On Aug 10, 2010, at 10:50 PM, Manjunath Doddavenkatappa wrote: > > Just a guess, > > Before asking the routing layer whether a new route to a neighbor is > promising, the estimator > asks physical layer whether the white bit of the incoming packet (from the > sender of the new link) is set. Only if the white bit is set then > estimator proceeds. Since the set white bit already indicates that local > link is good (may be interpreted as ETX=1), it may not be required to verify > the local ETX values of the existing neighbors. > > Please correct me if I am wrong. > > Manjunath D
Sort of -- please refer to the 4-bit link estimation paper. Normally, when the estimator first learns about a neighbor, it waits before making communication with that neighbor available (actually putting it into the link table as an active link). The reason is simple: after receiving only one packet, the estimator can't provide a good estimate, and so making the link active might cause a protocol to choose a very very poor link. The white bit circumvents this initial estimation phase. The white bit indicates that there's a high probability that the underlying link is high quality; this allows the link estimator to skip the initial estimation and make the link immediately available for the routing layer to use. Phil _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
