s for the system. Nordic countries deployed Nordic Mobile Telephones or NMTs, while UK and Ireland went for Total Access Communication System or TACS, and SO on. Roaming was not possible and efficient use of the frequency spectrum was not there. 1.2.2 The Second-generation System (Digital) In the mid-1980s the European commission started a series of activities to liberalise the communications sector, including mobile communications. This resulted in the creation of ETSI, which inherited all the standardisation activities in Europe. This saw the birth of the first specifications, and the network based on digital technology; it was called the Global System for Mobile Communication or GSM. Since the first networks appeared at the beginning of 1991, GSM has gradually evolved to meet the requirements of data traffic and many more services than the original networks. GSM (Global System for Mobile Communication): The main elements of this system are the BSS (Base Station Subsystem), in which there are the BTS (Base Transreceiver Station) and BSC (Base Station Controllers); and the NSS (Network Switching Subsystem), in which there is the MSC (Mobile Switching Centre); VLR (Visitor Location Register); HLR (Home Location Register); AC (Authentication Centre), and EIR (Equip- ment Identity Register) (see Figure 1.4). This network is capable of providing all the basic services such as speech and data services up to 9.6 kbps, fax, etc. This GSM network also has an extension to the fixed telephony networks. GSM and VAS (Value Added Services): The next advancement in the GSM system was the addition of two platforms, called Voice Mail System (VMS) and the Short Message Service Centre (SMSC). The SMSC proved to be incredibly commercially successful, SO much SO that in some networks the SMS traffic constitutes a major part of the total traffic. Along with the VAS, IN (INtelligent services) also made its mark in the GSM system, with its advantage of giving the operators the chance to create a whole range of new services. Fraud mana