When a boat moves through the water, it creates waves, which, if analyzed, can provide an indication of its size, speed, and direction. A new Wi-Fi technology seeks to do something similar. Wi-Fi Sensing leverages existing Wi-Fi signals to sense motion, which can then be used to enable many new applications.
Additionally, sensing enables Wi-Fi networks to become more interactive. Envisioned applications include motion detection, gesture recognition, security, smart homes, and more.
How Wi-Fi Sensing works
Wi-Fi Sensing technology uses Wi-Fi signals to sense activities and interpret movement. How? The Wi-Fi standard provides a set of back-and-forth signaling protocols to set up Wi-Fi stations. The technology applies artificial intelligence to make sense of Wi-Fi signals. Specifically, AI is applied to channel state information (CSI), which has information about the communication link. That information describes how a signal propagates from the transmitter to the receiver and incorporates the effect of scattering, fading, and power decay over distance.
While the CSI was designed primarily for data communication, it captures a lot of information about the operating environment. Every time a data packet is sent over the air via Wi-Fi, the Wi-Fi devices compute the CSI of the wireless channel to overcome interference from the environment to decode the data packet properly. In recent years this information has been used to overcome the interference due to the movement of objects.
Wi-Fi Sensing technology can sense the disruption of the signal and use the information to determine the size, speed, and location of the disruption. Some sensing capabilities include basic motion detection, motion localization, presence detection, speed/velocity measurement, breathing detection, sleep monitoring, and daily activity monitoring.
Guidelines to get started
Earlier this month, the Wireless Broadband Alliance, a global organization founded on the vision of driving interoperable service experiences via Wi-Fi, issued residential Wi-Fi Sensing deployment guidelines.
"Wi-Fi Sensing lays the foundation for Wi-Fi service providers to expand into a wide variety of exciting new markets, including health care, home security, building automation, and more," said Tiago Rodrigues, CEO of the Wireless Broadband Alliance.
While aimed at the home environment, the techniques and methodologies could also be applied to commercial and industrial settings. The guidelines cover key topics such as:
- Technological benefits, relevant communication guidelines, and constraints
- Environmental and device factors that can impact sensing, such as how different types of construction materials affect signal strength and propagation in each Wi-Fi band
- Experiments that provide insights into factors such as access point locations, interference, floor plans, and more
- General deployment guidelines including access point placement, network topology, floorplan considerations, and sensitivity settings.
An emerging technology
Many see sensing as the next major enhancement to Wi-Fi. The alliance is hoping to address some of the common issues that crop up whenever a new technology area emerges.
"We hope our work serves as an initial starting point for more stakeholders to get involved in shaping this future as the community continues working toward enhancing sensing applications and capabilities," said Dr. Taj Manku, Co-founder and CEO at Cognitive Systems, an alliance member.
He noted that discussions and testing conducted through the WBA Wi-Fi Sensing group helped drive awareness of the technology and improved the technology itself.
As part of the alliance's work in Wi-Fi Sensing, it sought to spell out what the technology is, classified its use cases and requirements, and identified the gaps in Wi-Fi standards that would lead to the enhancement of the technology and ease of deployment if those gaps are addressed.
It also created a white paper on test methodologies and performance metrics. Through the paper, the group laid out a detailed set of KPI metrics that can be used to evaluate the performance of a Wi-Fi Sensing-based home monitoring system. It also included a number of test cases and scenarios to measure the defined KPIs.
Some Wi-Fi Sensing applications are ready to go
The alliance noted that there are some gaps in current Wi-Fi standards for some use cases. However, home monitoring is one application that can be implemented using current standards and existing Wi-Fi hardware with minimal changes.
Using Wi-Fi Sensing for this application has the benefit of not requiring cameras or passive-infra-red (PIR) sensors (as is the case now) but instead leverages communications with standard Wi-Fi devices already in a home. In addition, the alliance claims home monitoring solutions using Wi-Fi Sensing provides better coverage than current systems using fewer devices.
Such a system could be based on a single access point (AP). Motion is detected by measuring Channel CSI from transmissions between different Wi-Fi devices. The current state of the Wi-Fi standards favors having the agent located on the AP. In the future, home monitoring may be further extended by having the sensing agent on a device rather than an AP.