IEC 61108-6:2023

IEC 61108-6 ®
Edition 1.0 2023-02
INTERNATIONAL
STANDARD
Maritime navigation and radiocommunication equipment and systems – Global
navigation satellite systems (GNSS) –
Part 6: Navigation with Indian constellation (NavIC)/Indian regional navigation
satellite system (IRNSS) – Receiver equipment – Performance requirements,
methods of testing and required test results

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IEC 61108-6 ®
Edition 1.0 2023-02
INTERNATIONAL
STANDARD
Maritime navigation and radiocommunication equipment and systems – Global

navigation satellite systems (GNSS) –

Part 6: Navigation with Indian constellation (NavIC)/Indian regional navigation

satellite system (IRNSS) – Receiver equipment – Performance requirements,

methods of testing and required test results

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.060; 47.040; 47.060 ISBN 978-2-8322-6363-1

– 2 – IEC 61108-6:2023 © IEC 2023
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions . 8
3.2 Abbreviated terms . 8
4 Minimum performance requirements . 9
4.1 Object . 9
4.2 IRNSS/NavIC receiver equipment . 10
4.2.1 Minimum facilities . 10
4.2.2 Configuration . 10
4.2.3 Quality assurance . 10
4.3 Performance of IRNSS/NavIC receiver equipment . 10
4.3.1 General . 10
4.3.2 Equipment interfaces . 11
4.3.3 Accuracy . 12
4.3.4 Acquisition . 12
4.3.5 Protection . 13
4.3.6 Antenna design . 13
4.3.7 Sensitivity and dynamic range . 14
4.3.8 Effects of specific interfering signals . 14
4.3.9 Position update . 14
4.3.10 Differential IRNSS/NavIC input . 15
4.3.11 Navigation warnings and status indications . 15
4.3.12 Output of COG, SOG and UTC . 17
4.3.13 Typical interference conditions . 18
5 Methods of testing and required test results . 18
5.1 Test sites . 18
5.2 Test sequence . 19
5.3 Standard test signals . 19
5.4 Determination of accuracy . 20
5.5 General requirements and presentation requirements . 20
5.5.1 Normal environmental conditions for tests . 20
5.5.2 General requirements . 20
5.5.3 Presentation requirements . 20
5.6 Receiver performance tests . 20
5.6.1 IRNSS/NavIC receiver equipment . 20
5.6.2 Position output. 20
5.6.3 Equipment interfaces . 21
5.6.4 Accuracy . 21
5.6.5 Acquisition . 22
5.6.6 Protection . 23
5.6.7 Antenna design . 23
5.6.8 Sensitivity and dynamic range . 23
5.6.9 Protection from other shipborne transmitters . 24
5.6.10 Position update . 25
5.6.11 Differential IRNSS/NavIC input . 25

5.6.12 Navigational warnings and status indications . 26
5.6.13 Accuracy of COG and SOG. 28
5.6.14 Validity of COG and SOG information . 29
5.6.15 Output of UTC . 29
5.7 Tests for typical RF interference conditions. 29
5.7.1 Simulator conditions . 29
5.7.2 Navigation solution accuracy test . 29
5.7.3 Re-acquisition test . 30
Annex A (normative) Typical IRNSS/NavIC interference environment. 32
A.1 IRNSS/NavIC CW in-band and near-band interference environment . 32
A.2 Band-limited noise-like interference . 33
A.3 Pulsed interference . 34
A.4 IRNSS/NavIC minimum antenna gain . 35
Annex B (normative) Alert management . 36
Bibliography . 37

Figure 1 – Logical interfaces of IRNSS/NavIC receiver . 11
Figure A.1 – CW interference thresholds for IRNSS/NavIC L5 band receivers in steady
state navigation . 33
Figure A.2 – CW interference thresholds for IRNSS/NavIC S band receivers in steady
state navigation . 33
Figure A.3 – Effect of interference bandwidth on interference thresholds for
IRNSS/NavIC receivers (for noise like interference) . 34

Table 1 – Acquisition time limits . 13
Table 2 – RAIM integrity status . 17
Table 3 – Accuracy of COG . 18
Table 4 – RF interference value . 30
Table A.1 – CW interference thresholds for IRNSS/NavIC L5 band receivers in steady-
state navigation . 32
Table A.2 – CW interference thresholds for IRNSS/NavIC S band receivers in
steady‑state navigation . 32
Table A.3 – Interference threshold for band-limited noise-like interference to
IRNSS/NavIC receivers in steady-state navigation . 34
Table A.4 – Interference thresholds for pulsed interference . 35
Table A.5 – IRNSS/NavIC minimum antenna gain . 35
Table B.1 – Required alerts and their classification . 36

– 4 – IEC 61108-6:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MARITIME NAVIGATION AND RADIOCOMMUNICATION EQUIPMENT
AND SYSTEMS – GLOBAL NAVIGATION SATELLITE SYSTEMS (GNSS) –

Part 6: Navigation with Indian constellation (NavIC)/Indian regional
navigation satellite system (IRNSS) – Receiver equipment – Performance
requirements, methods of testing and required test results

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
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Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 61108-6 has been prepared by IEC technical committee 80: Maritime navigation and
radiocommunication equipment and systems. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
80/1055/FDIS 80/1058/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 61108 series, published under the general title Maritime navigation
and radiocommunication equipment and systems – Global navigation satellite systems (GNSS),
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 61108-6:2023 © IEC 2023
MARITIME NAVIGATION AND RADIOCOMMUNICATION EQUIPMENT
AND SYSTEMS – GLOBAL NAVIGATION SATELLITE SYSTEMS (GNSS) –

Part 6: Navigation with Indian constellation (NavIC)/Indian regional
navigation satellite system (IRNSS) – Receiver equipment – Performance
requirements, methods of testing and required test results

1 Scope
This part of IEC 61108 specifies the minimum performance requirements, methods of testing
and required test results for the Indian regional navigation satellite system (IRNSS), also known
as Navigation with Indian Constellation (NavIC), shipborne receiver equipment, based on IMO
resolution MSC.449(99), which uses the signals from NavIC/IRNSS in order to determine
position.
This document takes account of the general requirements given in IMO resolution A.694(17)
and is associated with IEC 60945. When a requirement in this document is different from
IEC 60945, the requirement in this document takes precedence. This document also takes into
account, as appropriate, requirements for the presentation of navigation-related information on
shipborne navigational displays given in IMO resolution MSC.191(79) and is associated with
IEC 62288. This document further takes into account, as appropriate, requirements for bridge
alert management given in IMO resolution MSC.302(87) and is associated with IEC 62923-1.
This document applies to navigation in ocean waters for the standard positioning service and
harbour entrances, harbour approaches and coastal waters, as defined in IMO resolution
A.1046(27) within IRNSS/NavIC coverage area as given in IMO resolution MSC 449(99).
All text of this document whose meaning is identical to that in IMO resolution MSC. 449(99) is
printed in italics and the resolution and paragraph number indicated between brackets, i.e.
"(M.449(99)/A1.2)".
The requirements in Clause 4 are cross-referenced to the tests in Clause 5 and vice versa.
NOTE 1 A description of the IRNSS standard positioning service can be found in the interface control documents
which were officially released in 2017 in the public domain (see ISRO-IRNSS-ICD-SPS-1.1).
NOTE 2 The IRNSS constellation was renamed as "NavIC" (navigation with Indian constellation) in 2016.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60945, Maritime navigation and radiocommunication equipment and systems – General
requirements – Methods of testing and required test results
IEC 61108-4, Maritime navigation and radiocommunication equipment and systems – Global
navigation satellite systems (GNSS) – Part 4: Shipborne DGPS and DGLONASS maritime radio
beacon receiver equipment – Performance requirements, methods of testing and required test
results
IEC 61108-5:2020, Maritime navigation and radiocommunication equipment and systems –
Global navigation satellite systems (GNSS) – Part 5: BeiDou navigation satellite system (BDS)
– Receiver equipment – Performance requirements, methods of testing and required test results
IEC 61162-1, Maritime navigation and radiocommunication equipment and systems – Digital
interfaces – Part 1: Single talker and multiple listeners
IEC 61162-2, Maritime navigation and radiocommunication equipment and systems – Digital
interfaces – Part 2: Single talker and multiple listeners, high-speed transmission
IEC 61162-450, Maritime navigation and radiocommunication equipment and systems – Digital
interfaces – Part 450: Multiple talkers and multiple listeners – Ethernet interconnection
IEC 62288, Maritime navigation and radiocommunication equipment and systems –
Presentation of navigation-related information on shipborne navigational displays – General
requirements, methods of testing and required test results
IEC 62923-1, Maritime navigation and radiocommunication equipment and systems – Bridge
alert management – Part 1: Operational and performance requirements, methods of testing and
required test results
IEC 62923-2, Maritime navigation and radiocommunication equipment and systems – Bridge
alert management – Part 2: Alert and cluster identifiers and other additional features
IMO resolution A.694(17):1991, General requirements for shipborne radio equipment forming
part of the Global maritime distress and safety system (GMDSS) and for electronic navigational
aids
IMO resolution A.915(22), Revised maritime policy and requirements for a future Global
Navigation Satellite System (GNSS)
IMO resolution A.1046(27), Worldwide radio navigation system
IMO resolution MSC.302(87), Performance standards for bridge alert management
IMO resolution MSC.449(99), Performance Standards for Shipborne IRNSS Receiver
Equipment
ITU-R Recommendation M.823-3, Technical characteristics of differential transmissions for
global navigation satellite systems from maritime radio beacons in the frequency band
283.5-315 kHz in Region 1 and 285-325 kHz in Regions 2 and 3
ISRO-IRNSS-ICD-SPS-1.1, Navigation with Indian Constellation System – Signal in Space
Interface Control Document for Standard Positioning Service V 1.1, Aug 2017 [viewed
2022-11-11]. Available at
https://www.isro.gov.in/media_isro/pdf/Publications/Vispdf/Pdf2017/irnss_sps_icd_version1.1-
2017.pdf
RTCM 10402, RTCM Recommended Standards for Differential GNSS (Global Navigation
Satellite Systems) Service
– 8 – IEC 61108-6:2023 © IEC 2023
3 Terms, definitions and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
NOTE All definitions and abbreviations used are the same as those used in ISRO-IRNSS-ICD-SPS-1.1.
3.1 Terms and definitions
3.1.1
integrity
ability of the system to provide users with warnings within a specified time when the system
should not be used for navigation
3.1.2
Indian regional navigation satellite system
IRNSS
independent satellite navigation system developed and operated by India
Note 1 to entry: IRNSS can provide 3D position, velocity and time information for users within 1 500 km from the
Indian geopolitical boundary.
Note 2 to entry: IRNSS is known as NavIC and the words are used interchangeably in this document.
3.1.3
IRNSS/NavIC time
time reference built and kept by IRNSS
nd
Note 1 to entry: The IRNSS system time start epoch is 00:00 UT on Sunday August 22 1999 (midnight between
st nd
August 21 and 22 ). At the start epoch, IRNSS system time is ahead of UTC by 13 leap seconds (i.e. IRNSS time,
nd st
August 22 1999, 00:00:00 corresponds to UTC time August 21 1999, 23:59:47).
3.2 Abbreviated terms
BAM bridge alert management
CAM central alert management
COG course over ground
CW continuous wave
DNavIC differential navigation with Indian constellation
EUT equipment under test
GNSS global navigation satellite system
GPS global positioning system
HAL horizontal alert limit
HDOP horizontal dilution of precision
HPL horizontal protection limit
ICD interface control document
MKD minimum keyboard and display
NavIC navigation with Indian constellation
NB narrow band
NPLI national physical laboratory of India

PDOP position dilution of precision
PNT position navigation and timing
RAIM receiver autonomous integrity monitor
RF radio frequency
RFCS radio frequency constellation simulator
RFI radio frequency interference
SOG speed over ground
SPS standard positioning service
UTC universal time coordinated
WB wide band
4 Minimum performance requirements
4.1 Object
(M.449(99)/A1.2) The IRNSS Standard Positioning Service (SPS) provides positioning,
navigation and timing services, free of direct user charges. The IRNSS SPS receiver equipment
should be capable of receiving and processing the IRNSS SPS signal. It should be capable of
tracking all IRNSS satellites.
(M.449(99)/A1.3) Receiver equipment for the Indian Regional Satellite System (IRNSS)
intended for navigational purposes on ships with maximum speeds not exceeding 70 knots shall,
in addition to the general requirements contained in resolution A.694(17), comply with the
following minimum performance requirements.
(M.449(99)/A1.4) This standard covers the basic requirements of position fixing, determination
of course over ground (COG), speed over ground (SOG) and timing either for navigation
purposes or as input to other functions. The standards do not cover other computational
facilities which may be in the equipment nor cover the requirements for other systems that may
take input from the IRNSS receiver.
This document contains the basic minimum performance requirements for use of IRNSS/NavIC
standard positioning service (SPS) signals for navigational position fixing, including differential
corrections, and, in addition, for the determination of speed and direction of the movement of
the antenna over the ground.
Other computational activity, input/output activity or extra display functions which may be
provided shall not degrade the performance of the equipment below the minimum performance
requirements set out in this document.
The IRNSS/NavIC receiver equipment shall comply with:
– the provisions of IMO resolutions A.1046(27), MSC. 449(99), MSC.302(87) and A.694(17);
– the accuracy requirements of the SPS interface control document;
– tests in accordance with IEC 60945.

– 10 – IEC 61108-6:2023 © IEC 2023
4.2 IRNSS/NavIC receiver equipment
4.2.1 Minimum facilities
(M.449(99)/A2.1) The term "IRNSS receiver equipment" as used in these performance
standards includes all the components and units necessary for the system to properly perform
its intended functions. The equipment shall include the following minimum facilities:
a) antenna capable of receiving IRNSS signals;
b) IRNSS receiver and processor;
c) means of accessing the computed latitude/longitude position;
d) data control and interface; and
e) position display and, if required, other forms of output.
If the IRNSS/NavIC receiver forms part of an approved integrated navigation system (INS),
requirements of c), d) and e) may be provided within the INS.
If the IRNSS/NavIC receiver forms part of an approved multi-system PNT, requirements of c),
d) and e) may be provided within the multi-system PNT.
4.2.2 Configuration
The IRNSS/NavIC receiver equipment may be supplied in one of several configurations to
provide the necessary position information. Examples are as follows:
– stand-alone receiver with means of accessing computed position via a keyboard with the
positional information suitably displayed and with means to display alerts and acknowledge
alerts via the keyboard;
– IRNSS/NavIC black box receiver fed with operational parameters from external
devices/remote locations and feeding an integrated system with means of access to the
computed position via an appropriate interface, and the positional information and alert
management information available to at least one remote location. With this option, a
separate user interface called as MKD shall be provided as a backup;
– as one of the position velocity and time (PVT) methods included in a multi-system PNT
equipment based on IMO resolution MSC.401(95).
The above examples should not be implied as limiting the scope of future development.
4.2.3 Quality assurance
The equipment shall be designed, produced and documented by manufacturers complying with
approved quality systems as applicable.
4.3 Performance of IRNSS/NavIC receiver equipment
4.3.1 General
(See 5.6.2)
(M.449(99)/A3.1) The IRNSS receiver equipment shall be capable of receiving and processing
the IRNSS SPS positioning and velocity, and timing signals, and shall use the ionospheric
model broadcast to the receiver by the constellation to generate ionospheric corrections.
A detailed description of the IRNSS/NavIC navigation signal characteristics is given in ISRO-
IRNSS-ICD-SPS-1.1, Aug 2017.
(M.449(99)/A3.2) The IRNSS receiver equipment shall provide position information based upon
WGS-84 and should be in accordance with international standards.

Means may be provided to transform the computed position based upon WGS-84 into data
compatible with the datum of the navigational chart in use. Where this facility exists, the display
shall indicate that co-ordinate conversion is being performed and shall identify the co-ordinate
system in which the position is expressed.
(M.449(99)/A3.3) The IRNSS receiver equipment shall provide time referenced to universal time
coordinated UTC (NPLI).
4.3.2 Equipment interfaces
(See 5.6.3)
(M.449(99)/A3.4) The IRNSS receiver equipment shall be provided with at least two outputs
from which position information, UTC, course over ground (COG), speed over ground (SOG)
and alarms can be supplied to other equipment. The output of position information shall be
based on the WGS 84 datum and shall be in accordance with international standards. The
output of UTC, course over ground (COG), speed over ground (SOG) and alarms shall be
consistent with the requirements of M.449(99)/A3.16 and M.449(99)/A3.18.
(M.449(99)/A3.17) The IRNSS receiver equipment shall provide at least one normally closed
contact, which shall indicate failure of the IRNSS receiver equipment.
(M.449(99)/A3.18). The IRNSS receiver equipment shall have a bidirectional interface to
facilitate communication so that alarms can be transferred to external systems and so that
audible alarms from the IRNSS receiver can be acknowledged from external systems; the
interface shall comply with relevant international standards.
NOTE Alarms are read as alerts in M.449(99)/A3.4 and A3.18 for BAM compliance.
The physical interface shall be based on IEC 61162-1 or IEC 61162-2 or IEC 61162-450.
Logical interfaces are shown in Figure 1, where required interfaces are indicated with solid lines
and optional interfaces are indicated in dashed lines.

Figure 1 – Logical interfaces of IRNSS/NavIC receiver
IRNSS/NavIC receiver shall use talker ID "GI".
For reporting purposes, the following sentences shall be available in any combination:
• DTM – Datum reference (see IEC 61108-5);
• GBS – GNSS satellite fault detection (see IEC 61108-5);
• GFA – GNSS fix accuracy and integrity (see IEC 61108-5);
• GNS – GNSS fix data (see IEC 61108-5);
• RMC – Recommended minimum specific GNSS data;
• VTG – Course over ground and ground speed;
• ZDA – Time and date.
– 12 – IEC 61108-6:2023 © IEC 2023
If a sentence uses a datum other than WGS 84, then the DTM sentence shall be used in
compliance with IEC 61162-1 or IEC 61108-5, whichever is newer.
For reporting GNSS differential correction data, the following sentence shall be available:
• GDC – GNSS differential correction (see IEC 61108-5).
For alert reporting and alert command purposes, the following sentences shall be available:
• ACN – Alert command;
• ALC – Cyclic alert list;
• ALF – Alert sentence;
• ARC – Alert command refused;
• HBT – Heartbeat supervision sentence.
Alert requirements shall comply with IEC 62923-1 and IEC 62923-2.
In addition, for integrating with other navigational aids, the following sentences may be available
for output in any combination:
• GRS – GNSS range residuals (see IEC 61108-5);
• GSA – GNSS DOP and active satellites (see IEC 61108-5);
• GST – GNSS pseudorange error statistics (see IEC 61108-5);
• GSV – GNSS satellites in view (see IEC 61108-5).
GBS, GRS, GSA, GST and GSV are required to support external integrity checking. They are
synchronized with the corresponding fix data (GNS).
4.3.3 Accuracy
(See 5.6.4)
4.3.3.1 Static position accuracy
(M.449(99)/A3.5) The IRNSS receiver equipment shall have static accuracy such that the
horizontal position of the antenna is determined to within 25 m horizontally (95 %) and 30 m
vertically (95 %).
NOTE The position accuracy with the specified user conditions has been determined to be within 10 m (95 %) as
specified by the IRNSS SPS ICD document. According to ICD, IRNSS provides L5 and S band dual-frequency
services. The IRNSS/NavIC receiver equipment has higher static accuracy for dual frequency operations on L5 and
S frequencies.
4.3.3.2 Dynamic position accuracy
(M.449(99)/A3.6) The IRNSS receiver equipment shall have dynamic accuracy equivalent to the
static accuracy specified in 4.3.3.1 above under the normal sea states and motion experienced
in ships.
4.3.4 Acquisition
(See 5.6.5)
(M.449(99)/A3.9) The IRNSS receiver equipment shall be capable of selecting automatically
the appropriate satellite transmitted signals to determine the ship's position, velocity and time
with the required accuracy and update rate.
(M.449(99)/A3.12) The IRNSS receiver equipment shall be capable of acquiring position,
velocity and time to the required accuracy within 3 min when there is no valid almanac data.

(M.449(99)/A3.13) The IRNSS receiver equipment shall be capable of acquiring position,
velocity and time to the required accuracy within 2 min when there is valid almanac data.
(M.449(99)/A3.14) The IRNSS receiver equipment shall be capable of reacquiring position,
velocity and time to the required accuracy within 1 min when there has been a service
interruption of 60 s or less.
Acquisition is defined as the processing of IRNSS/NavIC satellite signals to obtain a position
fix within the required accuracies.
Three conditions of the IRNSS/NavIC receiver equipment are set out under which the minimum
performance requirements shall be met.
• Condition A
Initialization (cold start) – the equipment has no valid almanac because it has:
– been transported over large distances (> 1 000 km to < 10 000 km) without power or
IRNSS/NavIC signals or by the deletion of the current almanac;
– not been powered for > 7 days;
– not received IRNSS/NavIC signals for > 7 days.
• Condition B
Warm start – the equipment has a valid almanac but there is:
– power outage – the equipment under normal operation loses power for at least 24 h; or
– interruption of IRNSS/NavIC signals – under normal operation, the IRNSS/NavIC signals
receptions are interrupted for at least 24 h, but there is no loss of power.
• Condition C
Brief interruption of power or IRNSS/NavIC signals – under normal operation, the power or
the signals are interrupted for 60 s.
No user action other than applying power and providing a clear view from the antenna for
the IRNSS/NavIC signals shall be necessary, from any of the initial conditions above, in
order to achieve the required acquisition time limits in Table 1.
Table 1 – Acquisition time limits
Equipment condition A B C
Acquisition time limits (min) 3 2 1

4.3.5 Protection
(See 5.6.6)
(M.449(99)/A4) Precautions shall be taken to ensure that no permanent damage can result from
an accidental short circuit or grounding of the antenna or any of its input or output connections
or any of the IRNSS receiver equipment inputs or outputs for a duration of 5 min.
4.3.6 Antenna design
(See 5.6.7)
(M.449(99)/A2.2) The antenna design shall be suitable for fitting at a position on the ship which
ensures a clear view of the satellite constellation, taking into consideration any obstructions
that might exist on the ship.
– 14 – IEC 61108-6:2023 © IEC 2023
4.3.7 Sensitivity and dynamic range
(See 5.6.8)
(M.449(99)/A3.10) The IRNSS receiver equipment shall be capable of acquiring satellite signals
with input signals having carrier levels in the range of –137 dBm to –127 dBm as measured at
the antenna input. Once the satellite signals have been acquired the equipment shall continue
to operate satisfactorily with satellite signals having carrier levels down to –140 dBm as
measured at the antenna input.
4.3.8 Effects of specific interfering signals
(See 5.6.9)
The IRNSS/NavIC receiver equipment shall meet the following requirements.
a) In a normal operating mode, i.e. switched on and with antenna attached, it is subject to
radiation consisting of a burst of 10 pulses, each 1,0 µs to 1,5 µs long on a duty cycle of
1 600:1 at a frequency lying between 2,9 GHz and 3,1 GHz at power density of about
7,5 kW/m . The condition shall be maintained for 10 min with the bursts of pulses repeated
every 3 s. When the unwanted signal is removed and the IRNSS/NavIC receiver antenna is
exposed to the normal IRNSS/NavIC satellite signals, the receiver shall calculate valid
position fixes within 5 min without further operator intervention.
NOTE 1 This condition is approximately equivalent to exposing the antenna to radiation from a 60 kW S band
marine radar operating at a nominal 1,2 µs pulse width at 600 pulses/s using a 4 m slot antenna rotating at
20 r/min with the IRNSS/NavIC antenna placed in the plane of the bore site of the radar antenna at a distance
of 10 m from the centre of rotation.
b) In a normal operating mode, i.e. switched on and with antenna attached, it is subject to
radiation of 0,16 W/m at a frequency in the range of 1 626,5 MHz to 1 660,5 MHz for 10 min.
During the period, the IRNSS/NavIC receiver equipment shall be able to calculate valid
position fixes.
NOTE 2 This is equivalent to exposing a IRNSS/NavIC antenna to radiation from an Inmarsat Fleet Broadband
antenna at 10 m distance along the bore sight.
Advice shall be given in the manual for adequate installation of the antenna unit, to minimize
interference with other radio equipment such as marine radars, Inmarsat ship earth stations,
Iridium ship earth stations, etc.
4.3.9 Position update
(See 5.6.10)
(M.449(99)/A3.15) The IRNSS receiver equipment shall generate and output to a display and
digital interface (conforming to IEC 61162) a new position solution at least once every 1 s for
conventional craft and at least once every 0,5 s for high speed craft.
For high speed craft purposes, the equipment shall additionally provide an IEC 61162-2 or
IEC 61162-450 interface with a position update rate of 2 Hz.
(M.449(99)/A3.7) The IRNSS receiver equipment shall have position resolution equal to or
better than 0,001 min of latitude and longitude.
NOTE AIS receivers require 0,000 1 min of latitude and longitude.

4.3.10 Differential IRNSS/NavIC input
(See 5.6.11)
(M.449(99)/A3.19) The IRNSS receiver equipment shall have the facilities to process differential
IRNSS (DNavIC) data fed to it in accordance with the standards of Recommendation ITU-R
M.823 and an appropriate RTCM standard and provide indication of the reception of DNavIC
signals and whether they are being applied to the ship’s position. When a IRNSS receiver is
equipped with a differential receiver, performance standards for static and dynamic accuracies
(M.449(99)/A3.5 and A3.6) shall be 10 m (95 %).
An integrated DNavIC receiver shall have an ITU-R M.823 compliant asynchronous full duplex
serial input/output port for testing in compliance with IEC 61108-4. The data input/output port
shall be supplied for testing purposes only.
4.3.11 Navigation warnings and status indications
(See 5.6.12)
4.3.11.1 Position
(M.449(99)/A4.1) The IRNSS receiver equipment shall also indicate whether the performance
of IRNSS is outside the bounds of requirements for general navigation in the ocean, coastal,
port approach, restricted waters, and inland waterway phases of the voyage as specified in
either IMO resolution A.1046(27) within IRNSS coverage area or appendix 2 to IMO resolution
A.915(22) and any subsequent amendments, as appropriate.
The IRNSS/NavIC receiver equipment shall as a minimum:
a) (M.449(99)/A4.2.1) provide a warning within 5 s of loss of position or if a new position based
on the information provided by the IRNSS constellation has not been calculated for more
than 1 s for conventional craft and 0,5 s for high-speed craft. Under such conditions the last
known position and the time of last valid fix, with the explicit indication of the state allowing
for no ambiguity, shall be output until normal operation is resumed;
b) display DNavIC messages. The IRNSS receiver either shall have as a minimum the
capability of displaying appropriate DNavIC messages or forwarding those messages in
GDC sentences for display on a remote system;
c) provide an indication of the navigational status.
The navigational status for different position accuracy levels shall be expressed in three
navigational states:
– "safe"
– "caution", and
– "unsafe
The conditions for a "safe" navigational state are as follows:
d) the estimated error (95 % confidence) along the major axis of the error ellipse is less than
the selected accuracy level corresponding to the actual navigation mode; and
e) integrity is available and within the requirements for the actual navigation mode; and
f) a new position has been calculated within 1 s for a conventional craft and 0,5 s for a high
speed craft.
The conditions for a "caution" navigational state are as follows:
g) integrity has not been available for a period of at least 3 s; and/or
h) HDOP exceeded – HDOP exceeds the required threshold; and/or

– 16 – IEC 61108-6:2023 © IEC 2023
i) loss of differential signal or differe
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