Wireless Multimedia Extensions
Encyclopedia
Wireless Multimedia Extensions (WME), also known as Wi-Fi Multimedia (WMM), is a Wi-Fi Alliance
interoperability certification, based on the IEEE
802.11e standard. It provides basic Quality of service
(QoS) features to IEEE 802.11
networks. WMM prioritizes traffic according to four Access Categories (AC) - voice, video, best effort, and background. However, it does not provide guaranteed throughput
. It is suitable for simple applications that require QoS, such as Voice over IP
(VoIP) on Wi-Fi phones (VoWLAN
).
WMM replace the traditional Wi-Fi DCF distributed coordination function
for traditional CSMA/CA wireless frame transmission with EDCF, Enhanced Distributed Coordination Function, which according to version 1.1 of the WMM specifications by the Wi-Fi Alliance, defines four Access Categories (AC_BK, AC_BE, AC_VI, AC_VO) labels, for the EDCA Enhanced Distributed Channel Access parameters that are used by a WMM-enabled station to control how long it shall set its TXOP Transmission Opportunity, according to the information transmitted by the access point to the station, and is implemented for wireless QoS between over RF media.
The underlying concept of WMM PowerSave is that the station (STA) triggers the release of buffered data from the access point
(AP) by sending an uplink data frame
. Upon receipt of such a data (trigger) frame the AP releases previously buffered data stored in each of its queues. Queues may be configured to be trigger enabled, (i.e. a receipt of a data frame corresponding to the queue acts as trigger), and delivery enabled, (i.e. data stored at those queues will be released upon receipt of a frame). Queues refer to the four ACs defined for WMM.
Wi-Fi Alliance
The Wi-Fi Alliance is a trade association that promotes Wireless LAN technology and certifies products if they conform to certain standards of interoperability. Not every IEEE 802.11-compliant device is submitted for certification to the Wi-Fi Alliance, sometimes because of costs associated with...
interoperability certification, based on the IEEE
Institute of Electrical and Electronics Engineers
The Institute of Electrical and Electronics Engineers is a non-profit professional association headquartered in New York City that is dedicated to advancing technological innovation and excellence...
802.11e standard. It provides basic Quality of service
Quality of service
The quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
(QoS) features to IEEE 802.11
IEEE 802.11
IEEE 802.11 is a set of standards for implementing wireless local area network computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee . The base version of the standard IEEE 802.11-2007 has had subsequent...
networks. WMM prioritizes traffic according to four Access Categories (AC) - voice, video, best effort, and background. However, it does not provide guaranteed throughput
Throughput
In communication networks, such as Ethernet or packet radio, throughput or network throughput is the average rate of successful message delivery over a communication channel. This data may be delivered over a physical or logical link, or pass through a certain network node...
. It is suitable for simple applications that require QoS, such as Voice over IP
Voice over IP
Voice over Internet Protocol is a family of technologies, methodologies, communication protocols, and transmission techniques for the delivery of voice communications and multimedia sessions over Internet Protocol networks, such as the Internet...
(VoIP) on Wi-Fi phones (VoWLAN
Vowlan
VoWLAN is the use of a wireless broadband network according to the IEEE 802.11 standards for the purpose of vocal conversation. In essence, it's VoIP over a Wi-Fi network...
).
WMM replace the traditional Wi-Fi DCF distributed coordination function
Distributed Coordination Function
Distributed coordination function is the fundamental MAC technique of the IEEE 802.11 based WLAN standard. DCF employs a CSMA/CA with binary exponential backoff algorithm....
for traditional CSMA/CA wireless frame transmission with EDCF, Enhanced Distributed Coordination Function, which according to version 1.1 of the WMM specifications by the Wi-Fi Alliance, defines four Access Categories (AC_BK, AC_BE, AC_VI, AC_VO) labels, for the EDCA Enhanced Distributed Channel Access parameters that are used by a WMM-enabled station to control how long it shall set its TXOP Transmission Opportunity, according to the information transmitted by the access point to the station, and is implemented for wireless QoS between over RF media.
Power Save Certification
The Wi-Fi Alliance has added Power Save Certification to the WMM specification. Power Save uses mechanisms from 802.11e and legacy 802.11 to save power (for battery powered equipment) and fine-tune power consumption. The certification provides an indication that the certified product is targeted for power critical applications like hand-phones and portable power devices.The underlying concept of WMM PowerSave is that the station (STA) triggers the release of buffered data from the access point
Wireless access point
In computer networking, a wireless access point is a device that allows wireless devices to connect to a wired network using Wi-Fi, Bluetooth or related standards...
(AP) by sending an uplink data frame
Data frame
In computer networking and telecommunication, a frame is a digital data transmission unit or data packet that includes frame synchronization, i.e. a sequence of bits or symbols making it possible for the receiver to detect the beginning and end of the packet in the stream of symbols or bits...
. Upon receipt of such a data (trigger) frame the AP releases previously buffered data stored in each of its queues. Queues may be configured to be trigger enabled, (i.e. a receipt of a data frame corresponding to the queue acts as trigger), and delivery enabled, (i.e. data stored at those queues will be released upon receipt of a frame). Queues refer to the four ACs defined for WMM.
See also
- 802.11e: Quality of Service enhancements for Wi-FiWi-FiWi-Fi or Wifi, is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point has a range of about 20...
standard 802.11b - 802.11e-2005 APSD (Automatic Power Save Delivery)
- Sleep Proxy ServiceSleep Proxy ServiceApple's Bonjour Sleep Proxy service is an open sourcecomponent of zero configuration networking, designed to assist in reducing power consumption of networked electronic devices. A device acting as a sleep proxy server will respond to Multicast DNS queries for another, compatible device which has...
- Unscheduled Automatic Power Save DeliveryUAPSDUAPSD is an acronym for Unscheduled Automatic Power Save Delivery, a feature of Wi-Fi devices that allows them to save power.UAPSD is also known as WMM power save-Practical Uses:...