IPv6 Soft Handover Applied to Network Mobility over Heterogeneous Access Networks

Toward seamless inter-networking between cellular networks and Wireless LAN, one of the major challenges is seamless vertical handover between different access technologies. Even in heterogeneous access networks which provide combined radio coverage, users may still suffer from packet losses due to bad radio conditions during the handover. Eurecom IPv6 soft handover can reduce packet losses even in the case of vertical handover. Considering that Network Mobility (NEMO) has an advantage of hiding mobility functions from users involved, Eurecom IPv6 soft handover and NEMO are expected to provide a good combination. This paper proposes IPv6 soft handover extension for NEMO over heterogeneous access networks to achieve better performance for UDP and TCP traffic. The proposed method called NEMO-SHO uses two different interfaces simultaneously during vertical handovers, and provides good Quality of Service for the users regardless of the radio coverage quality. Using 3G and IEEE802.11b interfaces, our experiments show that NEMO- SHO can achieve better performances for UDP traffic and constant-bit-rate TCP traffic than Make-Before-Break handovers in lossy radio conditions. We find that in case of TCP traffic the performance gain of NEMO-SHO is more affected by the difference of bandwidth and transmission delay between the two links due to the larger amount of outstanding TCP segments.