The logical channels are described in the table below.
|
Name |
Type |
Function |
Direction |
|
NCS Common |
Control |
Network Bulletin Board status information |
Forward (to MES) |
|
NCS Assignment |
Control |
Channel assignment |
Forward (to MES) |
|
NCS Spot-beam Identification |
Control |
Spot beam identification for MES |
Forward (to MES) |
|
NCS Inter-station |
Control |
NCS-LES signaling and assignment |
Forward (to LES) |
|
NCS Registration Acknowledgement |
Control |
Registration acknowledgement |
Forward (to MES |
|
LES Assignment |
Control |
Stand-alone or NCS backup assignment |
Forward (to MES) |
|
LES Inter-station |
Control |
LES-NCS signaling |
Return (to NCS) |
|
MES Request |
Control |
Access request channel |
Return (to LES, NCS) |
|
MES Response |
Control |
Signaling response channel |
Return (to NCS) |
|
MES Registration |
Control |
Initial registration |
Return (to LES, NCS) |
|
MES Call Acknowledgement |
Control |
Call acknowledgement |
Return (to LES) |
|
SCPC channel |
User traffic |
Circuit switched |
Forward and return |
|
Shared channels |
User traffic |
Packet switched |
Return |
The only frequencies the MES initially knows are the frequencies of the NCSC in all regions - all other frequency information is dynamically extracted from the NCS Bulletin Board or in session oriented signaling messages. After being switched on, the MES must be told (or remembers) in which region it is currently located, and will automatically tune to the corresponding frequency of the NCS. The terminal will then search through the NCSS spot beam ID frequencies to identify the best spot beam.