Fast vertical handover utilizing sleep mode in WLAN and WiMAX heterogeneous networks

Vertical handover (VHO) latency needs to be minimized for successful handover especially in heterogeneous network environments. In this paper, we propose a VHO scheme to reduce handover latency in heterogeneous wireless networks composed of WLAN and WiMAX networks. The proposed scheme utilizes sleep mode operation of the WiMAX when a mobile station (MS) switches its serving network from WLAN to WiMAX. In this scheme, a MS is connected to its target network and enter to the sleep mode before performing VHO procedure. When the vertical handover occurs, a MS merely returns to the awake(normal) mode and resumes data transmissions with WiMAX. By these prior operations, VHO latency can be dramatically reduced. To evaluate the performance of proposed scheme, simulation has been designed and performed. Results show that VHO latency can be reduced from 57.15 ms of the conventional scheme to 4.28 ms by the proposed one.