Sec.  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
    Sec. 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  Sec. 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   Sec. 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  Sec. 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]