09 WCDMA RNO Access Failure Problem Analysis 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 “Cal[.]
Trang 1WCDMA Access Problems Analysis
Trang 2Access 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
Trang 4Course Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems Case study
Trang 5Definition of access failure
General originating call setup signaling flow:
Trang 6Definition of access failure
General terminating call setup signaling flow:
Trang 7Definition 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
Trang 8Course Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems Case study
Trang 9Access problem analysis process
Preparation before Analysis
Access problem analysis
methods
Trang 10Preparation 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
Trang 11Access problem analysis process
Preparation before Analysis
Access problem analysis methods
Trang 12Access problem analysis methods
General methods of access problem analysis:
Traffic statistics data analysis Custom complaint collection
Call setup test in specific area
Coverage analysis
Signaling analysis
Trang 13Access 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.
Trang 14Course Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems
Case study
Trang 15Common reasons for access problems
RF reasons
Radio Parameter Settings
Other reasons
Trang 16RF reasons
Poor coverage
Strong Uplink or downlink Interference
Trang 17Common reasons for access problems
RF reasons
Radio Parameter Settings
Other reasons
Trang 18Radio parameter settings
Improper threshold of Qqualmin and Qrxlevmin
Improper settings of access threshold
Inappropriate settings of preamble power ramp step and retransmission timesInappropriate 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
Trang 19Common reasons for access problems
RF reasons
Radio Parameter Settings
Other reasons
Trang 20Other reasons
Data configuration problems
Access problems caused by cell load
Trang 21Course Contents
Definition of access failure
Access problem analysis process
Common reasons for access problems
Case study
Trang 22Case 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 UE
Trang 23Access failure due to synchronization failure
Access failure location:
Trang 24Access 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:
Trang 25Access failure due to synchronization failure
UE does not send RRC Connection Setup Complete to RNC after receiving RRC Connection Setup message from RNC :
Trang 26Case 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 UE
Trang 27Access failure during RB setup
Access failure location:
Trang 28Access 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 :
Trang 29Access failure during RB setup
The cause of call setup failure is Requested circuit/channel not available:
Trang 30Access 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:
Trang 31Case 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 UE
Trang 32Access failure during handover process
Access failure location (Scanner Rscp ):
Trang 33Access failure during handover process
ScannerEc/I0 :
Trang 34Access failure during handover process
Scanner BestServer :
Trang 35Access failure during handover process
During access process, UE Txpower is rising rapidly :
Trang 36Access failure during handover process
And the downlink Bler reaches 100%:
Trang 37Access failure during handover process
UE report the measurement of cell Sc508 which request the active set update:
Trang 38Access 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:
Trang 39Access 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:
Trang 40Access failure during handover process
Trang 41While the radio links hold on till successful handover is completed:
Trang 42Access 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:
Trang 43Case 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 UE
Trang 44Access failure due to terminating UE
Access failure location (UE Ec/I0 ):
Trang 45Access failure due to terminating UE
The coverage is not bad where the UE originates the VP access:
Trang 46Access failure due to terminating UE
CN send “disconnect” message with the cause “bearer capability not authorized”before access failure:
Trang 47Access failure due to terminating UE
setup signaling procedure for RRC and RAB have already finished The cause of disconnect is the same:
Trang 48Access 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:
Trang 49Access 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 .