IEEE 802.11mc

Task Group mc (TGmc) of the IEEE 802.11 Working Group, sometimes referred to as IEEE 802.11mc, was the third maintenance/revision group for the IEEE 802.11 WLAN standards.^[1]^[2] Purpose was to incorporate accumulated maintenance changes (editorial and technical corrections) into IEEE Std 802.11-2012, and roll up approved amendments into the standard.^[3]

The work by TGmc resulted in the publication of IEEE Std 802.11-2016 in 2016.^[2]

TGmc has ceased its operation. Maintenance/revision for IEEE Std 802.11-2016 is being handled by TGmd.^[2]

Amendments rolled-In

Following amendments were incorporated by TGmc on top of IEEE Std 802.11-2012:

IEEE Std 802.11ae-2012
IEEE Std 802.11aa-2012
IEEE Std 802.11ad-2012
IEEE Std 802.11ac-2013
IEEE Std 802.11af-2013

Wi-Fi Round Trip Time

While it is not the main purpose of the maintenance/revision group, some features deemed not big enough to require a full Task Group within the IEEE 802.11 WG are sometimes added to the IEEE 802.11 standard via the maintenance/revision group.

The main feature added through TGmc is commonly known as Wi-Fi Round Trip Time (Wi-Fi RTT). It allows computing devices to measure the distance to nearby Wi-Fi access points (APs) and determine their indoor location with a precision of 1–2 metres using round-trip delay.^[4] The accuracy is better than estimations with trilateration based on received signal strength indication (RSSI).

Concept

With a single Wi-Fi access point, only a distance measurement is available. With three or more nearby APs, an app can trilaterate a device's location with an accuracy of one to two meters.

The technology operation principle is based on time delay in signal reception and transmission - the time necessary for sending a signal and the time required for receiving its confirmation have to be taken into account. The system calculates this time span and then multiplies it by the speed of light.^[4]

Not all devices have the necessary hardware support yet for this feature. At present the list of the certified routers contains only the following models:^[4]

Google Wi-Fi.
Compulab Wi-Fi Indoor Location Device.
Google Nest Wi-Fi (Point or Router).

Application

With accurate indoor position awareness, apps can perform advanced automation based on where a device is in a building. For example, a smartphone user can have lights turn on when they enter a particular room by simply making voice commands since the device is location-aware (e.g. "turn on the lights in this room").

The technology makes it possible to create location-based applications and detailed services that let users orient easily inside buildings. In comparison with BLE, the function ensures higher accuracy in defining location and accelerates production processes.^[5]

Navigine tested the performance of the Wi-Fi RTT technology and made the conclusion that, subject to the specified requirements, the obtained result exceeds the declared values. Thus, within 95% of the time, the positioning accuracy in the check point is less than 1 m and within 50% of the time, the accuracy figures are kept within the limits of 30 cm. The delay in locating doesn’t exceed 1 sec. Such time frames can be achieved by using the function of calculating pedestrian coordinates (PDR) within the particle filter.^[5]

Android Pie

Wi-Fi Round-Trip-Time in Android Pie does not require that the phone connect to any Wi-Fi access points. Only the phone is used to determine distance, not the APs^{[citation needed]}. This feature is also tied into the Android operating system's existing location system to preserve the user's privacy. Apps using round-trip delay time (RTT) need the location permission, and the device must have location-based services enabled at the system level.

Many smartphone models with the Android 9 or later operating system can calculate the distance to access points. The following devices support Wi-Fi RTT technology: Xiaomi, LG Corporation, Samsung, Google Pixel, Poco X2, Sharp Aquos.^[4]

References

^ "IEEE 802.11, The Working Group Setting the Standards for Wireless LANs". Ieee802.org.
^ ^a ^b ^c "IEEE P802 - Task Group M Status". Ieee802.org.
^ "IEEE P802.11 Wireless LANs" (DOC). IEEE. Retrieved 28 February 2019.
^ ^a ^b ^c ^d "Wi-Fi location: ranging with RTT, Google Developers".
^ ^a ^b "A needle in a haystack: how Wi-Fi RTT takes Indoor Positioning to the next level, Navigine".

External links

[1] "IEEE 802.11, The Working Group Setting the Standards for Wireless LANs". Ieee802.org.

[auto-2] "IEEE P802 - Task Group M Status". Ieee802.org.

[3] "IEEE P802.11 Wireless LANs" (DOC). IEEE. Retrieved 28 February 2019.

[auto1-4] "Wi-Fi location: ranging with RTT, Google Developers".

[auto2-5] "A needle in a haystack: how Wi-Fi RTT takes Indoor Positioning to the next level, Navigine".

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