the public the potential for more
flexible, efficient, and comprehensive use of the available RF spectrum.
Nevertheless, CR technologies could raise new interference issues that
will have to be addressed. Furthermore, unlike conventional unlicensed
devices, the compliance measurements for devices employing CR
technologies will be much more complicated and will have a greater
impact on whether or not a device is compatible with other spectrum
users. The NPRM does not address how unlicensed devices that employ CR
technologies should be accommodated under the current Part 15 Rules.
NTIA recommends that a new subpart within the Commission's Part 15 Rules
be established for unlicensed devices that employ CR techniques. This is
similar to the approach that was used for unlicensed UWB devices, which
also did not fit into the existing Part 15 Rules.

The Commission has adopted a definition for SDRs. NTIA recommends that
the Commission consider adopting the following definition for CR:

> *Cognitive radio: A radio or system that senses its operational
> electromagnetic environment and can dynamically and autonomously
> adjust its radio operating parameters to modify system operation, such
> as maximize throughput, mitigate interference, facilitate
> interoperability, access secondary markets.*

NTIA believes that the Commission should adopt a definition for CR in
order to provide regulatory certainty to manufacturers seeking industry
investment in these new technologies.

# UNLICENSED DEVICES CAPABLE OF OPERATING ON NON-PART 15 FREQUENCIES MUST INCORPORATE FREQUENCY SENSING OR GEO-LOCATIOIN CAPABILITIES.

The Commission proposes to allow certification of Part 15 devices that
are capable of operating on non-Part 15 frequencies. As part of this
proposal, the Commission would require that such devices incorporate DFS
to select the appropriate operating frequency based on the country of
operation.[^86] The Commission also proposes that these devices must
incorporate a means to determine the country of operation.[^87] The
Commission seeks comment on these proposals.

Many of the frequency bands where unlicensed device operation is
permitted are not harmonized on a worldwide basis. For example, the
902-928 MHz band is limited to the United States in most cases. With the
Commission's recent action in the U-NII proceeding additional spectrum
in the 5 GHz bands, unlicensed devices operating on the U.S. channels
will be using the same frequency bands as most of the world. However, in
the United States, unlicensed device operation is permitted in the
2400-2483.5 MHz as opposed to the 2400-2500 MHz band used by most
countries.[^88] The ability to certify unlicensed devices that could be
used on a worldwide basis, or at least in a number of different
countries, would eliminate the need for manufacturers to produce
multiple versions of a device for use in different countries.

Unlicensed devices can fall into two general categories: devices that
are under the control of a central controller (e.g., access point); and
devices that are capable of operating without a central control (e.g.,
peer-to-peer operation). NTIA recognizes the potential benefits of
allowing manufacturers to produce one device that can be enabled on a
country specific basis to transmit in the authorized spectrum bands of
that country. However, the proposal to require DFS technology to be
embedded into unlicensed devices capable of operating outside of the
Part 15 frequency bands is unnecessary since DFS only looks for an open
frequency and has no ability to recognize where it is located. Passive
sensing is possible in the case where the central controller is capable
of supplying the frequency selection information to the devices, for
example, as specified in IEEE 802.11 Task Group (TG)d. However, this
does not address devices that can operate without a central controller
and it also assumes that the central controller is set to only access
frequencies authorized for use in the United States.

If the Commission adopts its proposal to certify unlicensed devices that
are capable of using non-Part 15 frequencies, then it should limit this
to devices where the central controllers can control the transmit
frequencies of the client devices. As part of the device certification
process, it is imperative that it be ensured that the central
controllers can only operate in the bands authorized for Part 15
operations. For unlicensed devices that operate without a central
controller, the device should be required to incorporate geo-location
capabilities, such as GPS, in conjunction with a database, to determine
its geographic location. The location information would then be used to
control the authorized frequencies that the unlicensed device can use.
Furthermore, if the unlicensed device is not capable of determining its
geographic location, the device must be restricted from transmitting.

# CONCLUSION

NTIA commends the Commission for initiating this proceeding examining CR
technology. NTIA agrees with the Commission regarding the significant
benefits that could be gained by employing CR technologies. The NPRM
identifies several areas where technical and regulatory issues must be
addressed. NTIA supports the Commission's approach, whereby the initial
implementation of CR technologies is limited to a few frequency bands
primarily used by unlicensed devices. NTIA believes that the experience
gained in these frequency bands will help facilitate a much broader
implementation of CR technologies while ensuring that existing
government and non-government spectrum users are adequately protected
from interference. NTIA will continue to work with the Commission and
industry to resolve the technical and regulatory issues surrounding the
successful implementation of CR technologies.

For the foregoing reasons, NTIA submits these comments

Respectfully submitted,

Michael D. Gallagher Kathy D. Smith

Assistant Secretary for Chief Counsel

Communications and Information

Fredrick R. Wentland

Associate Administrator

Office of Spectrum Management

Edward Drocella

Mark Settle

Electronics Engineers

Office of Spectrum Management

National Telecommunications

and Information Administration

U.S. Department of Commerce

Room 4713

1401 Constitution Avenue, N.W.

Washington, DC 20230

> \(202\) 482-1816

February 15, 2005

[^1]: . *Facilitating Opportunities for Flexible, Efficient, and
    Reliable Spectrum Use Employing Cognitive Radio Technologies*,
    Notice of Proposed Rulemaking, ET Docket No. 03-108, 18 F.C.C. Rcd.
    26859 (2003) ("Cognitive Radio NPRM").

[^2]: . Cognitive Radio NPRM at ¶ 22.

[^3]: . XG Working Group, *The XG Vision*, Request for Comments, Version
    2.0, BBN Technologies, Cambridge Massachusetts. This document and
    other information about the DARPA XG program are available at
    <http://www.darpa.mil/ato/programs/xg/rfc_vision.pdf>

[^4]: . National Science Foundation, Directorate for Computer and
    Information Science Engineering, Division of Computer and Network
    Systems, Research in Networking Technology and Systems (NeTS). More
    information on the NeTS program is available at
    [http://www.cise.nsf.gov](http://www.cise.nsf/).

[^5]: . Federal Aviation Administration, *Radio Spectrum Plan*, at
    Section 1.7 (January 26, 2004).

[^6]: . Cognitive Radio NPRM at ¶ 31.

[^7]: . Recommendation ITU-R RA.769-1, *Protection Criteria Used for
    Radioastronomical Measurements* (1992-1995).

[^8]: . In the NPRM, the Commission describes cyclostationary detectors
    or feature detectors, which use longer sensing times and internal
    computation to achieve signal sensitivities below the noise level
    for signals of known format. Cognitive Radio NPRM at ¶ 25. However,
    the practical capabilities and limitations of these detectors need
    to be studied and demonstrated to determine whether or not they can
    contribute significantly to the implementation of CR sensing
    techniques.

[^9]: . Cognitive Radio NPRM at ¶ 38.

[^10]: . *Id.* at ¶ 39.

[^11]: . *Id.* at ¶ 43.

[^12]: . The frequency bands from 5250-5925 MHz are allocated on a
    primary basis to Government radiolocation.

[^13]: . Cognitive Radio NPRM at ¶ 43.

[^14]: . *Id.* at ¶ 44.

[^15]: . *Id.*

[^16]: . DFS is a mechanism that dynamically detects signals from other
    systems and avoids co-channel operation with these systems.

[^17]: . *Revision of Parts 2 and 15 of the Commission's Rules to Permit
    Unlicensed National Information Infrastructure (U-NII) Devices in
    the 5 GHz Band*, Report and Order, ET Docket No. 03-122, 18 F.C.C.
    Rcd. 24484 (2003) ("U-NII R&O").

[^18]: . Cognitive Radio NPRM at ¶ 38. A power level of 6 watts is
    proposed in the 5725-5850 MHz band and 125 millivolts per meter at a
    distance of 3 meters in the 5725-5875 MHz band.

[^19]: . *Id.* at ¶ 44. The detection threshold is specified as 30 dB
    above the calculated thermal noise floor within a measurement
    bandwidth of 1.25 MHz. The thermal noise floor of a 1.25 MHz
    bandwidth receiver is -113 dBm. The detection threshold proposed by
    the Commission is 30 dB above -113 dBm or -83 dBm.

[^20]: . The Monte Carlo method has been used for the simulation of
    random processes and is based upon the principle of taking samples
    of random variables from their assumed probability density
    functions.

[^21]: . For DFS-equipped U-NII devices, these parameters are defined in
    Section 15.403 of the Commission's Rules.

[^22]: . The values for the DFS detection threshold and the additional
    parameters are provided in Section 15.407(h)(2) of the Commission's
    Rules.

[^23]: . Cognitive Radio NPRM at ¶ 42.

[^24]: . *Id.*

[^25]: . The power levels of the spurious emissions in many cases are
    statistical in nature, where the peak levels can vary with time and
    frequency. Harmonic emissions are more difficult to eliminate, but
    at non-harmonically related frequencies the levels are also believed
    to be well below the limits specified in the Commission's Rules.

[^26]: . Cognitive Radio NPRM at ¶ 47.

[^27]: . *Revision of the Commission's Rules to Ensure Compatibility
    with Enhanced 911 Emergency Calling Systems*, Third Report and
    Order, CC Docket No. 94-102, 14 F.C.C. Rcd. 17388 (1999).

[^28]: . Federal Communications Commission, OET Bulletin No. 71*,
    Guidelines for Testing and Verifying the Accuracy of Wireless E911
    Location Systems* (April 12, 2000).

[^29]: . Institute of Electrical and Electronics Engineers Comments, ET
    Docket No. 02-380, at 10 (April 17, 2003).

[^30]: . The exclusion areas where unlicensed device operation is
    prohibited would be determined based on the characteristics and
    operational scenarios for the licensed service and the unlicensed
    devices.

[^31]: . A minimum of three to four satellites are necessary for a GPS
    receiver to determine a position location.

[^32]: . Cognitive Radio NPRM at ¶ 76.

[^33]: . Public Safety Wireless Advisory Committee, *Final Report of the
    Public Safety Wireless Advisory Committee to the Federal
    Communications Commission*, Reed E. Hundt, Chairman, Federal
    Communications Commission and Larry Irving, Assistant Secretary of
    Commerce for Communications and Information, at 547 (September 1996)
    ("PSWAC Final Report").

[^34]: . The SAFECOM Program, Department of Homeland Security,
    *Statement of Requirements for Public Safety Wireless Communications
    and Interoperability Version 1* (March 10, 2004). SAFECOM was
    established to serve as the umbrella program within the federal
    government to help local, tribal, state, and federal public safety
    agencies improve public safety response through more effective and
    efficient interoperable wireless communications.

[^35]: . National Institute of Justice Journal*, Can We Talk? Public
    Safety and Interoperability Challenge*, at 18 (April 2000).

[^36]: . Air-interface is a radio-to-radio signal path defined in terms
    of access method, modulation scheme, voice-coding method, channel
    rate, and channel data format.

[^37]: . A waveform is the software package that defines the air
    interface and protocols necessary to enable communications using a
    particular technology. Project 25 Phase I, M/A-COM, EDACS, and
    Motorola SmartNet are all examples of waveforms that could be
    supported on an SDR platform.

[^38]: . The MBITR operates in the 30-512 MHz frequency range and
    supports amplitude and frequency modulation.

[^39]: . The Universal Communicator operates in the 100 to 475 MHz
    frequency range and can interoperate with multiple radio systems by
    touching various icons on the screen. It is configured to support
    analog frequency modulation and the Project 25 digital standard.

[^40]: . The SDR Forum is an international, non-profit organization
    dedicated to promoting the development, deployment, and use of SDR
    technologies.

[^41]: . The special interest group is charged with involving vendors
    and public safety organizations in the SDR forum's initiatives to
    promote development of SDR technologies.

[^42]: . Mobile Radio Technology, *Software Defined Radio: The
    interoperability solution*?, at 40 (November 2003) ("MRT Magazine
    Article").

[^43]: . PSWAC Final Report at 239.

[^44]: . MRT Magazine Article at 40.

[^45]: . Cognitive Radio NPRM at ¶ 77.

[^46]: . *Id.* at ¶ 79.

[^47]: . *Id.* at ¶ 80.

[^48]: . Cognitive Radio NPRM at ¶ 94.

[^49]: . Geo Intelligence, *GPS-Based Geo Encryption*, at 26 (Winter
    2003).

[^50]: . Cognitive Radio NPRM at ¶ 41.

[^51]: . In the restricted frequency bands, only spurious and
    unintentional emissions from unlicensed devices are permitted.

[^52]: . The Terminal Doppler Weather Radar provides quantitative
    measurements of gusts fronts, wind shear, microbursts, and other
    weather hazards for improving the safety operations at major
    airports.

[^53]: . The Intelligent Transportation System Dedicated Short Range
    Communication Service is used to support public safety
    communications on the Nation's highways.

[^54]: . Fixed point-to-point microwave systems are used by public
    safety, railroads, and the energy and water industries.

[^55]: . In the hidden transmitter problem, if a spectrum sensing
    equipped unlicensed device is blocked from receiving the transmitted
    point-to-point signal (*e.g*., shielded by local terrain features)
    it will be permitted to transmit, possibly causing interference to
    the point-to-point receiver that is located close to the spectrum
    sensing equipped unlicensed device.

[^56]: . In accordance with the requirements of Title VI of the Omnibus
    Budget Reconciliation Act of 1993 and the Balanced Budget Act of
    1997, 247 MHz of federal government spectrum have been identified
    for transfer to the private sector.

[^57]: . *Additional Spectrum for Unlicensed Services Below 900 MHz and
    in the 3 GHz Band*; *Amendment of the Commission's Rules with Regard
    to the 3650-3700 MHz Government Transfer Band*, Notice of Proposed
    Rulemaking, ET Docket No. 04-151, ET Docket No. 02-380, ET Docket
    No. 98-237, FCC 04-100, 2004 FCC LEXIS 2071, at ¶¶ 64-68 (2004).

[^58]: . Cognitive Radio NPRM at ¶ 50.

[^59]: . Letter from Nancy J. Victory, Assistant Secretary for
    Communications and Information, National Telecommunications and
    Information Administration, to the Honorable Michael K. Powell,
    Chairman, Federal Communications Commission (March 7, 2002).

[^60]: . Cognitive Radio NPRM at ¶ 92.

[^61]: . RF Design, *Sources of Spurious Components in a DDS/DAC
    System,* at 28 (April 1998).

[^62]: . *Id.*

[^63]: . Cognitive Radio NPRM at ¶ 94.

[^64]: . *See* 47 C.F.R. § 2.932(e).

[^65]: . *Inquiry Regarding Software Defined Radios*, Report and Order,
    ET Docket No. 00-47, 16 FCC Rcd 17373, 13383 (2001).

[^66]: . SDR Forum, Document Number SDRF-02-A-007-C0.00, *Requirements
    for Radio Software Download for RF Reconfiguration* (November 13,
    2002).

[^67]: . *Id.* at 29.

[^68]: . *Id.* at Appendix A.

[^69]: . Protection Profiles are registered through national processes.

[^70]: . More information is available at
    <http://www.commoncriteria.org/protection_profiles/pp.html>.

[^71]: . For example, information on current configuration of a user's
    equipment.

[^72]: . Cognitive Radio NPRM at ¶ 86.

[^73]: . Cognitive Radio NPRM at ¶ 88.

[^74]: . *Id.* at ¶ 87.

[^75]: . A software defined radio is one that includes a transmitter in
    which the operating parameters of frequency range, modulation type
    or maximum output power (either radiated or conducted) can be
    altered by making a change in software without making any changes to
    hardware components that affect the radio frequency emissions.

[^76]: . The manufacturers of SDR devices are now required under Section
    2.932(e) of the Commission's Rules to take steps to ensure that only
    software that has been approved with a SDR can be loaded into such a
    radio.

[^77]: . Cognitive Radio NPRM at ¶ 103.

[^78]: . *Id.* at ¶ 105.

[^79]: . *Id.* at ¶ 106.

[^80]: . *Id.* at ¶ 102.

[^81]: . DFS is the same as the sensing or listen-before-talk techniques
    described in the NPRM.

[^82]: . U-NII R&O at Appendix C.

[^83]: . A standard Moving Picture Experts Group-2 (MPEG-2) file could
    be used for the channel loading depending on the device application.

[^84]: . For DFS-equipped U-NII devices, detection is based on a maximum
    power level averaged over a 1 microsecond time period.

[^85]: . U-NII R&O at Appendix C-13.

[^86]: . Cognitive Radio NPRM at ¶ 97.

[^87]: . *Id.*

[^88]: . Channels 12 and 13 (2467 MHz and 2472 MHz) of the IEEE 802.11
    b/g standard are not used in most cases to avoid problems with
    out-of-band emissions in the restricted frequency band 2483.5-2500
    MHz which is used by the mobile satellite service in the United
    States.