IECSTD - Version 3.1

RTCM Paper 082-2008-SC123-047

- iii -RTCM Paper 082-2008-SC123-047

CONTENTS

11Scope

2Normative references1

3Definitions and abbreviations2

3.1Definitions2

3.4Abbreviations2

4General requirements for VDSMS3

4.1Operational modes4

4.2Means for sharing the use of a channel4

4.2.1Determining the availability of a channel4

4.2.2Limiting the use of a channel4

4.3Transmitter emissions spectrum4

4.4Transmitter modulation4

4.5Receiver performance4

5Performance requirements for VDSMS equipment5

5.1General5

5.2Composition5

5.3Operating frequency channels5

5.3.1Primary and secondary channel users5

5.3.2Carrier Sense Time Division Multiple Access (CSTDMA)5

5.4Identification5

5.5VDSMS Message Content6

5.6VDSMS Message Types6

5.7Alarms and indications, fall-back arrangements6

5.7.1Integrity and protection6

5.7.2Transmitter shutdown procedure6

5.86.7 User interface6

5.8.1Indicators and display6

5.8.2MMSI input7

5.8.3External interfaces7

6Technical requirements for VDSMS equipment7

6.1General7

6.2Physical layer8

6.2.1Transceiver characteristics8

6.2.2Transmitter requirements9

6.2.3Receiver requirements10

6.3Link layer10

6.3.1Link sublayer 1: Medium Access Control (MAC)10

6.3.2Link sublayer 2: Data Link Service (DLS)10

6.3.3Link sublayer 3 – Link Management Entity (LME)13

6.4Network layer13

6.5Transport layer13

6.5.1Transmission packets13

6.5.2Retransmission of packets14

7Test conditions14

8Power supply, environmental and EMC test15

9Operational tests15

10Specific tests of link layer15

11Specific tests of network15

Annex A (normative) GMSK type VDSMS17

A.1Scope17

A.2References17

A.3Performance characteristics17

A.3.1Frequency and type of signal17

A.3.2Radiated power output17

A.3.3Type of emission17

A.3.4Radiated power output17

A.3.5Modulation Characteristics17

A.4Performance Tests17

A.4.1Transmitter17

A.4.2Receiver17

Annex B (normative) /4 DQPSK type VDSMS18

B.1Scope18

B.2References18

B.3Performance characteristics18

B.3.1Frequency and type of signal18

B.3.2Radiated power output18

B.3.3Type of emission18

B.3.4Radiated power output18

B.3.5Modulation Characteristics18

B.4Performance Tests18

B.4.1Transmitter18

B.4.2Receiver18

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RADIO TECHNICAL COMMISSION FOR MARITIME SERVICES

RTCM STANDARD 12301.0

for

VHF-FM Digital Small Message Services

1 Scope

This standard specifies the minimum functional and technical requirements for VHF-FM Digital Small Message Services (VDSMS).

The VHF-FM Digital Small Message Services are intended to provide short text messaging for ship to ship, shore to ship and ship to shore applications.

The VHF-FM Digital Small Message Services operates on frequencies in the International VHF Marine Band, unless otherwise restricted by regulation. VDSMS may share channels with voice services on a non-interference basis. The VHF Data Link access method for VDSMS will help to ensure that a voice call in progress is not disrupted.

VDSMS transmissions will have a limited duration and a limited duty cycle to ensure the availability of the channel for other users. The VDSMS transmitter emissions masking is designed to protect the users of the adjacent channels.

The body of this standard includes requirements for The VHF-FM Digital Small Message Services (Sections 1 through 8). Requirements for specific technologies are contained in the Annexes.

2 Normative references

The following referenced documents are indispensable for the application of this standard to the extent specified herein. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

IEC 61162-1

IEC 61993-2

IEC 62287-1

ITU-R M.1084-4

ITU-R M.1371-3

ITU-R M.1842

ITU Radio Regulations (RR) Appendix 18

ISO/IEC 3309:1993

3 Definitions and abbreviations3.1 Definitions

VHF-FM Digital Small Message Services (VDSMS)

A Marine Short Messaging Service that uses VHF channel white space to transmit and receive digital messages between ships and between ships and shore stations.

3.2 Abbreviations

TBD (For Reference- this is the list from Class B IEC document with a couple of additions)

AIS Automatic Identification System

BER Bit Error Rate

BT Bandwidth Time product

COG Course over ground

CPU Central Processing Unit

CRC Cyclic Redundancy Check

CS Carrier-Sense

CSTDMA Carrier-Sense Time Division Multiple Access

DGNSS Differential Global Navigation Satellite Service

DLS Data Link Service

DSC Digital Selective Calling

ECDIS Electronic Chart Display and Information System

EPFS Electronic Position Fixing System

ETA Estimated Time of Arrival

EUT Equipment Under Test

FCS Frame Check Sequence

FM Frequency Modulation

GMSK Gaussian Minimum Shift Keying

GNSS Global Navigation Satellite Service

HDG Heading

HDLC High level Data Link Control

HSC High Speed Craft

IEC International Electrotechnical Commisission

IMO International Maritime Organization

ITU International Telecommunication Union

LME Link Management Entity

LR Long Range

MAC Medium Access Control

MMSI Maritime Mobile Service Identity

NM Nautical Miles (refer to ISO 19018)

NRZI Non Return to Zero Inverted

NUC Not Under Command

OSI Open System Interconnection model

Pss Steady state RF output power

PER Packet Error Rate

PI Presentation Interface

PRS Pseudo Random Sequence

RAIM Receiver Autonomous Integrity Monitoring

Rx Receive

SINAD Signal Interference Noise and Distortion ratio

SOG Speed Over Ground

SOLAS International Convention for the Safety of Life at Sea

TBD To Be Determined

TBR To Be Reviewed

TDMA Time Division Multiple Access

Tx Transmit

UTC Universal Time Coordinated

VDL VHF Data Link

VDSMS VHF-FM Digital Small Message Service

VDM Serial output message containing VDL information (IEC 61162-1)

VHF Very High Frequency

VSWR Voltage Standing Wave Ratio

VTS Vessel Traffic Services

4 Requirements

4.1 4.2 Operating frequencies

VDSMS is intended to operate on frequencies in the VHF Marine Band.

VDSMS is intended to operate in ship-to-ship and ship-to-shore modes.

4.2.1 Operating channels

VDSMS may operate on both simplex and duplex 25-kHz channels as specified in recommendation ITU-R M.1084-4.

4.3

VDSMS may share a channel (e.g. with voice services).

4.3.1 Determining the availability of a channel

VDSMS shall use the carrier-sense method described in recommendation ITU-R M.1371-3 Annex 7 to determine the availability of a channel for transmission.

When VDSMS determines by carrier-sense that a channel is occupied, it shall delay its pending transmission attempt by a pseudo-random time of between 5 milliseconds and 100 milliseconds, in one millisecond intervals. Each transmission attempt shall be preceded by carrier-sense determination of availability of the channel.

VDSMS shall scan a channel for availability for at least four seconds.

In response to a message requesting acknowledgement of delivery, VDSMS shall immediately acknowledge receipt of a message, without delay (i.e. without carrier-sense or scan delay).

4.3.2 Limiting the use of a channel

VDSMS shall limit the duration of each transmission to a maximum of 150 milliseconds.

VDSMS shall wait at least one second between successive transmissions.

4.4 Transmitter emissions spectrum

VDSMS shall use the transmitter modulation emissions mask specified in IEC 61993-2 to protect adjacent channels.

VDSMS transmitter attack and decay times shall be as specified in IEC 62287-1.

VDSMS mobile equipment transmitter power shall be less than or equal to 25 watts PEP.

VDSMS base station equipment transmitter power, measured at the base of the antenna, shall be less than or equal to 50 watts PEP.

4.5 Transmitter modulation

VDSMS equipment transmitter modulation shall be as specified in recommendation ITU-R M.1371-3 or recommendation ITU-R M.1842 Annex 1.

4.6 Receiver performance

VDSMS equipment receiver performance shall be as specified in IEC 61993-2.

VDSMS minimum static receiver sensitivity for the transmitter modulation specified in recommendation ITU-R M.1842 Annex 1 shall be as specified that recommendation.

5 Performance requirements 5.1 General

5.2 Composition

The VDSMS transceiver shall be comprised of:

· a communication processor, capable of operating in a part of the VHF Maritime Mobile Service band, in support of short range (VHF) applications;

· at least one transmitter and one receiving processes

· processes shall work independently and simultaneously on AIS channel A and channel B4

· Others TBD?

TBR

5.3 Operating frequency channels

The VDSMS shall be designed for operation in the VHF maritime mobile band, on either 25 kHz or 12.5 kHz simplex or duplex channels in half-duplex mode, in accordance with Radio Regulations (RR) Appendix 18 and Recommendation ITU-R M.1084, Annex 4.

The VDSMS shall operate on the coast station frequencies assigned to channels 21, 22, 23, 80, 81, 82 , 83 as listed in Radio Regulations (RR) Appendix 18 and Recommendation ITU-R M.1084, Annex 4.

5.3.1 Primary and secondary channel users

VDSM Services shall be secondary users of these channels. The primary users of these channels shall be in accordance with Radio Regulations (RR) Appendix 18 and Recommendation ITU-R M.1084, Annex 4.

5.3.2 Carrier Sense Time Division Multiple Access (CSTDMA)

Access to the operating channels shall be via Carrier Sense Time Division Multiple Access described 7.2.1 in this document. This access method is designed use channel white space and to minimize interference with the primary users.

TBR

5.4 Identification

For the purpose of ship and message identification, the appropriate Maritime Mobile Service Identity (MMSI) number shall be used?

The unit shall only transmit if an MMSI has been programmed?

TBR

5.5 VDSMS Message Content

The VDSMS message shall contain plain text.

The VDSMS message shall contain the MMSI of the transmitting radio?

The VDSMS message shall contain the position of the VDSMS transceiver or base station?

A point to point VDSMS message shall contain the address (MMSI) of the intended ship or shore station?

A broadcast message shall contain a broadcast message identifier?

The VDSMS message shall contain a CRC.

TBR

5.6 VDSMS Message Types

There shall be three types of VDSMS messages. They are an addressed text message, a broadcast text message and an acknowledgement message.

TBR

5.7 Alarms and indications, fall-back arrangements

5.7.1 Integrity and protection

The VDSMS shall be equipped with built in integrity tests (BIIT). The BIIT shall run continuously or at appropriate intervals simultaneously with the standard functions of the equipment.

If any failure or malfunction is detected that will significantly reduce integrity or stop operation

of the VDSMS, a visual indication shall be given. This includes the detection of background noise above –77 dBm.

The VDSMS installation, when operating, shall not be damaged by the effects of open-circuited or

short-circuited antenna terminals.

TBR

5.7.2 Transmitter shutdown procedure

An automatic transmitter shutdown shall be provided in the case where a transmitter does not

discontinue its transmission within 1 s of the end of its nominal transmission. This procedure

shall be independent of the operating software.

TBR

5.8 6.7 User interface

5.8.1 Indicators and display

The VDSMS transceiver shall be provided with the following indicators:

Power: power on and fully operable (transmitting and receiving properly);

Receipt: of message: successful or unsuccessful

TBR

5.8.2 MMSI input

It shall not be possible for the user to alter the MMSI once programmed (if MMSI used)

TBR

5.8.3 External interfaces

TBD

6 Technical requirements 6.1 General

This clause covers layers 1 to 4 (Physical Layer, Link Layer, Network Layer, Transport Layer) of the Open System Interconnection (OSI) model.

Figure 1 illustrates the layer model of an VDSMS transceiver (Physical Layer to Transport Layer) and the layers of the applications (Session Layer to Application Layer):

Figure 1 – OSI layer model

TBR

6.2 Physical layer

The Physical Layer is responsible for the transfer of a bit-stream from an originator to the data link.

TBR

6.2.1 Transceiver characteristics

General transceiver characteristics shall be as follows:

· Frequency Channels as specified in 6.2

· Channel spacing – 25 kHz (encoded according to RR Appendix 18 with footnotes)

· Channel bandwidth - 25 kHz

· Training sequence 24 bits

· Modulation in accordance with Annexes in this document

TBR

6.2.1.1 Single channel operation

The VDSMS transceiver shall operate on one channel at a time with no channel hopping. The operator shall manually select the operating channel.

TBR

6.2.1.2 Bandwidth

The VDSMS transceiver shall operate on 25 kHz channels according to ITU-R Recommendation

M.1084-4 and Appendix 18 of the Radio Regulations.

TBR

6.2.1.3 Modulation scheme

The modulation scheme shall be in accordance with one of the modulation schemes in the annex of this document.

TBR

6.2.1.4 Training sequence

Data transmission shall begin with a 24-bit demodulator training sequence (preamble) consisting of one segment synchronisation. This segment shall consist of alternating zeros and ones (0101....). This sequence shall always starts with a 0.

TBR

6.2.1.5 Data encoding

The NRZI waveform is used for data encoding. The waveform is specified as giving a change in the level when a zero (0) is encountered in the bit stream.

Forward error correction, interleaving or bit scrambling is not used.

TBR

6.2.2 Transmitter requirements

6.2.2.1 Transmitter parameters

Technical requirements for transmitters shall be in accordance with the requirements for the individual technologies as described in the Annex of this document.

TBR

6.2.3 Receiver requirements

Technical requirements for receivers shall be in accordance with the requirements for the individual technologies as described in the Annex of this document.

TBR

6.3 Link layer

The Link layer specifies how data shall be packaged in order to apply error detection to the

data transfer. The Link layer is divided into three sublayers.

TBR

6.3.1 Link sublayer 1: Medium Access Control (MAC)

The MAC sublayer provides a method for granting access to the data transfer medium, i.e. the

VHF data link. The method used shall be Carrier Sense Time Division Multiple Access (CSTDMA).

TBR

6.3.1.1 Carrier-sense (CS) detection method

The CSTDMA shall detect “dead air” on the selected VDSMS channel based on the CS detection threshold. When the CS detection threshold is met, a “transmission allowed window” of TBD seconds duration will begin provide the time from the last message transmission is at least TBD seconds. Access to the VDL shall be accomplished within this window of time. This transmission allowed window shall consist of TBD time slots.

TBR

6.3.1.2 CS detection threshold

TBD

6.3.1.3 VDL access

The VDSMS message shall be transmitted in one of the time slots in the transmission allowed window. The time slot shall be randomly selected to reduce interference with other VDSMS transmitters. Access to the VDL shall be limited one time slot within the transmission allowed window.

TBR

6.3.2 Link sublayer 2: Data Link Service (DLS)

The DLS sublayer provides methods for

· data link activation and release;

· data transfer; or

· error detection and control.

TBR

6.3.2.1 Data link activation and release

Based on the MAC sublayer the DLS will listen, activate or release the data link.

TBR

6.3.2.2 7.3.2.2 Data transfer

Data transfer shall use a bit-oriented protocol which is based on the High-Level Data Link

Control (HDLC) as specified by ISO/IEC 3309:1993. Information packets (I-Packets) shall be

used with the exception that the control field is omitted.

TBR

6.3.2.2.1 Bit stuffing

The bit stream shall be subject to bit stuffing. This means that if five consecutive ones (1’s)

are found in the output bit stream, a zero shall be inserted. This applies to all bits except the

data bits of HDLC flags.

TBR

6.3.2.2.2 Packet format

The packet shall be sent from left to right. This structure is identical to the general HDLC

structure, except for the training sequence. The training sequence shall be used in order to

synchronise the VHF receiver. The total length of the default packet is

256 bits. This is equivalent to 26.7 ms.

Start-Buffer

Training sequence

Start flag

Data

FCS

End flag

End-Buffer

TBR

6.3.2.2.3 Start-Buffer

TBD

6.3.2.2.4 Training sequence

TBD

6.3.2.2.5 Start flag

The start flag shall be 8 bits long and consists of a standard HDLC flag. It is used to detect the start of a transmission packet. The Start flag consists of a bit pattern, 8 bits long: 01111110 (7Eh). The flag shall not be subject to bit stuffing, although it consists of 6 bits ofconsecutive ones (1's).

TBR

6.3.2.2.6 Data

The data portion in the default transmission packet transmitted in 1 time period is a maximum of 168 bits.

TBR

6.3.2.2.7 Frame Check Sequence (FCS)

The FCS uses the Cyclic Redundancy Check (CRC) 16-bit polynomial to calculate the checksum as defined in ISO/IEC 3309:1993. All the CRC bits shall be pre-set to one (1) at the beginning of a CRC calculation. Only the data portion shall be included in the CRC calculation.

6.3.2.2.8 End flag

The End flag is identical to the Start flag as described in 7.3.2.2.5.

TBR

6.3.2.2.9 End-buffer

· bit stuffing 4 bits

NOTE The probability of 4 bits of bit stuffing is only 5 % greater than that of 3 bit; refer to ITU-R M.1371-1 A2 3.2.2.8.1.

· ramp down 3 bits

· distance delay 2 bits

NOTE A buffer value of 2 bits is reserved for a distance delay equivalent to 30 NM for own transmission.

A repeater delay is not applicable (Duplex Repeater Environment is not supported).

TBR

6.3.2.3 Summary of the transmission packet

TBD

6.3.2.4 Transmission timing

TBD

6.3.2.5 Long transmission packets

TBD

6.3.2.6 Error detection and control

Error detection and control shall be handled using the CRC polynomial as described in 7.3.2.2.7. CRC errors shall result in no further action by the VDSMS“.

TBR

6.3.3 Link sublayer 3 – Link Management Entity (LME)

The LME controls the operation of the DLS, MAC and the physical layer.

TBR

6.3.3.1 Access algorithm for transmissions

TBD

6.3.3.2 Modes of operation

TBD

6.3.3.3 Initialization

TBD

6.4 Network layer

The network layer shall be used for

· establishing and maintaining channel connections;

· management of priority assignments of messages;

· distribution of transmission packets between channels;

· data link congestion resolution.

TBR

6.5 Transport layer

TBD

6.5.1 Transmission packets

A transmission packet is an internal representation of some information, which can ultimately be communicated to external systems. The transmission packet is dimensioned so that it conforms to the rules of data transfer. The transport layer shall convert data intended for transmission, into transmission packets.

The transport layer keeps track of the packet delivery and the packets that must be resent.

TBR

6.5.2 Retransmission of packets

An acknowledgement message shall be transmitted by the receiving radio upon successful receipt of the message. If the acknowledgement is not received within TBD seconds, the message shall be retransmitted. Retransmission shall be limited to TBD retries. The retries shall follow the same link access rules as the original transmission. The VDSMS transceiver that originated the message shall provide an positive indicator to show successful or unsuccessful transmission of the addressed message.

7 Test conditions

8.1 General

The test condition requirements in section 8 are applicable to all technologies described in the Annex of this document.

TBR

8.2 Normal and extreme test conditions

8.2.1 Normal test conditions

8.2.1.1 Temperature and humidity

Temperature and humidity shall be within following range:

Temperature +15 °C to +35 °C

Humidity 20 % to 75 %

TBR

8.2.1.2 Power supply

The normal power supply for the tests shall be the nominal voltage as defined by the

manufacturer ±3 %.

TBR

8.2.2 Extreme test conditions

Test under extreme test conditions shall be a combination of high temperature (dry heat) and

upper limit of supply voltage applied simultaneously and low temperature and lower limit of

supply voltage applied simultaneously (see Clause 9).

During type-testing of battery operated equipment the power source to the equipment may be

replaced by a test power source, capable of producing normal and extreme test voltages.

TBR

8.3 Test signals

The test signals are described in the Annex of this document each of the included technologies.

TBR

8.4 Test arrangements

8.4.1 Standard test environment

TBD

8.4.2 Modes of operation of the transmitter

For the purpose of the measurements according to this standard, there shall be a means to

operate the transmitter unmodulated or, alternatively, the method of obtaining an

unmodulated carrier or special types of modulation patterns may be decided by agreement

between the manufacturer and the test laboratory. It shall be described in the test report. It

may involve suitable temporary internal modifications of the equipment under test.

TBR

8.4.3 Measurement uncertainties

Maximum values of absolute measurement uncertainties shall be as follows:

RF frequency .........................................................................±1 10–7

RF power .............................................................................. ±0,75 dB

Adjacent channel power ............................................................. ±5 dB

Conducted spurious emission of transmitter ............................... ±4 dB

Conducted spurious emission of receiver .................................. ±3 dB

Two-signal measurement ........................................................... ±4 dB

Three-signal measurement ........................................................ ±3 dB

Radiated emission of transmitter ................................................ ±6 dB

Radiated emission of receiver ................................................... ±6 dB

Transmitter timing characteristics ..................................±1 bit (104 μs)

Transmitter transient frequency (frequency difference) ...........±250 Hz

For the test methods according to this standard, these uncertainty figures are valid to a

confidence level of 95 %.

The interpretation of the results recorded in a test report for the measurements described in

this standard shall be as follows:

a) the measured value related to the corresponding limit shall be used to decide whether

equipment meets the requirements of this standard;

b) the actual measurement uncertainty of the test laboratory carrying out the measurements,

for each particular measurement, shall be included in the test report;

c) the values of the actual measurement uncertainty shall be, for each measurement, equal to or lower than the figures given in this subclause (absolute measurement uncertainties).

TBR

8 Power supply, environmental and EMC test

TBD

9 Operational tests

TBD

10 Specific tests of link layer

TBD

11 Specific tests of network

TBD

Annex A (normative)

GMSK type VDSMS

A.1 Scope

TBD

A.2 References

TBD

A.3 Performance characteristics

TBD

A.3.1 Frequency and type of signal

A.3.2 Radiated power output

A.3.3 Type of emission

A.3.4 Radiated power output

A.3.5 Modulation Characteristics

A.4 Performance Tests

TBD

A.4.1 Transmitter

A.4.2 Receiver

Annex B (normative)

/4 DQPSK type VDSMS

B.1 Scope

TBD

B.2 References

TBD

B.3 Performance characteristics

TBD

B.3.1 Frequency and type of signal

B.3.2 Radiated power output

B.3.3 Type of emission

B.3.4 Radiated power output

B.3.5 Modulation Characteristics

B.4 Performance Tests

TBD

B.4.1 Transmitter

B.4.2 Receiver

� Appendix 18 of the International Radio Regulations (RR Ap 18)Reference Part 80

� Reference Part 80?

�Take language from AIS...

�IEC 60945?