Reading thousand sensors in the blink of an eye

A cyber-physical system is formed by a network of interacting sensors and actuators. With the availability of small inexpensive sensor elements, such a network may contain thousands of interacting sensors. This makes such systems a little bit similar to biological systems. For example, the human body has 3 billion touch sensor cells. Still a notable difference though.

However, even for a few thousand sensors, conventional communication methods come into trouble. With a typical network, it takes too long to transmit such a large number of sensor measurements.

In the paper “A Scalable and Efficient Approach for Obtaining Measurements in CAN-based Control Systems” scientists from Portugal and Austria present a solution to this problem by polling many sensors at once while actually transmitting only one representative measurement.

Example for a priority-based medium access control; "0" is dominant over "1"

The idea is based on so-called priority-based medium access control protocols:

  • the message consists of a number of bits, each bit being 0 or 1 (any message can be encoded that way)
  • when the bits are sent via transmission medium, one of the states can overwrite the other (for example if 1 overrides 0, then a synchronously transmitted 1 and 0 result in a 1)
  • all sensors start their transmission at the same time, for example triggered by a query message
  • a transmitting sensor monitors its own transmission; if a bit gets overwritten it immediately stops transmission. This way it is possible to get the largest value (or by inverting the messages, the lowest value) of a number of sensors with a single query. If there are thousands of sensors, the protocol definitely pays off.

A few sensor measurements (green) with high information content are sufficient to interpolate the overall dataset

Andersson, Pereira, Elmenreich, Tovar, Pacheco and Cruz employ this method to get a map of sensor readings with just a few messages. The priority-based protocol is here used to select the sensor messages with high information content. This approach greatly reduces the time for obtaining sensory information, which makes cyber-physical systems ready for use in fast control systems.

The full paper is available as a technical report. It was published in the highly respected IEEE Transactions on Industrial Informatics:

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About Wilfried Elmenreich

Understanding the communication networks of the future.
This entry was posted in Embedded Software, Protocols, Real-Time Networks, Sensor Fusion and tagged , , , . Bookmark the permalink.

One Response to Reading thousand sensors in the blink of an eye

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