§  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 § 15.319(c), but in no event shall the emission
   bandwidth be less than 50 kHz.

   (b) [Reserved]

   (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 repeated.

   (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
   location.

   (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
   -20DEG to +50 DEGC 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 DEGC. 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]

Subpart E--Unlicensed National Information Infrastructure Devices