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Researchers Make Low-Power Wi-Fi Breakthrough (networkworld.com)
alphadogg writes: The biggest downside of Wi-Fi for most users might be that it can really drain your smartphone or tablet battery, but a research team at the University of Washington has come up with a way to make using the nearly ubiquitous wireless technology in a less taxing way. They have demonstrated a technique for using 10,000 times less power than typical Wi-Fi (well, at up to 11Mbps anyway) and next month will present a paper titled "Passive Wi-Fi: Bringing Low Power to Wi-Fi Transmissions" at the USENIX Symposium on Networked Systems Design in Santa Clara. The main trick involves decoupling digital and analog components of a typical Wi-Fi router.
Blazing speed and low power are less important to me than long range. And these router manufacturers are getting rather annoying with their "specs." Oh, it covers 14,000 square feet. That's a square less than 120 feet on a side. So what? That's what you get for 600 mW of output power?
It's not that it takes orders of magnitude less power, it's that they move the power-consuming-part to a device that isn't relying on a battery.
Here's a comparison:
Back in my grandfather's day, two kids who live on adjacent farms might use flashlights to "talk" to each other at night using Morse Code over distances of several hundred meters. But the flashlight batteries only had so much juice. But what if, instead of using flashlights, they used lenses and mirrors so they light source was a lamp that was plugged into the electrical outlet? They could talk all night and not use up any batteries at all.
Well, that's the gist of these devices. The "low power battery-operated devices" still need batteries to do the equivalent of "manipulating the lenses and mirrors" and operating an RF receiver, as well as whatever other task they are supposed to be doing (say, monitoring for pollution, or whatever).
They key is that they don't need to waste energy operating an RF transmitter - that work is done by a nearby device that has a reliable energy source.
That, and several "low power" devices can "share" the same transmitter.
Something not noted in the summary: Depending on the scenario, this may result in a net increase in power consumption if the "shared transmitter" is in a naive, "always on" mode compared to a conventional system where the transmitter(s) would only be on when needed. I'm not saying you can't design such a system that isn't "naive," just that if you do, your total power usage may be higher than a conventional system. But since you are "plugged in" and not on battery, it the "cost" may be negligible.
Bottom line: It's a neat and useful trick and if "mains power" is "many times cheaper than battery power" for your application, this is a big win. On the other hand, if "overall power used" is the controlling factor, it's not such a big win and if you aren't careful, it could be a big loss.
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
from the article "This translates to 10000x lower power than existing Wi-Fi chipsets and 1000x lower power than Bluetooth LE and ZigBee."
The system works by remodulating the poweful carrier from a transmitter to shift it's frequency. Thus it doesn't need much power itself, it is just reflecting the power from a powerful source. The set the powerful source frequency just outside wifi channel frequncy and the reflected modulated signal is shiften inband. this lets an existing wi-fi receiver pick up the signal. Thus it works with conventional wiFi systems without them having to be aware they are communicating with a low power device. I believe it will require the addition of the high power transmitter of the carrier that is being passively reflected.
Some drink at the fountain of knowledge. Others just gargle.
Let's hope for a wireless mouse that no longer needs batteries every time you pick it up.