How It Works
The elements of the Iridium end-to-end SBD architecture are the Field Application (FA), the Iridium Subscriber Unit (ISU), the Iridium satellite constellation, the Gateway SBD Subsystem (GSS) located at the Iridium gateway, the Internet, and the Vendor Application (VA.) The interface between the FA and the ISU is a serial connection with extended proprietary AT commands. The interface is used to load and retrieve messages between the ISU and the Field Application.
Remote Applications send Mobile Originated SBD (MO-SBD) messages from an Iridium 9522 L-Band Transceiver (LBT). The application microcontroller or microprocessor communicates with the LBT via AT commands over an RS232 connection. The application loads the message into the LBT and instructs it to send the message, which traverses the Iridium satellite network via inter-satellite links to reach the Iridium Gateway. From there, the message is transferred to the Internet and onto a Value Added Resellerís host computer system where it is stored in a database for further data processing.
Mobile Terminated SBD (MT-SBD) messages are sent to the Iridium Gateway via the Internet from the Value Added Resellerís host computer system.
The maximum length of a MO-SBD message is 1960 bytes. The maximum length of a MT-SBD message is 1890 bytes. Global network transmit latency for message delivery ranges from 5 seconds for messages of 70 bytes to approximately 20 seconds for maximum length messages. (Additional latency may occur across the Internet.)