3G RF Opt Training-libre

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January 2005

AIRCOM International 2005

3G RF Optimisation Basics

Robert Joyce



January 2005


WCDMA Basics

Frequency Reuse

Scrambling Codes

Signal Strength/Quality Measurements in WCDMA

Soft/Softer Handover

Pilot Pollution

Missing Neighbours



January 2005


UK 3G Spectrum Allocations

From (MHz) To (MHz) From (MHz) To (MHz) From (MHz) To (MHz)A Hutchison 3G 1920.0 1934.9 2110.3 2124.9 1914.9 1920.0 2x15 + 5 = 35

B Vodafone 1944.9 1959.7 2134.9 2149.7 N/A N/A 2x14.8 = 29.6

C O2 1934.9 1944.9 2124.9 2134.9 1909.9 1914.9 2x10 + 5 = 25

D T-Mobile 1959.7 1969.7 2149.7 2159.7 1899.9 1904.9 2x10 + 5 = 25

E Orange 1969.7 1979.7 2159.7 2169.7 1904.9 1909.9 2x10 + 5 = 25

Total (MHz)

TDD

Licence Operator

FDD DownlinkFDD Uplink

1905

1910 1960

FDD Uplink

Licence A - Hutchison 3G

Licence B - Vodafone

1935

Licence C - O2

Licence D - T-Mobile

FDD Downlink

21502110

Licence E - Orange

1915

1920 1980 21251945 1970 2135 2160

TDD



January 2005


Frequency Reuse

Initially operators have been launching with just a single carrier

Vodafone NZ Network will initially be FDD only

Vodafone will launch using only the FDD carrier (F1 =10588)

All launch cells will use F1 & therefore Vodafone NZ’s 3G networkwill have a frequency reuse of 1

UARFCNFrequency

(MHz)

FDD Uplink F1 9638 1927.6

F2

F3

FDD Downlink F1 10588 2117.6

F2

F3



January 2005


Scrambling Codes & CPICH

The Common Pilot Indication Channel (CPICH) is broadcast fromevery cell

It carries no information and can be thought of as a “beacon”constantly transmitting the Scrambling Code of the cell

It is this “beacon” that is used by the phone for its cell measurementsfor network acquisition and handover purposes (Ec, Ec/Io).

CPICH



January 2005


3G Coverage Measurements

The majority of 3G coverage measurements are based upon

measurements of the CPICH Golden Rule: If the UE can’t see the CPICH the UE can’t see the

cell.

Initial 3G network optimisation will be performed purely from CPICHmeasurements

Three key related measurements for 3G optimisation are

Ec - The Received Signal Level of a particular CPICH (dBm)

Io - The Total Received Power (dBm)

Ec/Io - The CPICH Quality (The ratio of the above two values)



January 2005


Total Received Power I o

In a WCDMA network the User Equipment (UE) may receive signalsfrom many cells whether in handover or not

I o * = The sum total of all of these signals + any background noise (dBm)

*Note: Sometimes Io is referred to as No, RSSI or ISSI

I o



January 2005


Received Power of a CPICH E c

Using the properties of SCs the UE is able to extract the respectiveCPICH levels from the sites received

E c * = The Received Power of a Particular CPICH (dBm)

*Note: Sometimes Ec is referred to as RSCP

E c1 E c2



January 2005


The CPICH Quality (Ec/Io)

From the previous two measures we can calculate a signal quality foreach CPICH (SC) received

Ec/Io = Ec - Io (dB)

*Note: Sometimes Ec/Io is referred to as Ec/No

E c1 E c2



January 2005


Example

From the above three measurements we can calculate for each pilotthe Ec level for that particular pilot

Ec1 = -80 - 5 = -85dBm

Ec2 = -80 - 10 = -90dBm

E c /I o1=-5dB E c /I o2 =-10dB

Io=-80dBm



January 2005


Ec, Io and Ec/Io Measurement

All commercial scanners and test UEs are capable of making Ec, Io and

Ec/Io measurements It is these measurements that are used for cover analysis and basic

optimisation



January 2005


3G Scanners

Many types of 3G scanners on the market

Agilent’s 3G Scanner & Nitros Software

Anritsu’s ML8720B 3G scanner

DTI Seagull (Dual band 3G/2G) scanner

From experience the Anritsu scanner is the better of the all three with

a higher sampling rate and greater flexibility However DTI scanner has added benefit of 2G scanning, ideal for 3G-

2G neighbour optimisation as well as 2G optimisation



January 2005


Handovers in WCDMA

Various handover types exist in WCDMA

Those between WCDMA sites (intra-system HO)

Those between WCDMA and GSM (inter-system HO)



January 2005


Handovers in WCDMA - Softer HO

Softer handover occurs between sectors of the same site



January 2005


Soft handover occurs between sectors of the different sites

For both softer and soft it is the Ec/Io levels used to determine whethera cell should be added or removed from the active set

Handovers in WCDMA - Soft HO



January 2005


Handovers - Inter frequency HO

Inter frequency handover occurs between two WCDMA carriers

Will be used once operator deploys its second carrier, for microcelllayer or capacity purposes



January 2005


Handovers - Inter system HO

Inter system handover occurs between 3G and 2G sites

As with all handovers, accurate adjacencies will be required

3G 2G



January 2005


Optimisation Basics

Coverage Optimisation

Neighbour Optimisation

Pilot Pollution Optimisation

SHO Optimisation



January 2005



As with 2G if the coverage is inadequate then the call quality will be

inadequate Therefore this first stage in 3G optimisation is ensuring adequate

coverage

Link budgets should be used to determine both the planning targetsand the drive survey level targets

Note that the planning and drive survey level targets will be different



January 2005



Dense Urban Urban/Suburban Rail Road Rural Indoor

Deep Indoor - 95% Deep Indoor - 95% Indoor Window - 95% Indoor Window - 95% Outdoor - 90% 95%

12.2k Speech -71.0 -81.0 -88.0 -95.0 -102.0 -102.0

64k CSD -72.0 -82.0 -90.0 -96.0 -103.0 -102.0

64k PSD -73.0 -82.0 -90.0 -97.0 -103.0 -103.0

64k CSD Videophone -71.0 -80.0 -88.0 -94.0 -101.0 -101.0

144k CSD -69.0 -79.0 -86.0 -93.0 -100.0 -99.0

144k PSD -70.0 -79.0 -87.0 -94.0 -100.0 -100.0384k CSD -65.0 -75.0 -84.0 -90.0 -95.0 -95.0

384k PSD -66.0 -76.0 -84.0 -90.0 -96.0 -96.0

Service

Environment

These levels are the levels that should be achieved at the roof of thevehicle

If these levels are not achieved then inbuilding coverage will be poor

Further optimisation with lower coverage levels is very difficult

Solutions: Downtilt, Azimuth, New Site

Given below are example target drive survey Ec levels for thedifferent 3G services



January 2005



Missing Neighbours was and still is the biggest cause of poor

performance in most commercial 3G networks The majority of call drops in early cluster are due to missing

neighbours.

It is therefore essential that the initial neighbour list is thorough, ideallywith neighbours ranked in order of importance

In 3G the UE must be on the best cell at all times … otherwise it willdrop the call – this is not the case in 2G

3G/2G neighbour lists must also be comprehensive, incorrect 3G/2Gneighbour lists will lead to dropped calls when moving from 3G to 2Gand poor 3G re-selection performance when on 2G



January 2005


3G/3G Neighbour Optimisation

We declare a 3G missing neighbour as a a cell not declared as

neighbour of the best active cell although it is eligible to be added inthe active set.

A practical margin of 5dB is recommended as an initial window …anything bigger and the neighbour lists become too large

Solution: 3G Scanner Survey, Actix Analysis, Neighbours Added

N MISSING BEST N MISSING in M EcNo EcNo __ arg−≥



January 2005


2G/3G Neighbour Optimisation

2G/3G neighbour optimisation will require the use of both 3G and 2G

drive survey equipment Dualband scanner files can quickly be processed to pair up the best

3G cells with the best 2G cells for every sample along the drivesurvey.



January 2005



As more and more 3G sites are integrated, the pilot pollution within the

network will increase With >4 pilots of a similar level it can be very difficult to establish even

a voice call

The higher the data rate the more susceptible the service is to pilotpollution (bad Ec/Io).

Whilst 3G voice requires an Ec/Io of above -15dB, 384kbps willrequired Ec/Io levels of -9dB or higher !!

Pilot pollution should not be confused with poor coverage, where thereis poor coverage, there is generally pilot pollution/bad Ec/Io



January 2005


PS384 - Pilot Pollution Areas

DL_PS384 is much more sensitive to pilot pollution or overlaps than

lower bit-rates. Optimising pilot pollution for PS128 is already achallenge, for 384 might be an unrealistic target.

Comparison of required EcIo:

Service Voice PS64 PS128 PS384

Min EcIo -15 -13 -13 -9.5

Even with good Ec levels, some areas will never provide reliablePS384 simply due to cell overlaps. It seems unclear whether a maturenetwork may ever provide a full 384 footprint.

Conclusion: 384 requires an optimised network



January 2005


Required EcIo

GPRS Attach Success Rate vs Serving CPICH Ec/Io

-20%

0%

20%

40%

60%

80%

100%

120%

-19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5

Serving Cell CPICH Ec/Io (dB)

GPRS Attach Success Rate



January 2005


PS384 - required EcIo

DL Application Throughput vs. Serving Cell CPICH Ec/Io

0

50

100

150

200

250

300

-14 -12 -10 -8 -6 -4 -2 0

Serving Cell CPICH Ec/Io (dB) D L

A p p l i c

a t i o n T h r o u g h p u

t ( k b p s )

Mean DL Application Throughput

Mode DL Application Throughput

DL Application Throughput (Last Value)



January 2005



To avoid confusing areas of poor coverage with areas of pilot pollution

we can define an area of pilot pollution as somewhere where

The Ec target is the target coverage = -100dBm

The current recommended Ec/Io target = -10dB

Actix is able to identify areas of pilot pollution and display the locationson a map

Best server CPICH_Ec >= Ec target (dBm)

And

Best server CPICH EcNo < Ec/Io target (dB)



January 2005



There are various means of reducing pilot pollution

New Sites: Additional sites may reduce pilot pollution by bringingdominance to an area (before optimising for pilot pollution, alwayscheck that a new site is not about to be brought on air in the locality)

Antenna Downtilts: By adjusting tilts on the best servers, or worstinterferers, pilot pollution can be removed

Solution: 3G Scanner Survey, Analysis, Downtilts, New Sites?



January 2005


Handover Optimisation

Softer, Soft, Inter-frequency & system HOs have all been optimised on

Nokia’s trial and other customers networks Therefore initial HO Optimisation should not require any changes to the

UTRAN parameters ….

Instead initial HO optimisation will involve studying how much HO occursin the network and where this HO occurs.

For 3G/3G HO, Actix is able to display areas where Softer & Soft HO isoccurring and calculate the percentage of a drive route in SHO

Typically we should be aiming for a SHO area of less that 40%

Optimisation of SHO area should be performed using downtilt andazimuth changes

Solution: 3G Scanner Survey, Analysis, Downtilt and Azimuthchanges



January 2005


Optimisation Basics




SHO Optimisation

Everything is based around Ec/Io, to improve this we need to

Increase Ec (improve the best server(s))

Reduce Io (reduce pilots not eligible for the active set)

Get all neighbours optimised In call drive runs should only take place once Radio Optimisation is

complete



January 2005


Overview of Vodafone New ZealandOptimisation Process



January 2005


OrangeUK 3G Optimisation Process

This section will cover the following;

Overview of Vodafone New Zealand 3G Optimisation Process

Key Performance Indicators

Analysis Tools & Processes

Next Steps



January 2005


Overview of Vodafone NZ’s 3G Optimisation Process

Based upon the 3G

Optimisation Processflowcharts agreed betweenAircom/Nokia andVodafone New Zealand

1 hour prior to every clusterDrive test 3G Opt eng must

obtain CDF dump from OSS eng

CDF fileobtainable ?

3G Opt eng obtains Alarmreport and cell availability

report from OSS eng

Yes

No

CDF = Cell Definition File

Yes

Check with NokiaOpt manager

High numberof alarm ?

Can drive testproceed ?

Yes

No

Can drive testproceed ?

Check with NokiaOpt manager

Yes

High cellavailability ?

NoCheck with NokiaOpt manager

Yes Yes Can drive teststart ?

Can OMC solvethe problem < 4

hours?

Yes

OMC works onsolving the alarm

Is the problemsolved ?

No

Optimization Stage 1(Optimize RF condition)

Optimization Stage 2(Optimize Neighbour list)

Optimization Stage 3(Optimize Call Performance)

Postpone the drive testto next day or until

Problem solved

Can OMC solvethe problem < 4

hours?

Yes

OMC works onIncreasing cell

availability

Is the problemsolved ?

No

Stage 1completed?

Stage 2completed?

Stage 3completed?

KPI measurementand reporting

Postpone the drive testto next day or until

Problem solved

No

No

No

Yes

Yes

Yes

No

No

NoNo

Yes

Yes

A

A

A

A

D

C

B

Drive test starts

A.1

A.3A.2

A.4

A.5

A.6 A.7

A.8 A.9

A.10

A.11

A.12

A.13A.14

A.15

A.16A.17

A.19

A.21

A.22

A.20

A.23

A.24

A.18



January 2005


Overview of Vodafone NZ’s 3G Optimisation Process

Based upon the 3G

Optimisation Processflowcharts agreed betweenAircom/Nokia andVodafone New Zealand

Stage 1 & 2 cover thebasic RF Optimisationsteps described earlier

Only once these steps arecompleted is it worthmoving onto Stage 3 – CallPerformance Optimisation

Yes

Optimization Stage 1(Optimize RF condition)

Optimization Stage 2(Optimize Neighbour list)

Optimization Stage 3

(Optimize Call Performance)

Stage 1

completed?

Stage 2

completed?

Stage 3

completed?

KPI measurement

No

No

No

Yes

Yes

Yes

A

A

A

D

C

B

Drive test starts A.8

A.10

A.14

A.17

A.22

A.20

A.23

A.24



January 2005


Key Performance Indicators (KPI)

In order to benchmark the performance of a 3G network a basic set of

KPI targets are required The Vodafone NZ 3G KPI targets fall into two categories, RF KPIs and

in-call KPIs

The Vodafone RF KPIs are very simple and concise but focus on thekey RF requirements of Ec (RSCP), Ec/Io and SHO area

The In Call or End To End (E2E) KPIs are somewhat more complex



January 2005


Vodafone RF KPIs

The RF targets are defined in terms of: -

RSCP of the Common Pilot Channel

-89 dBm in >= 95% of bins for dense urban -94 dBm >= 95% of bins for urban

-99 dBm >= 95% of bins for suburban

-104 dBm >= 90% of bins for rural

Ec/Io of Common Pilot Channel in unloaded network

Ec/Io >= –10 dB in >= 95% of bins for DU, U, SU

Ec/Io >= –10 dB in >= 90% of bins for Rural

Ec/Io of Common Pilot Channel in loaded network

Ec/Io >= –14 dB in >= 95% of bins for DU, U, SU

Ec/Io >= –14 dB in >= 90% of bins for Rural

Test case to be agreed

SHO Overhead: 30-40%

This Kpi will be measured according to the formula below:

Set ActiveinCells BinsSet ActiveinCells BinsSet ActiveinCell Bins

Set ActiveinCells BinsSet ActiveinCells BinsSet ActiveinCell Bins

____3__#____2__#____1__#

3____3__#2____2__#1____1__#

++

×+×+×



January 2005


RF Optimisation

Basic RF analysis checking the following



Pilot Pollution Optimisation SHO Optimisation.

First stage is to run the KPI reports, then follows this with moredetailed analysis.

If the route meets the RF KPIs there’s no point doing further analysis



January 2005


Actix RF KPI Report

Run the basic RF KPI report – check the KPIs



January 2005


Basic “Sites on air” analysis

For each cell in the cluster check that

coverage is seen for the sites expected tobe on air

Check correct SC is radiating in theexpected direction (crossed feeders?)

Highlight those sites not seen on air and

any suspected crossed feeders But make sure your cell refs data is

accurate !!!



January 2005


Coverage (Ec) Analysis

If KPI Report indicates good Ec - no further Ec analysis required !

Otherwise analyse !!

Solution: Tilts, azimuths, new sites



January 2005



If downtilts are to be made to any sectors, then additional neighbours

should not be added to/or for these cells as they may not benecessary after downtilts

Actix should be used to generate Missing Neighbour Report fromScanner data

Remember until the cluster is complete, additional neighbours will

come and go



January 2005


3G/3G Neighbour Optimisation (2)

3G Neighbour lists can be generated

automatically by the Actix The tool runs through every point in the

survey comparing the Ec/Io values of theSCs seen generating a neighbour list likethe one given

The number of missing neighbours foundwill be dependent on the quality of the initialneighbour list

Don’t be scared of adding neighbours !!

sc neighbour count

8 9 165

8 232 528 496 40

8 344 34

8 154 18

8 386 12

8 10 11

8 362 11

8 145 10

8 114 8

8 256 58 488 5

8 360 4

8 376 4

8 346 3

8 50 1

8 218 1

8 490 1

8 66 18 152 1

8 48 1

8 378 1

8 401 1

9 8 114

9 362 37

9 10 10



January 2005


Pilot Pollution (Ec/Io) Analysis

Run Pilot Pollution query to display areas of pilot pollution on map



January 2005


Pilot Pollution (Ec/Io) Analysis

Identify worst “Pilot Polluters” on map

Solution: tilts, azimuths, new site?



January 2005


SHO Analysis

KPI report will indicate % of route in SHO

Aim for SHO < 40%

Run RE SHO query to display areas on a map - is this due to distantsites, is it in important high traffic areas?

Solution: Tilts, Azimuths

Cell Adjacency Planner CAP



January 2005


Cell Adjacency Planner - CAP

3G – 2G Adjacencies

Cell Adjacency Planner CAP



January 2005


Cell Adjacency Planner - CAP

3G – 3G adjacencies



January 2005


3G/3G Neighbour Optimisation (3)



January 2005


Stage 3: In Call Optimisation

Only once the RF Optimisation is complete should In Call analysis be

undertaken In call analysis will also pick up

Coverage Problems

Pilot Pollution Problems

Missing Neighbours

SHO problems

However if the RF Optimisation has been done correctly, none of theabove should be seen at Stage 3 !

In Call Optimisation will be similar to RF Optimisation

Run In Call KPI report Analyse any problems seen



January 2005


Stage 3: Run Call KPIs Report

Run RE Call KPI report

Identify problem areas, Call Setup Success, Call Drop etc.



January 2005


Stage 3: Detailed In call analysis

Detailed in call analysis

Look for the basics first, Ec, Ec/Io, missing neighbours etc.

Only then delve into the detailed L3 message flows.



J 2005

Process Summary

Stage 0 Cluster Preparation - plots, site checks, neighbour checks

etc.

Stage 1&2 RF optimisation, Ec, Ec/Io, Missing Neighbours, SHOArea

Stage 3 In Call Analysis (Speech, Video, PS, ISHO etc) – will be thesubject of a further training session once Actix Reports in place.

CLUSTER ACCEPTANCE !!

Any questions: [email protected]

Documents

3G RF Opt Training-libre