# Create a new simulation environment
set ns [new Simulator]

# Enable OLSR routing
$ns olsr

# Create nodes
set node(0) [$ns node]
set node(1) [$ns node]
set node(2) [$ns node]
set node(3) [$ns node]

# Create a wireless channel
set channel [new Channel/WirelessChannel]

# Create a propagation loss model
set loss [new Propagation/TwoRayGround]

# Create a wireless physical layer
set phy [new Phy/WirelessPhy]

# Create a wireless MAC layer
set mac [new Mac/802_11]

# Create a wireless device
set dev [new NetDeviceContainer]
$dev Create $phy $mac

# Install the device on the nodes
$dev Install $node(0) $channel
$dev Install $node(1) $channel
$dev Install $node(2) $channel
$dev Install $node(3) $channel

# Set up the mobility model
set mobility [new MobilityModel/RandomWalk]
$mobility SetAttribute("Bounds", "0|200|0|200|0|0")

# Install the mobility model on the nodes
$ns initial_node_pos $node(0) 50 100 0
$ns initial_node_pos $node(1) 150 100 0
$ns initial_node_pos $node(2) 100 50 0
$ns initial_node_pos $node(3) 100 150 0

# Set up OLSR routing
set olsr [new Agent/OLSR]
$olsr SetDebugLevel(2)

# Install OLSR on the nodes
$ns attach-agent $node(0) $olsr
$ns attach-agent $node(1) $olsr
$ns attach-agent $node(2) $olsr
$ns attach-agent $node(3) $olsr

# Create a UDP traffic source and sink
set udp [new Agent/UDP]
$ns attach-agent $node(0) $udp

set null [new Agent/Null]
$ns attach-agent $node(3) $null

set sink [new Agent/UDP]
$ns attach-agent $node(3) $sink

# Create a traffic model
set traffic [new Application/Traffic/Constant]
$traffic attach-agent $udp
$traffic SetType(1)
$traffic SetPacketSize(1024)
$traffic SetRate(1Mbps)
$traffic SetMaxBytes(1000000)

# Connect the traffic source and sink
$ns connect $udp $sink

# Create a trace file for mobility
set tracefile [open "olsr-mobility.tr" w]
$mobility set_tracefile $tracefile

# Schedule events
$ns at 0.0 "$mobility resume"
$ns at 5.0 "$traffic start"
$ns at 20.0 "$traffic stop"
$ns at 25.0 "finish"

# Define the 'finish' procedure
proc finish {} {
    global ns tracefile
    $ns flush-trace
    close $tracefile
    exec nam olsr-mobility.nam &
    exit 0
}

# Run the simulation
$ns run