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Mobile stream control transmission protocol (MSCTP) is ideal to support vertical handover (VHO) between WLANs and 3G cellular networks by enabling a mobile client to switch freely between IP addresses acquired in different networks. We show that the MSCTP-based VHO scheme suffers from poor throughput performance during WLAN to cellular forced VHOs. We propose a novel error-recovery scheme called sending-buffer multicast-aided retransmission with fast retransmission (SMART-FRX) to improve performance during VHO by multicasting the buffered and new data over both WLAN and cellular links when handover losses occur, while keeping the retransmissions of wireless error losses, that occur over the cellular link, over the same link. In this way, the link utilization can be increased significantly and unnecessarily long delays of packet retransmissions over the possibly unreachable secondary link can be avoided. Simulation results are presented to demonstrate the effectiveness of the proposed scheme.