[Tinyos-help] [Tinyos-devel] Issue regarding implementation of the Link Estimator

Philip Levis pal at cs.stanford.edu
Tue Aug 14 08:22:04 PDT 2012


On Aug 14, 2012, at 4:02 PM, Adrian Dudau wrote:

> Hi everyone,
> 
> I have stumbled upon the following issue while trying to port the TinyOs Link Estimator implementation onto a different platform. In the file LinkEstimatorP.nc, there is a NeighborTable structure that holds the up-to-date link quality information to all the neighbouring nodes. This table is parsed and the corresponding eetx value is returned when the module is asked the link quality of a specific node. My issue is the following: what happens when the connection with a neighbour disappears? As the corresponding RoutingTable seems to be updated only upon receiving a message from that node (by calling updateNeighborEntryIdx() on the corresponding entry), the link information seems to stick in the table and continue to be reported to the caller even when they are not connected anymore. It seems like a too obvious flaw, so I somehow expect that I'm missing something, though I can't see it at this moment. So I appreciate someone else's view on this :)

This is more a question for -help, I'm moving it there.

The link estimator doesn't assume a particular beacon rate; it might receive no packets because the node has an excessively long beacon timer. The assumption is that if a node starts sending packets to the dead destination, then none of them will be acked, and these failed transmissions will then update the link estimate.

Phil




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