Updated antenna gain documentation to reflect the fact that its value is referenced to the isotropic antenna.

#563

Author: mluis1

src/mac/LoRaMac.h

@@ -1575,13 +1575,21 @@ typedef enum eMib
      * The antenna gain is used to calculate the TX power of the node.
      * The formula is:
      * radioTxPower = ( int8_t )floor( maxEirp - antennaGain )
+     * 
+     * \remark The antenna gain value is referenced to the isotropic antenna.
+     *         The value is in dBi.
+     *         MIB_ANTENNA_GAIN[dBi] = measuredAntennaGain[dBd] + 2.15
      */
     MIB_ANTENNA_GAIN,
     /*!
      * Default antenna gain of the node. Default value is region specific.
      * The antenna gain is used to calculate the TX power of the node.
      * The formula is:
      * radioTxPower = ( int8_t )floor( maxEirp - antennaGain )
+     * 
+     * \remark The antenna gain value is referenced to the isotropic antenna.
+     *         The value is in dBi.
+     *         MIB_DEFAULT_ANTENNA_GAIN[dBi] = measuredAntennaGain[dBd] + 2.15
      */
     MIB_DEFAULT_ANTENNA_GAIN,
     /*!

src/mac/region/RegionCommon.h

@@ -385,12 +385,16 @@ void RegionCommonComputeRxWindowParameters( double tSymbol, uint8_t minRxSymbols
 
 /*!
  * \brief Computes the txPower, based on the max EIRP and the antenna gain.
+ * 
+ * \remark US915 region uses a conducted power as input value for maxEirp.
+ *         Thus, the antennaGain parameter must be set to 0.
  *
  * \param [IN] txPower TX power index.
  *
  * \param [IN] maxEirp Maximum EIRP.
  *
- * \param [IN] antennaGain Antenna gain.
+ * \param [IN] antennaGain Antenna gain. Referenced to the isotropic antenna.
+ *                         Value is in dBi. ( antennaGain[dBi] = measuredAntennaGain[dBd] + 2.15 )
  *
  * \retval Returns the physical TX power.
  */