Cellular architecture is constituted of the following − A network of cells each with a base station. A packet-switched network for communication between the base stations and mobile switching centres. The public switched telephone networks to connect subscribers to the wider telephony network. In all cellular systems, land area is divided into a number of cells each with its radio service. In AMPS the area is large which in digital services, the area is much smaller. Conventionally cells are hexagonal in shape. Each cell uses a frequency range that is not used by its adjacent cells. However, frequencies may be reused in non-adjacent cells.