When I am searching for Voice over WiFi materials , I found below material presented by Flavien RICHARD during Ciscolive- Cancun (Nov-2012). You must watch this session (recorded version) & it is freely accessible if you have a account with Ciscolive365. Please register yourself & get access to every CiscoLive event session materials for free.
Here are the top 10 recommendations for VoWiFi from Cisco. I remember he was saying “Number Zero” is reading this design guide (Voice over Wireless LAN 4.1 Design Guide). So go through it end to end before follow the other recommendations.
Here is the snapshot of features recommended for a VoWiFi deployment which he described in detail during his presentation. If you have to deploy voice/Data through a single SSID (due to BYOD trend cannot have two seperate SSID for Data & Voice services) you have to compromise certain features like DHCP required, band select which is really good for normal data deployment.
This Cisco support forum video(Basics of Voice over WLAN on a Cisco Controller) illustrate how to configure these features on a WLC.
There are lot of other things he covered ( I have to go through 2-3 times to absorb everything) in his presentation & some interesting stuff about Apple IOS device QoS behaviour with WMM-Allowed & WMM-Required settings on a Cisco controller. I will do some testing on that & will post my findings.
Also mentioned about following cisco support forum document(DOC-26863) to follow when deploying 792x wireless phones. How to get your 792x wireless phones performing reliably
There are some other documents I found useful on this topic. Few of them are previous years Ciscolive event presentation on the same topic.
1. Voice Over Wireless LAN (VoWLAN) Troubleshooting Guide
2. Design Principles for Voice Over WLAN
3. BRKEWN-3012 – Troubleshooting Voice over Wireless LAN Deployment (2012 London)
4. Voice over Wireless troubleshooting Checklist