GSM (Global System for Mobile communication) is a digital mobile telephone system that is widely used in Europe and other parts of the world. GSM uses a variation of Time Division Multiple Access (TDMA) and is the most widely used of the three digital wireless telephone technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1,800 MHz frequency band.
GSM is the de facto wireless telephone standard in Europe. GSM has over one billion users worldwide and is available in 190 countries. Since many GSM network operators have roaming agreements with foreign operators, users can often continue to use their mobile phones when they travel to other countries.
| Mobile Frequency Range | Rx: 925-960; Tx: 880-915 |
| Multiple Access Method | TDMA/FDM |
| Duplex Method | FDD |
| Number of Channels | 124 (8 users per channel) |
| Channel Spacing | 200kHz |
| Modulation | GMSK (0.3 Gaussian Filter) |
| Channel Bit Rate | 270.833Kb |
