06-07-2012, 04:06 PM
GLOBAL SYSTEM OF MOBILE COMMUNICATIONS
GLOBAL SYSTEM OF MOBILE .ppt (Size: 1.71 MB / Downloads: 127)
Base Station Controller
Wireless link distribution between MS and BTS
Communication connection and disconnection
MS location, handover and paging
Voice encoding, transecoding (TC), rate, adaptation,
The operation and maintenance functions of BSS.
Cell Mode Layout
Omni-directional cell
Adopt omni-directional antenna,
the overall directional propagation characteristic is the same.
Directional cell
In general, cell with multi-sector is in common use. Every directional cell adopts directional antenna.
Traffic Measurements
Erlang :
the traffic intensity of a totally occupied channel (i.e. the call hour of a unit hour or the call minute of a unit minute). For example, the traffic of a channel occupied for 30 minutes in an hour is 0.5 Erlang)
GOS:
defined as the probability of call blocking or the probability when the call delay time is longer than a given queuing time.
Frequency Hopping
Reason:
counteract Rayleigh Fading
scatter interference among multiple calls
Types:
Base band frequency hopping
keeps the transmission and receiving frequency of each carrier unit unchanged, but merely sends FU transmission data to different carrier units at different FN moments.
radio frequency hopping
controls the frequency synthesizer of each transceiver, making it hop according to different schemes in different time slots.