|The Federal Communications Commission (FCC) is the authority
in the United States of America that creates and enforces the use of airwaves throughout the entire
radio frequency spectrum. This group of documents contains the entirety of the
FCC Part 15 regulations
that concern unlicensed radio frequency devices. As with all government documents, this material
is in the public domain and may be freely copied so long as the content is not changed. This copy
is provided as a convenience for RF Cafe visitors.
Click here for the
Table of Contents.
[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2008]
From the U.S. Government Printing Office via GPO Access
CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION
PART 15_RADIO FREQUENCY DEVICES--Table of Contents
Subpart D_Unlicensed Personal Communications Service Devices
Sec. 15.323 Specific requirements for devices operating in
the 1920-1930 MHz sub-band.
(a) Operation shall be contained within the 1920-1930 MHz band. The
emission bandwidth shall be less then 2.5 MHz. The power level shall be
as specified in Sec. 15.319(c), but in no event shall the emission
bandwidth be less than 50 kHz.
(c) Devices must incorporate a mechanism for monitoring the time and
spectrum windows that its transmission is intended to occupy. The
following criteria must be met:
(1) Immediately prior to initiating transmission, devices must
monitor the combined time and spectrum windows in which they intend to
transmit for a period of at least 10 milliseconds for systems designed
to use a 10 milliseconds or shorter frame period or at least 20
milliseconds for systems designed to use a 20 milliseconds frame period.
(2) The monitoring threshold must not be more than 30 dB above the
thermal noise power for a bandwidth equivalent to the emission bandwidth
used by the device.
(3) If no signal above the threshold level is detected, transmission
may commence and continue with the same emission bandwidth in the
monitored time and spectrum windows without further monitoring. However,
occupation of the same combined time and spectrum windows by a device or
group of cooperating devices continuously over a period of time longer
than 8 hours is not permitted without repeating the access criteria.
(4) Once access to specific combined time and spectrum windows is
obtained an acknowledgment from a system participant must be received by
the initiating transmitter within one second or transmission must cease.
Periodic acknowledgments must be received at least every 30 seconds or
transmission must cease. Channels used exclusively for control and
signaling information may transmit continuously for 30 seconds without
receiving an acknowledgment, at which time the access criteria must be
(5) If access to spectrum is not available as determined by the
above, and a minimum of 40 duplex system access channels are defined for
the system, the time and spectrum windows with the lowest power level
below a monitoring threshold of 50 dB above the thermal noise power
determined for the emission bandwidth may be accessed. A device
utilizing the provisions of this paragraph must have monitored all
access channels defined for its system within the last 10 seconds and
must verify, within the 20 milliseconds (40 milliseconds for devices
designed to use
a 20 milliseconds frame period) immediately preceding actual channel
access that the detected power of the selected time and spectrum windows
is no higher than the previously detected value. The power measurement
resolution for this comparison must be accurate to within 6 dB. No
device or group of co-operating devices located within 1 meter of each
other shall during any frame period occupy more than 6 MHz of aggregate
bandwidth, or alternatively, more than one third of the time and
spectrum windows defined by the system.
(6) If the selected combined time and spectrum windows are
unavailable, the device may either monitor and select different windows
or seek to use the same windows after waiting an amount of time,
randomly chosen from a uniform random distribution between 10 and 150
milliseconds, commencing when the channel becomes available.
(7) The monitoring system bandwidth must be equal to or greater than
the emission bandwidth of the intended transmission and have a maximum
reaction time less than 50xSQRT (1.25/emission bandwidth in MHz)
microseconds for signals at the applicable threshold level but shall not
be required to be less than 50 microseconds. If a signal is detected
that is 6 dB or more above the applicable threshold level, the maximum
reaction time shall be 35xSQRT (1.25/emission bandwidth in MHz)
microseconds but shall not be required to be less than 35 microseconds.
(8) The monitoring system shall use the same antenna used for
transmission, or an antenna that yields equivalent reception at that
(9) Devices that have a power output lower than the maximum
permitted under this subpart may increase their monitoring detection
threshold by one decibel for each one decibel that the transmitter power
is below the maximum permitted.
(10) An initiating device may attempt to establish a duplex
connection by monitoring both its intended transmit and receive time and
spectrum windows. If both the intended transmit and receive time and
spectrum windows meet the access criteria, then the initiating device
can initiate a transmission in the intended transmit time and spectrum
window. If the power detected by the responding device can be decoded as
a duplex connection signal from the initiating device, then the
responding device may immediately begin transmitting on the receive time
and spectrum window monitored by the initiating device.
(11) An initiating device that is prevented from monitoring during
its intended transmit window due to monitoring system blocking from the
transmissions of a co-located (within one meter) transmitter of the same
system, may monitor the portions of the time and spectrum windows in
which they intend to receive over a period of at least 10 milliseconds.
The monitored time and spectrum window must total at least 50 percent of
the 10 millisecond frame interval and the monitored spectrum must be
within 1.25 MHz of the center frequency of channel(s) already occupied
by that device or co-located co-operating devices. If the access
criteria is met for the intended receive time and spectrum window under
the above conditions, then transmission in the intended transmit window
by the initiating device may commence.
(12) The provisions of (c)(10) or (c)(11) of this section shall not
be used to extend the range of spectrum occupied over space or time for
the purpose of denying fair access to spectrum to other devices.
(d) Emissions outside the sub-band shall be attenuated below a
reference power of 112 milliwatts as follows: 30 dB between the sub-band
and 1.25 MHz above or below the sub-band; 50 dB between 1.25 and 2.5 MHz
above or below the sub-band; and 60 dB at 2.5 MHz or greater above or
below the sub-band. Emissions inside the sub-band must comply with the
following emission mask: In the bands between 1B and 2B measured from
the center of the emission bandwidth the total power emitted by the
device shall be at least 30 dB below the transmit power permitted for
that device; in the bands between 2B and 3B measured from the center of
the emission bandwidth the total power emitted by an intentional
radiator shall be at least 50 dB below the transmit power permitted for
that radiator; in the bands between 3B and the sub-
band edge the total power emitted by an intentional radiator in the
measurement bandwidth shall be at least 60 dB below the transmit power
permitted for that radiator. ``B'' is defined as the emission bandwidth
of the device in hertz. Compliance with the emission limits is based on
the use of measurement instrumentation employing peak detector function
with an instrument resolution bandwidth approximately equal to 1.0
percent of the emission bandwidth of the device under measurement.
(e) The frame period (a set of consecutive time slots in which the
position of each time slot can be identified by reference to a
synchronizing source) of an intentional radiator operating in these sub-
bands shall be 20 milliseconds or 10 milliseconds/X where X is a
positive whole number. Each device that implements time division for the
purposes of maintaining a duplex connection on a given frequency carrier
shall maintain a frame repetition rate with a frequency stability of at
least 50 parts per million (ppm). Each device which further divides
access in time in order to support multiple communication links on a
given frequency carrier shall maintain a frame repetition rate with a
frequency stability of at least 10 ppm. The jitter (time-related,
abrupt, spurious variations in the duration of the frame interval)
introduced at the two ends of such a communication link shall not exceed
25 microseconds for any two consecutive transmissions. Transmissions
shall be continuous in every time and spectrum window during the frame
period defined for the device.
(f) The frequency stability of the carrier frequency of the
intentional radiator shall be maintained within 10
ppm over 1 hour or the interval between channel access monitoring,
whichever is shorter. The frequency stability shall be maintained over a
temperature variation of -20[deg] to +50 [deg]C at normal supply
voltage, and over a variation in the primary supply voltage of 85
percent to 115 percent of the rated supply voltage at a temperature of
20 [deg]C. For equipment that is capable only of operating from a
battery, the frequency stability tests shall be performed using a new
battery without any further requirement to vary supply voltage.
[58 FR 59180, Nov. 8, 1993; 59 FR 15269, Mar. 31, 1994. Redesignated at
59 FR 32852, June 24, 1994, as amended at 59 FR 32853, June 24, 1994; 59
FR 40835, Aug. 10, 1994; 59 FR 55373, Nov. 7, 1994; 60 FR 3303, Jan. 13,
1995; 69 FR 62621, Oct. 27, 2004]