Battery-Free Wireless System

Anyone with a mobile device has likely experienced the frustration of having to be reliant on a battery. The charge never lasts long enough, and finding a source of electricity on the run is a hassle. Researchers at the University of Washington have come up with a solution to modern tech troubles with their new communication technique called “ambient backscatter”.

What does ambient backscatter do? And what makes it battery-free?

Ambient Backscatter transforms existing wireless signals into both a source of power and a communication medium. Since it leverages the ambient RF signals that are already around us, it does not require a dedicated power infrastructure; hence, making it a battery-free technology.


Further Discussion:
As computing devices become smaller and more numerous, powering them becomes more difficult; wires are often not feasible, and batteries add weight, bulk, cost, and require recharging/replacement that is impractical at large scales. Ambient backscatter communication solves this problem by leveraging existing TV and cellular transmissions, rather than generating their own radio waves. This novel technique enables ubiquitous communication where devices can communicate among themselves at unprecedented scales and in locations that were previously inaccessible.

Ambient Backscatter transforms existing wireless signals into both a source of power and a communication medium. It enables two battery-free devices to communicate by backscattering existing wireless signals. Backscatter communication is orders of magnitude more power-efficient than traditional radio communication. Further, since it leverages the ambient RF signals that are already around us, it does not require a dedicated power infrastructure as in RFID.

Ambient Backscatter

To understand ambient backscatter in more detail, consider two nearby battery-free devices, Alice and Bob, and a TV tower in a metropolitan area as the ambient source, as shown in Fig. 1. Suppose Alice wants to send a packet to Bob. To do so, Alice backscatters the ambient signals to convey the bits in the packet—she can indicate either a ‘0’ or a ‘1’ bit by switching her antenna between reflecting and non-reflecting states. The signals that are reflected by Alice effectively create an additional path from the TV tower to Bob and other nearby receivers. Wide-band receivers for TV and cellular applications are designed to compensate for multi-path wireless channels, and can potentially account for the additional path. Bob, on the other hand, can sense the signal changes caused by the backscattering, and decode Alice’s packet.

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