Goto Section: 15.321 | 15.401 | Table of Contents
Revised as of October 1, 2020
Goto Year:2019 |
§ 15.323 Specific requirements for devices operating in the 1920-1930 MHz
(a) Operation shall be contained within the 1920-1930 MHz band. The
emission bandwidth shall be less than 2.5 MHz. The power level shall be
as specified in § 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
(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 repeated.
(5) If access to spectrum is not available as determined by the above,
and a minimum of 20 duplex system access channels are defined for the
system, the time and spectrum windows with the lowest power level 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 band shall be attenuated below a reference
power of 112 milliwatts as follows: 30 dB between the band and 1.25 MHz
above or below the band; 50 dB between 1.25 and 2.5 MHz above or below
the band; and 60 dB at 2.5 MHz or greater above or below the band.
Emissions inside the 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 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 this band
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° to +
50 °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 °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
[ 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; 77 FR 43013 , July 23, 2012]
Subpart E--Unlicensed National Information Infrastructure Devices
Goto Section: 15.321 | 15.401
Goto Year: 2019 |
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