The maintenance of Quality of Service (QoS) is more challenging issue when the concept of handover diverts from horizontal handover to vertical handover. QoS is defined in terms of throughput, end to end delay, jitter and packet loss etc. In this paper Wi-Fi and WiMAX technologies are focused to form a heterogeneous network environment. The proposed approach performance is measured and analyzed and found better for QoS parameters at time of Interface Swapping from Wi-Fi to WiMAX and WiMAX to Wi-Fi.