Multihoming at layer-2 for inter-RAT handover

One of main feature of next generation of mobile networks is an integration of existing cellular systems with other wireless access technologies. In order to realize a seamless vertical handover (inter-RAT handover) among these different access technologies, a multi-interfaced mobile station is expected to communicate simultaneously on various network interfaces (i.e. to be multihomed) to achieve best handover performance gain, such as low packet losses and short handover latency. Unfortunately, the conventional multihoming schemes are almost realized at IP layer or above and the handover performance gains are limited. Moreover, these multihoming schemes are not applicable to integrated and tight coupling architectures. In this article, a novel layer 2 multihoming approach is proposed for inter-RAT handover between UMTS and WiMAX in the integrated and tight coupling architectures. This layer 2 multihoming approach has the ability of enabling either soft handover or make-before-break handover in order to adapt to handover scenarios, and can achieve a lossless and short latency handover procedure. The simulation results show that, in case of TCP traffics for handover from UMTS to WiMAX, the layer 2 multihoming approach can achieve a lossless and zero latency handover procedure by enabling soft handover. For handover from WiMAX to UMTS, due to the fact that the performance gain of soft handover is more affected by the difference of bandwidth and transmission delay between these wireless links, the make-before-break handover is preferred and it can achieve lossless and short latency handover procedure.