From 5aa6ec32b7d137d7923ab10cbfe976196ce0330e Mon Sep 17 00:00:00 2001
From: Tim Schubert <tim.schubert@tu-bs.de>
Date: Fri, 28 Aug 2020 13:10:21 +0200
Subject: [PATCH] Fix ISL LOS

---
 examples/leo-delay-tracing-example.cc |  9 ++++---
 model/isl-propagation-loss-model.cc   | 38 ++++++++++++++++++++-------
 2 files changed, 33 insertions(+), 14 deletions(-)

diff --git a/examples/leo-delay-tracing-example.cc b/examples/leo-delay-tracing-example.cc
index 733c48a..e0058f6 100644
--- a/examples/leo-delay-tracing-example.cc
+++ b/examples/leo-delay-tracing-example.cc
@@ -44,7 +44,7 @@ int main (int argc, char *argv[])
   uint32_t lonGws = 20;
   double interval;
   double duration;
-  bool islEnable = false;
+  bool islEnabled = false;
   bool traceDrops = false;
   bool traceTxRx = false;
   std::string routingProto = "aodv";
@@ -61,7 +61,7 @@ int main (int argc, char *argv[])
   cmd.AddValue("ttlThresh", "ns3::aodv::RoutingProtocol::TtlThreshold");
   cmd.AddValue("netDiameter", "ns3::aodv::RoutingProtocol::NetDiameter");
   cmd.AddValue("routeTimeout", "ns3::aodv::RoutingProtocol::ActiveRouteTimeout");
-  cmd.AddValue("islEnable", "Enable inter-satellite links", islEnable);
+  cmd.AddValue("islEnabled", "Enable inter-satellite links", islEnabled);
   cmd.AddValue("traceDrops", "Enable tracing of PHY and MAC drops", traceDrops);
   cmd.AddValue("traceTxRx", "Enable tracing of PHY and MAC transmits", traceTxRx);
   cmd.AddValue("latGws", "Latitudal rows of gateways", latGws);
@@ -100,7 +100,8 @@ int main (int argc, char *argv[])
   else
     {
       AodvHelper aodv;
-      //aodv.Set ("EnableHello", BooleanValue (false));
+      aodv.Set ("EnableHello", BooleanValue (false));
+      //aodv.Set ("RreqLimit", UintegerValue (2));
 
       stack.SetRoutingHelper (aodv);
     }
@@ -114,7 +115,7 @@ int main (int argc, char *argv[])
   ipv4.SetBase ("10.1.0.0", "255.255.0.0");
   ipv4.Assign (utNet);
 
-  if (islEnable)
+  if (islEnabled)
     {
       std::cerr << "ISL enabled" << std::endl;
       IslHelper islCh;
diff --git a/model/isl-propagation-loss-model.cc b/model/isl-propagation-loss-model.cc
index 3b453d6..11f365e 100644
--- a/model/isl-propagation-loss-model.cc
+++ b/model/isl-propagation-loss-model.cc
@@ -35,15 +35,19 @@ IslPropagationLossModel::~IslPropagationLossModel ()
 bool
 IslPropagationLossModel::GetLos (Ptr<MobilityModel> moda, Ptr<MobilityModel> modb)
 {
-  // TODO get max distance with line-sphere intersection
-
   // origin of LOS
-  Vector3D oc = moda->GetPosition ();
-  Vector3D bp = modb->GetPosition ();
+  Vector3D apos = moda->GetPosition ();
+  Vector3D bpos = modb->GetPosition ();
 
+  // select upper satellite as origin
+  Vector oc = apos.GetLength () > bpos.GetLength () ? apos : bpos;
+  Vector bp = apos.GetLength () > bpos.GetLength () ? bpos : apos;
+
+  Vector3D u = bp - oc;
+  // distance from s1 to s2
+  double s2 = u.GetLength ();
   // direction unit vector
-  Vector3D u = Vector3D (bp.x - oc.x, bp.y - oc.y, bp.z - oc.z);
-  u = Vector3D (u.x / u.GetLength (), u.y / u.GetLength (), u.z / u.GetLength ());
+  u = Vector3D (u.x / s2, u.y / s2, u.z / s2);
 
   double a = u.x*u.x + u.y*u.y + u.z*u.z;
   double b = 2.0 * (oc.x*u.x + oc.y*u.y + oc.z*u.z);
@@ -57,7 +61,23 @@ IslPropagationLossModel::GetLos (Ptr<MobilityModel> moda, Ptr<MobilityModel> mod
   		<<";c="<<c
   		<<";disc="<<discriminant);
 
-  return discriminant < 0;
+  if (discriminant < 0)
+    {
+      return true;
+    }
+  else
+    {
+      // distances from oc (first sat)
+      double t1 = (-b - sqrt (discriminant)) / (2.0 * a);
+      double t2 = (-b + sqrt (discriminant)) / (2.0 * a);
+
+      NS_LOG_DEBUG ("t1="<<t1
+      		    <<"t2="<<t2
+      		    <<"s2="<<s2);
+
+      // check if second sat is behind earth
+      return (s2 < abs (t1) && s2 < abs (t2));
+    }
 }
 
 double
@@ -65,14 +85,12 @@ IslPropagationLossModel::DoCalcRxPower (double txPowerDbm,
                                         Ptr<MobilityModel> a,
                                         Ptr<MobilityModel> b) const
 {
+  NS_LOG_FUNCTION (this << txPowerDbm << a << b);
   if (!GetLos (a, b))
     {
-      NS_LOG_DEBUG ("DROP;"<<a->GetPosition ()<<";"<<b->GetPosition ());
       return -1000.0;
     }
 
-  NS_LOG_DEBUG ("LOS;"<<a->GetPosition ()<<";"<<b->GetPosition ());
-
   return txPowerDbm;
 }