Ambient Backscatter

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tzs · 2023-09 · Reference

It is not just ambient electrical noise that contains usable energy. Others have demonstrated practical sensor energy harvesting from ambient WiFi and ambient broadcast TV signals. I'd expect that the Sony device can probably use those too, so if you've got WiFi in your building you should be fine. If there is ambient radio, you can also use that for extremely low power data transmission from your sensors. The trick there is to not actually transmit any of your own energy. You instead either absorb or reflect the ambient radio. This is called backscatter communications. Here is a video showing a demonstration of both energy harvesting from ambient radio and backscatter data transmission [1]. If you use WiFi signals as your ambient radio for backscatter, the research group in that video has also demonstrated that you can make your backscatter data stream match standard WiFi protocols so that you can use ordinary WiFi equipment for the receiver. The above was fairly short range, but even so there are a lot of interesting applications. For instance you might want to have moisture sensors inside a wall to detect water leaks early. If your sensors are powered by ambient EM energy (noise or radio), you don't have to limit the sensors to places where you can easily reach them later to change batteries. They are fine if they are behind brick or drywall with no openings. [1] [VIDEO]

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tzs · 2021-05 · Reference

If you don't need much range (a couple feet, say), you can use ambient backscatter which doesn't need to store up energy for bursts. Here's a video about it from 2013 [1] showing some test devices. Here's an article about it [2]. A bit later they extended this to make it work with off-the-shelf WiFi devices, so you could have a battery-free device that can communicate to ordinary WiFi devices [3]. Still short range, but now you could make it so the reader is a commodity WiFi device like a smartphone, instead of a specialty device. Here are some other researchers who demonstrated a backscatter tag that diddled with Bluetooth Low Energy (BLE) instead of WiFi, and was correctly received by an iPad at over 9 m using the existing iOS Bluetooth stack with no modifications [4]. And here is a battery-fee phone that communicates with a powered base station [5]. It works up to 30 ft away. The phone uses energy from ambient RF and small photodiodes. [1] [VIDEO] [2] [LINK] [3] [LINK] [4] [LINK]

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baldfat · 2017-12 · Reference

No I quoting a fact not an opinion. Please read my comment and sources before claiming I am factually wrong. "In this backscatter system, an antenna embedded in a 3-D printed object (middle) reflects radio signals emitted by a WiFi router (left) to encode information that is “read” by the WiFi receiver in a phone, computer or other device (right).University of Washington" Screenshot: [LINK] > They're not magically encoding new Wi-Fi packets Yes, these are NEW signals powered by the radio signals that specifically in this article is wifi since it is so widely used. "The chip uses a technique called long-range backscatter to communicate with other devices. Instead of creating signals from scratch, it is able to selectively reflect radio waves that are already passing through space to create a new signal." [LINK] Just because they are using residual radio signals (They could use TV, Wifi or FM signals) doesn't mean the new singals aren't new. They are just using the energy in the signal itself doesn't make them magic. Instead of using electricity from a battery or a cord they are using the power of the radio wave. They can even power themselves off of the Gollakota’s radio frequency power scavenging technology. You could light up a led without any on board electricity and communicate between two devices [VIDEO] Here is a speech about HitchHike: Practical Backscatter Using Commodity WiFi at (SenSys 2016) [LINK]

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