A few months ago I posted in the thread ‘6.1r3 slow performance’ about call quality issues our company was having with the Ascom i62 VoIP handsets following the upgrade of 5.1r5 to 6.1r3. In the time between we have work with our supplier and identified one configuration issue, and been able to reproduce a second issue that appears to be Aerohive firmware related. If anyone else is having VoIP issues this may be of some use.
Firstly I would like to acknowledge the replies from Roberto Casula in the thread above. The advice he gave was practical and helped a lot.
If you are using the Ascom devices I would also recommend going over the two Interoperability Reports. One covers the Call Manager settings and the other the Ascom handset settings.
The environment is Cisco Call Manager (CUCM) 9.1 with Aerohive AP330’s running 6.1r3.
Call Manager Configuration
While we had set the codec on the handset according to the Ascom Interop Guide, one site in particular reported quality issues for internal calls. As part of the testing we were able to identify that the codec specified by the Ascom handset (G711) was not the codec being negotiated (G722) for internal calls.
It is possible to see the codec in use on some model Cisco desk phones (such as the 79xx series) by pressing the ‘?’ button quickly twice during the call.
From what I now understand the codec is negotiated between the devices, and as the Ascom is G722 capable the internal desk phones were negotiating to use this codec. (This also explained why external calls were a better quality, because they gateway negotiated a different codec.) According to our providers the G722 codec is not noted for being ‘wi-fi friendly’.
To fix this problem a new Device Pool and new Region were created on the Cisco Call manager specifically for the Ascom phones. The Call Manger setting and the Ascom handset settings have been configured to use G729a for intra-site calls. This has fixed a lot of the call quality issues, but there are still issues in some areas of the building following the 6.1r3 upgrade.
There is still an open case with Aerohive concerning the 6.1r3 firmware. We have performed a number of tests at several sites and can see the same problem in one specific scenario. The issue appears in areas with marginal RF coverage. It is very easy to duplicate at one site where the building was extended and coverage is only provided in the new room by a single AP.
If the AP is running 5.1r5 the Ascom call quality is usable. (I would rate it the same quality as a mobile phone call.) If the AP is changed to 6.1r3 the call quality is unusable in the same area. In this situation the person on the desk phone can hear most of the conversation from the Ascom, but the Ascom can hardly hear the desk phone. The only difference is the 6.1 firmware. (I believe we had this issue with earlier versions of the 6.1 firmware, but have not retested with them.)
We are looking at any areas with marginal coverage, but can defiantly reproduce VoIP quality issues by changing the firmware to 6.1r3. However in areas with an RSSI on the device of -67 or better it is possible to get good call quality on VoIP.
Hope this is of help to someone!