3g Optimization 1

3G RF Optimisation Basics Robert Joyce

January 2005 AIRCOM International 2005

WCDMA Basics ▪ Frequency Reuse ▪ Scrambling Codes ▪ Signal Strength/Quality Measurements in WCDMA ▪ Soft/Softer Handover ▪ Pilot Pollution ▪ Missing Neighbours

January 2005 AIRCOM International 2005

UK 3G Spectrum Allocations Licence A B C D E

FDD Uplink Operator From (MHz) To (MHz) Hutchison 3G 1920.0 1934.9 Vodafone 1944.9 1959.7 O2 1934.9 1944.9 T-Mobile 1959.7 1969.7 Orange 1969.7 1979.7

TDD

1910 1920 1905 1915

FDD Downlink TDD From (MHz) To (MHz) From (MHz) To (MHz) 2110.3 2124.9 1914.9 1920.0 2134.9 2149.7 N/A N/A 2124.9 2134.9 1909.9 1914.9 2149.7 2159.7 1899.9 1904.9 2159.7 2169.7 1904.9 1909.9

FDD Uplink

1935

1945

1960

Total (MHz) 2x15 + 5 = 35 2x14.8 = 29.6 2x10 + 5 = 25 2x10 + 5 = 25 2x10 + 5 = 25

FDD Downlink

1970 19802110

2125

2135

2150

Licence A - Hutchison 3G

Licence D - T-Mobile

Licence B - Vodafone

Licence E - Orange

2160

Licence C - O2 January 2005 AIRCOM International 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 network

will have a frequency reuse of 1

FDD Uplink

Frequency UARFCN (MHz) F1 9638 1927.6 F2 F3

FDD Downlink F1 F2 F3

10588

2117.6

January 2005 AIRCOM International 2005

Scrambling Codes & CPICH CPICH

▪ The Common Pilot Indication Channel (CPICH) is broadcast from

every 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 measurements

for network acquisition and handover purposes (Ec, Ec/Io). January 2005 AIRCOM International 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 CPICH

measurements ▪ 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 AIRCOM International 2005

Total Received Power Io

Io

▪ In a WCDMA network the User Equipment (UE) may receive signals

from many cells whether in handover or not ▪ Io* = The sum total of all of these signals + any background noise (dBm) ▪

*Note: Sometimes Io is referred to as No, RSSI or ISSI January 2005 AIRCOM International 2005

Received Power of a CPICH Ec

Ec1

Ec2

▪ Using the properties of SCs the UE is able to extract the respective

CPICH levels from the sites received ▪ Ec* = The Received Power of a Particular CPICH (dBm) ▪

*Note: Sometimes Ec is referred to as RSCP January 2005 AIRCOM International 2005

The CPICH Quality (Ec/Io)

Ec1

Ec2

▪ From the previous two measures we can calculate a signal quality for

each CPICH (SC) received ▪ Ec/Io = Ec - Io (dB) ▪

*Note: Sometimes Ec/Io is referred to as Ec/No January 2005 AIRCOM International 2005

Example

Ec/Io1=-5dB

Ec/Io2 =-10dB

Io=-80dBm ▪ From the above three measurements we can calculate for each pilot the Ec level for that particular pilot ▪ Ec1 = -80 - 5 = -85dBm ▪ Ec2 = -80 - 10 = -90dBm

January 2005 AIRCOM International 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 AIRCOM International 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 AIRCOM International 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 AIRCOM International 2005

Handovers in WCDMA - Softer HO ▪ Softer handover occurs between sectors of the same site

January 2005 AIRCOM International 2005

Handovers in WCDMA - Soft HO ▪ Soft handover occurs between sectors of the different sites

▪ For both softer and soft it is the Ec/Io levels used to determine whether

a cell should be added or removed from the active set

January 2005 AIRCOM International 2005

Handovers - Inter frequency HO ▪ Inter frequency handover occurs between two WCDMA carriers ▪ Will be used once operator deploys its second carrier, for microcell

layer or capacity purposes

January 2005 AIRCOM International 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 AIRCOM International 2005

Optimisation Basics ▪ Coverage Optimisation ▪ Neighbour Optimisation ▪ Pilot Pollution Optimisation ▪ SHO Optimisation

January 2005 AIRCOM International 2005

Coverage Optimisation ▪ 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 targets

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

January 2005 AIRCOM International 2005

Coverage Optimisation ▪ Given below are example target drive survey Ec levels for the

different 3G services Service 12.2k Speech 64k CSD 64k PSD 64k CSD Videophone 144k CSD 144k PSD 384k CSD 384k PSD

Dense Urban Deep Indoor - 95% -71.0 -72.0 -73.0 -71.0 -69.0 -70.0 -65.0 -66.0

Urban/Suburban Deep Indoor - 95% -81.0 -82.0 -82.0 -80.0 -79.0 -79.0 -75.0 -76.0

Environment Rail Indoor Window - 95% -88.0 -90.0 -90.0 -88.0 -86.0 -87.0 -84.0 -84.0

Road Indoor Window - 95% -95.0 -96.0 -97.0 -94.0 -93.0 -94.0 -90.0 -90.0

Rural Outdoor - 90% -102.0 -103.0 -103.0 -101.0 -100.0 -100.0 -95.0 -96.0

Indoor 95% -102.0 -102.0 -103.0 -101.0 -99.0 -100.0 -95.0 -96.0

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

vehicle ▪ 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 January 2005 AIRCOM International 2005

Neighbour Optimisation ▪ 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, ideally

with neighbours ranked in order of importance ▪ In 3G the UE must be on the best cell at all times … otherwise it will

drop the call – this is not the case in 2G ▪ 3G/2G neighbour lists must also be comprehensive, incorrect 3G/2G

neighbour lists will lead to dropped calls when moving from 3G to 2G and poor 3G re-selection performance when on 2G

January 2005 AIRCOM International 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 in the active set.

EcNoMISSING_ N ≥ EcNoBEST − M arginMISSING_ N ▪ 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

January 2005 AIRCOM International 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 drive survey.

January 2005 AIRCOM International 2005

Pilot Pollution Optimisation ▪ 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 pilot

pollution (bad Ec/Io). ▪ Whilst 3G voice requires an Ec/Io of above -15dB, 384kbps will

required Ec/Io levels of -9dB or higher !! ▪ Pilot pollution should not be confused with poor coverage, where there

is poor coverage, there is generally pilot pollution/bad Ec/Io

January 2005 AIRCOM International 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 a challenge, for 384 might be an unrealistic target. ▪ Comparison of required EcIo: Service Min EcIo

Voice

PS64 -15

PS128 -13

PS384 -13 -9.5

▪ Even with good Ec levels, some areas will never provide reliable

PS384 simply due to cell overlaps. It seems unclear whether a mature network may ever provide a full 384 footprint. Conclusion: 384 requires an optimised network

January 2005 AIRCOM International 2005

Required EcIo

GPRS Attach Success Rate vs Serving CPICH Ec/Io 120% 100% 80% 60% GPRS Attach Success Rate

40% 20%

-19 -18 -17 -16 -15 -14 -13 -12 -11 -10

-9

-8

-7

0% -6 -5 -20%

Serving Cell CPICH Ec/Io (dB)

January 2005 AIRCOM International 2005

PS384 - required EcIo

DL Application Throughput vs. Serving Cell CPICH Ec/Io DL Application Throughput (kbps)

300

-14

250 200 Mean DL Application Throughput

150

Mode DL Application Throughput DL Application Throughput (Last Value)

100 50 0 -12

-10

-8

-6

-4

-2

0

Serving Cell CPICH Ec/Io (dB)

January 2005 AIRCOM International 2005

Pilot Pollution Optimisation ▪ To avoid confusing areas of poor coverage with areas of pilot pollution

we can define an area of pilot pollution as somewhere where Best server CPICH_Ec >= Ec target (dBm) And Best server CPICH EcNo < Ec/Io target (dB)

▪ 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 locations

on a map

January 2005 AIRCOM International 2005

Pilot Pollution Optimisation ▪ There are various means of reducing pilot pollution ▪ New Sites: Additional sites may reduce pilot pollution by bringing

dominance to an area (before optimising for pilot pollution, always check 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 worst

interferers, pilot pollution can be removed ▪ Solution: 3G Scanner Survey, Analysis, Downtilts, New Sites?

January 2005 AIRCOM International 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 occurs

in the network and where this HO occurs. ▪ For 3G/3G HO, Actix is able to display areas where Softer & Soft HO is

occurring 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 and

azimuth changes ▪ Solution: 3G Scanner Survey, Analysis, Downtilt and Azimuth

changes

January 2005 AIRCOM International 2005

Optimisation Basics ▪ Coverage Optimisation ▪ Neighbour Optimisation ▪ Pilot Pollution Optimisation ▪ 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 AIRCOM International 2005

Overview of Vodafone New Zealand Optimisation Process

January 2005 AIRCOM International 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 AIRCOM International 2005

Overview of Vodafone NZ’s 3G Optimisation Process A

▪ Based upon the 3G

1 hour prior to every cluster Drive test 3G Opt eng must obtain CDF dump from OSS eng

Optimisation Process flowcharts agreed between Aircom/Nokia and Vodafone New Zealand

CDF file obtainable ?

A.1

CDF = Cell Definition File

No

Can drive test proceed ?

A.2

Check with Nokia Opt manager

Yes

A.3

Yes

3G Opt eng obtains Alarm A.4 report and cell availability report from OSS eng

Yes Check with Nokia Opt manager

High number A.5 of alarm ? No

Can drive test proceed ?

Yes

A.6

High cell availability ?

No

Yes Drive test starts

No

Check with Nokia Opt manager

A.7

Yes A.8

Can drive test start ? No

Optimization Stage 1 A.10 (Optimize RF condition)

No

Can OMC solve the problem < 4 hours?

A.9

A.11

Can OMC solve the problem < 4 hours?

B

A.12

No

Yes Yes OMC works on solving the alarm

A.13

No Stage 1 A.14 completed?

A

OMC works on Increasing cell availability

Yes Is the problem A.16 solved ?

Yes

A.15

Optimization Stage 2 A.17 (Optimize Neighbour list) Yes

C

No

Is the problem A.18 solved ? No

No Stage 2 A.20 completed? Postpone the drive test A.19 to next day or until Problem solved

A

Yes

Postpone the drive test A.21 to next day or until Problem solved

Optimization Stage 3 A.22 (Optimize Call Performance)

D

Stage 3 A.23 completed?

No

A

Yes KPI measurement and reporting

January 2005 A.24

AIRCOM International 2005

Overview of Vodafone NZ’s 3G Optimisation Process ▪ Based upon the 3G

Optimisation Process flowcharts agreed between Aircom/Nokia and Vodafone New Zealand ▪ Stage 1 & 2 cover the

basic RF Optimisation steps described earlier

Yes Drive test starts

Optimization Stage 1 A.10 (Optimize RF condition)

B

Stage 1 completed?

No A.14

A

Yes A.17 Optimization Stage 2 (Optimize Neighbour list)

▪ Only once these steps are

completed is it worth moving onto Stage 3 – Call Performance Optimisation

A.8

C

No Stage 2 completed?

A

A.20

Yes A.22 Optimization Stage 3 (Optimize Call Performance)

D

Stage 3 completed?

No A.23

A

Yes KPI measurement

A.24

January 2005 AIRCOM International 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 the

key 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 AIRCOM International 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:

# _ Bins _ 1 _ Cell _ in _ Active_ Set ×1+# _ Bins _ 2 _ Cells_ in _ Active_ Set × 2+# _ Bins _ 3 _ Cells_ in _ Active_ Set × 3 # _ Bins _ 1 _ Cell _ in _ Active_ Set+# _ Bins _ 2 _ Cells_ in _ Active_ Set+# _ Bins _ 3 _ Cells_ in _ Active_ Set January 2005 AIRCOM International 2005

RF Optimisation ▪ Basic RF analysis checking the following

▪ Coverage Optimisation ▪ Neighbour Optimisation ▪ Pilot Pollution Optimisation ▪ SHO Optimisation. ▪ First stage is to run the KPI reports, then follows this with more

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

January 2005 AIRCOM International 2005

Actix RF KPI Report ▪ Run the basic RF KPI report – check the KPIs

January 2005 AIRCOM International 2005

Basic “Sites on air” analysis ▪ For each cell in the cluster check that

coverage is seen for the sites expected to be on air ▪ Check correct SC is radiating in the

expected 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 AIRCOM International 2005

Coverage (Ec) Analysis ▪ If KPI Report indicates good Ec - no further Ec analysis required ! ▪ Otherwise analyse !! ▪ Solution: Tilts, azimuths, new sites

January 2005 AIRCOM International 2005

Neighbour Optimisation ▪ 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 be necessary after downtilts ▪ Actix should be used to generate Missing Neighbour Report from

Scanner data ▪ Remember until the cluster is complete, additional neighbours will

come and go

January 2005 AIRCOM International 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 the SCs seen generating a neighbour list like the one given ▪ The number of missing neighbours found

will be dependent on the quality of the initial neighbour list ▪ Don’t be scared of adding neighbours !!

sc 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 9 9 9

neighbour 9 232 496 344 154 386 10 362 145 114 256 488 360 376 346 50 218 490 66 152 48 378 401 8 362 10

count 165 52 40 34 18 12 11 11 10 8 5 5 4 4 3 1 1 1 1 1 1 1 1 114 37 10 January 2005 AIRCOM International 2005

Pilot Pollution (Ec/Io) Analysis ▪ Run Pilot Pollution query to display areas of pilot pollution on map

January 2005 AIRCOM International 2005

Pilot Pollution (Ec/Io) Analysis ▪ Identify worst “Pilot Polluters” on map ▪ Solution: tilts, azimuths, new site?

January 2005 AIRCOM International 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 distant

sites, is it in important high traffic areas? ▪ Solution: Tilts, Azimuths

January 2005 AIRCOM International 2005

Cell Adjacency Planner - CAP 3G – 2G Adjacencies

January 2005 AIRCOM International 2005

Cell Adjacency Planner - CAP 3G – 3G adjacencies

January 2005 AIRCOM International 2005

3G/3G Neighbour Optimisation (3)

January 2005 AIRCOM International 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 the

above 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 AIRCOM International 2005

Stage 3: Run Call KPIs Report ▪ Run RE Call KPI report ▪ Identify problem areas, Call Setup Success, Call Drop etc.

January 2005 AIRCOM International 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.

January 2005 AIRCOM International 2005

Process Summary ▪ Stage 0 Cluster Preparation - plots, site checks, neighbour checks

etc. ▪ Stage 1&2 RF optimisation, Ec, Ec/Io, Missing Neighbours, SHO

Area ▪ Stage 3 In Call Analysis (Speech, Video, PS, ISHO etc) – will be the

subject of a further training session once Actix Reports in place. ▪ CLUSTER ACCEPTANCE !!

▪ Any questions: [email protected] January 2005 AIRCOM International 2005