How Iridium SBD Works

Iridium Short Burst Data (SBD) Delivers Cost-Effective One-to-Many M2M

Iridium SBD is the world’s first one-to-many global data broadcast service.

Available as an on-demand or dedicated service, Iridium Burst offers secure, simple, cost-effective and low latency one-to-many transmission of data to an unlimited number of
enabled devices within a targeted geographic region – at a fraction of the cost of comparable services.

From command and control of troops and deployed assets to software, firmware and electronic billboard updates, to warnings about tsunamis, fires, earthquakes, tornados and
hurricanes, Iridium Burst transmits highly actionable, customer-specific critical information anywhere on the planet.

Iridium’s SBD uses small portable satellite modems to relay vital information back to where needed.

Iridium delivers the information client needs for monitoring – anywhere on the planet.

How Iridium SBD Works

Iridium’s SBD is a simple and efficient satellite network service for transmitting short data messages between field equipment and a centralized host computing system. It is integrated in our case by us, for running specific maritime applications.

The primary elements of an end-to-end SBD architecture consist of:

  • client’s field application,
  • the Iridium satellite transceiver/modem,
  • the Iridium satellite constellation,
  • the Gateway SBD Subsystem (located at the Iridium gateway),
  • the Internet,
  • and client’s host Application (such as a tracking, SCADA host application, etc.).

The field application represents the hardware and software that is configured for specific applications, such as collecting and transmitting equipment health parameters or GPS location information.
The satellite transceiver/modem is an Iridium L-Band Transceiver with the SBD feature available in firmware and the service activated on the Iridium network.
The Gateway SBD Subsystem is responsible for storing and forwarding messages from the satellite transceiver/modem to the Host VA Application and storing messages from the VA Application to forward to the satellite transceiver/modem.
The satellite transceiver/modem communicates with the Gateway SBD Subsystem via the Iridium satellite constellation.

The interface between the Host Application and the Gateway SBD Subsystem uses either standard Internet mail protocols or an IP Socket type interface to send and receive messages. Mobile terminated messages are sent to the Gateway SBD Subsystem using a common email or IP address, identifying the specific satellite transceiver/modem by encoding the unique satellite transceiver/modem’ IMEI in the subject line of the email or as part of the IP Socket payload. For email, the data message itself is transported as a binary attachment to the email. For IP Socket, the data message is part of the payload. Messages sent to the Host Application are delivered to a specific email or IP address that is configured when the IMEI is provisioned.

It is also possible for one satellite transceiver/modem to send a message direct to another satellite transceiver(s)/modem(s) without the message passing to the Host Application. The second satellite transceiver/modem destination IMEI must be programmed on-line by us. However, only one delivery type (email or satellite transceiver/modem to satellite transceiver/modem) is permitted. Up to five email addresses or five satellite transceiver/modem IMEIs or one IP Socket address can be provisioned as destinations for Mobile Originated SBD Messages.

For a Mobile Originated SBD Message (MO-SBD) the message is loaded into the MO buffer in the satellite transceiver/modem, then a message transfer session between the satellite transceiver/modem and the Gateway SBD Subsystem is initiated. For a Mobile Terminated SBD Message (MT-SBD) the satellite transceiver/modem can either initiate a Mailbox Check to see whether a MT message is queued at the Gateway SBD Subsystem; or the satellite transceiver/modem can use the “SBD Ring-Alert” capability to be told when a MT message is queued at the Gateway SBD Subsystem. The satellite transceiver/modem must then retrieve the MT-SBD message from the Gateway SBD Subsystem. When the message is received from the Gateway SBD Subsystem it can be retrieved from the MT buffer in the satellite transceiver/modem by the field application. Additionally an MT-SBD message can also be retrieved in the same network transaction by the satellite transceiver/modem when a MO-SBD message is sent from the satellite transceiver/modem.

Messages are transferred between the satellite transceiver/modem and the Gateway SBD Subsystem using a reliable transport mechanism that ensures the message is delivered error free. If the satellite transceiver/modem was not able to send or receive messages, an indication is passed to the field application via the serial interface.

The MO and MT message buffers in the satellite transceiver/modem will maintain messages as long as the satellite transceiver/modem is powered on. Once a message is transferred from the field application to the MO buffer in the satellite transceiver/modem, it will remain there even after it is successfully sent to the Gateway SBD Subsystem. If a MT message is received at the satellite transceiver/modem from the Gateway SBD Subsystem, it will remain in the MT buffer even after the field application reads it. The buffers in the satellite transceiver/modem will be cleared only when either given an explicit command or when the satellite transceiver/modem is power cycled, or is overwritten with new data.

All MO and MT messages between the host application and the Gateway SBD Subsystem are routed to the Internet by default. Iridium offers additional options for Virtual Private Network (VPN) and leased line routing of email or IP Socket messages to provide additional security, capacity and/or redundancy if required for the application. satellite transceiver/modem to satellite transceiver/modem SBD messages remain entirely within the Iridium network infrastructure.

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.