Iridium Network

There's no need to show a coverage map picture because Iridium is the world's only truly global mobile communications company, with coverage of the entire Earth, including oceans, airways and Polar Regions.

Iridium voice and data products provide communications solutions that allow global companies, government agencies and individuals to stay connected, everywhere. The unique Iridium constellation of 66 Low Earth Orbiting (LEO) cross-linked satellites routes communications traffic through space and around the world, creating highly efficient and reliable connections.

The network is considered a meshed constellation of interconnected, cross-linked satellites so that each satellite “talks” with the other nearby satellites in adjacent orbits. Unique to Iridium, this architecture provides inherent advantages in performance and reliability over other mobile satellite services providers.

Iridium Low-Earth-Orbiting satellites (LEO for short) are approximately 485 miles (781 km) above the Earth's surface and travel in a polar orbit, meaning they move around the Earth from one pole to the other pole. These 66 satellites make up 6 rings of 11 satellites each and travel at a speed of 17,000 mph (27,000 km) making a complete orbit around the Earth every 100 minutes. The 6 polar orbiting rings around the planet also slowly change their longitude in a westerly direction from the equator so they never rise in the same location each orbit… This means Iridium satellites will both rise from the north or rise from the south on different days…

Standing on the ground, an Iridium satellite will rise from the horizon and stay within line-of-sight view for about 7 minutes. To maintain constant connectivity with the Iridium network, a data handoff is made when one satellite is setting and another is rising from the horizon… this allows for Iridium's 100% seamless coverage which goes completely unnoticed to the end-user.

Short Burst Data or SBD is a simple and efficient bi-directional transport capability used to transfer messages with sizes ranging from zero (a mailbox check) to 1960 bytes for Mobile Originated (MO-SBD) and zero to 1890 bytes for Mobile Terminated (MT-SBD). SBD takes advantage of signals within the existing air interface, without using the dedicated traffic channels. As a result, small amounts of data can be transferred more efficiently than those associated with circuit-switched data calls.

For MO-SBD, messages are transmitted across the Iridium satellite network utilizing inter-satellite links to reach the gateway. From there messages are disseminated to end-users via direct IP link. For MT-SBD, messages are sent to the Iridium gateway via IP from an end-user host computer. From there messages are delivered to an ISU immediately following a MO-SBD or “mailbox check” by an ISU. Global network transmit latency for delivery of messages ranges from ~5 seconds for short messages to ~20 seconds for maximum length messages. This latency is the elapsed time before the Iridium SBD system sends the SBD message to its destination. Additional latency introduced by the Internet/NIPRNet or the customer's host system is not in Iridium's control.