Goto Section: 15.709 | 15.712 | Table of Contents
Revised as of October 1, 2009
Goto Year:2008 |
§ 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
(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
(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
(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.
Goto Section: 15.709 | 15.712
Goto Year: 2008 |
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