Goto Section: 15.245 | 15.249 | Table of Contents
FCC 15.247
Revised as of December 4, 2012
Goto Year:2011 |
2013
§ 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 digitally modulated 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. Alternatively, frequency
hopping systems operating in the 2400-2483.5 MHz band may have hopping
channel carrier frequencies that are separated by 25 kHz or two-thirds
of the 20 dB bandwidth of the hopping channel, whichever is greater,
provided the systems operate with an output power no greater than 125
mW. The system shall hop to channel frequencies that are selected at
the system hopping rate from a pseudo randomly 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.
(ii) Frequency hopping systems operating in the 5725-5850 MHz band
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.
(iii) Frequency hopping systems in the 2400-2483.5 MHz band shall use
at least 15 channels. The average time of occupancy on any channel
shall not be greater than 0.4 seconds within a period of 0.4 seconds
multiplied by the number of hopping channels employed. Frequency
hopping systems may avoid or suppress transmissions on a particular
hopping frequency provided that a minimum of 15 channels are used.
(2) Systems using digital modulation techniques may operate in the
902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz bands. The minimum 6 dB
bandwidth shall be at least 500 kHz.
(b) The maximum peak conducted output power of the intentional radiator
shall not exceed the following:
(1) For frequency hopping systems operating in the 2400-2483.5 MHz band
employing at least 75 non-overlapping hopping channels, and all
frequency hopping systems in the 5725-5850 MHz band: 1 watt. For all
other frequency hopping systems in the 2400-2483.5 MHz band: 0.125
watts.
(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) For systems using digital modulation in the 902-928 MHz,
2400-2483.5 MHz, and 5725-5850 MHz bands: 1 Watt. As an alternative to
a peak power measurement, compliance with the one Watt limit can be
based on a measurement of the maximum conducted output power. Maximum
Conducted Output Power is defined as the total transmit power delivered
to all antennas and antenna elements averaged across all symbols in the
signaling alphabet when the transmitter is operating at its maximum
power control level. Power must be summed across all antennas and
antenna elements. The average must not include any time intervals
during which the transmitter is off or is transmitting at a reduced
power level. If multiple modes of operation are possible (e.g.,
alternative modulation methods), the maximum conducted output power is
the highest total transmit power occurring in any mode.
(4) The conducted output power limit specified in paragraph (b) of this
section is based on the use of antennas with directional gains that do
not exceed 6 dBi. Except as shown in paragraph (c) of this section, if
transmitting antennas of directional gain greater than 6 dBi are used,
the conducted output power from the intentional radiator shall be
reduced below the stated values in paragraphs (b)(1), (b)(2), and
(b)(3) 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.
(c) Operation with directional antenna gains greater than 6 dBi.
(1) Fixed point-to-point operation:
(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 conducted 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 conducted output power.
(iii) Fixed, point-to-point operation, as used in paragraphs (c)(1)(i)
and (c)(1)(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 or digitally modulated 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.
(2) In addition to the provisions in paragraphs (b)(1), (b)(3), (b)(4)
and (c)(1)(i) of this section, transmitters operating in the
2400-2483.5 MHz band that emit multiple directional beams,
simultaneously or sequentially, for the purpose of directing signals to
individual receivers or to groups of receivers provided the emissions
comply with the following:
(i) Different information must be transmitted to each receiver.
(ii) If the transmitter employs an antenna system that emits multiple
directional beams but does not do emit multiple directional beams
simultaneously, the total output power conducted to the array or arrays
that comprise the device, i.e. , the sum of the power supplied to all
antennas, antenna elements, staves, etc. and summed across all carriers
or frequency channels, shall not exceed the limit specified in
paragraph (b)(1) or (b)(3) of this section, as applicable. However, the
total conducted output power shall be reduced by 1 dB below the
specified limits for each 3 dB that the directional gain of the
antenna/antenna array exceeds 6 dBi. The directional antenna gain shall
be computed as follows:
(A) The directional gain shall be calculated as the sum of 10 log
(number of array elements or staves) plus the directional gain of the
element or stave having the highest gain.
(B) A lower value for the directional gain than that calculated in
paragraph (c)(2)(ii)(A) of this section will be accepted if sufficient
evidence is presented, e.g., due to shading of the array or coherence
loss in the beamforming.
(iii) If a transmitter employs an antenna that operates simultaneously
on multiple directional beams using the same or different frequency
channels, the power supplied to each emission beam is subject to the
power limit specified in paragraph (c)(2)(ii) of this section. If
transmitted beams overlap, the power shall be reduced to ensure that
their aggregate power does not exceed the limit specified in paragraph
(c)(2)(ii) of this section. In addition, the aggregate power
transmitted simultaneously on all beams shall not exceed the limit
specified in paragraph (c)(2)(ii) of this section by more than 8 dB.
(iv) Transmitters that emit a single directional beam shall operate
under the provisions of paragraph (c)(1) of this section.
(d) In any 100 kHz bandwidth outside the frequency band in which the
spread spectrum or digitally modulated 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, provided the transmitter demonstrates compliance with the
peak conducted power limits. If the transmitter complies with the
conducted power limits based on the use of RMS averaging over a time
interval, as permitted under paragraph (b)(3) of this section, the
attenuation required under this paragraph shall be 30 dB instead of 20
dB. Attenuation below the general limits specified in § 15.209(a) is
not required. In addition, radiated emissions which fall in the
restricted bands, as defined in § 15.205(a), must also comply with the
radiated emission limits specified in § 15.209(a) (see § 15.205(c)).
(e) For digitally modulated systems, the 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. This power spectral density shall be
determined in accordance with the provisions of paragraph (b) of this
section. The same method of determining the conducted output power
shall be used to determine the power spectral density.
(f) For the purposes of this section, hybrid systems are those that
employ a combination of both frequency hopping and digital modulation
techniques. The frequency hopping operation of the hybrid system, with
the direct sequence or digital modulation 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 digital modulation
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.
(i) 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 § 1.1307(b)(1) of this chapter.
[ 54 FR 17714 , Apr. 25, 1989, as amended at 55 FR 28762 , July 13, 1990;
62 FR 26242 , May 13, 1997; 65 FR 57561 , Sept. 25, 2000; 67 FR 42734 ,
June 25, 2002; 69 FR 54035 , Sept. 7, 2004; 72 FR 5632 , Feb. 7, 2007]
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Goto Section: 15.245 | 15.249
Goto Year: 2011 |
2013
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