Sec. 15.321  Specific requirements for asynchronous devices operating in 
          the 1910-1920 MHz and 2390-2400 MHz bands.

    (a) Operation shall be contained within either or both of the 1910-
1920 MHz and 2390-2400 MHz bands. The emission bandwidth of any 
intentional radiator operating in these bands shall be no less than 500 
kHz.
    (b) All systems of less than 2.5 MHz emission bandwidth shall start 
searching for an available spectrum window within 3 MHz of the band edge 
at 1910, 1920, 2390, or 2400 MHz while systems of more than 2.5 MHz 
emission bandwidth will first occupy the center half of the band. 
Devices with an emission bandwidth of less than 1.0 MHz may not occupy 
the center half of the band if other spectrum is available.
    (c) Asynchronous devices must incorporate a mechanism for monitoring 
the spectrum that its transmission is intended to occupy. The following 
criteria must be met:
    (1) Immediately prior to initiating a transmission, devices must 
monitor the spectrum window they intend to use for at least 50 
microseconds.
    (2) The monitoring threshold must not be more than 32 dB above the 
thermal noise power for a bandwidth equivalent to the emission bandwidth 
of the device.
    (3) If no signal above the threshold level is detected, a 
transmission burst may commence in the monitored spectrum window. Once a 
transmission burst has started, an individual device or a group of 
cooperative devices is not required to monitor the spectrum window 
provided the intraburst gap timing requirement specified below is not 
exceeded.
    (4) After completion of a transmission, an individual device or 
cooperating group of devices must cease transmission and wait a 
deference time randomly chosen from a uniform random distribution 
ranging from 50 to 750 microseconds, after which time an attempt to 
access the band again may be initiated. For each occasion that an access 
attempt fails after the initial inter-burst interval, the range of the 
deference time chosen shall double until an upper limit of 12 
milliseconds is reached. The deference time remains at the upper limit 
of 12 milliseconds until an access attempt is successful. The deference 
time is re-initialized after each successful access attempt.
    (5) The monitoring system bandwidth must be equal to or greater than 
the emission bandwidth of the intended transmission and shall have a 
maximum reaction time less than 50 x SQRT(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 threshold level, the maximum 
reaction time shall be 35 x SQRT(1.25/emission bandwidth in MHz) 
microseconds but shall not be required to be less than 35 microseconds.
    (6) The monitoring system shall use the same antenna used for 
transmission, or an antenna that yields equivalent reception at that 
location.
    (7) Devices that have a power output lower than the maximum 
permitted under the rules may increase their detection threshold by one 
decibel for each one decibel that the transmitter power is below the 
maximum permitted.
    (d) Emissions shall be attenuated below a reference power of 112 
milliwatts as follows: 30 dB between the sub-band edges 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. Compliance with the emissions limits is based on the use of 
measurement instrumentation employing a 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 frequency stability of the carrier frequency of intentional 
radiators operating in accordance with this section shall be 
&177;10 ppm over 10 milliseconds 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.Celsius 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 degrees

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Celsius. For equipment that is capable of operating only from a battery, 
the frequency stability tests shall be performed using a new battery 
without any further requirement to vary supply voltage.
    (f) An asynchronous transmission burst is a series of transmissions 
from one or more transmitters acting cooperatively. The transmission 
burst duration from one device or group of devices acting cooperatively 
shall be no greater than 10 milliseconds. Any intraburst gap between 
cooperating devices shall not exceed 25 microseconds.
    (g) Operation of devices in the 2390-2400 MHz band from aircraft 
while airborne is prohibited, in order to protect space research 
operations at the National Astronomy and Ionospheric Center at Arecibo, 
Puerto Rico.
[ 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;  60 FR 13073 , Mar. 10, 1995;  61 FR 55926 , Oct. 
30, 1996]