3G Drive Test

3G Drive Test Introduction

Radio Network Initial Tuning for WCDMA

Preparations Parameter Audit

Commercial Launch

Drive Testing & Post

Processing

Change Verification & Reporting

Analysis & Change

Proposals

Drive Test Steps

Tools For Drive Test and Analysis

TEMS Investigation, Nemo, Probe for WCDMA (Software)

Scanner (Software + HW) External GPS User Equipment (UE) MCOM3g/Mapinfo/Actix MS Access/Excel based tools

Serving/Active Set + Neighbors

Layer 3 MessagesLayer 3 Messages are the messages on the Uu interface i.e between Mobile station and the Node B.

Radio Parameters

WCDMA HSPA/GSM Data Line Chart

GSM NeighborsThis window is very helpful in case of 2G – 3G Handovers as we can see all the 2G neighbors of that particular 3G cell in the compressed mode state.

Serving/Active Set + Neighbors Cell I.D – This is the identity or name

given to a particular Node B and its cell by the operator.

UARFCN – It is the frequency band allotted to the operator. One spectrum bandwidth is of 5MHz in WCDMA or 3G.This window shows us the centre frequency of the bandwidth allotted to the operator.

Serving/Active Set + Neighbors Cell Name – It is the name given to

particular Node B’s by the operator generally along the lines of the name of the area the Node B is located in.

Scrambling Code – Scrambling code is a code assigned to a particular cell. There are 512 such codes for the network to differentiate among different Node B’s and these codes can be repetitive. They are of two types primary and secondary.

Serving/Active Set + Neighbors AS – This stands for Active Set. Active Set is

the set of Scrambling Code which the U.E is currently latched on and there can be a maximum of 3 Scrambling codes in Active Set.

MN – MN Stands for monitored neighbor i.e. the neighbor cell that is detected by the U.E as a neighbor and is also defined as a neighbor in the network. U.E will initiate a Handover onto the monitored neighbor in case the monitored neighbor has a stronger RSCP or EcNo than the AS.

Serving/Active Set + Neighbors DN - DN stands for Detected Neighbor and

as the name suggests it is the neighbor detected by the UE but, is not defined in our network . Hence, the U.E does not handover to the detected neighbor. It can be because of Overshooting of a site, incomplete neighbor list or in case of a new site. It is very important to optimize and have no DN’s as they are one of the major reasons of Call drops in 3G.

Radio Parameters

CPICH Ec/No – Common Pilot channel Ec/No is the ratio of energy of the chip and the combined power of all the signals including the pilot itself received by the UE at that particular point. It is a very important factor for call quality.

CPICH RSCP – Received Signal Code Power is the level of the signal received by the U.E from a particular pilot.

Radio Parameters

Radio parameters are the parameters of a Mobile equipment –Tx Power – As the name suggests it is the

transmitting power of a Mobile Station. Its value can vary from

-50 to 50. The minimum the Tx power of the Mobile station the better it is for call quality.

UTRA Carrier RSSI - It is the Received Signal Strength Indicator of the Mobile Station or the U.E. It tells us the total Power Received by the Mobile Station from all the Pilots including itself at that particular location.

Radio Parameters

SIR – It is the signal to interference Ratio is the ratio of Energy in the DPCC(Dedicated Physical Control Channel) to that of the interference and noise received by the U.E.

Target SIR – It is the target Signal to Interference ratio that Mobile Equipment is supposed to achieve by increasing or decreasing its power. It is set by the use of Power Control procedure.

Radio Parameters

SQI - It is the speech Quality Index which is a parameter to rate the voice Quality on that particular call. It ranges from 0 – 30 with 30 being the best quality.

RRC State – It tells the current state and channel as in Idle or dedicated.

Mode – It is the mode that we are using GSM or WCDMA.

HSPA/GSM Line Chart

This window gives us the data speed for both 3G and 2G modes depending on which mode the mobile equipment is.

RLC DL Throughput – This is the total throughput on the downlink at that particular point.

The speed shown in this window as throughput is in Kilobits/sec.

Active Window

Handovers

In UMTS there are the following type of Handovers-Intra Frequency Handovers- Softer Handover – The HO’s that take place

between any sectors of the same node B come under this category.

Soft Handover – The HO’s that take place between different Node Bs running on same frequency are called soft HOs.

Inter Frequency Handover- Hard Handover – The HO’s that take place between

Node Bs running on different frequencies. HOs from 2G-3G fall under this category.

Active Set Update

In 3G there can be 6 pilots in the active set. But, we generally set it at maximum of three(depends on the operator) to avoid Pilot pollution. In case of soft Handover all the cells which are in MN can be entered into Active set but, only till the maximum limit of three. This procedure of soft HO from monitored to Active set is called Active set update.

Active Set Update(Soft HO)

Monitored Neighbor

Current Location

Active Set Update(Soft HO)

Current Location

Added to Active Set

Active Set Update

Pilot Pollution

The Cells with which the UE is communicating form the UE’s Active Set

This Active Set is made typically of 3 cells/pilot signals Any Pilot which is not a member of a UE’s Active Set

and exceeds a certain threshold (typ. Ec/Io>-15dB) is considered a Polluter

Pilot Pollution is a common WCDMA issue that needs to be sorted immediately.

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

Pilot Pollution

There are various means of reducing pilot pollution▪New Sites: Additional sites may reduce pilot pollution by bringing dominance to an area (before optimizing for pilot pollution, always check that a new site is not about to be brought on air in the locality)▪Antenna Down tilts: By adjusting tilts on the best servers, or worst interferers, pilot pollution can be removed.▪Azimuth Change: Azimuth can be adjusted to other direction after discussing with RF Planning Team.▪Reduce Power: Power of overshooting cell ( Pilot Polluter ) can be reduced but it is last step to reduce coverage but in day to day optimization its not much recommended.

Case 1: Drop due to missing neighbor

Problem: Detected Nighbor (DN) UE sends a Measurement Report that contains an

event1a means adding a new RL (cell) to Active Set If the reported cell is not in the current neighbor cell

list and the reported Ec/No is better than the best serving cell Ec/No in AS by some dBs (set by a RNC parameter)

If for any reason the new cell can not be added to AS, call will be released

Case 1: Drop due to missing neighbor

“DN” cell better than the serving cell

DL BLER gets worse

“DN” cell better than the serving cell

DL BLER gets worse

Case 2: Drop due to Poor Coverage (low RSCP)

Problem: Poor DL coverageWhen UE gets to an area with low RSCP ( < -105 dBm)regardless Ec/No values there is high risk for drop.UE will likely ramp up the transmitted power and reach its max power. The DL BLER will probably increase and SIR target cannot maintain anymore, finally the call drops.

Case 2: Drop due to DL Poor Coverage

Very bad RSCP

UE max Tx powerandhigh DL BLER

Very bad RSCP

UE max Tx powerandhigh DL BLER

Drive Test Route with Drop Calls: Cluster 1

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Quality Comparison(Long Call) (Scanner)

EcNo of UE dedicated mode is quite low in many areas, main reasons are missing neighbors and overshooting, all cases are discussed later.

Coverage Comparison(Long Call) (Scanner)

RSCP of UE dedicated mode is quite low in many areas, main reasons are missing. All cases are discussed later.

Best SC Comparison(Long Call) (Scanner)

Scrambling code of UE dedicated mode and Scanner:

Quality Check Comparison(Long Call) (Scanner)

Quality Check of UE dedicated mode and Scanner:

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OvershootingAnalysis

DXB2314-7 (SC -91)Down tilt from 4 degree to 7 degree

DXB2314-8 (SC -92)Down tilt from 4 degree to 7 degree

DXB2309-7Down tilt from 4 degree to 7 degree





DXB2308-7Down tilt from 4 degree to 7 degrees. High Call Drop Cell.

DXB2308-8Down tilt from 4 degree to 7 degree. High Call Drop Cell.





DXB2766-8Down tilt from 4 degree to 6 degree.








Down tilt Recommendations for Overshooting Cells

Cell Name Current E-Tilt Proposed E-TiltDXB23147 4 7DXB23148 4 7DXB23097 4 7DXB23099 4 7DXB28028 4 6DXB28029 4 6DXB23077 4 5DXB23087 4 7DXB23088 4 7DXB27657 4 6

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Cell Name Current E-TiltProposed E-

TiltDXB27658 4 6DXB23078 4 7DXB27667 4 7DXB27668 4 6DXB27669 4 7DXB24207 4 6DXB24208 4 6DXB24209 4 6DXB24257 4 6DXB24258 4 6DXB24259 4 6

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Missing NeighborAnalysis

Missing Neighbors

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SRNC SCELL SPSC NRNC NCELL NPSC1 31263 442 1 31323 5011 31263 442 1 31311 496

231 23147 91 1 31261 440231 23148 92 1 31311 496231 23148 92 1 31102 41231 23148 93 1 31102 41

Missing Neighbors60

SRNC SCELL SPSC NRNC NCELL NPSC231 23088 185 1 48011 11231 23089 186 1 48011 11231 27658 353 1 48011 11231 27657 352 1 48011 11231 27477 27 1 48011 11231 23088 185 231 27657 353231 27657 352 1 48013 13231 23087 184 231 27657 352231 23077 405 231 27477 27231 23077 405 231 23089 186231 23078 404 231 27658 353

Missing Neighbor61

SRNC SCELL SPSC NRNC NCELL NPSC

231 28598 36 1 32342 100

1 31673 306 231 28598 36

1 31591 288 231 28598 36

1 31592 289 231 28598 36

Missing Neighbor

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SRNC SCELL SPSC NRNC NCELL NPSC231 23097 459 1 34071 291231 23099 461 1 34071 291

1 31362 145 231 23099 461231 24207 115 1 40082 476231 24208 116 1 40082 476231 24208 116 1 33341 299231 24207 115 1 33322 260231 24207 115 1 33323 261

Neighbor Addition

SCELL SPSC NCELL NPSC31263 442 31323 50131263 442 31311 49623147 91 31261 44023148 92 31311 49623148 92 31102 4123148 93 31102 4123088 185 48011 1123089 186 48011 1127658 353 48011 1127657 352 48011 1127477 27 48011 1123088 185 27657 35327657 352 48013 1323087 184 27657 35223077 405 27477 2723077 405 23089 18623078 404 27658 353

63 SCELL SPSC NCELL NPSC28598 36 32342 10031673 306 28598 3631591 288 28598 3631592 289 28598 3627668 425 34762 17227668 425 48011 1130152 265 23077 40523097 459 34071 29123099 461 34071 29131362 145 23099 46124207 115 40082 47624208 116 40082 47624208 116 33341 29924207 115 33322 26024207 115 33323 26140081 475 24258 50533351 208 24259 506

Following Neighbors are found missing from Drive Test Analysis :

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Call DropAnalysis

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5 Sec Before Drop Call

5 Sec After Drop Call

Line ChartRSCP(A,N,D)

EcIo (A,N,D)

Best SC

UE TXPO, SIR, BLER

Drop Call#1

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Observations & Recommendations•Call was dropped on Nokia site DXB2061 overshooting from 2.8km and there are missing NHBRs in the vicinity i.e. DXB20617 and DXB 21357.•Also Nokia site DXB2125 is down.DXB23147 needs to be down-tilted from 4 to 6.

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Drop Call#2 (Dropped, Coverage hole)

Observations & Recommendations•This drop happened in Nokia cluster where there are no sites in the vicinity.•It’s a coverage hole and future site DXB2606 will improve the situation.

During Drop CallLine ChartRSCP(A,N,D)

EcIo (A,N,D)

Best SC

UE TXPO, SIR, BLER

RSCP EcIo

Drop Call#4 (Dropped on Nokia, re-Established on Nokia)

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Observations & Recommendations•Missing Neighbor DXB40082 and DXB24257.

RSCP(A,N,D)

EcIo (A,N,D)

Best SC

UE TXPO, SIR, BLER

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Thank You

Engineering

3G Drive Test