Mobility management and signaling traffic analysis for multi-tier wireless mobile networks

A multi-tier wireless system integrates the high-tier wireless systems and the low-tier wireless systems into a single system to provide the advantages of both tiers. Such a system is expected to provide better service (more service availability and more cost effectiveness to the users) at the expense of the extra tier-switching management. Examples of multi-tier systems include the interconnection network of a satellite communication network and a terrestrial cellular network, the integration of low-power systems such as wireless personal area networks and cellular systems, and the integration of higher mobility of cellular systems with low-mobility wireless local area networks. In such a system, mobility management is critical, because only when the location of a mobile user is known or tracked can the service quality for the user be guaranteed. In this paper, we study a few mobility management schemes for multi-tier wireless mobile networks under more realistic assumptions. Performance evaluation in terms of registration signaling traffic is carried out, and easy-to-use analytical results are obtained. It is also clear that for service availability, the two-tier system is better than the single one-tier system; we therefore study the probability that a call is forced to terminate in the single low-tier system because the low tier becomes unavailable during the call (such a call can be continued in the two-tier system).