Modeling and performance analysis of power efficient multi-tier location management in interworked WLAN and cellular network

In multi-radio access networks, it is essential to support multi-tier location management to mobile stations (MSs) with multi-radio interfaces, in order to deliver incoming calls to appropriate radio access networks. In multi-tier location management, the location information of MSs at multi-radio access networks should be managed in an integrated way, and single registration (SR) and multi registration (MR) are widely used multi-tier location management schemes. In SR, MSs register at the registration area (RA) of only one of available access networks. In MR, on the other hand, MSs register at the RAs of all available access networks simultaneously. However, battery power consumption is significant in both SR and MR, since multiple radio interfaces operate simultaneously. Recently, works on efficient power management (EPM) have been carried out in interworked WLAN and cellular network by turning off the WLAN interface when it is not active because the idle state power consumption of WLAN interface is significant. In EPM, if a voice over IP (VoIP) call arrives at WLAN, it is notified through a less power-consuming cellular interface. The paging via cellular interface, however, generates significant signaling load at radio interface because paging has to be performed to all cells within a registration area (RA) of cellular network. In this paper, we propose power efficient multi-tier location management schemes, i.e., power efficient SR (PSR) and power efficient MR (PMR), based on the tradeoff between SR/MR and EPM. The performance of the proposed schemes is analyzed in terms of signaling load and energy consumption. The results show that PSR and PMR have significantly lower signaling load than EPM and have significantly smaller energy consumption than SR/MR.