[Federal Register Volume 62, Number 92 (Tuesday, May 13, 1997)]
[Rules and Regulations]
[Pages 26239-26245]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-11584]
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FEDERAL COMMUNICATIONS COMMISSION
47 CFR Parts 2 and 15
[ET Docket No. 96-8; FCC 97-114]
Spread Spectrum Transmitters
AGENCY: Federal Communications Commission.
ACTION: Final rule.
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SUMMARY: By this Report and Order, the Commission amends its
regulations regarding the unlicensed operation of spread spectrum
systems in the 902-928 MHz (``915 MHz''), 2400-2483.5 MHz (``2450
MHz''), and 5725-5850 MHz (``5800 MHz'') bands, as proposed in the
Notice of Proposed Rule Making (``NPRM'') in this proceeding. These
amendments permit the use of high gain directional antennas for systems
operating as fixed, point-to-point stations in the 2450 MHz and 5800
MHz bands. They also reduce the number of hopping channels for
frequency hopping systems operating in the 915 MHz band. In addition,
these amendments clarify existing regulations, codify existing policies
into the rules, and update the definitions. These amendments will
facilitate the growth of spread spectrum systems by enabling and
encouraging practical applications for these systems.
DATES: Effective June 12, 1997.
ADDRESSES: Federal Communications Commission, 1919 M Street, N.W.,
Washington, D.C. 20554.
FOR FURTHER INFORMATION CONTACT: John A. Reed, Office of Engineering
and Technology, (202) 418-2455.
SUPPLEMENTARY INFORMATION: This is a summary of the Commission's Report
and Order in ET Docket No. 96-8, FCC 97-114, adopted April 3, 1997, and
released April 10, 1997. The complete text of this Report and Order is
available for inspection and copying during normal business hours in
the FCC Reference Center (Room 239), 1919 M Street, NW., Washington,
DC, and also may be purchased from the Commission's copy contractor,
International Transcription Services, Inc., (202) 857-3800, 2100 M
Street, NW, Suite 140, Washington, D.C. 20037.
Summary of the Report and Order
1. In the Report and Order (``Order''), the Commission amended
Parts 2 and 15 of its regulations regarding unlicensed spread spectrum
transmission systems operating in the 915 MHz, 2450 MHz and 5800 MHz
bands. Spread spectrum systems use special modulation techniques that
spread the energy of the signal being transmitted over a very wide
bandwidth. This spreading reduces the power density of the signal at
any frequency within the transmitted bandwidth, thereby reducing the
probability of causing interference to other signals occupying the same
spectrum. The reversal of the signal spreading process in the receiver
enables the suppression of strong undesired signals.
2. The Order eliminates the limit on directional gain antennas for
spread spectrum transmitters operating in the 2450 MHz and the 5800 MHz
bands. The operation of these systems is limited to fixed, point-to-
point systems. While transmitters in the 5800 MHz band are not required
to reduce output power when the directional antenna
[[Page 26240]]
gain is increased, the maximum permitted output power of spread
spectrum transmitters in the 2450 MHz band is decreased by 1 dB for
every 3 dB that the directional antenna gain exceeds 6 dBi. This
decrease in the maximum transmitter output power is necessary to reduce
the potential for harmful interference to mobile stations operating in
the 2450 MHz band, especially mobile licensees in the Public Safety
Radio Services under Part 90 of the rules and other Part 15 devices.
The waivers previously issued to six companies to permit the
manufacture of systems at 2450 MHz and 5800 MHz employing unlimited
antenna gain without a reduction in transmitter output power are no
longer in effect upon 30 days from the publication of these final rules
in the Federal Register. Any system manufactured after that date must
comply with the regulations adopted herein.
3. The increase in directional antenna gain will permit users of
spread spectrum systems to establish radio links without the delays and
costs associated with formal frequency coordination and licensing. Such
uses may include backbone connections to the new unlicensed NII system;
intelligent transportation system communications links; high speed
Internet connections for schools, hospitals, and government offices;
energy utility applications; PCS and cellular backbone connections; and
T-1 common carrier links in rural areas. However, the operators of
these systems are reminded that the operation of Part 15 devices is
subject to the conditions that any received interference must be
accepted and that harmful interference may not be caused to other radio
services. Thus, the Commission strongly recommends that operators of
systems that provide critical communication services should exercise
due caution to determine if there are any nearby radio services that
could be affected by their communications.
4. In the Order, the Commission also reduces the minimum number of
non-contiguous channels that must be employed by a frequency hopping
spread spectrum system in the 915 MHz band from 50 channels to 25
channels. This reduction in the number of hopping channels will enable
frequency hopping spread spectrum systems to avoid operations on
frequencies used by wideband, multilateration LMS systems operating
under Part 90 of the rules, thereby reducing mutual interference
problems. Frequency hopping spread spectrum systems that employ less
than 50 hopping channels must employ channel bandwidths of at least 250
kHz; shall not exceed an average time of occupancy on any hopping
frequency of 0.4 seconds in any 10 second period; and shall operate
with a maximum peak transmitter output power of 250 mW with a
directional antenna gain of 6 dBi. Higher antenna gain is permitted
only with a corresponding decrease in transmitter output power.
5. In the Order, the Commission made several amendments to the
rules to clarify existing regulations, codify existing policies into
the rules, and update the definitions. These amendments to the rules
are summarized below:
--The spectral power density limit for direct sequence systems is
modified to indicate that the standard applies to the peak spectral
power density, and the measurement procedure employed for measuring
spectral power density where the spectrum line spacing can not be
resolved is corrected;
--The definition of a direct sequence system is modified, as
proposed in the NPRM;
--The definition of a pseudorandom sequence and a frequency hopping
system is modified, as proposed in the NPRM;
--The rules are clarified to permit short duration transmissions
under the provisions for frequency hopping systems provided the systems
are capable of complying with all of the spread spectrum standards,
including the definition of a frequency hopping systems and the
eventual distribution of the transmissions over the minimum number of
hopping channels;
--An alternative method of measuring the processing gain of a
direct sequence system, based on receiver jamming margin, is
incorporated into the rules;
--The limits on unwanted emissions are simplified, as proposed in
the NPRM;
--The existing policy permitting the coordination of a frequency
hopping system when the system incorporates intelligence that permits
it to recognize other users within the spectrum band so that it
individually and independently chooses and adapts its hopping sequence
to avoid hopping on occupied channels is codified into the rules;
--The prohibition against the marketing and use of external radio
frequency power amplifiers that are not certified as part of the system
and the prohibition against the marketing and use of antenna/
transmitter combinations that are not certified as a system is
clarified in the rules;
--The applicability of the RF guidelines for human exposure, as
specified in Section 1.1307 of the rules, to Part 15 devices is noted;
and
--The prohibition against cross-border operation into Mexico or
Canada and the applicability of the non-interference rules to Canadian
or Mexican radio operations are noted.
Final Regulatory Flexibility Analysis
6. As required by Section 603 of the Regulatory Flexibility Act, 5
U.S.C. 603 (RFA), Initial Regulatory Flexibility Analysis (IRFA) was
incorporated in the Notice of Proposed Rule Making (``NPRM'') in ET
Docket No. 96-8.1 The Commission sought written public
comments on the proposals in the NPRM including the IRFA. The
Commission's Regulatory Flexibility Analysis (FRFA) in this Report and
Order conforms to the RFA, as amended by the Contract with America
Advancement Act of 1996 (CWAAA), Public Law 104-121, 110 Stat. 847
(1996).2
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\1\ Amendment of Parts 2 and 15 of the Commission's Rules
Regarding Spectrum Transmitters, 11 FCC Rcd 3068 (1996), 61 FR
15206, April 5, 1996.
\2\ Subtitle II of the CWAAA is ``The Small Business Regulatory
Enforcement Fairness Act of 1996'' (SBREFA), codified at 5 U.S.C.
601 et seq.
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7. Need for and Objective of the Rule. The objective is to amend
Parts 2 and 15 of the rules regarding the operation of spread spectrum
transmission systems in the 902-928 MHz, 2400-2483.5 MHz and 5725-5850
MHz bands. The Commission is also adopting a number of amendments to
the spread spectrum regulations to clarify the existing regulations, to
codify existing policies into the rules, and to update the current
definitions. These changes to the rules will facilitate the growth of
the spread spectrum industry by enabling and encouraging practical
applications for these products. The new rules will expand the ability
of equipment manufacturers to develop spread spectrum systems for
unlicensed use that provide users with the flexibility to establish
radio links without the delays and costs associated with formal
frequency coordination and licensing. Such uses may include intelligent
transportation system communications links; high speed Internet
connections for schools, hospitals, and government offices; energy
utility applications; PCS and cellular backbone connections; and T-1
common carrier links in rural areas. The new rules will also permit
frequency hopping spread spectrum systems and wideband, multilateration
Location Monitoring Service (LMS) systems to operate within the same
frequency band with decreased potential for mutual interference
problems.
[[Page 26241]]
8. Summary of Significant Issues Raised by the Public Comments in
Response to the Initial Regulatory Flexibility Analysis. Only one
commenter, Adtran submitted comments that were specifically in response
to the IRFA. It agrees with the Commission's assessment that the
changes made in the ``Order'' will have no negative impact on small
entities. In general, commenters were supportive of the Commission's
proposed changes to the rule. The Commission also received numerous
suggestions for improving or modifying the rules. In response to a
Petition for Rule Making filed by WMC, the Commission is eliminating
the limit on directional gain antennas for spread spectrum transmitters
operating in the 2450 MHz and 5800 MHz bands. For spread spectrum
systems operating in the 2450 MHz band, the Commission is implementing
its proposal to require that the output power for the transmitter be
reduced by 1 dB for every 3 dB that the directional gain exceeds 6 dBi.
In addition, in response to a Petition for Rule Making filed by
SpectraLink, the Commission is reducing, from 50 to 25, the minimum
number of channels required for frequency hopping spread spectrum
systems operating in the 915 MHz band.
9. Description and Estimate of the Number of Small Entities Subject
to Which the Rules Apply. The RFA generally defines the term ``small
business'' as having the same meaning as the term ``small business
concern'' under the Small Business Act, 15 U.S.C. 632. Based on that
statutory provision, we will consider a small business concern one
which: (1) Is independently owned and operated; (2) is not dominant in
its field of operation; and (3) satisfies any additional criteria
established by the Small Business Administration (SBA). The RFA SBREFA
provisions also apply to nonprofit organizations and to governmental
organizations. Since the Regulatory Flexibility Act amendments were not
in effect until the record in this proceeding was closed, the
Commission was unable to request information regarding the number of
small businesses that manufacture spread spectrum transmitters and is
unable at this time to determine the number of small businesses that
would be affected by this action. However, the Commission believes that
the amendments being adopted in this proceeding clarify permissible
methods of operation. With the exception of limits on directional
antenna gain versus transmitter output power for systems in the 2450
MHz band, these amendments should not impact any existing equipment
designs. The only parties that would be impacted by the requirement to
reduce transmitter output power when high antenna gains are employed
are WMC, Cylink, ACS, MDS, Larus, and Wi-LAN Inc. These companies are
currently producing this equipment under the conditions of a temporary
waiver that permits them to manufacture fixed, point-to-point spread
spectrum systems in the 2450 MHz band without a limit on directional
antenna gain. All of these companies were notified at the time the
waivers were granted that the waivers would expire upon the date of
final action in this proceeding.
10. The rules adopted in this Order will apply to any entities
manufacturing equipment for unlicensed Part 15 spread spectrum
transmitters. The Commission has not developed a definition of small
entities applicable to manufacturers of spread spectrum transmitters.
Therefore, the applicable definition of small entity is the definition
under the Small Business Administration (``SBA'') rules applicable to
manufacturers of ``Radio and Television Broadcasting and Communications
Equipment''. According to the SBA's regulations, radio frequency
manufacturers must have 750 or fewer employees in order to qualify as a
small business.3 Census Bureau data indicates that there are
858 companies in the United States that manufacture radio and
television broadcasting and communications equipment, and that 778 of
these firms have fewer than 750 employees and would be classified as
small entities.4
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\3\ See 13 CFR 121.201, Standard Industrial Classification (SIC)
Code 3663.
\4\ See U.S. Department of Commerce, 1992 Census of
Transportation, Communications and Utilities (issued May 1995), SIC
category 3663.
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11. Description of Projected Reporting, Recordkeeping and Other
Compliance Requirements. Part 15 spread spectrum transmitters are
already required to be authorized under the Commission's certification
procedure as a prerequisite to marketing and importation. The changes
proposed in this proceeding would not change any of the current
reporting or recordkeeping requirements. Further, the proposed
regulations add permissible methods of operation and would not require
the modification of any existing products, except for those currently
operating under limited waivers that expire upon adoption of this
Order. These requirements include obtaining a grant of certification
for the transmitter and meeting the emission limits specified in the
rules.
12. Skills of an application examiner, radio technician or engineer
will be needed to meet the requirements. In many cases the studies can
be done by a radio technician or engineer. Certification applications
are usually done by applications examiners. It is the responsibility of
the manufacturer of the device to determine whether the device will
comply with the RF radiation limits. This study can be done by
calculation or measurement, depending upon the situation.
13. Significant Alternatives and Steps Taken by Agency to Minimize
Significant Economic Impact on a Substantial Number of Small Entities
Consistent with Stated Objectives. In response to concerns raised in
comments filed in response to the NPRM, the Commission made several
minor clarifying amendments to its proposals. However, there was only
one issue raised in the comments that could have had a significant
economic impact on the manufacturers of spread spectrum systems. In the
NPRM, the Commission proposed to require that the 3 dB beamwidths of
the high gain directional antennas employed with spread spectrum
transmitters differ by no more than a factor of two between the
vertical and horizontal planes.5 Supporting comments were
received from Adtran and Digital Wireless; however, Cushcraft, Cylink,
the Part 15 Coalition and WMC believe that the requirement is an
unnecessary regulation. Cushcraft believes that the majority of
antennas already meet this criterion. Cylink states that this proposal
may prevent applications that require a different antenna design, such
as communications to off-shore platforms. The Commission agrees with
the latter commenters that this portion of its proposal is unnecessary.
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\5\ See NPRM at para. 17.
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14. Commission's Outreach Efforts to Learn of and Respond to the
Views of Small Entities pursuant to SBREFA 5 U.S.C. 609. During the
course of this proceeding Office of Engineering and Technology staff
members have had numerous ex parte meetings with representatives from
Metricom, Inc., Cylink Corporation, Mulcay Consulting Association, and
Digital Wireless Corporation.
15. Report to Congress. The Commission shall send a copy of this
Final Regulatory Flexibility Analysis, along with this Report and
Order, in a report to Congress pursuant to the Small Business
Regulatory Enforcement Fairness Act of 1996, 5 U.S.C. 801(a)(1)(A). A
copy of this FRFA will
[[Page 26242]]
also be published in the Federal Register.
List of Subjects
47 CFR Part 2
Communications equipment, Radio.
47 CFR Part 15
Communications equipment, Radio, Reporting and recordkeeping
requirements.
Federal Communications Commission
William F. Caton,
Acting Secretary.
Rule Changes
Title 47 of the Code of Federal Regulations, Parts 2 and 15, are
amended as follows:
PART 2--FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL
RULES AND REGULATIONS
1. The authority citation for Part 2 continues to read as follows:
Authority: Sec. 4, 302, 303, and 307 of the Communications Act
of 1934, as amended, 47 U.S.C. Sections 154, 302, 303, and 307,
unless otherwise noted.
2. Section 2.1, paragraph (c), is amended by removing the
definition for ``Pseudorandom sequence'', by revising the definition
for ``Direct Sequence Systems'', and by revising the definition for
``Frequency Hopping Systems'' and placing it in alphabetical order to
read as follows:
Sec. 2.1 Terms and definitions.
* * * * *
(c) * * *
* * * * *
Direct Sequence Systems. A spread spectrum system in which the
carrier has been modulated by a high speed spreading code and an
information data stream. The high speed code sequence dominates the
``modulating function'' and is the direct cause of the wide spreading
of the transmitted signal.
* * * * *
Frequency Hopping Systems. A spread spectrum system in which the
carrier is modulated with the coded information in a conventional
manner causing a conventional spreading of the RF energy about the
frequency carrier. The frequency of the carrier is not fixed but
changes at fixed intervals under the direction of a coded sequence. The
wide RF bandwidth needed by such a system is not required by spreading
of the RF energy about the carrier but rather to accommodate the range
of frequencies to which the carrier frequency can hop. The test of a
frequency hopping system is that the near term distribution of hops
appears random, the long term distribution appears evenly distributed
over the hop set, and sequential hops are randomly distributed in both
direction and magnitude of change in the hop set.
* * * * *
PART 15--RADIO FREQUENCY DEVICES
1. The authority citation for Part 15 continues to read as follows:
Authority: 47 U.S.C. 154, 302, 303, 304, 307 and 544A.
2. Section 15.3 is amended by adding a new paragraph (cc), to read
as follows:
Sec. 15.3 Definitions.
* * * * *
(cc) External radio frequency power amplifier. A device which is
not an integral part of an intentional radiator as manufactured and
which, when used in conjunction with an intentional radiator as a
signal source, is capable of amplifying that signal.
3. A new Sec. 15.204 is added, to read as follows:
Sec. 15.204 External radio frequency power amplifiers and antenna
modifications.
(a) Except as otherwise described in paragraph (b) of this section,
no person shall use, manufacture, sell or lease, offer for sale or
lease (including advertising for sale or lease), or import, ship, or
distribute for the purpose of selling or leasing, any external radio
frequency power amplifier or amplifier kit intended for use with a Part
15 intentional radiator.
(b) A transmission system consisting of an intentional radiator, an
external radio frequency power amplifier, and an antenna, may be
authorized, marketed and used under this part. However, when a
transmission system is authorized as a system, it must always be
marketed as a complete system and must always be used in the
configuration in which it was authorized. An external radio frequency
power amplifier shall be marketed only in the system configuration with
which the amplifier is authorized and shall not be marketed as a
separate product.
(c) Only the antenna with which an intentional radiator is
authorized may be used with the intentional radiator.
4. Section 15.247 is amended by revising paragraphs (a)(1)(i), (b),
(c), (d), and (e), and by adding new paragraphs (g) and (h) before the
note at the end of the section, to read as follows:
Sec. 15.247 Operation within the bands 902-928 MHz, 2400-2483.5 MHz,
and 5725-5850 MHz.
(a) * * *
(1) * * *
(i) For frequency hopping systems operating in the 902-928 MHz
band: if the 20 dB bandwidth of the hopping channel is less than 250
kHz, the system shall use at least 50 hopping frequencies and the
average time of occupancy on any frequency shall not be greater than
0.4 seconds within a 20 second period; if the 20 dB bandwidth of the
hopping channel is 250 kHz or greater, the system shall use at least 25
hopping frequencies and the average time of occupancy on any frequency
shall not be greater than 0.4 seconds within a 10 second period. The
maximum allowed 20 dB bandwidth of the hopping channel is 500 kHz.
* * * * *
(b) The maximum peak output power of the intentional radiator shall
not exceed the following:
(1) For frequency hopping systems operating in the 2400-2483.5 MHz
or 5725-5850 MHz band and for all direct sequence systems: 1 watt.
(2) For frequency hopping systems operating in the 902-928 MHz
band: 1 watt for systems employing at least 50 hopping channels; and,
0.25 watts for systems employing less than 50 hopping channels, but at
least 25 hopping channels, as permitted under paragraph (a)(1)(i) of
this section.
(3) Except as shown in paragraphs (b)(3) (i), (ii) and (iii) of
this section, if transmitting antennas of directional gain greater than
6 dBi are used the peak output power from the intentional radiator
shall be reduced below the stated values in paragraphs (b)(1) or (b)(2)
of this section, as appropriate, by the amount in dB that the
directional gain of the antenna exceeds 6 dBi.
(i) Systems operating in the 2400-2483.5 MHz band that are used
exclusively for fixed, point-to-point operations may employ
transmitting antennas with directional gain greater than 6 dBi provided
the maximum peak output power of the intentional radiator is reduced by
1 dB for every 3 dB that the directional gain of the antenna exceeds 6
dBi.
(ii) Systems operating in the 5725-5850 MHz band that are used
exclusively for fixed, point-to-point operations may employ
transmitting antennas with directional gain greater than 6 dBi without
any corresponding reduction in transmitter peak output power.
(iii) Fixed, point-to-point operation, as used in paragraphs
(b)(3)(i) and (b)(3)(ii) of this section, excludes the use of point-to-
multipoint systems, omnidirectional applications, and multiple co-
located intentional radiators
[[Page 26243]]
transmitting the same information. The operator of the spread spectrum
intentional radiator or, if the equipment is professionally installed,
the installer is responsible for ensuring that the system is used
exclusively for fixed, point-to-point operations. The instruction
manual furnished with the intentional radiator shall contain language
in the installation instructions informing the operator and the
installer of this responsibility.
(4) Systems operating under the provisions of this section shall be
operated in a manner that ensures that the public is not exposed to
radio frequency energy levels in excess of the Commission's guidelines.
See Sec. 1.1307(b)(1) of this chapter.
(c) In any 100 kHz bandwidth outside the frequency band in which
the spread spectrum intentional radiator is operating, the radio
frequency power that is produced by the intentional radiator shall be
at least 20 dB below that in the 100 kHz bandwidth within the band that
contains the highest level of the desired power, based on either an RF
conducted or a radiated measurement. Attenuation below the general
limits specified in Sec. 15.209(a) is not required. In addition,
radiated emissions which fall in the restricted bands, as defined in
Sec. 15.205(a), must also comply with the radiated emission limits
specified in Sec. 15.209(a) (see Sec. 15.205(c)).
(d) For direct sequence systems, the peak power spectral density
conducted from the intentional radiator to the antenna shall not be
greater than 8 dBm in any 3 kHz band during any time interval of
continuous transmission.
(e) The processing gain of a direct sequence system shall be at
least 10 dB. The processing gain represents the improvement to the
received signal-to-noise ratio, after filtering to the information
bandwidth, from the spreading/despreading function. The processing gain
may be determined using one of the following methods:
(1) As measured at the demodulated output of the receiver: the
ratio in dB of the signal-to-noise ratio with the system spreading code
turned off to the signal-to-noise ratio with the system spreading code
turned on.
(2) As measured using the CW jamming margin method: a signal
generator is stepped in 50 kHz increments across the passband of the
system, recording at each point the generator level required to produce
the recommended Bit Error Rate (BER). This level is the jammer level.
The output power of the intentional radiator is measured at the same
point. The jammer to signal ratio (J/S) is then calculated, discarding
the worst 20% of the J/S data points. The lowest remaining J/S ratio is
used to calculate the processing gain, as follows: Gp = (S/N) o + Mj +
Lsys, where Gp = processing gain of the system, (S/N) o = signal to
noise ratio required for the chosen BER, Mj = J/S ratio, and Lsys =
system losses. Note that total losses in a system, including
intentional radiator and receiver, should be assumed to be no more than
2 dB.
* * * * *
(g) Frequency hopping spread spectrum systems are not required to
employ all available hopping channels during each transmission.
However, the system, consisting of both the transmitter and the
receiver, must be designed to comply with all of the regulations in
this section should the transmitter be presented with a continuous data
(or information) stream. In addition, a system employing short
transmission bursts must comply with the definition of a frequency
hopping system and must distribute its transmissions over the minimum
number of hopping channels specified in this section.
(h) The incorporation of intelligence within a frequency hopping
spread spectrum system that permits the system to recognize other users
within the spectrum band so that it individually and independently
chooses and adapts its hopsets to avoid hopping on occupied channels is
permitted. The coordination of frequency hopping systems in any other
manner for the express purpose of avoiding the simultaneous occupancy
of individual hopping frequencies by multiple transmitters is not
permitted.
* * * * *
Note: The following appendix will not appear in the Code of
Federal Regulations.
Appendix--Measurement Procedure for Spread Spectrum Transmitters
Federal Communications Commission
Equipment Authorization Division, 7435 Oakland Mills Road, Columbia,
MD 21046, Telephone: (301) 725-1585, Facsimile: (301) 344-2050
Guidance on Measurements for Direct Sequence Spread Spectrum Systems
Part 15 of the FCC Rules provides for operation of direct
sequence spread spectrum transmitters. Examples of devices that
operate under these rules include radio local area networks,
cordless telephones, wireless cash registers, and wireless inventory
tracking systems.
The Commission frequently receives requests for guidance as to
how to perform measurements to demonstrate compliance with the
technical standards for such systems. No formal measurement
procedure has been established for determining compliance with the
technical standards. Such tests are to be performed following the
general guidance in Section 15.31 of the FCC Rules and using good
engineering practice. The following provides information on the
measurement techniques the Commission has accepted in the past for
equipment authorization purposes. Alternative techniques may be
acceptable upon consultation and approval by the Commission staff.
The information is organized according to the pertinent FCC rule
sections.
Section 15.31(m): This rule specifies the number of operating
frequencies to be examined for tunable equipment.
Section 15.207: Power line conducted emissions. If the unit is
AC powered, an AC power line conducted test is also required per
this rule.
Section 15.247(a)(2): Bandwidth. Make the measurement with the
spectrum analyzer's resolution bandwidth (RBW) = 100 kHz. In order
to make an accurate measurement, set the span >> RBW.
Section 15.247(b): Power output. This is an RF conducted test.
Use a direct connection between the antenna port of the transmitter
and the spectrum analyzer, through suitable attenuation. Set the RBW
> 6 dB bandwidth of the emission or use a peak power meter.
Section 15.247(c): Spurious emissions. The following tests are
required :
(1) RF antenna conducted test: Set RBW = 100 kHz, Video
bandwidth (VBW) > RBW, scan up through 10th harmonic. All harmonics/
spurs must be at least 20 dB down from the highest emission level
within the authorized band as measured with a 100 kHz RBW.
(2) Radiated emission test: Applies to harmonics/spurs that fall
in the restricted bands listed in Section 15.205. The maximum
permitted average field strength is listed in Section 15.209. A pre-
amp (and possibly a high-pass filter) is necessary for this
measurement. For measurements above 1 GHz, set RBW = 1 MHz, VBW = 10
Hz, Sweep: Auto. If the emission is pulsed, modify the unit for
continuous operation, use the settings shown above, then correct the
reading by subtracting the peak-average correction factor, derived
from the appropriate duty cycle calculation. See Section 15.35(b)
and (c).
Section 15.247(d): Power spectral density. Locate and zoom in on
emission peak(s) within the passband. Set RBW = 3 kHz, VBW > RBW,
sweep = (SPAN/3 kHz) e.g., for a span of 1.5 MHz, the sweep should
be 1.5 x 106 3 x 103= 500
seconds. The peak level measured must be no greater than +8 dBm. If
external attenuation is used, don't forget to add this value to the
reading. Use the following guidelines for modifying the power
spectral density measurement procedure when necessary.
For devices with spectrum line spacing greater than 3
kHz no change is required.
For devices with spectrum line spacing equal to or less
than 3 kHz, the resolution bandwidth must be reduced below 3 kHz
until the individual lines in the spectrum are resolved. The
measurement data must then be normalized to 3 kHz by summing the
power of all the individual spectral lines
[[Page 26244]]
within a 3 kHz band (in linear power units) to determine compliance.
If the spectrum line spacing cannot be resolved on the
available spectrum analyzer, the noise density function on most
modern conventional spectrum analyzers will directly measure the
noise power density normalized to a 1 Hz noise power bandwidth. Add
34.8 dB for correction to 3 kHz.
Should all the above fail or any controversy develop
regarding accuracy of measurement, the Laboratory will use the HP
89440A Vector Signal Analyzer for final measurement unless a clear
showing can be made for a further alternate.
Section 15.247(e): Processing Gain. The Processing Gain may be
measured using the CW jamming margin method. Figure 1 shows the test
configuration. The test consists of stepping a signal generator in
50 kHz increments across the passband of the system. At each point,
the generator level required to produce the recommended Bit Error
Rate (BER) is recorded. This level is the jammer level. The output
power of the transmitting unit is measured at the same point. The
Jammer to Signal (J/S) ratio is then calculated. Discard the worst
20% of the J/S data points. The lowest remaining J/S ratio is used
when calculating the Processing Gain.
In a practical system, there are always implementation losses
which degrade the performance below that of an optimal theoretical
system of the same type. Losses occur due to non-optimal filtering,
lack of equalization, LO phase noise, ``corner cutting in digital
processing'', etc. Total losses in a system, including transmitter
and receiver, should be assumed to be no more than 2 dB.
The signal to noise ratio for an ideal non-coherent receiver is
calculated from:
(1) Pe = \1/2\e(--\1/2\(S/N)o)
where :
Pe = probability of error (BER)
(S/N)o = the required signal to noise ratio at the receiver
output for a given received signal quality
This is an example. You should use the equation (or curve)
dictated by your demodulation scheme.
Ref.: Viterbi, A. J. Principles of Coherent Communications, (New
York: McGraw-Hill 1966), Pg. 207 Using equation (1) shown above,
calculate the signal to noise ratio required for your chosen BER.
This value and the measured J/S ratio are used in the following
equation to calculate the Processing Gain (Gp) of the system.
Gp=(S/N)o+Mj+Lsys
where:
(S/N)o = Signal to noise ratio
Mj = J/S ratio
Lsys = System losses.
Ref.: Dixon, R., Spread Spectrum Systems (New York: Wiley,
1984), Chapter 1.
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Alternative Test Procedures
If antenna conducted tests cannot be performed on this device,
radiated tests to show compliance with the various conducted
requirements of Section 15.247 are acceptable. As stated previously,
a pre-amp must be used in making the following measurements.
(1) Calculate the transmitter's peak power using the following
equation:
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Where:
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E is the measured maximum field strength in V/m utilizing the
widest available RBW.
G is the numeric gain of the transmitting antenna over an
isotropic radiator.
d is the distance in meters from which the field strength was
measured.
P is the power in watts for which you are solving:
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(2) Measure the power spectral density as follows:
A. Tune the analyzer to the highest point of the maximized
fundamental emission. Reset the analyzer to a RBW = 3 kHz, VBW >
RBW, span = 300 kHz, sweep = 100 sec.
B. From the peak level obtained in (A), derive the field
strength, E, by applying the appropriate antenna factor, cable loss,
pre-amp gain, etc. Using the equation listed in (1), calculate a
power level for comparison to the +8 dBm limit.
[FR Doc. 97-11584 Filed 5-12-97; 8:45 am]
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