Package com.irurueta.navigation.indoor

Class AltBeaconUtils

java.lang.Object
com.irurueta.navigation.indoor.AltBeaconUtils
public class AltBeaconUtils extends Object
Utility class to handle Android's AltBeacon library coefficients used te determine distance for calibrated devices. AltBeacon uses the following formula to estimate Beacon's distance: d = coefficient1 * ratio^coefficient2 + coefficient3

Considered that radio signal propagation follows equation: Pr = Pt * k / d^n, where: - Pr is received signal strength (expressed in mW), - Pt is transmitted signal strength (expressed in mW), - k is equal to k = c / (4 * pi * f), where: - c is speed of light (which is approximately 9*10^8 m/s) - f is the radio link frequency used by the beacon.

Hence, considering: ratio = Pr / Pt

which is equal to: ratio = k / d^n

And isolating d, whe obtain that: d^n = k / ratio

d = (k / ratio)^(1/n) d = k^(1/n)*ratio^(-1/n)

And thus we can see from this last expression that: coefficient1 = k^(1/n) = (c / (4 * pi * f))^(1/n) coefficient2 = -1/n, where n is the path loss exponent and depends on the environment where the device is used (typically on free space n is equal to 2.0, but can usually range from 1.6 to 1.8 on indoor environments) coefficient3 is a bias term calibrated for each device.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final double
    SPEED_OF_LIGHT
    Speed of light expressed in meters per second (m/s).

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    private
    AltBeaconUtils()
    Constructor to prevent instantiation of utility class.

  • Method Summary

    Modifier and Type
    Method
    Description
    static double
    getCoefficient1(double k, double pathLossExponent)
    Gets AltBeacon's 1st coefficient.
    static double
    getCoefficient1WithFrequency(double frequency, double pathLossExponent)
    Gets AltBeacon's 1st coefficient.
    static double
    getCoefficient2(double pathLossExponent)
    Gets AltBeacon's 2nd coefficient.
    static double
    getDistance(double coefficient1, double coefficient2, double coefficient3, double ratio)
    Gets distance using AltBeacon's coefficients.
    static double
    getDistance(double coefficient1, double coefficient2, double coefficient3, double receivedPower, double transmittedPower)
    Gets distance using AltBeacon's coefficients.
    static double
    getFrequency(double k)
    Gets frequency from k value.
    static double
    getFrequency(double coefficient1, double coefficient2)
    Gets frequency using AltBeacon's coefficients.
    static double
    getK(double frequency)
    Gets k value using provided frequency.
    static double
    getK(double coefficient1, double coefficient2)
    Gets k value using AltBeacon's coefficients.
    static double
    getPathLossExponent(double coefficient2)
    Gets path loss exponent using AltBeacon's coefficient.
    static double
    getRatio(double receivedPower, double transmittedPower)
    Gets power ratio between received power and transmitted power.
    static double
    getRatio(double coefficient1, double coefficient2, double coefficient3, double distance)
    Gets power ratio between received power and transmitted power using AltBeacon's coefficients.
    static double
    getReceivedPower(double ratio, double transmittedPower)
    Gets received power.
    static double
    getReceivedPower(double coefficient1, double coefficient2, double coefficient3, double distance, double transmittedPower)
    Gets received power using AltBeacon's coefficients.
    static double
    getTransmittedPower(double ratio, double receivedPower)
    Gets transmitted power.
    static double
    getTransmittedPower(double coefficient1, double coefficient2, double coefficient3, double distance, double receivedPower)
    Gets transmitted power using AltBeacon's coefficients.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • SPEED_OF_LIGHT

      public static final double SPEED_OF_LIGHT
      Speed of light expressed in meters per second (m/s).
      See Also:

  • Constructor Details

    • AltBeaconUtils

      private AltBeaconUtils()
      Constructor to prevent instantiation of utility class.

  • Method Details

    • getK

      public static double getK(double frequency)
      Gets k value using provided frequency. K is defined as k = c / (4 * pi * f), where: - c is the speed of light expressed in m/s. - f is the frequency expressed in Hz.
      Parameters:
      frequency - a frequency (expressed in Hz).
      Returns:
      k value.

    • getK

      public static double getK(double coefficient1, double coefficient2)
      Gets k value using AltBeacon's coefficients.
      Parameters:
      coefficient1 - 1st coefficient.
      coefficient2 - 2nd coefficient.
      Returns:
      k value.

    • getFrequency

      public static double getFrequency(double k)
      Gets frequency from k value.
      Parameters:
      k - k value.
      Returns:
      frequency expressed in Hz.

    • getFrequency

      public static double getFrequency(double coefficient1, double coefficient2)
      Gets frequency using AltBeacon's coefficients.
      Parameters:
      coefficient1 - 1st coefficient.
      coefficient2 - 2nd coefficient.
      Returns:
      frequency expressed in Hz.

    • getPathLossExponent

      public static double getPathLossExponent(double coefficient2)
      Gets path loss exponent using AltBeacon's coefficient.
      Parameters:
      coefficient2 - 2nd coefficient.
      Returns:
      path loss exponent.

    • getDistance

      public static double getDistance(double coefficient1, double coefficient2, double coefficient3, double ratio)
      Gets distance using AltBeacon's coefficients.
      Parameters:
      coefficient1 - 1st coefficient.
      coefficient2 - 2nd coefficient.
      coefficient3 - 3rd coefficient.
      ratio - ratio between received power and transmitted power.
      Returns:
      distance expressed in meters.

    • getDistance

      public static double getDistance(double coefficient1, double coefficient2, double coefficient3, double receivedPower, double transmittedPower)
      Gets distance using AltBeacon's coefficients.
      Parameters:
      coefficient1 - 1st coefficient.
      coefficient2 - 2nd coefficient.
      coefficient3 - 3rd coefficient.
      receivedPower - received power (expressed in mW).
      transmittedPower - transmitted power (expressed in mW).
      Returns:
      distance expressed in meters.

    • getRatio

      public static double getRatio(double coefficient1, double coefficient2, double coefficient3, double distance)
      Gets power ratio between received power and transmitted power using AltBeacon's coefficients.
      Parameters:
      coefficient1 - 1st coefficient.
      coefficient2 - 2nd coefficient.
      coefficient3 - 3rd coefficient.
      distance - distance expressed in meters.
      Returns:
      power ratio.

    • getRatio

      public static double getRatio(double receivedPower, double transmittedPower)
      Gets power ratio between received power and transmitted power.
      Parameters:
      receivedPower - received power (expressed in mW).
      transmittedPower - transmitted power (expressed in mW).
      Returns:
      power ratio.

    • getReceivedPower

      public static double getReceivedPower(double ratio, double transmittedPower)
      Gets received power.
      Parameters:
      ratio - ratio between received power and transmitted power.
      transmittedPower - transmitted power (expressed in mW).
      Returns:
      received power (expressed in mW).

    • getReceivedPower

      public static double getReceivedPower(double coefficient1, double coefficient2, double coefficient3, double distance, double transmittedPower)
      Gets received power using AltBeacon's coefficients.
      Parameters:
      coefficient1 - 1st coefficient.
      coefficient2 - 2nd coefficient.
      coefficient3 - 3rd coefficient.
      distance - distance expressed in meters.
      transmittedPower - transmitted power expressed in mW.
      Returns:
      received power expressed in mW.

    • getTransmittedPower

      public static double getTransmittedPower(double ratio, double receivedPower)
      Gets transmitted power.
      Parameters:
      ratio - ratio between received power and transmitted power.
      receivedPower - received power expressed in mW.
      Returns:
      transmitted power expressed in mW.

    • getTransmittedPower

      public static double getTransmittedPower(double coefficient1, double coefficient2, double coefficient3, double distance, double receivedPower)
      Gets transmitted power using AltBeacon's coefficients.
      Parameters:
      coefficient1 - 1st coefficient.
      coefficient2 - 2nd coefficient.
      coefficient3 - 3rd coefficient.
      distance - distance expressed in meters.
      receivedPower - received power expressed in mW.
      Returns:
      transmitted power expressed in mW.

    • getCoefficient1

      public static double getCoefficient1(double k, double pathLossExponent)
      Gets AltBeacon's 1st coefficient.
      Parameters:
      k - k value.
      pathLossExponent - path loss exponent.
      Returns:
      AltBeacon's 1st coefficient.

    • getCoefficient1WithFrequency

      public static double getCoefficient1WithFrequency(double frequency, double pathLossExponent)
      Gets AltBeacon's 1st coefficient.
      Parameters:
      frequency - frequency expressed in Hz.
      pathLossExponent - path loss exponent.
      Returns:
      AltBeacon's 1st coefficient.

    • getCoefficient2

      public static double getCoefficient2(double pathLossExponent)
      Gets AltBeacon's 2nd coefficient.
      Parameters:
      pathLossExponent - path loss exponent.
      Returns:
      AltBeacon's 2nd coefficient.