User Manual Part 7

User Guide to Q4000/QPRO
Document Number 1135-4713 Rev G
THIS DOCUMENT CONTAINS CONFIDENTIAL AND PROPRIETARY INFORMATION OF QUAKE GLOBAL CORPORATION. IT MAY BE USED BY
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13 Satellite networks
13.1 ORBCOMM network
The ORBCOMM System is a wide area, packet-switched, two-way data communication system.
Communications between modems and ORBCOMM Gateways are accomplished via a
constellation of Low-Earth Orbit (LEO) satellites.
The ORBCOMM System consists of ground infrastructure, a space segment, and a subscriber
segment. A Network Control Center (NCC) manages the overall system worldwide.
• The ground infrastructure contains the ORBCOMM Gateway, which provides message
processing and subscriber management.
• The space segment currently consists of 29 LEO satellites and one Satellite Control
Center (SCC).
• The subscriber segment consists of the modems used by ORBCOMM System
subscribers to transmit information to, and receive information from the LEO satellites.
RF communication within the ORBCOMM System operates in the Very High Frequency (VHF)
portion of the frequency spectrum, between 137 and 150 Megahertz (MHz).
Figure 13-1: ORBCOMM satellite network diagram
There are four basic service elements provided by the ORBCOMM System: Data Reports,
Messages, Globalgrams, and Commands.
• Data Reports – the modem uses a data report to transmit or receive a single packet
containing 6 bytes or less of user-defined data.