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Owj104103 Wcdma Access Analysis Issue1.0
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Wireless Curriculum Development SectionWireless Curriculum Development Section
ISSUEISSUE
WCDMA Access AnalysisWCDMA Access Analysis
1.01.0
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Overview
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.
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Objectives
Be familiar with the access procedure in UMTS
Do analysis on access problems independently
When finished this course,you will be able to:
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Course Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems
Case study
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Definition of access failure
General originating call setup signaling flow:
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Definition of access failure
General terminating call setup signaling flow:
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Definition 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 .
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Course Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems
Case study
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Access problem analysis process
Preparation before AnalysisPreparation before Analysis
Access problem analysis
methods
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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.
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Access problem analysis process
Preparation before Analysis
Access problem analysis Access problem analysis
methodsmethods
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Access problem analysis methodsGeneral methods of access problem analysis:
Traffic statistics data analysisCustom complaint collection
Call setup test in specific area
Coverage analysis
Signaling analysis
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Access 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.
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Course Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems
Case study
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Common reasons for access problems
RF reasonsRF reasons
Radio Parameter Settings
Other reasons
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RF reasons
Poor coverage
Strong Uplink or downlink Interference
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Common reasons for access problems
RF reasons
Radio Parameter SettingsRadio Parameter Settings
Other reasons
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Radio parameter settings
Improper threshold of Qqualmin and Qrxlevmin Improper settings of access threshold Inappropriate settings of preamble power ramp step and ret
ransmission 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 ch
annel Unsuitable setting of uplink Initial SIR target value of dedica
ted channel
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Common reasons for access problems
RF reasons
Radio Parameter Settings
Other reasonsOther reasons
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Other reasons
Data configuration problems
Access problems caused by cell load
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Course Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems
Case study
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Case study
Access failure due to synchroni-Access failure due to synchroni-
zation failurezation failure
Access failure during RB setup
Access failure during handover
process
Access failure due to terminating
UE
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Access failure due to synchronization failure
Access failure location:
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Access 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:
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Access failure due to synchronization failure
UE does not send RRC Connection Setup Complete to RNC after receiving RRC Connection Setup message from RNC :
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Case study
Access failure due to synchroni-
zation failure
Access failure during RB setupAccess failure during RB setup
Access failure during handover
process
Access failure due to terminating
UE
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Access failure during RB setup
Access failure location:
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Access failure during RB setup
UE Tx power is very low and downlink pilot Ec is high before access failure,but Ec/Io is not very good :
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Access failure during RB setup
The cause of call setup failure is Requested circuit/channel not available:
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Access 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:
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Case study
Access failure due to synchroni-
zation failure
Access failure during RB setup
Access failure during handover Access failure during handover
process process
Access failure due to terminating
UE
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Access failure during handover process
Access failure location (Scanner Rscp ):
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Access failure during handover process
ScannerEc/I0 :
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Access failure during handover process
Scanner BestServer :
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Access failure during handover process
During access process, UE Txpower is rising rapidly :
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Access failure during handover process
And the downlink Bler reaches 100%:
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Access failure during handover process
UE report the measurement of cell Sc508 which request the
active set update:
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Access failure during handover process
The report was
received properly
and
“RRC_ACTIVE_UPD
ATE” was sent as
response while UE
didn’t received it
which results in the
access failure:
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Access 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:
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Access failure during handover process
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Access failure during handover process
While the
radio links hold
on till successful
handover is
completed:
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Access 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:
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Case study
Access failure due to synchroni-
zation failure
Access failure during RB setup
Access failure during handover
process
Access failure due to terminating Access failure due to terminating
UEUE
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Access failure due to terminating UE
Access failure location (UE Ec/I0 ):
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Access failure due to terminating UE
The coverage is not bad where the UE originates the VP access:
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Access failure due to terminating UE
CN send “disconnect” message with the cause “bearer capability not authorized” before access failure:
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Access failure due to terminating UE
setup signaling procedure for RRC and RAB have already finished. The cause of disconnect is the same:
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Access 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:
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Summary
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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