ABSTRACT
The coverage area in an infrastructure-based wireless network is divided into small regions called
cells
. Each cell in a cellular network is equipped with a base station (BS), and the number of radio channels is assigned according to the transmission power constraints and availability of spectrum. A channel can be a frequency, a time slot, or a code sequence. Any mobile terminal (MT) residing in a cell can communicate through a radio link with the base station located in the cell, which in turn is connected to the core of the network through a base station controller, as shown in Figure 25.1. A group of base stations is controlled by a base station controller. The core network consists of circuit-switched (CS) and packetswitched (PS) domains. The former basically provides voice service over a circuit-based infrastructure that has evolved from analog technologies to more advanced digital technologies. The latter has recently been added to the infrastructure to provide packet-based data services. Both voice calls and data packets follow the same path until reaching the base station controller. In the core, voice calls are handled by the CS domain, which is also connected to the Public-Switched Telephone Network (PSTN), and data packets are transmitted through the PS domain, which is connected to external data networks such as the Internet.
