analyze coverage issue in dt

8/3/2019 Analyze Coverage Issue in DT

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HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

Security Level:

www.huawei.com

How to analyze Coverage

Issues in DT


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Coverage

Downlink RxLevel and Coverage

Coverage of single cell

Coverage of whole network


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HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 3

Coverage

EIRP(dBm)

L(dB)

RxLev(dBm)

Unexpected coverage(overshooting)Good coverage

Network Coverage is evaluated by:

RxLev = EIRP(dBm) L(dB)

Where:

EIRP = Effective Isotropic Radiated Power

L = Propagation Losses

In urban area, Lower Antenna Height (=6 degree),

and Lower EIRP (


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Coverage(one cell)

The following example shows thedownlink RxLevel(Dedicated Mode)

decreases when MS is driving away

from BTS.

The RxLevel decrease faster when

Antenna Downtilt increase.

Downtilt: 0 drgree

Downtilt: 8 drgree

Variation

due to

shadowing

Global

means

RxLevel

Variations due to

Rayleigh

fading


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Coverage(Network)

The picture shows the coverage of a city, which contains good and bad

coverage areas. The distribution of downlink RxLev concentrates from -80 to -95 dBm.

Good Coverage

Bad Coverage


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Coverage Issues

What is

Coverage hole

Sudden Decrease on Signal Level

Line of Sight Lost

Lack of Dominant Server

Coverage Overlapping

Overshooting


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Coverage Hole

RxQuality

RxLevel

Legend

Poor Coverage

Areas

RxLevel(Serving Cell) is about (or less than) -95 dBm

RxLevel(Neighbours) are about (or less than) -95 dBm

Bad

RxQualityCall

Drop


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Sudden Decrease on Signal Level

RxLev(Serving Cell and

Neighbors) decrease in ashort time.

Check if there is big

change of testing

environment, e.g. check

if the test was performedon a highway and that

particular area was a

tunnel or not.

Signal level on the chart

will make a curve rather

than unstable changes.

This usually results in

Ping Pong Handovers

Page 8


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Line of Sight Lost

Page 9

Signal Strength of Serving cell make fast up and down due

to far away server being blocked by obstacles from the

terrain. The other way, signal from the server lose line of

sight(LOS) to the mobile because of a hill of something.

RxQuality goes

worse when the

level drops down

fast


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Lack of Dominant Server

Page 10

Signal Level of more

than one cell (ServingCell and Neighbors)

are not high enough.

This might happen

because the MS is

located on the cell

borders and there is

no any best server to

keep the call.

Lack of Dominant

Server Causes too

many HandoversBetween the same

Cells


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Coverage Overlapping

Signal Level of 34

cells are too closed

to each other.

This might point

overlapping cells.

This will cause

quality problemsbecause of

frequency reuse

Immediate action to

optimize cell

coverage should betaken by by power

reductions, downtilts

or other

configuration

changes.

Page 11


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Overshooting

Page 12

BTS

Serving

cell

Coverage spot

(island effect)Neighbour cell A

BSIC 1

Freq. A

Other cell B

BSIC 1

Freq. A

MS is covered by the

serving cell, but isoutside the cell

BSC thinks that it is

neighbour cell A and

makes a handover to

cell A

The MS is not nearcell A so the

assigned TCH for the

handover is not used

Cell A will have

unused TCH

(handover)

The call might bedropped because it

cannot make the

handover


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Proposal of Coverage Issue

Solution of low coverage

Solution of overshooting and overlapping


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Solutions of Low Coverage

Possible solution can be listed as below:

New Site ProposalSector Addition

Site Configuration Change (Antenna Type, height, azimuth, tilt changes)

Loss or Attenuation Check ( Feeders, Connectors, Jumpers, etc..)

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Proposal Remark How to do

New Site ProposalMost effective solution,but the cost is highest

Using prediction tool(U-net) to identify the bestlocations to put new sites

Sector AdditionEffective solution

but only for Omni-Site

Using prediction tool(U-net) to identify the

recommended azimuth of new sectors

Antenna

Height Difficult, high cost


recommended height, type, azimuth or down tilt of

sector.

Type Difficult, high cost

AzimuthEasy to operate

Downtilt Easy to operate

Hardware

Feeders Only for troubleshooting

Referring to hardware checking guide

Connectors Only for troubleshooting

Jumpers Only for troubleshooting


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Solutions of overshooting or overlapping

Page 15

Possible solution can be listed as below:

Site Configuration Change (Antenna Type, height, azimuth, tilt changes)Cell Configuration Change (Carrier Power Type, Static TRX Power Class, Fine

Tuning of Static TRX Power)

Proposal Remark How to do

Antenna

Height Difficult, high cost


recommmended height, type, azimuth or

downtilt of sector.

Type Difficult, high costAzimuth Easy to operate

Downtilt Easy to operate

Parameter Output Power relatedEasy to operate, but with

risk of coverage reduction

Referring to Data Configuration Reference

Help


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analyze coverage issue in dt

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