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Modulated Reflectance

The new issue of Wireless Business & Technology is running a story on modulated reflectance, a new technology under development at Los Alamos National Labs. The idea is simple in concept: a base station-wireless node link in which the wireless link transmits by reflecting a modulated version of the base station's signal back to it. Los Alamos' name for this technology is INFICOMM:

I first learned of this scoop from an old acquaintance named Ron Dennis who's consulting at Los Alamos...

Today, Wi-Fi uses radio frequency (RF) technology to interact. A base station pings my notebook computer using its power source. My WLAN card takes a big toke on the notebook battery, then replies...

INFICOMM promises to replace RF with something the scientists call modulated reflectance. A modulated reflectance­-equipped base station will be able to signal your INFICOMM wireless device, which in turn reflects back to the base station without using a single microwatt of your device's battery.

"If you're looking at a rose with a flashlight in the dark," Ron illustrates, "the rose isn't transmitting."

Los Alamos has a document (PDF format; Google's HTML version is here) that goes into more detail:

The fundamental principle of modulated reflectance works much like sunlight reflecting off of a mirror. A transmitter-receiver base unit emits carrier waves of RF energy, and each remote wireless device (a receiverreflector) would modulate these waves to correspond to the voice/data signal and reflect them back to the tower. The transmitter-receiver base unit would then receive these modulated waves. Thus, half of the duplex "conversation" is transferred from the remote unit to the base unit using modulated reflectance, while the other half is transferred from the base unit to the remote wireless unit using conventional RF energy techniques.
The document goes on to describe two forms of modulated reflectance. One form is a "pure system," in which "the remote wireless unit requires no transmitter power," but which requires changes both to the base station and mobile device. The other form is a "hybrid system:"
In this design, a cellular telephone uses modulated reflectance to reduce the power consumption of the battery but also retains standard transmission modes of operation, much like a standard cell phone, as a supplement to the reflected signal. Enhancement of the battery-charge life is expected to be highly significant and radiation exposure to the user is reduced. All of the "magic" in this system is in the handset.
Could this be the breakthrough we so desperately need for mobile wireless battery life?

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