日本財団図書館（電子図書館）　Ninth International Conference on Maritime Education and Training Proceedings

　

Table 3 : Comparison of Transponder Systems - Operational Aspects

Characteristics	DSC ("2S?")	STDMA ("4S")	Mobile (LOPOS)
Timing of Message Collision Rate Data Overhead	Non-coordinated High High	Self-synchronized Very small Low	-
Telegramme	128 Byte	256 Byte	256 Byte
Transmission Rate	1996:1200 bit/s later : 9600	9600 bit/s	128 KBaud
System Capacity (Ships*Update Rate)	max 160/mm (9600 bit/s)	2000/min	-
Frequencies	Channel 70	136-174MHz	2.4GHz
Required Radio Channels Usage of Channel	VHF Channel 70 + at least 1 working Channel <30%	1 ww VHF Channel (+1 reserve Chan. where required) >90%	80 Channels Frequency Hopping
Transmiss. Reliabiliy	High	High	-
International Standards	CCIR/IALA GMDSS	Aviation (IALA)	-

　

6. IMO Activities

　

The revision of SOLAS Chapter V including the review of ship's safety standards takes account of the safety potential of "Transponders" (AIS) and of the present controversy between DSC and STDMA "Transponder" systems. The Sub-Committee on "Safety of Navigation" on its sessions NAV 41(1995) and NAV 42 (1996) has prepared

- a "Draft Revision of SOLAS Chapter V" containing the carriage requirements (1);

- draft performance standards for a shipborne AIS using broadcast techniques (2);

- draft performance standards for a shipborne AIS using VHF DSC techniques (3).

　

After controversial discussion, the functional superiority of the AIS using broadcast techniques and STDMA has been recognized and the carriage requirement will be approved. In the revised draft SOLAS text (Regulation 1), this reads as follows:

　

　

　

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