NS-2 Wireless 802.11 WLAN

Network Network Simulator:Simulator:

802.11 WLAN802.11 WLAN

Daniele Messina, Ilenia Tinnirello

Wireless SimulationsWireless Simulations A mobile node consists of several network components including:

Link Layer Interface Queue MAC PHY

Other parameters need to be defined: radio propagation model type of ad-hoc routing type of antenna


type of antenna

set val(chan) Channel/WirelessChannel ;# channel typeset val(prop) Propagation/TwoRayGround ;# radio-propagation

modelset val(ant) Antenna/OmniAntenna ;# Antenna typeset val(ll) LL ;# Link layer typeset val(ifq) Queue/DropTail/PriQueue ;# Interface queue typeset val(ifqlen) 50 ;# max packet in ifqset val(netif) Phy/WirelessPhy ;# network interface typeset val(mac) Mac/802_11 ;# MAC typeset val(rp) DSDV ;# ad-hoc routing

protocol set val(nn) 2 ;# number of mobilenodes

Wireless Node StructureWireless Node Structure

Node

ARPLLLLLL

Classifier: Forwarding

Agent: Protocol Entity

Node Entry

LL: Link layer object

protocolagent

routingagent

addrclassifier

portclassifier

255

defaulttarget_


ARP

Propagation and antenna models

MobileNode

LL

MAC

PHY

LL

CHANNEL

LL

MAC

PHY

LL: Link layer object

IFQ: Interface queue

MAC: Mac object

PHY: Net interface

IFQIFQ

Radio propagation/antenna models

Prop/ant

Wireless SimulationsWireless Simulations

We need a topology object that keeps track of movements of mobilenodes within the topological boundary.

set topo [new Topography]

Mobilenodes move within a topology of 500mX500m. We provide the topography object with x and y


Mobilenodes move within a topology of 500mX500m. We provide the topography object with x and y coordinates of the boundary, (x=500, y=500) :

$topo load_flatgrid 500 500#file:simple-wireless.tcl


Next we create the object God, as follows:

create-god $val(nn)

God (General Operations Director) stores:

the total number of mobilenodes


the total number of mobilenodes

a table of shortest number of hops required to reach from one node to another.

the next hop information is normally loaded into god object from movement pattern files.


We need to configure nodes:

# $ns_ node-config -addressingType flat or hierarchical or expanded

# -adhocRouting DSDV or DSR or TORA# -llType LL# -macType Mac/802_11# -propType "Propagation/TwoRayGround"# -ifqType "Queue/DropTail/PriQueue"# -ifqLen 50# -phyType "Phy/WirelessPhy"


# -phyType "Phy/WirelessPhy"# -antType "Antenna/OmniAntenna"# -channelType "Channel/WirelessChannel"# -topoInstance $topo# -energyModel "EnergyModel"# -initialEnergy (in Joules)# -rxPower (in W)# -txPower (in W)# -agentTrace ON or OFF# -routerTrace ON or OFF# -macTrace ON or OFF# -movementTrace ON or OFF

Wireless simulationsWireless simulations

# Create nodes:for {set i 0} {$i < $val(nn) } {incr i} {

set node_($i) [$ns_ node ]$node_($i) random-motion 0;# disable random motion

}

# Provide initial (X,Y,Z) co-ordinates for node_(0)


# Provide initial (X,Y,Z) co-ordinates for node_(0) and node_(1)

$node_(0) set X_ 5.0$node_(0) set Y_ 2.0$node_(0) set Z_ 0.0

$node_(1) set X_ 390.0$node_(1) set Y_ 385.0$node_(1) set Z_ 0.0


# Produce some node movements ## Node_(1) starts to move towards node_(0)# command: $node setdest $ns_ at 50.0 "$node_(1) setdest 25.0 20.0 15.0"$ns_ at 10.0 "$node_(0) setdest 20.0 18.0 1.0"


# Node_(1) then starts to move away from node_(0)$ns_ at 100.0 "$node_(1) setdest 490.0 480.0 15.0"


# Tell nodes when the simulation ends#for {set i 0} {$i < $val(nn) } {incr i} {

$ns_ at 150.0 "$node_($i) reset";}$ns_ at 150.0001 "stop"$ns_ at 150.0002 "puts \"NS EXITING...\" ; $ns_ halt"


$ns_ at 150.0002 "puts \"NS EXITING...\" ; $ns_ halt"

proc stop {} {global ns_ tracefdclose $tracefd

}

puts "Starting Simulation..."$ns_ run

Wireless TraceWireless Trace

[65536:0 16777984:0 31 16777984] [1 0] 2 0

r 160.093884945 _6_ RTR --- 5 tcp 1492 [a2 4 6 800] -------

MAC

NETWORK TRANSPORT


TCP packet received by routing agent of node 6 at time 160.09...UID: 5size: 1492Mac Layer fields: time src_addr dst_addr type (800: IP, 806: ARP) Network Layer fields: src_addr dst_addr TTL next_hop_addr Transport Layer fields: seq_no ack_no no_of_fwds opt_no_of_fwds

New Wireless Trace FormatNew Wireless Trace Format

enabled by the command

$ns use-newtraceavailable only for wireless simulations

adds:

coordinates log


coordinates log

energy log

reason code for the event

flow id

duration at PHY layer

Wireless Nam TraceWireless Nam Trace

Enabling nam trace for wireless simulation:

set namtrace [open wireless1-out.nam w]$ns_ namtrace-all-wireless $namtrace $val(x) $val(y)


Note: We are able to see only MAC Layer packet

exchanges

#file:wireless1.tcl

Creating scenario files for Creating scenario files for mobility simulationsmobility simulations

To create the scenario, run

cd /indep-utils/cmu-scen-gen/setdest


./setdest [-v version of setdest] [-n num_of_nodes] [-p pausetime] [-s maxspeed] [-t simtime] [-x maxx] [-y maxy]> [outdir/movement-file]

Wireless Channel and MACWireless Channel and MAC

Duplicate packets to all mobile nods attached to channel

except the source

Each receiver is responsible to decide if it can receive the

packet

Each receiver evaluates the received power Pr on the

basis of the Propagation Model

Antenna: Unit Gain Omni-directional


Antenna: Unit Gain Omni-directional

Fee Space, TwpRayground, Shadowing

If Pr > Pthreshold, the packet is received

N1 N2 N3

CHANNEL_1

N4

CHANNEL_2

N4 cannot hear N1, N2 and N3

PHY Layer ParametersPHY Layer Parameters

Transmission Power: set by default at 0.2818W

(corresponding to a coverage range of 250m)

Phy/WirelessPhy set Pt_ 0.2818

Capture threshold: indicates the power ratio over which a

collision results in the reception of the strongest packet


Phy/WirelessPhy set CPThresh_ 10.0

Carrier Sense and Reception thresholds: indicate the

power threshold over which a packet is sensed or

correctly received

Phy/WirelessPhy set CSThresh_ 1.559e-11

Phy/WirelessPhy set RXThresh_ 3.652e-10

Transmission/Interference/CS RangeTransmission/Interference/CS Range

TX


TX

Correct reception (if no collision)

Incorrect reception

TX detected, but no reception

No Interference from TX

MAC Layer ParametersMAC Layer Parameters

Contention Parameters: minimum and

maximum contention windows, backoff slot,

SIFS (DIFS=SIFS+2*backoff slot)

Mac/802_11 set CWMin_ 31

Mac/802_11 set CWMax_ 1023


Mac/802_11 set CWMax_ 1023

Mac/802_11 set SlotTime_ 0.000020

Mac/802_11 set SIFS_ 0.000010

RTS Threshold (over which the 4way

handshake is used)

Mac/802_11 set RTSThreshold_ 0

MAC Layer ParametersMAC Layer Parameters

Data Rate: rate at which data frames are sent

over the wireless medium (default: 1 Mbps)

Although only some rates are standardized, in principle each

configuration is possible


configuration is possible

MAC/802_11 set dataRate_ 11.0e6

Basic Rate: rate at which ACK, RTS/CTS

frames are sent over the wireless medium

(default: 1 Mbps, usually: 2 Mbps)

MAC/802_11 set basicRate 2.0e6

Energy modelEnergy model

The energy model represents level of energy in a mobile host.

The energy model in a node has an initial value which is the level of energy the node has at the beginning of the simulation. This is known as initialEnergy.


It also has a given energy usage for every packet it transmits and receives, for idle and sleep states and for transitions (txPower, rxPower, idlePower, sleepPower, transitionPower)


When the energy level at the node goes down to zero, no more packets can be received or transmitted by the node

OTcl interface: $ns_ node-config...

-energyModel $opt(energymodel) \ #EnergyModel


-energyModel $opt(energymodel) \ #EnergyModel-idlePower 1.0 \ #watts-rxPower 1.0 \ #watts-txPower 2.0 \ #watts-sleepPower 0.001 \ #watts-transitionPower 0.2 \ #watts-transitionTime 0.005 \ #seconds-initialEnergy $opt(initialenergy) #joules


Examples:

/tcl/ex/wireless-newnode-energy.tcl

http://www.isi.edu/ilense/software/smac/MyTest.tcl

Trace:

[energy 979.917000 ei 20.074 es 0.000 et 0.003 er 0.006]


[energy 979.917000 ei 20.074 es 0.000 et 0.003 er 0.006]

energy: total remaining energy

ei: energy consumption in IDLE state

es: energy consumption in SLEEP state

et: energy consumed in transmitting packets

er: energy consumed in receiving packets

Wireless Script StructureWireless Script Structure

# parameters and options# parameters and optionsset ns [new Simulator]set ns [new Simulator]# [Turn on tracing]# [Turn on tracing]# create # create MobileNodeMobileNode object (PHY to layer 3 object (PHY to layer 3

configured) configured) # Create topology# Create topology


# Create topology# Create topology# create mobility# create mobility# Create Layer 4 and above# Create Layer 4 and above# # -- UDP/TCP agentsUDP/TCP agents# # -- application and/or setup traffic sourcesapplication and/or setup traffic sources# Post# Post--processing proceduresprocessing procedures# Start simulation# Start simulation

SingleSingle--hop hop

Simulation ScenarioSimulation Scenario


See ex4.tcl..

ExerciseExercise

Run the script ex4.tcl for different number

of contending stations.

1. How does the throughput change?

2. What happens by activating the


What happens by activating the

RTS/CTS mechanism?

3. What happens if we reduce the

CWmin/CWmax values?

MultiMulti--hop hop

Simulation ScenarioSimulation Scenario

240m

8 11

13 14

11


4 7

8 11

2 3

See ex5.tcl..

ExerciseExercise

Run the script ex5.tcl for different number

of contending stations.

1. How does the throughput change?

2. Which traffic flows are active in the


Which traffic flows are active in the

network?

3. What happens by activating RTS/CTS?

4. What happens by reducing the node

distance?

Date post:	21-Nov-2015
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NS-2 Wireless 802.11 WLAN

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