Tae-Sun Yeoum

Improvements to seamless vertical handover between mobile WiMAX and 3GPP UTRAN through the evolved packet core

Recent mobile devices are integrated with multiple network interfaces. Users want their devices connected to the network anytime anywhere. It is highly feasible for a user to change connection to another network for users that leave the service area of its current serving network, where handover needs to be executed seamlessly such that ongoing service sessions are not interrupted. The handover operation not only requires switching the interfaces within a device but also involves seamless reconfiguration of the supporting networks. In this article, an improved IP-based vertical handover technology for mobile WiMAX , 3GPP legacy systems (i.e., Global System for Mobile communications and Universal Mobile Telecommunications System), and 3G Long Term Evolution is presented, which is based on existing optimized handover techniques between mobile WiMAX and 3GPP accesses. Formerly proposed 3GPP WiMAX optimized VHO solutions introduced new elements, such as the forward attachment function and access network discovery and selection function. The ANDSF supports the discovery of target access, and the FAF provides the functionality that authenticates the UE before the execution of VHO. However, the previous technique has limitations that result in data loss and abnormal disconnection to the source access. This article provides a solution by introducing an additional network element called the data forwarding function (DFF) that eliminates the data loss during VHO execution. In addition, the DFF resolves the problem of abrupt disconnection to the source network. The simulation results show that the proposed VHO technique is effective in minimizing data loss during VHO execution between mobile WiMAX and 3GPP networks. As the proposed solution of this article is an IP based handover solution, it can be similarly applied to other communication networks.

Enhancements to FPMIPv6 for improved seamless vertical handover between LTE and heterogeneous access networks

Fast handovers for proxy mobile IPv6 (FPMIPv6) was created to reduce packet-delay that occurs during proxy mobile IPv6 (PMIPv6) handover. Based on vertical handover (VHO) experiments conducted between Long Term Evolution (LTE) and heterogeneous accesses over the evolved packet core (EPC) using FPMIPv6, it was recognized that consistently reliable seamless VHO operations were difficult to accomplish due to limitations in FPMIPv6. Noticeably, VHO performance degradation resulted from the serving network (SN) lacking information of the target network (TN) when the TN is a heterogeneous protocol domain, packet congestion and loss problems occurring on specific network gateway interfaces, and also from using long packet-forwarding paths. In this article, an enhanced FPMIPv6 technique is proposed to solve these problems and improve the VHO operation by using shorter data-paths and improved coordination of buffered packet-forwarding and TN switching, which results in a significantly reduced packet-delay.