Hi everyone,
I am quite new to the TinyOS and I don't understand how CSMA works during
the simulation of Tossim. I found documentation described that that "By
default, the MAC object is configured to act like the standard TinyOS 2.0
CC2420 stack". So, I check the file ./tos/chips/cc2420/csma/CC2420CsmaP.nc
and add a "dbg" statement into command RadioBackoff.setInitialBackoff,
RadioBackoff.setCongestionBackoff, etc. to see when back off happens.
However, it doesn't work as I expected. There nothing happens at all. (I
tried to make the file contain syntax errors, but I still can compile my
tinyos program using make micaz sim, so I guess the sim does not use
CC2420CsmaP.nc. So what file is used?)
I tried simulating with 10 nodes with all-to-all topology and have them
broadcast message at the same time and all of them can successfully send the
broadcast message. I also tried to have nodes send the message at 1-100 us
time difference but still, I did not see they sense the carrier before
sending at all. What I observed is that sending is always succeed (send
immediately when it is asked to send without sensing if others are sending).
To what I understood.
1. The Tossim simulates packet loss, packet collision, hidden channel as
shown in the ./apps/tests/TestSimComm.
2. The Tossim simulates sending delay but does not simulate receiving delay.
I experimented this by having one node broadcasting in all-to-all topology.
I saw that all other nodes received the message at application level exactly
at the same time.
3. The Tossim does not simulate transmission propagation delay, which I
agree with that because it is so small so that it is neglectable.
Question
1. Did I understood correctly on when I mentioned above
2. How could I observe CSMA behavior in Tossim? Is there any easy way e.g.
put t.addChannel("AM", sys.stdout)
3. How to enable Tossim to simulate CSMA behavior?
Thank you so much for reading this long email.
Regards,
Ake
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