It's so easy to connect a device today via Wi-Fi to your local network. Engineers design it
into their device hardware platform and you can even add it to any device that has a USB port by plugging in a small Wi-Fi dongle (that's what I use on my Raspberry Pi). But as we start communicating with more and more devices a couple of issues become important:
Since all of these devices are actively transmitting on the narrow Wi-Fi RF band, they
will eventually interfere with each other. They will interfere in the radio signal domain, and they will also interfere in the network packet exchange domain.
Also many of these devices will be battery-powered (or even micro powered by motion or piezo generators. We all know that you can extend battery life on your phone or laptop if you turn off the Wi-Fi. Most of the functional circuitry on newer tiny devices use power in the milliwatt (or even microwatt) range. It is completely impractical to use 20 or so milliwatts of power just to communicate.
Here is where a fresh new technology might save the day. MIT Technology Review listed
passive Wi-Fi as one of the top 10 new breakthrough technologies for 2016. This new technology makes it possible to use 10,000 times less power for Wi-Fi transmissions (tens of microwatts versus tens of milliwatts). From an engineering standpoint that will usually be far below the power that the device uses for its particular functionality. It makes communication practically free from a power point of view. Some of the most recent work on this is being done at the University of Washington and the scientists and engineer researchers have published their results in this paper. They will also be presenting the results at the 13th USENIX Symposium on Networked Systems Design and Implementation this March.
The data rates that have been achieved so far are up to 11 Mb per second, but before you complain that that is slower than regular Wi-Fi remember that it is still much faster (about 10 times) than Bluetooth, and at very low power, and it can communicate with billions of other devices that use Wi-Fi.
All of this is very cool, but of course it isn't magic. All of your very low power communication devices rely on one powered (plugged into the wall?) Wi-Fi transmitter somewhere in the area. What the passive system does is alter the reflection and absorption of the existing central signal and it is the alteration of that existing signal that carries the information. It's been demonstrated to work over a range of 100 feet. And it's important to stress that these altered signals are actual Wi-Fi packets: any existing Wi-Fi device can use them without modification. What could be better than having new and improved technology that plays perfectly fine with the existing infrastructure?
One interesting question is: what will happen to Bluetooth and ZigBee? Passive Wi-Fi uses much less power, has higher transmission rates, and works just fine with regular Wi-Fi. Why have a Tower of Babel with three standards and the attendant hardware and radio infrastructure cost? Why don't we just do it all with Wi-Fi?