UMTS Call Drop Analysis file

7/23/2019 UMTS Call Drop Analysis file

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UMTS Call Drop Analysis

Content

Definition of Call DropReasons of Call Drop

Analysis of Call DropParameters of Call DropCase of Call Drop

Definition of Call Drop

Type of Call Drop Definition Call termination not through the normal hang up process, that is dropped calls.

Tow types of call drop definition:

o Definition of drive test indicators

o Definition of network management indicators

Definition of Drive Test ndicators The definition of drive test:

o Call drop rate! "um#er of call drop times$"um#er of call setup success times

o "um#er of call setup success times%&:After the Alerting message is received

"um#er of call drop times%&:'Air interface signaling at the () side*

o The Connect AC+ message is not received #ut the ystem nformation message is

received.

o After the Connect AC+ message is received, RRC Release message received and

the reasons is "ot "ormal.

o After the Connect AC+ message is received, any of the CC Disconnect, CC Release,

CC Release Complete message received and the reasons is "ot "ormal.
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() -oluntarily nitiated ignaling Release

Definitions of "etwork anagement ndicators


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Definitions of "etwork anagement ndicators


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Reasons of Call Drop

Call Drop Reasons Poor Coverage

(n/configured "eigh#or Cell 0andover

nterference

PC Confliction

)ngineering )rror

Poor Coverage

The decision whether it is pro#lem of uplink or downlink poor coverage is #ased on the

power of dedicated channel #efore call drop. (1 Poor Coverage:

o T2 power reaches the ma3imum

o (1 41)R is poor

o "ode4 report 5R1 failure6

D1 Poor Coverage:

o T2 power reaches the ma3imum

o D1 41)R is poor

canner:

o f the RCP and )c$o of the cell with the #est coverage are poor, you can infer that

the coverage is poor.

(nconfigured "eigh#oring Cell issed neigh#or cell.

Removal of key neigh#or cells caused #y com#ination of macro diversity.

(ntimely update of the e3ternal cell information.

0andover


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The handover process is incomplete

o Radio )nvironment #ecoming #ad, () can not receive the 5Active et (pdate6

Ping/pong 0andover

o n a short time, () send different Report for delete or add cell A

nterference Reasons for Pilot Pollution:

o Cross/cell coverage of high "ode/4

o "ode/4 in ring layout

o ignal distortion caused #y street effect or strong reflection

7udgment of D1 interference:

o CPC0 RCP of the active set is large than /89d4m

o )c$o is lower than /&d4

Reason of D1 interference:


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o Pilot pollution

o (nconfigured neigh#oring cell

7udgment of (1 interference:

o The average RT;P of an idle cell e3ceeds /&


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PC Confliction

;hen analy>ing such call drop, check Cell D in the call drop signaling #esides PCs #ecause theneigh#or relation is identified #y Cell D.

Cell A and Cell 4 are configured as neigh#or cell for each other.

Cell C and Cell 4 are not configured as neigh#or cells for each other.

Cell A and Cell C have the same PC.


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)ngineering )rror Call drops caused #y engineering error:

o Reversely/connected antenna

o An e3cessive -;R

o ulti/#and antenna pro#lem

o 1eakage of signals from indoor distri#ution system


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o Call drop caused #y unsteady transmission

Analysis of Call Drop

Common Analysis ethods for Call Drop Analy>ing Call Drops #y DT

Analy>ing Call Drops #y Traffic tatistics

Analy>ing Call Drops #y DT

Call drop data

Call drop spots

ta#ility of the primary serving cell

RCP and )c$o of the primary serving cell

Reproducing of pro#lems with DT


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Analy>ing Call Drops #y Traffic tatistics The commonly used +P analysis method is the T?P cell method, which means the top cells

will #e screened out according to certain inde3, then these top cells are optimi>ed and then the topcells are selected again. After several repetitions, the related +P can #e speedily converged.


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ulti/Dimension Analysis ulti/dimension analysis is carried out from different perspectives.

@or the call drop pro#lem, not only the call drop itself, #ut also related factors such as

o access

o handover

o traffic statistics

o time

o RT;P


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Accident Analysis Check the euipment alarm and system log of this period to find out hardware pro#lemsB Check the transmission of this periodB

Check whether the upgrade or cell #locking is performed during this periodB

Check whether there is an occasion with a#rupt high traffic reuirements such as a concert,

game, or e3hi#ition.


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Ranking Analysis Ranking analysis

o Ranking analysis is carried out through classifying data into top " and #ottom " data

from a large amount of data.


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Cause/and/)ffect Analysis @or a certain effect, the cause/and/effect analysis is performed to locate the causes that may

result in the effect and to determine the influence of the causes.

@or e3ample, the call congestion of a cell may #e caused #y insufficient capacity of the

hardware, of the downlink, or of the uplink.

Parameters of Call Drop

?ptimi>ation ethods for Call Drop )ngineer optimi>ation:

o Directional angle, downtilt, position of Antenna, type of Antenna, Transmit power of

4, position of 4, new 4.

Radio parameter optimi>ation:

o Time to Trigger, C?, threshold of ena#ling$disa#ling Compression ode, a3imum

transmit power of D1 R1, Threshold of nter/freuency and nter/system.

Time To Trigger

Cell ndividual ?ffset


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Threshold of )na#ling$Disa#ling Compression ode

a3imum Downlink Transmit Power of Radio 1ink


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a3imum Downlink Transmit Power of Radio 1ink


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Threshold of nter/system handover

Timer and Counter Related to Call Drop


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Case of Call Drop

"eigh#oring Relation Adustment Reason

o 0igh call drop rate caused #y improper neigh#or list configuration

Description

o The call drop rate of the TR&9;/& cell corresponding to R"C& in 1i#ya is always

around , and no hardware alarm is generated. The cell coverage is mainly on the sea.


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"eigh#oring Relation AdustmentAfter the neigh#or relation is adusted, the C call drop rate of TR&9;/& decreases from to&..

(nconfigured "eigh#oring Cell


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(nconfigured "eigh#oring Cell ain parameters:

o Cells in the system

Trou#leshooting process:

o The cell with C = is in the detection set and cannot #e added to the active set when

the uality of the serving cell with C EF is e3tremely poor. This is a typical unconfigured neigh#oringcell.

olution:

o Adust the neigh#or relation: Add the cell with C = to the neigh#or list of the cell with

C EF.

Result:

o n the same test, the cell with C = is in the active set of the serving cell with C EF.

;hen the signal cell with C = is strong enough, the () hands over from the serving cell to the cellwith C =.


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oft 0andover Parameter ?ptimi>ation Reason:

o 1ow handover success rate #ecause of improper soft handover parameter

configuration

Description:

o The success rate of the handover from sector & 'C FG* of the huian 1u site to

sector H 'C FF* of the eihuacun hotel is low. This area is within the huian 1u section.

ain parameters:

o oft handover &a$ event handover threshold, trigger time

oft 0andover Parameter ?ptimi>ation

The signal uality of the huian 1u section is poor and unsta#le #ecause there are overpasses in

this section, 4ecause the comparative threshold decision algorithm is used, a cell with poor signaluality may #e added to the active set if the &a threshold is e3cessively high. f the R"C sends the

Activeet (pdate Command message to instruct the () to enter this cell, the soft handover may fail#ecause the radio link cannot #e set up due to poor and unsta#le signal uality of this cell.


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Adust the &a$ event handover threshold and trigger time of cell FG.

1ower the &a event handover threshold and shorten the trigger time to ensure that the cells

with good signal uality can firstly enter the active set.

Raise the event handover threshold and e3tend the trigger time so that the cells are not

deleted too early due to drastic signal deterioration.

Result

o After the parameter optimi>ation, cell FF of the 4/& 'eihuacun hotel site* can #e

added to the active set uickly and is not deleted too early.

o According to the drive test result from more than &ation in HI$I 0andover Reason

o Call drop #ecause of incorrect data configuration

Descriptiono ;hen the HI$I handover tests are performed at the #oundary of the I network,

the handover from the I network to the HI network succeeds in the west to east direction, #ut thehandover fails in the east to west direction.

ain parameters

o 4C D, 1AC, "CC, and 4CC0 of the HI neigh#oring cell


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Trou#leshooting process

o 4ecause the handover from I network to HI network fails, you should firstly check

whether HI neigh#oring cells are configured. f all HI neigh#oring cells are configured, go to thene3t step.

o Record whether the HI agem () starts the compression mode when the signal

uality of a I () is lower than the threshold for starting the compression mode, and record the Cof the HI cell where the compression mode is started.

o Jou can find that the () starts the compression mode after the preceding step is

performed. The signaling is as follows:

olution:

o Check the 4C and 1AC of the target HI cell on the C". Jou can find that the 1AC is

not configured. Then, reconfigure the 1ACs of all HI neigh#oring cells on the C".

Result:


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o After the data is configured again, all I/to/HI handovers succeed.

uggestion for similar pro#lems:

o n the I/to/HI handover, the 4C D, 1AC, "CC, and 4CC0 of HI neigh#oring

cells must #e configured in the HI neigh#oring cell data#ase of the ?CR and on the C".

Call Drop Case/0andover


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UMTS Call Drop Analysis file