GSM Mobile Network – mobile network of 2nd generation
GSM system and its standards

Basic applications are implemented at 900 MHz band in GSM. Increase of traffic has led to development of other versions with multiple frequency bands. Thus, there are three standards, which differ primarily in used frequency range and number of allocated channels:

- GSM 900 – frequency band at 900 MHz, maximum capacity 2×124 channels, bandwidth of 2×25 MHz
- GSM 1800 – frequency band at 1800 MHz, maximum capacity 2×374 channels, bandwidth of 2×75 MHz
- GSM 1900 – frequency band at 1900 MHz, maximum capacity 2×298 channels, bandwidth of 2×75 MHz

The later versions of GSM system, that is GSM 1800 and GSM 1900, are sometimes referred to as DCS (Digital Communication System or Digital Cellular System) systems.

Allocation of frequency bands used by GSM 1800 in the European continent is shown in the following figure.

Frequency bands used by GSM 1800 systems and their separation

GSM 1800 system does not bring any major technological innovations but allows you to meet others subscribers interested in mobile communications, especially in cities. The system allows you to create either standalone network or network cooperating with the former GSM 900. Usually, there are combined macrocells of GSM 900 with the microcells of GSM 1800, which aim is to provide the services in areas with high concentrations of users (such as shopping centres or downtowns). However, the two-way (or dual mode) MSs have to be utilized in order to exploit both frequencies.