Dear all, We have a high-data-rate application and we need to decrease the transmission delay (between send.send and send.sendDone).
The payload of our packet is 80 bytes. ( Total packet size is about 100 bytes in Tinyos ) We've adjusted the initial backoff time defined in CC2420csmaP.nc to the range of 10~60 ticks (under 32khz clock) The above two added is about 100*8/250(kbits/sec) + 35/32768 = 4.27ms But when we measure the time between send.send and send.sendDone, the result is 7.82ms, much bigger than 4.27ms Even though we take the congestion backoff time into account( 10~80 ticks ----> 45/32768 = 1.37ms ), the result is still less 7.82ms But the inteval between our testing data packest is 3 seconds, the congestion backoff time shouldn't exist. Our application is broadcast, so we don't consider ACK wait time. Does anyone know why the larger transmission delay in our experiment? We also record the time when the packet is send out ( by the SFD interrupt ), the time between this SFD time and send.sendDone is about 1.99ms What confuse us is this time is much less than the data transmission needed (4.27ms), does anyone know why? Many thanks!! Best regards, Sean
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