N10-005 Question #324: Real Exam Question with Answer & Explanation

The correct answer is B: 802.11a / 802.11n. 802.11a operates at 5 GHz, and 802.11n can also operate at 5 GHz-so they share the same frequency band. However, 802.11a uses a single-antenna OFDM scheme, while 802.11n uses MIMO (multiple-input multiple-output) technology, and the two standards are not backward compatible at 5

Question

Which of the following wireless standards can operate on the same frequency but are not compatible?

Options

A802.11a / 802.11b
B802.11a / 802.11n
C802.11b / 802.11g
D802.11g / 802.11n

Explanation

802.11a operates at 5 GHz, and 802.11n can also operate at 5 GHz-so they share the same frequency band. However, 802.11a uses a single-antenna OFDM scheme, while 802.11n uses MIMO (multiple-input multiple-output) technology, and the two standards are not backward compatible at 5 GHz. 802.11b and 802.11g (choice C) both operate at 2.4 GHz but 802.11g is explicitly designed to be backward compatible with 802.11b. 802.11g and 802.11n (choice D) also share 2.4 GHz and 802.11n is backward compatible with 802.11g. 802.11a and 802.11b (choice A) operate on different frequencies (5 GHz vs 2.4 GHz), so they do not share a frequency at all.

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