On Wed, Mar 16, 2011 at 5:52 AM, Matthias Schwamborn <schwamb...@cs.uni-bonn.de> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Hi all, > > I've been looking into the TinyOS 2.1.1 CTP (lib/net/ctp) and Link > Estimator (lib/net/le) implementation in order to understand how ETX > values are calculated. > > If I understand it correctly, the ETX stored in both CTP routing and > data packets are actually EETX values as fixed-point real numbers with a > precision of tenths: a value of 15 represents an EETX of 1.5 or ETX of > 2.5 (EETX = ETX - 1), respectively. If it is not EETX, I wouldn't be > able to explain values < 10 (which I've been seeing in packets a lot).
EETX = 10 * (ETX - 1). So, if you see an EETX of 3, that means an ETX of 1.3. Because of the confusion EETX was causing, we have been using ETX for a while now so you might want to update to the latest version of the code. > Now, assuming the above is true, is it still sufficient to assume a node > is a root if it reports a value of 0? This would only mean that there a > no retransmissions needed to successfully transmit a packet to the root > (EETX = 0, ETX = 1) and would be feasible for any node, right? In RootControl.setRoot(), a node sets its ETX to 0. If you see a node advertise an ETX of 0, you know that was a packet from a root node. - om_p _______________________________________________ Tinyos-help mailing list Tinyos-help@millennium.berkeley.edu https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
