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The first generation of fully conformant IEEE 802.16-based networks is being deployed throughout the world. Most of these networks do not support full mobility, due to radio access layer limitations. Newer solutions, based on IEEE 802.16-2005 standard, offer mobility support for subscriber stations. Unfortunately, after quickly changing the point of attachment on the WiMAX layer, very slow and inefficient IPv6 reconfiguration takes place. Delays introduced by DHCPv6 stateless automatic configuration and mobile IPv6 can easily diminish or even render useless all benefits gained using the efficient WiMAX - data link layer. IPv6 automatic configuration process was not designed with fast reconfiguration in mind. As handover speed is a crucial requirement in mobile cellular environments, reasons behind delays introduced by IPv6 layer mechanisms have to be analyzed and appropriate countermeasures applied. Proposals include novel use of DHCPv6 relays for remote configuration, solving DAD delays, limiting Binding Update procedure in Mobile IPv6, configuring routing through DHCPv6 communication and some other. This paper describes all stages of full IPv6 handover in IEEE 802.16 environment, focusing on major reasons of reconfiguration delays. A new metric for assessing impact of every stage on handover efficiency is defined. Several proposed improvements to the IPv6 handover process are evaluated and simulation results are presented. A discussion regarding possible generalization of best improvement proposals and further research areas concludes this paper. |
