Mobility Management

Abstract

INTRODUCTIONAs already indicated in Chapter 1 (see Figure 1.1), 4G wireless networks will integrate services of different segments such as cellular networks, WLAN, WPAN and even LEO satellites. Several alternative backbone networks will be used, like the public land mobile networks (PLMN), mobile Internet protocol (mobile IP) networks, wireless asynchronous transfer mode (WATM) networks, and low Earth orbit (LEO) satellite networks. Regardless of the network, one of the most important and challenging problems for wireless communication and computing is mobility management . Mobility management enables telecommunication networks to locate roaming terminals for call delivery and to maintain connections as the terminal is moving into a new service area, process known as handoff. The handoff may be executed between different segments (cells) of the same or different systems. The handoff event is caused by radio link degradation or initiated by the system that rearranges radio channels in order to avoid congestion. Our focus in this section is on the first kind of handoff, where the cause of handoff is poor radio quality due to a change in the environment or the movement of the wireless terminal. For example, the mobile user might cross cell boundaries and move to an adjacent cell while the call is in process. In this case, the call must be handed off to the neighboring cell in order to provide uninterrupted service to the mobile subscriber. If adjacent cells do not have enough channels to support the handoff, the call is forced to be blocked. In systems where the cell size is relatively small (microcellular systems), the handoff procedure has an important effect on the performance of the system. Here, an important issue is to limit the probability of forced call termination, because from the point of view of a mobile user, forced termination of an ongoing call is less desirable than blocking a new call. Therefore, the system must reduce the chances of unsuccessful handoffs by reserving some channels explicitly for handoff calls. For example, handoff prioritizing schemes are channel assignment strategies that allocate channels to handoff requests more readily than new calls.Thus, mobility management supports mobile terminals, allowing users to roam while simultaneously offering them incoming calls and supporting calls in progress. Mobility management consists of location management and handoff management.Location management is a process that enables the network to discover the current attachment point of the mobile user for call delivery. The main components of the process are shown in Advanced Wireless Networks: Cognitive, Cooperative and Opportunistic 4G Technology Second Edition Savo Glisic and Beatriz Lorenzo