Suppose an 802.11b station is configured to always reserve the channel with the

Question

Suppose an 802.11b station is configured to always reserve the channel with the RTS/CTS sequence. Suppose this station suddenly wants to transmit 1,000 bytes of data (the payload of the frame), and all other stations are idle at this time (so, no backoff time). Ignore propagation delay and assume no bit errors. Let DIFS be 50 microseconds and SIFS 10 microseconds. Ignore PHY encapsulation and assume all transmissions occur at the maximum data rate supported by 802.11b (11 MBps).

What is the minimum total time required to transmit the frame and receive the acknowledgment in microseconds?

Explanation / Answer

First sender will send RTS since no backoff time, so time taken = 50 microseconds

Then receiver will wait for 10 microseconds and send CTS, then sender will receive CTS and wait for 10 microseconds before transmitting the data

Transmit Time = 1000 bytes/11 MBps = 90.9 ~ 91 microseconds

Then after receiving the data, the receiver will wait for 10 microseconds before sending acknowledgement.

Therefore total minimum time = 50+10+10+91+10 = 171 microseconds

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