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Table 19.4 Station EDCA Parameters
Field
Queue
AIFS
(Inter-Frame Space)
cwMin
(Minimum Conten-
tion Window)
Description
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).
For more information, see "QoS Queues And Parameters To Coordinate Traffic Flow" on page 188.
The Arbitration Inter-Frame Spacing (AIFS) specifies a wait time (in milliseconds) for data
frames.
For more information, see DCF Control of Data Frames and Interframe Spaces.
For more information, see "EDCF Control Of Data Frames And Arbitration Interframe Spaces" on
page 190.
This parameter is input to the algorithm that determines the initial random backoff wait time ("window")
for retry of a transmission.
The value specified here in the 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.
For more information, see "Random Backoff And Minimum/Maximum Contention Windows" on
page 191.
Psion Teklogix 9160 G2 Wireless Gateway User Manual
Chapter 19: Quality Of Service (QoS)
Configuring Station EDCA Parameters
199
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