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Top1. Introduction
The Beyond Third Generation (B3G) wireless communication systems intends to offer the end-users with the appropriate global information access competences and personalized wireless communication services (Chandavarkar and Reddy, 2012; Kassar et al., 2008; Assouma et al., 2006). Their architecture aims to integrate an assortment of heterogeneous wireless networks over an Internet Protocol (IP) backbone. The recently sanctioned / ratified IEEE 802.21 Media Independent Handover (MIH) standard intends to support seamless roaming amongst various wireless access technologies, comprising of the GSM, UMTS, WLAN, WiMAX and the Bluetooth, through different handover techniques. Several leading world’s operators have already started deploying this approach. In January 2009, 4G network CLEAR was launched through the collaboration of Clearwire and Intel in Portland, Oregon, USA. Similarly, major carriers such as AT&T are in process of converting their existing networks into 4G by using a successor of UMTS – 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) standards (Kassar et al., 2008).
The International Telecommunication Union (ITU) Radiocommunication Sector (ITU-R) has explicitly specified a globally accepted and agreed definition of the 4G in consultation with its diverse stakeholder groups, as to what should be encompassed in the nucleus of a 4G System (or International Mobile Telecommunication Advanced – IMT Advanced as defined by ITU), so that technologies could earn the right to be categorized into this group. At present, there are only two families of standards that fit in the bill – LTE Advanced and WiMAX Release 2 (Assouma et al., 2006). Though High-Speed Packet Access (HSPA) and Evolved High Speed Packet Access (HSPA+) are marketed by various network operators as 4G services in various parts of world, but they are not considered 4G in the true sense (Kassar et al., 2008; Zhang et al., 2007).
The convergence of internet and wireless mobile communication accompanied by massive growth in number of cellular subscribers has led mobility management to emerge as a significant and challenging domain for wireless mobile communication over the internet (Chandavarkar and Reddy, 2012; Kassar et al., 2008; Assouma et al., 2006; Zhang et al., 2007). Mobility management enables serving networks to locate roaming terminals for call delivery (i.e. location management) and ensures a seamless connection as the MT enters into the new service area (i.e. handover management). The hierarchy of the mobility management in a heterogeneous network environment is depicted in Figure 1.
Figure 1. Hierarchy of mobility management in a heterogeneous network environment
Location management facilitates the serving network to trace the location of the MT; and constitute(s) two stages, i.e. location registration and call paging. In location registration, the MT periodically advises specific signals to inform the network of its present location (or of its newest access point ~ AP) in order to keep the location database updated (Vuong, 2008). Call paging, which is invoked after the location registration procedure, is for querying the network about the MT’s location profile in order to deliver any calls successfully (Zekri et al., 2012; Misra et al., 2008; George et al., 2008).