o046 - umts pre-launch optimisation_26 & 27 march_ncell

1 © 2012 AIRCOM International Ltd

O046 - UMTS Pre-Launch Optimisation


Session Objectives

• The objective of this two days course is to provide the delegates with knowledge of optimisation techniques which will enable them to plan and optimise UMTS network.


Agenda of TrainingCourse Content(Pre-Optimization)

• Optimization Overview• WCDMA Power Budget• Pilot Pollution and Power Setting of common channels• Factors Limiting Capacity• Handover Concepts• Scrambling Code Planning• Assessing a Plan


UMTS Evolution

BSC

PSTN MSC HLR, etc

GSM Architecture

Circuit Switched

BTS


UMTS Evolution

BSC

Serving GPRS Support Node

Gateway GPRS Support Node

Internet

PSTN

PSDN

MSC HLR, etc

Adding GPRS

Packet Switched

BTS

Frame Relay


UMTS Evolution

BSC

Serving GPRS Support Node

Gateway GPRS Support Node

Internet

PSTN

PSDN

MSC HLR, etc

RNC

BTS

Node B

Adding UMTS

ATM

So it’s just a new modem then


UMTS Evolution


Major Interfaces in UMTS There are four major new

interfaces defined in UMTS

Iu

The interface between UTRAN and the CN

Iur

The Interface between different RNCs

Iub

The interface between the Node B and the RNC

Uu

The air interface

RNC

Node-B

RNC

UE

CN

Uu

Iu

Iub

Iur


Iu - the Core Network to UTRAN Interface There are two parts to the Iu interface

Iu-ps connecting UTRAN to the PS Domain of the CN Iu-cs connecting UTRAN to the CS Domain of the CN

No radio resource signalling travels over this interface The Iu interface divides the UMTS network into the radio specific

UTRAN and the CN responsible for switching routing and service provision

RNC

Node-B

RNC

UE

CN

Uu

Iu

Iub

Iur


Iur - the Inter-RNC Interface

The Iur interface allows soft handovers between Node-Bs attached to different RNCs

It is an open interface to allow the use of RNCs from different manufacturers

Its functions may be summarised: Support of basic inter-RNC mobility Support of Dedicated and Common Channel Traffic Support of Global Resource Management

RNC

Node-B

RNC

UE

CN

Uu

Iu

Iub

Iur


Iub - the RNC to Node-B Interface The Iub is an open interface to allow the support of different

manufacturers supplying RNCs and Node-Bs Its major functions are:

Carries dedicated and common channel traffic between the RNC and the Node-B

Supports the control of the Node-B by the RNC

RNC

Node-B

RNC

UE

CN

Uu

Iu

Iub

Iur


Uu - the Air Interface

Clearly the Uu must be standardised to allow multiple UE vendors to be supported by a network

The major functions of the Uu are to: Carry dedicated and common channel traffic across the air interface Provide signaling and control traffic to the mobile from the RNC and

the Node-B

RNC

Node-B

RNC

UE

CN

Uu

Iu

Iub

Iur


UMTS Compared to GSM

UMTS GSM Carrier Spacing 5MHz 200kHz

Frequency Reuse Factor

1 1-18

Power Control Frequency

1500Hz 2Hz or lower )

Quality Control Radio Resource Management

algorithms

Frequency Planning and Network Optimisation

Frequency Diversity 5MHz bandwidth gives multipath diversity with

rake reciever

Frequency Hopping

Packet Data Load Based Packet Scheduling

Time Slot based Scheduling with GPRS

Transmit Diversity Supported to improve downlink capacity

Not supported by standard but may be

applied


GSM 9.6Kbps 9.6KbpsGPRS 40Kbps 171KbpsEDGE 120Kbps 473KbpsR99 384Kbps 2.0MbpsR5(HSDPA) 7.2Mbps 14.4Mbps

Peak data rate(Typical Deployment)

Peak data rate(Theoretical Maximum)

UMTS Evolution


UMTS Evolution


What is Optimisation ?

• Should involve major improvements plan for the network.

• Fine tuning of Radio Interface and Network Parameters.

• Key issues

• Coverage• Capacity• Interference• Functionality(Qos)


Pre-launch Optimisation

• Plan (using a planning tool)

• Assess and Improve (“optimise the plan”)

• Build

• Test

• Diagnose Problems

• Rectify

Pre-launch optimization phase


Post-launch Optimisation


Network Dimensioning and Planning


WCDMA Power Control


WCDMA Power Control

Example:PtxCPICH=33dBm (Parameter per Node-B)

DL RSCP = -80dBm (Measured by UE)UL_IF = –80 dBm(RTWP is received Total Wideband Power(uplink interference)

measured by RBS)UL_Required_SIR = -25 dB (Parameter per Node-B)

UE PRACH First Preamble Power = 33 dBm – (-80 dBm) + (-80 dBm) + (-25 dB) = 8 dBm

3GPP TS 25.331 8.5.7)


WCDMA Power Control


Random Access Procedure



• UE transmits the first preamble with the power determined by UL open loop PC• If the UE does not detect any acquisition indicator in AICH, it increases the

preamble Tx power by a specified offset Po

• If the UE detects the positive indicator in AICH, it transmits the random access message, 3 or 4 access slots after the UL access slot of the last transmitted preamble

• The Tx power of the control part of random access message should be Pp-m higher than the last transmitted preamble power

• The required power offset values for random access procedure PowerOffsetLastPreamblePRACHmessage in PRACH(Pp-m)

PowerRampStepPRACHpreamble (Power Ramp Step)(Po)



• The power ramp-up process will continue until

1) A positive AI is received from the network Send RACH message

2) A negative AI is received from the network Exit RACH procedure

3) RACH_preamble_retrans value is exhausted

4) TX power exceed UEtxPowerMaxPRACH value by > 6dB Exit RACH procedure

• When the RACH_preamble_retrans value is exhausted, PRACH preamble power will be re-set to the initial value of the cycle and a new power ramp-up cycle initiated. The preamble power ramp-up cycle will be repeated RACH_tx_Max times. At this stage the UE will send a RACH failure message to the network.

• The maximum allowed UE transmit power for the PRACH procedure is defined by UEtxPowerMaxPRACH. Layer 1 of the UE controls the UE transmit power during the PRACH procedure using the ‘commanded transmit power’. If the commanded transmit power exceeds the maximum allowed transmit power then the UE transmits the maximum allowed transmit power.


BS RNC

UL Outer Loop Power Control

• Outer PC loop is performed to adjust the TARGET SIR in BS/UE, according to the needs of individual radio link. Required SIR depends on

• UE speed• Changes in the propagation conditions• Available multipath diversity• UE power control dynamics• SHO branches (Macro Diversity Combining)

• SIR is constantly adjusted in order to maintain a constant QUALITY, usually defined as a certain BLER target of the transport channel

• BLER is measured for each transport channel separately

DL Outer LoopPower Control

Outer Loop Power Control


Uplink OLPC

UL OuterLoop PC

Entity #N

UL OuterLoop PC

Entity #1

UL Outer Loop PCController

RNC

BTS 1

UL Fast Closed

Loop PC

BTS 2

UL Fast Closed

Loop PC

UL Outer Loop PC In the RNC the functionality of the UL

outer loop PC is divided into two parts:

Þ UL outer loop PC Controller, one for each RRC connection

Þ UL outer loop PC Entities, one for each transport channel multiplexed in the same radio link


Uplink OLPC Entities

There is one UL outer loop PC Entity for each transport channel in the RNC.

This UL OLPC Entity calculates the required change in SIR Target according to UL quality estimates (CRC).

One of UL OLPC Entities under the same radio link is selected to transmit the New SIR Target to the WCDMA BTS.

UL OuterLoop PC

Entity #N

UL OuterLoop PC

Entity #1


RNC

BTS 1

UL Fast Closed

Loop PC

BTS 2

UL Fast Closed

Loop PC

UL Outer Loop PC


Uplink OLPC Controller An UL Outer Loop PC Controller controls all

UL OLPC Entities under the same RRC connection.

The UL OLPC Controller sets the parameters for each UL OL PC Entities at the RAB Setup/Modification.UL

OuterLoop PC

Entity #N

UL OuterLoop PC

Entity #1


RNC

BTS 1

UL Fast Closed

Loop PC

BTS 2

UL Fast Closed

Loop PC

UL Outer Loop PC


Fast Closed Loop Power Control


Processing Gain(Gp dB)


Logical Channelscontent is organised in separate channels, e.g.

System information, paging, user data, link management

Transport Channelslogical channel information is organised on transport channel

resources before being physically transmitted

Physical Channels(UARFCN, spreading code)

FramesIub interface

Channel Mapping DL (Network Point of View)


P-CCPCH

PCH

BCH

CTCH

DCCH

CCCH

PCCH

BCCH

DCH

P-CPICH

S-SCH

P-SCHFACH

HS-DSCH

AICH

HS-PDSCH

DPDCH

S-CCPCH

DTCH

PICH

LogicalChannels

TransportChannels

PhysicalChannels

DPCCH

Channel Mapping DL (Network Point of View)

HS-SCCH


Logical Channels

Dedicated user data can be transmitted point to multiple to a group of UEs


Common Control Channels BCH Broadcast Channel FACH Forward Access Channel PCH Paging Channel RACH Random Access

Channel

Dedicated Channels DCH Dedicated Channel DSCH Downlink Shared

Channel

Transport Channels


Carrying the Transport Channels

Logical Channels

BCH

FACH

PCH

RACH

DCH

DSCH

Physical Channels

Primary Common Control Physical Channel (Primary CCPCH)

Secondary Common Control Physical Channel(Secondary CCPCH)

Physical Random Access Channel (PRACH)

Dedicated Physical Data Channel (DPDCH)

Dedicated Physical Control Channel (DPCCH)

Physical Downlink Shared Channel (PDSCH)

Synchronisation Channel (SCH)


The Common Control Channels

The Broadcast Channel (BCH) is a cell-wide channel that is used to broadcast system and cell-specific information. The BCH is always transmitted over the entire cell with a low fixed bit rate.

The Paging Channel (PCH) is a cell-wide channel that is used to carry control information to a UE when the system does not know the location cell of the UE

The Forward Access Channel (FACH) is a downlink channel that is used to carry control information to a UE when the system knows the location cell of the UE. May also carry short user packets. (what is the use of FACCH in GSM)

The Random Access Channel (RACH) is an uplink control channel from the UE. May also carry short user packets..


DCCH

DCH DPDCHDTCH

LogicalChannels

TransportChannels

PhysicalChannels

RACHCCCH PRACH

DPCCH

Channel Mapping UL (Network Point of View)

HS-DPCCH


Power Setting for DL Common Channel

DL Common Control Channel

• DL Common control channels must be heard over the whole cell, thus their power setting is designed for “cell edge”.• The power of the common physical channels are set relative to the CPICH

Parameters Default (Relative) Default (Absolute)

PtxPrimaryCPICH 33 dBm 33 dBmPtxPrimarySCH -3 dB 30 dBmPtxSecSCH -3 dB 30 dBmPtxPrimaryCCPCH -5 dB 28 dBmPtxSCCPCH 1 (SF=64) 0 dB 33 dBmPtxSCCPCH 2 (SF=256) -5 dB 28 dBmPtxSCCPCH 3 (SF=128) -2 dB 31 dBmPtxPICH -8 dB 25 dBmPtxAICH -8 dB 25 dBm


• By default the CPICH consumes 2 W of the Node B power (20 W )• For 40 W default is 4 W (10 %)

• CPICH power is used to derive the power requirements of the other Common Control Physical Channels (CCPCH)

Pilot Channel Power Setting


Effects CPICH Power modification


Secondary CCPCH

The Secondary CCPCH (Common Control Physical Channel) carries FACH and PCH transport channels.

FACH(Forward access channel) used for small amount of data used for transport of signaling message & user data No fast power control used

PCH(Paging Channel)Broadcast into the entire cell Support efficient sleep mode procedure.Used for transport of paging message.


Pilot Pollution

• Pilot pollution is a situation in which a mobile station receives several pilot signals with strong reception levels, but none of them is dominant enough that the mobile can track it.


Pilot Pollution Example

We can also see 5 scrambling codes, all within 5dBs of each other. This is clearly an area suffering from pilot pollution.

RSCP is –91dBm but Ec/Io is poor –10dB

How do you reduce Pilot Pollution?


Pilot PollutionSite Name Sector ID SC Pilot Pollution Events RSCP EcNo DL Interf.

KAT718 B 146 679 -77.84 -9.58 6.42

KAT728 C 7 474 -79.81 -10.92 7.98

KAT706 A 415 371 -71.2 -10.32 7.15

KAT904 C 58 287 -81.17 -8.42 4.86

KAT766 A 454 237 -72.55 -9.17 5.37

KAT844 C 507 235 -73.16 -9.82 6.54

KAT718 A 126 228 -76.63 -10.02 7.02

KAT957 A 171 196 -70.59 -10.36 6.72

KAT713 B 374 189 -71.68 -10.02 6.57

KAT884 A 499 187 -70.26 -8.64 4.99

KAT843 C 435 184 -83.09 -10.35 6.93

KAT818 B 413 172 -64.38 -8.92 5.31

KAT769 B 473 159 -71.7 -8.9 5.18

KAT868 A 478 154 -70.62 -9.18 5.87

KAT830 C 477 150 -74.4 -10.37 7.18

KAT1098 C 271 148 -78.78 -9.39 5.92

KAT729 A 493 148 -77.07 -11.32 8.48

KAT1106 B 24 147 -71.69 -9.19 5.97

KAT874 B 53 147 -77.78 -10.56 7.49

KAT1108 A 131 145 -68.76 -9.82 6.72

KAT1106 C 35 140 -72.87 -9.47 6

KAT777 A 457 138 -71.61 -10.52 7.33

KAT834 B 392 119 -88.99 -10.47 7.41

KAT753 B 497 115 -68.99 -10.32 7.05

UMTS Pilot Pollution Events


Factors Limiting Capacity

Link Budget-DL


WCDMA Handover Principal and Analysis


Handover


• Why mobile systems need handover?

• UE mobility(Seamless connectivity)

• The mobile system is composed of cells which the coverage ability is limited.

The Purpose of Handover

• Providing the continuous service in mobile system is the basic element in QoS.

• The load balance: sharing the resource


The Basic Concepts of Handover

• Active Set• Monitored Set• Detected set • Event reporting

Event reporting Radio Link (RL)

• Combination way: maximum ratio combination selection combination

• The soft handover gain• Soft handover, softer handover, hard handover


Types of Handover• According to the signaling characters:

• Soft handover (softer handover)• Hard handover

• According to the properties of source cell and target cell• Intra-frequency handover• Inter-frequency handover• Inter-mode handover (FDD <-> TDD)• Inter-system handover (UMTS <-> GSM/CDMA2000)

• According to the purpose of handover• Based on Coverage• Based on Load (Optional)• Based on mobility of UE (Optional)• Based on Service (Optional)


Characters of Different Handovers

Comparison between soft handover and hard handover:

Item Soft Handover Hard Handover

The numbers of RL in active set after handover

Several One

Interruption during handover

No Yes

The frequencies of cells

Only possible in Intra-frequency

cells

Occurs in Intra-frequency cells or Inter-frequency

cells


Characters of Different Handovers

Comparison between soft handover and softer handover:

• During softer handover, the uplink signaling are combined in NodeB by maximum ratio combination, but during soft handover they are combined in RNC by selection combination.

• Compare to later one, the maximum ratio combination give more gain. So the performance of maximum ratio combination is better.

• Since softer handover is completed in NodeB, it does not consume a lot of transport resource of Iub.


Softer Handover

RNC

NodeB


Hard Handover


Hard Handoff vs. Soft Handoff

Hard Handoff

Soft Handoff

Continuity of call quality is maintained and Dropped calls are minimized

Continuity of call quality is maintained and Dropped calls are minimized


Three Steps of Handover

Decision

Execute

Measurement

• Measurement• Measurement control• Measurement execution and

the result processing• The measurement report• Mainly accomplished by UE

• Decision • Based on Measurement• The application and

distribution of resource• Mainly accomplished by RRM

in RNC

• Execution• The process of signaling• Support the failure drawback • Measurement control refresh


Basic Concepts of Measurement• Measurement values of Handover

• Intra-frequency and inter-frequency: • CPICH RSCP, CPICH Ec/No, Path loss

• Inter-frequency：• CPICH RSCP, CPICH Ec/No

• Inter-system：• GSM Carrier RSSI, BSIC Identification, BSIC Reconfirmation

• Reporting methods of measurement• Periodic reporting • Event reporting

• The events of reporting• Intra-frequency events： 1A,1B,1C,1D,1E,1F• Inter-frequency events ： 2D,2F,2B,2C• Inter-system events ： 3A,3C• Others： 6G,6F


Intra-frequency Measurement EventsIntra-frequency measurement events are identified with 1x :

• 1A : A primary pilot channel enters the reporting range. If active set of UE is full, UE stops reporting 1A event;

• 1B : A primary pilot channel leaves the reporting range;

• 1C : The primary pilot channel in a non active set is better than the primary pilot channel in an active set;

• 1D : The best cell changes;

• 1E : The measurement value of a primary pilot channel exceeds the absolute threshold

• 1F : The measurement value of a primary pilot channel is lower than the absolute threshold


Inter-frequency Measurement EventsInter-frequency measurement events are identified with 2x:

• 2A : The best frequency changes

• 2B : The quality of the current cell frequency is lower than a certain threshold, but that of the non-used frequency is

higher than a certain threshold

• 2C : The estimated quality of the non-used frequency is higher than a certain threshold

• 2D : The estimated quality of the used frequency is lower than a certain threshold

• 2E : The estimated quality of the non-used frequency is lower than a certain threshold

• 2F : The estimated quality of the used frequency is higher than a certain threshold


Inter-system Measurement Events

Inter-system measurement events are identified with 3x:

• 3A: The estimated quality value of the used UTRAN frequency is lower than a certain threshold, and that of the other system is higher than a certain threshold;

• 3B: The estimated quality value of the other system is lower than a certain threshold ;

• 3C: The estimated quality value of the other system is higher than a certain threshold ;

• 3D: The best cell in the other system changes


Introduction of Soft Handover

• Soft Handover Features

• UE has several RLs with different cells----active set.

• The handover among different cells which are in same RLS is softer handover.

• Soft handover Combination:• Selection combination in uplink• Maximum combination in downlink

• Softer handover Combination:• Maximum combination in uplink and downlink


Introduction of Soft Handover• Advantages

• Soft handover gain:• Multi-Cell gain: Multiple unrelated radio links can reduces the

required fading margin.• Macro Diversity Combining gain: Gain for the link demodulation

of the soft handover:

• Load balance: • Different cells receive the signal from a UE in uplink, which can

decrease the transmission power of UE. • Similarly, UE receive signal from different cells, which also can

decrease the required transmission power of base station.• Decrease the possibility of call drop caused by ping-pong handover.

• Disadvantages

• More resource needed in downlink, especially for the code resource of BE service.


Measurement of Soft Handover • The measurement of soft/softer handover

• Measurement value： CPICH RSCP, CPICH Ec/No, Pathloss

• Process of Measurement： Layer 1 filter, Layer 2 filter

• Reporting way

• Periodic reporting • Event reporting

• Event type： 1A, 1B, 1C, 1D, 1F• Reporting rules: Trigger condition, Relative threshold (or

Absolute threshold), Hysteresis, Time_to_Trigger• Event reporting to periodic reporting


Key Parameters To Optimize• Relative threshold

• Set 1A, 1B value separately • 1A < 1B， which makes deleting RL is more difficult, and it can avoid

ping-pong handover• Usually 1A: 3dB; • 1B: 6dB

• Time to trigger• Each event can be set separately• Usually, 1B>1A， which makes deleting RL is more difficult, and it can

avoid ping-pong handover• Usually, 1A: 320ms, 1B: 640ms

• Layer 3 filter coefficient• Only one value for all intra-frequency measurement• Sensitive to the delay of event trigger and ping-pong handover• Usually： 3


Inter-frequency Hard Handover Measurement Values and Events

• Inter-frequency hard handover measurement values

• Measurement values:• CPICH RSCP, CPICH Ec/No

• Different handover purpose for different measurement type:• At the edge of carrier coverage: CPICH RSCP• At the center of carrier coverage: CPICH Ec/No


Compressed Mode Initiation in Inter-frequency Hard Handover

• Conditions to initiate Compressed Mode (CM) measurement

• 2D event• Used to enable the compressed mode to perform inter-

frequency measurement.

• Conditions to stop measurement

• 2F event• Used to stop compressed mode. When used frequency

quality exceeds the threshold.


Inter-frequency Hard Handover Decision Algorithm

The inter-frequency hard handover decision

• Coverage trigger handover• 2B event：

• the quality of current serving cell is lower than absolute threshold, but the quality in other cell is higher than another absolute threshold.

• Both cells are of different frequency

• Load triggers handover• 2C event：

• the quality of another frequency is higher than an absolute threshold


Introduction of Inter-system Hard Handover

• Application scenarios • WCDMA FDD <－ >GSM• WCDMA FDD <－ >WCDMA TDD• WCDMA FDD <－ >CDMA2000


Measurement for Inter-system：Compressed Mode Initiated

• The inter-system measurement (GSM measurement)• Measurement type:

• GSM Carrier RSSI• BSIC Identification

• Measurement reporting• Event reporting

• 2D Event: initiate GSM measurement• 2F Event: stop GSM measurement


Inter-system Hard Handover Decision Algorithm

• The inter-system hard handover decision

• Inter-system handover due to coverage issue• Event reporting:

• 3A event：• The estimated quality value of UTRAN frequency is lower than a

certain threshold, and that of the other system is higher than a certain threshold

• Periodic reporting:• Evaluation： According to periodic report GSM RSSI

measurement value and the BSIC confirming state of target cell of GSM system, and UE evaluates GSM RSSI of target cell is greater than the absolute threshold, then consider the cell.


Key Parameters (I)• Parameters for Inter-system handover

• Inter-system measurement initiated and stopped threshold: • Considering different demands of CPICH Ec/No and CPICH RSCP

for PS domain and CS domain, the different 2D and 2F parameters are configured

• Inter-system measurement values (2D, 2F)• CPICH Ec/No• CPICH RSCP

• Configure the GSM RSSI threshold of CS domain and PS domain separately

• Using inter-system frequency quality handover threshold

• Trigger time delay, Hysteresis for each event


Purpose of Compressed mode• Purpose：

• Measure the inter-frequency cell or inter-system cell under FDD mode

• Cause:• Since one receiver only can work in one frequency, the UE has

to stop working in current frequency if it is going to measure the signal from another frequency cell. To ensure the downlink service unaffected, the remained data should be sent in the limited time.


Compressed Mode Sketch Map

One frame(10 ms) Transmission gap available for

inter-frequency measurements


Realization Methods of Compressed mode• CM Methods

• Reduce SF by half• This double the data rate. But since amount of data not changed, it

halves the time in which it is sent, open up a gap.

• Puncturing• Decrease the coding redundancy

• Higher layer scheduling• Higher layer permit only some transport format to be used in CM, to

generate gap. Appropriate for variable-rate service.


Scrambling Code

Scrambling Code are not orthogonal codes so they don’t required synchronization. UL: separates terminals(different UE’s) DL: Separates the sectors.

• In DL long SC are used. They are 2^18-1 i.e around 262143 In order to speed up the cell search procedure only we are uses 8192 codes out of 262143. 8192 further divided into 512 sets each sets consist of primary SC & secondary SC.

In UL there are 2^24 long & 2^24 short SC(length of 256 chips) uplink Scrambling code are available. UL scrambling code are Cell specific and are allocated in the time of connection establishment by the RNC ,Each RNC has its own planned range.


Scrambling Code Planning

Scrambling Code allocation for Indoor & outdoor

• The Total Number of SC is 512 codes. They are separated in 4 groups outdoor (phase 0),outdoor(Future),indoor(phase0) & indoor(future)


Scrambling Code Planning

• A cell must be allocated 1 of a possible 512 scrambling codes. The scrambling code is the pilot channel. The mobile uses this to synchronise to so that it can demodulate traffic channels and common control channels. It is clear that satisfactory network operation requires that a mobile receive a particular pilot channel from a clearly identifiable cell.

• If it receives the same pilot channel from two or more cells, confusion will result. The 512 codes are divided into 64 groups with 8 codes in each group. There are advantages if the number of codes per group is restricted or if the number of groups used is restricted.

• These advantages are in the form of:

• Handover time/success

• Mobile battery life


Cell Synchronisation

• Chips synchronisation

• Acquire slot synchronisation

• Acquire frame synchronisation

• Identify the code group of the cell found in the first step

• Determine the exact primary scrambling code used by the found cell

• Measure level & quality of the found cell

Phase 1 – P-SCH

Phase 2 – S-SCH

Phase 3 – P-CPICH


Cell Synchronisation

• Primary Synchronisation Channel (P-SCH)

• The P-SCH only uses the first 10% of a time slot

• A Primary Synchronisation Code (PSC) is transmitted the first 256 chips of a time slot. This is the case in every UMTS cell.

CP CP

2560 Chips 256 Chips

CP CP CP

Primary Synchronisation Channel (P-SCH)

Slot 0 Slot 1 Slot 14 Slot 0

10 ms Frame


Cell Synchronisation (S-SCH)

• Secondary Synchronisation Channel (S-SCH)

• The S-SCH also uses only the first 10% of a timeslot

• Secondary Synchronisation Codes (SSC) are transmitted

• There are a total of 512 primary scrambling codes, which are grouped in 64 scrambling code families, each family holding 8 scrambling code members


15

15

Scramblingcode group

group 00

group 01

group 02

group 03

group 05

group 04

group 62

group 63

1 1 2 8 9 10

15 8 1

016 2 7 1

5 7 16

1 1 5 16 7 3 1

416 3 1

0 5 12

14

12

10

1 2 1 15 5 5 1

216 6 1

1 2 16

11

12

1 2 3 1 8 6 5 2 5 8 4 4 6 3 7

1 2 16 6 6 1

1 5 12 1 1

512

16

11 2

1 3 4 7 4 1 5 5 3 6 2 8 7 6 8

9 11

12

15

12 9 1

313

11

14

10

16

15

14

16

9 12

10

15

13

14 9 1

415

11

11

13

12

16

10

Slot number0 1 2 3 4 5 6 7 8 9 1

011

12

13

14

SSC Allocation for S-SCH


Common Pilot Channel (CPICH)

• A total of 512 primary scrambling codes exist

• 64 groups, 8 scrambling code in each group

• Used for cell selection and handovers

Group 0

Group 1Group 2

SC 0

SC 1

SC 8

SC 9

SC 16

SC 17

SC 2

SC 7

Group 0

Code 0

Code

Code 7

Group 63

Code 0

Code

Code 7


Common Pilot Channel (CPICH)


Effect of MHA

• Coverage Improvement Alternatives

Mast head amplifier

• Basic solution for optimized uplink performance

• Compensates feeder cable loss


Effect of MHA

• Coverage Improvement Alternatives


Dividing a Network into Clusters

• 3G network Optimization could be split into …..

(A)Cluster Optimization :

• Mainly concentrates on the detail network optimization for each individual

sub-cluster area.

• Cluster optimization work start when all the sites in the Sub-cluster have been

implemented and integrated into the Network.

• 10-12 cells form one cluster


Dividing a Network into Clusters

(B) Area optimization :

• Takes broader approach by focusing the network

performance over the whole area.

• Will begin after a number of clusters have finished

implemented & optimised ClusterArea


Optimisation of Site Clusters• Identify size and location of clusters

• Define cluster characteristics

• Coverage, interference, handover region size and location

• Neighbour list assessment

• Access, handover and call failures

• Take measurements

• Drive tests

• Ec/Io, pilot pollution, UE TX power, neighbours, call drop rate and handover stats

• Service allocation, FER/BLER, throughput, Max and Av. BER, Delay


Drive Test Process

ClusterPreparation

Data AnalysisData Collection TroubleShooting

Define ClusterDefine Drive Route(major Routes-Airports,Hospitals,Corportate route,Hotspots etc)

Equipment NeededCall PatternsOSS AlarmsNetwork Stats

KPI DefinitionsType Breakdown Root Cause


Dividing a Network into Clusters• Drive testing should be performed on radial and circumferential routes

• Radial routes show variationin signal quality with distancefrom base station

• Circumferential routes provide predictions for signal quality in different directions from the base station

• Typically, three routes should be defined per

cluster: consistency is vital


Equipment: What do you Need to Measure?

• Handset Terminal Measurements

• RRC, Layer 3 Messages

• CPICH Ec/No & CPICH RSCP

• UMTS Active State & Neighbour Set

• UE State

• RLC Throughput

• BLER


Field Measurement tool

• Scanner could be used for coverage and Scrambling code analysis(PCTL/RN/JDSU).

• Logging tools are available from many manufacturers(ASCOM/NEMO/Dingli

swissqual..etc)


Dominance Verification


RSCP Verification


Ec/No Verification


Pilot Pollution Verification-example


Throughput Verification


Drive Tests: Effect of Loading on Ec/Io

• Ec/Io can vary by 7 dB with loading conditions

• It is vital that conditions at the time of measuring are known (you will not get Ec/Io>-10 dB on a heavily loaded network)

• For pre-launch optimisation it is common to assume the network is quiet

• But, if someone else is doing a load test while the drive test is taking place…….

Drive test

Load test


Drive Test Analysis – Call Patterns

• Enough call samples have to be made to make the measurement statistically valid

• In a 50 call sample, one dropped call will cause a change in performance of -2%

• In a 500 call sample, one dropped call will cause a change in performance of -0.2%

• Call length should be defined at the beginning

• We can use different call testing patterns for different optimisation techniques

• Short Calls (for Calls setup performance and delay)

• Long calls (for Drop call performance and SHO performance)


Rake Receiver• Rake fingers delays tuned based on channel impluse response estimation

with the help of different fingers & attributes.(Code matched filter ,search finger, phase rotator ..etc.)


Rake Receiver• Work on MRC(maximul ratio combining)


Rake Receiver• Micro Diversity


Rake Receiver• Macro Diversity in RNC


Thank You

[email protected]

raaj_skype07

mailto:[email protected]

o046 - umts pre-launch optimisation_26 & 27 march_ncell

Documents

aircom international

aircom international

aircom international

aircom international

aircom international

open interface

cniurthe interface

interfacethe iu interface