[Ns-developers] wireless PHY project

[Anders L Nilsson]

Hi all,

I had a look at the wireless PHY wiki again:
http://www.nsnam.org/wiki/index.php/Ns3WirelessPhy

I have a problem with the following section: "Be aware that the
current Shadowing
model implemented in ns-2.xx implements a Shadowing model which is time-varying,
 i.e. at every signal(packet9 reception the Shadowing formula is
applied. This means
that every packet will see different path loss. This is not true. In
reality, the shadowing is static. After generating the path losses,
they should be constant during the simulation."

Actually, in reality, shadowing is never constant. Even when the two
communicating nodes are stationary, the environment is constantly
changing, cars are moving, people are walking by, trees are waving,
windows and doors opens and closes etc. Path loss and shadowing are
not the same thing. Maybe if you are somewhere out in deep
interstellar space, you will see no shadowing. But I believe at least
90% of the users of NS3 will want to simulate at least a semi-urban
environment.
As a simple test you could turn on your laptop, connect it to an
access point, sit still and monitor the rx signal strength, and you
will see that it varies a few dB even if you are not moving an inch.

So what I am saying is that the path loss do vary with every packet
reception, and this variation should be a configurable parameter
depending on the type of (urban) environment you are simulating.

regards,
Anders

On 11/15/06, annalisa <demarco at fit.ac.jp> wrote:
>
> Have you ever used this package?
>
> http://www.comp.nus.edu.sg/~wuxiucha/research/reactive/release/wireless_transmission_error.tar.gz
>
> It seems to include most of our dilemma about interference and fading
> modelling.
> I took a look at the code, and I' am not sure if the implementor decrease
> the interfence
> amount one the interering packet ceases transmission.
> However, in ns-3 have these solutions been implemented?
> Regards
> Giuseppe De Marco
> FIT, JAPAN
>
>
> Mathieu Lacage wrote:
> >
> > Hi all,
> >
> > The ns-3 project is the opportunity a lot of people had been waiting for
> > to get world-class wireless simulation support. This support will depend
> > largely on the PHY-level layer provided by ns-3. As such, I would like
> > to start the "ns-3 wireless PHY" project whose aim is to build a set of
> > PHY-level models for wireless mediums able to accomodate the needs of a
> > broad spectrum of users:
> >   - 802.11a/b/g
> >   - bluetooth
> >   - GSM/UMTS/EDGE/GPRS
> >   - satellite
> >   - wimax
> >   - your favorite wireless system
> >
> > It is quite obvious that no single model will be able to catch
> > accurately the characteristics of each of these transmission system
> > which is why I think it is important we provide a set of different
> > models and a single interface to access all these models to be able to
> > switch easily from one model to the other, thus allowing model
> > comparison.
> >
> > Because I have a little bit of experience with 802.11 PHY models, I have
> > started adding content to the following wiki page
> > (http://www.nsnam.org/wiki/index.php/Ns3WirelessPhy). It would be
> > awesome if others could start to do any of:
> >   - add descriptions of other wireless systems they would like to
> > modelize
> >   - add descriptions of models they would like to add
> >   - start discussions on the ns-developers mailing-list
> >
> > Idealy, the outcome of this project would be:
> >   1) a single interface to send and receive packets but also to sense
> > the status of the wireless medium
> >   2) multiple implementations of this interface
> >   3) documentation detailing the model behind each implementation
> >   4) documentation detailing "current best practice": when and where the
> > models should be used
> >
> > So far, I think that we should focus on 3) and 4): implementations
> > should not be too hard to come up with once we have gathered enough
> > requirements and model descriptions.
> >
> > Mathieu
> >
> >
> >
>
> --
> View this message in context: http://www.nabble.com/wireless-PHY-project-tf2502315.html#a7352145
> Sent from the ns-developers mailing list archive at Nabble.com.
>
>