§  90.377   Frequencies available; maximum EIRP and antenna height, and
priority communications.

   (a) Licensees shall transmit only the power (EIRP) needed to
   communicate with an On-Board Unit (OBU) within the communications zone
   and must take steps to limit the Roadside Unit (RSU) signal within the
   zone to the maximum extent practicable.

   (b) Frequencies available for assignment to eligible applicants within
   the 5850–5925 MHz band for RSUs and the maximum EIRP permitted for an
   RSU with an antenna height not exceeding 8 meters above the roadway bed
   surface are specified in the table below. Where two EIRP limits are
   given, the higher limit is permitted only for state or local
   governmental entities.
   Channel No. Frequency range
   (MHz) Max. EIRP^1
   (dBm) Channel use
   170 5850–5855 Reserved.
   172 5855–5865 33 Service Channel.^2
   174 5865–5875 33 Service Channel.
   175 5865–5885 23 Service Channel.^3
   176 5875–5885 33 Service Channel.
   178 5885–5895 33/44.8 Control Channel.
   180 5895–5905 23 Service Channel.
   181 5895–5915 23 Service Channel.^3
   182 5905–5915 23 Service Channel.
   184 5915–5925 33/40 Service Channel.^4

   ^1An RSU may employ an antenna with a height exceeding 8 meters but not
   exceeding 15 meters provided the EIRP specified in the table above is
   reduced by a factor of 20 log(Ht/8) in dB where Ht is the height of the
   radiation center of the antenna in meters above the roadway bed
   surface. The EIRP is measured as the maximum EIRP toward the horizon or
   horizontal, whichever is greater, of the gain associated with the main
   or center of the transmission beam. The RSU antenna height shall not
   exceed 15 meters above the roadway bed surface.

   ^2Channel 172 is designated for public safety applications involving
   safety of life and property.

   ^3Channel Nos. 174/176 may be combined to create a twenty megahertz
   channel, designated Channel No. 175. Channels 180/182 may be combined
   to create a twenty-megahertz channel, designated Channel No. 181.

   ^4Channel 184 is designated for public safety applications involving
   safety of life and property. Only those entities meeting the
   requirements of § 90.373(a) are eligible to hold an authorization to
   operate on this channel.

   (c) Except as provided in paragraphs (d) and (e) of this section,
   non-reserve DSRCS channels are available on a shared basis only for use
   in accordance with the Commission's rules. All licensees shall
   cooperate in the selection and use of channels in order to reduce
   interference. This includes monitoring for communications in progress
   and any other measures as may be necessary to minimize interference.
   Licensees of RSUs suffering or causing harmful interference within a
   communications zone are expected to cooperate and resolve this problem
   by mutually satisfactory arrangements. If the licensees are unable to
   do so, the Commission may impose restrictions including specifying the
   transmitter power, antenna height and direction, additional filtering,
   or area or hours of operation of the stations concerned. Further the
   use of any channel at a given geographical location may be denied when,
   in the judgment of the Commission, its use at that location is not in
   the public interest; use of any such channel may be restricted as to
   specified geographical areas, maximum power, or such other operating
   conditions, contained in this part or in the station authorization.

   (d) Safety/public safety priority. The following access priority
   governs all DSRCS operations:

   (1) Communications involving the safety of life have access priority
   over all other DSRCS communications;

   (2) Subject to a control channel priority system management strategy (
   see ASTM E2213–03 DSRC Standard at § 4.1.1.2(4)), DSRCS communications
   involving public safety have access priority over all other DSRC
   communications not listed in paragraph (d)(1) of this section. Roadside
   Units (RSUs) operated by state or local governmental entities are
   presumptively engaged in public safety priority communications.

   (e) Non-priority communications. DSRCS communications not listed in
   paragraph (d) of this section, are non-priority communications. If a
   dispute arises concerning non-priority communications, the licensee of
   the later-registered RSU must accommodate the operation of the early
   registered RSU, i.e. , interference protection rights are
   date-sensitive, based on the date that the RSU is first registered (
   see § 90.375) and the later-registered RSU must modify its operations to
   resolve the dispute in accordance with paragraph (f) of this section.

   (f) Except as otherwise provided in the ASTM–DSRC Standard ( see
   § 90.379) for the purposes of paragraph (e) of this section,
   objectionable interference will be considered to exist when the
   Commission receives a complaint and the difference in signal strength
   between the earlier-registered RSU and the later-registered RSU
   (anywhere within the earlier-registered RSU's communication zone) is 18
   dB or less (co-channel). Later-registered RSUs causing objectionable
   interference must correct the interference immediately unless written
   consent is obtained from the licensee of the earlier-registered RSU.

   [ 71 FR 52749 , Sept. 7, 2006, as amended at  72 FR 35199 , June 27, 2007]