Subject: [NEXTEL-1] NTIA Comments ET Docket No. 02-380 -- 05-07-2003.html

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Before the

FEDERAL COMMUNICATIONS COMMISSION

Washington, DC 20554

In the Matter of

)

)

Additional Spectrum for Unlicensed Devices
) ET Docket No. 02-380

Below 900 MHz and in 3 GHz band
)

COMMENTS OF THE NATIONAL TELECOMMUNICATIONS

AND INFORMATION ADMINISTRATION

Nancy J. Victory
Kathy D. Smith

Assistant Secretary for
Chief Counsel

Communications and Information

Frederick R. Wentland

Acting Associate Administrator

Office of Spectrum Management

Gerald F. Hurt

Edward F. Drocella

Ernesto A. Cerezo

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

May 7, 2003

TABLE OF CONTENTS

Section

EXECUTIVE SUMMARY . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I. INTRODUCTION . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . .

II. UNLICENSED DEVICE OPERATIONS SHOULD NOT BE

PERMITTED IN THE 608-614 MHz BAND . . . . . . . . . . . . . . . . . .
. . . . . .

III. THE EMISSION LIMIT FOR UNLICENSED DEVICES

OPERATING IN THE TELEVISION BROADCAST FREQUENCY

BANDS SHOULD INCLUDE A PROVISION FOR HARMONICS

THAT ARE GENERATED IN THE 1559-1610 MHz

RADIONAVIGATION SATELLITE SEVICE BAND . . . . . . . . . . . . . . . .
.

IV. UNLICENSED DEVICE OPERATIONS THAT EMPLOY

INTERFERENCE MITIGATION TECHNIQUES CAN

FACILITATE SHARING WITH FEDERAL RADARS IN

THE 3650-3700 MHz BAND . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . .

V. SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . .

EXECUTIVE
SUMMARY

The National Telecommunications and Information Administration
(NTIA) commends the Federal Communications Commission (Commission) for
initiating this proceeding to expand the options for unlicensed device
use, and particularly, linking such expanded use to adoption of new
technologies for active interference-avoidance. NTIA agrees with the
Commission regarding the significant benefits to the economy,
businesses, consumers, and government agencies that could be gained by
allowing unlicensed devices to operate in other bands at power levels
higher than those currently permitted, provided that such operation is
tied to effective implementation of active interference-avoidance
techniques. However, NTIA is concerned with the potential impact that
the expansion of unlicensed devices at higher power levels may have on
critical Federal systems used for scientific research, aviation, and
national defense.

NTIA agrees with the Commission that unlicensed device operation in
the 608-614 MHz band would not be appropriate because of the
interference concerns associated with the sensitive nature of radio
astronomy reception and the critical function of Wireless Medical
Telemetry Service (WMTS) equipment in the band. As such, NTIA strongly
recommends that the Commission prohibit unlicensed device operations in
the 608-614 MHz band. Furthermore, to protect radio astronomy
reception and WMTS equipment, NTIA also recommends that emissions in
the 608-614 MHz band from unlicensed devices operating in adjacent
bands be limited in accordance with Subsection 15.205 of the
Commission's Rules, 47 C.F.R. §15.205.

In exploring the authorization of unlicensed devices in the
television broadcast frequency bands, the Commission should recognize
and address the effect of harmonics of such use on critical systems in
other bands. Specifically, coarse/acquisition code receivers of the
Global Positioning System L1 operating in the 1559-1610 MHz band are
very susceptible to narrowband interfering signals. NTIA strongly
recommends that the emission limits developed for the unlicensed
devices permitted to operate in the television broadcast bands include
a provision for harmonic signals that may be generated in the 1559-1610
MHz radionavigation satellite service band.

Finally, NTIA supports the Commission's efforts to permit the
operation of unlicensed devices in the 3650-3700 MHz band, including
the possible relaxation of restrictions on the operating
characteristics of the unlicensed devices to allow higher power and
antenna gains than the maximum levels currently permitted for such
devices. However, in order to ensure that Federal operations in the
3650-3700 MHz band are not adversely impacted, NTIA recommends that any
relaxation of the restrictions on power level and antenna gain be tied
to the mandatory adoption of effective frequency and/or geographic
avoidance technologies, as suggested by the Commission. NTIA
recommends that a project team be formed to examine the merits of the
proposed interference-mitigation techniques and to develop the
recommended technical requirements to allow compatible unlicensed
device usage in the 3650-3700 MHz band.

COMMENTS OF THE NATIONAL TELECOMMUNICATIONS

AND INFORMATION ADMINISTRATION

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, 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 Inquiry
(NOI) in the above-captioned proceeding.(1)

I. INTRODUCTION

In this NOI, the Commission seeks
comments on the feasibility of allowing unlicensed devices to operate
in additional frequency bands. Specifically, the Commission seeks
comments on allowing unlicensed devices to operate in the television
(TV) broadcast spectrum at locations and times when spectrum is not
being used, and on the technical requirements that would be necessary
to ensure that such devices do not cause interference to authorized
services operating within the TV broadcast bands. In addition, the
Commission seeks comments on the feasibility of permitting unlicensed
devices to operate in other bands, such as the 3650-3700 MHz band, at
power levels significantly higher than the maximum levels currently
authorized for unlicensed devices in other frequency bands with only
minimal technical requirements.

NTIA commends the Commission for
initiating this proceeding to expand the options for unlicensed use,
and particularly, linking such expanded use to adoption of new
technologies for active interference-avoidance. NTIA agrees with the
Commission regarding the significant benefits to the economy,
businesses, consumers, and government agencies that could be gained by
allowing unlicensed devices to operate in other bands at power levels
higher than those currently permitted, provided that such use is tied
to effective implementation of active interference-avoidance
techniques. However, NTIA is concerned with the potential impact that
the expansion of unlicensed devices at higher power levels may have on
critical Federal systems. Accordingly, NTIA provides comments to this
NOI in three areas: unlicensed device operations in the 608-614 MHz
band used for Federal scientific observations; potential interference to
receivers operating in the 1559-1610 MHz radionavigation satellite
service band used for aviation and safety related applications; and
unlicensed device operations in the 3650-3700 MHz band used to support
military radiolocation operations.

II. UNLICENSED DEVICE OPERATIONS
SHOULD NOT BE PERMITTED IN THE 608-614 MHz BAND.

The 608-614 MHz band is used by Federal radio
astronomers for Very Long Baseline Interferometry (VLBI), which links
radio telescopes together across long distances. Scientists use VLBI
to study continental drift, rotation of the Earth, earthquakes, and
space navigation. The National Radio Astronomy Observatory (NRAO)
operates the VLBI Array of telescopes at ten sites in the United States
and its territories that use the 608-614 MHz band. To make VLBI
continuum measurements, data from the antennas are combined
synthesizing a single telescope 5000 miles in diameter.(2)

In order for these continuum observations to be useful,
it is essential that background noise in the 608-614 MHz band remains
limited.

The 608-614 MHz band is also one of the three bands allocated to
the Wireless Medical Telemetry Service (WMTS). WMTS equipment is
permitted only in health care facilities and eligibility to operate
such equipment is strictly limited to health care personnel. Frequency
coordination is required by Commission-selected entities that record
and monitor the locations and frequencies of WMTS equipment for
interference-control purposes.

NTIA agrees with the Commission that unlicensed device operation in
the 608-614 MHz band would not be appropriate because of the
interference concerns associated with the sensitive nature of radio
astronomy reception and the critical safety function of WMTS equipment.(3)

The current sharing relationship between radio astronomy and WMTS is
successful because of the required coordination process. It is not
possible to coordinate unlicensed device operations, thus increasing
the potential for interference to radio astronomy continuum
observations. NTIA therefore recommends that the Commission prohibit
unlicensed device operations in the 608-614 MHz band. Furthermore, to
protect sensitive scientific and medical equipment, NTIA recommends
that emissions in the 608-614 MHz band from unlicensed devices operating
in adjacent bands be limited in accordance with Subsection 15.205 of
the Commission's Rules, 47 C.F.R. §15.205.

III. THE EMISSION LIMITS FOR UNLICENSED DEVICES OPERATING
IN THE TELEVISION BROADCAST FREQUENCY BANDS SHOULD INCLUDE A PROVISION
FOR HARMONICS THAT ARE GENERATED IN THE 1559-1610 MHz RADIONAVIGATION
SATELLITE SERVICE BAND.

The Commission also seeks comments on the feasibility of permitting
unlicensed devices to operate in the TV broadcast frequency bands.(4)

The TV broadcast bands refer to the 402 MHz of spectrum allocated to
the broadcast services at 54-72 MHz, 76-88 MHz, 174-216 MHz, 470-608
MHz, and 614-806 MHz. One of the most common undesirable effects of
non-linearity in communications systems is the generation of harmonics.
Aside from interfering signals whose fundamental frequencies(5) may fall into the passband(6) of a receiver, harmonics of out-of-band
signals may also fall into the receiver passband.(7)

Depending upon the transmit frequency, unlicensed
devices that operate in the TV bands may have harmonic signals that
fall within the radionavigation satellite service (RNSS) band of
1559-1610 MHz.

The RNSS systems operating in the 1559-1610 MHz band include the
Global Positioning System (GPS) L1 signal operating in the
1563.42-1587.42 MHz segment of the band and the Russian Federation
Global Navigation Satellite System (GLONASS) operating in the 1598-1605
MHz segment of the band. GPS and GLONASS are components of the Global
Navigation Satellite System (GNSS).(8)

The European Union is also planning to operate an RNSS system,
Galileo, in the 1559-1610 MHz band. It is envisioned that Galileo will
also become a component of the GNSS. Table 1 gives the relationship
between the TV channel number and the harmonic of the carrier that
falls nearest to the GPS and GLONASS signals. For example, TV channel
23 has a frequency assignment of 525.25 MHz. The third harmonic of
this frequency is 1575.42 MHz, which is the center frequency of the GPS
L1 signal.

TABLE 1

PROXIMITY OF TV BAND CARRIER HARMONICS TO GPS

AND GLONASS CARRIERS

Channel Number

Frequency Allocation

(MHz)

Harmonic Number

6

82-88

19

7

174-180

9

10

192-198

8

11

198-204

8

22

518-525

3

23

524-530

3

24

530-536

3

66

782-788

2

67

788-794

2

Harmonics are in many instances narrowband signals. GPS receivers
using the L1 coarse/acquisition (C/A) code are known to be susceptible
to narrowband interference primarily because of the relatively short
period of the C/A code.(9)

With a period of 1 millisecond, the C/A
code spectrum is not continuous, but rather it is a line spectrum with
discrete lines at 1 kHz intervals. In addition, there are some "strong
lines" in each C/A code that can deviate significantly from a [sin(x)/x]2
envelope. This makes a C/A code receiver vulnerable to continuous wave
(CW) or very narrowband interfering signals since they can mix with a
strong C/A code line and affect the code and carrier tracking loops.

Based on the susceptibility of GPS L1 C/A
code receivers to narrowband interference, NTIA strongly recommends
that the emission limits developed for unlicensed devices permitted to
operate in the TV broadcast bands should include a provision for
harmonic signals that may be generated in the 1559-1610 MHz RNSS band.

IV. UNLICENSED DEVICES THAT
EMPLOY INTERFERENCE MITIGATION TECHNIQUES CAN FACILITATE SHARING WITH
FEDERAL RADARS IN THE 3650-3700 MHz BAND.

Pursuant to the Omnibus Budget
Reconciliation Act of 1993 (OBRA-93),(10)
NTIA identified 235 MHz of spectrum previously allocated for Federal
Government use for reallocation to the private sector.(11)
One of the frequency bands identified, 3650-3700 MHz, was reallocated on
a mixed-use basis effective January 1999.(12)
Under the mixed-use allocation, the Federal Government retained systems
and operations at three sites indefinitely.(13)
Full use of the 3500-3700 MHz by the Department of the Navy (Navy) will
be required at these sites on a primary basis. The locations of these
sites are provided in Table 2. Based on available information,
observance of the 80 km radius of operation around these sites should
provide adequate identification of spectrum conflicts.

TABLE 2

SITES AT WHICH FEDERAL SYSTEMS AND OPERATIONS
IN THE 3650-3700 MHz BAND WILL BE RETAINED INDEFINITELY

Location

Coordinates

Radius of Operations (km)

St. Inigoes, MD

38E 10' 00"N 76E 23' 00"W

80

Pascagoula, MS

30E 22' 00"N 88E 29' 00"W

80

Pensacola, FL(14)

30E 21' 28"N 87E 16' 26"W

80

The AN/SPN-43 is an air traffic control radar system that operates
in the 3500-3700 MHz band at these three sites. Normally, the
AN/SPN-43 is deployed on medium and large carriers and large amphibious
assault ships for simultaneous control and identification of aircraft
in a terminal area. The three "grandfathered sites" support the
land-based facet of the AN/SPN-43 Program. These sites provide unique
functions, which are not duplicated anywhere in the United States. For
example, the St. Inigoes site is used for maintenance, test-calibration
and pre-setting of crystals on the AN/SPN-43 system. The Pascagoula
site is used to conduct test and evaluation, while the Pensacola site
is used for littoral or in-port training.(15)

Fifteen or more frequencies are used at each site to
adequately support their respective requirements. Table 3 shows key
technical characteristics of the AN/SPN-43.

TABLE 3

KEY TECHNICAL CHARACTERISTICS OF THE AN/SPN-43

ELEMENT

VALUE

Frequency Range

3500-3700 MHz

Peak Power

1 Megawatt

Antenna Gain

32 dBi

Antenna Scan Coverage

360E

Necessary Bandwidth

10 MHz

The Navy has expressed concern about the authorization of
unlicensed devices in the 3650-3700 MHz band at power levels
significantly higher than those currently allowed under the
Commission's Part 15 rules.(16)

Navy states that allowing higher power unlicensed operation in the
3650-3700 MHz band with minimal technical requirements could
potentially introduce additional interference sources to the
grandfathered federal operations within the band as well as to
incumbent federal systems in the lower adjacent band.(17)

The Navy reiterates the constraint associated with the original
identification of the 3650-3700 MHz band for reallocation as follows:
"To achieve a satisfactory commercial service which is immediately
adjacent to a band used by multi-megawatt mobile radar systems, the
adoption of effective transmitter emission and receiver selectivity
standards are essential to minimize interference to and from the
federal system operating in this band."(18)

The Department of Army (Army) has similarly raised concerns
regarding higher-powered unlicensed device operation. The Army states
that the increased number of unlicensed devices that could result when
new Part 15 bands are authorized have the potential to add to the
electromagnetic noise floor, which can contribute to an increase in
electromagnetic interference.(19) The
Army further states that, without adequate safeguards, operation of
higher-powered unlicensed devices in this band could potentially
negatively impact military operations at the grandfathered federal sites.(20)

NTIA agrees with the Navy and Army that operation of higher-powered
unlicensed devices in the 3650-3700 MHz band, without adequate control
mechanisms, could potentially adversely impact federal operations in
this shared/mixed-use allocated band. Accordingly, NTIA recommends
that any authorization of higher-powered Part 15 use in this band be
linked with mandated use of effective frequency and/or geographic
avoidance technologies. As the Commission has suggested, such
technologies could include, but would not be limited to, dynamic
frequency selection, listen before transmit protocols, and/or
GPS-assisted geographic avoidance methods.(21)

NTIA also believes that certain unlicensed device applications can
facilitate sharing. For example, similar to the situation in the 5 GHz
band, unlicensed local area networks that employ frequency and/or
geographic interference-mitigation techniques could reduce interference
to the radar operations in the 3650-3700 MHz band.

Assuring that the application of the interference mitigation
technologies is  effective for the specific frequency band and
incumbent systems will require further engineering study. In this
regard, the recent successful analysis and agreement within the United
States addressing sharing arrangements for an international allocation
of mobile devices in the 5 GHz band could serve as a useful model to
address and resolve the technical details.(22)
A Government/Industry project team, as was used in the 5 GHz band
preparing for the 2003 World Radio Conference, could be used to provide
technical guidance on the sharing conditions required for the 3650-3700
MHz band. Such a project team could address emission limits, receiver
interference immunity performance specifications, and
interference-avoidance techniques for unlicensed devices to facilitate
sharing in the 3650-3700 MHz band.

V. SUMMARY

NTIA agrees with the Commission that potential economic benefits
could be gained by permitting unlicensed operations in frequency bands
not currently authorized for unlicensed devices. However, NTIA
recommends that unlicensed device use not be expanded in such a way as
to adversely impact critical Federal systems used to support scientific
research, aviation, and defense. Specifically, NTIA urges the
Commission not to permit the operation of unlicensed devices in the
608-614 MHz band. Second, based on the susceptibility of GPS L1 C/A
code receivers to narrowband interference, NTIA strongly recommends
that the emission limits developed for unlicensed devices permitted to
operate in the TV broadcast bands include a provision for harmonic
signals that may be generated in the 1559-1610 MHz RNSS band. Finally,
although NTIA supports the Commission's effort to allow higher-powered
unlicensed devices in the 3650-3700 MHz band, NTIA recommends that any
such relaxation of the restrictions on power levels and antenna gains
be tied with mandatory adoption of effective frequency and/or
geographic avoidance technologies, as suggested by the Commission, to
protect incumbent systems. Further, in order to conduct the study
needed to identify specific details of any adopted technologies, NTIA
recommends that a project team be formed to examine the merits of the
proposed mitigation techniques and to develop the recommended technical
requirements to allow compatible unlicensed device usage in the
3650-3700 MHz band.

Respectfully Submitted,

Nancy J. Victory

Kathy D. Smith

Assistant Secretary for
Chief Counsel

Communications and Information

Frederick R. Wentland

Acting Associate Administrator

Office of Spectrum Management

Gerald F. Hurt

Edward F. Drocella

Ernesto A. Cerezo

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

May 7, 2003

ENDNOTES:

1.  In the Matter of Additional
Spectrum for Unlicensed Devices Below 900 MHz and in the 3 GHz Band, Notice of Inquiry (NOI), ("hereinafter NOI"), ET Docket No.
02-380, FCC 02-328 (rel. Dec. 20, 2002), 68 Fed. Reg. 2730 (Jan. 21,
2003).

2.  Observations
of radio continuum emissions establish frequency dependence of the
cosmic emissions, which requires the observation of the emission
intensity at a number of frequencies. Observations of radio continuum
emissions are only performed by Federal radio astronomers and
associated universities.

3.  NOI, at ¶14.

4.  Id.

5.  The fundamental frequency
is the principal component of a wave. For example, the component with
the lowest frequency or the greatest amplitude.

6.  The passband is the band
of frequencies which will pass through a receive filter with
essentially no attenuation.

7.  A harmonic is a
sinusoidal wave having a frequency that is an integral multiple of the
fundamental frequency. For example, a wave with twice the frequency of
the fundamental is called the second harmonic.

8.  The GNSS is a satellite
navigation system which provides a world-wide position determination,
time and velocity capability for multi-modal use. As currently
envisioned, the GNSS will encompass aviation, maritime, and terrestrial
navigation.

9.  RTCA DO-235, Assessment of Radio Frequency Interference
Relevant to the GNSS, at C-4 (Jan. 27, 1997).

10.  See Omnibus Budget
Reconciliation Act of 1993, Pub. L. No. 103-66, Title VI, §
6001, 107 Stat. 312, 379 (1993) (amending the NTIA Organization Act to
add a new part B) (codified at 47 U.S.C. §921 et seq.).

11.  National
Telecommunications and Information Administration, NTIA Special
Publication 95-32, Spectrum Reallocation Final Report (hereinafter
"NTIA Final Report") (Feb. 1995).

12.  For a frequency band to
be qualified as "mixed-use" band, OBRA-93 specified that "Federal
Government stations are limited by geographic area, by time, or by
other means so as to guarantee that the potential use to be made by
such Federal Government stations is substantially less (as measured by
geographic area, time, or otherwise) than the potential use to be made
by non-federal stations.", See 47 U.S.C. 923(b)(2).

13.  See NTIA
Final Report at 4-21.

14.  As a result of base
realignment and closures, the Memphis Tennessee site originally
identified for continued Federal system operations was closed, and the
relevant facilities were subsequently moved to the Pensacola, Florida
site. See The Department of the Navy (B. Swearingen, Navy
IRAC Representative) Memo, Navy's Protected Sites in the 3650-3700
MHz Band, to the Department of Commerce (E. Cerezo/NTIA-OSM) (Nov.
19, 1998).

15.  Littoral operations are
operations close to land that is presumed to be occupied, at least in
part, by hostile forces.

16.  The Department of the
Navy (B. Swearingen Navy IRAC Representative) Memorandum for the IRAC
Chairman, Comments on the Additional Spectrum for Unlicensed
Devices Below 900 MHz and in the 3 GHz Band. Notice of Inquiry (ET
Docket No. 02-380, Released Dec. 20, 2002) (March 24, 2003).

17.  Id.

18.  Id. (quoting
NTIA Final Report at 4-20).

19.  The Department of the
Army (LTC Clinton Burrell, Deputy Director, Army Spectrum Management
Office) Memo for the IRAC Chairman (K. Nebbia), Review of the
FCC's Notice of Inquiry on the Subject of Additional Spectrum for
Unlicensed Devices Below 900 MHz and in the 3 GHz Band (March 24,
2003).

20.  Id.

21.  NOI, at ¶ 21.

22.  See U.S.
department of Commerce, National Telecommunications and Information
Administration, Agreement Reached Regarding U.S. Position on 5 GHz
Wireless Access Devices (rel. Jan. 31, 2003), (available at
http://www.ntia.doc.gov/ntiahome/press/2003/5ghzagreement.htm.).