CWNA: Certified Wireless Network Administrator v108 — Question 5

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

Answer options

• 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.

Correct answer: B

Explanation

The correct answer is B because OFDM was indeed first introduced in the 802.11a standard and is utilized in subsequent PHYs such as ERP, HT, and VHT. Option A is incorrect as OFDM does not implement BPSK to achieve such high data rates. Option C is misleading since OFDM is also used in the 2.4 GHz band in standards like 802.11n. Option D is wrong since OFDM is not associated with FHSS PHY devices, which use a different modulation technique.