Architecture and testbed implementation of vertical handovers based on SIP session border controllers

This paper describes a Session Initiation Protocol (SIP) based solution for mobility management that provides seamless mobile multimedia services in a heterogeneous scenario where different radio access technologies are used (802.11/ WiFi, Bluetooth, 2.5G/3G networks). The solution relies on the so called "Session Border Controllers" which are now widely used in many commercial SIP telephony solutions, mainly to deal with NAT traversal. Session Border Controller functionality has been extended to support seamless mobility for multimedia applications. A prototype of the proposed solution focused on VoIP services has been implemented in a test bed which is able to perform seamless handovers (and NAT traversal) using the 802.11, Bluetooth and 3G (UMTS) access networks. Measurements results are reported which analyze the performance of the solution in a real world environment, using commercial WiFi and 3G services.