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IN CSMA/CA, suppose the channel is idle. Two nodes that have been waiting for the same backoff time, start transmitting simultaneously. The nodes detect the collision and double the Contention Window and back off again.

I want to know how does the node hardware detect such a collision?

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  • I had implemented the CSMA/CA protocol for an underwater network last year. Though I don't remember it in a crystal-clear fashion the system might be waiting for an ACK packet to return in a given timeframe. Also, do you mean to say that the two nodes are caught in a loop with each other?
    – Dhananjai Sharma
    Commented Aug 23, 2018 at 7:01
  • @DhananjaiSharma Acc to CSMA/CA, back off duration will be chosen randomly from (0,contention-window). So it will not be stuck in a loop
    – Harsh Agarwal
    Commented Aug 23, 2018 at 14:09

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I want to know how does the node hardware detect such a collision?

A WiFi node doesn't detect a collision the way Ethernet does. Instead, every frame is acknowledged by the receiver. So if the frame is not acknowledged, the sender assumes there was a collision. It waits a random (back-off) time and tries again.

Here is a more in-depth explanation of the protocol.

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