Utilizing Multiple Networked Switching Systems to Serve Large Metropolitan Areas (7-2)

Commercial cellular service began in the United States with the cutover of the AT&T AUTOPLEX(R) System 100 in Chicago on October of 1983. As the FCC awarded licenses city by city other cities came on line all served by single system stand-alone switches. This resulted in islands of cellular service throughout the country with cumbersome and varied roamer arrangements. Obtaining originating and terminating features, beyond a minimal feature set outside of the home system required manual registration. Enabling calls to be delivered to the subscriber in the visited system required that the caller know the location of the mobile so that they could either dial the (generally hard to find) roamer access number or a local directory number that the mobile customer obtained after manually registering. The dependence on manual registration for roamer service is still widely used today, due to the unavailability of more simplified techniques in many markets.