[Code of Federal Regulations]
[Title 47, Volume 1, Parts 0 to 19]
[Revised as of October 1, 1999]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.247]
[Page 705-707]
TITLE 47--TELECOMMUNICATION
CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION
PART 15--RADIO FREQUENCY DEVICES--Table of Contents
Subpart C--Intentional Radiators
Sec. 15.247 Operation within the bands 902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz.
(a) Operation under the provisions of this section is limited to
frequency hopping and direct sequence spread spectrum intentional
radiators that comply with the following provisions:
(1) Frequency hopping systems shall have hopping channel carrier
frequencies separated by a minimum of 25 kHz or the 20 dB bandwidth of
the hopping channel, whichever is greater. The system shall hop to
channel frequencies that are selected at the system hopping rate from a
pseudorandomly ordered list of hopping frequencies. Each frequency must
be used equally on the average by each transmitter. The system receivers
shall have input bandwidths that match the hopping channel bandwidths of
their corresponding transmitters and shall shift frequencies in
synchronization with the transmitted signals.
(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.
[[Page 706]]
(ii) Frequency hopping systems operating in the 2400-2483.5 MHz and
5725-5850 MHz bands shall use at least 75 hopping frequencies. The
maximum 20 dB bandwidth of the hopping channel is 1 MHz. The average
time of occupancy on any frequency shall not be greater than 0.4 seconds
within a 30 second period.
(2) For direct sequence systems, the minimum 6 dB bandwidth shall be
at least 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 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
[[Page 707]]
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.
(f) Hybrid systems that employ a combination of both direct sequence
and frequency hopping modulation techniques shall achieve a processing
gain of at least 17 dB from the combined techniques. The frequency
hopping operation of the hybrid system, with the direct sequence
operation turned off, shall have an average time of occupancy on any
frequency not to exceed 0.4 seconds within a time period in seconds
equal to the number of hopping frequencies employed multiplied by 0.4.
The direct sequence operation of the hybrid system, with the frequency
hopping operation turned off, shall comply with the power density
requirements of paragraph (d) of this section.
(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: Spread spectrum systems are sharing these bands on a
noninterference basis with systems supporting critical Government
requirements that have been allocated the usage of these bands,
secondary only to ISM equipment operated under the provisions of part 18
of this chapter. Many of these Government systems are airborne
radiolocation systems that emit a high EIRP which can cause interference
to other users. Also, investigations of the effect of spread spectrum
interference to U. S. Government operations in the 902-928 MHz band may
require a future decrease in the power limits allowed for spread
spectrum operation.
[54 FR 17714, Apr. 25, 1989, as amended at 55 FR 28762, July 13, 1990;
62 FR 26242, May 13, 1997]