There’s a handful of terms that will help you better understand how beacons work. Most of them describe signal characteristics and the way beacons communicate with mobile devices:
- Broadcasting Power
- Advertising Interval
- Measured Power
- Proximity zones
Broadcasting Power and Beacon’s Range
Broadcasting Power (or Transmit Power) is the power with which the beacon broadcasts its signal. In Estimote Beacons, you can change it with the Estimote SDK, the Cloud interface, or the app.
The value ranges from -40 dBm to +4 dBm.
Note that there are some exceptions:
- Proximity Beacons ordered before mid-2016 (hardware revision "D") have the minimum value of -30 dBm.
- Location Beacons (hardware revision "F") support the minimum value of -30 dBm.
- Location Beacons with long range (hardware revision "F3.3") have the maximum option of +10 dBm.
Broadcasting Power directly impacts signal range. The more power, the longer the range. Increasing the power can also make the signal more stable, but keep in mind it can have a negative effect on battery life.
The beacon’s range is technically up to 70 m (+ 4dBM). In real-world conditions, however, you should expect up to 40-50 m.
The long-range Location Beacons' signal travels for up to 200 m.
Estimote Stickers have a range of up to 15 m.
Beacons do not broadcast constantly. They ‘blink’ instead. Advertising Interval describes the time between each blink. Just as with Broadcasting Power, Advertising Interval on beacons can be adjusted with Estimote SDK, Cloud, and the app.
The value ranges between 100 ms and 2000 ms. The shorter the interval, the more stable the signal. Keep in mind that adjusting Advertising Interval will impact battery life in a big way.
In the case of Estimote Stickers, the interval is adjusted automatically, depending on the sticker’s state. You can read about it in detail on our Developer Portal.
RSSI stands for Received Signal Strength Indicator. It is the strength of the beacon's signal as seen on the receiving device, e.g. a smartphone. The signal strength depends on distance and Broadcasting Power value. At maximum Broadcasting Power (+4 dBm) the RSSI ranges from -26 (a few inches) to -100 (40-50 m distance).
RSSI is used to approximate the distance between the device and the beacon using another value defined by the iBeacon standard: Measured Power (see below).
Due to external factors influencing radio waves—such as absorption, interference, or diffraction—RSSI tends to fluctuate. The further away the device is from the beacon, the more unstable RSSI becomes.
Read How precise are Estimote Beacons? for more information.
Measured Power is a factory-calibrated, read-only constant which indicates what's the expected RSSI at a distance of 1 meter to the beacon. Combined with RSSI, it allows you to estimate the distance between the device and the beacon.
iBeacon defines four proximity zones for estimating the distance to a beacon. Keep in mind, these are approximations.
- immediate (very close to the beacon)
- near (about 1-3 m from the beacon)
- far (further away or the signal is fluctuating too much to make a better estimate)