Generally, yes. As ETX increases lossses also increase. I can observe the
fact that
RetxmitTimer in CtpForwardingEngine being fired quite a few times before sucessfully transmitting every packet.
But, only a few times this does not hold with packets getting through
although ETX remains at a higher value.
Please let me know if you want me to redo the experiments if you need any
other information.
Regards,
Manjunath D
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On Thu, 21 Oct 2010, Omprakash Gnawali wrote:
On Tue, Oct 19, 2010 at 1:04 AM, Manjunath Doddavenkatappa
<dodda...@comp.nus.edu.sg> wrote:
Dear All,
? We are not able to figure out a reason why ETX values in CTP increases as
wake-up interval of the LPL (BoXMaC-One) increases. We have a simple setup
of a sender and a root node placed adjacent to each other. Nodes use
maximum power of 0 dBm.
? 1) We are using IPI of 15s. We repeated the experiment at three
different places with sevral runs runs at every location. Different
wake-up intervals were tried back-to-back so that temporal variations are
minimized. We used wake-up intervals of 10, 20, 40, 100, and 1000 (ms).
? 2) We also used "LPL.setRemoteWakeupInterval(&packet, WAKEUP_INTERVAL +
100)" but without any luck.
? 3) Our debug messages show that CTP's RetxmitTimer being fired quite a
few times before sucessfully transmitting every packet.
? 4) I first thought that the loss of data packets in the BoXMAC's
preamble could be the reason, but looking into the LPL code, I understand
that preamble packet losses are not fed into the Link Estimator.
? 5) In some experimental runs, particularly when the wake-up interval
is 1000ms, no packet go-through. Requires a hard reboot.
?6) Searching the archieves for "CTP and LPL on tmote", I found that
similar problem being discussed sometime in Dec 2008. The discussion
suggests quite a few number of changes.
http://mail.millennium.berkeley.edu/pipermail/tinyos-devel/2008-December/003510.html
We should debug this. Do you also observe loss in delivery ratio along
with high ETX values?
- om_p
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