On Jun 12, 2008, at 12:29 PM, Anton wrote: > Hello! > > There is probable bug in the > /tinyos-2.x/tos/chips/cc2420/csma/CC2420CsmaP.nc (lines 218 and 225) > > Communicating wireless modules should wait some random delay before > performing Clear Channel Assess. > According to the IEEE 802.15.4 standard, that delay should be > random(2^BE-1) backoff periods, where BE can vary from 3 to 5 (the > default values macMinBE and macMaxBE, IEEE 802.15.4-2006, pages > 163-164). This means that for CC2420 the maximum backoff delay is > 31*320 > = 9920 microseconds (when BE=5), and the maximum initial backoff delay > is 7*320 = 2240 microseconds (since initially BE=3). > > But according to CC2420CsmaP.nc file the maximum initial backoff delay > can be around 9765 microseconds (line 218) and maximum congestion > backoff delay can be around 2441 microseconds (line 225). > It seems that the ranges of these random delays are swapped. Even in > TinyOS 1.x the range of the initial delay is smaller than that of > congestion backoff delay > (/tinyos-1.x/tos/lib/CC2420Radio/CC2420RadioM.nc, lines 745 and > 752). In > TinyOS 2.x this is conversely. > > Also, according to the standard the range of the random delay should > expand (by default BE should change from 3 to 5) each time the channel > is sensed busy (CSMA/CA algorithm - page 172 of the standard). But the > range of all random delays is constant both in TinyOS 1.x and TinyOS > 2.x. > > Please, tell whether it is bug or not.
No, it is not a bug. TinyOS does not have an 802.15.4 MAC. Phil _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
