The safety standard and the handover

WLAN was originally developed for data transmission by terminals whose location does not change. With VoWLAN, however, the WLAN telephone's location is constantly changing. So a VoWLAN installation must be capable of handing the connection over from one access point to the next access point without any noticeable interruption to the connection (seamless handover). This feature is particularly important for installations in large enterprises in which multiple access points are being used. In particular, simple, cheap access points from the consumer sector, and older terminals too, often have problems here.

The WLAN security method selected also has a crucial impact on handover performance. When handing over from one access point to another access point with a better WLAN signal, once the connection has been established the WLAN security must be restored before the next voice data packet can be transmitted. We recommend WPA2-PSK, as this achieves a high level of security with, at the same time, excellent handover times (<40 ms).

We advise against using 802.1x or WPA2-Enterprise in wireless VoWLAN networks, because the restoring of security after a handover to a new access point takes far longer than with WPA2-PSK. This may then result in audible interruptions and interfering sounds.