Which modulation technique do 802.11a, 802.11n, and 802.11ac use to achieve higher data throughput?

Which modulation technique do 802.11a, 802.11n, and 802.11ac use to achieve higher data throughput?

• A. Direct sequence spread spectrum (DSSS)
• B. Amplitude modulation (ASK)
• C. Frequency hopping
• D. Orthogonal frequency division multiplexing (OFDM)

Answer: (D)

The idea being tested is how Wi‑Fi standards increase data throughput. The technique used by 802.11a, 802.11n, and 802.11ac is OFDM, which stands for orthogonal frequency division multiplexing. OFDM sends data over many narrow subcarriers within a single channel, and those subcarriers are orthogonal to one another so they don’t interfere. This setup lets a lot more data be transmitted in parallel, boosting throughput significantly.

Because each subcarrier can carry its own modulation (like QPSK or higher-order schemes), the overall data rate scales up without needing extra bandwidth. OFDM also includes a small guard interval to reduce intersymbol interference caused by multipath propagation, which helps maintain higher speeds in real-world wireless environments.

Older approaches like direct sequence spread spectrum (DSSS) and frequency hopping were used in earlier standards and are more limited in achievable throughput. Amplitude modulation (ASK) isn’t used for the high-speed, reliable data links these standards require. In short, OFDM is the method that enables the high-throughput performance of 802.11a, 802.11n, and 802.11ac.