The researchers have been focusing on the most efficient way to reprogram these simple machines. In some situations it may be relatively easy. For instance, emergency responders may decide they want a sensor network that’s monitoring air quality every 15 minutes to start doing it every minute. This would require a fairly simple change for the sensor. A more complicated scenario would involve more extensive reprogramming, replacing parts of the existing program. The most significant type of retasking involves replacing the entire program on the sensor network.
Researchers are striving for two goals as they work on retasking. The first is speed. “In the context of emergency management, there’s an advantage to doing this as quickly as you can,” Hallstrom said.
The second challenge is how much energy the change uses. Transmitting data wirelessly is the largest power consumer for these remote networks. “You have a very small energy budget,” Hallstrom said, and it has to be managed well. The less sent over the network, the better.
The group hopes to find efficient protocols and programming mechanisms to retask large-scale sensor systems, Hallstrom said.
Other questions the group is trying to answer:
- How do you know how many sensors are needed for a particular task? Sometimes it may be that a sensor network can’t do a particular task because it doesn’t have enough sensors. Other times, if there are more than enough to give a reliable result, some of the sensors could be used to monitor other things.
- How long does a sensor network need to get a particular result before the software reports an incident like a fire? “You want it quickly but also with as high confidence as possible,” Weigle said. “We’re doing theoretical work to look at what the tradeoff point is.”
- How frequently should sensors report their results? Sensors can be programmed to simply report their results at regular intervals. But since reporting uses energy, conserving power is key. So researchers are looking at different ways for sensors to determine how frequently to report their data.
One last area the team is still investigating is cost. Since the idea is to use existing networks, there should be few additional infrastructure costs, although there would be costs for developing and deploying the necessary software.
Figuring out how to keep the costs down while moving the networks to new uses is just one of the challenges that keeps the team going.
“This is ongoing, exciting work,” Olariu said.