[e2e] Simulator for wireless network

[Eric W Anderson]

At the risk of flogging a dead horse, here are a few observations.
Right now, my group is working on studying the physical- and MAC-layer
impact of using steerable antennas in 802.11-ish networks.   We've
used ns2 and Opnet a fair bit, and right now we're measuring actual
deployments.  With that said here are my thoughts:

(1) RF propagation is extremely sensitive to the details of a physical
environment.  If you do your research using the "40 laptops" approach,
it's important to consider an appropriate range of physical
environments.  If you use a simulator, you need to consider what sort of
physical world you're specifying -- or implicitly assuming.

(2) Both Opnet and ns2 make significant simplifying assumptions about
the RF environment and the sender and receiver hardware.  Whether
these assumptions are OK or not depends very much on what you're
studying.

(3) Opnet's main strengths -- to me -- are its extensive library of
equipment models and its built-in statistics gathering.  Both are
handiest if you're a network administrator and want to quickly evaluate
a proposed deployment of stock systems and protocols.  If you're
interested in re-designing things significantly, they're probably less
useful.  In my experience, the built-in statistics tracking proved
inappropriate for the fine granularity data I needed to gather.

(4) Parts of Opnet are modifiable models which come with the source
code, and other parts are opaque and immutable.  The parts I most wanted
to change or instrument were often in the latter category.

In the end, we've settled on actually implementing things as our
preferred approach.  I'll probably use ns2 in the future when an actual
deployment is impractical.  I probably won't be using Opnet again.

That's my two cents' worth,
Eric



Thus spake Durga Prasad Pandey (dpsmiles at MIT.EDU):

> What would be considered the best network simulator(s) for wireless  
> networks, particularly for TCP experiments?
> 
> Durga

-- 
Eric W. Anderson                                   University of Colorado
eric.anderson at colorado.edu                      Dept. of Computer Science
phone: +1-720-984-8864                             Systems Lab - ECCS 112

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