We propose a call flow for vertical handover procedure and a soft QoS scheme using dynamic programming (DP) approach for an efficient radio resource management in an environment where several different radio access networks (e.g., WLAN and WCDMA) coexists. We compare the soft QoS scheme with hard QoS scheme and propose a greedy and a DP approach for resource allocation scheme under a vertical handover situation. The proposed scheme is a promising approach for QoS support under the heterogeneous radio access networks. This work is supported by Korea Telecom.