H12-311_V3.0 · Question #43
There are four wireless STAs. According to the following back-off time parameters, which workstation is the priority to occupy the channel?
The correct answer is C. 4. In CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance), each station waiting to transmit selects a random back-off counter and counts it down while the channel is idle; the station whose counter reaches zero first is allowed to transmit. The workstation with a…
Question
There are four wireless STAs. According to the following back-off time parameters, which workstation is the priority to occupy the channel?
Options
- A5
- B7
- C4
- D6
How the community answered
(32 responses)- A3% (1)
- B6% (2)
- C75% (24)
- D16% (5)
Explanation
In CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance), each station waiting to transmit selects a random back-off counter and counts it down while the channel is idle; the station whose counter reaches zero first is allowed to transmit. The workstation with a back-off value of 4 reaches zero before any of the others, so it gains priority access to the channel. Options A (5), D (6), and B (7) are all incorrect because their back-off counters are larger, meaning those stations must wait longer and will lose the contention to the station with the smallest value. Memory tip: the smallest back-off number wins the channel - think of it as a race where the lowest starting count finishes the countdown first.
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