Tag Archives: backscatter

WISP – Re-programmable Microcontroller That Runs On Energy Harvested From Radio Waves

A new research initiative between the University of Washington’s Sensor Lab and the Technical University of Delft in the Netherlands has created a microprocessor that can power itself through stray radio waves and receive programmable updates in the same fashion. While the RISC-derived 16-bit microcontroller CPU is very weak compared to modern standards, it’s much more powerful than any other device that’s powered by ambient energy in the environment with no battery required.

The WISP 5 - Microchips and sensors run from radio wave's energy
The WISP 5 – Microchips and sensors run from radio wave’s energy

This battery-free system is equipped with a sensor and a microchip, which can be powered entirely by radio waves harvested from the air and is up to 10 times faster than similar ambient-powered devices. Best of all, in contrast to similar devices, it can also download executables, allowing it be reprogrammed or upgraded to newer version of firmware whenever needed. This has significant implications for the Internet of Things development and for ambient computing as a whole.

The variety of handheld, portable technology, and wearable gadgets available today is truly amazing. In order to make devices even more compact and thinner, manufacturers typically try to shrink their designs as much as possible. Unfortunately, device size is ultimately limited by the batteries, all of which have a certain capacity before they dry out and must be recharged again. It is a challenge for engineers and designers to balance battery life with function and aesthetics.

The project of radio wave-driven microcontroller is dubbed WISP, or Wireless Identification and Sensing Platform. RFID (CRFID) technology is an example of  WISP. In particular, WISP is capable of being powered passively by converting radio frequencies emitted by conventional RFID (radio frequency identification) readers into electrical power. The project’s latest accomplishment is the addition of Wisent (short for “wirelessly sent”), a faster and more reliable downstream communication-oriented protocol for CRFIDs that can tolerate fluctuations in operating power.

The WISP is constructed out of an open source, open architecture EPC Class 1 Generation 2 RFID tag that incorporates a fully programmable 16-bit microcontroller, in addition to any add-on sensors. It differs from ordinary RFID tags as it is programmable, and can be multi-functional. The team writes in their research paper,

The novelty of Wisent is its ability to change adaptively the frame length sent by the reader, based on the length throttling mechanism, to minimize the transfer times at varying channel conditions. Wisent enables wireless CRFID reprogramming, demonstrating the world’s first wirelessly reprogrammable CRFID.

Researchers Develop Long Range Backscatter Sensors That Consume Almost No Power

Researchers at the University of Washington developed a new backscatter sensors that can operate over long ranges with very little power. The researchers demonstrated for the first time that the device runs on almost zero power and can transmit data across distances of up to 2.8 kilometers.

The long-range backscatter system developed by UW researchers
The long-range backscatter system developed by UW researchers

Backscatter communication works by emitting a radio signal and then monitoring the reflections of that signal from sensors. As the transmitter generates the signal, the sensors themselves require very little power. But this kind of system badly suffers from noise. Noise can be added anywhere – on the transmitter side, on the channel or on the sensor array. The key to solving this problem is a new type of signal modulation called chirp spread spectrum.

By using the chirp spread spectrum modulation technique, the team was able to transmit data up to 2.8 kilometers while the sensors themselves consumed only a few microwatts of power. Such extremely low power consumption lets them run by harvested ambient energy and very small printed batteries. The cost is surprisingly cheap too. The sensors would cost just 10 to 20 cents per unit if bulk purchased.

Today’s flexible electronics and other sensors need to operate with very low power typically can’t communicate with other devices more than a few feet or meters away. By contrast, the University of Washinton’s long-range backscatter system achieved pretty strong coverage throughout a 4800-square-foot house, an office area including 41 rooms, and a one-acre vegetable farm at extremely low power and low cost.

Shyam Gollakota, the lead faculty and associate professor in the Paul G. Allen School of Computer Science & Engineering, said,

Until now, devices that can communicate over long distances have consumed a lot of power. The tradeoff in a low-power device that consumes microwatts of power is that its communication range is short. Now we’ve shown that we can offer both, which will be pretty game-changing for a lot of different industries and applications.

These low-power sensors have endless potential applications. They can be used for everything from wearable health monitors to scientific data collection devices. Though there are no confirmed products yet, the team has created few prototypes in the form of flexible sensors worn on the skin, smart contact lenses, and more.