Sec. 21.902  Interference.

    (a) All applicants, conditional licensees, and licensees shall make 
exceptional efforts to avoid harmful interference to other users and to 
avoid blocking potential adjacent channel use in the same city and 
cochannel use in nearby cities. In areas where major

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cities are in close proximity, careful consideration should be given to 
minimum power requirements and to the location, height, and radiation 
pattern of the transmitting antenna. Licensees, conditional licensees, 
and applicants are expected to cooperate fully in attempting to resolve 
problems of potential interference before bringing the matter to the 
attention of the Commission.
    (b) As a condition for use of frequency in this service, each 
applicant, conditional licensee, and licensee is required to:
    (1) Not enter into any lease or contract or otherwise take any 
action that would unreasonably prohibit location of another station's 
transmitting antenna at any given site inside its own protected service 
area.
    (2) Cooperate fully and in good faith to resolve interference and 
transmission security problems.
    (3) Engineer the system to provide at least 45 dB of cochannel 
interference protection within the 56.33 km (35 mile) protected service 
area of any authorized or previously-proposed ITFS or incumbent MDS 
station, and at each previously-registered ITFS receive site registered 
as of September 17, 1998 (or the appropriate value for bandwidths other 
than 6 MHz.)
    (4) Engineer the station to provide at least 0 dB of adjacent 
channel interference protection within the 56.33 km (35 mile) protected 
service area of any authorized or previously-proposed ITFS or incumbent 
MDS station, and at each previously-registered ITFS receive site 
registered as of September 17, 1998 (or the appropriate value for 
bandwidths other than 6 MHz.)
    (5)(i) Engineer the station to limit the calculated free space power 
flux density to -73 dBW/m \2\ (or the appropriate value for bandwidth 
other than 6 MHz) at the boundary of a 56.33 km (35 mile) protected 
service area, where there is an unobstructed signal path from the 
transmitting antenna to the boundary; or alternatively, obtain the 
written consent of the entity authorized for the adjoining area to 
exceed the -73 dBW/m \2\ limiting signal strength at the common 
boundary.
    (ii) In determining signal path conditions, the following shall be 
used: a 9.1 meter (30 feet) receiving antenna height, the transmitting 
antenna height, terrain elevations and 4/3 earth radius propagation 
conditions.
    (6) If a proposed station is within 80 km (50 miles) of the Canadian 
or Mexican border, the station must be designed to meet the requirements 
set forth in international treaties.
    (7) Notwithstanding the above, main, booster and response stations 
shall use the following formulas, as applicable, for determining 
compliance with: (1) Radiated field contour limits where bandwidths 
other than 6 MHz are employed at stations utilizing digital emissions; 
and (2) Cochannel and adjacent channel D/U ratios where the bandwidths 
in use at the interfering and protected stations are unequal and both 
stations are utilizing digital modulation or one station is utilizing 
digital modulation and the other station is utilizing either 6 MHz NTSC 
analog modulation or 125 kHz analog modulation (I channels only).
    (i) Contour limit: -73 dBW/m\2\ + 10 log(X/6) dBW/m\2\, where X is 
the bandwidth in MHz of the digital channel.
    (ii) Co-channel D/U: 45 dB + 10 log(X1/X2) dB, 
where X1 is the bandwidth in MHz of the protected channel and 
X2 is the bandwidth in MHz of the interfering channel.
    (iii) Adjacent channel D/U: 0 dB + 10 log(X1/
X2), dB where X1 is the bandwidth in MHz of the 
protected channel and X2 is the bandwidth in MHz of the 
interfering channel.
    (c) The following interference studies must be prepared:
    (1) An analysis of the potential for harmful interference within the 
56.33 km (35 mile) protected service areas of any authorized or 
previously proposed incumbent station:
    (i) If the coordinates of the applicant's proposed transmitter are 
within 160.94 km (100 miles) of the center coordinates of any authorized 
or previously proposed incumbent station with protected service area of 
56.33 km (35 miles) as specified in Sec. 21.902(d); or
    (ii) If the great circle path between the applicant's proposed 
transmitter and the protected service area of any authorized, or 
previously-proposed, cochannel or adjacent-channel station(s) is within 
241.4 kilometers or less and 90

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percent or more of the path is over water or within 16.1 kilometers of 
the coast or shoreline of the Atlantic Ocean, the Pacific Ocean, the 
Gulf of Mexico, any of the Great Lakes, or any bay associated with any 
of the above (see Secs. 21.901(a) and 74.902 of this chapter);
    (2) Applicants may design interference studies in any manner that 
demonstrates the avoidance of harmful interference, as defined in this 
subpart.
    (i) In lieu of interference studies, applicants may submit in 
accordance with Sec. 21.938 a written statement of no objection to the 
operation of the MDS station.
    (ii) The Commission may direct applicants to submit interference 
studies of a specific nature.
    (3) Except for new stations proposed in applications filed after 
September 15, 1995, in the case of a proposal to operate a non-colocated 
station within the protected service area of an authorized, or 
previously proposed, adjacent channel station, an analysis that 
identifies the areas within the protected service areas of both the 
authorized or previously proposed adjacent channel station and the 
proposed station that cannot be protected as specified in 
Sec. 21.902(b)(4) and an explanation of why the proposed station cannot 
be colocated with the existing or previously proposed station.
    (4) In the case of a proposal for use of channel 2, an analysis of 
the potential for harmful interference with any authorized point-to-
point station located within 80.5 kilometers (50 miles) which utilizes 
the 2160-2162 MHz band; and
    (d)(1) Subject to the limitations contained in paragraph (e) of this 
section, each MDS station licensee shall be protected from harmful 
electrical interference, as determined by the theoretical calculations, 
within a protected service area of which the boundary will be 56.3255 
kilometers (35 miles) from the transmitter site.
    (2) As of September 15, 1995, the location of these protected 
service area boundaries shall become fixed. The center of the circular 
area shall be the geographic latitude and longitude of the transmitting 
antenna site specified in station authorizations or previously proposed 
applications filed at the Commission before September 15, 1995. 
Subsequent transmitter site changes will not change the location of the 
56.3255 kilometers (35 mile) protected service area boundaries.
    (e) No MDS licensee will be protected from harmful interference 
caused by:
    (1) Any station with an earlier filing date.
    (2) Any station that was authorized before July 1984.
    (3) Any multichannel MDS station whose application was pending on 
September 9, 1983.
    (f) In addressing potential harmful interference in this service, 
the following definitions, procedures and other criteria shall apply:
    (1) Cochannel interference is defined as the ratio of the desired 
signal to the undesired signal present in the desired channel, at the 
output of a reference receiving antenna oriented to receive the maximum 
desired signal. Harmful interference will be considered present when a 
calculation using a terrain sensitive signal propagation model 
determines that this ratio is less than 45 dB (or the appropriate value 
for bandwidths other than 6 MHz.)
    (2) Adjacent channel interference is defined as the ratio of the 
desired signal to undesired signal present in an adjacent channel, at 
the output of a reference receiving antenna oriented to receive the 
maximum desired signal level.
    (i) Harmful interference will be considered present when a 
calculation using a terrain sensitive model determines that this ratio 
is less than 0dB (or the appropriate value for bandwidths other than 6 
MHz.)
    (ii) In the alternative, harmful interference will be considered 
present for an ITFS station constructed before May 26, 1983, when a 
calculation using a terrain-sensitive propagation model determines that 
this ratio is less than 10 dB (or the appropriate value for bandwidths 
other than 6 MHz.) unless:
    (A) The individual receive site under consideration has been 
subsequently upgraded with up-to-date reception equipment, in which case 
the ratio shall be less than 0 dB. Absent information presented to the 
contrary, however, the Commission will assume that

[[Page 70]]

reception equipment installation occurred simultaneously with original 
station equipment; or
    (B) The license for an MDS station is conditioned on the proffer to 
the affected ITFS station licensee of equipment capable of providing a 
ratio of 0 dB or more at no expense to the ITFS station licensee, and 
also conditioned, if necessary, on the proffer of installation of such 
equipment; and there has been no showing by the affected ITFS station 
licensee demonstrating good cause and that the proposed equipment will 
not provide a ratio of 0 dB or more, or that installation of such 
equipment, at no expense to the ITFS station licensee, is not possible 
or has not been proffered.
    (3) For purposes of this section all interference calculations 
involving receive antenna performance shall use the reference antenna 
characteristics shown in figure 1.

[[Page 71]]

[GRAPHIC] [TIFF OMITTED] TC01MR91.040

    (4) For purposes of this section, the received signal power level 
(RSL)dBW at the output of the FCC reference receiving antenna 
is obtained from the following formulas (or an equivalent adaptation):

(RSL)dBW=(EIRP)dBW-
    (LFS)dB+(GAR)dB
where the free space loss (LFS) is

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(LFS)dB=20 log (4d/)dB

in which the parameters are defined as follows:

(RSL)dBW is the received power in decibels referenced to one 
watt.
(EIRP)dBW is the equivalent isotropically radiated power in 
decibels above one watt.
d is the distance of the signal path in meters.
[lambda] is the wavelength of the signal in meters.
GAR is the dB gain of the reference receiving antenna above 
an isotropic antenna (obtained from Figure 1 of this section.)

    (5) A determination of signal path conditions shall use a 9.1 meters 
(30 feet) receiving antenna height, the transmitting antenna height, 
terrain elevation, and assume 4/3 earth radius propagation conditions.
    (6) An application will not be accepted for filing if cochannel or 
adjacent channel interference is predicted at the boundary of the 56.33 
km (35 mile) protected service area of an authorized or previously 
proposed incumbent station based on the following criteria:
    (i) Interference calculations shall be made only for directions 
where there is an unobstructed signal path from the site of a proposed 
station to the boundary of any protected area.
    (ii) Calculations of received power levels in units of dBW from the 
proposed station will be made at one degree intervals around the 
protected service area.
    (iii) The assumed value of the desired signal level at the boundary 
of an incumbent station shall be -83 dBW, which is the calculated 
received power in free space at a distance of 56.33 km (35 miles), given 
at EIRP of 2000 watts and a receiver antenna gain of 20 dBi.
    (iv) Harmful interference will be considered to occur at locations 
along the boundary wherever the ratio between the desired signal level 
of -83 dBw and the received power from a proposed cochannel or adjacent 
channel station is less than 45 dB or 0 dB for cochannel or adjacent 
channel proposals, respectively.
    (7) Alternatively, MDS applications will be accepted on the basis of 
an executed written interference agreement between potentially affected 
parties filed in accordance with Sec. 21.938.
    (g)(1) All interference studies prepared pursuant to paragraph (c) 
of this section must be served on all licensees, conditional licensees, 
and applicants for the stations required to be studied by this section. 
This service must include a copy of the FCC application and occur on or 
before the date the application is filed with the Commission.
    (2) MDS licensees, conditional licensees and applicants of 
facilities with 56.33 km (35 mile) protected service areas shall notify 
in writing the holders of authorizations for adjoining BTAs or PSAs of 
application filings for modified station licenses, provided the proposed 
facility would produce an unobstructed signal path to any location 
within the adjoining BTA or PSA. This service must include a copy of the 
FCC application and occur on or before the date the application is filed 
with the Commission.
    (h) For purposes of Sec. 21.31(a), an MDS application, except for 
those applications filed on or after September 15, 1995, filed for a 
facility that would cause harmful electrical interference within the 
protected service area of any authorized or previously proposed station 
will be presumed to be mutually exclusive with the application for such 
authorized or previously proposed station.
    (i)(1) For each application for a new station, or amendment thereto, 
proposing MDS facilities, filed on October 1, 1995, or thereafter, on or 
before the day the application or amendment is filed, the applicant must 
prepare an analysis demonstrating that operation of the MDS applicant's 
transmitter will not cause harmful electrical interference to each 
receive site registered as of September 17, 1998, nor within a protected 
service area as defined in paragraph (d)(1) of this section, of any 
cochannel or adjacent channel ITFS station licensed, with a conditional 
license, or proposed in a pending application on the day such MDS 
application is filed, with an ITFS transmitter site within 50 miles of 
the coordinates of the MDS station's proposed transmitter site.
    (2) For each application described in paragraph (i)(1) of this 
section, the applicant must serve, by certified mail, return receipt 
requested, on or before the day the application or amendment

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described in paragraph (i)(1) of this section is filed initially with 
the Commission, a copy of the complete MDS application or amendment, 
including each exhibit and interference study, described in paragraph 
(i)(1) of this section, on each ITFS licensee, conditional licensee, or 
applicant described in paragraph (i)(1) of this section.
    (3) For each application described in paragraph (i)(1) of this 
section, the applicant must certify and file, with the application or 
amendment, its certification of its compliance with the requirements of 
paragraph (i)(2) of this section.
    (4) For each application described in paragraph (i)(1) of this 
section, the applicant must file with the Commission in Washington, DC, 
on or before the 30th day after the application or amendment described 
in paragraph (i)(1) of this section is filed initially with the 
Commission, a written notice which contains the following:
    (i) Caption--ITFS Service Notice;
    (ii) Applicant's name, address, proposed service area and channel 
group, and application file number, if known;
    (iii) A list of each ITFS licensee and conditional licensee 
described in paragraph (i)(1) of this section;
    (iv) The address used for service to each ITFS licensee and 
conditional licensee described in paragraph (i)(1) of this section; and
    (v) A list of the date each ITFS licensee and conditional licensee 
described in paragraph (i)(1) of this section received a copy of the 
complete application or amendment described in paragraph (i)(1) of this 
section; or a notation of lack of receipt by the ITFS licensee or 
conditional licensee of a copy of the complete application or amendment, 
on or before such 30th day, together with a description of the 
applicant's efforts for receipt by each such licensee or conditional 
licensee lacking receipt of the application.
    (5) The public notices described in paragraph (i)(6) of this section 
are as follows:
    (i) For initial applications for new MDS stations which participate 
in a lottery, this public notice is the notice announcing the selection 
of the applicant's application by lottery for qualification review.
    (ii) For initial applications for new MDS stations which participate 
in a competitive bidding process, this public notice is the notice 
announcing the application of the winning bidder in the competitive 
bidding process has been accepted for filing.
    (iii) For initial applications for new MDS stations which do not 
participate in a lottery or a competitive bidding process, this public 
notice is the notice announcing that the applicant's application is not 
mutually-exclusive with other MDS applications.
    (iv) For MDS modification applications, this public notice is the 
notice announcing that the modification application has been accepted 
for filing.
    (6)(i) Notwithstanding the provisions of Sections 1.824(c) and 
21.30(a)(4), for each application described in paragraph (i)(1) of this 
section, each ITFS licensee and each ITFS conditional licensee described 
in paragraph (i)(1) of this section may file with the Commission, on or 
before the 30th day after the public notice described in paragraph 
(i)(5) of this section, a petition to deny the MDS application.
    (ii) Except for the requirements as to the filing time deadline, 
this petition to deny must otherwise comply with the provisions of 
Section 21.30.
    (iii) In addition, this ITFS petition to deny must:
    (A) Identify the subject MDS application, including the applicant's 
name, station location, channel group, and application file number;
    (B) Include a certificate of service demonstrating service on the 
subject MDS applicant by certified mail, return receipt requested, on or 
before the 30th day after the MDS public notice described in paragraph 
(i)(5) of this section;
    (C) Include a demonstration that it made efforts to reach agreement 
with the MDS applicant but was unable to do so;
    (D) Include an engineering analysis that operation of the proposed 
MDS station will cause harmful interference to its ITFS station;
    (E) Include a demonstration, in those cases in which the MDS 
applicant's analysis is dependent upon modification(s) to the ITFS 
facility, that the harmful interference cannot be avoided

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by the proposed substitution of new or modified equipment to be supplied 
and installed by the MDS applicant, at no expense to the ITFS licensee 
or conditional licensee; and
    (F) Be limited to raising objections concerning the potential for 
harmful interference to its ITFS station, or concerning a failure by the 
MDS applicant to serve the ITFS licensee or conditional licensee with a 
copy of the complete application or amendment described in paragraph 
(i)(1) of this section.
    (iv) The Commission will presume an ITFS licensee or conditional 
licensee described in paragraph (i)(1) of this section has no objection 
to operation of the MDS station, if the ITFS licensee or conditional 
licensee fails to file a petition to deny by the deadline prescribed in 
paragraph (i)(6)(i) of this section.
    (j) If the initial application for facilities in the 2596-2644 
frequency band was filed on September 9, 1983, an applicant proposing to 
modify such facilities must include with its modification application:
    (1) An analysis demonstrating that the modification will not 
increase the size of the geographic area suffering harmful interference 
within the protected service area of existing or proposed co-channel or 
adjacent-channel facilities in the 2596-2644 MHz frequency band with a 
transmitter site within 80.5 km (50 miles) of the modifying station's 
transmitter site of the initial application for the interfered-with 
station was filed on September 9, 1983; and
    (2) An analysis demonstrating that the modification will not cause 
harmful interference to any new portion of the protected service area of 
existing or proposed co-channel or adjacent-channel facilities in the 
2596-2644 frequency band with a transmitter site within 80.5 km (50 
miles) of the modifying station's transmitter site, if the initial 
application for the interfered-with station was filed on September 9, 
1983.
    (k) If an initial application for facilities in the 2596-2644 
frequency band was filed on September 9, 1983, a licensee proposing to 
modify a constructed station may request exclusion from the interference 
analysis prescribed at Sec. 21.902(c) (1) and (2) with respect to 
another specified application for E or F channel facilities, if the 
modifying licensee files as part of its modification application a 
demonstration that:
    (1) The MDS application for which exclusion is requested was 
proposed by an initial application filed on September 9, 1983;
    (2) The MDS application for which exclusion is requested is not yet 
perfected by the submission of the information necessary for processing, 
as of the date of filing of the modification application; and
    (3) A copy of the licensee's modification application, including the 
demonstration specified in this paragraph, was served on the MDS 
applicant for which exclusion is requested, on or before the date of 
filing of the modification application.
    (l) Specific rules relating to response station hubs, booster 
stations, and 125 kHz channels are set forth in Secs. 21.909, 21.913, 
21.940, 74.939 of this chapter, 74.940 of this chapter and 74.985 of 
this chapter. To the extent those specific rules are inconsistent with 
any rules set forth above, those specific rules shall control.
    (m) The following information formats and storage media are to be 
used in connection with applications for new and modified MDS and ITFS 
stations:
    (1) The data file prepared for submission to the Commission's 
Reference Room pursuant to the requirements set out at paragraph 74 of 
Appendix D to the Report and Order in MM Docket 97-217, FCC 98-231, must 
be in ASCII format on either CD-ROMs or 3.5[sec] diskettes. Any 
supplementary information submitted in connection with Appendix D may be 
in either ASCII or PDF format (graphics must be in PDF format) on either 
CD-ROMs or 3.5[sec] diskettes. Applicants serving such data/information 
on other applicants and/or licensees should do so using the same 
format(s) and media as used in their submission to the Commission's 
Reference Room.
    (2) Demonstrations and certifications prepared for submission to the 
Commission's Reference Room may be in either hard copy or in ASCII or 
PDF format on CD-ROM's or 3.5[sec] diskettes.

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(Graphics must be either hard copy or PDF format) Applicants serving 
such demonstrations and certifications on other applicants and/or 
licensees should do so using the same format(s) and media as used in 
their submission to the Commission's Reference Room.

[ 44 FR 60534 , Oct. 19, 1979, as amended at  48 FR 33901 , July 26, 1983; 
 49 FR 25479 , June 21, 1984;  52 FR 27556 , July 22, 1987;  55 FR 46010 , 
Oct. 31, 1990;  56 FR 57598 , Nov. 13, 1991;  56 FR 57818 , Nov. 14, 1991; 
 56 FR 65191 , Dec. 16, 1991;  58 FR 11798 , Mar. 1, 1993;  58 FR 44895 , Aug. 
25, 1993;  60 FR 36553 , July 17, 1995;  60 FR 36739 , July 18, 1995;  60 FR 57367 , Nov. 15, 1995;  61 FR 18098 , Apr. 24, 1996;  61 FR 26676 , May 28, 
1996;  63 FR 65102 , Nov. 25, 1998;  64 FR 63731 , Nov. 22, 1999;  65 FR 46617 , July 31, 2000]

    Effective Date Note: At  65 FR 46617 , July 31, 2000, Sec. 21.902 was 
amended by adding paragraph (m). This paragraph contains information 
collection and recordkeeping requirements and will not become effective 
until approval has been given by the Office of Management and Budget.