Future Spy Cameras Could Steal Power from Your Home WiFi Signals

Researchers working at the University of Washington appear to have become the first to harvest power using signals from home WiFi devices operating in the 2.4GHz radio spectrum band (note: an Asus RT-AC68U router was used for the demo), which allowed them to power several devices including a tiny camera.

The idea of harvesting power from existing wireless signals is nothing new, although the PoWiFi system mentioned here is the first to demonstrate this ability using signals from existing WiFi hardware. As part of this project several small devices were developed to test the system, including a battery free camera (picture), temperature sensor and two battery chargers.

Initially the paper suggests that the team could not reach the minimum voltage of 300mV needed to operate their harvesting hardware because the signals were too variable, which made it difficult to sustain the needed set level of power. But this was solved by modifying the WiFi transmissions to broadcast a sustained signal even when there wasn’t much/any data being transmitted.

Research Paper (Extract)

We present the first power over Wi-Fi system that delivers power and works with existing Wi-Fi chipsets. Specifically, we show that a ubiquitous piece of wireless communication infrastructure, the Wi-Fi router, can provide far field wireless power without compromising the network’s communication performance.

Building on our design we prototype, for the first time, battery-free temperature and camera sensors that are powered using Wi-Fi chipsets with ranges of 20 and 17 feet respectively. We also demonstrate the ability to wirelessly recharge nickel–metal hydride and lithium-ion coin-cell batteries at distances of up to 28 feet.

Finally, we deploy our system in six homes in a metropolitan area and show that our design can successfully deliver power via Wi-Fi in real-world network conditions.

The demonstration was designed in a way that didn’t affect the normal performance of the home WiFi network, although obviously there would be limits to how much power you could “borrow” before it did begin to create problems. Similarly some of the power saving characteristics of WiFi might be compromised by the PoWiFi approach.

Apparently PoWiFi can harvest power from multiple 2.4GHz Wi-Fi channels and the research suggests that it may also be possible to combine multiple ISM bands (e.g. 900MHz, 2.4GHz and 5GHz) to optimise the system and deliver even more power.

But without strict controls we could see parasitical power harvesting as also creating some new problems, such as with regards to the question of legality when stealing somebody else’s wireless power without their permission.

The paper also mentions a number of security implications, such as a hypothetical Power Denial-of-Service (PDoS) attack in which a rogue device causes power starvation for other members of the network. Never the less this is an interesting development and one to watch.