Coverage Session Slides

7/27/2019 Coverage Session Slides

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Objectives

Review distributed files Setting up the tools for coverage analysis

Prioritizing your work Selecting top coverage issues

Categorizing In-building, In car, On-street coverage Identifying potential interference locations

Walk through on coverage examples Probable coverage holes scenario

Probable multi server scenario

Design changes


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What is the Right Coverage?

Creating Dominant Servers Each location ideally has one dominant server

Eliminating coverage gaps

Minimizing interference


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What Limits the Coverage?

Downlink Maximum downlink power allocated for a

traffic channel

Uplink Max uplink transmit power from MS

Discuss other factors!


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Coverage scenarios

On street In Car

In building (1-wall)

In building (3-wall)


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Interference

Minimizing interference Definition:

4 or more servers within 5 dB of strongest, inclusive

Example:

Impacts:Access failures

High HO reduced capacity Drops in extreme cases

Impact to throughput (for GPRS/EDGE)


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Coverage Optimization Process

Input Scanner Data

Mobile Camped On Cell RxLevIdle

Prediction Tool Plots Test transmitter (site selection)

Tasks

Identify each sectors coverage pattern Eliminate over-spray where sector is dominant

(and shouldnt be)


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Per Sector Coverage Data

AnalysisAnswer the following for each sectors coverage

pattern:

What is the design intent of this sectors coverage?

Where is this sector dominant?

Where shouldthis sector be dominant?

Is this sector over- (or under-) covering?

Is this sector contributing to excessive coverage? Is this sector under-performing (network stats)?


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Summary

Other useful plots RxLev Sub Plots

C1 Plots

Use of coverage plotsAccess failure analysis

Dropped call analysis

Throughput analysis


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Interference

Confidential


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Interference

Types of Interference Sources of Interference

Detecting Interference

Confidential


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Types of Interference

Types of Interference

External Interference

Internal Interference Co-Channel Interference

Adjacent Channel Interference


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External Interference

Sources of External Interference

Noise from other RF sources

Man made noiseAutomobiles, Machines, Power Lines, etc.,Galactic Noise

From Sun, Stars etc.,

Atmospheric NoiseMostly from Lightning..


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Co-Channel Interference

Co Channel interference: It is the relation between thedesired signal C and undesired (Interfering or re-used) signal I,both using the same carrier frequency.

Carrier, F1 Interferer,F1

CI

C/I > 12 dB (Design criteria)

C/I > 9 dB ( GSM Rec.)


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Types of Co-Channel Interference

Downlink Co-Channel Interference

Uplink Co-Channel Interference


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Frequency re-use

A1

A2A3

B1

B2B3

C1

C2C3

D3

D2D1

A1

A2A3

B1

B2B3

C1

C2C3

D3

D2D1

A1

A2A3

B1

B2B3

C1

C2C3

D3

D2D1

A1

A2A3

B1

B2B3

C1

C2C3

D3

D2D1

A1

A2A3

B1

B2B3

C1

C2C3

D3

D2D1

A1

A2A3

B1

B2B3

C1

C2C3

D3

D2D1

A1

A2A3

B1

B2B3

C1

C2C3

D3

D2D1

Potential

Interferers

PotentialInterferers

PotentialInterferers


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Internal Interference

BCCH BCCH interference TCH TCH interference

BCCH BCCH interference: Can be identified by poor call origination rate in the

interfered cell

More call drops in the BCCH Carrier

BCCH interference is not always dependent on theamount of traffic in the cell

Difficult to detect which cell is interfering, if there aremore cells with the same BCCH around the interferedcell


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TCH TCH Interference

TCH carriers are reused contribute to co-channelinterference.

It will be present only when these TCH carriers have callactivity

To check this type of interference calls are originated oneach timeslot of suspected reused TCH carriers & the C/Ivalues are measured

Easiest method to solve this measurement problem is to

make Delta (difference) measurements, that is Instead ofmeasuring C/I on the T1 (common TCH carrier frequency),we make a delta measurement of B2 / B1 , which is nearto the C/I value of T1


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TCH TCH Interference

Cell 1 has BCCH carrier on ARFCN B1 and cell 2 hasBCCH carrier on ARFCH B2 while both have TCH carrierson ARFCN T1


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Adjacent - Channel interference: It is the relationbetween the desired signal C and undesired signal A, bothusing the adjacent carrier frequency.

Carrier, F1Interferer

F1+1 or F1-1

CA


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Adjacent Channel interference: It is the relation betweenthe desired signal C and undesired signal A, both separated by200Khz

fx fx+200khz

C

AC/A > -9 dB


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Time Dispersion

C = Direct signalR = Reflected signalC/R > 9 dB

The Reflected signal that are delayed more than 15 micro secmust be at least 9 dB below the direct signal received at thattime instant.

C

R


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Detecting External interference

Detecting internal interferenceTools for detecting interference

Methods of detecting interference

D t ti E t l I t f


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Detecting External Interference

Other RFSources:

SpectrumAnalyzer

Directional

Antenna(Operating in the

required band)

Confidential

Source: www.Agilent.com


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Interference Analyzer

Detecting Interference using Interference Analyzer:

Racal - SmartAIR

Rohde & Schwarz - Roger TS 9958

Agilent E6474A / E7475A


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Interference Analyzer

Detecting Interference in the network

Measurement of Interfered and Interfering Signal

Identifying to which cell the interfered and interferingsignal belongs to.

G l C l i


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General Coverage Analysis processStudy RSSI from scanner and Idle phone RxLev plots.

Compare with the intended (planned) coverage and identify

serving with neighboring cells. Look for potential interference.Plot serving BCCH for camped on cell.

Plot individual coverage (from scanner ) to see per cellcoverage/containment.

In Mapinfo, plot serving with neighbors in idle mode and identifypotential interference.

Per cell, look at the individual tilts/height with general field clutterinformation

Look at stats for per cell usage and performance during busy

hour.Discuss recommendations for any changes required.

Simulate possible changes in Frequency planning tool forintended coverage


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Objectives for 15/02/10

Introduction on Drive Test tool and Actix post-processing tool.

Drive test process, different test set ups

Validating drive logs.

Initial set-up in Actix Loading drive data into Actix tool

Analysis windows/options in Actix

Using MapInfo

Site database ,Network Site level statistics.

Examples review

Documents

Coverage Session Slides