Location management in cellular mobile radio networks

− Location Management is the procedure of keeping track of and locating Mobile Terminals (MT’s) in mobile radio communication system so that calls arriving for them can be routed correctly to their current location. The main aim of the Location Management is to track the MT’s using minimum overhead traffic. Since the radio bandwidth is a scarce resource in mobile radio communication systems, it is imperative to develop efficient techniques for minimizing this overhead traffic and thereby maximizing the revenue-generating traffic-carrying capacity of the system. Given the cell-crossing rate of MT’s, call arrival pattern and other design parameters, the intent of the present paper is to put forward an optimal Location Management scheme which can minimize the volume of registration traffic on the air-interface and the SS7 network. In the present paper, the Location Management problem is developed in terms of a node-capacitated graph-partitioning problem. Cells are modeled as weighted nodes and the arcs between them represent the cell-crossing rate of MT’s. The problem involves partitioning nodes of this graph under capacity restriction on the sum of the node weights in each subset of the partition. The objective is to minimize the sum of the cost of the edges (i.e. cell crossing rate or Registration traffic) between the subsets of the partition usually called Location Areas (LA’s). The problem of minimizing the radio access traffic with Paging traffic capacity as an upper bound on the size of the LA is formulated as a Mathematical Programming problem. A specially tailored Branch and Bound algorithm is then used to solve the mathematical formulation with the theoretical guarantee of the global optimality of solution obtained. The presented examples illustrate that using the proposed technique, it is possible to develop truly optimal Location Management schemes for fairly large-size mobile radio communication systems.