# How is the CSSR formula ?
CSSR_w/o_block = ImmAss SR x SSS Proc SR x Ass TCH SR
ImmAss SR =
ImAss Phase
SSS Proc Phase
NSUCCHPC(APSD,CRSD,ECSD,OCSD)ATIMASCA(APSD,CRSD,ECSD,OCSD)-NS
SSS Proc SR =
TASSAT (F,H) NSUCCHPC(APSD,CRSD,ECSD,OC NSUCCHPC(SMTCSD)
TCH Assignment Phase
TCH Ass SR = TASSSUCC(F,H)+TASSFAIL(NRF,NRH)+SINTHIN +SUOISHDO(DR) TASSAT (F,H
SS Proc SR x Ass TCH SR
HPC(APSD,CRSD,ECSD,OCSD)-NSUCCHPC(SMTCSD) CA(APSD,CRSD,ECSD,OCSD)-NSUCCHPC(SMTCSD)
TASSAT (F,H) UCCHPC(APSD,CRSD,ECSD,OCSD)D)
H)+TASSFAIL(NRF,NRH)+SINTHINT(DR)+SUINBHDO(DR) TASSAT (F,H)
Analysis # What factor can influence within this phase ?
Phase I : ATIMASCA - SUIMASCA Loss probability : a. No SDCCH available -> SDCCH attem - High number of request - Lack of SDCCH resources - Over idle coverage b. Transmission problem - Abis interfa - flicker transmission - not LOS transmission (obstacle) -> - unnecessary cabling on DDF pane - problems on COBA/COSA module c. HW problem & wrong installation on - high VSWR - broken module - untight connector - broken cable/feeder ; high loss - fabrication faulty : BTS mainboard - cell inversion : antenna, feeder, ba d. Radio Interface problem -> message - frequency interference - unbalance UL & DL due to imprope - unnecessary db setting
Phase II : SUIMASCA - NSUCCHPC Loss probability : a. Transmission problem - Abis interfa - see point b on phase I explanation b. AGCH overload - see statistic meas : difference betw - if the differences > 0 means there a c. Radio Interface problem -> message MS might be due to MS used 'phanto - see point d on phase I explanation d. HW problem & wrong installation on - see point c on phase I explanation
: ATIMASCA - SUIMASCA robability : DCCH available -> SDCCH attempt meeting blocked h number of request k of SDCCH resources er idle coverage smission problem - Abis interface -> messages loss (CHNAV, CHNAK) between BTS and BSC ker transmission LOS transmission (obstacle) -> wrong transmission planning necessary cabling on DDF panel oblems on COBA/COSA module problem & wrong installation on BTS -> bad processing/failure, un-received/sent of messages toward BTS/MS h VSWR oken module ight connector oken cable/feeder ; high loss rication faulty : BTS mainboard, module slot l inversion : antenna, feeder, backplane, semirigid, wrong HW db creation o Interface problem -> messages loss between MS and BTS quency interference balance UL & DL due to improper coverage (overshoot or lack of coverage), contour factor necessary db setting
II : SUIMASCA - NSUCCHPC robability : smission problem - Abis interface -> messages loss (IMASS, ESTIN) between BTS and BSC point b on phase I explanation H overload statistic meas : difference between TACCBPRO (2) - NACSUCPR(2) he differences > 0 means there are AGCH overload o Interface problem -> messages (IMASS, SABM, CMSREQ) loss between MS and BTS ; no SABM sent to BTS by might be due to MS used 'phantom' RACH when send CHNREQ point d on phase I explanation problem & wrong installation on BTS -> bad processing/failure, un-received/sent of messages toward BTS/MS e point c on phase I explanation
Action
a. SDCCH capacity overhand - adding SDCCH TS within - more selective on filtering (set RXLEVAMI, RACHBT - reduce the (over) coverag b. Radio Interface quality imp - frequency retune - hopping optimization (ho - power control mechanism - no over coverage for prev - antenna optimization (ant c. HW problem & wrong insta - changing any broken mo - fix any wrong installation d. Transmission problem ove - transmission replan by T - fix any transmission cabl
a. Solving AGCH overload by - adding block AGCH reser b. Radio Interface quality imp - see point b on explanatio c. HW problem & wrong insta - see point c on explanatio d. Transmission problem ove - see point d on explanatio
a. SDCCH capacity overhandling might be done by : - adding SDCCH TS within TRX - more selective on filtering MS for accessing network => only MS with good UL level can access the cell and get RACH (set RXLEVAMI, RACHBT) - reduce the (over) coverage by tilting adjustment b. Radio Interface quality improvement : - frequency retune - hopping optimization (hop mode, hop activation, HSN, maio, mall lists - check it all) - for dedicated mode - power control mechanism (threshold, step size) - for dedicated mode - no over coverage for preventing interfering with others => done by coverage adjustment - antenna optimization (ant type with proper beamwidth, ant height, azimuth, tilt) c. HW problem & wrong installation fixing : - changing any broken module/equipment - fix any wrong installation d. Transmission problem overhandling : - transmission replan by TNP (if no LOS) by antenna μw optimization (height), transmission re-route - fix any transmission cabling/connection problem and module failure
a. Solving AGCH overload by : - adding block AGCH reserved => set NBLKACGR, but must consider PCH reserved reducing impact by increasing this AGCH capacity b. Radio Interface quality improvement : - see point b on explanation above c. HW problem & wrong installation fixing : - see point c on explanation above d. Transmission problem overhandling : - see point d on explanation above
capacity
# What kind of process (procedures) occurred within this phase ?
- SSS Procedure Phase start from CMS REQ message se - SDCCH are already seized within this phase. - Many SSS procedure events are performed during this p procedures. - From BSS point of view, loss analysis can be got from S
Authentication Process
Ciphering Process
# How can the SDCCH connection become drop ?
What may be the most drop reason can be known from mesurement counter NRFLSDCC [1-9] :
NFRLSDCC (1,3)
Counter
Sub Counter 1 2 3 4 5 6 7 8 9
Description T200 expired unsolicited DM response, multi frame established state sequence error T_MSRFPCI expired distance limit exceeded handover access failure radio link failure remote transcoder failure unspecified (others)
When BTS has sent layer 2 message in ackn receiving layer 2 acknowledgement from MS dropped.
MS has sent a Um layer 2 (LAPDm) message state’ BTS has detected irregularities in the Um laye T_MSRFPCL is not adjustable on database
MS-BTS distance exceeds the threshold EXCDIST Failure on HO SDCCH-SDCCH ; Causes : Ra HW&Installation) Radio Problems (interference, coverage, HW&
TRACK/TRAU module failure, COBA/CU failure
ase start from CMS REQ message sent from BSC towards MSC, and stop after receipt of ASS REQ. y seized within this phase. ure events are performed during this phase, that are authentication, ciphering, IMEI check, TMSI re-allocation, setup message, and digit translation
f view, loss analysis can be got from SDCCH drop counter (NRLFSDCC_1-9)
IMEI Check & TMSI Reallocation Procedure
Ciphering Pro Setup Message & Digit Translation Procedure
BTS has sent layer 2 message in acknowledge mode (that is I frame message : ASS CMD) N200+1 times to the MS without ng layer 2 acknowledgement from MS (reasons : any radio problems may exist) until T200 timer expired, then the connections are d. sent a Um layer 2 (LAPDm) message DM (Mode) to the BTS while the BTS-MS communication is in ’multiple frame stablished
s detected irregularities in the Um layer 2 (LAPDm) flow control functions (wrong message sequence) useds in’acknowledged mode’ FPCL is not adjustable on database
S distance exceeds the threshold ST on HO SDCCH-SDCCH ; Causes : Radio Problems (interference, coverage, tallation)(interference, coverage, HW&Installation) oblems
TRAU module failure, COBA/CU failure, wrong DB setting (TTRAU > T8 , TTRAU > T10, TTRAU = TSYNC => This setting is for ensuring that a signaling failure (T8 and T10)
at a signaling failure (T8 and T10) is detected before transcoder failure (TSYNC and TTRAU)
# How is this phase ?
- TCH Assignment Phase start after receiving - BSS Counter start from TASSATT and end b - Actually TCH Blocking influence this phase, formula - There is still loss probability on SDCCH Dro - Any TCH Assignment Failure will increment
# TASSFAIL causes ?
TASSFAIL (1,30)
Counter
Sub Counter for CHAN TYPE Description TCH/F TCH/H 6 11 Radio Interface Message Failure 7 12 Radio Interface Failure - reversion to old channel 8 13 No radio resource available 9 14 Directed Retry 10 15 Al Other Cause
Counted as TCH Assignment Success on KPI CSS Formula HCPT -> see shet formula
TASSFAIL due to Radio Interface Message Failure
ASS CMD message is lost, may be ca - Radio Interface problem : Interferenc - unnecessary T10 setting
TASSFAIL due to Radio Interface Failure - reversion to old channel
SABM message is lost while using FA - Radio Interface problem : Interferenc - unnecessary T10 setting
Directed Retry HO ACCESS message - Radio Interface problem : Interference
TASSFAIL due to Directed Retry
When Directed Retry HO is perf
H Assignment Phase start after receiving assignment request (ASS REQ) message on BSC from MSC, and stop after assignment complete (ASS COM) message sending S Counter start from TASSATT and end by TASSSUCC ually TCH Blocking influence this phase, BUT on KPI Formula HCPT for CSSR, TCH blocking is excluded from TCH assignment failure, but counted as TCH Assignment Succ ula ere is still loss probability on SDCCH Drop with T200 expiry reason within this phase => check if any radio problem which cause loss of ASS CMD message TCH Assignment Failure will increment TASSFAIL counter in BSC
s TCH Assignment Success on KPI CSSR CPT -> see shet formula
ASS CMD message is lost, may be caused by : - Radio Interface problem : Interference, Coverage, HW Failure / Wrong Installation - unnecessary T10 setting
SABM message is lost while using FACCH, assignment TCH fail and back to SDCCH , may be caused by : - Radio Interface problem : Interference, Coverage, HW Failure / Wrong Installation - unnecessary T10 setting
Directed Retry HO ACCESS message is lost while using FACCH, assignment TCH fail and back to SDCCH on old cell , may be caused by : - Radio Interface problem : Interference, Coverage, HW Failure / Wrong Installation
When Directed Retry HO is performed, TASSFAIL(9) counter will be incremented
(ASS COM) message sending counted as TCH Assignment Success -> see on sheet
SS CMD message
DB Parameter Related DB Parameter RXLEVAMI
Object BTS
Description Minimum received level at the MS required for access to the network
Value Setting Trade Off Increase => Idle coverage shrinking, less attempt SDCCH Decrease => Idle coverage enlargement, more attempt SDCCH
RACHBT
BTS
NBLKACGR
BTS
Increase => Low UL level can access RACH, more attempt SDCCH, less HO fail possibility due to FACCH rejected. Decrease => Only good UL level can access RACH, less Threshold for the signal level on RACH attempt SDCCH, more HO fail possibility due to FACCH rejected. Increase => Add CCCH blocks to be reserved for AGCH, Specifies the number of CCCH blocks decrease blockes to be reserved for PCH. to be reserved in CCCH TS for AGCH ; Decrease => vica versa from statement above. MAINBCCH provides 9 CCCH blocks (shared between PCH and AGCH)
BTS
LAPDm timer 200 ; determines the waiting time for a layer 2 frame acknowledgement
Should be attended that this timer setting can much reduce drop call / signalling conection, but can also deliver non realistic image of the actual radio interface quality (less drop but poor quality). So need proper adjustment as trade off
To enable / disable intercell SDCCH HO
Set True => activate intercell SDCCH HO, more SDCCH usage, more possibility on SDCCH fail/drop. Set FALSE => disabling intercell SDCCH HO, less SDCCH usage, less possibility on SDCCH fail/drop
To enable / disable intracell SDCCH HO
Set True => activate intercell SDCCH HO, more SDCCH usage, more possibility on SDCCH fail/drop. Set FALSE => disabling intercell SDCCH HO, less SDCCH usage, less possibility on SDCCH fail/drop
To enable / disable interBSC SDCCH HO
Set True => activate intercell SDCCH HO, more SDCCH usage, more possibility on SDCCH fail/drop. Set FALSE => disabling intercell SDCCH HO, less SDCCH usage, less possibility on SDCCH fail/drop
T200
IERCHOSDCCHBTS
IRACHOSDCCHBTS
EISDCCHHO
BTS
TTRAU
BTS
TSYNC
BTS ; TRAU
T10
BSC
Timer supervision start from sending UL Must set to proper value ; Must follow the rule : TTRAU > T8, TRAU frame and stop when first DL TTRAU > T10, TTRAU = TSYNC for ensuring signalling failure is TRAU frame received by BTS detected before transcoder failure Timer supervision start of TRAU frame Must be set to proper value ; Must follow the rule : TSYNC = handling. Start when 3 DL TRAU frame TTRAU ; TSYNC setting in BTS object must be same with TSYNC haven't correctly received, and reset setting in TRAU object when correct frame is received again.
Time to return assignment complete (ASS CMP) message. Start from sending message ASS CMD and stop when ASS CMP received.
Must be set to proper value ; In the case of call setup, the setting must follow the rule : T10 < TTRAU
