> > I have a few questions regarding link estimation of tinyos 2.x:
I'm working on it too since a few month, so I can help you, but don't hesitate to correct me. > > 1 Are they identical, the link estimator under $TOSDIR/lib/net/4bitle and > the one under $TOSDIR/lib/net/le? If yes, why bother keeping both? If no, > what is the difference between these two? net/le is the simplest estimator, 4bitle add the concept describe in this paper : http://sing.stanford.edu/pubs/sing-07-00.pdf, it uses 4 bits too have a metric which efficiently mix the qualities of the physical, link and network layers, it uses the CompareBit component with the event shouldInsert(...). For now I have only used and modified net/le. > > 2 What is the inage field in each entry of neighbor table? Why is it > initialized to MAX_AGE, rather than 0? I didn't look closely to this parameter but it allow to estimate the number of round (a round correspond to have received BLQ_PKT_WINDOW beacon packets) we haven't be able to update the in-bound quality link of a neighbor (we haven't received beacon from this neighbor). It's initialized to MAX_AGE and decremented to 0 every BLQ_PKT_WINDOW beacon packets received. When you look in the updateNeighborTableEst(...) function we can see that if ((ne->inage == 0) && (ne->outage == 0)) then ne is set to be a invalid entry (like if the neihbor was evicted). > > 3 Why is linkest_footer_t defined this way? Does it imply only one > neighbor entry can be accommodated in the footer? > typedef nx_struct linkest_footer { > neighbor_stat_entry_t neighborList[1]; > } linkest_footer_t; > I'm not yet comfortable with nesC concepts but neighborList[1] doesn't meens that theres only one neighbor entry in the footer, on the contrary if you look in the sources or the LEEP frame describes in the Link Estimator Exchange Protocol TEP, there's as many entry in this list that there are neihgbors in the neihbor table. This information is broadcast and the neighbors can update their out-bound quality link. Note that in 4bitle the out-bound quality link is not used for a reason I don't know, but the LEEP frame stay identical as the net/le estimator to respect the protocol.
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