这个例子包含了8个移动节点【4个源节点和4个目的节点】。每个源节点是一个UDP类型的CBR源。传输包的大小为512k，传输速率为600kbps,我们假设所有的节点都在一个恒定的范围195米内，模拟的时间持续80sec.
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# ====================================================================
# Define Node Configuration paramaters
#====================================================================
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(mac) Mac/802_11 ;# MAC type
set val(ifq) Queue/DropTail/PriQueue ;# interface queue type
set val(ll) LL ;# link layer type
set val(ant) Antenna/OmniAntenna ;# antenna model
set val(ifqlen) 50 ;# max packet in ifq
set val(nn) 8 ;# number of mobilenodes
set val(rp) DSDV ;# routing protocol
set val(x) 500 ;# X dimension of the topography
set val(y) 500 ;# Y dimension of the topography
Mac/802_11 set RTSThreshold_ 3000
Mac/802_11 set basicRate_ 1Mb
Mac/802_11 set dataRate_ 2Mb
#=====================================================================
# Initialize trace file desctiptors
#=====================================================================
# *** Throughput Trace ***
set f0 [open out02.tr w]
set f1 [open out12.tr w]
set f2 [open out22.tr w]
set f3 [open out32.tr w]
# *** Packet Loss Trace ***
set f4 [open lost02.tr w]
set f5 [open lost12.tr w]
set f6 [open lost22.tr w]
set f7 [open lost32.tr w]
# *** Packet Delay Trace ***
set f8 [open delay02.tr w]
set f9 [open delay12.tr w]
set f10 [open delay22.tr w]
set f11 [open delay32.tr w]
# *** Initialize Simulator ***
set ns_ [new Simulator]
# *** Initialize Trace file ***
set tracefd [open trace2.tr w]
$ns_ trace-all $tracefd
# *** Initialize Network Animator ***
set namtrace [open sim12.nam w]
$ns_ namtrace-all-wireless $namtrace $val(x) $val(y)
# *** set up topography object ***
set topo [new Topography]
$topo load_flatgrid 500 500
# Create General Operations Director (GOD) object. It is used to store global information about the state of the environment, network, or nodes that an
# omniscent observer would have, but that should not be made known to any participant in the simulation.
create-god $val(nn)
# configure nodes
$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) \
-channelType $val(chan) \
-topoInstance $topo \
-agentTrace ON \
-routerTrace ON \
-macTrace OFF \
-movementTrace OFF
# Create Nodes
for {set i 0} {$i < $val(nn) } {incr i} {
set node_($i) [$ns_ node]
$node_($i) random-motion 0 ;# disable random motion
}
# Initialize Node Coordinates
$node_(0) set X_ 5.0
$node_(0) set Y_ 5.0
$node_(0) set Z_ 0.0
$node_(1) set X_ 200.0
$node_(1) set Y_ 5.0
$node_(1) set Z_ 0.0
$node_(2) set X_ 5.0
$node_(2) set Y_ 50.0
$node_(2) set Z_ 0.0
$node_(3) set X_ 200.0
$node_(3) set Y_ 50.0
$node_(3) set Z_ 0.0
$node_(4) set X_ 5.0
$node_(4) set Y_ 100.0
$node_(4) set Z_ 0.0
$node_(5) set X_ 200.0
$node_(5) set Y_ 100.0
$node_(5) set Z_ 0.0
$node_(6) set X_ 2.0
$node_(6) set Y_ 150.0
$node_(6) set Z_ 0.0
$node_(7) set X_ 200.0
$node_(7) set Y_ 150.0
$node_(7) set Z_ 0.0
# Setup traffic flow between nodes
# TCP connections between node_(0) and node_(1)
# Create Constant four Bit Rate Traffic sources
set agent1 [new Agent/UDP] ;# Create TCP Agent
$agent1 set prio_ 0 ;# Set Its priority to 0
set sink [new Agent/LossMonitor] ;# Create Loss Monitor Sink in order to be able to trace the number obytes received
$ns_ attach-agent $node_(0) $agent1 ;# Attach Agent to source node
$ns_ attach-agent $node_(1) $sink ;# Attach Agent to sink node
$ns_ connect $agent1 $sink ;# Connect the nodes
set app1 [new Application/Traffic/CBR] ;# Create Constant Bit Rate application
$app1 set packetSize_ 512 ;# Set Packet Size to 512 bytes
$app1 set rate_ 600Kb ;# Set CBR rate to 200 Kbits/sec
$app1 attach-agent $agent1 ;# Attach Application to agent
set agent2 [new Agent/UDP] ;# Create TCP Agent
$agent2 set prio_ 1 ;# Set Its priority to 1
set sink2 [new Agent/LossMonitor] ;# Create Loss Monitor Sink in order to be able to trace the number obytes received
$ns_ attach-agent $node_(2) $agent2 ;# Attach Agent to source node
$ns_ attach-agent $node_(3) $sink2 ;# Attach Agent to sink node
$ns_ connect $agent2 $sink2 ;# Connect the nodes
set app2 [new Application/Traffic/CBR] ;# Create Constant Bit Rate application
$app2 set packetSize_ 512 ;# Set Packet Size to 512 bytes
$app2 set rate_ 600Kb ;# Set CBR rate to 200 Kbits/sec
$app2 attach-agent $agent2 ;# Attach Application to agent
set agent3 [new Agent/UDP] ;# Create TCP Agent
$agent3 set prio_ 2 ;# Set Its priority to 2
set sink3 [new Agent/LossMonitor] ;# Create Loss Monitor Sink in order to be able to trace the number obytes received
$ns_ attach-agent $node_(4) $agent3 ;# Attach Agent to source node
$ns_ attach-agent $node_(5) $sink3 ;# Attach Agent to sink node
$ns_ connect $agent3 $sink3 ;# Connect the nodes
set app3 [new Application/Traffic/CBR] ;# Create Constant Bit Rate application
$app3 set packetSize_ 512 ;# Set Packet Size to 512 bytes
$app3 set rate_ 600Kb ;# Set CBR rate to 200 Kbits/sec
$app3 attach-agent $agent3 ;# Attach Application to agent
set agent4 [new Agent/UDP] ;# Create TCP Agent
$agent4 set prio_ 3 ;# Set Its priority to 3
set sink4 [new Agent/LossMonitor] ;# Create Loss Monitor Sink in order to be able to trace the number obytes received
$ns_ attach-agent $node_(6) $agent4 ;# Attach Agent to source node
$ns_ attach-agent $node_(7) $sink4 ;# Attach Agent to sink node
$ns_ connect $agent4 $sink4 ;# Connect the nodes
set app4 [new Application/Traffic/CBR] ;# Create Constant Bit Rate application
$app4 set packetSize_ 512 ;# Set Packet Size to 512 bytes
$app4 set rate_ 600Kb ;# Set CBR rate to 200 Kbits/sec
$app4 attach-agent $agent4 ;# Attach Application to agent
# defines the node size in Network Animator
for {set i 0} {$i < $val(nn)} {incr i} {
$ns_ initial_node_pos $node_($i) 20
}
# Initialize Flags
set holdtime 0
set holdseq 0
set holdtime1 0
set holdseq1 0
set holdtime2 0
set holdseq2 0
set holdtime3 0
set holdseq3 0
set holdrate1 0
set holdrate2 0
set holdrate3 0
set holdrate4 0
# Function To record Statistcis (Bit Rate, Delay, Drop)
proc record {} {
global sink sink2 sink3 sink4 f0 f1 f2 f3 f4 f5 f6 f7 holdtime holdseq holdtime1 holdseq1 holdtime2 holdseq2 holdtime3 holdseq3 f8 f9 f10 f11 holdrate1 holdrate2 holdrate3 holdrate4
#获得模拟器实例
set ns [Simulator instance]
#设置每0.9秒会调用本函数一次
set time 0.9 ;#Set Sampling Time to 0.9 Sec
#记录有多少字节被接收节点接收？
set bw0 [$sink set bytes_]
set bw1 [$sink2 set bytes_]
set bw2 [$sink3 set bytes_]
set bw3 [$sink4 set bytes_]
#计算每个sink丢包的数目
set bw4 [$sink set nlost_]
set bw5 [$sink2 set nlost_]
set bw6 [$sink3 set nlost_]
set bw7 [$sink4 set nlost_]
#统计每个sink收到最后一个包的时间
set bw8 [$sink set lastPktTime_]
#统计每个sink接收到的数据包个数
set bw9 [$sink set npkts_]
set bw10 [$sink2 set lastPktTime_]
set bw11 [$sink2 set npkts_]
set bw12 [$sink3 set lastPktTime_]
set bw13 [$sink3 set npkts_]
set bw14 [$sink4 set lastPktTime_]
set bw15 [$sink4 set npkts_]
#获取当前时间
set now [$ns now]
# Record Bit Rate in Trace Files写入带宽
puts $f0 "$now [expr (($bw0+$holdrate1)*8)/(2*$time*1000000)]"
puts $f1 "$now [expr (($bw1+$holdrate2)*8)/(2*$time*1000000)]"
puts $f2 "$now [expr (($bw2+$holdrate3)*8)/(2*$time*1000000)]"
puts $f3 "$now [expr (($bw3+$holdrate4)*8)/(2*$time*1000000)]"
# Record Packet Loss Rate in File写入丢包率
puts $f4 "$now [expr $bw4/$time]" #丢包的数目除以某个时间段值
puts $f5 "$now [expr $bw5/$time]"
puts $f6 "$now [expr $bw6/$time]"
puts $f7 "$now [expr $bw7/$time]"
# Record Packet Delay in File
#计算end-to-end delay-暂时还不清楚计算法则~~~
if { $bw9 > $holdseq } {
puts $f8 "$now [expr ($bw8 - $holdtime)/($bw9 - $holdseq)]"
} else {
puts $f8 "$now [expr ($bw9 - $holdseq)]"
}
if { $bw11 > $holdseq1 } {
puts $f9 "$now [expr ($bw10 - $holdtime1)/($bw11 - $holdseq1)]"
} else {
puts $f9 "$now [expr ($bw11 - $holdseq1)]"
}
if { $bw13 > $holdseq2 } {
puts $f10 "$now [expr ($bw12 - $holdtime2)/($bw13 - $holdseq2)]"
} else {
puts $f10 "$now [expr ($bw13 - $holdseq2)]"
}
if { $bw15 > $holdseq3 } {
puts $f11 "$now [expr ($bw14 - $holdtime3)/($bw15 - $holdseq3)]"
} else {
puts $f11 "$now [expr ($bw15 - $holdseq3)]"
}
# Reset Variables
$sink set bytes_ 0
$sink2 set bytes_ 0
$sink3 set bytes_ 0
$sink4 set bytes_ 0
$sink set nlost_ 0
$sink2 set nlost_ 0
$sink3 set nlost_ 0
$sink4 set nlost_ 0
set holdtime $bw8
set holdseq $bw9
set holdrate1 $bw0
set holdrate2 $bw1
set holdrate3 $bw2
set holdrate4 $bw3
$ns at [expr $now+$time] "record" ;# Schedule Record after $time interval sec
}
# Start Recording at Time 0
$ns_ at 0.0 "record"
$ns_ at 1.4 "$app1 start" ;# Start transmission at time t = 1.4 Sec
$ns_ at 10.0 "$app2 start" ;# Start transmission at time t = 10 Sec
$ns_ at 20.0 "$app3 start" ;# Start transmission at time t = 20 Sec
$ns_ at 30.0 "$app4 start" ;# Start transmission at time t = 30 Sec
# Stop Simulation at Time 80 sec
$ns_ at 80.0 "stop"
# Reset Nodes at time 80 sec
for {set i 0} {$i < $val(nn) } {incr i} {
$ns_ at 80.0 "$node_($i) reset";
}
# Exit Simulatoion at Time 80.01 sec
$ns_ at 80.01 "puts \"NS EXITING...\" ; $ns_ halt"
proc stop {} {
global ns_ tracefd f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11
# Close Trace Files
close $f0
close $f1
close $f2
close $f3
close $f4
close $f5
close $f6
close $f7
close $f8
close $f9
close $f10
close $f11
# Plot Recorded Statistics
exec xgraph out02.tr out12.tr out22.tr out32.tr -geometry 800x400 &
exec xgraph lost02.tr lost12.tr lost22.tr lost32.tr -geometry 800x400 &
exec xgraph delay02.tr delay12.tr delay22.tr delay32.tr -geometry 800x400 &
# Reset Trace File
$ns_ flush-trace
close $tracefd
exit 0
}
puts "Starting Simulation..."
$ns_ run
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[simulation results]
Throughput:
Analysis: Node 1 starts transmitting at time T =1.4 sec while Node 2 starts transmitting at time T=10 sec. During the period of time [1.4 sec, 10 sec] Node 1 is the only transmitting node using the entire available bandwidth. This justifies the high performance of Node 1 during the specified interval of time. At time T=10 sec, Node 2 starts transmission hence sharing channel resources with Node 1. This explains the heavy reduction of bit rate. In addition, the bit rate plot experiences heavier oscillations and reduction as the number of transmitting nodes increases. Oscillations are reflected in heavy disorders in network performance.
Packet Drop Rate:
Analysis: This figure shows a high packet drop rate whenever the number of nodes sharing network resources increases. It can be shown that the packet drop rate in the interval [1.4 sec, 10 sec] is 0. This can be easily justified since only one node is using the network during this time interval. However this high-quality performance is deteriorated as more nodes start sharing the network resources.
Average Packets End to End Delay:
Analysis: When the number of nodes that are sharing the network resources, the delay significantly increases and readjusting CW of each node takes longer time.
[Reference]
J. Naoum-Sawaya, B. Ghaddar, S. Khawam, H. Safa, H. Artail, and Z. Dawy, "," in IEEE International Conference on Wireless and Mobile Computing , Networking and Communications (WiMob 2005), Montreal, Canada, August 2005
