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:
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
External links
