RTCM Paper 244-2013-SC119-169
Radiocommunication Study Groups
Source:
Document 5B/369
Subject:
Annex 23 to Document 5B/304
Preliminary draft new Report
ITU-R M.[MAN OVERBOARD SYSTEM]
Document 5B/TEMP/231-E
28 November 2013
English only
Working Party 5B
(Chairman, Working Group 5B-3)
DRAFT LIAISON STATEMENT TO EUROPEAN TELECOMMUNICATIONS
STANDARDS INSTITUTE (ETSI) TG 26
Introduction
ITU-R Working Party 5B (WP 5B) thanks the European Telecommunications Standards Institute
and the Kingdom of the Netherlands for their contribution in Document 5B/369 commenting on
certain aspects of the preliminary draft new Report ITU-R M.[MAN OVERBOARD SYSTEM]
under consideration by ITU-R WP 5B.
To assist ETSI TG26 in its work in developing its own AIS-MOB technical standard
(EN 303 098-1, Maritime survival locating device - AIS), WP 5B provides the following
information after consideration.
Discussion on AIS-MOB
As ETSI has noted, RTCM standard 11901.1 currently provides for unsynchronised transmission
when in ACTIVE mode, as is also provided in IEC 61097-14 for the AIS-SART, which is a
requirement of the IMO Performance Standard: “The AIS-SART should continue transmission even
if the position and time synchronization from the positioning system is lost or fails.” (refer IMO
Resolution MSC.246(83), (paragraph 2.5).
WP 5B acknowledges the potential for effective interference on the VHF data link (VDL) from an
AIS-MOB device when transmitting unsynchronized, since there is no receiver incorporated in the
AIS-MOB or AIS-SART. Considering however, that the radio coverage area or ‘footprint’ of an
AIS-MOB is small since the antenna elevation is very low, and the unit transmits at low power, and
under sometimes very poor physical conditions. WP 5B considers the impact on the VDL to
limited and acceptable. It is recommended however, that manufacturer’s inclusion design features
that will assist with the minimization of inadvertent activations.
WP 5B does not believe that AIS-MOB transmissions while unsynchronized contradicts the
requirements in Recommendation ITU-R M.1371. Although this Recommendation provides only
for synchronized transmissions, the usage of AIS-SART and AIS-MOB devices in ACTIVE mode
are not standard operational conditions. Considering also, that the impact on the VDL would be
restricted to one additional adjacent time slot for each messaged transmitted, the low duty cycle of
the devices, and the potential for savings lives, this is acceptable. In the case, where a GNSS
Attention: The information contained in this document is temporary in nature and does not necessarily represent material that has been agreed by the
group concerned. Since the material may be subject to revision during the meeting, caution should be exercised in using the document for the
development of any further contribution on the subject.
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RTCM Paper 244-2013-SC119-169
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position has been obtained, and then lost, transmission of the last known position provides useful
information for locating during search and rescue operations.
Conclusion
WP 5B agrees with the ETSI position that AIS-MOB devices while in TEST mode should only
transmit when synchronised with UTC (i.e. via GNSS) after successful UTC lock within
predetermined period of time, which will indicate that the unit is functional.
WP 5B is of the view that AIS-MOB devices while in ACTIVE mode should be capable of
transmitting when unsynchronised with UTC in the case where UTC lock is not achieved via the
integral GNSS receiver.
Preliminary draft new Report ITU-R M.[MAN OVERBOARD SYSTEM]
WP 5B acknowledges that some technical consistencies may be encountered in the preliminary
draft new Report ITU-R M.[MAN OVERBOARD SYSTEM]. The following text has been inserted
into the document (section 2.1):
“When comparing the different man overboard devices and systems described in this
Report, certain parameters or stipulations may appear inconsistent, which is the result of
devices developed under national arrangements, and input contributions from
Administrations to this Report. A possible future Recommendation may codify these
inconsistencies for better classification.”
Multiple active 121.5 MHz beacons
WP 5B acknowledges the advent of modern direction-finding (DF) equipment using phase
discrimination and pseudo-Doppler techniques. Text from Document 5B/439, which raised the
same issue, has been inserted into the preliminary draft new Report (see section 9.4).
Status:
For information
Contact:
Peter POKORNY
E-mail:
Peter.Pokorny@amsa.gov.au
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