Wi-Fi multimedia

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Wi-Fi Multimedia ( WMM ), also known as Wireless Multimedia Extensions ( WME ), is a certification based on the IEEE 802.11e standard that is guaranteed by the Wi-Fi Alliance - a voluntary association of over 300 companies in the electronics industry of interoperability in wireless networks (WLAN) - was developed for better use of entertainment electronics and multimedia via WLAN. This is to optimize the streaming of multimedia content (e.g. IPTV or DVB-IPI ) or the use of IP telephony (e.g. for WLAN telephony ).

WMM provides Quality of Service (QoS) features for IEEE 802.11 -based networks for this purpose. A fixed bandwidth is not guaranteed; the data traffic is divided into four categories, which are prioritized differently:

  • "Best possible" (AC_BE)
  • Background (AC_BK)
  • Video (AC_VI)
  • Language (AC_VO)

The properties of each category are defined by several parameters:

  • Acknowledgment Policy (ACKPOLICY): Defines whether the recipient should acknowledge receipt of a data packet.
  • Admission Control Mandatory (ACM): Defines whether the access control is controlled by the access point or the accessing client.
  • Arbitrary Inter-Frame Space Number (AIFSN): Defines a fixed period of time between accesses per category.
  • Contention Window (CW): Defines the time window for the negotiation phase of competing accesses. The window is determined by a minimum (CW MIN ) and a maximum value (CW MAX ).
  • Transmission Opportunity (TXOP): Used to prioritize a category. A category with a higher value, such as voice or video, is given preference in the data transmission. In addition, the values ​​for AIFSN and CW must be defined correspondingly smaller.

A direct connection can be established between two WMM-compatible devices in DLS mode ( direct link setup ). For this purpose, one device is given the MAC address of the other device.

As of 2016, 21,900 different WLAN devices were certified according to WMM.

Individual evidence

  1. ↑ Wi-Fi Alliance (as of January 2016)

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