[Positioning] Use AccessPoint::friis_constant_term()

Use AccessPoint::friis_constant_term() wherever possible.
Fix MultilaterationAlgorithm::make_constant_term() and
ReferencePoint::friis_indexes_for_ap(), where the AP's trx
power was used instead of the mobile's power.

TODO

@@ -73,8 +73,6 @@
    ° Cannot compute the error (Real) with autocalibration requests.
 
 - Algorithms
-   ° Check MultilaterationAlgorithm::make_constant_term().
-   Hint: mobile.trx_power() vs. ap.trx_power().
    ° MinMax: use a different step for X, Y and Z?
 
 - Autocalibration

owlps-positioning/src/multilaterationalgorithm.cc

@@ -47,19 +47,15 @@ double MultilaterationAlgorithm::
 make_constant_term(const Measurement &measurement)
 {
   assert(request) ;
-  assert(request->get_mobile()) ;
+  const Mobile *mobile = request->get_mobile() ;
+  assert(mobile) ;
   const AccessPoint *ap = measurement.get_ap() ;
   assert(ap) ;
 
   return
-    ap->get_trx_power() +
-    ap->get_antenna_gain() +
-    20 * log10(
-      static_cast<double>(PosUtil::LIGHT_SPEED) /
-      ap->get_frequency() /
-      (4 * M_PI)
-    ) +
-    request->get_mobile()->get_antenna_gain() ;
+    ap->friis_constant_term() +
+    mobile->get_antenna_gain() +
+    mobile->get_trx_power() ;
 }
 
 

owlps-positioning/src/referencepoint.cc

@@ -204,13 +204,7 @@ float ReferencePoint::
 friis_index_for_ap(const string &ap_mac) const
 {
   const AccessPoint &ap = Stock::get_ap(ap_mac) ;
-
-  double ap_freq = ap.get_frequency() ;
-  double const_term =
-    ap.get_antenna_gain()
-    - 20 * log10(4 * M_PI)
-    + 20 * log10(PosUtil::LIGHT_SPEED / ap_freq)
-    + ap.get_trx_power() ;
+  double const_term = ap.friis_constant_term() ;
 
   int nb_friis_idx = 0 ;
   double friis_idx_sum =
@@ -258,8 +252,10 @@ float ReferencePoint::friis_indexes_for_ap(
           assert((*request)->get_mobile()) ;
           float mobile_gain =
             (*request)->get_mobile()->get_antenna_gain() ;
+          float mobile_pow =
+            (*request)->get_mobile()->get_trx_power() ;
           friis_idx_sum +=
-            (const_term + mobile_gain - ss)
+            (const_term + mobile_gain + mobile_pow - ss)
             / (10 * log10(distance)) ;
           ++nb_indexes ;
         }

owlps-positioning/src/stock.cc

@@ -281,12 +281,7 @@ void Stock::update_all_friis_indexes()
       int nb_friis_idx = 0 ;
 
       // Compute main general term, independant from scans
-      double ap_freq = ap->second.get_frequency() ;
-      double const_term =
-        ap->second.get_antenna_gain()
-        - 20 * log10(4 * M_PI)
-        + 20 * log10(PosUtil::LIGHT_SPEED / ap_freq)
-        + ap->second.get_trx_power() ;
+      double const_term = ap->second.friis_constant_term() ;
 
       /*
        * Compute indexes for each ReferencePoint. The Friis index for an
@@ -566,14 +561,8 @@ void Stock::generate_reference_point(const Point3D &point)
       // Distance RX-P
       float point_dst =
         rx_coord.distance(point) ;
-      // Constants & common data
-      double wavelength =
-        static_cast<double>(PosUtil::LIGHT_SPEED) /
-        rx->second.get_frequency() ;
-      double common_ss =
-        rx->second.get_antenna_gain() +
-        20 * log10(wavelength) -
-        20 * log10(4 * M_PI) ;
+      // Constant term
+      double common_ss = rx->second.friis_constant_term() ;
       // SS for REF1
       const ReferencePoint &ref1_rp =
         get_reference_point(ref1_coord) ;