On May 28, 2008, at 2:06 AM, salvatore galati wrote: > hi all. > I'm a student and I'm working on WSN with telosb motes and I'm using > TinyOs 2.x. > Telosb motes uses cc2420 Radio Stack , so i want to exstimate the > maximum transmission time for a packet of 28 bytes ( max payload > lenght) > > i think that the total transmission time depends on: > > time to transmit packet of 46 total bytes [28bytes MAC payload + > 2bytes FCF +10 bytes MAC Header + 5bytes SHR + 1 byte PHR] = 1,4 > msec ( 46*8 / 250Kbit/sec) > > + > > initial backoff time bounded between 0,15--->4,785 msec ( based on > value in opt\tinyos-2.x\tos\chips\cc2420\CC2420.h and opt\tinyos-2.x > \tos\chips\cc2420\csma\CC2420csmaP.nc ) > > + > congestion backoff time bounded between 0,15---->1,185 msec ( based > on same files as over there )
I thought the initial backoff was bigger than that. The units of backoff are 10 jiffies (32kHz ticks), as defined in CC2420.h. The initial backoff is 1-32 backoff units; the congestion backoff is 1-8 backoff units. Those correspond to 300us - 10ms and 300us - 2.5ms accordingly. Phil _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
