Yes you will need to use 4.2 release when using the 7921/7925 with the AP1000 series. Otherwise try disabling WMM which will disable U-APSD as a temporary workaround. The 7921/7925 will then use PS-POLL, so battery life will not be impacted.
If it's only a voice gap when roaming, then this is expected. And depending on the authentication mechanism implemented, the audio gap time can vary. If using WPA/WPA2 or 802.1x authentication without CCKM, this can be up 400ms + network delay time. Open, WEP should be less than 150ms. You can also check the call stats menu to see how many packets are lost after the roam, then times that by 20ms.
Its a voice gap for about a second when switching AP's. Its bad enough that the callers miss a few words in the conversation. The strange thing is that the phones switch AP's even if the phone isn't moving. I've attached my config if you'd like to review.
Ensure you use 18.104.22.168 for the WLC and 1.2(1) for the 7921G phone. If the phone is roaming, then there is either enough packet loss on that channel/ap for it to roam or the RSSI (signal) is flapping enough where there is a stronger signal AP. If RSSI is flapping it could be due to multipath. Would suggest to use 5 GHz if possible.
Transferring Crash file from standby: Login to the Active WLC in HA.
From CLI: (Cisco Controller) >transfer upload datatype crash (Cisco
Controller) >transfer upload filename (Cisco
Controller) >transfer upload mode tftp (Cisco Controller) >transfer
This is the start of a display filter cross reference between Wireshark
and OmniPeek. The 1st installment is a table of advanced filters. More
filters will be added as time allows. It is a living doc, so check back
for changes every so often Please feel f...
I have created a Powershell script to automatically add a Wireless Guest
User on Cisco WLCs. (tested on 2500 Series) The script should be
completely self explanatory. Prerequisites: Powershell SNMP Module
(Install-Module -Name SNMP) SNMP Write Access to y...