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I have a problem which i don't know how to calculate or more specifically what am I missing. The subject is about 802.11 (wifi)

The selected PHY rate is 54Mbit/s, that is whenever DATA is being sent the rate is 54Mbit/s, and when the node is not sending anything the rate is 0. To simplify the task, assume that there are no collisions and no errors in the channel.

The frames in the figure are marked up as follows:

Message Purpose Duration, us RTS Request to send 44 CTS Clear to send 48 DATA Payload packet Variable ACK Acknowlegement 44 SIFS Inter-frame-spacing 4 DIFS Same as SIFS 16 Backoff MAC arbitration 0..63

The question is: What would be average effective throughput (in Mbit/s) with basic signaling if the DATA packet takes 166 microseconds? Write your answer as average effective bit rate for whatever is being put into DATA packets. Allowed error is 2%

What am I missing?

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  • $\begingroup$ What have you tried? Where did you get stuck? $\endgroup$ – dkaeae Dec 21 '18 at 8:15
  • $\begingroup$ Thank you for the question. I tried to compare the time of data with overall time but it seems that i might have to do something to the data in order for the comparison to work $\endgroup$ – Copsa Dec 21 '18 at 14:05
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Okay so I managed to solve it.

It was simply: PHY rate * (DATA time / Access cycle time, where backoff = 30us)

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