CWDP QoS and Voice/Video over WLAN Flashcards

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

Answer: IEEE 802.11e

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

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

Answer: Voice (AC_VO)

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

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

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

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

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

Answer: Less than 150 ms

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

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

Answer: APs map DSCP values to WMM AC queues for traffic prioritization

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

Which metric most directly indicates the wireless medium is over-subscribed, degrading VoIP quality?

Answer: High channel utilization above 50%

Channel utilization above 50% indicates heavy contention, increasing latency and jitter that degrade real-time voice traffic.