UMTS

Fundamental

Mehmet TANIS
Umts Optimisation Expert
+90 541 953 21 21
Study 1 - Content
The Load Measurement

The Load Control Measures

Admission Control
Load Balance
Congestion Control
Load Measurement

Load Concept
Load Measurement
Uplink Load
Downlink Load
Load Concept

Load:
The occupancy of capacity
TDMA and FDMA system: the capacity is hard limited.
Example: In GSM, the cell capacity (channel number) is
fixed.
CDMA system:
soft capacity
Hard capacity
Load Concept

User#1 User#1
Frequency User#2 Frequency
User#3 User#2
User#3

Time Time
TDMA FDMA

Frequency

User#1
User#2
User#3
Time

CDMA
Code
Capacity of CDMA system

Soft capacity:
Interference (UL)
Power (DL)
Hard capacity
Code
Hard ware resource
Transport resource, NodeB processing capability.
The Load controls

CAC: Call Admission Control

Used to admit/reject the resource request to keep the
system work in stable state.
Load Balance:
To balance load between cells to maximize the system
capacity
Congestion Control:
To get the system come back from congestion state to the
stable state.
The Content

The Load Measurements

The Load Control Measures
Admission Control
Load Balance
Congestion Control
Load control - CAC

Admission Control
 Call Admission Control (CAC)

What is CAC?

Why we need CAC?

Basic concepts used in the algorithm.

How the CAC been implemented.

Confidential Information of Huawei.

No Spreading without Permission.
What is CAC?
Flow chart of CAC
call arrive

Get the service characteristic and the current load

Suppose the user is accepted, and calculate the predicted

UL load factor. And then compared with the threshold.

admitted? n

Suppose the user is accepted, and

calculate the predicted DL load factor.
And then compared with the threshold.

admitted? n

call admitted call rejected

end
Principle of the CAC
Why we need CAC?
 Why we need CAC?

WCDMA is an interference limited system, after a new call is

admitted, the system load will be increased.

If a cell is high loaded, a new call will cause ongoing user

dropped.

We must keep the coverage planed by the Radio Network

Planning.
 Admission control scenarios

CAC is needed under such scenarios

New call

Handover

New RAB(s) for ongoing call

Bandwidth increasing reconfiguration

Basic concepts used in the
algorithm.
 System load
Uplink : RTWP (Received Total Wide band Power)

The RTWP has an unique corresponding with the uplink

load
Backgroud noise
UL 1
RTWP

Downlink : TCP (Transmitted Carrier Power)

The TCP has no unique corresponding with the actual

downlink load factor. And because the actual downlink
load factor is difficult to measure, we use the TCP instead.
 Activity factor

Activity factor : The percentage of time that the data

transmission is active.

The UL and DL activity factor may be different for dedicated

channel.

Different service type has different activity factor.

How the CAC been implemented.
 Strategies
Only for dedicated channels, and reserve a certain resource for
the common channels.

UL and DL CAC algorithms are independently.

In principle, a request will be admitted only when UL and DL are

both admitted. But if UL or DL CAC switch is closed, only one
direction CAC also can be realized.
 Strategies

UL CAC is not need for intra-frequency handover because the

interference is already included in the target cell.

Handover threshold, conversational threshold and other

services threshold are used to keep the priority of the handover
higher than the conversational, conversational than the Best
Effort services.
UL Algorithm1

Admission request

PN
Get current RTWP, and calculate the
current load factor.
UL 1
RTWP
1
Get the traffic characteristic, and
estimate the increment of load factor. W
1
Eb
R
Calculate the predicted load factor.
N0
UL _ predicted UL 0
Smaller than the
threshold?
n
y

admitted rejected

end of UL CAC
DL Algorithm1

Admission request

Get current TCP. P(N )

Get the traffic characteristic, and

estimate the increment of tcp. P

Calculate the predicted tcp. P( N ) P Pcomm

Smaller than the

threshold?
n
y

admitted rejected

end of DL CAC
The Content

The Load Measurements

The Load Control Measures
Admission Control
Load Balance
Congestion Control
 Load Balancing (LDB)

What is LDB?

Why we need LDB?

Basic concepts used in the algorithm.

How the LDB been implemented.

What is LDB?
Intra-frequency LDB ( Cell Breathing )
Load decrease, and cell
expand.

Original

Load increase, and cell

shrink.
Inter-frequency LDB

For cells have different frequencies, and the same

coverage.

Load level
indication

f1 f2
f1
& f2

Result
Why we need LDB?
 Why we need LDB?

Intra-frequency LDB

To move calls in a heavily loaded cell to neighboring

cells.
To relieve calls in surrounding cells when lightly loaded.

Inter-frequency LDB
To distribute calls in a heavily loaded cell to the lightest
loaded carrier co-located.
The Content

The Load Measurements

The Load Control Measures
Admission Control
Load Balance
Congestion Control
 Why We Need Congestion Control ?

To receive information correctly, signal in receiver must

be above certain S/I (Signal/Interference ) threshold.

In CDMA system, all users in a cell use the same

frequency, so one customers signal will be an
interference to others.
 Why We Need Congestion Control ?

To overcome the interference, transmitter must

increase signal power, that is, it need more MS or BTS
power.
MS or BTS power is limited. If interference keeps rising,
S/I requirement can not be achieved at a certain
degree, quality of services will deteriorate and some
users will drop.
Congestion occurs.
Why We Need Congestion Control ?

To guarantee the networks stability and customers

QoS (Quality of Service), we should try our best to
avoid congestion.

I.e., some actions should be taken to keep the

whole system away from congestion or quickly
recover from congestion!
 Congestion Control General

Abbr. LCC (Load Congestion Control)

Object: All BE (Best Effort) services.

Range: Downlink only. (Optimization is ongoing.)

Study 2 - Content
Accessbility KPI

Congestion Type & solution Types

Accessbility & Transmission Quality Comparison

 General 3G KPI`s

Cssr

PS Rab Establishment Success Rate

PS Rab Abnormal Release Rate

Cs Rab Abnormal Release Rate

Rtwp

PDU Retransmission Rate

IP Path Lost

IP Path Delay
 RRC Problem Causes..

RRC.FailConnEstab.NoReply counter is generally arises from the following

resources..

Poor / weak Coverage (DL / UL)

Pilot Pollution / No Dominant Serving Cells..
Missing Neighbor
SC Clash
Handover With Long Delay
No resource availability (RRC Rej Cong)..
High Rtwp Problem
External Interference
 RAB Establishment Problem Causes..

The RAB failures caused by unsupported configuration and congestion are

similar with those of RRC procedure , following counters count the failure..

Reason
RAB.FailEstabCS.RNL
RAB.FailEstabCS.Cong
RAB.FailEstabCS.DLPower.Cong
RAB.FailEstabCS.UuFail
RAB.FailEstabCS.ULPower.Cong
RAB.FailEstabCS.UuNoReply
RAB.FailEstabCS.IubFail
RAB.FailEstabCS.RBIncCfg
RAB.FailEstabCS.Code.Cong
RAB.FailEstabCS.ULCE.Cong
RAB.FailEstabCS.TNL
RAB.FailEstabCS.DLIUBBand.Cong
RAB.FailEstabCS.ULIUBBand.Cong
RAB.FailEstabCS.DLCE.Cong
RAB.FailEstabCS.RBCfgUnsup
RAB.FailEstabCS.PhyChFail
 AMR Call Drop Problem Causes..

AMR Call drop actualy arises due to following problems..

High Uplink Interference

External Inteference
High Uplink / Downlink Congestion
Not available code / CE resources
Missing neighbouring
Pilot Pollution
No Dominance Cell
Overshooting..
SC clash..
Long Handover delay time..
PS Call Drop Problem Causes..

PS Call drop actualy arises due to following problems..

High Uplink Interference
IP Path Lost
IP Path Delay
High Pdu Retransmission Rate
External Inteference
High Uplink / Downlink Congestion
Not available code / CE resources
Missing neighbouring
Pilot Pollution
No Dominance Cell
Overshooting..
SC clash..
Long Handover delay time..
KPI problems are generally due to soft or harhd capacity problems on 3g..

So firstly we should to check and solve all type congestion on the network..
What Is The
Congestion ???

In data networking and queueing theory, network congestion occurs

when a link or node is carrying so much data that its quality of
service deteriorates. Typical effects include queueing delay, packet
loss or the blocking of new connections. A consequence of the latter
two effects is that an incremental increase in offered load leads
either only to a small increase in network throughput, or to an
actual reduction in network throughput.
Congestion Types

IUB Band Congestion

HSUPA User Congestion

HSDPA User Congestion

Downlink Power Congestion

Uplink Power Congestion

Uplink Channel Element Congestion

Code Congestion
IUB Band Congestion

IUB Band congestion problems are caused by problems such as transmission capacity and the
fiber length .. Under the circumstances such as radio transmission capacity and fiber length
should be checked .. it needs to increase its transmission capacity if necessary to get any
actions..

IUB congestion will cause low CSSR of both CS and PS service. We can use NodeB counters to
calculate IUB utility ratio.

If average utility ratio is more than 70%, IUB expansion is recommended for this site.

UL IUB congestion:
VS.RRC.Rej.ULIUBBandCong+VS.RAB.FailEstab.CS.ULIUB Band.Cong+ VS.RAB.FailEstab.PS.ULIUBBand.Cong+
VS.RAC.SHO.Fail.ULIub.Cong+ VS.RAC.HHO.Fail.ULIub.Cong

DL IUB congestion:
VS.RRC.Rej.DLIUBBandCong+VS.RAB.FailEstab.CS.DLIUB Band.Cong+ VS.RAB.FailEstab.PS.DLIUBBand.Cong+
VS.RAC.SHO.Fail.DLIub.Cong+ VS.RAC.HHO.Fail.DLIub.Cong
 HSUPA User Congestion

HSUPA user congestion problems causes by the high user number and high
user traffic .. In this case, the following checks should be made for solves
its..

Overshooting check

If cell or cells are overshooting we should to implement tilt actions , if tilt

is on maximum rate , we should to decrease pcpich Power by below
command line on the rnc..

MOD UCELL:CELLID=XXXXXXX,PCPICHPOWER=300;

If There is No RCU / RET Configuration firstly we should to configure

RCU/RET and than we can go to change tilt implementation..
 HSUPA User Congestion

Load Sharing

We can solve Hsupa user congestion with traffic load sharing between neighbor
cells.. Traffic will go by congested cell to non-congested cells with below
parameter or actions....

* Inter or Intra freq handover threshold changes..

* Tilt implementation between congested and non-congested

cells..

* Pcpich Power implementation between congested and non-

congested cells..

* Number of maximum hsupa user cong checks and changes..

UL DL total equivalent user number changes..

 HSUPA User Congestion

Maximum HSUPA User Num Check

We can solve Hsupa user congestion with changes max hsupa user num..
Default range of that parameter for each cells 20.. We can increase that
parameter from 20 to 40/60 but it`s not recommended due to caused Uplink
Power Congestion.. We must to check that parameter maybe it isnt on default
range..

Checking command line ; ( For changes we use MOD )

LST UCELLCAC:CELLID=4242,MAXHSUPAUSERNUM=40,ULNONCTRLTHDFOROTHER=75;
HSUPA User Congestion Trend After below action..

- Max HSUPA User Num Increased

- E-AGCH Channel Num increase ( for each 20 HSUPA User 1 )
- E-RGCH Channel Num Increase ( for each 20 HSUPA User 1 but recommend value maximum 2 )
 Downlik Power Congestion

Downlink Power Congestion Caused ;

Low Downlink Power Range - Check the Max Tx power of the congested cell

Low Power Capacity RRU We must to change RRU types from 60 watt to 80 or 120 watts

Overshooting Tilt or Pcpcih Power Implementation or Traffic Sharing..

Low Max Transmitter Power range We must to check RRU model , capability and maximum
transmit power range.. And adjust to maximum range..
Downlik Power Congestion

Check the MeanTCP and MeanRTWP:

1.Check the Max Tx power of the congested cell

Add cellsetup:cellid=1111, maxtxpower=430

2.Check counter VS.MeanTCP and VS.MeanTCP.NonHS

and calculate the utility ratio tocheck whether the utility ratio is
very high.

3.Monitor the RTWP to check whether RTWP is very high.By

this check then we can know the uplink and downlink power
status.
 Downlik Power Congestion

Max Transmit Power Changes Command Line..

MOD ULOCELL: ULOCELLID=10196, LOCELLTYPE=NORMAL_CELL, MAXPWR=460; ( This command for Nodeb )

MOD UCELL: CELLID=10196, MAXTXPOWER=460; ( this command for Rnc )

RRU Types , Mimo and Maximum Transmit Power for Each Cells..
 Downlik Power Congestion

Solution for DL Power congestion :

1. Implement DL LDR

Enable DL LDR switch:

MOD UCELLALGOSWITCH: CellId=X, NBMLdcAlgoSwitch= DL_UU_LDR-1;

Modify UCELLLDR parameters:

Ldr First action : If there is high traffic should select BE Traff Rate , if there is high code usage should to
select CodeAdj..

MOD UCELLLDR: CellId=X, DlLdrFirstAction=CodeAdj, DlLdrSecondAction=BERateRed,

DlLdrThirdAction=InterFreqLDHO, DlLdrFourthAction=CSInterRatShouldBeLDHO,
DlLdrBERateReductionRabNum=3, GoldUserLoadControlSwitch=ON; (if customer agrees
for handover of CS service to 2G in case of congestion in 3G otherwise remove fourth
action; if we have single carrier InterFreqLDHO action should be removed from proposal)

2. Modify UCELLLDM Parameters:

MOD UCELLLDM: CellId=X, DlLdrTrigThd=60, DlLdrRelThd=50;

3. Modify UCELLCAC Parameters:

MOD UCELLCAC:CELLID=X,DLCONVAMRTHD=85,DLCONVNONAMRTHD=
85,DLOTHERTHD=83,DLHOTHD=87,DLCELLTOTALTHD=93;
 Downlik Power Congestion

If TCP ratio is very high, it means downlink power congestion. Then we can:

For single carrier cells,

we can use downlink LDR:

MOD CELLALGOSWITCH:CellId=0, NBMLdcAlgoSwitch=DL_UU_LDR-1;

MOD CELLLDR:CellId=0, DlLdrFirstAction=BERateRed, DlLdrBERateReductionRabNum=1;GoldUserLoadControlSwitch=ON;

For F1 cell,

Setting LDR as follows:

MOD CELLALGOSWITCH:CellId=0, NBMLdcAlgoSwitch=DL_UU_LDR-1;

MOD
CELLLDR:CellId=0, DlLdrFirstAction=BERateRed, DlLdrSecondAction=InterFreqLDHO,DlLdrBERateReductionRabNum=1, GoldUserLoadControlSwitch=ON;
 Downlik Power Congestion

For downlink power congestion, if LDR cant solve the problem, we

can reconfigure the related Call Admission congestion threshold:

1.Start DL LDR algorithm earlier MOD CELLLDM: DlLdrTrigThd=55, DlLdrRelThd=45;

2.Raise the power congestion threshold MOD CELLCAC: CellId=0, DlConvAMRThd=85, DlConvNonAMRThd=85,
DlOtherThd=83,DlHOThd=87, DlCellTotalThd=93;

Current DL LDR setting as below on Rightel Network..

DL LDR trigger threshold = 70

DL LDR release threshold = 60

DL threshold of Conv AMR service = 80

DL threshold of Conv non_AMR service = 80
DL threshold of other services = 75
DL handover access threshold = 85
DL total power threshold = 90
Downlik Power Congestion Trend after DL Call
Admission Threshold increase..
Uplink Power Congestion

Uplink Power cong is can solve by the below issues / actions..

UL total equivalent user number changes..

Uplink User noice decrease from 24 to 18.. This parameter will press to UE uplink power
usage is from 24 db to 18 db.. It will give us more power capacity for other UE`s..

Maximum hsupa user num check and if it has been set too many high range , we should to set
it lover than before..

Overshooting check and tilt or power implementation..

 Uplink Power Congestion

Currently for uplink we use Equivalent Number of User to do CAC; for downlink we use
TCP todo CAC. According to our CAC strategy, first make sure some basic parameters
should beconfigured as follows:

ADD CELLALGOSWITCH:CellId=0 , NBM Ul CacAlgoSelSwitch=ALGORITHM_SECOND , NBM Dl CacAlgoSelSwitch=ALGORITHM_FIRST ;

ADD CELLCAC:CellId=0 ,Ul TotalEqUserNum=150;

Current UL LDR setting as below on Rightel Network..

UL LDR trigger threshold = 55

UL LDR release threshold = 45

UL threshold of Conv AMR service = 75

UL threshold of Conv non_AMR service = 75
UL threshold of other services = 60
UL handover access threshold = 80
UL total power threshold = 83
 Uplink Power Congestion

Solution for UL Power congestion :

1. Implement UL LDR

Enable Switch for UL LDR-

MOD UCELLALGOSWITCH: CellId=X, NBMLdcAlgoSwitch= UL_UU_LDR-1;

Modify LDR parameters-

MOD UCELLLDR:CELLID=X,ULLDRFIRSTACTION=BERateRed,ULLDR
SECONDACTION=InterFreqLDHO,ULLDRBERATEREDUCTIONRAB NUM=3; (This is without IRAT for
example if customer dont want IRAT even if congestion in 3G; if we have single carrier
InterFreqLDHO action should be removed from proposal).

2. Modify UCELLLDM Parameters:

MOD UCELLLDM:CELLID=X,ULLDRTRIGTHD=55,ULLDRRELTHD=45;

3. Modify UCELLCAC Parameter :

MOD UCELLCAC:CELLID=X,ULTOTALEQUSERNUM=160;

Can also try to change few more UCELLCAC parameters:

MOD UCELLCAC: CellId=X, UlNonCtrlThdForAMR=85, UlNonCtrlThdForNonAMR=85,

UlNonCtrlThdForOther=83, UlNonCtrlThdForHo=87, UlCellTotalThd=93,
 Uplink Power Congestion

If the configuration is correct and power congestion still happen, we recommend solutions asfollows:

Uplink power congestion:

If RTWP is always very high (more than -90dBm), most probability it was caused byuplink interference. Then first check
whether interference problem, if uplink interference problem, then solving interference is the recommended method.

If not interference problem. We can:1.For single carrier cells or F1 cells, use LDR algorithm:

Switch on the LDR switch:

MOD CELLALGOSWITCH:CellId=0, NBMLdcAlgoSwitch=UL_UU_LDR-1;

Setting LDR action:

MOD CELLLDR:CellId=0, UlLdrFirstAction=BERateRed, UlLdrBERateReductionRabNum=1;GoldUserLoadControlSwitch=ON;

Uplink Power Congestion Trend after UL Call
Admission Threshold Increase..
Uplink Channel Element Congestion

What is CE(Channel Element)?

A band Channel Element is the resource base required in the Node-B

to Provide for one voice channel capacity, including the control plane to
Provide for one voice channel capacity, including the control plane
signaling, compressed mode, the transmit diversity and softer
handover. signaling, compressed mode, the transmit diversity and
softer handover.
Uplink Channel Element Congestion

Solutions for Uplink CE Congestion:

Upgrade the CE license according to your vendor.

Wbbp Addition..

Channel Element License Setting checks..

R99 services uses more CE so try to reduce R99 services.There are several
parametrs which can help R99 Service utlization optimization.

Load Balacing between carriers can help to reduce Uplink CE Congestion.

Uplink Channel Element Congestion

How Can Define Wbbp..

Wbbp Types , License Number , Support Cell Number..

How Can Define Wbbp UL-DL License..

How Can Define Uplink or Downlink group specification..

Wbbp addition , definition and license update documentation

is sharing as below objects for the RAN16 version
 Uplink Channel Element Congestion

Wbbp Types and Support Uplink Downlink Channel Element License

Number & Supports Cell`s Number

Wbbp Type Uplink Channel Element Number Downlink Channel Element Number Support Cell Number
WbbpB2 128 128 3 Cell
WbbpB3 256 256 6 Cell
WbbpD2 384 384 6 Cell
WbbpF3 384 512 6 Cell
WbbpF4 512 768 6 Cell
UbbpD3 384 512 6 Cell
Uplink Channel Element Congestion

R99 Service CE Consumption

Directi Rate SF Number of CEs Corresponding

on (kbit/s) Consumed Credits
Consumed
UL 3.4 256 1 2
13.6 64 1 2
8 64 1 2
16 64 1 2
32 32 1.5 3
64 16 3 6
128 8 5 10
144 8 5 10
256 4 10 20
384 4 10 20
DL 3.4 256 1 1
13.6 128 1 1
8 128 1 1
16 128 1 1
32 64 1 1
64 32 2 2
128 16 4 4
144 16 4 4
256 8 8 8
384 8 8 8
Uplink Channel Element Congestion
LICENSE UPDATE : From the main menu we select NE License Management and than we will go to
right page.. On right page we will find to NodeB and than right click..
 Code Congestion
Summary

Code Congestion Will cause low Cssr of Both Cs and Ps Services..

Solution
Code Congestion Will happen in single carrier cell or F1 cell.. If single carrier cell exprience
very serious code congestion ' expanding 2 carriers or 3 carriers is recommended..
To solve code congestion ' we recommend using LDR algorithm also..

The MML configuration is as follows..

Switch on the LDR switch:

MOD CELLALGOSWITCH:CellID=111,NBMLdcalgoswitch=CELL_CODE_LDR-1;

Setting LDR Action:

MOD
CELLLDR:CellId=111,DLLDRFIRSTACTION=CodeAdj,DLLDRSECONDACTION=BERATERED,DLLDRBERTEREDUCTIONRABNUM=1,GoldUSerLoadControlSwi
tch=ON;
CS Drop & Call Setup Trend of some city of TH1RNCH2.. There is PS Rab Setup
Success rate and Hspa Rab Setup Success Rate`s are improved from %90 to %99..
 Rtwp

RTWP : Received Total Wideband Power.

Rtwp

Total diffrerence should to be maximum 6 db between Rx-main and Rx-

Diversity... IF ve checked more than 6 db there are Rtwp problem.. We must to
check what is the caued..
Rtwp

How can solve Rtwp ?

If Rtwp problem caused by the external interference resource`s we can check it wih
spectrum analyzer..

We should to check Hardware equipment of site`s or problematic cell`s

Antenna changes , wbbp changes , RRU changes issues can solve Rtwp if rtwp caused
by internal problem`s..

Antenna position check`s maybe there are any equipment or external things are closed
antenna position and directions..

Site definitions are remove and add again by the bss side..

Try to enable IC , TurboIC , TurboICPhase2 ( Ran16 ) feature for which sites has
WbbpF4 , WbbpD3 type Wbbp card..
Rtwp

Antenna direction and site position check`s..

 Transmission Quality
We should to check below KPI Rate if PS Accessbility , Hsdpa Accessbility ,
Hsupa Accessbility is low..

PDU Retransmission Rate

IP Path Lost Rate
IP Path Delay Time ( millisecond )

Above KPI directly affecting all kind of accessibility..

 Transmission Quality

Below trend shows IP Path Lost Rate of some sites..

IP Path Loss rate is directly affecting acessbility and Hsdpa &Hsupa

Throughput rate.. Before starting optimization firstly should to clear IP
Path Lost , IP Path Delay , PDU Retransmission Rate..
 Transmission Quality

High PDU Retransmission Rate directly affecting to the Hsdpa

Throughput Rate..
Study 3 - WCDMA Call Drop Problems Analysis
Call drop problems analysis process

General call drop analysis flow

Categories for call drop reasons

Call drop problems analysis process

General call drop analysis flow:

 Call drop problems analysis process
General call drop analysis flow2:
 Call drop problems analysis process
General call drop analysis flow2:
 Call drop problems analysis process

Call drop location analysis: based on the location of the call drop event in the map
window in the post processing tool
Neighbor list analysis: to find out any cell not defined in the neighbor list
Analyze the pilot coverage to make sure whether following coverage events take
place or not: Coverage limited, System interference, Poor uplink coverage, Poor
downlink coverage, pilot pollution
Handover analysis to make sure whether following cause exist or not: insufficient
handover area, too late to start CM, too late to add target cell, too early to delete
serving cell
Signaling analysis is used for those call drops that are still confused about the
exact reason through analysis mentioned above
 Call drop problems analysis process

Categories for call drop reasons:

1. RF problems
2. Equipment problems
RF problems usually can be find out by neighbor list analysiscoverage analysis

handover analysis, while signaling analysis is helpful to equipment problems.

Case study on call drop problems

RF concerned problems
1. Neighbor missing
2. Coverage Limited
3. Handover problems
Equipment concerned problems
1. UE problem
2. Data configuration problem
Neighbor list analysis

To analyze Neighbor list:

to find out any cell not defined in the neighbor list.
the best serving 3G cell before the call dropped
the best serving 3G/2G cell after the call dropped
the existing neighbor list of the best serving 3G cell
intra-freq HO neighbor list
inter-freq HO neighbor list
inter-RAT HO neighbor list
Neighbor missing
Call drop location-2-ScannerEc/I0 : There is RSCP and Ec No level is
serving cells is going bad , there is one cells has better Rscp and Ec no then
serving cells , but not handover to it due to no neighbor definition between
each others
Neighbor missing
Call drop location-3-ScannerBestserver :
Neighbor missing
Before call drop, SC489 goes poor, while SC504 is good the moment before drop,
according to the measurements by UE shown below; but SC03 which is not
measured by UE is becoming good gradually :
WEAK Coverage
RSCP and Ec/No is got to bad.. It means there are weak / Poor coverage..
Should to check site / cell location , serving area and recommendation about
antenna direction change , tilt change , Pcpich Power change , MaxTx Power
change , cell addition . Carrier addition , New site..
Strong Interferences
There is RSCP is good , Ec No is bad , it means there is a strong interferences.. Firstly we
should to try to find is it causes by internal or external.. And then we should to find
solution for each type problem..
CONGESTION
During the handover , cell cannot add to active set list due to RRC Connection
fail.. There is possible to some kind congestion on target cells.. Need check
congestion trend of target cells..
Pilot Pollution
No Dominance
Case study on call drop problems

RF concerned problems
1. Neighbor missing
2. Coverage Limited
3. Handover problems
Equipment concerned problems
1. UE problem
2. Data configuration problem
 Coverage analysis
To analyze the coverage:
the pilot coverage
CPICH transmission power
Coverage limited
System interference
Poor uplink coverage
Poor downlink coverage
pilot pollution
the service coverage
Service related Maximum downlink transmission power
SIR before the call dropped
Max uplink transmission power allowed for UE
Actual uplink transmission power before the call dropped
Coverage limited
Call drop location-1-ScannerEc/I0 :
Case study on call drop problems

RF concerned problems
1. Neighbor missing
2. Coverage Limited
3. Handover problems
Equipment concerned problems
1. UE problem
2. Data configuration problem
Handover analysis

To analyze the handover:

the signal change
Source cell
Target cell
insufficient handover area
Too late to add new cell
Too early to delete old cell
ping-pang handover
Handover problem
Call drop caused by handover problems, is helpful for us to get solutions to
parameters optimization. Heres an example. Call drop place is shown below:
Handover problem
The drop call occurred in the area of frequent change of best server shown by the
scanner :
Case study on call drop problems

RF concerned problems
1. Neighbor missing
2. Coverage Limited
3. Handover problems
Equipment concerned problems
1. UE problem
2. Data configuration problem
RRC Rej Fail Reason
RRC Setup Failure\Solution
RRC.FailConnEstab.NoReply counter is generally arises from the following
resources..
Transmission Problem:
Relative alarms to identify faults on the transmission path or the transmission boards of RNC

NodeB
Congestion Problem:
Check the Admission Control thresholds.
Take appropriate measures to relieve congestion, e.g.
activate LDR (Load Reshuffling), OLC (Overload Control) algorithms, and to increase capacity.

RF Problem:
Check coverage in the failure points.
Check if most failures occur in cell border (most probably they are).
Check power. ( Max Tx , Pcpich )
Check DL interference in the cell: is there a pilot pollution issue?
Check UL interference in the cell.
Failure Analysis/RRC Rej. Failure
Failure Analysis/CS RAB Setup Failure
Failure Analysis/PS RAB Setup Failure
RAB Setup Failure Reason
RAB Setup Failure Reason
The RAB failures caused by unsupported configuration and congestion are
similar with those of RRC procedure , following counters count the failure..

RAB CS Fail Chaking List

Transmission Problem:
Check transmission issue on Iu - CS interface;
check relative alarms and its history.

RF Problem:
Check invalid parameters
Check inter RAT HO and if the failure point is in RNC border
Check the relative RB Setup failure counters to get more details on the failure cause

Congestion Problem:
Check the Admission Control thresholds.
Take appropriate measures to relieve congestion, e.g.
activate LDR, OLC algorithms, and to increase
capacity
Failure Analysis/AMR Call drop
Failure Analysis/AMR Call drop
AMR Call Drop Reason / RF Problem
AMR Call drop actualy arises due to following problems..

Check for missing neighbors

Check for pilot pollution (adjust physical )config

Check for UL interference.

Check VS.MeanRTWP counter in order to see the value of UL interference in the cell. If the value is higher than -97
dBm , then interference exists in the UL.

Check internal interference .Internal interference is usually caused by faulty connections in the antenna line.

Check thoroughly all relative connection

Check external interference ..External interference is caused by external sources (e.g. TV/Radio stations, military
equipment, other networks equipment, etc.).External interference will appear randomly throughout the day. Its
direction will be specific and it will affect more than one sites in the area.

Check neighbouring sites to see if they face the same problem.In case of poor coverage, adjust physical
config
AMR Call Drop / Non-RF Problem

Drops due to OM intervention, cell was blocked

Drops due to UTRAN generated reasons..Indicates hardware failure on RAN equipment

Check alarms in order to identify the faulty part..Repair or replace the faulty part once identified.

Drops due to congestion for Cell

Drops due to AAL2 failure

Check transmission alarms to identify possible faults in the Iu-CS transmission path
Failure Analysis/PS Call Drop
Failure Analysis/PS Call Drop
PS Call Drop / Rf Problem
PS Call drop actualy arises due to following problems..

Check for missing neighbors

Check for pilot pollution (adjust physical config)

Check for UL interference. Check VS.MeanRTWPcounter in order to see the value of UL interference in the cell. If the
value is higher than -97 dBm , then interference exists in the UL.

Check internal interference..Internal interference is usually caused by faulty connections in the antenna line. Check
thoroughly all relative connection

Check external interference.External interference is caused by external sources (e.g. TV/Radio stations, military
equipment, other networks equipment, etc.).External interference will appear randomly throughout the day. Its
direction will be specific and it will affect more than one sites in the area.

Check neighbouring sites to see if they face the same problem.In case of poor coverage, adjust physical config
PS Call Drop / Non-Rf Problem
PS Call drop actually arises due to following problems..

Drops due to OM intervention, cell was blocked

Drops due to UTRAN generated reasons

Indicates hardware failure on RAN equipment

Check alarms in order to identify the faulty part Repair or replace the faulty part once identified.

Drops due to congestion for Cell

Check transmission alarms to identify possible faults in the Iu-PS transmission path.
LOW HSDPA / HSUPA Throughput

Check radio environment in the problematic cell Poor coverage is directly related with low HSDPA throughput.
Enhance coverage by appropriate tuning of antenna parameters (tilt, azimuth).

Check for pilot pollution. In case pilot pollution exists in the area, try to adjust tilts and/or azimuths of relative
sites..

Check for ping-pong serving cell change based on 1D event: ping-pong limits throughput.. If this is the problem,
tune event 1D parameters in order to eliminate Ping pong. Consider also the value of the HspaTimerLen
parameter. (event 1D: Change of best cell)

Check for hardware/software alarm in the site

Check transmission whole network thoroughly..

Possibility of bottleneck in the transmission chain (e.g. too many sites are served by a single low capacity
router).

Check Iu-PS interface. Check for faults (relative alarms) and its capacity. Make sure that the configured Iu-PS
capacity is not a bottleneck for PS service demands
Weak Coverage
Weak coverage arises ; Cross-cell coverage, Unbalance uplink and downlink , No primary pilot cell

Check the NodeB hardware equipment.

Check the alarms.

Conduct DT in the area of poor coverage to confirm the problem.

Measure RSCP and Propagation delay. If RSCP is low while Propagation delay is low as well, this indicates poor coverage
close to the base station.

Survey the environment Check for shadowing effect caused by object obstacles in the area. This might cause low signal
strength close to NodeB.

Adjust physical config (tilt, azimuth) appropriately in order to Optimise the coverage in the problematic area.

Check the CPICH power setting. Default value is 33 dBm Consider increase/decrease if needed

Increase the power amplifier output usually initial 3G output is 20W. Consider upgrading to 40W or even to 60W.

This will give extra margin to increase CPICH power and RL power.
INTERFERENCES

Check for pilot pollution in the area

In case pilot pollution exists in the area Adjust tilts and/or azimuths of relative sector

Check for missing neighbors. Missing neighbors can cause increase of interference in the source cell.

Check whether the interference is from an external source

Check for nearby sources of E/M radiation: TV/Radio stations, Military, Civil aviation, etc.
Overshooting Analysis
1 Prach = 0.78 meter
1 TP = 3*PRACH ( TP : Time Propagation )
Chart below shows all cells propagation samples(PRACH) and cells which are overshooting.

Total sample time propagation is greater than %15 serving the more than 55 TP cells are calculated..
Totally : 60 Cells.. ( Find in attachment file pls.. )

Propagation Overshooting
Delay meter
TP.UE.0 0-233
TP.UE.1 234
TP.UE.2 468
TP.UE.3 702
TP.UE.4 936
TP.UE.5 1170
TP.UE.6.9 1170-2106
TP.UE.10.15 2106-3510
TP.UE.16.25 3510-5850
TP.UE.26.35 5850-8190
TP.UE.36.55 8190-12870
More Than
TP.UE.More55 12870
Cell availability

Availability is THR2 is looking normal.. A lot of day , a lot of cells

temporary down..
Band Traffic Load
Consistency Check / Pcpich Power Between Co-
Carriers

There are 195 cells has different PCPICH Power set`s on

RNC TH1RNCH2..

You can find in attachment files which cells has different Pcpich settings
after filter by the red colors.. ( firstly filter the RNC column , secondary filter the site column
by the red color )
 RTWP check
External Interference Check by the Spectrum analyzer
Antenna Inter Modulation Check
Antenna Connector Check
Antenna Feeder check
IC & Turbo IC Interference Cancelation Parameter Try which
cells doesnt has external problem and which sites has
WbbpF4 or UBBPD3 type CE Card`s
SC Utilization
Cell ID Cell Name DL UARFCN PSC City Usage Num
PSC Usage of THR1RNCH2 is good.. There 49441 MAZ0238-MU-A 10712 109 TEHRAN 2
is only 1 consistency in Tehran city for 49442 MAZ0238-MU-B 10712 110 TEHRAN 2
RNC2 .. Two different site`s using the 49443 MAZ0238-MU-C 10712 111 TEHRAN 2
49581 MAZ0325-MU-A 10712 109 TEHRAN 2
same screambling code in Tehran City..
49582 MAZ0325-MU-B 10712 110 TEHRAN 2
Please change one of them.. 49583 MAZ0325-MU-C 10712 111 TEHRAN 2
Paging analysis/PS Paging

PS Paging is looking good.. PS Paging Loss Rate

is very low..
Paging analysis/Paging CS Paging

CS Paging is looking good.. CS Paging Loss Rate is very low..

TCP utilization
R99 TCP utilization Chart below includes average one week busy hour
data. TCP Utilisation is not good.. Most of cells has between 90-100
% utilization.. Need to change Power distribution..
CPU utilization

Max/Mean loads of some subsystem are up to 70%, as a critical level.. Chart

below includes average one week busy hour data. Need to 4 th Subrack.. And
after that Rehome some sites to new subrack..
 Summary
Weve discussed of several kinds of call drop, so typical they are as mentioned
above. Engineers may meet with call drops that seem more puzzling. Taking no
account of equipment problems, RF problems can be solved by suggestions below
mostly:

1. If coverage is poor, we can reduce the downtilt and adjust the azimuth, or we can increase
the pilot transmit power or maximum downlink transmit power for service. The negative
effect: is other places may be interfered, and soft handover ratio maybe higher.

2. If the interference is strong, first make sure whether it is internal network interference or
external network interference. If it is internal network interference, find the interference
source cell, increase the downtilt and adjust the azimuth, or reduce the pilot transmit power
or maximum downlink transmit power for the service. The negative effect is coverage in other
places may become discontinuous, and soft handover areas maybe shrink.

3. As for the handover area is insufficient, and if its too slow to add the target cell, we can
modify corresponding 1a event parameters. If its too fast to delete the serving cell, we can
modify corresponding 1b event parameters. The negative effect is other places may be
interfered and soft handover ratio maybe increase.