Seamless vertical handover management for VoIP over intermingled IEEE 802.11g and IEEE 802.16e

Heterogeneous wireless access networks will be deployed in many areas. IEEE802.11g and IEEE802.16e will become key technologies as means of providing wireless broadband access to mobile users. These two different wireless access technologies will co-exist while complementing each other in the near future; hence, a mobile node (MN) with dual interfaces will likely execute many handovers (HOs) between 802.11g and 802.16e networks with different IP subnets. In this paper, we propose an end-to-end vertical HO management (HM) for VoIP over the intermingled 802.11g and 802.16e networks considering the wireless link condition and congestion state of both wireless networks. The HM exploits RTS retries and RTT between an MN and an access point in an 802.11g interface as well as CINR level and MN queue length of an 802.16e interface as HO decision criteria. We then conducted simulation experiments to evaluate the effectiveness of our proposed vertical HM using Qualnet 4.5. Our simulation results show that our proposed HM can preserve VoIP quality during such HOs.