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CWNP Exam CWAP-404 Topic 1 Question 6 Discussion

Actual exam question for CWNP's CWAP-404 exam
Question #: 6
Topic #: 1
[All CWAP-404 Questions]

When performing protocol analysis, you capture an 802.1 lac data frame on channel 52, transmitted at MCS 8. At what data rate was the PHY Preamble transmitted?

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Suggested Answer: C

The data rate at which the PHY preamble was transmitted is 6 Mbps. The PHY preamble is a part of the PPDU that is transmitted before the PHY header and the PSDU. The PHY preamble consists of a series of training fields that help the receiver to detect and synchronize with the signal. The PHY preamble is always transmitted at a fixed data rate that depends on the type of PPDU (e.g., OFDM, HT, VHT, HE). For an 802.1 lac data frame on channel 52, which uses VHT PPDUs, the data rate for the PHY preamble is 6 Mbps. This data rate does not depend on MCS (Modulation and Coding Scheme), which only affects the data rate for the PSDU.Reference:[Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 99-100


Contribute your Thoughts:

Carolann
4 months ago
You may be right, Rosenda. I should reconsider my answer.
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Rosenda
4 months ago
I think the answer is C) 6 Mbps because the MCS index dictates the rate at which the frame was transmitted.
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Lashonda
4 months ago
Why do you think it's 78 Mbps? Can you explain your reasoning?
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Carolann
4 months ago
I disagree, I believe the correct answer is D) 78 Mbps.
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Lashonda
5 months ago
I think the answer is B) 86.7 Mbps.
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Garry
5 months ago
Oh, I see. So the correct answer is A) 54 Mbps then.
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Shayne
5 months ago
Because MCS 8 corresponds to a data rate of 54 Mbps in 802.11ac.
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Lottie
5 months ago
But why do you think so?
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Garry
5 months ago
I'm pretty sure it was 78 Mbps.
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Jarryd
5 months ago
When capturing an 802.11ac data frame, the PHY Preamble is always transmitted at the lowest possible data rate to ensure that it can be decoded by all receivers. For 802.11ac, this rate is typically 6 Mbps in the 5 GHz band. Answer would be (C)
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Shayne
6 months ago
I believe it was 54 Mbps.
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Lottie
6 months ago
I think the data rate was 6 Mbps.
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