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 )
+
ack wait time of 256 jiffies = 3,84 msec
I'm correct? or are there others backoff times or delay in transmission?
if I simulate packets transmission in TOSSIM i find that between
send.send(....) and send.sendDone(...) there is a variable time bounded
between 3--->12 msec , it depends on
backoff times and on task scheduling in TOSSIM ?
Please , can anyone answer me?
goodbye , salvatore
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