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1527 Accelerating Wireless Simulations Using Scalability Techniques

Lab Manual for Session 1527: Accelerating Wireless

Simulations Using Scalability Techniques

Lab 1: Using a ast !n"ironment

The purpose of this lab is to introduce you to the network model used throughout this session and to

illustrate the speed difference between the development and execution environments.

A simple radio node model is provided (1527_base). t includes a packet generator and a sink! both

of which maintain statistics on the number of packets generated"received and the time of

generation"reception. There is no explicit antenna module! which will cause the simulation to act asif an isotropic antenna was present.

The movemodule contains a process model that will randomly move the node by an average of #$

meters in latitude and longitude every %$$ seconds.

The min frequencyattributes for the transmitter and receiver channels are promoted. They will be

specified in derived node models.

CONFIDENTIAL INFORMATION: DO NOT DISCLOSE, FORWARD, DISTRIBUTE, SHARE, OR MAKE COPIES OF THIS DOCUMENT IN WHOLE OR IN PART. Copyrigh !""# OPNET T$%h&o'ogi$(, I&%.

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Three such derived node models (1527_30Mhz! 1527_60Mhz! and 1527_90Mhz) have been createdwith! respectively! minimum fre&uencies of '$! $! and $ *+,. The channel bandwidth is set to

-#*+,. n this way! there is no fre&uency overlap among the derived node models.

ach node broadcasts %$$$/byte packets at the rate of $ packets per hour! randomly distributed in

time.

Baseline: development environment

%. 0tart Modelerby double/clicking on the *odeler icon on the desktop. The 123T *odeler

%%.$ application launches and displays its splash screen.

-. 1pen the 1527pro4ect as follows

a. 0elect the File" !en"menu. The !endialog box appears with a Model direc#ories$tree

on the left and a list of files on the right.

b. 5ouble/click on 1527to open the pro4ect.

6ou should see a colorful scenario named 'fre& with a scattering of red cell phones! antennas!

and humvee icons! representing the three kinds of derived node models.

'. 2ress %#rl&'hif#&(to run the simulation with the current settings.


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The 0imulation 0e&uence dialog box will eventually show you the simulation progress and thespeed of the simulation (your actual speed will depend on the hardware).

7. 1nce the simulation completes! write down the following information8

a. Total number of events899999999999999999999999

b. Average 0peed8999999999999999999999999999999events"sec

c. :urrent 0peed8999999999999999999999999999999events"sec

d. lapsed Time89999999999999min.999999999999999sec.

#. :lose the dialog box when you are done reviewing it. 6ou can view the speed of your simulation

by selecting 50 " 1pen 50 ;og to launch the log browser.


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and clicking under *essage to display the log entry

. :lose the ;og ntry $ and the ;og

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Switching to a faster production environment

Optimized Kernel

>. :lick on the %onfi)ure*(un +iscre#e ,ven# 'imula#ionbutton ( ) in the -ro.ec# ,di#or.The %onfi)ure*(un +,'dialog box appears.

:urrently the simulation se&uence is set to force the kernel type to development! regardless of

the setting of the kernel_typepreference. ;et=s switch to forcing the kernel to optimi,ed.

?. :lick on the 'imula#ion /ernel$popup and change the value to !#imized

. :lick on the ,ecu#ion* dvanced* %om!ila#ionvertical tab to show the various compilationoptions.


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%$. 0et the nclude func#ion s#ac #race informa#ion in recom!iled models to4o. This ise&uivalent to changing the comp_trace_infopreference to @A;0! but only for this

simulation without affecting the environment database or other simulations.

%%. :lick on (unto start the simulation.

%-. 1nce the simulation completes! review the speed information.





%'. :lose the simulation dialog box. 6ou can also open the 50 log to review the speed information

3ote that because of the short simulation duration! the average speed is not yet a goodrepresentation of the simulation speed. As you can see in the 0imulation 0peed graph! the

:urrent 0peed graph has reached a fairly steady rate while the Average 0peed graph is movingtowards that asymptotic value. The longer you run the simulation! the closer the Average will beto the :urrent value.

%7. :lose the simulation dialog box. 6ou can also open the 50 log to review the speed information

%#. ;eave the pro4ect open. 6ou will continue to use it in the next lab.

n this case the speed difference is actually not that great. 0ome simulations can run more than twice

as fast using the optimi,ed settings.

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time that is spent in the simulation (copying packets! going through the pipeline stage architecture) isreally spent in portions of the simulation kernels that are about the same speed in both versions.

The more complex your models! the higher the speed difference you are likely to encounter. @or

example! the following are some speed figures using standard models.

The second value (TB"@A;0) denotes the value of the comp9trace9info preference.

#onclusion

6ou have seen how to switch between a production (fast) and a development (less fast) environment

Bse the latter while you are developing or debugging your models! use the former once the modelsare deemed complete and you are gathering simulation data.

!$% & LA' 1


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Lab 2: %ynamically (e)ucing (ecei"er *rou+s

n this lab! you are going to compare the speed of a wireless simulation using different versions of

the closure and channel match pipeline stages.

n the previous lab you ran the simulation in development and optimi,ed mode! but what was this

simulation really doingC

ach node was broadcasting %$$$/byte packets $ times per hour! randomly distributed in time.

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f. 0elect File" 'ave s"

g. :hange the File name$to lab2_dra_chanma#ch

h. 0croll the Model direc#ories$tree display to the top

i. 0elect the o!_modelsdirectory to indicate where the file should be saved (by default it is

saved where the original was located)

4. :lick on 'ave

-. *odify the local copy

a. :hange the function name from dra_chanma#ch_m#to lab2_dra_chanma#ch_m#

(The 9mt suffix indicates that the pipeline stage can be executed in parallel using a parallelkernel. t has no effect in a se&uential execution.)

b. ;ook for the code testing for non/overlapping bands and update it as follows (add the boldtext)

if ((tx_freq > rx_freq + rx_bw) || (tx_freq + tx_bw < rx_freq)){Objid tx_ch_objid, rx_ch_objid;op_td_set_int (pkptr, O!_"#$_%$_&$"!'_"$", O!_"#$_%$_&$"!'_*O%-)./* Get the transmitter and receiver channels object ID from packets D! *tx_ch_objid " op_td_#et_int $pkptr, O%&_D!_'!_(_&)_O+ID;rx_ch_objid " op_td_#et_int $pkptr, O%&_D!_'!_'(_&)_O+ID;/* 'emove the receiver channel from the transmitter channel rx#ro-p */op_radio_txch_rxch_remove $tx_ch_objid, rx_ch_objid;/O"

0

f the fre&uency bands do not overlap! remove the receiver channel from the transmitter=sreceiver group. The change takes effect once the current transmission is over.

'. 0ave the modified code

7. :ompile the pipeline stage with the corresponding toolbar button ( ). This should display acompilation status dialog box

a. f the compilation fails! review the code changes mentioned above and repeat the

compilation.


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b. 1nce the compilation succeeds! close the compilation status dialog box and thelab-9dra9chanmatch.ps.c notepad.

#. *ake the 2ro4ect editor active by clicking on it

. 5ouble/click on one of the mobile nodes to open the associated node model

>. *odify the channel match pipeline stage

a. ight/click on the ra_#radio transmitter module and select ,di# ##ribu#es


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b. :lick on the value of the chanma#ch modelattribute to bring up a popup of possible pipelinestages.

c. 0elect lab2_dra_chanma#ch.

d. :lick /to accept the attribute change

e. 0elect File" 'aveto save the attribute change and close the node editor.

?. eturn to the %#-> pro4ect window.

. 6ou could 4ust run the simulation again! but you are going to use a different scenario to be ableto compare some statistic between executions.

%$. 0elect 'cenarios" +u!lica#e 'cenario"

%%. 0et the 'cenario nameto chanma#ch


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%-. :lick 1D

%'. 2ress %#rl&'hif#&(to run the simulation for the new scenario

%7. 1nce the simulation completes! write down the following information8





%#. :lose the dialog box when you are done reviewing it. 6ou can also see the 50 log to review thespeed information.


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%. 0elect +,'" (esul#s" %om!are '#a#is#ics"


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%>. :lick on Elobal T 5elay (msec) under the Elobal 0tatistics area.

%?. *ake sure that the pop ups are set to 1verlaid 0tatistics! All 0cenarios! and As s! then click

0how


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The two graphs are exactly identical! which is why you don=t see a red graph. 6ou can check theother statistics if you want (by selecting 0tacked 0tatistics).

%. :lose the %om!are (esul#sdialog box

-$. :lose the Elobal T 5elay (msec) graph (and any other statistics you might have displayed).

Fhen asked to hide or delete the graph! click on +ele#e

0peedwise! things are a bit better! aren=t theyC 3ow a transmitter channel only tries all channelsonce. After that! subse&uent transmissions from that channel will have a receiver group only

containing receiver channels with matching fre&uency.

:an this dynamic receiver group trimming be used elsewhereC :ertainly. Fhat happens before the

channel matchC The closure stage! where the simulation figures out if a signal can actually reach thereceiver channel. 0o you could do 4ust the same as for the channel match. f the closure stage fails!

remove the receiver channel from the receiver group of the transmitter channel.

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Lab ,: #aching -ith a -ireless )omain

n this lab you are going to use a Fireless 5omain model to further reduce the amount of work

performed by the simulation.

The various mobile nodes are changing their positions every %$$ seconds! and broadcasting

messages an average of once a minute. 0o this means that typically a node will communicate -times with matching ob4ects between moves.

@urthermore the moves are not that big! representing humans walking around (folks moving at about

#$ meters in latitude and longitude per %$$ seconds in not too friendly terrain). 0o the closure!

power loss! and propagation delay computations between two positions are likely to be &uite similar.

ventually nodes will have moved enough that data needs to be recomputed.

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. :lick /to overwrite the incomplete model.

>. 3ow skip to Using a wireless domain instance to speed things up


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Defining the Wireless Domain model

%. 0elect File" !en

-. :hange the File of #y!e$popup to ;ireless +omain Model(last entry in the menu)

'. 5ouble/click on :d1527

This wireless domain model is partly defined. 6ou are going to implement three of the re&uired

callbacks.

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7. :lick on the +efine"button to open the Model ##ribu#esdialog box

#. 1ne attribute (Mobile Model) is defined. *ake sure it is selected and click on the ,di#-ro!er#iesbutton

ach wireless domain instance will only cache information for a specific node model! since we

know that the models have non/overlapping fre&uency bands.

. :lick %anceltwice to close the Attribute and *odel Attributes dialog boxes without changing

their contents.


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>. :lick on the ,di# ;ireless +omain

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. 3ow click on ,di# ;ireless +omain ni# %allbac( ) toolbar button

This callback has already been written. t performs the following tasks8

a. terate through the mobile nodes looking for the ones with the matching model! setting up the

:ireless domainattribute on the transmitter and receiver channels

b. Allocate the domain state (the sparse array) and set up the arrays of pointers for theappropriate channel 5s

%$. :lose the editor when you are done reviewing the init callback.

The membership! info get! and info set callbacks remain to be defined.

o The membership callback is invoked by the simulation kernel when a transmission starts tocheck if a given transmitter"receiver module is considered part of the wireless domain area of

coverage! and if so to obtain an appropriate cluster id (the wireless domain model defineswhat=s a cluster id).

o The info get callback is invoked by the kernel before the closure pipeline stage. This allows

the wireless domain to retrieve any available values from its cache to skip pipeline stage

invocations.


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%-. nfo Eet :allback

a. :lick on the ,di# ;ireless +omain nfo >e# %allbac( ) toolbar button

Eiven a transmitter (xmit9cluster9id) and a receiver (rcvr9cluster9id)! this callback is

responsible for figuring out if there is some cached data and if so to return that cached data to

the kernel.

n this example! it means

i. Bse the transmitter 5 as an index in the first dimension of the -5 sparsearray.

ii. Bse the receiver 5 as an index in the second dimension of the -5 sparse

array for the transmitter 5 entry

iii. :heck if the array element is 12:93; (not cached) or an actual dataelement. f the latter! copy that data element into the kernel/provided info9ptr

argument.

The callback also provides a continuation9ptr argument that can be used to store a reference

to some cache data structure for faster access in a subse&uent info set callback. n thisexample! we are going to use the continuation9ptr to store the address of the -5 sparse array


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cell that was found to contain an 12:93; element! so that the info set callback can createthat element.

b. Bncomment the code between lines %#/%> and -#/7> by deleting the 7if 8and 7endif

statements.

c. :ode review the changes.

d. 0elect File" 'aveto close the editor and apply the changes.

%'. nfo 0et :allback

a. :lick on the ,di# ;ireless +omain nfo 'e# %allbac( ) toolbar button

This callback is invoked by the simulation kernel after each appropriate pipeline stage of aradio transmission @ a cache getcallback was invoked and some data was not present.

n this case! initially no data is cached. 0o the first time a transmission is attempted between

a transmitter channel and a receiver channel! the cache getwill return 12:93;! and the 7

pipeline stage invocations for the transmission between the channels will cause info setcallbacks. ;ater transmissions will get the cached data.


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0o what needs to be done is

i. :heck if there is already a caching element.

ii. f not! create one

iii. Bpdate the caching element with the data provided by the simulation kernel.

b. Bncomment the code between lines %7/%# and -#/7# by deleting the 7if 8and 7endif

statements.

c. :ode review the changes.

d. 0elect File" 'aveto save the changes to close the editor and apply the changes.

%7. :ompile the now complete model using the %om!ile ;ireless +omain Model ( ) toolbar

button.

%#. :lose the compilation status dialog box and the Fireless 5omain *odel.

Using a wireless domain instance to speed things up

%. *ake the 1527pro4ect active

-. 0elect 'cenarios" +u!lica#e 'cenario"

'. 0et the new scenario name to 1:d

7. 1pen the b.ec# -ale##e( )

#. 0elect the :d1527wireless domain ob4ect in the ob4ect palette

. :lick anywhere in the 2ro4ect area and drag to define a rectangle.

>. :lick again to complete the rectangle. 1nce the definition is complete the rectangle switches to

a blue outline. ight click to end the operation.

f the wireless domain were physically/based! the rectangle would be used to define the

geographic area of interest. 9'$*+, node model (default value of the *obile *odel

attribute of the model).?. +it %#rl&'hif#&(to run the simulation

. 1nce the simulation completes! write down the following information8






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+ow does this compare with the information obtained at the end of ;ab -C

%$. :lose the dialog box when you are done reviewing it. 6ou can also open the 50 log to see the

speed information.

%%. As for ;ab -! select +,'" (esul#s" %om!are '#a#is#ics"

%-. :hoose Elobal Throughput (bits"sec) and click 0how

%'. Things look &uite similar! but there is a difference. f you ,oom in the area shown above! here is

the difference8


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Fhy some differenceC emember that each node moves a little bit every now and then. The

wireless domain caches the information generated from the first transmission between twonodes. f the nodes= closure was feasible at the time of the first transmission any latter

transmissions will use that same data.

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a. ight click on the blue rectangle (that can be tricky. 1ne easier way is to right/click on anob4ect that overlaps the rectangle. This will bring up a menu showing the various elements

where the cursor clicked! including the wireless domain ob4ect.)

b. n the ##ribu#esdialog box! click on the Mobile Modelattribute ?alueto change the

default %#->9'$*+, to 1527_60M

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#. :lose the dialog box when you are done reviewing it. 6ou can also open the 50 log to reviewthe results.

#onclusion

n this lab you have been introduced to the potential of wireless domains. They provide a convenient

mechanism to cache some transmission information so that the simulation kernel can perform

transmissions faster.

Fireless domains are useful if some of the transmission pipeline stages involve complex

computations that are not likely to change much if any between transmissions. The idea is to tradespace (the cache) for time (the computation) to allow faster simulations.

1527_labmanual_opnk2004

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