NASHUA, N.H. — A radio-frequency sensor does not have to sit at a fixed site or on a large military platform. Make the equipment small enough, and an individual soldier can carry it. 

A wearable RF sensor can warn the person holding it about nearby activity. Connect sensors carried by multiple soldiers with equipment on vehicles and at fixed sites, and those individual observations can also contribute to a larger picture of the electromagnetic environment.

The idea is to put sensing in more places and allow those sensors to share what they find. Making all of that information useful is the harder engineering problem.

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One sensor can become part of a larger network

A soldier carrying an RF sensor can detect emissions and receive a local warning. Now imagine several soldiers spread across an area carrying similar equipment. A signal detected by one sensor may also reach sensors in other locations.

“Every soldier carrying one becomes a node,” said Bill Ostrowski of MyDefence. “On its own, a node gives personal warning. Networked, several nodes see the same emitter from different positions, and that is what allows you to locate the operator rather than only the aircraft.”

Connecting those nodes allows a detection to become useful beyond the person who encountered it first. Sensors aboard vehicles and at fixed positions can contribute information in the same way.

“Aggregated across a battalion and over time, you get pattern of life: where operators set up, at what hours, using which waveforms,” Ostrowski said. “That is intelligence with planning value, not only alerting value.”

Processing can move closer to the sensor

A distributed architecture also changes where information gets processed.

Instead of requiring every observation to travel to a central location before it becomes useful, some analysis can happen on or near the sensor itself. The local device can provide information to its user while also contributing relevant data to a broader network.

“It is not decentralisation replacing centralisation,” Ostrowski said. “It is the same intelligence, present at every level, connected.”

That distinction becomes particularly important when communications are disrupted.

“Each node is useful alone and more useful in company, so if connectivity is lost the network degrades gracefully instead of failing as a whole,” Ostrowski said. “The soldier keeps their own protection either way.”

Twelve detections should still look like one threat

More sensors also create more data to sort out. If 12 RF sensors detect the same emitter, the warfighter should not receive 12 warnings suggesting that 12 different threats have appeared.

“One emitter seen by twelve sensors has to be presented as one threat, not twelve,” Ostrowski said.

Doing that requires the system to determine which observations correspond to the same source.

Timing matters because sensors may encounter the signal at different moments. Location matters because the nodes themselves can be spread across an area and may be moving. The system also has to exchange enough information to compare those observations without overwhelming a tactical network with unnecessary data.

“Time and position have to stay synchronised across nodes that are all moving, under bandwidth constraints and in contested communications,” Ostrowski said. “Confidence has to be conveyed without a lecture in probability.”

Different sensors still have to tell one story

RF sensors may also be only one part of the network. A counter-UAS system can receive observations from radar, acoustic sensors and electro-optical or infrared equipment. Those sensors measure different characteristics of the same environment, and more than one may detect the same aircraft.

“The soldier does not need to know which sensor spoke,” Ostrowski said. “They need to know that something is there, from which direction, and how urgent it is.”

That requires the system to correlate observations that may describe the same object before presenting them to the user. The engineering work happens behind the interface rather than forcing the warfighter to interpret several separate feeds.

“The measure of a well-designed system is that the complexity disappears before it reaches the soldier, and what arrives is a single, consistent warning they can act on in seconds,” Ostrowski said.

Wearable electronics come with physical limits

Moving that capability onto an individual soldier introduces another set of constraints. A wearable system has to compete for space and weight with everything else a warfighter already carries. Improving one part of the sensor can also affect another.

“Engineering for the soldier is a series of trades where nothing is free,” Ostrowski said. “More sensitivity costs power. More processing costs heat. More battery costs weight.”

Engineers therefore cannot maximize every specification independently, and the equipment still has to be practical enough that carrying it does not interfere with the soldier's primary job.

That requirement becomes even more important for distributed sensing. The concept gains much of its value from putting sensors across a formation rather than assigning a single specialized system to one operator.

A technically impressive sensor that is too large, heavy or power-hungry to deploy widely can undermine that advantage before the network is ever built.

For Ostrowski, that reduces the engineering problem to a practical question:

“The right question is not how much capability you can fit on a soldier. It is how much you can fit before the soldier stops wearing it.”