This ASM message is used to broadcast data to all targets and does not contain a communication state. These broadcast messages are used for non-periodic transmission of data, and access the link using RATDMA. Broadcast message is defined in Table 27.
Table 27
Broadcast Message
|
Parameter |
Number of bits |
Description |
|---|---|---|
|
Message ID |
4 |
2 - Broadcast message with no communication state |
|
Retransmit flag |
1 |
0 (reserved for future use) |
|
Repeat Indicator |
2 |
Used by the repeater to indicate how many times a message has been repeated. 0 - 3; 0 = default; 3 = do not repeat any more |
|
Session ID |
6 |
The Session ID associates the VDL transmission with a specific PI transaction |
|
Source ID |
32 |
The Unique Identifier of the transmitting station as described in § 2.4, Annex 1. |
|
Data Count |
11 |
1 - Max data count |
|
ASM identifier |
16 |
Application identifier and described in § 6.2 |
|
Binary Data (no FEC / FEC) |
1 slot: 280 / 184 2 slot: 792 / 568 3 slot: 1304 / 952 SAT: N/A / 848 |
Application data as specified by the ASM Identifier. The available length of the binary data is specified by the Link Id. |
Table 22
ASM identifier parameters
|
Bit |
Description |
|---|---|
|
15-6 |
Designated area code (DAC). This code is based on the maritime identification digits (MID). Exceptions are 0 (test) and 1 (international). Although the length is 10 bits, the DAC codes equal to or above 1 000 are reserved for future use |
|
5-0 |
Function identifier. The meaning should be determined by the authority which is responsible for the area given in the designated area code |
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.