What are the rates supported by 802.11a?

Question

Options

• A6, 12, 24, 54 Mbps
• B6, 9, 12, 18, 24, 36, 48, 54 Mbps
• C6, 12, 18, 24, 36, 48, 54 Mbps
• D6, 9, 12, 18, 24, 30, 36, 48, 54 Mbps

• A
  8% (4)
• B
  70% (35)
• C
  18% (9)
• D
  4% (2)

Explanation

Option B is correct because 802.11a uses OFDM (Orthogonal Frequency Division Multiplexing) in the 5 GHz band and supports exactly eight data rates: 6, 9, 12, 18, 24, 36, 48, and 54 Mbps, with 6, 12, and 24 Mbps being mandatory and the rest optional. Option A lists only the three mandatory rates plus 54 Mbps, omitting the optional rates in between. Option C drops the 9 Mbps rate, which is a valid optional rate in the standard. Option D invents a 30 Mbps rate that does not exist in 802.11a.

Memory tip: Count the rates in option B - there are exactly 8 of them, and 802.11a is often associated with the number 8 (8 rates, 5 GHz band, introduced around 1999 alongside 802.11b). If you remember "8 rates topping out at 54 Mbps," you can eliminate any answer that has more or fewer entries or includes an unfamiliar value like 30 Mbps.

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