WiFi Sensing

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WiFi sensing (also referred to as WLAN sensing [1] ) uses existing Wi-Fi signals to detect events or changes such as motion, gesture recognition, and biometric measurement (e.g. breathing). [2] [3] WiFi sensing is a combination of Wi-Fi and radar sensing technology working in tandem to enable usage of the same Wi-Fi transceiver hardware and RF spectrum for both communication and sensing.

Contents

The applications of WiFi sensing are broad. Wi-Fi may operate in multiple frequency bands, each providing a unique range of possible use cases dependent on the physical electro-magnetic propagation properties, approved power levels, and allocated bandwidth. There are three major applications: detection (binary classification), recognition (multi-class classification), and estimation (quantity values of size, length, angle, distance, etc.). [4]

Combining communication and sensing within mobile networking technology is a large area of exploration. It is sometimes referred to as joint communications and radar/radio sensing (JCAS). [5] Combining the two technologies can leverage existing hardware and infrastructure, enable new services, and provide a higher level of interaction with networked devices (e.g. IoT and automation).  

Technical

In comparison with radar technology, such as frequency-modulated continuous-wave radar, WiFi sensing may use its physical layer (PHY) for both environment measurements as well as digital communication. Wi-Fi benefits from having a well-defined medium access control (MAC) layer entity specified in the 802.11 standard. Having a MAC layer present in a radar system makes coordination and sharing of air-time resource usage between multiple devices possible. Additionally, it allows for the exchange of information between multiple devices. [4]

WiFi sensing systems require more complex algorithms compared to traditional radar systems. With traditional radar systems, the PHY layer components produce waveforms designed so minimal processing is required to extract the desired physical measurements from the sensor. For example, in an FMCW system designed to sense target range, the PHY layer components output a signal with a frequency proportional to the reflection echo from a target. By employing a fast Fourier-transform algorithm on the output, all the targets visible by the sensor may be extracted, and simple linear mapping of frequency to target range can be performed. [6] [7]

With WiFi sensing, the PHY layer components and signals have been designed for communications. Sensing must make use of the signals transmitted by digital communication systems, which are typically orthogonal frequency-division multiplexing (OFDM) based.

History

The initial building blocks required for WiFi sensing were incorporated into the first OFDM Wi-Fi standard titled 802.11a, published in 1999. While not originally intended for sensing, the 802.11a PHY layer defined waveform components to be added to the transmission preamble. The receiver could then estimate the channel to perform equalization and other DSP techniques to improve the performance of the remaining data reception. These waveform components are referred to as the long training symbols. [8]

September 29, 2020 the IEEE Standards Association approved project IEEE 802.11bf for WLAN sensing. Its purpose was to establish standards for the interoperability of wireless devices and enable a wide range of WiFi sensing applications. [9]

Academic

Much of the early academic research on WiFi sensing was based on large software-defined-radio (SDR) hardware, [10] such as the Ettus Research USRP. SDR provided flexibility to perform custom operations which were previously impossible due to the close natured implementations of off-the-shelf Wi-Fi hardware. The requirement of a high-end SDR made it difficult for it to be commercialized as a product. Later efforts from the research community led to tools for extracting channel state information (CSI) measurements from commodity 802.11n NICs. [4]

In October 2019, The Wireless Broadband Alliance (WBA) published the first industry whitepaper on WiFi sensing. Led by Cognitive Systems Corp., Intel, and Centre for Development of Telematics (C-DOT), the paper was the result of a year-long collaboration between Wi-Fi technology developers and service providers. An analysis of the existing Wi-Fi standards identified gaps, opening areas for new potential enhancements. The paper explores early WiFi sensing applications, including motion detection, gesture recognition, and biometric measurement. Potential business opportunities within the home security, health care, enterprise, and building automation/management markets were also identified. [2]

Commercialization

In 2015, the first fully-integrated SDR on a single chip, known as the R10 (Radio10), was introduced by Cognitive Systems Corp. Its initial purpose was spectrum monitoring for cellular, Wi-Fi, and other land mobile radio (LMR) services using a radio-frequency (RF) camera system to observe RF signals and their parameters from a pre-defined field of view. The chip had five custom CPU cores, four wireless receivers, and highly configurable dual multi-vector processors, giving the R10 chip significant capabilities in detecting and processing wireless signals in real-time. Once in production, Cognitive Systems Corp. focused on using the R10 to monitor the most prevalent spectrum, Wi-Fi signals, for motion detection. To further develop the signal processing algorithms, a major subset of the Wi-Fi MAC/PHY stack was implemented on the R10. [11]

The first consumer product using WiFi sensing technology was Aura WiFi Motion, which utilized the R10 chip. This commercial product was distributed by Cognitive Systems Corp. through Amazon from December 2017 to January 2019. [12] In October 2019, Cognitive Systems Corp. began licensing its software stack as WiFi Motion to service providers. At the 2020 Consumer Electronics Show (CES), Plume Design, Inc. announced Motion Aware powered by WiFi Motion, a new addition to its intelligent services platform for modern smart homes. [13] Motion Aware was first commercially available on February 29, 2020, with the release of Plume Design, Inc.'s second-generation SuperPods and HomePass subscriber services

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IEEE 802.15 is a working group of the Institute of Electrical and Electronics Engineers (IEEE) IEEE 802 standards committee which specifies Wireless Specialty Networks (WSN) standards. The working group was formerly known as Working Group for Wireless Personal Area Networks.

<span class="mw-page-title-main">IEEE 802.11</span> Wireless network standard

IEEE 802.11 is part of the IEEE 802 set of local area network (LAN) technical standards, and specifies the set of medium access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) computer communication. The standard and amendments provide the basis for wireless network products using the Wi-Fi brand and are the world's most widely used wireless computer networking standards. IEEE 802.11 is used in most home and office networks to allow laptops, printers, smartphones, and other devices to communicate with each other and access the Internet without connecting wires. IEEE 802.11 is also a basis for vehicle-based communication networks with IEEE 802.11p.

<span class="mw-page-title-main">Wireless LAN</span> Computer network that links devices using wireless communication within a limited area

A wireless LAN (WLAN) is a wireless computer network that links two or more devices using wireless communication to form a local area network (LAN) within a limited area such as a home, school, computer laboratory, campus, or office building. This gives users the ability to move around within the area and remain connected to the network. Through a gateway, a WLAN can also provide a connection to the wider Internet.

<span class="mw-page-title-main">Wireless network</span> Computer network not fully connected by cables

A wireless network is a computer network that uses wireless data connections between network nodes. Wireless networking allows homes, telecommunications networks and business installations to avoid the costly process of introducing cables into a building, or as a connection between various equipment locations. Admin telecommunications networks are generally implemented and administered using radio communication. This implementation takes place at the physical level (layer) of the OSI model network structure.

<span class="mw-page-title-main">Wi-Fi</span> Wireless local area network

Wi-Fi is a family of wireless network protocols based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio waves. These are the most widely used computer networks, used globally in home and small office networks to link devices and to provide Internet access with wireless routers and wireless access points in public places such as coffee shops, hotels, libraries, and airports to provide visitors.

IEEE 802.11n-2009, or 802.11n, is a wireless-networking standard that uses multiple antennas to increase data rates. The Wi-Fi Alliance has also retroactively labelled the technology for the standard as Wi-Fi 4. It standardized support for multiple-input multiple-output, frame aggregation, and security improvements, among other features, and can be used in the 2.4 GHz or 5 GHz frequency bands.

IEEE 802.11y-2008 is an amendment to the IEEE 802.11-2007 standard that enables data transfer equipment to operate using the 802.11a protocol on a co-primary basis in the 3650 to 3700 MHz band except when near a grandfathered satellite earth station. IEEE 802.11y is only being allowed as a licensed band. It was approved for publication by the IEEE on September 26, 2008.

IEEE 802.11  – or more correctly IEEE 802.11-1997 or IEEE 802.11-1999 – refer to the original version of the IEEE 802.11 wireless networking standard released in 1997 and clarified in 1999. Most of the protocols described by this early version are rarely used today.

IEEE 802.11a-1999 or 802.11a was an amendment to the IEEE 802.11 wireless local network specifications that defined requirements for an orthogonal frequency-division multiplexing (OFDM) communication system. It was originally designed to support wireless communication in the unlicensed national information infrastructure (U-NII) bands as regulated in the United States by the Code of Federal Regulations, Title 47, Section 15.407.

IEEE 802.11b-1999 or 802.11b is an amendment to the IEEE 802.11 wireless networking specification that extends throughout up to 11 Mbit/s using the same 2.4 GHz band. A related amendment was incorporated into the IEEE 802.11-2007 standard.

IEEE 802.11g-2003 or 802.11g is an amendment to the IEEE 802.11 specification that operates in the 2.4 GHz microwave band. The standard has extended link rate to up to 54 Mbit/s using the same 20 MHz bandwidth as 802.11b uses to achieve 11 Mbit/s. This specification under the marketing name of Wi-Fi has been implemented all over the world. The 802.11g protocol is now Clause 19 of the published IEEE 802.11-2007 standard, and Clause 19 of the published IEEE 802.11-2012 standard.

WiGig, alternatively known as 60 GHz Wi-Fi, refers to a set of 60 GHz wireless network protocols. It includes the current IEEE 802.11ad standard and also the IEEE 802.11ay standard.

IEEE 802.11ac-2013 or 802.11ac is a wireless networking standard in the IEEE 802.11 set of protocols, providing high-throughput wireless local area networks (WLANs) on the 5 GHz band. The standard has been retroactively labelled as Wi-Fi 5 by Wi-Fi Alliance.

IEEE 802.11k-2008 is an amendment to IEEE 802.11-2007 standard for radio resource measurement. It defines and exposes radio and network information to facilitate the management and maintenance of a mobile Wireless LAN. IEEE 802.11k was incorporated in IEEE Std 802.11-2012; see IEEE 802.11.

IEEE 802.11ad is an amendment to the IEEE 802.11 wireless networking standard, developed to provide a Multiple Gigabit Wireless System (MGWS) standard at 60 GHz frequency, and is a networking standard for WiGig networks. Because it uses the V band of millimeter wave (mmW) frequency, the range of IEEE 802.11ad communication would be rather limited compared to other conventional Wi-Fi systems. However, the high frequency allows it to use more bandwidth which in turn enables the transmission of data at high data rates up to multiple gigabits per second, enabling usage scenarios like transmission of uncompressed UHD video over the wireless network.

IEEE 802.11ah is a wireless networking protocol published in 2017 called Wi-Fi HaLow as an amendment of the IEEE 802.11-2007 wireless networking standard. It uses 900 MHz license-exempt bands to provide extended-range Wi-Fi networks, compared to conventional Wi-Fi networks operating in the 2.4 GHz and 5 GHz bands. It also benefits from lower energy consumption, allowing the creation of large groups of stations or sensors that cooperate to share signals, supporting the concept of the Internet of things (IoT). The protocol's low power consumption competes with Bluetooth, LoRa, and Zigbee, and has the added benefit of higher data rates and wider coverage range.

IEEE 802.11af, also referred to as White-Fi and Super Wi-Fi, is a wireless computer networking standard in the 802.11 family, that allows wireless local area network (WLAN) operation in TV white space spectrum in the VHF and UHF bands between 54 and 790 MHz. The standard was approved in February 2014. Cognitive radio technology is used to transmit on unused portions of TV channel band allocations, with the standard taking measures to limit interference for primary users, such as analog TV, digital TV, and wireless microphones.

Wi-Fi 6, or IEEE 802.11ax, is the latest IEEE standard from the Wi-Fi Alliance, for wireless networks (WLANs). It operates in the 2.4 GHz and 5 GHz bands, with an extended version, Wi-Fi 6E, that adds the 6 GHz band. It is an upgrade from Wi-Fi 5 (802.11ac), with improvements for better performance in crowded places. Wi-Fi 6 covers frequencies in license-exempt bands between 1 and 7.125 GHz, including the commonly used 2.4 GHz and 5 GHz, as well as the broader 6 GHz band.

IEEE 802.11ay, Enhanced Throughput for Operation in License-exempt Bands above 45 GHz, is a follow-up to IEEE 802.11ad WiGig standard which quadruples the bandwidth and adds MIMO up to 8 streams. Development started in 2015 and the final standard IEEE 802.11ay-2021 was approved in March 2021.

RF CMOS is a metal–oxide–semiconductor (MOS) integrated circuit (IC) technology that integrates radio-frequency (RF), analog and digital electronics on a mixed-signal CMOS RF circuit chip. It is widely used in modern wireless telecommunications, such as cellular networks, Bluetooth, Wi-Fi, GPS receivers, broadcasting, vehicular communication systems, and the radio transceivers in all modern mobile phones and wireless networking devices. RF CMOS technology was pioneered by Pakistani engineer Asad Ali Abidi at UCLA during the late 1980s to early 1990s, and helped bring about the wireless revolution with the introduction of digital signal processing in wireless communications. The development and design of RF CMOS devices was enabled by van der Ziel's FET RF noise model, which was published in the early 1960s and remained largely forgotten until the 1990s.

References

  1. ↑ IEEE Standard for Telecommunications and Information Exchange Between Systems - LAN/MAN Specific Requirements - Part 11: Wireless Medium Access Control (MAC) and physical layer (PHY) specifications: High Speed Physical Layer in the 5 GHZ band. doi:10.1109/IEEESTD.1999.90606. ISBN   978-0-7381-1810-9.
  2. 1 2 "Wi-Fi Sensing". Wireless Broadband Alliance. Archived from the original on 2021-04-04. Retrieved 2021-03-03.
  3. ↑ Wi-Fi Sensing: Revolutionizing Motion Sensing with Wi-Fi technology. Semiconductor Components Industries LLC. July 2020.
  4. 1 2 3 Halperin, Daniel; Hu, Wenjun; Sheth, Anmol; Wetherall, David (2011). "Tool release". ACM SIGCOMM Computer Communication Review. 41: 53. doi:10.1145/1925861.1925870. S2CID   13561174.
  5. ↑ Andrew Zhang, J.; Md Lushanur Rahman; Wu, Kai; Huang, Xiaojing; Jay Guo, Y.; Chen, Shanzhi; Yuan, Jinhong (2020). "Enabling Joint Communication and Radar Sensing in Mobile Networks -- A Survey". arXiv: 2006.07559 [eess.SP].
  6. ↑ Beg, C.; Vajedi, M.; Nezhad-Ahmadi, M. R.; Azad, N. L.; Safavi-Naeini, S. (September 2012). "A cost-effective radar system for automotive powertrain control applications". 2012 15th International IEEE Conference on Intelligent Transportation Systems. pp. 84–89. doi:10.1109/ITSC.2012.6338893. ISBN   978-1-4673-3063-3. S2CID   9172584. Archived from the original on 2021-09-29. Retrieved 2021-03-03.
  7. ↑ Chang, W.; Huan, L.; Yubai, L. (June 2006). "A Practical FMCW Radar Signal Processing Method and Its System Implementation". 2006 6th International Conference on ITS Telecommunications. pp. 1195–1199. doi:10.1109/ITST.2006.288840. ISBN   0-7803-9586-7. S2CID   24028520. Archived from the original on 2021-09-29. Retrieved 2021-03-03.
  8. ↑ "IEEE Standard for Telecommunications and Information Exchange Between Systems - LAN/MAN Specific Requirements - Part 11: Wireless Medium Access Control (MAC) and physical layer (PHY) specifications: High Speed Physical Layer in the 5 GHZ band". IEEE STD 802.11a-1999: 1–102. December 1999. doi:10.1109/IEEESTD.1999.90606. ISBN   978-0-7381-1810-9. Archived from the original on 2020-11-29. Retrieved 2021-03-03.
  9. ↑ says, Rakesh Kumar (2020-12-05). "IEEE 802.11bf Aims to Enable a New Application of WLAN Technology: WLAN Sensing". IEEE SA Beyond Standards. Archived from the original on 2021-03-31. Retrieved 2021-03-03.
  10. ↑ Adib, Fadel; Katabi, Dina (2013-08-27). "See through walls with WiFi!". Proceedings of the ACM SIGCOMM 2013 conference on SIGCOMM. SIGCOMM '13. Hong Kong, China: Association for Computing Machinery. pp. 75–86. doi: 10.1145/2486001.2486039 . ISBN   978-1-4503-2056-6.
  11. ↑ Manku, T.; Kravets, O.; Selvakumar, A.; Beg, C.; Chattha, K.; Dattani, D.; Devison, S.; Ituah, S.; Magnusen, T.; Mathai, N.; McGinn, J. (June 2017). "A 680MHz to 4GHz 4RX-1TX SoC for cognitive radio applications". 2017 IEEE MTT-S International Microwave Symposium (IMS). pp. 586–589. doi:10.1109/MWSYM.2017.8058634. ISBN   978-1-5090-6360-4. S2CID   25695557. Archived from the original on 2021-09-29. Retrieved 2021-03-03.
  12. ↑ "Next Generation of Aura Uses WiFi Motion and Mesh Technology to Monitor Your Home Without Cameras". www.businesswire.com. 2017-11-14. Archived from the original on 2021-09-29. Retrieved 2021-03-03.
  13. ↑ "CES Roundup: Plume's motion detection for the home, Wi-Fi 6 laptops, & more Wi-Fi 6 mesh". Wi-Fi NOW Global. 2020-01-13. Archived from the original on 2020-11-28. Retrieved 2021-03-03.
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