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Wi-Fi Multimedia (WMM) is a Wi-Fi Alliance interoperability certification based on the IEEE 802.11e standard, which provides Quality of Service (QoS) features to IEEE 802.11 networks. WMM prioritizes traffic that requires more throughput and less delay over traffic where delays aren't as noticeable.

WMM-EDCA settings

Configuring WMM consists of adjusting parameters on queues for different categories of wireless traffic. The four queues are as follows:

  • Back ground: Low priority. High throughput, non-time-sensitive bulk data, such as FTP.
  • Best effort: Medium priority. Traditional IP data. Medium throughput and delay.
  • Video: High priority. Time-sensitive video data with low delay.
  • Voice: Highest priority. Time-sensitive data such as VoIP and streaming media with minimum time delay.

Queues automatically provide minimum transmission delays for video, voice, multimedia, and critical applications. The values are in milliseconds and can be adjusted manually for both the access point and the SIP station.

  • CWMin: Minimum Contention Window. The contention window determines when devices must wait and listen for other transmitting devices before they can transmit, also called a backoff period. Devices generate the backoff period between 0 and this value. If the device doesn't send the frame, it doubles the random backoff value until it reaches CWMax. The CWMin value must be less than the CWMax value.
  • CWMax: Maximum Contention Window. This value is the upper limit to random backoff value doubling.
  • AIFSN: Arbitration Inter-Frame Space. Specifies additional time between when a channel goes idle and the access point or device sends data frames. Traffic with a lower AIFSN value has a higher priority.
  • TxOP: Transmission Opportunity. The maximum interval of time an access point can transmit. This makes channel access more efficiently prioritized. A higher value means higher priority.