On Dec 12, 2006, at 2:53 AM, Miguel Pereira wrote:
Hi David,
Thanks for your help and report.
In my opinion to improve the reliability you should concentrate on
resend messages. The major problem, i think, is because you are not
resending the messages with CCA. I think you should use resend with
CCA by default and only use resend without CCA if the message was
not ack but the CCA check was passed true. If you put the resend
with CCA, even better if with "advanced CCA", I think you will
notice large improvements on Average Packets Dropped but a
significant reduce too on Average Packets Received. Maybe that will
be the price for increasing reliability.
I believe pretty strongly that the MAC layer should not specify a
retransmission policy for reliability. That should be up to the
network layer. E.g., if you look at CTP (the T2 collection protocol),
it might choose a new destination after as little as 1 unacknowledged
packet. Not considering collisions, we've collected pretty good data
suggesting that instantaneous link quality is for the most part
bimodal[1]: losses can be highly correlated.
Phil
[1] http://sing.stanford.edu/pubs/ip-hotnetsV.pdf
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