Modulation and Coding JN0-452 Practice Questions (Page 1)

Questions 1–5

1. 1expert · hard

   A network engineer is troubleshooting a slow Wi-Fi link. The client is a laptop with 2 spatial streams, connected to an 802.11ac AP on an 80 MHz channel. The AP reports the client is using MCS 6. The engineer suspects the client should be using a higher MCS. What is the most likely reason the client is not using MCS 9?

   • AThe client is too far from the AP, and the SNR is too low for 256-QAM.
   • BThe AP is configured to use a 40 MHz channel, not 80 MHz.
   • CThe AP has disabled MCS 8 and 9 to improve reliability for other clients.
   • DThe client's driver does not support 256-QAM, so it is limited to MCS 7 or lower.
   Reveal Solution Discussion Select an answer first
2. 2foundation · easy

   Which statement about MCS indices and data rates is true?

   • AHigher MCS indices generally provide higher data rates but require better signal quality
   • BHigher MCS indices always use more spatial streams
   • CLower MCS indices are more susceptible to interference
   • DAll MCS indices provide the same data rate on a given channel width
   Reveal Solution Discussion Select an answer first
4. 3expert · hard

   A network engineer is optimizing a Wi-Fi 6 network in a convention center. During a large event, the engineer notices that many clients are using MCS 0 (BPSK 1/2) even though they are close to the APs and have high SNR. What is the most likely cause of this behavior?

   • AThe AP is experiencing high interference on the channel, causing the rate adaptation algorithm to select a more robust MCS.
   • BThe AP is configured to use a very low transmit power, causing the clients to see a weak signal.
   • CThe clients are using a power-saving mode that forces them to use a lower MCS.
   • DThe clients are legacy 802.11b devices that only support BPSK.
   Reveal Solution Discussion Select an answer first
5. 4application · medium

   A junior engineer is reviewing a Wi-Fi 6 (802.11ax) AP's client table and sees a client associated at MCS 9. The engineer wants to explain what this index represents to a colleague. Which statement accurately describes MCS 9?

   • AMCS 9 specifies a combination of modulation and coding rate, but the actual data rate depends on channel width and number of spatial streams.
   • BMCS 9 indicates the client is using BPSK modulation, which is the most robust scheme available.
   • CMCS 9 is a fixed data rate of 600 Mbps that does not change with environmental conditions.
   • DMCS 9 always uses 1024-QAM with a 5/6 coding rate, regardless of channel width or spatial streams.
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6. 5application · medium

   A hospital is deploying Wi-Fi for patient monitoring devices that send small, critical data packets. The devices are stationary and have a consistent SNR of 30 dB. The network team wants to ensure the highest reliability for these packets. Which MCS configuration should they prioritize?

   • ADisable retries and rely solely on FEC to recover from any errors.
   • BUse the highest MCS available (e.g., MCS 11 in Wi-Fi 6) to minimize transmission time.
   • CConfigure the AP to use only 20 MHz channels to reduce interference and improve SNR.
   • DUse a moderate MCS with a lower coding rate (e.g., MCS 4 with 16-QAM 1/2) to provide more error correction.
   Reveal Solution Discussion Select an answer first