BTD090208 Drive Test Course

7/30/2019 BTD090208 Drive Test Course

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Mohamed Bakry

Issue:BTD090208

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Confidential Information of Brilliance Tech.

No Spreading without Permission.

The main purpose for site integration drive test is to:

check the site coverage, site performance, neighbor relation, frequency

interference, and the quality of service for this site after getting it on air.

Egypt Map

Security Level: Internal www.brilliancetech.net


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Security Level: Internal www.brilliancetech.netConfidential Information of Brilliance Tech.No Spreading without Permission.

Drive Test data is quite important for estimating the system performance and

helping to trouble shooting. Therefore, analyzing drive test data is an essentialskill for RNP engineers.


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Single Site Verification (Indoor an Outdoor)

Cluster Test Benchmark

Night Action Plans (Migration, Changing parameters or special action)

Special Problem (No Limitation)



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Frequency Plan for 2G and Engineering Parameters for 3G

Configuration Map Updated Cell File

Route

RF Neighbors

Software:TEMS or Genex Probe or any test SW

Hardware: Mobile TEMS, GPS, Portable PC

Test Problem Sheet

(1)



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Definition File (Cell File)

Without it, it is impossible to observe Overshooting neighbors

Neighbor list with

definition file

Neighbor list without

definition file



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Interface and

Functions



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BSIC Undecoded in Other Site No Handover

Delay Handover

Ping Pong Handover

Negative Handover

Overshooting High Overlapping

No Dominant Server

Poor Coverage Interference

Handover Failure

Handover Loss

Drop Call

Sudden Power Drop MS Power Rapid Increase

Below lists common problems which can be observed from Drive Test Log.



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Description:

BSICs cant be decoded in 5s Usually consider 3 strongest neighbors

Reason:

GCLK shift, only decode same site BSICs

Channel interference



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Description:

Neighbor BSIC is decoded and COMMON handover requirement isfulfilled but there is never a handover

Reason:

Missing neighbor.

Interference (Co or Adj-Channel Interference).

Serving cell overshoots covers too far away.

Optimization Parameters Issue (Optimization Team Responsibility).



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Description:

Neighbor BSIC is decoded but handover occurs in much later time

Reason:

All possible neighbors suffer blocking

Optimization Parameters Issue (Optimization Team Responsibility)



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Description:

Lot of handovers between cells

Reason:

Hardware fault

UL/DL interference

Different coverage footprint for antennas of a cell



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Description:

Serving cell hands over to a weaker neighbor

Reason:

Optimization Parameters Issue (Optimization Team Responsibility).



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-59dBm

before

HO

-66dBm

after

HO



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Description:

Cell shoots at far distance but that location has closer cells around

Reason:

Overshooting cell has small down tilt, 0 degree!

Overshooting cell has too high altitude

Closer cells have overshooting as well

BSIC of closer cells cant be decoded



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Overshooting cell (30663) volunteered to serve the MS.

Serving Cell

MS



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Description:

Cells have major RxLevel difference within 5dB

Reason:

Overshooting

Too many cells in that area

Poor antenna down tilt



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Over Lapping Area

-65dBm

-65dBm

-65dBm

-65dBm



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Description:

RxLevel of best neighbors are close to that of serving cell

Reason:

Poor antenna down tilt

Lack of near-by site



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Description:

Low RxLevel with RxQuality

Reason:

Lack of cell site

BSIC of dominant server cant be decoded

Dominant server has blocking or cell-bar

Handover problem. E.g. missing & incorrect neighbor, negativehandover, no & delay handover



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Description:

Coverage area of the cell is incoherent to the antenna direction

Reason:

Wrong cable connection to antennas (Cross Feeder)

ARFCN in the cell file is swapped

Wrong azimuth in the sectors



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Cell ID: 30661BCCH: 984

Cell ID:30663

BCCH: 982

Cell ID:30662

BCCH: 977



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Description:

High RxLevel with RxQuality

Reason:

Co or Adjacent Channel Interference.



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Interference

Co-ChannelInterference

Adjacent ChannelInterference

RF carriers of the same

frequency are transmitting

in close proximity to each other.

the transmission from one RF

Carrier interferes with the other

RF carrier.

An RF source of a nearby

frequency interferes with the

RF carrier.

Example:F = x

F(Co) = x

F(Adj)= x+1

(Or) x-1

Both Co & Adjacent channel interference make degradation in

the cellular network performance.



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Description:

MS fails to reach Target Cell, so return to Source Cell

Reason:

Channel interference (Co or Adjacent)

Poor coverage



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Description:

MS fails to reach target cell, but cant return to source cell

Reason:

Channel interference

Poor coverage



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R l t d I


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Related Issues

Handover (HO)

Power Control

Discontinuous Transmission (DTX)

Concentric Cells


HO (H d )


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As the Ms subscribers are in motion so MSs

tend to go from either poor Coverage or

poor Quality area to another better one,So hand over has to be occurred to save both

the network performance & customer

Satisfaction.

Causes of HO:

1- RF level signal strength.2- TA (Time advance) [MS distance].3- Quality.

Serving

Cell

NeighborCell

which neighbor cell to hand

the MS over to?

the MS performsmeasurements of its

surrounding neighbor cells

and reports its findings to

the network.

HO (Handover)



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Saves radio battery power at the MS.

- Helps to reduce co-channel and adjacent channel interference.

The BTS will

Adjust the TX

Power of Each MS

to ensure that

The Rx signal at

the BTS is

Maintained within

The defined power

Window.


Di ti T i i (DTX)


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Voice Call

Speech Silence

Voice Activity Detection (VAD)

Saves radio battery power

at the MS (where the MS

Doesn't transmit unnecessaryMessage data).

Discontinuous Transmission (DTX)


C t i C ll


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Concentric Cells

The Concentric cell feature has been recently introduced as a solution for radio

networks with high demands in traffic capacity under distinct bandwidth restrictions.

The idea is to split the cell area of a normal cell into an inner Zone (Overlaid) and anouter zone (underlaid) by operating a certain number of carriers (inner zone carriers)

at a lower transmission power . MS situated in the outer zone communicate on the

outer carriers. The mobiles which are closer to the base station preferably

communicate on the inner carriers but they can use the outer carriers if needed. A

handover algorithm is introduced to handle the

Underlaid

Overlaid

O to U

U to O


Si l Sit V ifi ti


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Single Site Verification

Techniques and Technical Description

For 2G and 3G


New Site


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Coverage

QualityCapacity

Customer ComplainsNo Signal

Poor Voice Quality

Network Busy

New Site



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Drive Test

VSWR

HO

Blocking

Coverage

Quality

Neighbors



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1- Call Attempt

Call EstablishedCall blocking

Call blocking100%

The site is not

defined in the

MSC.

Call blockingBut not 100%

Congestion Interference Wrong Mechanical

Or Electrical

antenna tilting.



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2- Call Established

Yes NO

Continue Testing Continue troubleshoot

the site



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3- Checking defined neighbors.

Nothing definedRight installed

The optimizer should defined the neighbors



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No neighbors are defined to the serving site



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4- Checking the azimuth of each antenna

NORight installed

BSS team

should adjust

the azimuth of

the antenna.



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S1

S2 actual

S2 supposed

S3



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5- Make sure that, the site coordinates is right

NOYES

Get the actual site

Coordinates using

GPS.



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Wrong

Coordinates

RightCoordinates



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6- Measuring output power value

Not acceptedAccepted value

VSWR

Wrong Configuration

Crossing between GSM & DCS feeders



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7- HO is allowed

Not allowed

(HO failure)

Allowed

Faulty of the BTS

Neighbors are not

Defined or defined

in a wrong Way.

Due to traffic

congestion.

Co or Adj-Channel

Interference.



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8- Drop calls

YESNO

Poor Rx Level Poor Rx Quality Cross Feeders or missingneighbors or

Overshooting problem

Poor Coverage Blocking

Interference Issue Very Poor RX Level



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9- HO parameters

Negative HO Delayed HOSmooth

Fixing the HO parameters with the optimizer

Ping Pong HO



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10- Cross feeders

YESNO

Production team

should repair this

Cross feeders

problem.



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11- Interference

YESNO

Co-channelinterference

Adjacent-channelinterference



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Cell (32297) was intensively interfering serving cell (33358)

Suggestion: Change frequency of (32297) and/or (33358).



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The Adj-Channel Interference

from CI 30351 caused the

dropped call on CI 31021

Recommendation:

1- Modify the frequency 983 on

CI 30351.

2- Or Down tilt 30351.

Dropped call

position

Adj-Interferer Cell



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12- site Coverage

Poor CoverageOvershootingAs the site objective



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The dropped call cell was 30663 due to that overshooting cell (30663) volunteered to

serve the MS.



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The dropped call cell was 31077

Suggestion:Delete (31078) from the Neighbor L ist of (30287) [but leave the opposite unidirectional relation].

Add (32807/32802) to the Neighbor L ist of (30287).



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The dropped call cell was 33977.

Suggestion:No Action required.



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KPI Introduction



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KPI (KEY PERFORMANCE INDICATORS)

Indicates overall performance of network over a period of time

Good way to monitor network trends and anticipate future problems

Data obtained from drive test and traffic statistics



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2- Call Setup Success Rate (CSSR) = Number of success calls / Number

of attempt calls

1- Call Drop Rate (CDR) = Number of Dropped Calls / Number of

established calls

3- Handover Success Rate (HOSR) = Number of success HO / Number of

attempt HO



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BTD090208 Drive Test Course

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Transcript of BTD090208 Drive Test Course