Nera Inmarsat-c, Service Manual

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AP1.1 System Overview
AP1-3
AP1.1.2 Inmarsat C Services
The Inmarsat C system provides the following communication services.
(1) Store-and-forward Telex message service
(2) EGC (Enhanced Group Call) broadcasting: Safety Net and Fleet Net
(3) Distress alerting and safety service
The following services are also available.
- Polling: The facility whereby an operational center sends a instruction to selected
MES, to perform a defined task, such as return a pre-assigned data report.
- Data reporting: Data report, such as ship’s position is sent regularly to a terrestrial
subscriber.
- E-mail
Table AP1.1.3 lists each service of the Inmarsat system.
Table AP1.1.3 Comparison of each Inmarsat sytem service
Inmarsat system
Service
A B C M Mini M
Voice Available Available Not available Available Available
FAX Available Available
Only sends
TEXT to PSTN
for Ship to Shore
direction.
Available Available
Telex Available Available Available Not available Not available
Data
communication
Available Available Available (DNID) Available Available
HSD
Communication
Available Available Not available Not available Not available
Store-and-forward Telex service
The following briefly describes how a MES sends a ship-to-shore message.
1) When the MES sends a message, it transmits a channel assignment request to the
LES. Then, the LES assigns the channel to the MES. After receiving a channel
assignment, the MES starts transmitting the message in packets.
2) The LES stores the received message and reconfigured the message. The LES
checks the received packets for errors, and if it finds any, returns acknowledgement
packets identifying the packets in error to ask to send the message again. The
reconfigured message is send to the intended destination via public network.
3) When the land subscriber sends the message, LES sends the message in packets to
MES. The MES checks the received packets for errors, and if it finds any, returns
acknowledgement packets identifying the packets in error to ask to send the
message again. The MES stores the received message and reconfigured the
message to output.