问使用RSSI计算近似距离

EN

double rssiToDistance(int RSSI, int txPower) {
   /* 
    * RSSI in dBm
    * txPower is a transmitter parameter that calculated according to its physic layer and antenna in dBm
    * Return value in meter
    *
    * You should calculate "PL0" in calibration stage:
    * PL0 = txPower - RSSI; // When distance is distance0 (distance0 = 1m or more)
    * 
    * SO, RSSI will be calculated by below formula:
    * RSSI = txPower - PL0 - 10 * n * log(distance/distance0) - G(t)
    * G(t) ~= 0 //This parameter is the main challenge in achiving to more accuracy.
    * n = 2 (Path Loss Exponent, in the free space is 2)
    * distance0 = 1 (m)
    * distance = 10 ^ ((txPower - RSSI - PL0 ) / (10 * n))
    *
    * Read more details:
    *   https://en.wikipedia.org/wiki/Log-distance_path_loss_model
    */
   return pow(10, ((double) (txPower - RSSI - PL0)) / (10 * 2));
}