Throughput of legacy Wi-Fi: What is the maximum data rate defined by the IEEE 802.11a standard?
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A6 Mbps
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B11 Mbps
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C22 Mbps
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D54 Mbps
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E108 Mbps (turbo)
Answer
Correct Answer: 54 Mbps
Explanation
Introduction / Context:Legacy Wi-Fi standards have headline data rates that are frequently referenced in certification exams and design discussions. 802.11a introduced OFDM at 5 GHz with a maximum PHY rate of 54 Mbps per 20-MHz channel.
Given Data / Assumptions:
- PHY data rate, not real-world throughput.
- Single 20-MHz channel, standard 11a modulation and coding.
Concept / Approach:802.11a’s OFDM supports multiple rates: 6, 9, 12, 18, 24, 36, 48, and 54 Mbps, with 54 Mbps being the top PHY rate under ideal conditions.
Step-by-Step Solution:
Recall the 802.11a rate set.Identify the highest rate in the mandatory/extended set: 54 Mbps.Select 54 Mbps as the defined maximum PHY rate.Verification / Alternative check:Standards summaries and vendor datasheets consistently list 54 Mbps as the maximum 802.11a rate.
Why Other Options Are Wrong:
- 6/11/22 Mbps: Valid in other contexts (e.g., 802.11b 11 Mbps, PBCC 22 Mbps) but not the 11a maximum.
- 108 Mbps: Vendor “turbo” or channel bonding marketing, not standard 11a.
Common Pitfalls:Confusing PHY rates with application throughput; mixing 11a with 11b/g figures.
Final Answer:54 Mbps