Introduction:
LTE is designed for frequency reuse 1 (To maximize spectrum efficiency), which means that all the neighbor cells are using same frequency channels and therefore there is no cell-planning to deal with the interference issues There is a high probability that a resource block scheduled to cell edge user, is also being transmitted by neighbor cell, resulting in high interference, eventually low throughput or call drops (see figure) Traffic channel can sustain upto 10% of BLER in low SINR but control channels cannot. Neighbor interference can result in radio link failures at cell edge. Heterogeneous networks require some sort of interference mitigation, since pico-cells/femto cells and macro-cells are overlapping in many scenarios
LTE in NS2:
---------Steps for patching LTE module in NS-2-------
Step 1:
Download the LTE patch tk-8.4-lastevent.patch
Step 2:
put the LTE patch in ns-allinone-2.33/tk8.4.18/
Step 3:
cd ns-allinone-2.33/tk8.4.18/
Step 4:
patch -p0 < tk-8.4-lastevent.patch
cd ../
Step 5:
./install
Step 6:
cd ns-2.33/ && mv ns ns233 && make clean && mv Makefile Makefile.org
Step 7:
svn checkout http://lte-model.googlecode.com/svn/trunk/ lte-model-read-only
Step 8:
mkdir project
cd lte-model-read-only/
Step 9:
sh checkin
cd ../
Step 10:
Edit the new Makefile , lines 41, 67, 82 to actual location in ns-allinone-2.33/ns-2.33/
Step 11:
make
TCL Script for LTE network:
# Define the multicast mechanism
set ns [new Simulator -multicast on]
# Predefine tracing
set f [open out.tr w]
$ns trace-all $f
#set nf [open out.nam w]
#$ns namtrace-all $nf
# Set the number of subscribers
set number 10
# qos_ means whether classfication/scheduling mechanism is used
Queue/LTEQueue set qos_ true
# flow_control_ is used in the model phase
Queue/LTEQueue set flow_control_ false
# later HVQ flow control mechanism is used
Queue/LTEQueue set HVQ_UE true
Queue/LTEQueue set HVQ_eNB false
Queue/LTEQueue set HVQ_cell false
# Define the LTE topology
# UE(i) <--> eNB <--> aGW <--> server
# Other configuration parameters see ~ns/tcl/lib/ns-default.tcl
# step 1: define the nodes, the order is fixed!!
set eNB [$ns node];#node id is 0
set aGW [$ns node];#node id is 1
set server [$ns node];#node id is 2
for { set i 0} {$i<$number} {incr i} {
set UE($i) [$ns node];#node id is > 2
}
# step 2: define the links to connect the nodes
for { set i 0} {$i<$number} {incr i} {
$ns simplex-link $UE($i) $eNB 10Mb 2ms LTEQueue/ULAirQueue
$ns simplex-link $eNB $UE($i) 10Mb 2ms LTEQueue/DLAirQueue
}
$ns simplex-link $eNB $aGW 1000Mb 2ms LTEQueue/ULS1Queue
$ns simplex-link $aGW $eNB 1000Mb 2ms LTEQueue/DLS1Queue
# The bandwidth between aGW and server is not the bottleneck.
$ns simplex-link $aGW $server 5000Mb 2ms DropTail
$ns simplex-link $server $aGW 5000Mb 2ms LTEQueue/DLQueue
# step 3: define the traffic, based on TR23.107 QoS concept and architecture
# class id class type simulation application
# -------------------------------------------------
# 0: Conversational: Session/RTP/RTPAgent
# 1: Streaming: CBR/UdpAgent
# 2: Interactive: HTTP/TcpAgent (HTTP/Client, HTTP/Cache, HTTP/Server)
# 3: Background: FTP/TcpAgent
# step 3.1 define the conversational traffic
set mproto DM
set mrthandle [$ns mrtproto $mproto {}]
for { set i 0} {$i<$number} {incr i} {
set s0($i) [new Session/RTP]
set s1($i) [new Session/RTP]
set group($i) [Node allocaddr]
#Adaptive Multi-Rate call bit rates:
#AMR: 12.2, 10.2, 7.95, 7.40, 6.70, 5.90, 5.15 and 4.75 kb/s
$s0($i) session_bw 12.2kb/s
$s1($i) session_bw 12.2kb/s
$s0($i) attach-node $UE($i)
$s1($i) attach-node $server
$ns at 0.4 "$s0($i) join-group $group($i)"
$ns at 0.5 "$s0($i) start"
$ns at 0.6 "$s0($i) transmit 12.2kb/s"
$ns at 0.7 "$s1($i) join-group $group($i)"
$ns at 0.8 "$s1($i) start"
$ns at 0.9 "$s1($i) transmit 12.2kb/s"
}
# step 3.2 define the streaming traffic
for { set i 0} {$i<$number} {incr i} {
set null($i) [new Agent/Null]
$ns attach-agent $UE($i) $null($i)
set udp($i) [new Agent/UDP]
$ns attach-agent $server $udp($i)
$ns connect $null($i) $udp($i)
$udp($i) set class_ 1
set cbr($i) [new Application/Traffic/CBR]
$cbr($i) attach-agent $udp($i)
$ns at 0.4 "$cbr($i) start"
$ns at 40.0 "$cbr($i) stop"
}
# step 3.3 define the interactive traffic
$ns rtproto Session
set log [open "http.log" w]
# Care must be taken to make sure that every client sees the same set of pages as the servers to which they are attached.
set pgp [new PagePool/Math]
set tmp [new RandomVariable/Constant] ;# Size generator
$tmp set val_ 10240 ;# average page size
$pgp ranvar-size $tmp
set tmp [new RandomVariable/Exponential] ;# Age generator
$tmp set avg_ 4 ;# average page age
$pgp ranvar-age $tmp
set s [new Http/Server $ns $server]
$s set-page-generator $pgp
$s log $log
set cache [new Http/Cache $ns $aGW]
$cache log $log
for { set i 0} {$i<$number} {incr i} {
set c($i) [new Http/Client $ns $UE($i)]
set ctmp($i) [new RandomVariable/Exponential] ;# Poisson process
$ctmp($i) set avg_ 1 ;# average request interval
$c($i) set-interval-generator $ctmp($i)
$c($i) set-page-generator $pgp
$c($i) log $log
}
$ns at 0.4 "start-connection"
proc start-connection {} {
global ns s cache c number
$cache connect $s
for { set i 0} {$i<$number} {incr i} {
$c($i) connect $cache
$c($i) start-session $cache $s
}
}
# step 3.4 define the background traffic
# no parameters to be configured by FTP
# we can configue TCP and TCPSink parameters here.
for { set i 0} {$i<$number} {incr i} {
set sink($i) [new Agent/TCPSink]
$ns attach-agent $UE($i) $sink($i)
set tcp($i) [new Agent/TCP]
$ns attach-agent $server $tcp($i)
$ns connect $sink($i) $tcp($i)
$tcp($i) set class_ 3
set ftp($i) [new Application/FTP]
$ftp($i) attach-agent $tcp($i)
$ns at 0.4 "$ftp($i) start"
}
# finish tracing
$ns at 30 "finish"
proc finish {} {
global ns f log
#global ns f nf log
$ns flush-trace
flush $log
close $log
close $f
#close $nf
#puts "running nam..."
#exec nam out.nam &
exit 0
}
# Finally, start the simulation.
$ns run
Outputs:
Topology Creation:
Data Transmission:
