Coverageand

Containment

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 poor coverage examples– Probable coverage holes

– Site add

– Design changes

Coverage Optimization

• Objectives

– Create the “right” coverage for each location

– Minimize Interference

What is the “Right” Coverage?

• Creating Dominant Servers

– Each location ideally has one dominant server

• Eliminating coverage gaps

• Minimizing interference

What Limits the Coverage?

• Downlink

– Maximum downlink power allocated for a traffic channel

• Uplink

– Max uplink transmit power from MS

Discuss other factors!

Coverage scenarios

• On street

• In Car

• In building (1-wall)

• In building (3-wall)

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)

Coverage Optimization Process

• Input

– Scanner Data

– Mobile “Camped On” Cell RxLevIdle

– Prediction Tool Plots

– Test transmitter (site selection)

• Tasks

– Identify each sector’s coverage pattern

– Eliminate over-spray where sector is dominant (and shouldn’t be)

Per Sector Coverage Data

Analysis

– Answer the following for each sector’s coverage pattern:

What is the design intent of this sector’s coverage?

Where is this sector dominant?

Where should this sector be dominant?

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

Is this sector contributing to excessive coverage?

Is this sector under-performing (network stats)?

Coverage Planning

• Planning Tool Example

– Site addition

– Possible coverage holes

– Design changes impacts

Summary

• Other useful plots

– RxLev Sub Plots

– C1 Plots

• Use of coverage plots

– Access failure analysis

– Dropped call analysis

– Throughput analysis

Interference

Confidential

Interference

• Types of Interference

• Sources of Interference

• Detecting Interference

• Methods to Reduce Interference

Confidential

Types of Interference

Types of Interference

External Interference

Internal Interference

Co-Channel Interference

Adjacent Channel Interference

External Interference

• Sources of External Interference

•Noise from other RF sources

•Man made noise

Automobiles, Machines, Power Lines, etc.,

•Galactic Noise

From Sun, Stars etc.,

•Atmospheric Noise

Mostly from Lightning..

Co-Channel Interference

Confidential

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

Carrier, F1 Interferer, F1

C

I

C/I > 12 dB (Design criteria)

C/I > 9 dB ( GSM Rec.)

Types of Co-Channel Interference

Confidential

Downlink Co-Channel Interference

Uplink Co-Channel Interference

Frequency re-use

Confidential

A1

A2A3

B1

B2B3

C1

C2C3

D3

D2D1A1

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

Potential Interferers

Potential Interferers

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 dependent on the amount of traffic in the cell

Difficult to detect which cell is interfering, if there are more cells with the same BCCH around the interfered cell

TCH – TCH Interference

Confidential

• 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 tomake 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

TCH – TCH Interference

Confidential

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

Adjacent Channel Interference

Confidential

Adjacent - Channel interference: It is the relation between the desired signal C and undesired signal A, both using the adjacent carrier frequency.

Carrier, F1Interferer F1+1 or F1-1

C

A

Adjacent Channel Interference

Adjacent Channel interference: It is the relation between the desired signal C and undesired signal A, both separated by 200Khz

fx fx+200khz

C

A

C/A > -9 dB

Time Dispersion

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

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

C

R

Detecting Interference

• Detecting Interference

Detecting External interference

Detecting internal interference

Tools for detecting interference

Methods of detecting interference

Confidential

Detecting External Interference

• Other RF Sources:

Spectrum Analyzer

Directional Antenna

(Operating in the required band)

Confidential

Source: www.Agilent.com

Interference Analyzer

Detecting Interference using Interference Analyzer:

• Racal - SmartAIR

• Rohde & Schwarz - Roger TS 9958

• Agilent – E6474A / E7475A

Interference Analyzer

• Detecting Interference in the network

• Measurement of Interfered and Interfering Signal

• Identifying to which cell the interfered and interfering signal belongs to.

General Coverage Analysis process•Study 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 cell coverage/containment.

• In Mapinfo, plot serving with neighbors in idle mode and identify potential interference.

• Per cell, look at the individual tilts/height with general field clutter information

•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 for intended coverage

Objectives for 13/01/09

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

• TEMS Drive test process, different test set ups

• Validating TEMS drive logs.

• Initial set-up in TEMS/Actix

• Loading drive data into Actix tool

• Analysis windows/options in TEMS/Actix

• Using MapInfo

• Site database ,Network Site level statistics.

• Examples review