What directly affects the MCS used by wireless stations? (Select two.)

Question

Options

• ASNR
• BChannel utilization
• CNumber of connected clients
• DRetry rate
• EFrequency band

• A
  93% (42)
• B
  2% (1)
• E
  4% (2)

Explanation

SNR (A) and retry rate (D) are the two metrics that directly feed into a wireless station's rate adaptation algorithm, which selects the MCS. High SNR enables higher-order modulation (e.g., 256-QAM) and aggressive coding rates, yielding a higher MCS index; when SNR drops, the station steps down. Retry rate acts as real-time feedback - frequent retries signal frame loss or poor link quality, forcing the algorithm to reduce MCS until transmissions succeed reliably.

Why the distractors are wrong:

• B (Channel utilization): Affects medium contention and throughput, but the AP/client still negotiates MCS based on link quality, not how busy the channel is.
• C (Number of connected clients): More clients means less airtime per device, but each client's MCS is still independently determined by its own RF link quality.
• E (Frequency band): Band choice influences propagation and interference, but these effects manifest as SNR changes - the band itself is not a direct MCS input.

Memory tip: Think of MCS selection as a two-signal feedback loop - SNR tells you what the channel can support, and Retry rate tells you what it's actually delivering. Only those two signals directly drive rate adaptation.

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