Estimating beacon proximity/distance based on RSSI - Bluetooth LE

Question

I\'ve got a simple iOS app which displays the proximity of the Bluetooth LE beacons it detects using such expressions as \"immediate\", \"near\" etc. and I need to write som

Answer 1

The txPower mentioned by @davidgyoung is given by the formula:

RSSI = -10 n log d + A

where

• d = distance
• A = txPower
• n = signal propagation constant
• RSSI = dBm

In free space n = 2, but it will vary based on local geometry – for example, a wall will reduce RSSI by ~3dBm and will affect n accordingly.

If you want the highest possible accuracy, it may be worthwhile to experimentally determine these values for your particular system.

Reference: see the paper Evaluation of the Reliability of RSSI for Indoor Localization by Qian Dong and Waltenegus Dargie for a more detailed explanation of the derivation and calibration.