Happened to read about a good article that explains the beacons and ranging etc. Below given few understanding from it
We have to consider a beacon at the centre of a sphere and radio signals being the sphere, with this imagination below concepts are applicable.
RSSI (Received Signal Strength Indicator)
This is a generic measure of power present in the received signal. The signal strength depends on first and foremost the TxPower. When the TxPower is set to maximum (+4) the RSSI ranges from -26 (few inches) to -100(40-50m distance)
Signal Direction
Beacons emit signals in every direction at once, much like the sphere.
Range
The signals range could be reduced down to few inches or increased to cover areas as wide as 230ft (70mts) Various forms of interference can negatively impact range, in addition wider ranges consume more power.
Battery Strength and Signal Degradation
Normally battery levels should not have a direct impact on the signal strength unless the battery is critically low.
Determining the position of a mobile device
It is possible to get the information about the distance between beacon and a mobile device. The term in known as “distance” and is measured in meters.
Reported Distance between a Mobile Device and a single Beacon.
When ranging a beacon, the measured distance between the beacon and the device can vary and can fluctuate heavily. This is because of the 2.4GHz radio wave spectrum is highly susceptible to external factors, like multi path propagation, diffraction, absorption and interference.
Looks like estimate team has already done some tests around this and the values are like below
Distance of 20cm : deviation is 5-6 cm
Distance of 1 m : deviation is 15cm
Distance greater than 10 m: deviation is 2-3 meters
The fluctuations will be more visible in Android platform and less in iOS because iOS already has noise reduction techniques implemented in to the CoreLocation framework. Android bluetooth stack on the other hand doesn’t have this yet.
Zones:
There are 3 static Zone surrounding each beacon.
Immediate Zone (0-20cm)
- When device is held up close to beacon
- Accuracy confidence is high
Near Zone (20cm - 2m)
- Within a couple of meters to the beacon
- Accuracy is fairly certain
Far Zone (2-70m)
- More than a few meters away
- Accuracy is low or the signal strength is weak
Zones are not adjustable, they are preset boundaries that fit within the confines of the radio signals reach. As an example, if the range is reduced to 10m, all three zones remain available, if the range is reduced to 1.5 m, only two zones available.
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