Wednesday 27 April 2016

CSMA/CA with/without RTS/CTS


CSMA/CA with RTS/CTS  
Step-1 When a sending station wants to transmit data, it first sends (through contention) an RTS (request to send) frame and waits for the destination to reply with a CTS (clear to send) frame.
Step-2 If CTS is detected, then data is transmitted and destination sends an ACK if the data was received completely and correctly.
Step-3 If CTS is not detected, the sending station goes back to compete for the media, in the CSMA/CA mode
Step-4 All other stations that hear RTS or CTS would defer transmission in the duration indicated in RTS or CTS.
Step-5 Both RTS and CTS include the estimated transmission time in the MAC header, so stations which hear either of them, know when the channel is going to be free again, through the NAV mechanism. 
CSMA/CA without RTS  


CSMA/CA with RTS 
 

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