Others

CE - Accurate Indoor Location for the IoT (Jan 19)

802.11b - Received Signal Strength Indication (RSSI)

Due to multipath fading, the RSSI fall-off from the antenna does not follow a uniform inverse square law and is distorted by the building materials that it travels through.
Large errors of 10 to 20 meters

Bluetooth low energy beacons
Low Power Wide Area Network (LPWAN)
LoRa Network Protocol (Long Range)

https://www.postscapes.com/long-range-wireless-iot-protocol-lora

P2PLoc for Group-Motion Applications

P2PLoc (peer-to-peer localization) envisions wearable IoT devices on users' arms or wrists that exchange wireless messages to ultimately compute the relative positions of each group member. The outcome is a topology or configuration of mo- bile users that can be tracked in real time.

Using the time wireless signals take to travel between two devices as a measure of the distance between them. The precision of this time measurement directly correlates with the bandwidth of the wireless signal used. Therefore, we use ultra-wideband (UWB) radios with a 1 GHz bandwidth. When used with a packet-handshake protocol called two-way ranging (TWR), today's UWB platforms can estimate the distance between two devices with about 10 cm precision without clock synchronization.

P2PLoc: Peer-to-Peer Localization of Fast-Moving Entities - Computing Edge, Feb 2019