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Exam CWNA-108 topic 1 question 13 discussion

Actual exam question from CWNP's CWNA-108
Question #: 13
Topic #: 1
[All CWNA-108 Questions]

What statement is true concerning the use of Orthogonal Frequency Division Multiplexing (OFDM) modulation method in IEEE 802.11 WLANs?

  • A. OFDM implements BPSK modulation to allow for data rates up to 7 Gbps.
  • B. OFDM was first introduced in 802.11a and is used by the ERP, HT and VHT PHYs as well.
  • C. OFDM modulation is used only in 5 GHz 802.11 transmissions.
  • D. OFDM was used by Frequency Hopping Spread Spectrum (FHSS) PHY devices.
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Suggested Answer: B 🗳️


Chosen Answer:
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4 months ago
Selected Answer: B
B is correct. CHAPTER 5 - PAGE 173 and 175 (Official Study Guide) 173 --> "This PHY was made available through the 802.11a amendment in 1999." 175 --> "ERP is the first OFDM-based PHY that operates in 2.4 GHz, and OFDM is the first OFDM-based PHY that operates in 5 GHz. HT and VHT, explained later in this section, are both OFDM-based as well."
upvoted 1 times
6 months, 3 weeks ago
http://www.rhyshaden.com/802_11a.htm OFDM is only used in 5Ghz transmissions. 802.11g ERP-OFDM, and 802.11n HT-OFDM are used in 2.4Ghz transmissions and are not specifically OFDM.
upvoted 2 times
2 years ago
Should be c
upvoted 1 times
2 years ago
Ignore my first answer, B is right. The manual states that ERP was the first to use OFDM modulation
upvoted 6 times
4 months ago
I think C is actually the right answer and this question is poorly worded. If they were actually wanting ERP- or HT- flavors of OFDM, I think they would have said it. I can't find any time where the 11g or 11n flavors were not specifically referred to as ERP or HT OFDM, whereas OFDM of the 11a flavor can only be described as OFDM.
upvoted 1 times
Community vote distribution
A (35%)
C (25%)
B (20%)
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