Which TWO statements correctly compare 802.11ac and 802.11ax features?
OFDMA allows multiple users to share subcarriers simultaneously, improving efficiency in dense environments.
Why this answer
Option A is correct because 802.11ax (Wi‑Fi 6) introduces Orthogonal Frequency Division Multiple Access (OFDMA), which allows multiple users to share subcarriers simultaneously, improving efficiency in dense environments. In contrast, 802.11ac (Wi‑Fi 5) uses Orthogonal Frequency Division Multiplexing (OFDM), where each transmission occupies the entire channel for a single user, leading to less efficient channel utilization. Option C is correct: WPA3 is mandatory for Wi‑Fi 6 (802.11ax) certification, while for 802.11ac it is optional—devices can still obtain Wi‑Fi 5 certification with WPA2 only.
Option B is incorrect because 802.11ac supports a maximum of 256‑QAM; 1024‑QAM is first introduced with 802.11ax. Option D is wrong: 802.11ac operates exclusively in the 5 GHz band, but 802.11ax operates in both 2.4 GHz and 5 GHz. Option E is false: both standards support 20, 40, 80, and 160 MHz channel widths; 802.11ac does not exclusively use 80 MHz, and 802.11ax does not use 160 MHz exclusively.
Exam trap
Cisco often tests the misconception that higher QAM values (like 1024-QAM) are backward-compatible across Wi-Fi generations, but 802.11ac is limited to 256-QAM, and 802.11ax is the first to support 1024-QAM.
Why the other options are wrong
802.11ac supports only up to 256‑QAM; 1024‑QAM is introduced with 802.11ax.
802.11ac operates only in the 5 GHz band, but 802.11ax operates in both 2.4 GHz and 5 GHz.
Both 802.11ac and 802.11ax support a range of channel widths, including 20, 40, 80, and 160 MHz; neither standard restricts to a single channel width.