[Tinyos-help] Collection: Loosing Connection to a Node

[Bulut ERSAVAS]

Hi Omprakash,

I can't really say that it is quite deterministic. In networks where we
collect measurements every 15 minutes, we lost path to some nodes within a
few hours to half a day. Our networks are generally small (i.e. 3 to 5 nodes
per network). There are cases where we lost the connection in a
single-hop-to-root setting. As we are experimenting, the nodes are not moved
around without our knowledge.

This issue happens specifically at two locations. One is a greenhouse with
barely any obstacles. The other is a closed environment where there are
reflective metal walls. For the latter case, the motes are placed very close
to each other (about 10-15 meters).

Would rebooting the motes periodically (e.g. every few hours) help ease this
problem? Is it possible for CTP to get stuck in a state where it can no
longer discover a path to root?

In addition, have you noticed any reliability problems for packets coming
from nodes which are multi-hops away from the root? We seem to loose more
packets in such cases than single-hop transmissions.

Last question: we are using TinyOS 2.0.2. Should we consider employing
latest CVS copy for a better CTP?

Thanks,
Bulut


We encounter this problem at two locations specifically.

On Sun, Apr 6, 2008 at 3:11 PM, Omprakash Gnawali <gnawali at usc.edu> wrote:

> We have not encountered this situation in our testing. Is this bug
> deterministic? Example, it happens after certain number of packets,
> certain number of days, or at a certain location?
>
> If there are very few neighbors, all the possible paths leading to the
> root might not be good enough to deliver packets successfully. The
> number of neighbors can change over time even if you don't move the
> motes.
>
> - om_p
>
> On Fri, Apr 4, 2008 at 9:44 AM, Bulut ERSAVAS <bfersavas at gmail.com> wrote:
> > Hi all,
> >
> > My Main Question: "Is it possible in CTP for a node to get stuck in a
> state
> > where it can no longer find a path to the root? If so, is there any
> > workaround? Would rebooting motes every now and then help?"
> >
> > Rest of the Story (for those interested):
> > --------------------------------------------------------
> > We have 6 separate Collection networks in the field. We collect the data
> > from their root nodes through GPRS modems. Some of the nodes in few of
> those
> > networks lost their path to root node and stop sending their
> measurements
> > (temperature & humidity). We contacted the people on the field and the
> motes
> > stay in their original location.
> >
> > We know that their battery levels were fine looking at the latest data
> sent.
> >
> > Does anyone have any theories as to what might have happened?
> >
> > Thanks,
> > Bulut
> >
> > _______________________________________________
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> >
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> >
>
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