§  15.711   Interference avoidance mechanisms.

   (a) Except as provided in § 15.717, television channel availability for
   a TVBD is determined based on either the geo-location and database
   access mechanism described in paragraph (b) of this section or spectrum
   sensing described in paragraph (c) of this section.

   (1) A TVBD shall rely on the geo-location and database access mechanism
   to identify available television channels consistent with the
   interference protection requirements of § 15.712. Such protection will
   be provided for the following authorized services: digital television
   stations, digital and analog Class A, low power, translator and booster
   stations; translator receive operations; fixed broadcast auxiliary
   service links; private land mobile service/commercial radio service
   (PLMRS/CMRS) operations; offshore radiotelephone service; and cable
   system head-ends. In addition, protection shall be provided in border
   areas near Canada and Mexico in accordance with § 15.712(g).

   (2) For low power auxiliary services authorized pursuant to § § 74.801
   through 74.882 of this chapter, including wireless microphones, a TVBD
   shall rely on the geo-location and database access mechanism to
   identify available television channels to provide interference
   protection to registered locations of such operations, consistent with
   the requirements of § 15.712, and shall rely on spectrum sensing to
   identify available television channels to provide interference
   protection to all other operations.

   (b) Geo-location and database access . (1) The geographic coordinates
   of a fixed TVBD shall be determined to an accuracy of +-50 meters by
   either an incorporated geo-location capability or a professional
   installer. In the case of professional installation, the party who
   registers the fixed TVBD in the database will be responsible for
   assuring the accuracy of the entered coordinates. The geographic
   coordinates of a fixed TVBD shall be determined at the time of
   installation and first activation from a power-off condition, and this
   information may be stored internally in the TVBD. If the fixed TVBD is
   moved to another location or if the stored coordinates become altered,
   the operator shall re-establish the device's:

   (i) Geographic location and store this information in the TVBD either
   by means of the device's incorporated geo-location capability or
   through the services of a professional installer; and

   (ii) Registration with the database based on the device's new
   coordinates.

   (2) A Mode II personal/portable device shall incorporate a geo-location
   capability to determine its geographic coordinates to an accuracy of
   +-50 meters. The device must re-establish its position each time it is
   activated from a power-off condition.

   (3)(i) Fixed devices must access a TV bands database over the Internet
   to determine the TV channels that are available at their geographic
   coordinates prior to their initial service transmission at a given
   location. Operation is permitted only on channels that are indicated in
   the database as being available for TVBDs. Fixed TVBDS shall access the
   database at least once a day to verify that the operating channels
   continue to remain available. Operation must cease immediately if the
   channel is no longer available.

   (ii) Mode II personal/portable devices must access a TV bands database
   over the Internet to determine the TV channels that are available at
   their geographic coordinates prior to their initial service
   transmission at a given location. Operation is permitted only on
   channels that are indicated in the database as being available for
   TVBDs. A Mode II personal/portable device must access the database for
   a list of available channels each time it is activated from a power-off
   condition and re-check its location and the database for available
   channels if it changes location during operation. A Mode II
   personal/portable device that has been in a powered state shall
   re-check its location and access the database daily to verify that the
   operating channel(s) continue to be available.

   (iii) If a fixed or mode II TVBD fails to contact the TV bands database
   during any given day, it may continue to operate until 11:59 PM of the
   following day at which time it must cease operations unless it has
   contacted the TV bands database during the intervening period.

   (iv) Personal/portable devices operating in Mode I shall obtain a list
   of channels on which they may operate from a master device.

   (4) All geographic coordinates shall be referenced to the North
   American Datum of 1983 (NAD 83).

   (c) Spectrum sensing --(1) Detection threshold. (i) All fixed and
   personal/portable TVBDs must be capable of detecting ATSC digital TV,
   NTSC analog TV and wireless microphone signals using analog or digital
   modulation methods. The required detection thresholds are.

   (A) ATSC signals: -114 dBm, averaged over a 6 MHz bandwidth;

   (B) NTSC signals: -114 dBm, averaged over a 100 kHz bandwidth;

   (C) Wireless microphone signals: -114 dBm, averaged over a 200 kHz
   bandwidth. (ii) The detection thresholds are referenced to an
   omnidirectional receive antenna with a gain of 0 dBi. If a receive
   antenna with a minimum directional gain of less than 0 dBi is used, the
   detection threshold shall be reduced by the amount in dB that the
   minimum directional gain of the antenna is less than 0 dBi. Minimum
   directional gain shall be defined as the antenna gain in the direction
   and at the frequency that exhibits the least gain. Alternative
   approaches for the sensing antenna are permitted, e.g. , electronically
   rotateable antennas, provided the applicant for equipment authorization
   can demonstrate that its sensing antenna provides at least the same
   performance as an omnidirectional antenna with 0 dBi gain.

   (2) Low power auxiliary device channel availability check time. A TVBD
   may start operating on a TV channel if no wireless microphone or other
   low power auxiliary device signals above the detection threshold are
   detected within a minimum time interval of 30 seconds.

   (3) TV channel availability check time. A TVBD is required to check for
   TV signals for a minimum time interval of 30 seconds. If a TV signal is
   detected on a channel indicated as available for use by the database
   system, the device will provide a notice of that detection to the
   operator of the device and a means for the operator to optionally
   remove the channel from the device's list of available channels.

   (4) In-service monitoring. A TVBD must perform in-service monitoring of
   an operating channel a minimum of once every 60 seconds. There is no
   minimum channel availability check time for in-service monitoring.

   (5) Channel move time. After a wireless microphone or other low power
   auxiliary device signal is detected on a TVBD operating channel, all
   transmissions by the TVBD must cease within two seconds.

   (6) Personal/portable devices operating in the client mode shall
   identify to the fixed or Mode II personal/portable device those
   television channels on which it senses any signals above the detection
   threshold. The fixed or Mode II device shall respond in accordance with
   the provisions of this paragraph as if it had detected the signal
   itself.

   (7) TVBDs communicating either directly with one another or linked
   through a base station must share information on channel occupancy
   determined by sensing. If any device in a local area group or network
   determines that a channel is occupied, all other linked devices will
   also be required to respond in accordance with the provisions of this
   paragraph as if it had detected the signal itself.

   (d) A TVBD must incorporate the capability to display a list of
   identified available channels and its operating channels.

   (e) Fixed TVBDs shall transmit identifying information. The
   identification signal must conform to a standard established by a
   recognized industry standards setting organization. The identification
   signal shall carry sufficient information to identify the device and
   its geographic coordinates.

   (f) If a fixed TVBD device does not have a direct connection to the
   Internet and has not yet been initialized and registered with the TV
   bands database, consistent with § 15.713, but can receive the
   transmissions of another fixed TVBD, the device needing initialization
   may transmit to that other device on either a channel that the other
   TVBD has transmitted on or on a channel which the other TVBD indicates
   is available for use to access the database to register its location
   and receive a list of channels that are available for it to use.
   Subsequently, the newly registered TVBD must only use the television
   channels that the database indicates are available for it to use. Such
   fixed devices must re-contact the database through another fixed device
   to review their list of available channels at least once every 60
   seconds. A fixed device may not operate as a client to another fixed
   device.

   (g) A personal/portable TVBD operating in Mode I may only transmit upon
   receiving the transmissions of fixed or Mode II TVBD. A
   personal/portable device operating in Mode I may transmit on either an
   operating channel of the fixed or Mode II TVBD or on a channel the
   fixed or Mode II TVBD indicates is available for use.