Edit: I am going to clean this up a bit to try to get a response.
I am having a bit of trouble with these phones. They connect and work but within 5 minutes the call audio becomes one way. It is always the 7921g phone, it stops receiving audio. The issue is very strange. I have verified many many configuration items and have no where to go. The old part of this post didn't read so well so I cleaned up the detail.
EDIT: cleaned up old post below...
We have Call Manager 4.1. The APs are 1310 running IOS 12.4(10b)JA3. We use WLSE to manage access points. The phones work using EAP-Fast or PEAP on ACS 3.3. I have tried the voice vlan on both the 802.11a and b/g with the same results. I have enabled CAC by using the "Optimize for voice" button and the two check marks for WMM. "Dot11 phone dot11e" and "dot11 arp-cache" are also set on the AP. I don't understand how the power is supposed to work but I set "power level client" on the AP as well as both to lower power levels and such, I will read more about this standard since I am now thinking this is the issue. Anyhow when I turn on the phone it connects and obtains an ip address attaches to the call manager and obtains it's configuration. The firmware also updates if it is not firmware 1.1(1).
As I said above the phone works fine for a little while then it seems like it stops processing packets. When the phone stops working the other party can still hear me speak but I can't hear them. In testing I was pinging the phone and was getting responses until the problem starts then pings starts to fail. While still on the call if I hit a number key on the phone I will hear a few seconds of audio and pings start working but about 2 seconds later it stops again. I was sniffing the traffic on the AP and I could see that both directions of the conversation were getting to the AP and the call still looks normal even after I can't hear. After stopping the call I see the phone sending ARP requests for the routers IP and it is still not responding to pings. If I hit a key on the phone at this time it will respond to pings for a couple seconds. If I try to make a call right away the call will be setup but the audio is still one way. If I wait a while I will see it lose its connection to CM and eventually it will give up it's IP address. The phone will just sit there trying to obtain an IP address. I verified it is still a CDP neighbor of the AP and a capture of traffic reveals that there are DHCP responses to the requests but the phone never accepts the offer. The AP still shows the phone association with 0.0.0.0 for the ip address.
The phone just stops processing packets but hitting a key causes it to process packets for a few seconds.
I have the same issue on both 1.1(1) and 1.0(5) firmware.
I have tested 2 phones and they both experience the same issue.
I am going to try to remove the power management settings from the phone to see if that is causing the issue. I will let you know on Monday but if you have any ideas please please chime in and thanks in advance!!!