VoIP Performance in SIP-Based Vertical Handovers Between WLAN and GPRS/UMTS Networks
This paper experimentally analyzes the handover performance of VoIP sessions in a wireless overlay of 802.11 WLANs and GPRS/UMTS networks when mobility is handled at the application layer by SIP. It also assesses the impact of handovers on the VoIP call quality perceived by the user by means of the extended E-model. The study reveals that good performance values are achieved when handing over from GPRS/UMTS to WLAN. Additionally, acceptable quality is obtained for handovers from WLAN towards UMTS. On the other hand, unacceptable values are achieved when moving towards GPRS. The main reason is the delay experienced by SIP messages when traversing the cellular network.