hello, I have a question about the ACK and the the retransmission frame.
When the coordinator receives the data frame, it will wait for aTurnaroundTime(=12symbol),and then send ACK frame back to the transmitter .
And my question is whether the ACK frame need obey the CSMA-CA algorithm or the ACK frame will be sent immediately ignoring the channel is busy.
And I have another question ,when a sensor node doesnot receive an ACK after macAckWaitDuration symbols, it will retry transimte the former data frame.
And my question is whether the former data frame will obey the CSMA-CA algorithm or the former data frame will be sent immediately ignoring the channel is busy.
For non beacon zigbee network , before the coordinator sent the ACK frame,another end device find the channel is free during the aTurnaroundTime,
it will send the data frame immediately.So the ACK frame may be collision with the data frame ,isn't it ? Or, the coordinator will sense the channel is busy ,
and give up sent the ACK .
In the document of IEEE Std 802.15.4 ™-2003,page 23 says,
"Acknowledgment frames shall be sent without using a CSMA-CA mechanism."
Does the retransmission frame need obey the CSMA-CA algorithm before they are sent ?