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27
Sep
Satellite communications is not just for humans. In recent years Iridium satellite communications in particular has become a common choice for machine-to-machine (M2M) communications. Conventional terrestrial cellular networks can fail due to weather, earthquake or other regional emergencies. M2M applications need to be highly reliable, so M2M satellite communication equipment is increasingly being selected. In some cases, there also is a need for broader ranging coverage than is available from terrestrial cellular networks. For this reason, M2M satellite communication applications now include global monitoring of vehicle and cargo container fleets, monitoring of oil pipelines, and even aerial drones.
Rise of the "Talking" Machines
Unsurprisingly, smart devices that must perform actions automatically without human interaction are beginning to consume more and more data. In 2014 there were 5 billion such mobile smart devices. By 2020 it has been suggested that 11 billion smart devices may exist.M2M smart devices do not use data in the same way humans do. Most M2M satellite communications rely on short message service (SMS). The SMS messages have fixed-formats and typically follow strict calendar schedules. This means that M2M communication expenses tend to stay on budget -- another difference between M2M and human calling patterns.Hardware options for M2M over satellite:
The Iridium 9603 transceiver is one of the smallest short burst data (SBD) devices available. At about 31.5 mm long x 29.6 mm wide, it is similar is size to a postage stamp. It is 8.1 mm thick and weighs only 11.4 grams. A low-profile patch antenna suitable for mobile applications is available for use with the Iridium 9603. Costs currently range from a few hundred dollars to about $400 depending on how many you purchase.If you need faster data speeds, Inmarsat BGAN M2M products like the Hughes 9502 are available. The Hughes 9502 must be setup at a fixed-site but it can be managed from a remote terminal software and can recover from power failures without human intervention. Equipment costs currently are typically under $1500.Latency:
More most M2M applications the short amount of time a data packet takes to travel from the smart device to the destination server is not extremely important. However, in some applications data packet latency is a critical issue. For example, if you are controlling an aero drone, the amount of time it takes to send a command to steer the drone could be critical.Iridium has 66 active satellites in low earth orbit at a height of approximately 781 km. Voice latency has been estimated to be 0.27 to 0.39 seconds.* A 1024 bit data packet sent over the Iridium network can take from 0.43 to 1.7 seconds.*
Inmarsat uses geostationary satellites that are 36,000 km above the earth. The 72,000,000 meter round trip space leg path causes a 0.240 seconds of latency, and buffering and internet travel time further increase the latency. Measurements suggest that Inmarsat BGAN Streaming IP data packet latency ranges from 0.8 to 0.9 seconds if the internet is not congested but can reach 2.0 seconds if there is congestion. BGAN Standard IP data packets latency is 1.1 seconds if there is no internet congestion. The effect of internet congestion can be combatted using a dedicated line from the Inmarsat PoP to the destination device, but that is expensive.
* Lemme, P.W., Glenister, S.M., and Miller, A.W., "Iridium(R) Aeronautical Satellite Communications" , Aerospace and Electronic Systems Magazine, IEEE , vol. 14 no. 11, 1999, pp 11 –16
** All prices, terms, conditions, and equipment specifications in this article are subject to change without notice.
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Guy Arnold
