GSM System
Global System for Mobile Communication (GSM) is a communication system developed by a working group affiliated to the European Telecommunications Standards Institute (ETSI). GSM was first used in Finland in the world. Finland’s geographical structure, weather conditions, distribution of residential areas have prepared a suitable ground for the development of a wireless communication system [1].
GSM, which can be created in about 10 years and with billions of dollars of expenditure, was accepted as a standard by 30 European countries in 1987. The first GSM standards were published in 1990. Although it started as a European standard, GSM has become a world standard by adopting it worldwide in a short time. ANSI (American National Standards Institute — American National Standards Institute) stepped in to use these standards in the USA and GSM standards were published in the USA and linked to their applications [2].
The primary goal of mobile phone networks such as GSM is to allow subscribers with mobile stations to make phone calls from anywhere. In order to achieve this, main functions such as call management, call processing, radio management, mobility management, pricing and security must be fulfilled [1].
The GSM network consists of the network switching subsystem (NSS; Network Switching Subsytem) and the base station subsystem (BSS; Base Station Subsystem). NSS handles call handling, mobility management, security and pricing. BSS manages functions related to the radio system for mobile stations [1].
Although GSM is digital and brings many innovations in terms of radio access techniques it uses, it is not the last point reached, but it is accepted as a study that will provide transition to more advanced and global systems [3].
Transactions related to subscribers are divided into many sections. Permanent location register (HLR; Home Location Register), visitor location register (VLR; Visitor Location Register), authentication center (AUC; Authentication Center), device identity register (EIR; Equipment Identity Register). EIR, HLR and VLR are databases that contain information of subscribers.
HLR is a database that holds all kinds of data for a particular operator, such as where the cell phone is, subscriber identity information.
VLR temporarily keeps a copy of the HLR information of the subscribers served within a certain MSC. Copying subscriber information from HLR to VLR is a part of mobility management in the network.
AUC manages all security operations.
EIR is the database where the list of mobile stations in the network is kept. Here, all mobile stations have an international mobile device ID (IMEI; International Mobile Equipment Identity) [1].
One of the most useful features of GSM is that users can make calls (roaming) from different countries with the same line. All GSM standards use cellular networks, and GSM technology has the ability to switch between cells.
REFERENCES
[1] Biroğul, S., “GSM şebekelerinde frekans planlamasının veri füzyonu ile gerçekleştirilmesi”, Doktora Tezi, Gazi Üniversitesi Fen Bilimleri Enstitüsü, Ankara, 39–40 (2008).
[2] Arslan, S., “GSM 900 baz istasyon servis sayılarının simülasyon ve amaç programlama tekniklerinin kullanılması” Yüksek Lisans Tezi, Gazi Üniversitesi Fen Bilimleri Enstitüsü, Ankara, (2000).
[3] Dayak, M.E., “3. nesil gezgin telefonlar üzerinde multimedya destekli güvenlik artırım tekniklerinin araştırılması”, Kahramanmaraş Sütçü İmam Üniversitesi Fen Bilimleri Enstitüsü, Kahramanmaraş, 4 (2007).
