Dr. Levis, Thanks for your answer! I got the point.
In that case, I guess "nxle_uint16_t crc" inside the tossim_footer struct in TossimRadioMsg.h is not useful here. For crc will always be correct (and no need to be checked) in the simulation for all the received packets (that pass the SNR-based model). Or crc is actually reserved for other use? Best, Yi On Thu, May 13, 2010 at 4:13 PM, Philip Levis <[email protected]> wrote: > > On May 10, 2010, at 10:04 PM, Yi Tang wrote: > > Hi All, > > *Does TOSSIM 2.x really flip bits in the packet (according to the > SNR-based packet error model), as it did in TOSSIM 1.x?* > > I see that TOSSIM 2.x decides whether a node can receive a packet based on > the radio model (in CpmModelC.nc), yet it seems that the node will receive a > bit-error-free packet once the simulator decides that it can receive it. > > Please correct me and point me to the relevant source code if I'm wrong. > > > It does not; TOSSIM in 2.x uses an SNR-based packet model. Unlike the > packet models in 1.x, this one handles collisions, external interference, > and the RF capture effect. The major missing piece (and why the results can > be misleading compared to a real network and are insufficient by themselves) > is that signal strength is a constant; in reality it varies over time. > > Phil > -- Yi Tang Laboratory of Secure & HIgh-performance NEtworks (SHINE) Bradley Department of Electrical and Computer Engineering Virginia Tech
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