OverviewThe GSM system uses new technologies efficiently. A collection of innovative technological features demonstrates the engineering strength behind the system. The use of certain technological features is motivated by the benefit offered. The variety in the level of technologies is wide; from small details hidden deep in the system to revolutionary new concepts at the highest level of the system, visible to all users. The world is becoming digitalised. In many fields of technology, analogue systems are being replaced by a modern digital alternative. One of the major improvements over first generation cellular systems is that GSM is a digital system. In this module we will take a closer look at what it means for the system to be digital and what benefits it offers. A key feature of any cellular mobile network is that several users can communicate without disturbing each other. In fact, the frequency band allocated for mobile communications is always limited and a lot of effort is spent on developing systems that can serve as many users as possible in a given band. GSM uses a combination of two distinct methods to meet these stringent requirements. Digitalization GSM is a digital system. Let's take a closer look at what it means if a signal is analog or digital. An analog signal means in principle that the signal can have any value at any time. A good example is a traditional thermometer outside the window. The range of the meter is generally -40 Celsius to +40 Celsius, and the reading can be any value between these values. In theory, if we had good enough eyesight, we could distinguish small, arbitrary differences in temperature. If the thermometer reading were converted to an electrical form, such as voltage, we would have an analog signal. In a mobile communication network, part of the transmission connection uses a radio link and another part uses 2 Mbit/s PCM links. Radio transmission is used between the mobile station (MS) and the base transceiver station (BTS) and the information must be adapted to be carried over 2 Mbit/s PCM transmission links throughout the rest of the network. In a mobile communication network, part of the transmission connection uses a radio link and another part uses 2Mbit/s PCM links. Radio transmission is used between the mobile station (MS) and the base transceiver station (BTS) and the information must be adapted to be carried over 2 Mbit/s PCM transmission links throughout the rest of the network.