Re: [Playerstage-developers] Gazebo Truth

[Richard V. <va...@hr...>]

I'm very interested in what you guys achieve in this direction. For
example, if you come up with a reasonably clean Stage/ns2 interface, let's
talk about how to make this available to everyone. Wei Ye and I did this
with Stage (back when it was called `Arena') and it worked pretty well. We
achieved de-facto syncronisation by slowing down Arena's clock a bit so
ns2 ran just about fast enough. Not pretty, but enough to show that the
parameters of the wireless propagation model had significant effects on
our robots' overall behavior. Wireless is a significant part of a robot's
environment these days, so having decent models would be very useful.
Paper in ICRA'01.

Richard.


On Wed, 5 Nov 2003, john sweeney wrote:

> For research I have been doing, I have modified versions of stage and 
> the ns2 network simulator to run in (some sort of) synchronization. 
> This allows me to use ns to simulate wireless traffic, using its 
> built-in wireless models, but the locations of the wireless nodes come 
> from the locations of the robots, which is controlled by stage.
> 
> It's a pretty big hack, and it's on older versions of stage and ns 
> (1.3.2 and 2.1b9a respectively), and probably wicked overkill for most 
> robotics work, but if there's interest I could put it somewhere for 
> people to look at.
> 
> john
> 
> Nathan M. Farrington wrote:
> > Hi Pranav,
> > 
> > I remember Ben Grocholsky <bp...@gr...> was interested in
> > simulating wifi in Gazebo. Have you talked to him?
> > 
> > Our group is also interested in a wifi simulation. The question is now,
> > to what extent do you want to simulate it? For instance, we are using
> > BBN's ad-hoc network routing software developed by Jason Redi
> > <re...@bb...>. Ideally, we would like to simulate not only the 802.11b
> > radios we are using, but also BBN's ad-hoc networking algorithms.
> > 
> > If you just want to simulate a regular 802.11b (or g) radio, then the
> > task is much simpler, but still tricky depending on what exactly you
> > want. For simulating the signal strength of the radio, you could use an
> > empirical formula based on a model of 2.4GHz communications. For
> > instance, the signal strength has a sharp dip at a distance where
> > multipath reflections off of the ground destructively interfere with the
> > line-of-sight transmission from the transmitter to the receiver. The
> > problem should be more pronounced when there are more objects to reflect
> > off of, especially inside of a tunnel.
> > 
> > An improvement would be to drop packets in proportion to the degradation
> > in signal strength, to the point where robots can no longer communicate
> > with each other! And what about collisions caused by multiple radios in
> > the same area? I'm not an expert in networking or wireless networking
> > like Dr. Redi, but I imagine that wireless network simulation has
> > numerous issues. Anyway, its not an easy problem but I think it would be
> > very useful to lots and lots of people.
> > 
> > Also, we should find out what other wifi simulators are out there and
> > see if we can incorporate any of those efforts into Gazebo.
> > 
> > Regards,
> 
> 
> 
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-- 
Richard Vaughan / HRL Laboratories / va...@hr... / +1 310.317.5689