# How is the CSSR formula ?
CSSR_w/o_block = ImmAss SR x SSS Proc SR x Ass TCH
ImmAss SR = NSUCCHPC(APSD,CRSD,ECSD,OCSD NSUCCHPC(SMTCSD)
ImAss Phase
SSS Proc Phase
SSS Proc SR =
TASSAT (F,H) NSUCCHPC(APSD,CRSD,ECSD,O
TCH Assignment Phase
TCH Ass SR = TASSSUCC(F,H)+TASSFAIL(NRF,NRH)+SINTHINT(DR)+SU
SSS Proc SR x Ass TCH
CHPC(APSD,CRSD,ECSD,OCSD)-
TASSAT (F,H) SUCCHPC(APSD,CRSD,ECSD,OCSD)-
L(NRF,NRH)+SINTHINT(DR)+SUINBHDO(DR)+SUOISHDO(DR)
Analysis # What factor can influence within this phase ?
Phase I : ATIMASCA - SUIMASCA Loss probability : a. No SDCCH available - High number of request - Lack of SDCCH resources - Over idle coverage b. Transmission problem - flicker transmission - not LOS transmission (obstacle) - unnecessary cabling on DDF pan - 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, b d. Radio Interface problem - frequency interference - unbalance UL & DL due to improp - unnecessary db setting
Phase II : SUIMASCA - NSUCCHPC Loss probability : a. Transmission problem - see point b on phase I explanation b. AGCH overload - see statistic meas : difference bet - if the differences > 0 c. Radio Interface problem MS might be due to MS used 'phant - see point d on phase I explanation d. HW problem & wrong installation o - see point c on phase I explanatio
Action : ATIMASCA - SUIMASCA
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
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
a. SDCCH capacity overhand - adding SDCCH TS within - more selective on filterin (set RXLEVAMI, RACHBT - reduce the (over) covera b. Radio Interface quality im - frequency retune - hopping optimization (ho - power control mechanis - no over coverage for pre - antenna optimization (an c. HW problem & wrong inst - changing any broken mo - fix any wrong installation d. Transmission problem ov - transmission replan by T - fix any transmission cab
II : SUIMASCA - NSUCCHPC
smission problem - Abis interface -> messages loss (IMASS, ESTIN) between BTS and BSC point b on phase I explanation
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
a. Solving AGCH overload b - adding block AGCH rese b. Radio Interface quality im - see point b on explanatio c. HW problem & wrong inst - see point c on explanatio d. Transmission problem ov - 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
# What kind of process (procedures) occurred within this phase ?
- SSS Procedure Phase start from CMS REQ - 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
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 Description 1 T200 expired 2 unsolicited DM response, multi frame established state
When BTS has sent layer layer 2 acknowledgement from MS (reasons
MS has sent a Um layer
BTS has detected irregularities in the Um lay
NFRLSDCC (1,3)
3 4 5 6 7 8 9
sequence error T_MSRFPCI expired distance limit exceeded handover access failure radio link failure remote transcoder failure unspecified (others)
BTS has detected irregularities in the Um lay T_MSRFPCL is not adjustable on database
MS-BTS distance exceeds the threshold Failure on HO SDCCH-SDCCH ; Causes : Ra Radio Problems (interference, coverage, HW&
TRACK/TRAU module failure, COBA/CU failu
ase start from CMS REQ message sent from BSC towards MSC, and stop after receipt of ASS REQ. y seized within this phase. re events are performed during this phase, that are authentication, ciphering, IMEI check, TMSI re-allocation, setup message, and digit translation , loss analysis can be got from SDCCH drop counter (NRLFSDCC_1-9)
IMEI Check & TMSI Reallocation Procedure
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 receiving acknowledgement from MS (reasons : any radio problems may exist) until T200 timer expired, then the connections are dropped. 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’
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 on HO SDCCH-SDCCH ; Causes : Radio Problems (interference, coverage, oblems (interference, coverage, HW&Installation)
TRAU module failure, COBA/CU failure, wrong DB setting (TTRAU > T8 , TTRAU > T10, TTRAU = TSYNC => This setting is for ensuring that a signaling failure (T
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 - Actually TCH Blocking influence this phase formula - There is still loss probability on - Any TCH Assignment Failure will incremen
# TASSFAIL causes ?
TASSFAIL (1,30)
Counter
Sub Counter for CHAN TYPE TCH/F TCH/H 6 11 7 12 8 13 9 14 10 15
Description Radio Interface Message Failure Radio Interface Failure - reversion to old channel No radio resource available Directed Retry Al Other Cause
Counted as TCH Assignment Success on KPI CSSR Formula HCPT -> see shet formula
TASSFAIL due to Radio Interface Message Failure
ASS CMD message is lost, may be c - Radio Interface problem : Interferen - unnecessary
TASSFAIL due to Radio Interface Failure - reversion to old channel
SABM message is lost while using FA - Radio Interface problem : Interferen - unnecessary T
Directed Retry HO ACCESS - Radio Interface problem : Interference
Directed Retry HO ACCESS - Radio Interface problem : Interference
TASSFAIL due to Directed Retry
When Directed Retry
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 Suc
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 y TCH Assignment Failure will increment TASSFAIL counter in BSC
TCH Assignment Success on KPI CSSR > see shet formula
message is lost, may be caused by : Radio Interface problem : Interference, Coverage, HW Failure / Wrong Installation unnecessary T10 setting
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
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
Directed Retry HO is performed, TASSFAIL(9) counter will be incremented
message sending
counted as TCH Assignment Success -> see on sheet
SS CMD message
DB Parameter Related DB Parameter
Object
RXLEVAMI
BTS
RACHBT
BTS
NBLKACGR
BTS
T200
BTS
IERCHOSDCCH
BTS
IRACHOSDCCH
BTS
EISDCCHHO
BTS
TTRAU
BTS
TSYNC
BTS ; TRAU
T10
BSC
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 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 attempt SDCCH, more HO fail possibility due to FACCH Threshold for the signal level on RACH rejected. Specifies the number of CCCH blocks to be reserved in CCCH TS for AGCH ; Increase => Add CCCH blocks to be reserved for AGCH, MAINBCCH provides 9 CCCH blocks decrease blockes to be reserved for PCH. (shared between PCH and AGCH) Decrease => vica versa from statement above. Should be attended that this timer setting can much reduce drop LAPDm timer 200 ; determines the call / signalling conection, but can also deliver non realistic waiting time for a layer 2 frame image of the actual radio interface quality (less drop but poor acknowledgement quality). So need proper adjustment as trade off Set True => activate intercell SDCCH HO, more SDCCH usage, more possibility on SDCCH fail/drop. Set FALSE => disabling To enable / disable intercell SDCCH intercell SDCCH HO, less SDCCH usage, less possibility on HO SDCCH fail/drop Set True => activate intercell SDCCH HO, more SDCCH usage, more possibility on SDCCH fail/drop. Set FALSE => disabling To enable / disable intracell SDCCH intercell SDCCH HO, less SDCCH usage, less possibility on HO SDCCH fail/drop Set True => activate intercell SDCCH HO, more SDCCH usage, more possibility on SDCCH fail/drop. Set FALSE => disabling To enable / disable interBSC SDCCH intercell SDCCH HO, less SDCCH usage, less possibility on HO SDCCH fail/drop Timer supervision start from sending Must set to proper value ; Must follow the rule : TTRAU > T8, UL TRAU frame and stop when first DL TTRAU > T10, TTRAU = TSYNC for ensuring signalling failure TRAU frame received by BTS is 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 haven't correctly received, and reset TSYNC setting in TRAU object when correct frame is received again. Time to return assignment complete Must be set to proper value ; In the case of call setup, the (ASS CMP) message. Start from setting must follow the rule : T10 < TTRAU sending message ASS CMD and stop when ASS CMP received.
