Generally, we do not think about power consumption issues when we use WiFi networks. It may be sometimes painful for our smartphones, but mobile data transmission also reduces battery life. However, high power consumption level of WiFi modules is very problematic for IoT (Internet of Things) devices.
The solution developed by the researches and students from University of Washington may be the revolution for IoT. The main problem of WiFi modules is the fact, that RF (Radio Frequency) part consumes a lot of power, because it contains power amplifier which is required to generate strong WiFi signal. However in recent years, great progress in the reducing of power consumption of integrated circuits (e.g. base-band part of WiFi module) has been made. Therefore, the idea of Passive WiFi is to isolate RF part and baseband part and use modules which do not have power consuming RF components.
How does it work? The idea is that Passive WiFi module generates WiFi packets by reflecting the normal WiFi signal and adding its own data on top the carrier transmitted by the standard WiFi router or delegated plugged-in device. Very interesting is the performance of Passive WiFi solution. Tests of prototype modules prove that this solution is able to transmit data with all four 802.11b bit rates (i.e. 1 Mbps, 2 Mbps, 5 Mbps and 11 Mbps) over distances of 9 – 30 meters in various line-of-sight (i.e. without any obstacle) and through-the-wall scenarios. As you can see, it is the perfect replacement of Bluetooth for IoT devices. All details of Passive WiFi solution are described in this article.