cbcch common bcch ppt
DESCRIPTION
common BCCHTRANSCRIPT
CBCCH
Common BCCH
• Benefits– Improved trucking gain,
(improve blocking probability)
– Reduced frequency used– Reduced number of cell,
reduced LAC, reduced paging
– Reduced neighboring cells, improve performance due to decreased handover
Restrictions• BCCH on Comon BCCH system must be the same band throughout the whole network
• There can be only 31 frequency in adjacent cell and BA list
• Only 5 strongest neighbours are included in the adjacent cell measurement
• Initial SDCCH channel for call setup is always allocated in the BCCH segment, since FACCH setup take place as a response to an SDCCH allocation request, FACCH has the same restriction as SDCCH
• Dynamic SDCCH can be utilised only in the BCCH frequency band.
DCS
GSM
Problem on CBCCH
Difference cell coverage difference radio attenuation between DCS & GSM
DCS
GSM
Problem on CBCCH
CCCH problem
DCSGSM
Parameter_1 (NBL)
NBL = NonBCCH Layer offsetSuggested value = 10
DCS GSM
Parameter_2 (LAR)
LAR = non BCCH layer access threshold
Average_Rxlev_DL – NBL >= LAR
DCS GSM
Parameter_3 (LER)
LER = non BCCH layer Exit threshold
Parameter_4(LSEG)
BTSloadInseg + ( (100 – BTSloadInseg ) / 2 ) = HO triggered
Example :
BTSloadInseg GSM = 20
BTSloadInseg DCS = 80
20 % 60 %
80 %
TCH allocation priority to DCS
Handover triggered
Parameter_5 (extend SD)
ISS = guard time for attempting an SDCCH handover from the BCCH BTS resource layer to another resource layer in a segment. (BSC level)
ESD = enable SDCCH handove (BTS level)
Thank you
by dimas