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CWNP CWNA-109 Exam - Topic 6 Question 31 Discussion

What statement is true concerning the use of Orthogonal Frequency Division Multiplexing (OFDM) modulation method in IEEE 802.11 WLANs?
B) OFDM was first introduced in 802.11a and is used by the ERP, HT and VHT PHYs as well.
A) OFDM implements BPSK modulation to allow for data rates up to 7 Gbps.
C) OFDM modulation is used only in 5 GHz 802.11 transmissions.
D) OFDM was used by Frequency Hopping Spread Spectrum (FHSS) PHY devices.

CWNP CWNA-109 Exam - Topic 6 Question 31 Discussion

Actual exam question for CWNP's CWNA-109 exam
Question #: 31
Topic #: 6
[All CWNA-109 Questions]

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

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Suggested Answer: B

OFDM is a modulation method that divides the channel bandwidth into multiple subcarriers, each carrying a single data symbol. This allows for higher data rates and more robust transmissions in multipath environments. OFDM was first introduced in the 802.11a standard, which operates in the 5 GHz band and supports data rates up to 54 Mbps. Later, the 802.11g standard adopted OFDM for the 2.4 GHz band, and the 802.11n and 802.11ac standards enhanced OFDM with features such as MIMO (Multiple Input Multiple Output), channel bonding, and higher-order modulation schemes to achieve data rates up to 600 Mbps and 6.9 Gbps, respectively. These standards are collectively known as the ERP (Extended Rate PHY), HT (High Throughput), and VHT (Very High Throughput) PHYs .Reference:[CWNA-109 Study Guide], Chapter 4: Radio Frequency Signal and Antenna Concepts, page 163; [CWNA-109 Study Guide], Chapter 4: Radio Frequency Signal and Antenna Concepts, page 157.


by Stephen at Jul 30, 2025, 02:25 PM

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Stevie
8 months ago
Wait, OFDM only in 5 GHz? That doesn’t sound right.
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Renea
9 months ago
Totally agree, it’s used in ERP, HT, and VHT PHYs too.
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Tanja
9 months ago
OFDM and FHSS? Nope, that’s not how it works!
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Naomi
9 months ago
BPSK for 7 Gbps? That seems a bit off to me.
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Wilbert
9 months ago
OFDM was indeed first introduced in 802.11a!
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Thaddeus
9 months ago
I don't recall OFDM being linked to FHSS at all; that seems off to me, but I could be mistaken.
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Raelene
10 months ago
I practiced a question similar to this, and I believe option B is correct since OFDM is used in multiple PHYs like HT and VHT.
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Brunilda
10 months ago
I think OFDM is primarily associated with the 5 GHz band, but I might be mixing it up with other modulation techniques.
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Billy
10 months ago
I remember studying that OFDM was indeed introduced with 802.11a, but I'm not sure if it applies to all the other PHYs mentioned.
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Lettie
10 months ago
Ah, I remember learning about OFDM in my networking class. I think I've got a good handle on how it's used in 802.11 WLANs, so I should be able to identify the correct statement.
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Dulce
10 months ago
Okay, I know OFDM is a key modulation technique for 802.11, but I'm a bit fuzzy on the details. I'll try to eliminate the options that I'm sure are wrong, and then make an educated guess.
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Avery
11 months ago
Hmm, this is a tricky one. OFDM is used in 802.11, but I'm not sure about the specifics of which PHYs it's used in. I'll have to think this through carefully.
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Lashawn
11 months ago
I'm pretty familiar with OFDM, so I think I can handle this one. Let me carefully read through the options and think about what I know about OFDM in 802.11 WLANs.
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Delisa
11 months ago
I believe the correct answer is B because OFDM is used by ERP, HT, and VHT PHYs.
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Germaine
1 year ago
I'm not sure, but I think C is also a possibility.
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Nichelle
1 year ago
I agree with Dierdre, OFDM was first introduced in 802.11a.
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Dierdre
1 year ago
I think the answer is B.
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Yolande
1 year ago
OFDM is definitely used in 802.11a, but I'm pretty sure it's also used in other 802.11 PHYs too. Option B seems the most accurate to me.
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Delfina
11 months ago
Yes, OFDM is used in ERP, HT, and VHT PHYs in addition to 802.11a.
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Ariel
1 year ago
I agree, OFDM is used in 802.11a and other PHYs as well.
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