OTAcast provides efficient firmware upgrading of ground devices

OTAcast, developed by Steinwurf, is the most effective coding algorithm for broadcasting information (e.g. firmware updates) to a big population of devices over the satellite link, and makes it possible for operators to quickly patch security holes and offer new services protecting their investment in ground devices.

In modern satellite IoT networks the following scenario applies:

+ A constellation of low-earth-orbit satellites each orbiting the earth in approximately 1 0.5 hours and thereby only able to connect to a ground device approximately 30 minutes a day split over 2 maybe 3 orbits.

+ Thousands of ground devices installed all over the world, where each ground device often will be mobile and thereby have varying stability of its link to a passing satellite.

+ It has to be assumed some data packets will be lost on their way from the satellite to the ground device due to a temporarily degraded satellite link (e.g. from bad weather or temporarily no line of sight from ground device to the satellite).

+ Unnecessary transmissions between ground devices and the satellite should by all means be avoided to save battery power.

+ Transmissions from the ground devices to the satellites should be minimized to make sure the network can handle as many ground devices as possible.

+ Often the date rate from satellite to ground device is limited because the ground device use a more or less omni-directional antenna with limited antenna gain to compensate for its inability to track a passing satellite.

+ It is mandatory for IoT operators to be able to push firmware upgrades to ground devices in case a security hole is threatening the network and possibly the operation of the network.

In this realistic scenario simply broadcasting a file again and again until each device has received all data will require a large overhead to make sure all 1000's of ground devices have received the complete file.

Even a small likelihood of a lost packet will - given the high number of ground devices - result in some devices waiting for certain parts of the transfer even after the file has been broadcast to all the devices multiple times. It is also easily shown that by repeatedly broadcasting a file each ground device will receive a lot of duplicates of data while hunting for its missing parts wasting scarce battery power.

With 1000's of ground devices it is as well unrealistic to rely on legacy broadcast or multicast protocols (like FLUTE and UFTP) where each ground device can report back and tell which parts of a file it is missing. The transmission overhead from reporting back and retransmitting parts of the file to individual ground devices can easily be shown to congest a network if the number of connected devices are just a few hundred. So for satellite IoT networks such methods are not viable.

OTAcast solves the above problems elegantly by

+ Making sure every piece of data received is useful in recreating the file at the ground device

+ Making sure there is no need for a return channel to request missing parts.

In this way every piece of data received from any satellite is helping complete the reception of the firmware file irrespective of the time of the day or position of the device. If a piece of data is lost the receiver just needs to receive another piece of data. i.e. the ground device only needs to collect a certain amount of data to recreate the file and it never ends hunting for a certain piece of the file. In this way the need for a return channel is eliminated, and it can be guaranteed that all devices will receive the file with the least overhead possible.

OTAcast transforms a file into a linear equation system, and the equations are broadcast instead of the individual parts of the file. When enough equations have been received by a ground device the linear equation system can be solved and the file recreated.

OTAcast becomes more effective the more devices and the bigger the file, which makes OTAcast a future proof scalable solution to broadcast information to big populations of ground devices. As well OTAcast is the most robust solution when the error rate for the satellite link increases.

The transformation of a file to a set of linear equations will only add 1% to the file size, but an almost unlimited number of equations can be generated for extending the period broadcasting the file.

Simulations show it is 10-20 times faster to broadcast a file using OTAcast to a large population of ground devices compared to other methods of broadcasting. In most cases OTAcast is the only practical solution to upgrade big populations of ground devices, because a firmware update can be done in all devices in a few days instead of weeks or even months.

In addition to pushing firmware updates to ground devices the applications for OTAcast is in broadcasting map updates to ships - like weather or ice maps and broadcasting films and documentaries in welfare solutions for ships or other applications where data need to be shared with many ground devices.

Related Links
OTAcast at Steinwurf
VSAT News - Suppliers, Technology And Applications

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