17-04-2014, 04:42 PM
GSM infrastructure
GSM infrastructure.ppt (Size: 108.5 KB / Downloads: 175)
Base Transceiver Station
Controls the radio link
encryption
error control
signal strength
1 - 6 duplex carriers, for example:
two layers
120o sectors
(6+8)*3 = 42 voice calls
Cost ~ 100 – 200 k$
Base Station Controller
communication with the mobile terminal
local hand-over
voice codecs
carrier allocation
paging to terminals
talks to the MSC
serves up to 40 BTSs
could be co-located with MSC
Mobile Swicthing Center
Mobility management
identifies and authenticates
locates
switches between BSCs
Handover to other MSCs
64 kbps regular voice channels
Control Channels
Broadcast
Frequency correction: to synchronize (FCCH)
Broadcast control: this is me, these are my neighbours (BCCH)
Common control
Paging: to notify a mobile station (PCH)
Random access: for the mobile to request service (RACH)
Access grant: reply with assigned dedicated control channel (AGCH)
Dedicated control
Standalone dedicated control: used during call set-up, SMS etc (SDCCH)
Slow associated control: power, time etc (SACCH)
Fast associated control: handover etc, uses the TCH (FACCH)
Cell broadcast: cell broadcast