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Copyright 2003 AIRCOM International Ltd

All rights reserved. No part of this work, which is protected by copyright,may be reproduced in any form or by any means - graphic, electronic or

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ILSA2 - Application Note

V1.0

Product Support GroupP-TN-010-001-002


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CONTENTS1 INTRODUCTION......................................................................................................... 3

2 FREQUENCY PLANNING.......................................................................................... 3

3 ILSA2 - PROCESS AND DATA FLOW...................................................................... 3

3.1 HIGH-LEVEL ILSA2PROCESS .........................................................................................3 3.2 DATA INPUTS TO ILSA2 ....................................................... .......................................... 5

4 STEPPING THROUGH THE ILSA2 PROCESS ........................................................ 5

4.1 ANALYSIS OF THE EXISTING FREQUENCY PLAN ..............................................................5 4.2 PREREQUISITES ...............................................................................................................6

4.2.1 Propagation Model, Predictions and Best Server Array .......................................74.2.2 Available Frequencies and Frequency Allocation Strategy......................... ........104.2.3 Current Frequency Allocations............................................................................114.2.4 Neighbour Lists and Exceptions................................................. .......................... 124.2.5 Traffic Information / Required Number of Carriers ............................................134.2.6 Interference Table ............................................................... ................................. 15

4.3 SETTING UP THE PLAN...................................................................................................18 4.3.1 ILSA2 Initialisation ................................................................ .............................. 184.3.2 ILSA2 Import Filters ....................................................... ..................................... 204.3.3 ILSA2 Plan List Dialog ....................................................... ................................. 234.3.4 ILSA2 Cost Matrix...................................................................... .......................... 24

4.3.5 ILSA2 Options Dialog........................................................ .................................. 364.4 STARTING PLANNING AND VIEWING PROGRESS............................................................41 4.4.1 Commencing Planning ..................................................... .................................... 424.4.2 Viewing Planning Progress..................................................................................43

4.5 ANALYSING RESULTS....................................................................................................46 4.5.1 Carrier Statistics ................................................................ .................................. 474.5.2 Cell Statistics........................................................................................................47

4.6 FURTHEROPTIONS ........................................................................................................48

5 ALGORITHM DESCRIPTION................................................................................... 49

5.1 PROBLEM DEFINITION...................................................................................................49 5.2 SEARCH ALGORITHMS...................................................................................................50 5.3 ILSA2SEARCH STRATEGY ...........................................................................................51

5.4 COST FUNCTION DESCRIPTION ......................................................................................51 APPENDIX A - FREQUENCY PLAN EXAMPLE .......................................................... 53A.1 SCENARIO DESCRIPTION ...............................................................................................53 A.2 INITIALNETWORKCONFIGURATION .............................................................................53

A.2.1 Network before Site Reconfiguration ............................................................. ......53A.2.2 Worst Interferer Array Statistics ............................................................. .............56A.2.3 Average Connection Array Statistics ...................................................................57

A.3 NETWORKRETUNE .......................................................................................................58 A.3.1 Network after Site Reconfiguration........... ........................................................... 58A.3.2 Frequency Planning Process ............................................................................... 59A.3.3 Retune Results .............................................................. ........................................ 62A.3.4 Worst Interferer Array Statistics ............................................................. .............63A.3.5 Average Connection Array Statistics ...................................................................64

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A.4 PLANNING SUMMARY....................................................................................................65

APPENDIX B - TABLE OF FIGURES ........................................................................... 67APPENDIX C - TABLE OF FAQS................................................................................. 69APPENDIX D - GLOSSARY OF TERMS...................................................................... 71

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1 INTRODUCTION

This application note describes in detail the ILSA2 automatic frequency planning tool,its use within the ENTERPRISE planning system and example planning scenarios.

2 FREQUENCY PLANNING

In essence, a frequency plan can be defined as carrier assignments to TRX.

There are too many possible carrier permutations to ever manually determine the best

frequency plan when you consider the capacity requirements and consequent number of

TRX found in networks today. Consequently, a method must be chosen that provides

an acceptable solution within the constraints of time whilst intelligently observing the

defined quality objectives.

Older, more traditional frequency planning techniques have relied on the ability of

engineers to manually allocate from carrier groups. But with the conflicting pressures

of larger networks, greater traffic capacity while minimising infrastructure costs,

manual planning can no longer be seriously considered.

Automated tools, in general, are not without their own problems. If an automated

method is unable to take into consideration the current plan, the results will most likely

require a complete reconfiguration of the network something that loses operator

revenue when inevitable mistakes occur.

Fortunately ILSA2, the second generation of ASSETs frequency planning tool, uses an

algorithm that constantly searches for improvements. Changes are therefore

incremental, steered by penalties associated with the changes the algorithm can make.By choosing the penalties carefully, the desired goals can be achieved.

3 ILSA2 - PROCESS AND DATA FLOW

The secrets of generating a good frequency plan with ILSA2 can be summarised as:

understanding how to perform the procedural steps involved understanding what inputs are required and whether they are mandatory or optional understanding what outputs you can expect and how to interpret them

3.1 HIGH-LEVEL ILSA2PROCESS

The list and diagram below describes the high level procedural steps. The sections later

in this document provide more details of the sub tasks involved.

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Steps:

i. analyse the existing frequency plan

ii. create the prerequisitesiii. set-up the cost matrixiv. run ILSA2v. analyse the resultsvi. decide whether the plan is acceptable

Start

Create

Prerequisites

Setup ILSA2/Cost

Matrix

Run ILSA2

Analyse Results

Finish

Analyse Existing

Plan

Acceptable

Improvement?

Yes

No

y Worst Interferer Statistics

y Average Connection Statistics

y Frequency Plan Report

y Carriers Required

y Interference Table

y Neighbours and Exceptions

y ILSA2 Setup

y Cost Matrix Setup

y Worst Interferer Statistics

y Average Connection Statistics

y Frequency Plan Report

Figure 1 - Highlevel Flow Chart of ILSA2 Planning Process

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3.2 DATA INPUTS TO ILSA2

The many inputs to ILSA2 are shown in the picture below. Some of the inputs aremandatory and others are optional (shown with an asterisk).

Site

Database

Cost Matrix

ILSA2

Neighbours *

Exceptions *Forbidden

Carriers *

Fixed Carriers *

Carrier Costs

Interference

Table

Wizard

Interference

Costs *

Coverage

Predictor

RF Parameters

Predictions

Array

Creation

Best Server

Array

Frequency

Plan

Traffic

Raster

Wizard

Traffic Raster *

Propagation

Model Editor

Terminal

Types

Propagation

Model

Traffic Spread

Separation

Costs

Required

Carriers

FH Settings *

DTX Settings *

Current Freq

Plan *Carrier Layers

Cell List

CellEquipment *

Exception

Costs

CarrierLayer Costs

Filter

Priorities

HandoverCosts

Cell Equipment

Costs

CellEquipment *

Filters

HandoverCounts *

Figure 2 - Flow of Data within the ILSA2 Planning Process (NeglectingNeighbour Generation)

4 STEPPING THROUGH THE ILSA2 PROCESS

4.1 ANALYSIS OF THE EXISTING FREQUENCY PLANAn important part of the frequency planning process is the verification of improvement.

It may be that the current frequency allocation is close to optimal, and that other

optimisation techniques need to be employed before a significant improvement can be

made. Alternatively, the level of improvement may not be sufficient to justify a retune,

and other frequency planning strategies may need to be employed.

The current frequency allocations should be loaded into the site database and

interference arrays generated and analysed statistically. Additionally, it can prove

useful to create an interference table and use it to create a frequency plan report.

A number of different interference arrays can be used to analyse the plan, both visually

and statistically, and the Frequency Plan Reporter can be used to detail the separationconstraints that are broken within the current plan.



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Array Description

Worst Connection The Worst Connection array gives the total level of interference

on the worst connection within the pixel - detailing the

connection (the connection can be regarded as either a carrier or

frequency hopping group, as appropriate), and the C/I level in

dB.

Average Connection The Average Connection array averages the total level of

interference across all serving connections at the pixel - detailing

the C/I level in dB.

Worst Interferer The Worst Interferer array gives the individual worst interferer

at the pixel - detailing the C/I level in dB, the interfering cell and

the carrier.

Total Interference The Total interference array gives the ratio of the total signal

strength within the pixel to the total interfering strength in dB.

Note: The arrays calculate the average values of C/I within the pixel, derived from

the predictions for the serving cell and for the interferer. As the predictions are

subject to a statistical distribution, so are the C/I values derived. If we assume

that the predictions follow a Gaussian distribution with standard deviation

(dB) then the standard deviation of the C/I should be 2 (dB). Using thisinformation, appropriate C/I thresholds can be calculated, according to the

probability of meeting a given real C/I within a pixel.

The arrays can be analysed both visually, by making plots of the area to be planned,

and statistically, using the Coverage Statistics dialog box. It is possible to create arraysstatistics over polygons, for example enclosing an urban area. The reports generated

detail the proportion of interference worse than an interference threshold over the area

analysed as a whole, as well as a breakdown by clutter type and by cell.

The Frequency Plan Reporter generates a report detailing all of the separation

constraints broken over the filter of sites analysed. If an interference table is in memory

then the levels of interference caused by each allocation are also detailed.

4.2 PREREQUISITES

The following sections describe the prerequisites for the frequency planning process. It

is vital that the prerequisites are correctly set up and checked before starting to plan

since if the inputs are poor quality then it cannot be expected that the outputs will offer

an improvement in the performance of the network!

It is expected that users follow sensible procedures while editing the site database to

ensure the integrity of the information it contains. If this is carried out correctly it

removes the requirement for laborious checking every time the tool is used.

The following sections also provide a description of how to generate the prerequisite (if

applicable), a number of FAQs (Frequently Asked Questions) and a section detailing

the site database parameters that will affect the validity of that prerequisite.



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4.2.1 Propagation Model, Predictions and Best Server Array

An important prerequisite is to have a propagation model of known accuracy, and to

have calculated predictions of all the sites that will be planned. The predictions shouldbe at an appropriate map pixel resolution and range for the problem considered.

The propagation model is used to predict the coverage of cells, in conjunction with the

RF parameters that are stored within the site database and the mapping data used. The

predictions in turn can be used to create arrays, including the best server array, which is

an important input into the generation of a number of the other prerequisites for ILSA2.

It is a good idea to create and display coverage arrays (or to display service areas) to

check that none of the predictions are clearly incorrect, i.e. all sites give some coverage

and none are dominating areas that they clearly should not.

Common errors found in the coverage array are typically simple to resolve, although acombination of factors may be the root cause. Individual factors may include:

Assigning an invalid model (e.g. a microcell model to a macrocell) Not assigning a slot to a sub-cell Incorrectly specifying the PA output power (e.g. 300.0 instead of 30.00)

The best server array itself is a possible input into the generation of many of the

prerequisites to ILSA2. A best server array is required to generate:

Neighbours, if using the Neighbour Wizard Traffic raster, if using the Spread Live Traffic option Carriers required, if using the Traffic Analysis Tool Interference tables using the Interference Table Wizard

The best server array should be generated to the resolution of the predictions created,over an area that covers all of the service areas of the cells being planned. It is

important that the Filter used to create the array includes all the sites to be planned.

FAQ 1 - Which propagation model should I use?

There are two propagation model styles provided with the basic version of ASSET. These can beused to calibrate accurate propagation models for different situations, which can be used to createpredictions for use with ILSA2. Each propagation model style has a number of differentcharacteristics:

Characteristic Standard Macrocell Microcell

Map Data Required Clutter and Height of sameresolution(s) no minimumresolution.

Clutter and Height of sameresolution(s) minimumresolution 5m.

Building Vector Data.

Below roof h

Yes, typica Yes, typical

Application Above roof height macrocells.

Cell radius 500m or greater.

eight urbanmicrocells.

Calibration lly to 8dB standarddeviation.

ly to 8dB standarddeviation.



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FAQ 2 - H ll if the wrong model has d to a site?

I th corre ysis

based upon the predictions to be incorrect. The f l ikely symptoms:

ow can you te been adde

f the wrong model is allocated to a site then e prediction will be in

ollowing are

ct, causing any anal

Symptom Cause Condition

The cell the model is allocated to may havefar better coverage than it should,

odel onmacrocell

vectors

dominating over correct cells.

Microcell m no building

The prediction may show a distinction incoverage between areas enclosed bybuilding vectors and those not.

odel onmacrocell

building vectorsavailable

Microcell m

The prediction may be very small anot show a distinction in coverage between

rocell model onmicrocell

-nd should Mac

areas enclosed by building vectors andthose not.

FAQ 3 - W r e affected by the accuracy of thep

The accuracy of the model affects th

Accuracy of the Model Affects

hat in the ILSA2 Planning p ocess will bropagation model?

e accuracy of the following:

In This Way

This has implications for the spreading of traffic within cells.Typically

calculation of service area. For a less densely plannednetwork, where cell service areas are limited by minimumsignal thresholds, inaccuracies in the model will have a greatereffect.

Typically for a densely planned area of theaccuracy of the model will have minimal impact on thiscalculation of nearest neighbours. For a less densely pnetwork, where cell service areas are limited by minimumsignal thresholds, inaccuracies in the model will have a greatereffect upon the calculation of neighbours.

The greatest effect of accuracy of the model is in theinterference table generation process. If, for example, the

Service area calculationfor a densely planned area of the network the

accuracy of the model will have minimal impact on this

Neighbour analysis network the

lanned

Interference table generation

propagation model is accurate to 8dB standard deviation, thenl C/I calculated the standard deviation will be

11.3dB. If the model is accurate to 10dB standard deviation,for each individua

the standard deviation of the C/I will be 14.1dB. The accuracyof an uncalibrated model may be significantly less than this.

FAQ 4 -model?

ple if the

This

2. Manually entering the neighbour lists (by importing or directly into the site database)3. Disabling the interference table allowing ILSA2 to work solely on separation

constraints that you have entered into the cost matrix

What action can be taken if you have no confidence in your current propagation

Even if you have little or no confidence in the propagation model that you have, for exammodel tuning process is still being carried out, ILSA2 can still be used to develop a frequency plan.

can be achieved by:

1. Manually entering the carriers required

(see below) and

While this is possible it is not necessarily desirable.



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FAQ 5 -

y to use the highest resolution mapping data available, with which it takes asensible amount of time to create the predictions to the required radius. The radius used should be

the minimare included in the predictions. To work out the area of coverage it is advisable to create lowresolution predictions over a very large radius, before creating higher resolution predictions over amore restricted range.

a much

What resolution and radius of predictions should be used with ILSA2?

The resolution and radius of the predictions that you should use are dependent upon a number of

issues. There is a compromise that must be made between the accuracy of the prediction and theamount of information that must be manipulated and stored.

As a rule, you should tr

such that the predictions hold the information about the entire area of coverage which is 20dB belowum service threshold. This should ensure that all pixels that might contribute as interferers

Note: It may be the case that you have a number of sites in your network, which pollutelarger area than others. If this is the case it is perfectly sensible to create much largerpredictions for these sites.

FAQ 6 - w

Wheimpo

2.

ool and Interference Table Wizard.3. Candidate and nominal sites th frequency planned should not be included in

the filter used to create the best server array. Including these sites will adversely affect theTool and

4. The best server array should cover the entire service area of all the sites to be frequency

FAQ 7 - W meters in th e predictions from a site?

The following is a list of parameters in the site database that affect the predictions from a site.

Site Object

Property Description

Ho should I set up my best server array for the ILSA2 planning process?

n creating your best server array for the ILSA2 planning process, there are a number ofrtant considerations:

1. All of the sites to be included in the ILSA2 frequency planning process must be included in thearray, by using a filter including all of them.Live sites / sites on the fringes of the region to be planned should be included in the filter usedto create the best server array. These sites will affect the service areas of cells in a realisticmanner. This will increase the accuracy of the Neighbour Wizard, Traffic Raster Wizard, Traffic

Analysis tat are not being

accuracy of the Neighbour Wizard, Traffic Raster Wizard, Traffic Analysis

Interference Table Wizard.

planned.

hat para e site database affect th

Location Physical location of site.

Actual Ground Height nd height at site. If the default value of 0 is enteredSurveyed grou

ASSET assumes the DTM height. (Units: metres)

Prediction Radius ault radius for predictions from this site. (Units: kilometres)The def


Prediction ModelAllocated

Prediction model to use on cell, as defined in the Propagation ModelEditor.

Slot One cell configuconfiguration on

ration per slot, all antenna, feeder and cell equipmenta slot by slot basis.

Antenna Type The antenna for use on slot as defined in the equipment database.

Antenna Azimuth (Units: degrees)

Antenna Downtilt Downtilt positive, Uptilt negative. (Units: degrees)

(Units: metr

Cell Object

Antenna Height es)



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Antenna Correction in/loss for fine tuning. A negative value implies a loss, aFactor

An additional gapositive value implies a gain. (Units: dB)

The absolu

Feeder Type The feeder type for use on the slot, as defined in the equipmentdatabase.

Antenna Location te antenna location, or that relative to the site.

Feeder Length (Units: metres)

Cell Equipment Type The cell equipment type for use on the slot, as defined in the equipmentdatabase.

Cell Equipment e implies a loss, aCorrection Factor

An additional gain/loss for fine-tuning. A negative valupositive value implies a gain. (Units: dB)

Description

Signal Offset The Signal Offset of the sub-cell within its cell layer.

The Signal Threshold of the sub-cell. Below the threshold lower prioritysub-cells will serve the traffic, if they are available. If no lower prioritysub-cells are available then the sub-cell will serve traffic down to theminimum signal threshold held within the Array Creation dialog box.

The TimTiming Advance lower ppriority sub-cells exist thMaximum Timing Advance set within the Array Creation dialog box.

Override to enable multiple model types within a cell. Default disableduses model defined in cell. Model

Sub-cell Object

Property

Signal Threshold

TA Threshold ing Advance threshold for the sub-cell. Further out than thisriority sub-cells will serve the traffic. If no loweren the sub-cell will serve the traffic down to the

Enable Model as defined in the propagation model

editor.

Slot Allocation Slot for use on sub-cell

PA Output Power The PA Power output for use on sub-cell. The EiRP is derived from thisvalue, taking into account losses and gains from the antenna, feeder,and cell equipment. (Units: dBm)

4.2.2

frequency allocation

to be

c in the tool, the frequency

o

(using additional carrier layers with appropriate carriers removed). These might be

Available Frequencies and Frequency Allocation Strategy

Before beginning the planning process you must decide upon your

strategy and create the appropriate carrier layers and cell layers. All frequencies

used should be entered into the system carriers list in the tool.

On e the available frequencies have been identified with

all cation strategy must be decided. Typically this would include:

Deciding if, and how, to use HCS, dual band frequency allocation and MRP

Allocating carriers to BCCH, TCH, and other, carrier layers Deciding if and how FH and DTX are going to be used Identifying frequencies that should not be allocated in areas of the network, on an

individual site (using forbidden carriers in the site database) or regional basis

caused by cross border separation agreements or geographical considerations.

These carriers can then be split into subsets (carrier layers), to help define the frequency

plan. These carrier layers can then be allocated to cell layers in the cell layers dialog

box. Cell layers then can be instantiated as sub-cells to cells.

Within the sub-cell object in the site database it is possible to allocate the individual

carrier layers for use. This is necessary as it is possible to allocate more carrier layers to



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a cell layer than are used. For example it is possible to allocate two carrier layers to

supply the BCCH carriers perhaps BCCH and BCCH_border.

If DTX is to be considered by ILSA2, then the cells at which it is enabled need to be

indicated in the site database, and the appropriate Voice Activity Factor (VAF)

assigned. VAFs are typically considered to be in the range 0.2 to 0.4.

If frequency hopping is to be considered by ILSA2, then the sub-cells at which it is

enabled need to be indicated in se. A choice needs to be made between

synthesiser, site and baseband hopping. If synthesiser or site hopping is enabled then it

for

opping where the number of carriers and TRXs must be identical. Finally

FH must be enabled on a carrier layer basis, on the carriers page of the sub-cell. It is not

possible to allocate FH to a control carrier layer.

FAQ 8 - What Parameters in the site database affect the frequency allocation strategy?

Cell Object

the site databa

is possible to indicate that more carriers are required than TRXs. This is not the case

baseband h


Enable DTX ell.Choose to enable DTX on the c

Voice Activity Factor VAF for the cell which indicates the factor by which the interference isreduced.


Enable FrequencyHopping

This allows the user to enable frequency hopping on the individualcarriers on the carriers page.

Enables the choice between Baseband, Synthesi

Sub-cell Object

Baseband /Synthesiser / SiteHopping

ser and Site hopping onthe sub-cell. With Baseband Hopping the number of frequencies requiredis equal to the number of TRX required. With Synthesiser or Site

encies than TRX can be allocated.Hopping more frequ

Carrier Layers Used Only those carrier layers allocated Used will be considered by ILSA2.

Carrier Layer Hopping The hopping column indicates whether an individual carrier layer usesfrequency hopping. Even if Frequency Hopping is enabled on theGeneral page of the sub-cell then if this column is not allocated, then nofrequency hopping will be considered by ILSA2.

4.2.3 C ncy

The current frequency ed

a st m

urrent Freque Allocations

allocation, including Fixed and Forbidden carriers, may be us

s inputs into the co atrix and ILSA2 itself.



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Sub-cell Object


Allocated Carriers The currently allocated carriers. If improving a current plan, ILSA2

will take these allocations as the initial state of the frequency plan.

Forbidden Carriers The carriers that are forbidden from this site. If improving a current

plan, ILSA2 treats these carriers as subject to the forbidden carriers

cost, as generated within the cost matrix.

Fixed Carriers The carriers that should be fixed to the site. If improving a current

plan, and the retuning of these carriers is allowed, ILSA2 makes a

tdifferent carrier subject to the retune cost, as generated within the cos

matrix

Neighbour Lists and ExceptionsTo allow ILSA2 to make fast initial progress with the frequency allocation problem, th

neighbours and exceptions present in the network should be known. Either th

optimised neighbours from the real network can be entered into the site database,

Neighbour lists can be generated using the Neighbour Analysis Tool. Exceptions can be

tered manually within the tool.

The neighbours are used to generate separation costs within the cost matrix and can

generated in a number of ways as shown below:

Start Start

Input Known

Neighbour

Relationships into

Site Database

Start

Input Known

Neighbour

Relationships into

Site Database

4.2.4e

e

or

en

be

Generate Best

Server Array

Generate Best

Complete

Neighbour

Nei

Analyse Neighbour

Relationahips using

Neighbour Wizard

Update Database

Analyse Neighbour

Relationahips using

Neighbour Wizard

Update Differencesto Database

Finish

Server Array

Finish Finish

Generation

ghbour

Update

our generation is to create a best server array and generate

Figure 3 - Flow Charts Showing Possible Routes for the Generation ofNeighbours

The first method of neighb

neighbour relationships using the Neighbour Wizard. These are then applied to the site

database using the Neighbour Analysis Tool. The advantage of using this method is that

it allows a quick first approximation of the neighbour relationships within the network.



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The disadvantages are that this may not align with the current neighbours set up within

your network, and that it will not produce neighbours with the same accuracy as a well

optimised network. The neighbour wizard creates neighbours when the number of

using the import

functionality within ASSET. The advantage of this method is that it can directly reflect

n the optimised network. The disadvantage of this method is that it

will not account for new sites or cell-splitting, unless these are added manually which is

a ming proce

The third method is a od,

known neighbour relat into the database by hand or by

i est serv n.

However during the ne ediateicinity of new sites or modified sites should be updated.

A2. For each site an

se, either manually or

l carrier assignments, but which are not neighbours.

Pr

pixels at the equal power boundary of the two cells exceeds a specified threshold.

The second method of neighbour generation relies upon direct input of neighbours into

the site database. This could either be manually, site by site, or by

the settings withi

time consu ss.

combination of the previous two. As in the second meth

ionships are added directly

mporting. A b er array is then generated and the Neighbour Wizard is ru

ighbour analysis, only the relationships within the immv

Exceptions can also be used to generate separations within ILS

Exception list can be entered into the cell page of the site databa

by importing. Exceptions represent a list of other cells which should not be allocated

co-channe

Sub-cell Object

operty Description

Neighbour List The neighbour list for a cell a

cost matrix. Neighbours can

ffects the separations created in ILSA2s

either be entered manually or created

using the Neighbour Wizard.

ception List The exception list for a cell indicates the cells for which co-channel

allocations should not be made but which are not neighbours.

Ex

4.2.5 Traffic Information / Required Number of Carriers

Either of these two inputs can be generated first:

spread traffic from sites option in the Traffic Raster Wizard.

2. The traffic raster can be generated first, using the approximated traffic spreadingset within the Terminal Types dialog box, using the Traffic Raster Wizard, and

then using the Traffic Analysis Tool to calculate the required carriers per carrier

layer.

If the required carriers are to be generated from a traffic raster, it is important that the

correct channel to carrier map is allocated to the cell layer. The map defines the

relationship between the number of TCHs available for a specific number of installed

TRX. Only a single channel to carrier map can be allocated per cell layer although five

Two forms of information about traffic are required in the ILSA2 frequency planning

process:

A traffic raster for generation of the interference table The required carriers for every carrier layer of every sub-cell, to allow ILSA2 to

allocate the correct number of carriers

1. The required carriers can be entered directly into the site database fromknown/predicted network statistics, and these can then be used to generate a traffic

raster using the



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maps are supplied with ASSET. If the maps supplied do not match the configuration of

your carriers it is possible to add your own.

These t

ILSA2 requires that the site database contains the required number of carriers in each

carrier layer for the frequency plan. Also, to generate the interference table a traffic

raster is required.

wo inputs can be generated as shown in the flow chart below:

Start

Set Up Terminal

Types

Spread TrafficRaster

Create Best Server

Array

Capture Traffic

Input Required

Carriers to Sites

Database

Create Best Server

Array

Spread TrafficRaster

Start

Set Up Terminal

Types

Set Up Channel to

Carrier Map

Generated Required

Number of Carriers

Directly Input

Required Number of

Carriers

Calculate Required

Carriers

Finish Finish

The first ply described as generating a traffic raster,

and then from the traffic raster to calculate the required number of carriers.

Figure 4 - Flow Charts Showing Traffic Raster and Required CarriersGeneration

method (left flow chart) can be sim

Note: If you have a small number of cells that have a very high control overhead it is

possible to manually edit the required number of carriers at these sites in the

site database, after the new required carriers values have been applied by the

Traffic Analysis tool. This may be preferable to creating a new cell layer with

a different Channel to Carrier map.



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When setting up Terminal Types you are defining how the traffic is spread within your

network. Each Terminal Type can be associated with one or more cell layers. This

makes it possible to separate GSM900 and GSM1800 traffic. Also held within theted with it is spread.

d (right flowchart) may simply be described as entering the required

number of carriers and then using them to generate a traffic raster.

T details

S


Terminal Type are the details of how the traffic associa

The second metho

he table below the database objects involved:

ub-cell Object

The traffic carried by a cell affects the creation ofCarried Traffic the interference table

and can affect the generation of the required carriers

Carriers Required The required number of carriers can be entered manually or allocatedby the Traffic Analysis Tool

TRX Required The required number of TRX may be different from the carriers

required in a synthesiser or site hopping network

Interference Table

An interference table allows ILSA2 to attempt to minimise the interference generated

by the frequency plan. The interference table in ASSET details the effect of

interference for every pair of sub-cell/carrier layer combinations in the network w

4.2.6

hose

predictions overlap. It gives the effect of interference in terms of both area and traffic

be thatarea wh The

inte

affected by interference. The area/traffic affected by interference is calculated toich is defined within an interference weights table for a mean C/I.

rference table is defined on a cell layer basis. The specific interference weights table

to be used is selected during the creation of an interference table using the wizard.

Start

Generate Best

Server Array

Generate Traffic

Raster

Generate

Interference Table

Using Interference

Table Wizard

Finish

Figure 5 - Flow Chart Showing Interference Table Generation Process



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FAQ 9 - verage C/I and the percentage traffic/areaaffected stored?How is the mapping between the a

The mapping is stored in the Interference Weights tables. When generating an interference table,you must specify which interference weights table is to be used. The default interference weightstable within ASSET appears as follows:

Default Interference Weights

0%

25%

50%

75%

100%

Proportionof

Interfe

rence(%)

Co-Channel Adjacent Channel

-20 -10 0 10 20 30 40

Average C/I (dB)

Figure 6 - Default Interference Weights

This default interference weights table has been generated assuming that a co-channel C/I of 9dBC/I follows a

.8dB.

FAQ 10 - enerate the adjacent channel interference weights?

The adjacent channel curve used by the Interference Table Wizard is implied directly from thee Interference page of the Array

FAQ 11 - eights table have?

any the network.

10% of the traffic to be operating in unacceptableinterference.

akingassignments where a C/I of 9dB is possible.

is where the quality of a connection begins to be adversely affected, and that the

Gaussian distribution about the calculated mean, which has a standard distribution of 7

How does the Interference Table Wizard g

specified co-channel curve by applying an offset specified on thCreation dialog box. The default offset is -18dB.

What values can the Interference W

It is not necessary to stick to a Gaussian distribution, or a maximum of 1: the table can be assignedvalues to reflect the distribution/severity of interference in

For example, consider a network where

The propagation model was known to be accurate to a standard deviation of 8dB, and the C/Iassumed to be accurate to 11.3dB standard deviation.

The required C/I for acceptable operation were 9dB. The network target was for less than

A C/I curve could be generated to measure the probability of the C/I being worse than 9dB, usingsimple Gaussian statistics. However this does not bias the ILSA2 significantly against m



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Alternatively you could create a curve to measure the probability of the C/I of being worse than ae that, if it wvalu ere the average in the network, result in only 10% of the real C/Is being 9dB or

rs carried out.

If an allocation would result in more than 10% C/Is being worse than 9dB the cost would be

wo e. This target value of C/I would actually be approximately 23dB if this were

A third option could be to alter the curve centred targeting 9dB in such a way that:

increased

If less than 10% C/Is being worse than 9dB the cost would be decreased.

For example, you could square the probability according to the first option and multiply by 10. Thiswould result in the graphs shown below:

Interference Weights - 9dB Rejection

200%

400%

600%

800%

1000%

ProportionofInterference

(%)

11.3dB Standard Deviation >10% Interference Rejection

0%

10 20 30 40

Average C/I (dB)

-20 -10 0

Figure 7 - Interference Weights 9dB Rejection

Interference Weights - 9dB Rejection (Close Up)

25%

50%

75%

100%

ProportionofInterference

(%)

11.3dB Standard Deviation >10% Interference Rejection

0%

20 30 40

Average C/I (dB)

-20 -10 0 10

Figure 8 - Interference Weights 9dB Rejection (Close Up)

These are only suggestions of how the problem might be approached. Other solutions may presentbetter results.



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4.3

en the plan needs to be set up within theILSA2 tool itself. There are two distinct stages to setting up ILSA2, which combine to

to suit your needs. The first stage consists of initialising

Planning tool dialog.

4.3.1 ILSA2 Initialisation

The ILSA2 Initialise d certain prerequisites are

imported into ILSA2.

SETTING UP THE PLAN

Once the prerequisites have been generated th

allow you to create a plan

ILSA2, where the Network, Interference and Network Counters prerequisites can be

imported. Further options are available in the second stage, and are accessed from the

main ILSA2 Frequency

ialog allows the user to specify how

Figure 9 - ILSA2 Initialise Dialog

The ILSA2 Initialise Dialog

Property Action

allows the setting of:

Description

This option allows current network configurations from the site

database to be imported into ILSA2. Use the Import Filters button

to select the exact configuration to be planned (see 4.3.2).

If this option is selected and no filters have yet been imported, if

the user attempts to initialise a warning wil

be available for ILSA2 to plan. It is possible to initialise ILSA2

without importing filters, although planning will not be possible.

Checking this option allows a network configuration stored in

XML export files to be imported into ILSA2 for planning. Use the

Data from

memory

l appear as no cells will

Network

File

browse button to locate the required files.

To use this method, complete network data must be selected for

import. The files required are those exported using the XML export

functionality in ASSET, with all Project and Configuration options

selected, or using the Save Network option in ILSA2 (section 4.6).



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Data from

memory

If this option is selected, ILSA2 will use the interference

relationships in the current interference table as inputs to the Costfunction.

If there is no interference table currently loaded, no interference

will be taken into account by ILSA2, and the only inputs to the

cost function will be the carrier and separation costs specified

within the cost matrix.

Interference

File If this option is selected, ILSA2 will use the interference

relationships stored in an interference table file (AIT) that has been

created and saved previously. Use the browse button to locate the

required file.

Selecting this option allows ILSA2 to use interference without the

need to generate an interference table each time ASSET is started.

This is of particular use when planning large networks.

If this option is used whilst an interference table is currentlyloaded, the AIT file specified here will take precedence, and the

interference table in memory will be ignored.

None This option prevents ILSA2 from using handover counts as inputs

to the cost function.

Handover

Counts

File Checking this option allows handover counts stored in a handover

counts file (TXT) to be imported into ILSA2 for planning. Use the

browse button to locate the required file.

Initialise Initialise When all three prerequisites have been set as required, the final

step is to initialise ILSA2. If initialisation is successful, the main

ILSA2 Frequency Planning dialog will be displayed.

FAQ 12 - When would you not use interference?

It is generally advisable to use interference, in the form of an interference table, with ILSA2.However it may be the case that you have little confidence in the propagation model that you areusing. In this case the interference table may be unreliable and you may wish to use ILSA2 withseparation and carrier constraints alone.

If an interference table is currently loaded in ASSET, and the Data from Memory option is selected,ILSA2 will automatically load the interference relationships that are in the table and use them asinputs to the cost function. In this case, should you specifically wish to plan without interference, thecurrent interference table should be saved to file (in case it is needed at a later date), and thecurrent ASSET project that is running should be closed and reopened. This will have the effect ofclearing the interference table from memory, allowing ILSA2 to plan without interference.



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4.3.2 ILSA2 Import Filters

The ILSA2 Import Filters wizard allows the exact network configuration to be selected

for planning over four steps.

4.3.2.1 Import Filters Wizard Step 1

Figure 10 - ILSA2 Filter Import Wizard Step 1

On the first step of the wizard, filters and filter folders are presented as in the filter

database. Any of the filter folders, or the individual filters, in the project can be selected

to be included in planning. In a project that contains a large number of filters in various

folders, this page allows groups of filters to be selected or deselected quickly.



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4.3.2.2 ILSA2 Import Filters Wizard Step 2


In the second step of the wizard, the filters chosen in the first step are presented without

the associated folder hierarchies. This page allows the user to further select any of the

filters that are required for planning. Sites that are to be considered, even if not

modified, must be included in the filters selected.

Filter priorities are also editable at this stage of the wizard. The properties of sites

which belong to multiple filters within the list are determined by the order of the filters

within the list. The properties of the top filter in the list have precedence.

FAQ 13 - What happens if a site is identified by multiple filters?

Only one set of allocations can be made to a site, even if that site is present in the results of morethan one filter that ILSA2 is planning. Consequently, the order of the filters in the list is importantand can be modified by using the up and down buttons.



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The third step of the wizard allows users to select which cell layers in the project are

required to be planned. In a project that contains a large number of cell layers, this page

allows groups of filters to be selected or deselected quickly. A typical use for this

would be when only planning GSM1800 cell layers in a dual band project environment.





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The last step in the wizard allows the user to make detailed selections of the

combinations of filters and cell layers that are required for planning. This step is used to

prevent unnecessary filter / cell layer combinations from being imported into ILSA2:minimising the amount of data that the algorithm must consider will improve the rate at

which ILSA2 arrives at an optimal solution. As was the case with filters, cell layers that

are to be considered, even if not modified, must be included in the cell layers selected

here.

FAQ 14 - When to include/ignore filter/cell layer combinations?

When planning, the complexity of the filter/cell layer combinations can severely impact the speed atwhich a solution is reached. If due to the nature of the frequency banding technique chosen, youcan disregard a particular cell layer since it is no possible impact on the others, it is advisable toignore the layer completely. This would happen when considering a dual-band network and onlyplanning the 900MHz layer. In this case the 900MHz layer and 1800MHz layer can be considered

independent of one another.

4.3.3 ILSA2 Plan List Dialog

After ILSA2 has been initialised, a plan list can be displayed and edited. For each

Filter/Cell Layer/Carrier Layer combination that was imported using the Import Filters

wizard you can choose to either plan, read only or to ignore the sub-cells included in

the list. The Plan List dialog is accessed from the View menu on the main ILSA2

Frequency Planning dialog.

Figure 14 - ILSA2 Plan List Dialog

The Plan List dialog displays the filter/cell layer/carrier layer combinations that were

imported into ILSA2. The dialog is used to define which combinations are to be

considered by the plan. The items that are available on the Plan List page include:



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Option Description

Plan List The Plan List is a list of all the filter/cell layer/carrier layer combinations that

the cost matrix includes. There are three options for each item.

Plan The plan option enables ILSA2 to plan the carriers required within sites

satisfying the filter/cell layer/carrier layer criteria. The carrier allocations can

be modified and are considered by other carrier allocations as interferers.

Read Only The Read Only option disables ILSA2 from planning the carrier allocations

required within sites satisfying the filter/cell layer/carrier layer criteria. The

current carrier allocations can still be considered as interferers by ILSA2

when planning other carrier allocations.

Ignore This option ignores sites satisfying the filter/cell layer/carrier layer criteria.

FAQ 15 - When would you use the plan/read only/ignore options?

If you wish to plan sites then it may be important to take into account frequency allocations inneighbouring regions. In this case the filter/cell layer/carrier layer combinations describing theneighbouring regions should be assigned the read only option. It may also be that there arecombinations within the plan list that you neither wish to plan nor take account of. Thesecombinations should be set to ignore.

4.3.4 ILSA2 Cost Matrix

The cost matrix within ILSA2 allows you to define the rules within which ILSA2

operates. It allows you to choose the separation constraints, and the desirability of the

constraints being met. The ILSA2 Cost Matrix is accessed from the Cost Matrix menu,

which contains the following functionality:

Option Description

Load This option allows you to load a previously saved cost matrix (CMF file).

When loaded, the user is given the option of immediately reviewing the cost

matrix.

Save This option allows you to save the current cost matrix (CMF file).

Edit This option opens the Cost Matrix Editorwhere the current cost matrix can be

edited (see subsequent sections 4.3.4.1 to 4.3.4.8).

Note: When ILSA2 is closed, or when it is re-initialised, the current cost matrix is

lost. For this reason, it is suggested that large cost matrices are always saved

before ILSA2 is closed or re-initialised, and then re-loaded.



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4.3.4.1 ILSA2 Cost Matrix Carrier Costs

The first folder in the ILSA2 Cost Matrix Editor is used to specify the constraints and

costs for individual carriers.

Figure 15 - ILSA2 Cost Matrix Carrier Costs

The ILSA2 Carrier Costs folder allows the user to view and edit the carrier costs (i.e.

costs associated with a single carrier on a single carrier layer of a single subcell). The

following options are available:


Cell ID The cell ID of the subcell for which a carrier cost is defined.

Cell Layer The cell layer of the subcell for which a carrier cost is defined.

Carrier Layer The carrier layer for which a carrier cost is defined.

Carrier The individual carrier for which a carrier cost is defined.

The actual cost associ

following situations:

If the cost type is forbidden, the cost will be

assigned to this carrier layer of this subcell.

If the cost type is fixed, the cost will b

Cost Type Whether the individual carrier is a Forbidden carrier or a Fixed carrier.

Cost ated with the individual carrier, applied in the

applied if this carrier is

e applied if this carrier is removed

from this carrier layer of this subcell.

FAQ 16 - How should Forbidden Carrier Costs be used?

In this way,the cost matrix is used to fine tune how ILSA2 deals with the allocations at these sites.

It is useful to be able to edit forbidden carrier costs on an individual carrier basis if the undesirabilityof making carrier allocations varies significantly between sites. It may be that, for some sites,making a certain allocation is undesirable, while for other sites it is absolutely imperative that theallocation is not made. Within the site database both of these situations can be considered asforbidden carriers. When each forbidden carrier is considered by ILSA2, different costs should beincurred depending on how important it is that the allocation is not made to this carrier.



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FAQ 17 - How should Fixed Carrier Costs be used?

As with forbidden carriers, the costs assigned to fixed carriers should reflect how important it is that

ILSA2 does not de-allocate the carrier. It will be highly likely that this level of importance will vary ona site to site basis. The cost associated with a fixed carrier would normally be set high enough suchthat ILSA2 is strongly discouraged from de-allocating that carrier. If the carrier is then de-allocated,in all probability there is something amiss in the network design that means that the inclusion of thiscost makes an improvement to the overall plan.

FAQ 18 - Why cant I assign individual carrier costs to all possible carriers?

Only forbidden and fixed carriers are considered in the carrier costs folder.

4.3.4.2 ILSA2 Cost Matrix Carrier Layer Costs

The second folder in the ILSA2 Cost Matrix Editor is used to specify the constraints

and costs for carrier layers that are to be planned.

Figure 16 - ILSA2 Cost Matrix Carrier Layer Costs

The ILSA2 Carrier Layer Costs folder allows the user to view and edit the carrier layer

costs (i.e. costs associated with actions that apply to an entire carrier layer). The

following options are available:Property Description

Filter The filter name that contains the carrier layer for which costs are

defined.

Cell Layer The cell layer that contains the carrier layer for which costs are defined.

Carrier Layer The carrier layer for which costs are defined.

Weight The weight option is used to define the importance of Filter/Cell

Layer/Carrier Layer combinations relative to each other.

Typically you would use low weightings between 1 and 10.

Allow Retune If this option is selected for a carrier layer, ILSA2 is allowed to retune

it. The option would generally be used when considering the Use

Current Plan option (section 4.4), although it has identical functionality



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when creating a new plan.

With the option selected, ILSA2 is able to retune any allocated carrier

on the carrier layer. If it does so, the associated retune cost will beincurred for each carrier that is retuned.

With the option deselected, ILSA2 is not able to retune any allocated

carriers on the carrier layer.

Note: this option is solely concerned with allocated carriers, NOT fixed

carriers.

Retune Cost The actual cost associated with retuning any carrier on the carrier layer.

The value should be set such that retuning a carrier on the carrier layer

is only of benefit to the overall cost of the plan because it will allow

considerable improvements in other areas of the network.

Note: Only filter/cell layer/carrier layer combinations that have been assigned a

planning status of Plan in the Plan List dialog will be displayed in the Carrier

Layer Costs folder.

FAQ 19 - When to use weightings?

Weightings can be used on a carrier layer by carrier layer basis to increase the importance of anyinterference or separation breaking on those carrier layers. For example, interference on the BCCHcarrier is regarded as more important than interference on the TCH carriers, and so the weightingon the BCCH carrier layers would be higher than the weighting on the TCH carrier layers.

FAQ 20 - How should the retune option be used?

The retune option for carrier layers can be used in two ways:

1. Deselecting the Allow Retune option for carrier layers that truly cannot be retuned. Forexample, if adding a new cell, it may be that carriers can be found to meet acceptableinterference criteria without changing any of the current allocations on the same carrier layer.This option would typically be tried before option 2.

2. Allowing the carrier layer to be retuned, but only at a cost. This option can be used to try tomaintain a majority of the current frequency plan. For example, when adding a few new cells tothe network, instead of retuning every cell within the region, it is best to change just enough tomeet acceptable interference criteria. This can be used to give ILSA2 slightly more flexibilitythan preventing all retuning from occurring.

FAQ 21 - How would you re-plan in a localised area?

For example, take the case when adding a new site to an existing design. In this case, you would

expect to have to re-plan the immediate cells surrounding the new site be reluctant to re-plan cells more than a neighbour relationship away, but if the plan was

significantly better then you would accept minor changes

want the majority of the existing design to be read-only

To achieve this create three dynamic filters based on polygons named Area for new site, Borderaround new site and Rest of plan.

In the Import Filters Wizard, import the three filters and, in Step 2, order the priority of the filterssuch that Area for new site is at the top and Rest of plan is at the bottom.

In the Plan List dialog, the cell layer/carrier layer combinations for the Rest of plan filter should beset to Read Only, and those of the Area for new site and Border around new site filters should be

set to Plan.



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In the Carrier Layer costs folder, set the Allow Retune checkbox for all the filter/cell layer/carrierlayer combinations (note that the cell layer/carrier layer combinations for the Rest of plan filter arenot present). For the cell layer/carrier layer combinations of the Border around new site filter

choose an associated cost of performing the retune. The cost should be high enough to ensure thatcarriers are re-planned in the border region only if a significant improvement is made: the valuereally depends on how critical it is to you that the number of changes should be minimised themore important, the higher the cost. It may take a couple of iterations (without applying the changesto the database) before the optimal retune cost is found.

4.3.4.3 ILSA2 Cost Matrix Equipment Costs

The third folder in the ILSA2 Cost Matrix Editor is used to specify the Site and Cell

separation constraints that ILSA2 should aim towards. A separation of 0 corresponds to

a co-channel allocation, 1 to an adjacent channel allocation, and so on. The costs

incurred if these separation constraints are not met are also defined here. The

separations and costs are defined at two levels, these being absolute minimum andpreferred values.

Figure 17 - ILSA2 Cost Matrix Equipment Costs

The ILSA2 Equipment Costs folder allows the user to view and edit the required

separations, and associated costs, for each of the equipment types. The following

options are available:


Equipment The equipment type for which a separation, and associated cost, is

defined. There are two mandatory equipment types that ILSA2

considers, Site and Cell, but any other equipment that is defined to cells

will be listed here, so that separations and costs can be specified at an

extra level of detail.

Cell separations apply to carrier assignments made on the same cell, i.e.

intra-cell separations.

Site separations apply to carrier assignments made on the same site, i.e.

inter-cell separations.

If an assignment on a cell breaks both Site and Cell separations, costs

for both equipment types will be incurred.

If any cell equipment is defined for cells, the separations and associated

costs for the equipment will take precedence over, and is therefore used



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in place of, cell separations and costs.

Cell Layer The cell layer that the equipment separations apply to.

Carrier Layer The carrier layer that the equipment separations apply to.

Min Separation The absolute minimum separation required.

Min Cost The cost incurred if the minimum separation is not met.

Pref Separation The separation preferred.

Pref Cost The cost incurred if the preferred separation is not met.

and apreferred separation of 4, with the cost of breaking it of 100, the following costs would apply:

Separation Cost (ignoring all other costs and interference)

FAQ 22 - How is the cost calculated when separation constraints are broken?

If a constraint is set to a minimum separation of 2, with the cost of breaking it of 1000,

4 or greater 0

3 100

2 200

1 1000

0 2000

As can be seen above, cost values are summed for each reduction in separation. If only thepreferred separation is broken, only the preferred cost is summed. If the minimum and preferredseparations are broken, only the minimum cost is summed.

costs are defined at two levels, these

being absolute minimum and preferred values.

4.3.4.4 ILSA2 Cost Matrix Neighbour Costs

The fourth folder in the ILSA2 Cost Matrix Editor is used to specify the First and

Second Order neighbour separation constraints that ILSA2 should aim towards. As

above, a separation of 0 corresponds to a co-channel allocation, 1 to an adjacent

channel allocation, and so on. The costs incurred if these separation constraints are not

met are also defined here. The separations and

Figure 18 - ILSA2 Cost Matrix Neighbour Costs



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The ILSA2 Neighbour Costs folder allows the user to view and edit the required

separations, and associated costs, for neighbour relationships. The following options

are available:Property Description

Neighbour The neighbour relationship type for which a separation, and associated

cost, is defined. There two options considered are First Order

(Neighbour) and Second Order (2nd Order Nbr).

If both first and second order relationships exist between a pair of cells,

costs can be incurred for both separation constraints if they are broken.

Cell Layer The cell layer that the neighbour separations apply to.

Carrier Layer The carrier layer that the neighbour separations apply to.

Min Separation The absolute minimum separation required.




FAQ 23 - What is the cost if more than one constraint applies to a separation?

minimum and preferred neighbour separation constraints and (bracketed) costs are 1 (50) and 2 (5).

Separation Site Cost bourst

all other costs andrference)

If more than one constraint applies, the costs of breaking the constraints are cumulative. Forexample, site and first order neighbour constraints might co-exist. In this case, the minimum andpreferred site separation constraints and (bracketed) costs are 2 (250) and 4 (25) respectively. The

NeighCo

Cost (ignoringinte

4 or greater 0 0 0

3 25 0 25

2 50 0 50

1 250 5 255

0 500 55050



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4.3.4.5 ILSA2 Cost Matrix Exception Costs

The fifth folder in the ILSA2 Cost Matrix Editor is used to specify the exception

separation constraints that ILSA2 should aim towards. As above, a separation of 0

corresponds to a co-channel allocation, 1 to an adjacent channel allocation, and so on.

The costs incurred if these separation constraints are not met are also defined here. The

separations and costs are defined at two levels, these being absolute minimum and

preferred values.

Figure 19 - ILSA2 Cost Matrix Exception Costs

The ILSA2 Exception Costs folder allows the user to view and edit the required

separations, and associated costs, for exception relationships. The following options are

available:


MSC The MSC of the cell from which an exception has been defined.

BSC The BSC of the cell from which an exception has been defined.

Site The Site of the cell from which an exception has been defined.

Cell The cell from which an exception has been defined.

The cell to which an exce

The absolute minimum separation required. The default value is taken

from that s


Exception ption has been defined (under the Exceptions

tab in the site database).Min Separation

et in the site database, though this can be modified here if

required.



FAQ 24 - What are the separation constraints between exceptions?

folder of the Cost Matrix. The default value of the minimum separation for each exception is takenThe separation constraints between exceptions can be manually edited in the Exception Costs



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from the exception definition in the site database. The preferred separation is set to be two greaterthan the minimum separation.

The site database sets a default separation of 2. In this case the following costs would apply inILSA2:

Separation Cost (ignoring all other costs and interference)

4 or greater 0

3 100

2 200

1 1000

0 2000

4.3.4.6 ILSA2 Cost Matrix Filter Priorities

The sixth folder in the ILSA2 Cost Matrix Editor is used to specify the priorities of the

filters that have been imported into ILSA2. The default values shown here reflect the

priorities that the filters were assigned in Step 2 of the Import Filters Wizard.

Figure 20 - ILSA2 Cost Matrix Filter Priorities

The ILSA2 Filter Priorities folder allows the user to view and edit the priorities that

each of the filters imported into ILSA2 is assigned. The properties of sites which

belong to multiple filters within the list are determined by the associated value of the

filter priority. The following options are available:


Filter The name of the filter imported into ILSA2.

Priority The priority of the filter expressed as a value. Filters with a higher value

have precedence over filters with a lower value.



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4.3.4.7 ILSA2 Cost Matrix Handover Counts and Intermodulation Interference

The seventh folder in the ILSA2 Cost Matrix Editor is used to specify the costs

associated with Handover Counts and Intermodulation Interference. These costs are

considered by ILSA2 if the relevant planning options are also selected.

Figure 21 - ILSA2 Cost Matrix Handover Counts and IntermodulationInterference

The ILSA2 Handover Counts and Intermodulation Interference costs folder allows the

user to view and edit the costs that will be incurred if these two planning options are

included in the planning process. Handover counts describe the number of handovers

that occur between two cells. Intermodulation Interference costs are only incurred ifILSA2 knows the actual frequencies that the carriers pertain to. To enable this,

Frequency Bands must first be setup. A further option to consider intermodulation

interference is included in the ILSA2 Planning Features options (section 4.3.5.2). The

following options are available in the cost matrix:


Use Handover

Count

When this option is selected, ILSA2 imports any handover counts that

were loaded from a handover counts file during the first stage of

initialisation. The counts are then used as an input to the cost function in

a similar manner to a neighbour relationship. The cost that is added is

the number of handovers that occur between a pair of cells.

The Auto Scale and Scale options become inactive when this option is

deselected.

Auto Scale With this option selected, ILSA2 applies an automatic scaling factor

when adding the handover count costs into the cost function. The scaling

factor is calculated such that large numbers of handovers will not swamp

the other costs involved.

The Scale option is inactive when this option is selected.

Scale When Auto Scale is not selected, this option allows the user to input the

required scaling factor for the handover count costs. This method would

be used to increase or decrease the relevance of handover counts relative

to the auto scale factor.

2nd Order This option sets the cost incurred by a carrier assignment that would

cause second order intermodulation interference.

3rd Order This option sets the cost incurred by a carrier assignment that would



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cause third order intermodulation interference.

Uplink Weighting This option is used to apply a weighting to the uplink frequencies. Since

these frequencies cause less interference, a typical value would be lessthan 1.

4.3.4.8 ILSA2 Cost Matrix Separation Costs

The last folder in the ILSA2 Cost Matrix Editor is used to specify the costs associated

with making close carrier allocations between any two individual carrier layers within a

subcell or between subcells.

Figure 22 - ILSA2 Cost Matrix Separation Costs

The ILSA2 Separation Costs folder allows the user to view and edit the costs that will

be incurred if close carrier assignments are made between any two cell/cell layer/carrier

layer combinations that exist in the network to be planned. Costs can be specified for

separations of 0 (co-channel), 1 (adjacent channel) or 2. The folder presents a grid

formation of all possible cell/cell layer/carrier layer combinations and therefore allows

the user to put a higher emphasis on specific network relationships. The following

options are available in the cost matrix:



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Property Action Description

Separation The three close separations for which costs can be defined.

Value The default cost that will be applied to all possible cell/cell

layer/carrier layer combinations in the network (as presented in the

grid) for carrier allocations at that separation.

Costs for co-channel (0) separations would generally be higher

than for adjacent channel (1) separations, which would in turn be

higher than for separations of 2.

Default

SeparationCosts

Reset to

Default

This option resets all cost entries in the grid to the default values

specified. Confirmation is required before the defaults are applied.

Search This option allows the user to move the grid quickly to a certain cell/cell

layer/carrier layer combination. The option presents a dialog allowing the user to

enter the cell ID of the x-axis (horizontal) and y-axis (vertical) cells to be located.

Either the x- or y-axis cell ID may be ignored if necessary.

Grid The grid presents all possible cell/cell layer/carrier layercombinations that exist in the network to be planned. These are

displayed by network hierarchy MSC/BSC/Site/Cell/Cell

Layer/Carrier Layer on both the x- and y-axis.

Grid

Tabs The tabs allow the user to view the costs for the three levels of

separation.

FAQ 25 - Why edit Separations?

The ability to set individual costs for the three closest levels of separation, for any single networkrelationship, allows the user to account for known trouble spots in the network. For example, theeffect of some close separations may be more serious than others, in which case it is desirable forthe cost matrix to include a high cost for making these allocations.

FAQ 26 - How were the default costs in the cost matrix set?

The default costs, seen when a new cost matrix is considered, are set such that they are of a similarmagnitude to typical interference costs. Since typical interference costs are of the order of 10

3

without considering separation constraints, the costs were given values of a similar order to 103.

Constraints that were considered to be more important that others were given larger cost values.

FAQ 27 - Should I modify the default costs for different circumstances?

The costs that you use should always be adapted to the individual planning case that you areconsidering. The values you apply should change according to the different levels of importancethat you assign to the different separations in the network, and to the level of constraint that youdecide to use. Of most importance is that the cost of a cell co-channel separation is greater than thecost of a site co-channel separation, which in turn is greater than the cost of a neighbour co-channelseparation, and so on. Likewise, the cost of a co-channel separation should always be greater thanthat of an adjacent channel, which is in turn greater than a separation of 2, and so on.

A typical approach to setting the cost values would be to start with an initial investigation into thecosts incurred from interference alone. This will form the basis of the values applied to all otherseparation constraints in the network. An iterative approach is then suggested, where plans areapplied (but NOT committed) to the database, analysed against the same criteria used for the initialanalysis, and, if not satisfactory, re-planned after fine tuning the costs in the cost matrix. It may takeseveral revisions to arrive at an optimal set of costs.



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4.3.5 ILSA2 Options Dialog

The ILSA2 Options dialog, accessed from the Tools menu on the main ILSA2

Frequency Planning dialog, allows the user to set a number of display and planningoptions for use with ILSA2.

4.3.5.1 ILSA2 General Options

The ILSA2 General Options page allows the user to set the display and save options for

use with ILSA2.

Figure 23 - ILSA2 General Options

The ILSA2 General Options page allows the setting of:

Property Action Description

X-Axis:

Iteration

This option draws a new section of graph when an improvement

has been made to the cost of the frequency plan.

Graph

X-Axis:

Increment

This option draws a new section of graph at steady intervals in the

number of iterations.



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Refresh Rate This parameter indicates how quickly the main ILSA2 Frequency

Planning dialog refreshes itself. The actual refresh rate iscalculated by multiplying the value entered in the field by 500ms,

e.g. if 10 were entered, the dialog will be refreshed every 5s.

Setting a slow refresh rate means that several improvements to the

plan may be made before the dialog is updated, and will therefore

not be seen by the user. Setting a faster refresh rate increases the

chance of seeing a cost improvement as soon as one is found.

Display

Log Results in

Message Log

Checking this option writes the current cost to the message log

every minute.

Saving Auto-Save

Assignments

Setting this option enables the current best plan that ILSA2 has

found to be periodically saved automatically. With the option

checked, the user can specify how often, and to which location the

plan can be saved. The file that is saved is an XML file of all data

that is applicable to the frequency plan.

4.3.5.2 ILSA2 Planning Features

The ILSA2 Planning Features page allows the user to set a number of extra options that

ILSA2 will use in the planning algorithm.

Figure 24 - ILSA2 Planning Features Options

The ILSA2 Planning Features page allows the setting of:


Use Frequency

Hopping Diversity

Gain

When this option is selected, ILSA2 will apply a gain to the interference

costs that assignments incur on any frequency hopping subcells. The

gain that is applied is dependent on the number of frequency hopping

carriers that will be allocated to subcells.

Aggregate Carriers

Required under Site

Hopping

This option applies to subcells that have Frequency Hopping enabled,

and Site Hopping selected as the hopping type.

If selected, ILSA2 takes the carrier requirement of each sub-cell to be

the sum of all carriers required for all subcells with which it is

synchronised in frequency hopping (that is, co-site, co-cell layer site

hopping subcells). This is typically used in nominal planning when



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traffic analysis has been used to set the required carriers.

If unselected, ILSA2 presumes that site hopping synchronised sub

on a site have already had their carrier requirements set, with allsynchronised subcells on that site sharing the same carriers. This is

-cells

typically used in when planning using data from an existing network.

Use Antenna

Hopping Gain

assumes that a fixed number of antennas (2) are

When this option is selected, ILSA2 will apply a gain to the interference

costs that assignments incur on subcells with Antenna Hopping enabled.

The gain that is applied

available to hop over.

Use DTX load

factors as set in the

se

which DTX is enabled is multiplied by

site databa

Selecting this will reduce the interference caused by sub-cells with DTX

set. The weighting of the cells on

the VAF set in the site database.

Consider

Intermodulation

Interference

rmodulation

dictate how close an intermodulation frequency would need to be to a

Setting this option means that ILSA2 will take inte

interference into account in the planning process.

When selected, tolerance values for both 2nd and 3rd orderintermodulation interference can be which specified. These values

given carrier before it is considered to interfere.

Selecting this option will cause ILSA2 to allocate frequencies according

to the group planning pattern allocated to the cell layer.

Note: ILSA2 only maintains group planning patterns on a cell basis, not

on a site basis. E.g. within every cell all the carriers will be a member of

a single group, such as A1 or B1. Groups allocated to a si

will not necessarily maintain the group pattern, i.e. a grou

may be allocated to more than one cell on the same site.

interference as an input to the cost function.

If the option to minimise interference by tfunction will take as an input the value of

an allocation from the interference table.

If the interfe

selecting thi

by ILSA2.

If the option to minimise interference by area is selected, the cost

from the interference table.

If this option is sele

input a combination

interference table.

The ratio of traffic vs. area can be specified. 0 indicates that only

area will be used and 100 indicates that only traffic will be used.

If the interference table has been generated without a Traffic r

selecting this option means that only the proportion of interfer

ILSA2.

The cost due to interference of ma

allocation is given by the following formula:

+

=wAwT

C))1((100.

200 subcelln

hannel allocation

where:

C= cost added to cost function by the co- or adjacent c

Use Group Planning

te, however,

p, such as A1,

Minimise

Interference by:

These options provide ILSA2 with three different methods of using

1 - raffic is selected, the costthe traffic affected due to

rence table has been generated without a Traffic raster,

s option means that no interference will be considered

2 -

function will take as an input the area affected due to an allocation

3 - cted then the Cost Function will take as an

of the traffic and area affected from the

aster,

ence

that is contributed by the area affected will be considered by

king a co-channel or adjacent channel



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T= affected traffic value (mE) from interference table

w)

affic and area) to the

same level as the other costs in the cost function.

A = affected area value (km2) from interference table

w = % contribution of traffic henceA is multiplied by (1

ncarriers = total number of carriers required on the subcell

Note: the multiplying factor of 100 is used to scale the affected area

values to the same level as the traffic values; the multiplying factor of

200 is used to scale the interference (made up of tr

FAQ 28 -

d if the site database indicates that frequencyou wish to create a plan that considers the

reduction of interference that this strategy provides.

u ty gain if

using frequency hopping but withoutmodifying every sub-cells frequ tings

FAQ 29 -at is the difference in gain between base-band, synthesised and site

rnal lookup table to determine what gain is provided for a particularnumber of hopping carriers.

Hopping Carriers Hop ityGain (dB)

When should Frequency Hopping Diversity Gain be used?

Frequency hopping diversity gain should be enablehopping is enabled on particular sub-cells and y

Yo would disable the frequency hopping diversi

your plan does not use frequency hoppingyou want to determine what could be achieved not

ency hopping set

How is the frequency hopping diver

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