Thomas Kunz
Systems and Computer Engineering
33
GSM: Radio Transmission Aspects
–spectrum
allocation
nin 1978 Europe allocated 2x25 MHz in the 900 MHz range
for mobile communications
–890
- 915 MHz for the uplink (mobile station to base station)
–935
- 960 MHz for the downlink (base station to mobile station)
ntop 10 MHz in each band reserved for a pan-European
mobile system, since band was also used by national analog
systems
–multiple
access:
nGSM divides allocated bandwidth into carriers spaced
200 kHz apart, starting 200 kHz from the edge - maximum of
124 carriers in GSM900, 374 carriers in DCS1800 (2x75 MHz allocation)
nTDMA divides time on each carrier frequency into burst periods
lasting 15/26 (0.577) ms