Advanced Mobile Phone Service: Control Architecture

The cellular concept, which achieves radio spectrum efficiency through the technique of frequency reuse, requires a grid of control elements (cell sites) distributed throughout a mobile coverage area to serve as the interface between the large numbers of moving customers and the nationwide switched telephone network. Meeting these requirements in a cost-effective manner and providing a framework for offering a variety of services to A M P S customers requires a complex yet flexible control architecture. Before proceeding with our description of the system control architecture, which draws heavily on earlier investigations,1-3 it will be helpful to look at some of the important system interfaces with the nationwide switched (wire-line) telephone network and with mobile users. 43 2.1 Network interface A single AMPS system is designed to serve customers within a given geographical area, known as a Mobile Service Area (MSA). This usually corresponds to a metropolitan area including a central city, its suburbs, and some portion of its rural fringe (see Fig. 1). However, it could encompass a portion of an extremely large metropolitan area or perhaps two or more cities located relatively close together. Mobile customers are expected to subscribe to service in a specific MSA. While operating within its boundaries, a customer is termed a "home mobile." Outside this area, the customer is termed a "roamer." An objective of AMPS is to provide dial access between home mobiles and any other telephone (mobile or land-line) reached through the wire-line telephone network.