[Tinyos-devel] Tossim - node receives packet althought sending other

Lumir Honus foldus at gmail.com
Wed Feb 11 02:49:47 PST 2009


Hello,

I'm sending my post also here, as I beleive it is internal bug in tossim.
If not, I apologize in advance.

I found the problem (possibly bug) in CpmModelC (in tossim). I have
simple network topology consisting of 4 nodes.

Node 1 sends packet to 0, the transmit finishes at 107542750616.
Before it is finalized, node 3 sends at 107540209259 a packet to 1.
(node 3 can send because it from his point of view is channel clear =
noise is lower than clear channel threshold)
Node 1 receives packet despite it is still transmitting packet to 0.

As far as I understand radio communication, it is not possible to
receive a packet while sending.
I made a workaround, I have added only loopback reception event with
high power.


If I am wrong, please let me know. In any case, this behavior brings
lot of problem in my application, because other nodes can't snoop traffic,
because of the radio collision.


----------------------------------------------------------------------------------------------------------------------------------------

107522761719:DEBUG (1): Node 1 transmitting to 0, finishes at 107542750616.
DEBUG (1): Enqueing reception event for 3 at 107542750616 with power -80.480000.
DEBUG (3): IN: noise_hash_generation()
DEBUG (1): Enqueing reception event for 2 at 107542750616 with power -79.400000.
DEBUG (2): IN: noise_hash_generation()
DEBUG (1): Enqueing reception event for 0 at 107542750616 with power -86.400000.
DEBUG (0): IN: noise_hash_generation()


107540209259:DEBUG (3): Node 3 transmitting to 1, finishes at 107560198156.
DEBUG (3): Enqueing reception event for 2 at 107560198156 with power -83.930000.
DEBUG (2): IN: noise_hash_generation()
DEBUG (2): Lost packet from 3 to 2 due to SNR being too low (-4)
DEBUG (2): Going to lose packet from 1 with signal -79.400000 as am
receiving a packet from 3 with signal -83.930000
DEBUG (3): Enqueing reception event for 1 at 107560198156 with power -68.060000.
DEBUG (1): IN: noise_hash_generation()
DEBUG (3): Enqueing reception event for 0 at 107560198156 with power -98.800000.
DEBUG (0): IN: noise_hash_generation()
DEBUG (0): Lost packet from 3 to 0 due to SNR being too low (-12)

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S pozdravem
       Lumir Honus


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