Modulation and Coding JN0-452 Practice Questions (Page 4)

Questions 16–20

1. 16foundation · easy

   In Wi-Fi 5 (802.11ac), which MCS index uses 256-QAM with a coding rate of 3/4?

   • AMCS 8
   • BMCS 9
   • CMCS 6
   • DMCS 7
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2. 17expert · hard

   A network team is designing a Wi-Fi network for a hospital where medical telemetry devices transmit critical data. The devices are stationary, have a consistent SNR of 28 dB, and are located in an area with occasional interference from medical equipment. The team must choose between two MCS settings: MCS 4 (16-QAM, 1/2 coding) and MCS 5 (64-QAM, 2/3 coding). Which should they choose, and why?

   • AMCS 5, because the higher data rate reduces transmission time, freeing up airtime for other devices.
   • BMCS 4, because the lower coding rate provides more FEC redundancy, improving the chance of successful first-time delivery.
   • CMCS 5, because 64-QAM provides a higher SNR margin than 16-QAM.
   • DMCS 4, because 16-QAM is more resistant to interference than 64-QAM, regardless of coding rate.
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4. 18application · medium

   A network engineer is troubleshooting a warehouse Wi-Fi deployment. A forklift repeatedly passes between an AP and a client scanner, causing brief signal fades. The client currently reports an SNR of 22 dB. The engineer wants to maximize throughput while maintaining a stable connection during these fades. Which MCS behavior should the engineer expect or configure?

   • ADisable FEC on the AP so the client can use higher modulation orders without the overhead of coding bits.
   • BForce the client to use 64-QAM with a 3/4 coding rate at all times to balance throughput and reliability without dynamic adjustment.
   • CKeep the client at 256-QAM with a 5/6 coding rate to maximize throughput, relying on retransmissions to recover from fades.
   • DAllow the client to dynamically fall back to a lower-order modulation such as 16-QAM or QPSK with a more robust coding rate when SNR degrades.
   Reveal Solution Discussion Select an answer first
5. 19foundation · easy

   What is the role of forward error correction (FEC) in Wi-Fi transmissions?

   • ATo compress the data so it occupies less bandwidth
   • BTo encrypt the data to prevent unauthorized access
   • CTo amplify the signal to overcome noise
   • DTo add redundant bits that allow the receiver to detect and correct some errors without retransmission
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6. 20application · medium

   A network engineer is configuring a new AP for a retail store. The store has a mix of old 2.4 GHz-only IoT devices and modern 5 GHz smartphones. The engineer wants to ensure reliable connectivity for the IoT devices, which are located far from the AP and have low SNR. Which configuration approach is most appropriate for the 2.4 GHz radio?

   • AEnable lower data rates (e.g., 1, 2, 5.5, 11 Mbps) to allow IoT devices to associate using robust modulations like BPSK and QPSK.
   • BConfigure the 2.4 GHz radio to use only 256-QAM to maximize throughput for all devices.
   • CDisable all data rates below 24 Mbps to force IoT devices to use higher modulations and free up airtime.
   • DSet the AP to use a fixed MCS 0 for all 2.4 GHz clients to guarantee maximum range.
   Reveal Solution Discussion Select an answer first