Passive Wi-Fi, a new technology that reduces the power consumption of Wi-Fi to one ten-thousandth It is likely that the Internet's long-lasting battery will come closer to the Internet

A new technology to solve the weak point of Wi-Fi, which was conventionally considered as "large power consumption" was developed. Developed by the research team of the University of Washington "Passive Wi-Fi"Can provide the maximum required power without affecting the communication speed,It can be drastically reduced to 1 / 10,000In addition to being able to reduce the battery consumption of smartphones and others,Internet of things(A society in which things are connected to the Internet) is becoming popular.

Passive Wi-Fi
http://passivewifi.cs.washington.edu/

Researchers create super-efficient Wi-Fi | Ars Technica
http://arstechnica.com/information-technology/2016/02/researchers-create-super-low-power-wi-fi/

In order to understand the mechanism of Passive Wi-Fi, it seems better to mention the communication technology used here. Passive Wi-Fi is a little different from general Wi-Fi, it is a technology to communicate by "reflecting" Wi-Fi waves that are flying. The meaning of expressing data by reflecting ambient radio waves (backscatter)Ambient BuckcaterAlthough I am using a technique called "The details, please understand if you read the following article.

What is the technology "WiFi Backscatter" that is optimal for IoT capable of wireless communication without battery? - GIGAZINE


Ambient Buckcater exploits the stealth technology used for fighter aircraft and creates states of "0" and "1" by reflecting or passing radio waves emitted from Wi - Fi router etc, It is to make it possible. Since we do not emit radio waves, we do not need electric power and the electric power necessary for switching between "0" and "1" can be covered by converting the jumping radio waves into energy.


Passive Wi - Fi is what developed this mechanism. It is possible to check from the following movie, etc. how it works and how it works.

Passive Wi-Fi - YouTube


Device with passive Wi - Fi device with antenna that can be seen in front. Beyond that, a staff member of a research team with a smartphone is sitting.


On the screen of the smartphone, the passive Wi - Fi device name "Passive_Wi - Fi - 1" is displayed, and it can be confirmed that it is operating as a normal Wi - Fi terminal.


Explain why Wi-Fi consumes much power. A typical Wi-Fi device has "baseband" for processing digital signals and "RF (high-frequency signal transmitter)" for converting signals to analog signals and emitting radio waves.


Among these,Moore's lawThe baseband portion that advanced along with power saving is progressing, achieving micro watt level low power. Meanwhile, it is difficult to reduce the power of analog parts that can be said to have been withered already, and it is inevitable to consume about 100 milliwatts of electricity. This is a very painful part for mobile terminals such as smartphones and at the same time, one of the reasons why it is difficult to utilize Wi-Fi in the "Internet of things" which is often difficult to install batteries It is accompanied.


Therefore, the idea that the research team devised is responsible for the device that the power supply can be supplied to the RF part, and the passive device (passive device) that actually uses Wi-Fi is handling the baseband It is intended to reduce power consumption by mounting only. Here, the above-mentioned ambient / backcatcher technology will be useful.


The operation of Passive Wi-Fi is as follows. Receive power from the outlet, send base radio waves from the transmitter that can emit as much as you want. This radio wave also reaches the passive type device equipped with the baseband.


Passive type device creates digital signal (packet data) by turning on / off reflection of radio waves and delivers data to the partner (Wi - Fi Receiver) you want to communicate. This means that we are named "Passive Wi - Fi (passive Wi - Fi)" from the mechanism that utilizes radio waves from others without emitting radio waves.


The research team succeeded in communication at 1 Mbps to 11 Mbps using this mechanism. That is, the wireless LAN standard "IEEE 802.11bIt means that communication according to "is already possible. Also, the necessary power is 15 to 60 microwatts. This is about one ten thousandth of the general Wi-Fi, which is characterized by power savingBLE(Low power Bluetooth) andZigBeeIt is about 1 / 1,000 level compared to the level.


Passive Wi-Fi can also be used with multiple devices. A radio transmitter is placed on the right side of the screen, and two passive Wi - Fi devices are placed on the desk. These devices have different SSIDs assigned to them.


On the screen of the smartphone, two device names "Passive_Wi-Fi_ 0" and "Passive_ Wi-Fi_ 1" are displayed, and it is confirmed that both devices are working normally.


With this technology, it will be realistic to conserve energy on smartphones and to incorporate Wi - Fi into the Internet 's Internet. Particularly, there is a merit that Wi-Fi technology can be used to directly use the security technology of Wi-Fi.


By incorporating sensors and Passive Wi - Fi devices in coffee machines and paper towel holders, the realization of a ubiquitous society that can automatically display "shopping list" on smartphones may be even closer. It seems possible to utilize Wi-Fi at a different level than before.