Change link cost for LQI 1 from 6 to 4. (#258)

src/core/thread/mle_constants.hpp

@@ -92,6 +92,13 @@ enum
     kReedAdvertiseJitter        = 60,   ///< REED_ADVERTISEMENT_JITTER (seconds)
 };
 
+enum
+{
+    kLqi3LinkCost               = 1,    ///< Link Cost for LQI 3
+    kLqi2LinkCost               = 2,    ///< Link Cost for LQI 2
+    kLqi1LinkCost               = 4,    ///< Link Cost for LQI 1
+    kLqi0LinkCost               = 16,   ///< Link Cost for LQI 0
+};
 
 }  // namespace Mle
 

src/core/thread/mle_router.cpp

@@ -1016,16 +1016,16 @@ uint8_t MleRouter::LqiToCost(uint8_t aLqi)
     switch (aLqi)
     {
     case 1:
-        return 6;
+        return kLqi1LinkCost;
 
     case 2:
-        return 2;
+        return kLqi2LinkCost;
 
     case 3:
-        return 1;
+        return kLqi3LinkCost;
 
     default:
-        return 16;
+        return kLqi0LinkCost;
     }
 }