Broadcast AIS ASM Message

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Extended description: 
Encapsulated AIS ASM messages
not applicable
Access scheme: 
Communication state: 
Transmitted by: 
Base station
  • ASM Message 0 may contain encapsulated AIS Messages 6, 8, 12, 14, 21, 25 or 26. Acknowledgement is not supported for addressed messages. This message type is for terrestrial use only. (notice from website master: msg 6 and 12 are addressed messages)
  • The encapsulated message may or may not be transmitted on AIS1 or AIS2 channels.
  • If the encapsulation repeats a Message that was transmitted on AIS1 or AIS2 channel, the encapsulation and transmission of messages shall be performed as soon as possible, according to configuration, after receiving the relevant messages which are required to be retransmitted.
  • The communication state of the encapsulated message shall always be set to zero at encapsulation.
  • The receiving station shall output all received encapsulated AIS Messages at the PI immediately after reception. Scheduled broadcast message is defined in Table 25 (below).

Table 25

Broadcast AIS ASM Message


Number of bits


Message ID


0 - Selected AIS messages that are output at receiving mobile station PI by using VDM sentence with no communication state

Retransmit flag


0 (reserved for future use)

Repeat Indicator


If the encapsulation repeats a Message that was transmitted on AIS1 or AIS2 channel, this is used to indicate how many times a message has been repeated. Encapsulation represents one repeat.

Possible values: 0 – 3:

0 = default, shall be used in case where the message is sent only on ASM channel(s);

1: also transmitted on AIS channel(s);

2, 3 = also transmitted on AIS channel(s) and repeated as counted by the repeat indicator on ASM channel.

Session ID


The Session ID associates the VDL transmission with a specific PI transaction

Source ID


The Unique Identifier of the transmitting station as described in  § 2.4, Annex 1. (see text below table)

Data Count


Size of actual data in Binary Data and ASM Identifier field in bits, excluding padding bits range: from 1 to maximum data count

Binary Data

(no FEC / FEC)

1 slot: 296 / 200
2 slot: 808 / 584
3 slot: 1320 / 968

Content is encapsulated AIS Messages that are channelled through ASM Channels. The Message 0 is transmitted only by Base Stations. Receiver is expected to be ASM-capable mobile station where the ASM-box would relay the encapsulated AIS messages to local presentation interface. The encapsulated AIS Messages would then be output at the PI using VDM sentence. The arrangement would thus be compliant with existing nav presentations.

Application data as specified by the ASM Identifier. 

The available length of the binary data is specified by the Link Id.


Annex 1  2.4 Station identification

Identification and location of all active maritime stations is provided automatically by means of the AIS. All VDES stations should be uniquely identified. For the purpose of identification, a unique numerical identifier is used as defined by the following:

If the unique identifier has a range which is less than or equal to 999999999, then this number is defined by the most recent version of Recommendation ITU-R M.585.

If the unique identifier has a range which is greater than 999999999, then this number is free form.