Due to the popularity of the IEEE 802.11-based LANs and fast development of the IEEE 802.16e MANs, we can expect a heterogeneous network consisting of 802.11-based and 802.16e networks in the near future. In such an environment, heterogeneous handoff is possible. How to keep guaranteeing the handoff connection its QoS demand, and in the meantime, avoid impacting on other connections is a challenge to support real-time applications in a heterogeneous network. In this paper, we develop a heterogeneous network in NS-2 simulator. In addition, we implement application mapping function, call admission control, and scheduling in this heterogeneous network to observe the QoS performance of a handoff connection. The simulation results show that our implemented modules support handoff connections' QoS demands in respect of throughput, and delay. In addition, the implemented call admission control algorithm reduces the blocking rate efficiently.