dt analysis - how to analyze coverage issue in dt

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

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47pt

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How to analyze Coverage Issues in DT

Coverage

Downlink RxLevel and Coverage Coverage of single cell Coverage of whole network

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 PowerL = Propagation Losses

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


Coverage(one cell) The following example shows the

downlink 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

R

x

L

e

v

e

l

Variations due to Rayleigh fading


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

Coverage Issues

What is Coverage hole Sudden Decrease on Signal Level Line of Sight Lost Lack of Dominant Server Coverage Overlapping Overshooting


Coverage Hole

RxQuality

RxLevel

Legend

Poor CoverageAreas

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

Bad RxQuality

Call Drop


Sudden Decrease on Signal Level

RxLev(Serving Cell and Neighbors) decrease in a short time.

Check if there is big change of testing environment, e.g. check if the test was performed on 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

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Line of Sight Lost

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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


Lack of Dominant Server

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Signal Level of more than one cell (Serving Cell 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 Handovers Between the same Cells


Coverage Overlapping Signal Level of 34

cells are too closed to each other.

This might point overlapping cells.

This will cause quality problems because of frequency reuse

Immediate action to optimize cell coverage should be taken by by power reductions, downtilts or other configuration changes.

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Overshooting

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BTS

Serving cell

Coverage spot(island effect)Neighbour cell A

BSIC 1Freq. A

Other cell BBSIC 1Freq. A

MS is covered by the serving cell, but is outside the cell

BSC thinks that it is neighbour cell A and makes a handover to cell A

The MS is not near cell A so the assigned TCH for the handover is not used

Cell A will have unused TCH (handover)

The call might be dropped because it cannot make the handover

Proposal of Coverage Issue

Solution of low coverage Solution of overshooting and overlapping


Solutions of Low Coverage Possible solution can be listed as below: New Site Proposal Sector 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 doNew Site Proposal Most effective solution, but the cost is highest

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

Sector Addition Effective solutionbut only for Omni-SiteUsing prediction tool(U-net) to identify the recommended azimuth of new sectors

Antenna

Height Difficult, high costUsing prediction tool(U-net) to identify the recommended height, type, azimuth or down tilt of sector.

Type Difficult, high costAzimuth Easy to operateDowntilt Easy to operate

HardwareFeeders Only for troubleshooting

Referring to hardware checking guideConnectors Only for troubleshooting

Jumpers Only for troubleshooting


Solutions of overshooting or overlapping

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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 costUsing prediction tool(U-net) to identify the recommmended height, type, azimuth or downtilt of sector.

Type Difficult, high costAzimuth Easy to operateDowntilt Easy to operate

Parameter Output Power relatedEasy to operate, but with risk of coverage reduction

Referring to Data Configuration Reference Help

Thank youwww.huawei.com

dt analysis - how to analyze coverage issue in dt

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