Sat system, Overview – Wavecom W61PC V7.5.0 User Manual
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WAVECOM Decoder W61PC/LAN Manual V7.5
SAT System
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SAT System
Overview
INMARSAT Ltd. is a private satellite provider based in London, UK
It evolved
from an inter-governmental organization to its current private status in the late 1990s. It operates a num-
ber of geostationary satellites covering the entire surface of the earth (except the polar regions) using
global beams, and spot beams for the more traffic intensive regions.
The positions (orbital slots) of the two latest generations of INMARSAT satellites are listed in the table be-
low.
Coverage Area
Satellite
Designation
Orbital
Position
Former Country
Code
Atlantic Ocean Region West (AOR-W)
3F4
54° W
+874
Atlantic Ocean Region East (AOR-E)
3F2
15° W
+871
Indian Ocean Region (IOR)
3F1
64° E
+873
Pacific Ocean Region (POR)
3F3
178° E
+872
Asia, Pacific
I-4 Asia-Pacific (4F1)
143° E
Europe, Middle East, Africa
I-4 EMEA (4F2)
25° E
Americas
I-4 Americas (4F3)
98° W
INMARSAT now uses +870 as a single country code for all regions (SNAC)
Each region has a system architecture as depicted below
A region is controlled by a Network Control Station, NCS. Its functions are operation of the control chan-
nels and allocation of traffic channels and channel resources. Each region may encompass a number of
Land Earth Stations, LES. Their functions are interfacing to terrestrial networks (PSTN, data networks, In-
ternet), session control. The user terminals called a Mobile Earth Stations, MES, communicate with the
NCS and LES. The NCS communicate with all LES within its control area. The LES and NCS continuously
broadcast system information.