Call Performance Issues.docx

8/12/2019 Call Performance Issues.docx

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Call Performance Issues

at3g,performance,tutorial

Got some reading which i though useful for u who work on network performance or fault management, kinda

action that can taken in solving common issue in 3G network.

Behaviour Problem Description Possible solutionsCall set-up

failure

Call drop

Poor coverage

areaIf problem is poor

coverage, this means

poor RSCP (


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Behaviour Problem Description Possible solutionsCall set-up

Failure

Call drop

High PrxTotal

due to UL

Externalinterference

The PrxTotal level is

significantly higher than

expected in no/low loadconditions.

Try to figure the possible

area/direction of the

interference by checkingPrxTotal level on

neighbouring cells.

Alternatively use spectrum

analyser & directive antennato locate interferer.

Inform operator/regulator

about the found conditions.

Check if auto tuning range

is large enough (20 dB).Call set-up

failure

Call drop

High PrxToatal

due to wrong

MHA settings



expected in no/low loadconditions.

MHA settings should be

checked, see more in

reference [7]

In case of MHA is used in

BTS check MHA and cables

loss parameters, otherwisePrxTotal value will be toohigh.

(If MHA parameter is set to

ON, Cable loss parameter is

used, Cable loss = Real

MHA gain = Feeder loss

parameter)Call set-up

failure

Call drop

High Prxtotal

due to

Installation

problems



expected in no/low load

conditions.

Check the antenna

installation as the last

alternative in high PrxNoise

case.

Cell set-up

failureBad RRC

connection set-

up success rate

due to slow Ue

cell reselection

RRC connection set-up

complete message not heard

by BTS.

Set parameters so that

reselection process will start

earlier:

Qqualmin, Sintrasearch and

Qhyst2 as per latestrecommendation [8]

Long call set-up

timeLong time

interval for sync

between RNC

and BTS before

connection

The value of Parameter

N312 is too high: maximum

number of in sync

indications received from

L1 during the establishment

of a physical channel

Use smaller value N312 (2,

recommendation is 4).

Use Actix for checking the

call set-up delay (L3

messages).

Use call set-up time

optimisation feature

Dynamic setting ofActivationTimeOffset

(possible in RAN1.5.2 ED2)

enables 200 to 500ms

reduction for set up delay.


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Behaviour Problem Description Possible solutionsDropped call SHO to wrong

cell will cause

drop call.

Overshooting cell come

temporarily into active set

and forces a suitable servingcell to be dropped out. Later

RSCP suddenly drops in the

wrong cell and causes adropped call because there

is no neighbour defined.

Pan away overshooting cell

if it is too close to the

serving cell, otherwise applydown tilting as well.

Dropped call Cell sufferingfrom UL

interference =

DL (CPICH)

coverage much

bigger than UL

coverage

As the UE Tx power is not

enough for target cell

synchronisation, the SHO

fails which will cause call

drop later.

Use cell individual offset

(negative value) parameter

to balance the DL and UL

coverage.

Check traffic direction of in-

car UEs to decide which cellrequires offsets.

Dropped call DL CPICHcoverage

Cell with lower CPICH

power than the surrounding

is having too good UL

performance, as this cells

UL cannot be used

efficiently due to SHO isdecided upon DL (CPICH

Ec/No).


(positive value) parameter

to balance the DL and UL

coverage.

Note: Cell individual offsets

are not taken into account

when calculating the added

cell Tx power.Dropped call Round the corner

effectThe call drops due to too

rapid CPICH coverage

degradation for Cell A, andtherefore there is not enough

time for SHO.


(positive value) parameter

to balance the DL and ULcoverage.

Note: Cell individual offsetsare not taken into account

when calculating the addedcell Tx power.

Dropped

call/SHO failureToo many

neighboursIn SHO area the number of

combined neighbouring

cells become more than 31.

HO list is created using

RNC algorithm in the final

stage some of the

neighbours will randomly

be removed.

Delete unnecessary

neighbours.

Improve dominance.

Documents

Call Performance Issues.docx