In 2024, the IEEE will unveil a new Wi-Fi standard—802.11bf—with specifications that will turn wireless devices into sensors capable of collecting data about people and objects by calculating how they disturb the signals bouncing around a physical space. Established Wi-Fi devices will become part of networks used to determine the location and interactions of humans and objects within a particular area.
The new standard will mark a significant shift in data transmission as sensors assume an integral role in how the information will be captured, deciphered, and utilized. It will also make Wi-Fi sensing ubiquitous and encourage the creation of innovative connected systems and applications that benefit from highly-integrated sensor technologies.
Underlying CMOS RF technology
The close-range radio frequency (RF) circuitry deployed for sensing in these Wi-Fi networks is built around radar technology. Unlike traditional hardware sensors, RF sensing provides low-cost and unobtrusive services. Due to the broadcast nature of RF signals, RF sensing can be used to monitor multiple subjects and capture changes in the environment over a large area.
RF or radar sensors use a waveform modulation scheme called frequency modulated continuous wave (FMCW). The waveform is optimized to detect objects in space and determine their velocity. That’s how a smart device can detect breathing patterns at close distances.
Using multiple antennas can generate an even more detailed picture of what is happening at close range. That’s because each antenna essentially takes a picture and uses that data to process the movements. A higher number of antennas translates into more capabilities to achieve finer angle resolution. The 3D location and multiple objects detection are a case in point.
Take the example of a smart home radar sensor that can monitor a person’s vital signs and track his or her breathing rates on how well they are sleeping. The device also uses the radar for gesture-based interactions at close range.
Figure 1 The new Wi-Fi sensor network, based on the 802.11bf standard, calls for RF CMOS-based single-chip solutions. Source: Socionext
It’s worth noting that advanced CMOS semiconductor integration offers ultra-low-power operation while enabling smaller circuits comprising millimeter wave (mmWave) RF circuitry along with A/D converters, filters, built-in dedicated engine for digital signal processing, and standard SPI serial I/O. It’s all integrated into a small planar antenna in package (AiP).
Wi-Fi sensing uses cases
Internet of Things (IoT) devices depend on wireless communication using RF technologies such as Bluetooth Low Energy (BLE) and Low Power Wide Area (LPWA). As the demand and usage for connected devices increases, developers seek sensors optimized for energy efficiency with new features and extended battery life. Low power CMOS digital and RF technologies offer such advantages. Additionally, as products become more compact, a system-on-chip (SoC) integrating the entire system—CPU, RF and other components—becomes desirable and practical.
Low-power RF CMOS technology originally developed for home appliances is now applied in a wide range of consumer and automotive applications. Radio waves are used in TV broadcasting, data communication, and sensors for object detection. To accelerate the evolution of these products, an SoC device allows optimal tuning for meeting customers’ different specifications. Its low power consumption also makes it a highly suitable design choice.
Figure 2 A wide range of applications will benefit from this sensor manifestation of the Wi-Fi network. Source: Socionext
Below are some of the use cases that can benefit from an RF CMOS-based SoC:
- Broadcasting: Streaming video directly on TVs, mobile devices, and in-vehicle infotainment systems.
- LPWA networks: Transmission of various sensing data from IoT devices using wireless communications.
- Ka-band satellite communications: Connectivity anytime, anywhere.
- Vehicle-to-everywhere (V2X): Vehicle-to-vehicle and vehicle-to-infrastructure communications for supporting autonomous driving.
- 79 GHz RF radar: Support for advanced driver assistance system (ADAS) applications.
- 24 GHz RF radar: Enables detection of suspicious individuals and approaching objects and automatically triggers an alarm and video recording before an incident occurs.
- 60 GHz RF radar: Multiple antennas such as 2TX and 4RX MIMOs and wide bandwidth FMCW chips can perform various sensing functions like detecting the position of multiple persons within the vehicle. It can also detect vital signs, which helps prevent drivers from accidentally leaving babies, children, or pets alone in a car.
In July 2021, a press release issued by the Federal Communications Commission (FCC) stated that the U.S. Government recognizes the increasing practicality of using mobile radar devices in the 60-GHz band to perform innovative and life-saving functions. Advanced radar technology can also be used for theft prevention and enables a host of smart in-cabin features, including seat occupancy monitoring, infant/pet detection and fatality prevention, driver state monitoring, and touchless precision operation.
Wi-Fi sensor SoC
Socionext has developed an RF-CMOS single-chip solution that encompasses RF core, analog-digital integration, and a small package design. It has integrated compact and low-power RF CMOS circuitry as well as high-precision RF sensor antennas.
Below is an example of an RF CMOS SoC, highlighting details of the integration of various technologies.
Figure 3 The RF sensing applications mandate a highly integrated SoC design. Source: Socionext
Over the years, Socionext has developed analog IPs to meet the low-power and small-size requirements for various applications. That allows the company to integrate multiple analog and digital building blocks into a single chip while optimizing the mobile design for low noise.
Masakazu Urade is manager of connected solution team at Socionext Inc.
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