CWNA-109 · Question #3
CWNA-109 Question #3: Real Exam Question with Answer & Explanation
The correct answer is B. OFDM was first introduced in 802.11a and is used by the ERP, HT and VHT PHYs as well.. 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 operat
Question
Options
- AOFDM implements BPSK modulation to allow for data rates up to 7 Gbps.
- BOFDM was first introduced in 802.11a and is used by the ERP, HT and VHT PHYs as well.
- COFDM modulation is used only in 5 GHz 802.11 transmissions.
- DOFDM was used by Frequency Hopping Spread Spectrum (FHSS) PHY devices.
Explanation
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.
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