diff --git a/examples/wimax/wimax-multicast.cc b/examples/wimax/wimax-multicast.cc
index cf3d30066..3074ded7c 100644
--- a/examples/wimax/wimax-multicast.cc
+++ b/examples/wimax/wimax-multicast.cc
@@ -150,7 +150,7 @@ int main (int argc, char *argv[])
   BSPosition = CreateObject<ConstantPositionMobilityModel> ();
 
   BSPosition->SetPosition (Vector (1000, 0, 0));
-  dev->GetPhy ()->SetMobility (BSPosition);
+  bsNodes.Get (0)->AggregateObject (BSPosition);
   bsDevs.Add (dev);
   if (verbose)
     {
@@ -169,7 +169,7 @@ int main (int argc, char *argv[])
 
       ss[i] = ssDevs.Get (i)->GetObject<SubscriberStationNetDevice> ();
       ss[i]->SetModulationType (WimaxPhy::MODULATION_TYPE_QAM16_12);
-      ss[i]->GetPhy ()->SetMobility (SSPosition[i]);
+      ssNodes.Get (i)->AggregateObject (SSPosition[i]);
 
     }
 
diff --git a/src/devices/wimax/bs-link-manager.cc b/src/devices/wimax/bs-link-manager.cc
index fcfae2bce..258a6952c 100644
--- a/src/devices/wimax/bs-link-manager.cc
+++ b/src/devices/wimax/bs-link-manager.cc
@@ -93,11 +93,12 @@ BSLinkManager::ProcessRangingRequest (Cid cid, RngReq rngreq)
                    * m_bs->GetSymbolDuration ().GetSeconds ());
     }
 
-  NS_ASSERT_MSG (Simulator::Now () >= m_bs->GetUlSubframeStartTime () && Simulator::Now () < irIntervalBoundary,
-                 "Base station: Error while processing ranging request: out of time");
   tries++;
 
-  PerformRanging (cid, rngreq);
+  if (Simulator::Now () >= m_bs->GetUlSubframeStartTime () && Simulator::Now () < irIntervalBoundary)
+    {
+       PerformRanging (cid, rngreq);
+    }
 }
 
 void
diff --git a/src/devices/wimax/simple-ofdm-wimax-channel.cc b/src/devices/wimax/simple-ofdm-wimax-channel.cc
index 314789740..aae4df055 100644
--- a/src/devices/wimax/simple-ofdm-wimax-channel.cc
+++ b/src/devices/wimax/simple-ofdm-wimax-channel.cc
@@ -145,23 +145,19 @@ SimpleOfdmWimaxChannel::Send (Time BlockTime,
   double rxPowerDbm = 0;
   Ptr<MobilityModel> senderMobility = 0;
   Ptr<MobilityModel> receiverMobility = 0;
-  if (phy->GetMobility ())
-    {
-      senderMobility = phy->GetMobility ()->GetObject<MobilityModel> ();
-    }
+  senderMobility = phy->GetDevice ()->GetNode ()->GetObject<MobilityModel> ();
 
   for (std::list<Ptr<SimpleOfdmWimaxPhy> >::iterator iter = m_phyList.begin (); iter != m_phyList.end (); ++iter)
     {
-      double delay = 0;
+      Time delay = Seconds(0);
       if (phy != *iter)
         {
-          if ((*iter)->GetMobility ())
-            {
-              receiverMobility = (*iter)->GetMobility ()->GetObject<MobilityModel> ();
-            }
+          double distance = 0;
+          receiverMobility = (*iter)->GetDevice ()->GetNode ()->GetObject<MobilityModel> ();
           if (receiverMobility != 0 && senderMobility != 0 && m_loss != 0)
             {
-              delay = (senderMobility->GetDistanceFrom (receiverMobility)) / 300000000LL;
+              distance = senderMobility->GetDistanceFrom (receiverMobility);
+              delay =  Seconds(distance/300000000.0);
               rxPowerDbm = m_loss->CalcRxPower (rxPowerDbm, senderMobility, receiverMobility);
             }
           simpleOfdmSendParam * param = new simpleOfdmSendParam (fecBlock,
@@ -183,7 +179,7 @@ SimpleOfdmWimaxChannel::Send (Time BlockTime,
               dstNode = dstNetDevice->GetObject<NetDevice> ()->GetNode ()->GetId ();
             }
           Simulator::ScheduleWithContext (dstNode,
-                                          Seconds (delay) + BlockTime,
+                                          delay,
                                           &SimpleOfdmWimaxChannel::EndSend,
                                           this,
                                           *iter,
@@ -196,7 +192,6 @@ SimpleOfdmWimaxChannel::Send (Time BlockTime,
 void
 SimpleOfdmWimaxChannel::EndSend (Ptr<SimpleOfdmWimaxPhy> rxphy, simpleOfdmSendParam * param)
 {
-  // std::cout << "END_SEND ";
   rxphy->StartReceive (param->GetFecBlock (),
                        param->GetBurstSize (),
                        param->GetIsFirstBlock (),
diff --git a/src/devices/wimax/simple-ofdm-wimax-phy.cc b/src/devices/wimax/simple-ofdm-wimax-phy.cc
index 4ba774217..48329552f 100644
--- a/src/devices/wimax/simple-ofdm-wimax-phy.cc
+++ b/src/devices/wimax/simple-ofdm-wimax-phy.cc
@@ -311,12 +311,7 @@ SimpleOfdmWimaxPhy::EndSendFecBlock (WimaxPhy::ModulationType modulationType,
     }
   else
     {
-      Simulator::Schedule (Seconds (0),
-                           &SimpleOfdmWimaxPhy::StartSendFecBlock,
-                           this,
-                           false,
-                           modulationType,
-                           direction);
+      StartSendFecBlock(false,modulationType,direction);
     }
 }
 
@@ -392,7 +387,7 @@ SimpleOfdmWimaxPhy::StartReceive (const bvec &fecBlock,
               SetBlockParameters (burstSize, modulationType);
               m_blockTime = GetBlockTransmissionTime (modulationType);
             }
-          Simulator::Schedule (Seconds (0),
+          Simulator::Schedule (m_blockTime,
                                &SimpleOfdmWimaxPhy::EndReceiveFecBlock,
                                this,
                                fecBlock,