09 wcdma rno access failure problem analysis
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WCDMA Access Problems Analysis
ReviewReview
Access is associated with the call setup
success rate of the network. This KPI can be
optimized by means of “Call setup test” and the
consequent trouble-shooting based on access
failure analysis.
ObjectivesObjectives
� Be familiar with the access
procedure in UMTS
� Do analysis on access problems
independently
When finished this course,you will be able to:
Course ContentsCourse Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems
Case study
Definition of access failureDefinition of access failure
General originating call setup signaling flow:
Definition of access failureDefinition of access failure
General terminating call setup signaling flow:
Definition of access failureDefinition of access failure
Call setup succeeds when the call setup
phase is completed (when CC Connect is
received). If the call fails to reach the CC
Connect stage, it should be pegged as an
access failure .
Course ContentsCourse Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems
Case study
Access problem analysis processAccess problem analysis process
�� Preparation before AnalysisPreparation before Analysis
� Access problem analysis
methods
Preparation before analysis Preparation before analysis
Be familiar with the planning information which can be obtained from planning
reports;
Be familiar with history records of optimization;
Get the latest reliable summary sheet of the engineering parameters;
Get the latest configuration of radio parameters;
Obtain the network traffic statistics and the subscriber complaint information of
access.
Access problem analysis processAccess problem analysis process
� Preparation before Analysis
�� Access problem analysis Access problem analysis
methodsmethods
Access problem analysis methodsAccess problem analysis methods
General methods of access problem analysis:
Traffic statistics data analysisCustom complaint collection
Call setup test in specific area
Coverage analysis
Signaling analysis
Access problem analysis methodsAccess problem analysis methods
Traffic statistics data and custom complaint collection reveal problems exactly, further trouble-shooting can be carried out by call setup test. While for a pre-commercial or trial network, call setup test is the effective way.
Course ContentsCourse Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems
Case study
Common reasons for access problemsCommon reasons for access problems
�� RF reasonsRF reasons
� Radio Parameter Settings
� Other reasons
RF reasonsRF reasons
Poor coverage
Strong Uplink or downlink Interference
Common reasons for access problemsCommon reasons for access problems
� RF reasons
�� Radio Parameter SettingsRadio Parameter Settings
� Other reasons
Radio parameter settings Radio parameter settings
Improper threshold of Qqualmin and Qrxlevmin
Improper settings of access threshold
Inappropriate settings of preamble power ramp step and retransmission times
Inappropriate setting of adjacent cells
Inappropriate setting of synchronization parameters
Unsuitable power allocation rate for common channel
Unsuitable initial power of uplink and downlink dedicated channel
Unsuitable setting of uplink Initial SIR target value of dedicated channel
Common reasons for access problemsCommon reasons for access problems
� RF reasons
� Radio Parameter Settings
�� Other reasonsOther reasons
Other reasonsOther reasons
Data configuration problems
Access problems caused by cell load
Course ContentsCourse Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems
Case study
Case studyCase study
�� Access failure due to synchroniAccess failure due to synchroni--zaza
tion failuretion failure
� Access failure during RB setup
� Access failure during handover pr
ocess
� Access failure due to terminating
UE
Access failure due to synchronization failureAccess failure due to synchronization failure
Access failure location:
Access failure due to synchronization failureAccess failure due to synchronization failure
UE Txpower reaches maximum value 21 dBm during VP call setup. So this call
setup failure may be caused by Uplink synchronization failure:
Access failure due to synchronization failureAccess failure due to synchronization failure
UE does not send RRC Connection Setup Complete to RNC after receiving RRC
Connection Setup message from RNC :
Case studyCase study
� Access failure due to synchroni-za
tion failure
�� Access failure during RB setupAccess failure during RB setup
� Access failure during handover pr
ocess
� Access failure due to terminating
UE
Access failure during RB setupAccess failure during RB setup
Access failure location:
Access failure during RB setupAccess failure during RB setup
UE Tx power is very low and downlink pilot Ec is high before access failure,butEc/Io is not very good :
Access failure during RB setupAccess failure during RB setup
The cause of call setup failure is Requested circuit/channel not available:
Access failure during RB setupAccess failure during RB setup
RNC didn’t receive RB
Setup Complete message
after it has sent RB Setup
message to UE. Timeout of
RNC is reached after 1.5s:
Case studyCase study
� Access failure due to synchroni-za
tion failure
� Access failure during RB setup
�� Access failure during handover prAccess failure during handover pr
ocess ocess
� Access failure due to terminating
UE
Access failure during handover processAccess failure during handover process
Access failure location (Scanner Rscp ):
Access failure during handover processAccess failure during handover process
ScannerEc/I0 :
Access failure during handover processAccess failure during handover process
Scanner BestServer :
Access failure during handover processAccess failure during handover process
During access process, UE Txpower is rising rapidly :
Access failure during handover processAccess failure during handover process
And the downlink Bler reaches 100%:
Access failure during handover processAccess failure during handover process
UE report the measurement of cell Sc508 which request the active set update:
Access failure during handover processAccess failure during handover process
The report was
received properly and
“RRC_ACTIVE_UPDATE”
was sent as response
while UE didn’t received it
which results in the
access failure:
Access failure during handover processAccess failure during handover process
Let’s turn to the performance of the terminating UE. During the access process, the measurements from the terminating UE were not satisfactory either:
Access failure during handover processAccess failure during handover process
Access failure during handover processAccess failure during handover process
While the radio links
hold on till successful
handover is completed:
Access failure during handover processAccess failure during handover process
Then the originating UE loses connection to the network and access released
where the cause is “destination out of order” from the signal traced by the terminating UE:
Case studyCase study
� Access failure due to synchroni-za
tion failure
� Access failure during RB setup
� Access failure during handover pr
ocess
�� Access failure due to terminating Access failure due to terminating
UEUE
Access failure due to terminating UEAccess failure due to terminating UE
Access failure location (UE Ec/I0 ):
Access failure due to terminating UEAccess failure due to terminating UE
The coverage is not bad where the UE originates the VP access:
Access failure due to terminating UEAccess failure due to terminating UE
CN send “disconnect” message with the cause “bearer capability not authorized”
before access failure:
Access failure due to terminating UEAccess failure due to terminating UE
setup signaling procedure for RRC and RAB have already finished. The cause of disconnect is the same:
Access failure due to terminating UEAccess failure due to terminating UE
The reason is: we use two mobile to test video phone, for the originating call mobile camped in 3G network, but the terminating call mobile camped in 2G network that moment, so video call setup failed, the missing signaling of terminating UE can also explain it:
SummarySummary
Access process is complicated since different devices are
involved and scenario varies. Careful study from signal
distribution to signaling procedure makes things easy.
Examples above are derived from tests carried out before,
which give general idea of trouble shooting, advanced
researches will be supplemented. .
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