WiFi is now ubiquitous, in the sense that many devices have WiFi embedded and there are millions of WiFi areas all over the world. A 2015 statistics indicated over 50 million public WiFi hot spots in the world with an expected growth to 340 million by 2018 (that is one hot spot every 20 people, but of course this is an average that means very little in many Countries in Africa and Asia...). Add to these the private WiFI areas that are basically present in every home with a ADSL/Fibre access and the ones that can be generated by smart phones to tether other devices and you are in the billion hot spots.
The problem with WiFi is that it requires quite a bit of power and in case of a mobile device it drains the battery. Alternative communications means, like ZigBee, are less power hungry but much less widespread.
Hence the interest for this news coming from the University of Washington where a team of researchers have managed to create what they call a passive WiFi showing a power consumption that is 1/10,000 of a normal WiFi. It is also 1,000 times better than alternative communications, like Bluetooth low energy and ZigBee.
That's impressive! And, indeed, it has been named among the top ten breakthrough technologies for 2016 by MIT.
The approach used is amazing. Rather than emitting a radio-wave signal, which requires power, the system piggy back on existing radio-waves (that are ubiquitous, given the amount of radio communications all over the world, think about television signals) and modulate the WiFi signal on those waves. It is like using a mirror to reflect Sun light and hence coding a signal on it, as opposite to light a lamp to generate a light signal. It is clearly much more efficient to piggy back on Sun light!
They have demonstrated the principle (they use backscattering technology) and proved that one can indeed have a passive (not powered) device piggy back on an existing WiFi hot spot. They only need to change a bit the software in the hot spot. The increase in power consumption by the hot spot is marginal and there is no power needed by the device to piggy back on the WiFi signal generated by the hot spot (since it uses that signal to power up its circuits.
This, in a 2-3 years timeframe, should bring to the bit Internet many sensors that would have been difficult to deploy because of power requirement.