CWDP CWDP QoS and Voice/Video over WLAN

Question 1

Which IEEE standard defines Quality of Service mechanisms for WLANs, including EDCA and TXOP?

Accepted Answer

IEEE 802.11e

Answer

IEEE 802.11e introduced QoS enhancements including Enhanced Distributed Channel Access (EDCA) and transmission opportunity (TXOP).

Question 2

In WMM (Wi-Fi Multimedia), which access category has the highest priority?

Accepted Answer

Voice (AC_VO)

Answer

AC_VO (Voice) has the shortest arbitration inter-frame spacing and smallest contention window, giving it highest channel access priority.

Question 3

What is the primary purpose of TXOP (Transmission Opportunity) in 802.11e?

Accepted Answer

Allow a station to transmit multiple frames within a bounded time period

Answer

TXOP grants a station a time window to send multiple frames back-to-back after winning channel access, reducing per-frame overhead.

Question 4

What one-way latency budget is recommended for VoIP over WLAN to maintain acceptable call quality?

Accepted Answer

Less than 150 ms

Answer

ITU G.114 recommends one-way latency under 150 ms for toll-quality voice; exceeding this degrades call quality noticeably.

Question 5

How does DSCP markings relate to WMM access categories in a Voice over WLAN deployment?

Accepted Answer

APs map DSCP values to WMM AC queues for traffic prioritization

Answer

APs inspect DSCP markings on incoming IP packets and map them to the appropriate WMM access category queue.

Certified Wireless Design Professional (CWDP) Practice Test