CWS CWS 802.11 Standards and Protocols 3

Question 1

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

Accepted Answer

Prevent inter-symbol interference caused by multipath

Answer

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

Question 2

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

Accepted Answer

UL MU-MIMO and OFDMA

Answer

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

Question 3

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

Accepted Answer

TPC – Transmit Power Control

Answer

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

Question 4

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

Accepted Answer

Reduce unnecessary deferrals from overlapping BSSs by tagging frames

Answer

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.

Question 5

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

Accepted Answer

3

Answer

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

CWS Exam Practice Test

CWS Exam Practice Test

CWS CWS 802.11 Standards and Protocols 3