Thanks for your pointer. In the paper I did see TOSSIM models packet corruptions (Sec. 3), and the simulation in Sec. 4.2 Fig. 9 also shows packet loss due to CRC failures. However I did not see how to distinguish between the causes to CRC failures,
i.e. collision and bit errors. In Sec. 6 you mentioned that RadioCRCPacket as a simulator has been developed which can model packet loss due to bit errors but does not model packet collision. Perhaps in a simulator like TOSSIM we can identify collision since we have global knowledge of which nodes are sending simultaneously (
e.g., the paper Sec. 3.7.2 mentioned something similar to this), but in reality how can a mote itself distinguish these two?
I modified TinyOS MAC layer to pass up packets even if CRC is error. However in experiments I never detected such CRC error, though I can detect packet loss. Is that because the error bits always occur at the start symbol and thus prevent reception?
Regards,
Tie
On 11/11/06, Philip Levis <[EMAIL PROTECTED]> wrote:
On Nov 10, 2006, at 7:14 PM, Tie Luo wrote:
> Thank you for your clarification.
> I think to detect collision in reality becomes difficult, since
> both collisions and channel error lead to packet CRC error. Other
> methods like using RSSI and LQI cannot clearly distinguish either,
> although they may help to some extent.
>
Please read the TOSSIM paper.
Phil
--
Regards,
Tie
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