Restricted sleep mode for effective cell throughput improvement in vertical handover

In this paper, we propose a ¿sleep mode restriction¿ scheme for improving the effective cell throughput of worldwide interoperability for microwave access (WiMAX) systems when a mobile station (MS) switches its serving network from WLAN to WiMAX in heterogeneous networks. In the previous scheme, a MS acquires the information related to vertical handover (VHO) from media independent handover (MIH) server before VHO is performed, and utilizes sleep mode operation (SMO) of the WiMAX. However, in this method, while VHO latency is reduced, the effective cell throughput of WiMAX is degraded because MSs connected to WLAN access point (AP) constantly utilize a certain portion of the WiMAX downlink radio resources. To diminish the performance degradation, we suggest that only MSs with high possibility of VHO can enter SMO and maintain connection with WiMAX. When proposed scheme is applied, the simulation results show that the effective cell throughput degradation of WiMAX is diminished by up to 12.57% compared to the scheme with non-restriction.