ASCOM i62 Troubleshooting Manual page 19

Troubleshooting Guide
Ascom i62 VoWiFi Handset
On association, the handset negotiates with the AP and trigger-enables all four Enhanced
Distributed Channel Access (EDCA) categories. These are:
For additional information about U-APSD and how to inspect and troubleshoot U-APSD
setup, see section
U-APSD Flow Example
The example is based on a voice call with bi-directional flow and symmetric codec speech
frames.
A call is established between two parties. In this the parties are assumed to be a VoWiFi
handset and a fixed line phone that resides somewhere on the LAN.
1 In the AP, a voice packet from the fixed phone is received from the wired LAN. The
packet is destined to the handset and the AP intends to transmit the packet on the
RF interface immediately.
However, the destination, that is, the handset for the packet is in PS-mode and since
the AP keeps track of all associated stations PS management mode, this is recognized
and the packet is buffered in the AP.
2 After a short while, the handset transmits a voice packet, as is done every 20 ms with
default settings. This packet is transmitted within the EDCA Access Category "Voice",
which means that it is highly prioritized.
3 The AP receives the packet from the handset, forwards the packet to the wired LAN
and recognizes that the sending station has a buffered packet. The AP releases the
packet and transmits the packet immediately to the VoWiFi handset that now is
awaiting a packet.
The procedure when an AP transmits a buffered packet due to a trigger frame is
called an "Unscheduled Service Period"
28 June 2012 / Ver. A
3. The VoWiFi Handset as
Category
Voice
Video
Best Effort
Background
7.2 U-APSD Troubleshooting
802.11e Priority
6 or 7
4 or 5
0 and 3
1 to 2
on page 55.
TD 92685EN
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