set val(chan)      Channel/WirelessChannel             ; #Channel Type
  set val(prop)      Propagation/TwoRayGround     ; #Radio propagation model
  set val(netif)     Phy/WirelessPhy       ; #Network interface type
  set val(ant)       Antenna/OmniAntenna       ; #Antenna model
  set val(rp)        AOMDV     ;#Routing Protocol
  set val(ifq)       Queue/DropTail/PriQueue                  ;# interface queue type
  set val(ifqlen)    50      ;# max packet in ifq
  set val(mac)       Mac/802_11      ;# MAC type
  set val(ll)        LL                         ;# link layer type
  set val(nn)        50               ;# number of mobilenodes
  set val(ni)        3               ;# number of interfaces
  set val(channum)     2     ;# number of channels per radio
  set val(cp)        ./random50100.tcl     ;      # topology traffic file 
  set val(stop)      100                ;# simulation time
  # ==================================================================
  # Main Program
  # ======================================================================
      
      
  # Initialize Global Variables
  set ns_        [new Simulator]
  set tracefd     [open ./50100.tr w]
  $ns_ trace-all $tracefd
      
  # set up topography object
  set topo       [new Topography]
  $topo load_flatgrid 1000 1000
      
  #create nam
  set namtrace [open ./50100.nam w]
  $ns_ namtrace-all-wireless $namtrace 1000 1000
      
  # Create God
  set god_ [create-god $val(nn)]
  # configure node
  $ns_ node-config -adhocRouting $val(rp) -llType $val(ll) -macType $val(mac) -ifqType $val(ifq) -ifqLen $val(ifqlen) -antType $val(ant) -propType $val(prop) -phyType $val(netif) -topoInstance $topo -agentTrace ON -routerTrace ON -macTrace ON -movementTrace ON
      
      
   for {set i 0} {$i < [expr $val(ni) * $val(channum)]} {incr i} {
                set chan_($i) [new $val(chan)]
    }
      
      
  #configure for interface and channel
  $ns_ node-config -ifNum $val(ni) -channel $chan_(0)
  $ns_ node-config -ChannelNum $val(channum)
      
  for {set i 0} {$i < [expr $val(ni) * $val(channum)]} {incr i} {
             $ns_ add-channel $i $chan_($i)
  }
      
  for {set i 0} {$i < $val(nn) } {incr i} {
         set node_($i) [$ns_ node]
           $node_($i) set recordIfall 1
         $node_($i) random-motion 0      ;# disable random motion
  $god_ new_node $node_($i)
  }
      
      
  source $val(cp)      ;    #source topology and traffic file generated by others
      
  # Tell nodes when the simulation ends
  for {set i 0} {$i < $val(nn) } {incr i} {
        $ns_ at $val(stop).0 "$node_($i) reset"; 
  }
  $ns_ at  $val(stop).0002 "puts \"NS EXITING...\" ; $ns_ halt "
  proc stop {} {
      global ns_ tracefd
      $ns_ flush-trace
      close $tracefd
      exec nam ./test.nam &
      exit 0
  }
  puts "Starting Simulation..." 
  $ns_ run