Beacon is BLE(Bluetooth low energy) device which is frequently used in Assets Tracking, Marketing (Sending Push Notification with message and Url), Body Fitness tracking, Door Tracking, etc.
When an old person or sick people enter into other room or cross the exit door then beacon signal will be captured by gateway device which is mounted in each room or exit door. Gateway after scanning beacon, it will raise alarm and notify Admin person.
Here Gateway will scan the RSSI value and transmitted power of beacon and calculate distance b/w gateway and beacon.
Each Beacon Device emits RSSI (Received Signal Strength Indicator) value which is measured by another device antenna. Higher the RSSI value indicates a higher strength of the signal.
As beacon is low energy device so RSSI value is mostly in Negative number. The RSSI value is always expressed in dBm (decibels per milliwatt).
There are 2 important Parameters for Distance calculation b/w BLE and Device.
RSSI stands for Received Signal Strength Indicator which strength of beacon signal received by Smartphone or receiving the device.
The RSSI value is used to calculate approximate distance b/w BLE and Device. Some time distance is not accurate due to external factor like Low Battery power level of BLE, obstacle b/w Ble and device or diffraction.
Some RSSI value consideration for signal strength.
RSSI Value | Quality Level |
-30dbm | Very Good Signal |
-65 dBm | Good Signal |
-70 dBm | Average Signal |
-80 dBm or less than -80 | Poor Signal |
This is an important parameter for calculating accurate distance b/w BLE and device. Tx Power is expected signal level when measured from a one-meter distance.
Tx power is always measured in decibels per milliwatt (dBm)
<code>function distanceCalculation(rssiValue) {
var txPowerValue = -62 // Normal ranges between -59 to -65
if ( rssiValue == 0) {
return -1.0;
}
var ratio = rssiValue*1.0/txPowerValue;
if (ratio < 1.0) {
return Math.pow(ratio,10);
}
else {
var distance = (0.89976)*Math.pow(ratio,7.7095) + 0.111;
return distance;
}
}</code>
Let try some examples
i)let say txPowerValue = -65;
rssiValue = -60
Then Distance = 0.44 Meter
ii)let say txPowerValue = -59
rssiValue = -65
Then Distance = 2.0 Meter
To know more about measuring distance between beacons & Device and how it can help your business let’s schedule a demo!
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