Different topology with the same example(the only difference is the routing protocol-AODV,DSR,OLSR)

[Teo Iliadis]

Hello , 

I am using omnet++ 4.4 and inet framework 2.2.0 . I am testing the example net80211_control. I am running the example and the only parametre that I am changing is the routing protocol (AODV,DSR,OLSR etc). The topology with AODV routing protocol is different from the topology when I choose the other protocols. Why does that happen?? I've attached the .ini file and two pictures with the topologies but i am not sure if therei is a parametre in the ini file that affects the topology. Should I find the cause into another file?

Please give me some help. Thanks in advance.

Kindest Regards, 

Teo  

[Michael Kirsche]

Those examples use StationaryMobility.
In this module, initial node positions are "drawn" from a uniform distribution (default(uniform(this.constraintAreaMinX, this.constraintAreaMaxX));).
Different configurations run with a different start seed, depending on the chosen random number generator (RNG). That's why different configurations have different layouts.
If you want the same layout, you should manually adjust the node positions or adjust the choice of the random number generators.

In the omnetpp.ini you see a line num-rngs = 2, that specifies that two RNGs are provided and used in your simulation.
It seems like the AODV example uses a different RNG for the placement of nodes than all the other nodes.

You can specify that all mobility modules of all nodes use always the same random number generator (and thus the same start value if you always use the same run number).

So try to add this line:

**.mobility.rng-0 = 1

It tells OMNeT that the mobility module should use the first random number generator. The node placement should then be identical for all examples as they will now use the same RNG and the same generated numbers to calculate node placements.

[Teo Iliadis]

Thank you very much Michael for your help !! I 've tested it and it worked !!! 

One more question if you know. If i am gonna try to change the mobility with mass mobillity or random walk, will I have any problem with this parameter of mobility.rng ?? 

Thanks again for your help !!

Kindest regards

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[Michael Kirsche]

By "any problem" you mean the node positions?
I honestly don't know... take a look at the code! If node positions are also initialized from a distribution like in StaticMobility you probably need to adjust the RNG again. Same goes for any other RNG distribution that might be used in the code of the other mobility models (for example for movement modeling).

Simply try it out and observe and always take a look inside the code!

[Teo Iliadis]

I will make some tests and I will let you know if you want !! 

thanks again Micheal

[Alfonso Ariza Quintana]

the problem is the random generator, the position of the nodes is selected randomly and the different protocols don't use the same number of random numbers, this provokes that the random sequence used to generate the position of the nodes is different en every one of the simulations

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Date: Wed, 27 Aug 2014 03:46:41 -0700
From: teoi...@gmail.com
To: omn...@googlegroups.com
Subject: [Omnetpp-l] Different topology with the same example(the only difference is the routing protocol-AODV,DSR,OLSR)

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[Teo Iliadis]

Thanks Alfonso for your answer and your time! 

I managed to have a stable topology for all the protocols with the line **mobility.rng-0 = 1 that Michael suugested. 

So, these generetors give different random numbers using the same RNG class - MersenneTwister as distribution class? Am I wrong?

Regards

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[Alfonso Ariza Quintana]

Whit the same initial seed the sequence is the same, but, by default the same random number generator is used by all modules. If you change a module that uses, for example 3 calls to the random protocol of other that uses only 1 the sequence will change in the rest of the modules except

[Teo Iliadis]

I got it !! thank you very much Mr.Alfonso!