Downlink 925 – 960 and 1805 – 1880 MHz
Uplink 890 – 915 and 1710 – 1885 MHz
Duplex spacing 45 bzw. 95 MHz
The Global System for Mobile Communications (GSM) was developed by the Groupe Spécial Mobile (“GSM”). It is the standard for second generation (2G) mobile communications, being the first fully digital network to supplant the first generation analog systems. It is worldwide the most common mobile communications standard. Higher data transfer rates have been made possible by its further development, EDGE (enhanced data rates for GSM evolution) using an additional modulation method.
Combination of frequency and time multiplexing. Frequency multiplex: MC (multi-carrier), RF channels 270 kHz wide, channel spacing 200 kHz (adjacent channels often unusable depending on level). Time multiplex: TDMA (time division multiple access), frame length 4.62 ms with 8 timeslots of 576.56 µs; 1 burst 546 µs, guard interval 30.4 µs. The bursts are GMSK modulated (Gaussian minimum shift keying with constant amplitude); 8PSK modulation is used for EDGE.