Nera Inmarsat-c, Service Manual, Page: 129 / 228

AP1.1 System Overview
AP1-8
NCS/LES Signaling Channel
All LES is linked to NCS and this channel.
a. contacting to NCS and then confirming whether the MES is login or not, when the
shore sends the message to MES.
b. forwarding EGC message to NCS.
c. forwarding NCS received distress alerts to LES.
MES Message Channel
This channel is used when the message is sent to LES from MES. Each LES has a
number of MES message channels assigned to it by the NCS. Allocation of MES
message channels to MESs is done by the LES via LES TDM channel (the assignment
packet).
MES Signaling Channel
This channel is used when MES sends the line controlling packets (channel assignment
request, distress call, data reporting, etc.) to LES or NCS. This channel is worked by the
combination of the slot aloha and the reserve access mode. The channel to be used and
the slot information is transmitted by the NCS common channel and the LES TDM
channel.
NCS/NCS Signaling Link
This is a data link between NCS. It is used when the information about MES in its
coverage area is exchanged.