[Tinyos-help] MultiHopOscilloscope Packet Loss

[Gaurav Chandwani]

Hi All,

I am facing packet loss problem with CTP in TinyOS 2.0(using the
release 2.0.2) on telosb.
Initially, I faced this in my modified-MultiHopOscilloscope code where
I was accepting multiple
message types and forwarding them to the Root node, but since I had
changed some code,
included a queue, added some functionality etc, it was difficult to
understand whether the
problem is with my addition in code or MultiHopOscilloscope. I saw
packet loss in above case
in different network settingto the extent(worse case) that I dont
receive messages from some nodes/all nodes for even an hour
and then start receiving again.
To trace out the problem, I started with simple
apps/MultiHopOscilloscope(negligible changes to make it compatible
with my Java GUI app) application on 10 nodes (interval = 5 sec),
since it has been tested exhaustively.
All the nodes can reach the Root node directly and they are kept very
close to each other.
I saw a strange behaviour using SerialForwarder - When the application
is running for some hours, sometimes, i dont receive messages from a
particular node for some minutes and then it comes back again.  Its
reproduced many times.

Has anybody seen this kind of behaviour ?
Since MHO is stable, so there should be a problem at my end but I am
not able to find where.

Since the nodes can reach root node directly, they will send message
only to it or also other nodes ?

Can there be a problem with root node sending of messages on UART or
some other queue overflow ? I am using baud rate of 115200.
Next, I will try to use printf to understand at which level the problem is.

As i read, the reliability of CTP should be 99.9% at low traffic rate,
but the 0.1% messages that are lost, are lost
periodically or there is a possibility that they can be lost in chunks
of messages ? and what will be high traffic rate ?

My application is totally based on Node visibility/absence and if I
loose some Nodes falsely for some minutes, its a big problem.
If somebody has any suggestions, they are welcome.

Best Regards,
G

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