Motorola WA840GP User Guide - Page 86

Arbitrary Inter-Frame Space Number AISFN, Transmit Opportunity Limit TXOP limit

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Section 3 Configuration Field EDCA AP and Client Parameters: (ADVANCED) Description WMM uses a protocol called Enhanced Distributed Channel Access (EDCA) to prioritize traffic on the wireless network. EDCA requires that wireless devices assign each intended transmission a priority, within an Access Category (AC). WMM defines 4 Access Categories: • Voice, to give voice traffic the highest priority, since it has the least tolerance for delays and/or loss of data. • Video, to give video a higher priority than other traffic, and optimize real-time video display. • Best Effort, for legacy devices, and/or any other traffic sensitive to delays (e.g., general Internet surfing). • Background, for lowest priority traffic with limited sensitivity to delays (e.g., printing). EDCA manages queues of transmissions within each of these ACs, allocating "slots" of time (or "transmit opportunities") to each, based on three prioritization settings, set per AC: • Arbitrary Inter-Frame Space Number (AISFN), a minimum number of "slots" a transmission will wait in between transmission opportunities. • Contention Window (CW), a minimum and maximum number of "slots" randomly added to the AIFSN, in order to minimize conflicts between transmissions. • Transmit Opportunity Limit (TXOP limit), the length of time allocated to a transmission one it reaches the top of a queue. For example, video is typically given larger TXOP limits because it is more data-intensive. The WA840 manages EDCA prioritization across the network. (continued on next page) 3-52 WA840

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Section 3
Configuration
3-52
WA840
Field
Description
EDCA AP and
Client Parameters:
(ADVANCED)
WMM uses a protocol called Enhanced Distributed Channel
Access (EDCA) to prioritize traffic on the wireless network.
EDCA requires that wireless devices assign each intended
transmission a priority, within an Access Category (AC).
WMM defines 4 Access Categories:
•
Voice
, to give voice traffic the highest priority, since it has
the least tolerance for delays and/or loss of data.
•
Video
, to give video a higher priority than other traffic,
and optimize real-time video display.
•
Best Effort
, for legacy devices, and/or any other traffic
sensitive to delays (e.g., general Internet surfing).
•
Background
, for lowest priority traffic with limited
sensitivity to delays (e.g., printing).
EDCA manages queues of transmissions within each of these
ACs, allocating “slots” of time (or “transmit opportunities”) to
each, based on three prioritization settings, set per AC:
•
Arbitrary Inter-Frame Space Number (AISFN),
a
minimum number of “slots” a transmission will wait in
between transmission opportunities.
•
Contention Window (CW)
, a minimum and maximum
number of “slots” randomly added to the AIFSN, in order
to minimize conflicts between transmissions.
•
Transmit Opportunity Limit (TXOP limit)
, the length of
time allocated to a transmission one it reaches the top of
a queue.
For example, video is typically given larger
TXOP limits because it is more data-intensive.
The WA840 manages EDCA prioritization across the network.
(continued on next page)