Bluetooth is one of the 2 default secondary wireless protocol supported by all Private Cyberspaces. Bluetooth is used in situations where WiFi is not practical or feasible.

Wireless technology Link distance Power consumption Connection speed
WiFi medium high high
Bluetooth low medium medium
LoRa high low low

1. Bluetooth Versions

Minimum supported version is Bluetooth 4.0 from 2010, also known as Bluetooth LE (Bluetooth Low Energy).

Bluetooth 4.0 - Bluetooth Low Energy
Bluetooth 4.1 - direct IoT connection
Bluetooth 4.2 - direct IPv6 connection
Bluetooth 5.0 - higher speed longer range
Bluetooth 5.1 - direction finding
Bluetooth 5.2 - improved audio
Bluetooth 5.3 - better signal quality and security

Bluetooth Positioning

1. Bluetooth Timing

Setting of Bluetooth Advertising Interval, Scan Interval and Scan Window is important, as they must overlap for discovery to happen (those tall dotted boxes shown in diagram below).

Source: Microchip

Note Bluetooth 4.0 onwards has 40 channels, all needs to be scanned.

2. Direction Finding

Bluetooth 5.1 direction finding is very nice, by attaching Constant Tone Extension (CTE) data sequence behind the CRC in a Bluetooth packet in order to get Angle of Departure (AoD) or Angle of Arrival (AoA) with multiple antennas at either transmitter or receiver.

That would be great for our indoor positioning, unfortunately it is not readily available yet, so we will be using the Received Signal Strength Indication (RSSI) and triangulation from multiple fixed Bluetooth sources instead.