# 8.5 Combined multiple access systems

## Examples of FDMA/TDMA combinations

We have already seen some examples of digital communication systems exploiting combinations of multi-user access techniques. GSM, although primarily a TDMA system, requires several 200 kHz frequency channels (each carrying eight time slots) in order to provide a practical high capacity cellular system and can thus be viewed as an FDMA system also. The TETRA (Trans European Truncked Radio Access) system exploits a three time slot TDMA structure with FDMA channels spaced at 25 kHz spacing. |