QoS Parameters

Quality of Service (QoS) provides you with the ability to specify parameters on multiple queues for increased throughput and better performance of differentiated wireless traffic like Voice-over-IP (VoIP), other types of audio, video, and streaming media, as well as traditional IP data over the Access Point.

Configuring QoS on the Access Point consists of setting parameters on existing queues for different types of wireless traffic, and effectively specifying minimum and maximum wait times (through Contention Windows) for transmission. The settings described here apply to data transmission behavior on the AP only, not to that of the client stations.

AP Enhanced Distributed Channel Access (EDCA) Parameters affect traffic flowing from the AP to the client station.

Station Enhanced Distributed Channel Access (EDCA) Parameters affect traffic flowing from the client station to the AP.

The default values for the AP and station EDCA parameters are those suggested by the Wi-Fi Alliance in the WMM specification. In normal use these values should not need to be changed. Changing these values will affect the QoS provided.

Field	Description
QoS Preset	QoS Preset lists the options: Factory Defaults, WFA Defaults, Optimized for Voice, and Custom. Select any option except Custom from the QoS Preset list to auto-populate the AP EDCA parameters and Station EDCA parameters tables with predetermined values. When you select any option except Custom from the list, the two EDCA tables on the page are then grayed out.
AP EDCA Parameters
Queue	Queues are defined for different types of data transmitted from AP-to-station: Data 0 (Voice)-High priority queue, minimum delay. Time-sensitive data such as VoIP and streaming media are automatically sent to this queue. Data 1(Video)-High priority queue, minimum delay. Time-sensitive video data is automatically sent to this queue. Data 2 (Best Effort)-Medium priority queue, medium throughput and delay. Most traditional IP data is sent to this queue. Data 3 (Background)-Lowest priority queue, high throughput. Bulk data that requires maximum throughput and is not time-sensitive is sent to this queue (FTP data, for example).
AIFS (Inter-Frame Space)	The Arbitration Inter-Frame Spacing (AIFS) specifies a wait time for data frames. The wait time is measured in slots. Valid values for AIFS are 1 through 255.
cwMin (Minimum Contention Window)	This parameter is input to the algorithm that determines the initial random backoff wait time (window) for retry of a transmission. The value specified for Minimum Contention Window is the upper limit (in milliseconds) of a range from which the initial random backoff wait time is determined. The first random number generated will be a number between 0 and the number specified here. If the first random backoff wait time expires before the data frame is sent, a retry counter is incremented and the random backoff value (window) is doubled. Doubling will continue until the size of the random backoff value reaches the number defined in the Maximum Contention Window. Valid values for cwMin are 1, 3, 7, 15, 31, 63, 127, 255, 511, or 1023. The value for cwMin must be less than or equal to the value for cwMax.
cwMax (Maximum Contention Window)	The value specified for the Maximum Contention Window is the upper limit (in milliseconds) for the doubling of the random backoff value. This doubling continues until either the data frame is sent or the Maximum Contention Window size is reached. Once the Maximum Contention Window size is reached, retries will continue until a maximum number of retries allowed is reached. Valid values for cwMax are 1, 3, 7, 15, 31, 63, 127, 255, 511, or 1023. The value for cwMax must be higher than or equal to the value for cwMin.
Max. Burst	The Max. Burst is an AP EDCA parameter and only applies to traffic flowing from the AP to the client station. This value specifies (in milliseconds) the maximum burst length allowed for packet bursts on the wireless network. A packet burst is a collection of multiple frames transmitted without header information. The decreased overhead results in higher throughput and better performance. Valid values for maximum burst length are 0.0 through 999.0.
Wi-Fi Multimedia Settings
Wi-Fi MultiMedia (WMM)	Wi-Fi MultiMedia (WMM) is enabled by default. With WMM enabled, QoS prioritization and coordination of wireless medium access is on. With WMM enabled, QoS settings on the Access Point control downstream traffic flowing from the AP to client station (AP EDCA parameters) and the upstream traffic flowing from the station to the AP (station EDCA parameters). Disabling WMM deactivates QoS control of station EDCA parameters on upstream traffic flowing from the station to the AP. If WMM disabled, all the fields below it are not able to be edited. To disable WMM, click Disabled. To enable WMM, click Enabled.
Station EDCA Parameters
Queue	Queues are defined for different types of data transmitted from station-to-AP: Data 0 (Voice)-Highest priority queue, minimum delay. Time-sensitive data such as VoIP and streaming media are automatically sent to this queue. Data 1(Video)-Highest priority queue, minimum delay. Time-sensitive video data is automatically sent to this queue. Data 2 (Best Effort)-Medium priority queue, medium throughput and delay. Most traditional IP data is sent to this queue. Data 3 (Background)-Lowest priority queue, high throughput. Bulk data that requires maximum throughput and is not time-sensitive is sent to this queue (FTP data, for example).
AIFS (Inter-Frame Space)	The Arbitration Inter-Frame Spacing (AIFS) specifies a wait time for data frames. The wait time is measured in slots. Valid values for AIFS are 1 through 255.
cwMin (Minimum Contention Window)	This parameter is used by the algorithm that determines the initial random wait time for data transmission during a period of contention for Access Point resources. The value specified here in the Minimum Contention Window is the upper limit from which the initial random backoff wait time will be determined. The first random number generated will be a number between 0 and the number specified here. If the timer expires before the data frame is sent, a retry counter is incremented and the random backoff value is doubled. Doubling will continue until the size of the random backoff value reaches the number defined in the Maximum Contention Window.
cwMax (Maximum Contention Window)	The value specified here in the Maximum Contention Window is the upper limit (in milliseconds) for the doubling of the random backoff value. This doubling continues until either the data frame is sent or the Maximum Contention Window size is reached. Once the Maximum Contention Window size is reached, retries will continue until a maximum number of retries allowed is reached.
TXOP Limit	The TXOP Limit is a station EDCA parameter and only applies to traffic flowing from the client station to the AP. The Transmission Opportunity (TXOP) is an interval of time, in milliseconds, when a client has the right to initiate transmissions towards the Access Point. The TXOP Limit maximum value is 65535.
Other QoS Settings
No Acknowledgement	Select On to specify that the AP should not acknowledge frames with QosNoAck as the service class value.
Automatic Power Save Delivery	Select On to enable Automatic Power Save Delivery (APSD), which is a power management method. APSD is recommended if VoIP phones access the network through the AP.

Note: After you configure the QoS settings, you must click Apply to apply the changes and to save the settings. Changing some settings might cause the AP to stop and restart system processes. If this happens, wireless clients will temporarily lose connectivity. We recommend that you change AP settings when WLAN traffic is low.