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CWS 802.11 Standards and Protocols Flashcards

7 cards from real CWS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 CWS 802.11 Standards and Protocols flashcards as text

  1. In 802.11 OFDM, what is the purpose of the cyclic prefix (guard interval)?

    Answer: Prevent inter-symbol interference caused by multipath

    The cyclic prefix provides a guard interval between OFDM symbols so that multipath echoes from one symbol do not corrupt the next symbol.

  2. What technology does 802.11ax use to allow simultaneous uplink transmissions from multiple clients?

    Answer: UL MU-MIMO and OFDMA

    802.11ax introduced uplink MU-MIMO and OFDMA, enabling the AP to schedule multiple clients to transmit simultaneously on different resource units.

  3. Which 802.11 feature allows an AP to request that associated clients adjust their transmit power to reduce co-channel interference?

    Answer: TPC – Transmit Power Control

    Transmit Power Control (TPC), defined in 802.11h, lets the AP signal clients to lower their transmit power, reducing interference on shared channels.

  4. What is the primary function of BSS Coloring introduced in 802.11ax?

    Answer: Reduce unnecessary deferrals from overlapping BSSs by tagging frames

    BSS Coloring adds a numeric color field to PHY headers so STAs can identify frames from a foreign BSS and potentially ignore them rather than deferring unnecessarily.

  5. How many non-overlapping 20 MHz channels are available in the 2.4 GHz band in the United States?

    Answer: 3

    In the US 2.4 GHz band, only channels 1, 6, and 11 are non-overlapping when using 20 MHz channel widths.

  6. What does the 802.11r amendment specifically optimize?

    Answer: Fast BSS Transition (roaming) handoff times

    802.11r (Fast BSS Transition) pre-authenticates clients with target APs before the handoff, reducing roaming latency critical for voice and real-time applications.

  7. Which 802.11 PHY layer mode is used when legacy 802.11b devices must coexist with 802.11g devices on the same BSS?

    Answer: ERP mixed mode with CTS-to-self or RTS/CTS protection

    When 802.11b clients are present, 802.11g APs activate ERP protection using CTS-to-self or RTS/CTS to prevent legacy devices from transmitting during OFDM frames.