[Olsr-dev] Bug in function olsr_tc_update_edge ?

[Henning Rogge]

Am Dienstag 19 Februar 2008 11:40:37 schrieb sebastian sauer:
> hell, yes :) i would even say it's a bunch of correctness issues, and
> hennig may have a different opinion than i but i disagree that the ETX/LQ
> in the MIT paper suffers from the same correctness issues.
> it's just us.
Do you have an argument for this oppinion except "I think so" ?
Last time we discussed this I quoted the paper and you did not reply...

Just to do it again:
See "3.1 Metric":
(http://pdos.csail.mit.edu/papers/grid:mobicom03/paper.pdf)
> ETX = 1 / (df * dr)
>
> The delivery ratios df and dr are measured using deticated link probe
> packets. Each node broadcasts link probes of a  fixed size, at an average
> period r (one second in the implementation). To avoid accidental
> synchronization, r is jittered by up to +-0.1r per probe. Because the probes
> are broadcast, 802.11b does not acknowledge or retransmit them. Every node
> remembers the probes it receives during the last w seconds (ten seconds in
> our implementation), allowing it to calculate the delivery ratio from the
> sender at any time t as:
>
> r(t) = count(t-w,t) / (w/r)

The MIT paper states that all nodes use a fixed period r and a constant 
timewindow "w" for ETX calculations...

Henning

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