Passive Wi-Fi is a refinement of

Wi-Fi Wi-Fi () is a family of wireless network protocols based on the IEEE 802.11 family of standards, which are commonly used for Wireless LAN, local area networking of devices and Internet access, allowing nearby digital devices to exchange data by ...

technology that uses passive

reflection Reflection or reflexion may refer to: Science and technology * Reflection (physics), a common wave phenomenon ** Specular reflection, mirror-like reflection of waves from a surface *** Mirror image, a reflection in a mirror or in water ** Diffuse r ...

to reduce energy consumption.

Wi-Fi energy use

Wi-Fi use can account for up to 60 percent of a

smartphone A smartphone is a mobile phone with advanced computing capabilities. It typically has a touchscreen interface, allowing users to access a wide range of applications and services, such as web browsing, email, and social media, as well as multi ...

's energy consumption. When not connected to a network, Wi-Fi consumes energy because the device constantly searches for a signal.

Backscattering

The technique communicates via

backscattering In physics, backscatter (or backscattering) is the reflection of waves, particles, or signals back to the direction from which they came. It is usually a diffuse reflection due to scattering, as opposed to specular reflection as from a mirror, ...

, reflecting incoming radio waves sent from a separate device. The technique is similar to contactless

RFID chip Radio-frequency identification (RFID) uses electromagnetic fields to automatically identify and track tags attached to objects. An RFID system consists of a tiny radio transponder called a tag, a radio receiver, and a transmitter. When trigg ...

cards although unlike such cards, the new technique does not require a special device to read the signal. The project effectively decoupled the analog and the digital radio signals. Power-intensive functions – like producing a signal at a specific frequency are assigned to a single device in the network that is plugged into the grid. Smartphones modify and reflect this signal to communicate to the router. Prototype passive devices transferred data as far as 100 feet through walls at 11 megabits per second. The system used tens of microwatts of power, 10⁻⁴ less energy than conventional Wi-fi devices, and one thousandth the energy of

Bluetooth LE Bluetooth Low Energy (Bluetooth LE, colloquially BLE, formerly marketed as Bluetooth Smart) is a wireless personal area network technology designed and marketed by the Bluetooth Special Interest Group (Bluetooth SIG) aimed at novel applications i ...

and

Zigbee Zigbee is an IEEE 802.15.4-based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios, such as for home automation, medical device data collection, and oth ...

communications standards.

Applications

Applications include smart home devices such as

smoke detectors A smoke detector is a device that senses smoke, typically as an indicator of fire. Smoke detectors/alarms are usually housed in plastic enclosures, typically shaped like a disk about in diameter and thick, but shape and size vary. Smoke can be ...

temperature sensor Mechanical temperature sensors * Thermometer * Bimetallic strip Electrical temperature sensors * Thermistor- Thermistors are thermally sensitive resistors whose prime function is to exhibit a large, predictable and precise change in electrical res ...

s and

security cameras Closed-circuit television (CCTV), also known as video surveillance, is the use of closed-circuit television cameras to transmit a signal to a specific place on a limited set of monitors. It differs from broadcast television in that the signal ...

that will no longer require a power source.

References

{{reflist, 30em Wi-Fi Internet of things