[Tinyos-help] help:packets cannot be received in lossy model in TOSSIM

[Nikolas]

On 03/06/07, qiting chen <cqt_chaos at yahoo.com.cn> wrote:
> Hi,all
>    I tend to use the lossy model in TOSSIM(tinyos1.15) and met a problem.
>    The problem is that in the lossy model, no packet reception will ever
> occure though I've set the bit error rate to zero.While in simple
> model,packets can be received successfully.
>    To use the lossy model,I've creadted lossy.nss in the app directory.At
> the beginning of the dbg message,it says:
>    SIM: EEPROM system initialized.
>    Initializing lossy model from lossy.nss.
>    0: RFM connectivity graph constructed.
>    However,packets sent can no longer be received as long as the lossy model
> is used.
>    Can anyone help me sovle the problem
>
>    thanks in advance.

First, may I suggest you explore this further by using dbg statements
in the simulator code.
Also check the TOSSIM document: just google nido.pdf.

I can see 2 possibilities:
a) your packets arrive corrupted at the receiver and are subsequently dropped
b) your packets are not sent at all

If a):
Your bit-error-rate in lossy.nss might be too high so all received
packets are lost.  The TOSSIM document explains the formula used to
calculate loss-rate from the bit-error-rate.  The loss-rate is
dependent on the size of the packets and the bit-error-rate.

If b):
I assume you are using the bit-level radio model of the simulator, as
opposed to the packet-level simulator.  If you are, you need to be
aware that the bit-level radio model can be very slow.  So you might
simply not be waiting long enough.  Depending on your needs you might
consider using the packet-level radio model.  It's faster but less
accurate (no CSMA, no collisions, no hardware acks).  To use it, just
add this in your Makefile:
PFLAGS += -I$(TOSDIR)/platform/pc/packet