Simulator Pres

8/4/2019 Simulator Pres

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Simulators for Sensor

Networks

Sagnik Bhattacharya

9/12/2001


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How much effort should we

put in?

Build battery and wireless models?

(Preferably no) Implement routing?

How much learning is involved?

Change basic modules or just add our ownmodules?

-A computer scientist is someone who fixes things that aren't

broken.


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GlomoSim

Specific for mobile wireless networks.

Built as a set of libraries. The libraries are

built in Parsec( a C-based discrete eventsimulation language).

Layered architecture with easy plug-in

capability.

-Any program that runs right is obsolete.


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Propagation

model

Radio

MAC Layer

Network

IP

Transport

Application

Link Layer

GloMoSim LibraryGloMoSim Library

Modular, extensible library for

network models

Model each layer using abstract

ordetailed model

Built-in statistics collection ateach layer

Cons :

Fixed protocol layers.

Application Processing

Free space, TIREM

EPLRS, WaveLAN, ...

IEEE 802.11, 802.3,

OSPF,AODV,

IP

TCP, UDP, RSVP

RTP Wrapper

Packet Store/Forward

Data Plane

-Windows is NOT a virus. Viruses DO something.


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NS - 2

De facto standard for network simulations Discrete Event Simulator

Packet-level

Wired and Wireless Size : (Current release adds around 10%) 100K lines of C++

70K lines of OTcl

30K lines of test suites 20K lines of documentation

-A program is never finished until the programmer dies.


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NS Architecture

Object-oriented (C++, OTcl)

Scalability + Extensibility

Control/data separation

Split C++/OTcl object

Modular approach

Fine-grained object composition

Reusability

-You are making progress if each mistake is a new one.


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C++ and OTcl Separation

C++ for data Per packet action

OTcl for control Periodic or triggered action

+ Compromise between composibility and

speed Learning and debugging

-To err is human, but to really foul things up requires a computer.


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OTcl and C++: The Duality

C++ OTcl

Pure C++objects

Pure OTclobjects

C++/OTcl split objects

ns

-There were computers in Biblical times. Eve had an Apple.


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SensorSim

Extension to NS - 2.

Provides battery models, radio

propagation models and sensor channelmodels.

Provides a lightweight protocol stack.

Has support for hybrid simulation. To be integrated with NS - 2.

-There can never be a computer language in which you cannotwrite a bad program.


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SensorSim Architecture

monitor and controlhybrid network

(local or remote)

Simulation Machine

Gateway Machine

ns

modified event scheduler

VR

V

VV

GUIapp

app

R

real sensor apps on

virtual sensor nodes

gateway

socket

comm

serial

comm

HS InterfaceEthernet RS232

Proxies for real

sensor nodes

GUI Interface

app


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Sensor Node Model in SensorSim

Node Function Model

Network Layer

Micro Sensor Node

Applications

Power Model(Energy Consumers and Providers)

Battery

Model

Radio Model

CPU Model

Sensor #1 Model

Sensor #2 Model

MAC Layer

Physical Layer

Sensor Layer

Wireless Channel Sensor Channel

Network

Protocol Stack

Sensor

Protocol Stack

Middleware

Physical Layer

State

Change

Status

Check

-There are two ways to write error-free programs; only the thirdone works.


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Power Management Model

Transmit Receive

Off

Idle

BZR event

BZR event

BZR event

receive

done

transmit

transmit

done

Without Power Management

Transmit Receive

Sleep

Off

Idletransmit

timeout(3 sec)

BZR event

BZR event

transmit

transmit

done

BZR event

receive

done

receivetimeout

With Power Management

-The program is absolutely right; therefore the computer must be

wrong.


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SensorSim Problems

Still at pre-release stage.

No Documentation.

The software currently has a very specificapplication hard-coded.

It caters to only one base station.

-The definition of an upgrade: Take old bugs out, put new ones in.


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NS-2 primer

-Reference Manual: Object that raises the monitor to eye level.

Also used to compensate for that short table leg.


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Hello World - Interactive

Mode % ns% set ns [new Simulator]

_o3

% $ns at 1 puts \Hello World!\1

% $ns at 1.5 exit

2

% $ns runHello World!

72%

-One person's error is another person's data.


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Hello World - Batch Mode

simple.tclset ns [new Simulator]

$ns at 1 puts \Hello World!\$ns at 1.5 exit

$ns run

74% ns simple.tcl

Hello World!

75%

-Maintenance-free: When it breaks, it can't be fixed...


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Basic tclset a 43

set b 27

proc test { a b } {

set c [expr $a + $b]

set d [expr [expr $a - $b] * $c]for {set k 0} {$k < 10} {incr k} {

if {$k < 5} {

puts k < 5, pow = [expr pow($d, $k)]

} else {

puts k >= 5, mod = [expr $d % $k]}

}

}

test 43 27 -MACINTOSH stands for Most Applications Crash If Not TheOperating System Hangs.


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Basic OTclClass Mom

Mom instproc greet {} {

$selfinstvar age_

puts $age_ years old

mom: How are youdoing?

}

Class Kid -superclass Mom

Kid instproc greet {} {$selfinstvar age_

puts $age_ years oldkid: Whats up, dude?

}

set mom [new Mom]

$mom set age_ 45

set kid [new Kid]

$kid set age_ 15

$mom greet

$kid greet

-It works! Now if only I could remember what I did...


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Elements of ns-2

Create the event scheduler

[Turn on tracing]

Create network Setup routing

Create transport connection

Create traffic / Schedule events

Transmit application-level data

Start simulation

-It is easier to write an incorrect program than understand a

correct one.


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Wireless simulation in NS-2

Very different from wired simulation.

Central object called GOD(General

Operations Director) contains global stateinformation.

Nodes are inherently mobile.

-I finally made my stupid computer faster; I dropped it out of the

window, and it went really fast.


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An Example Step 1

# Define Global Variables

# create simulator

set ns [new Simulator]

# define traces

set tracefd [open simple.tr w]

$ns_ trace-all $tracefd

# create a topology in a 100m x 100m area

set topo [new Topography]

$topo load_flatgrid 100 100

-If at first you don't succeed, call it version 1.0.


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An Example Step 2

# Create God

create-god $val(nn)

# Create channel

set chan_1_ [new $val(chan)]

-For any problem there is a solution that is simple, quick, and

ultimately worse than the problem.


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An Example Step 3$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) \-channel $chan_1_ \

-topoInstance $topo \

-agentTrace ON \

-routerTrace ON \

-macTrace OFF \

-movementTrace OFF \-energyModel "EnergyModel" \

-initialEnergy $val(initialenergy) \

-rxPower $val(receivepower) \

-txPower $val(transmitpower) \

-idlePower $val(idlepower)

-Excuse me for butting in, but I'm interrupt-driven.


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An Example Step 4

# Generating nodes

for {set i 0} {$i < $val(nn) } {incr i} {

set node_($i) [$ns_ node]

}

# Provide initial (X,Y, for now Z=0) co-ordinatesfor mobilenodes

$node_(0) set X_ 94.85

$node_(0) set Y_ 12.75$node_(0) set Z_ 0.0

$node_(1) set X_ 60.79

:

:

-Computers can figure out all kinds of problems, except the thingsin the world that just don't add up.


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An Example Step 5

#Create two ping agents and attach themto the nodes n0 and n2

set p0 [new Agent/Ping]

$ns attach-agent $n0 $p0

set p1 [new Agent/Ping]

$ns attach-agent $n2 $p1

#Connect the two agents

$ns connect $p0 $p1

-Computer Science is no more about computers than astronomy is

about telescopes.

E. W. Dijkstra


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An Example Step 6

#Schedule events

$ns_ at 100.0 "puts \"hell-O\" "

$ns_ at 10.2 "$p0 send"

$ns_ at 10.4 "$p1 send":

:

#Run the Simulationputs "Starting Simulation..."

$ns_ run

-Build a system that even a fool can use, and only a fool will use

it.


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Ping Protocol

Check out the handout.

To add a new protocol :

Define packet header (PT_PING)

Define new agent class as a subclass ofAgent in header file (ping.h)

Implement at least the following functions: int command ( int argc, const char*const* argc)

void recv ( Packet * pkt, Handler* h)

-To err is human, but to really foul things up requires a computer.


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NS - 2 (contd.)

Cons : Comparatively difficult to learn and use.

Supposedly more useful for getting statisticsfor lower level protocols.

Originally built for wired networks, laterextended for wireless.

Supposedly, does not work well for largetopologies.

-To err is human--and to blame it on a computer is even more so.


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NS-2 problems and

workarounds Large memory footprint

100 nodes 23MB

1000 nodes 412 MB Solutions :

Turn off tracing

-routerTrace OFF \-macTrace OFF \ Remove packet headers

remove-all-packet-headers

add-packet-header DSDV-Bug? That's not a bug, that's a feature.


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Scalability of NS-2

Maximum number of nodes dependsupon the traffic.

Should be able to up to 500 nodes withreasonable(?) traffic.

Running time?

-Every time I type 'win', I loose ...


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To use NS..

Dont worry about Otcl. Its easy..

Forget about Nam traces.

Join the ns-usermailing list. Get started as soon as possible. learning to

use and modify it can take time.

Just adding new protocols might not do. Someinternal changes might need to be made.

-A user friendly computer first requires a friendly user.


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Conclusion

Use SensorSim if you can.

NS-2 can be used for simulation of the

order of hundreds of nodes. Notpossible with motes.

Can build more advanced protocols, for

future motes which might have morememory.

-ASCII stupid question, get a stupid ANSI!


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URLs

This presentation:

http://www.cs.virginia.edu/~sb2jb/rese

arch/ns

NS-2 home:

http://www.isi.edu/nsnam/ns

-Every bug you find is the last one.


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Questions?

-Computer Science: solving today's problems tomorrow.

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