ILSA User Reference Guide

ILSA User Reference Guide

Software Version 7.0 Reference Guide Edition 1

© Copyright 2010 AIRCOM International All rights reserved ASSET ACP, ARRAYWIZARD, ASSET, CONNECT, CONNECT, DATASAFE, DIRECT, ENTERPRISE, MYRIAD, AIRCOM OPTIMA, RANOPT and WEBWIZARD are recognised trademarks of AIRCOM International. Other product names are trademarks of their respective companies. Microsoft Excel , .NET™, Microsoft Office, Outlook , Vis Visu ual Bas Basiic Wi Wind ndo ows®, s®, Windows XP™, Windows Vista and Word Word are trad tradema emarks rks of th thee Micros Microsoft oft Corporation. This documentation is protected by copyright and contains proprietary and confidential information. No part of the contents of this documentation may be disclosed, used or reproduced in any form, or by any means, without the prior written consent of AIRCOM International. Although AIRCOM International has collated this documentation to reflect the features and capabilities supported in the software products, the company makes no warranty or representation, either expressed or implied, about this documentation, its quality or fitness for particular customer purpose. Users are solely responsible for the proper use of ENTERPRISE software and the application of the results obtained. An electronic version of this document exists. This User Reference Guide finalised on 13 September 2010. Refer to the Online Help for more information. This User Reference Guide prepared by: AIRCOM International Ltd Cassini Court Randalls Research Park Randalls Way Leatherhead Surrey KT22 7TW Telephone: Support Hotline: Fax: Web:

+44 (0) 1932 442000 +44 (0) 1932 442345 +44 (0) 1932 442005 www.aircominternational.com

About This Manual Change History This table shows the change history (if any) of this guide: Edition

Date

Reason

1

13 September 2010

First Official Publish.

Explanation of Symbols Throughout this guide, where appropriate, some symbols are used to highlight particular pieces of text. Three different symbols are in use, and are explained as follows: Symbol

Brief Description

Full Description

Note

Signifies text that should be noted or carefully considered.

Tip

Signifies text that may help you do something in an easier or quicker way.

Warning or Important

Signifies text that is intended as a warning or something important.

Contents Chapter 1 Introduction to ILSA

9

Obtaining User Assistance ................................................................................. 9 Who is This User Reference Guide For?................................................................... 10 About the ENTERPRISE User Reference Guides .................................................... 11 Can You Improve Our User Assistance?................................................................... 12 Obtaining Support ...................................................................................................... 12 Obtaining Further Information and Services .............................................................. 14

Chapter 2 Automatic Frequency Planning for GSM

15

Automatic Frequency Planning (ILSA) ............................................................. 15 The Cost Function of the ILSA Algorithm .................................................................. 16 How ILSA Works ........................................................................................................ 17 The ILSA Process ...................................................................................................... 17 Creating the Prerequisites for a Frequency Plan ...................................................... 19 How ILSA W orks with an Existing Frequency Plan ................................................... 24 Initialising the ILSA Frequency Plan .......................................................................... 24 About the ILSA Frequency Planner Dialog Box ........................................................ 26 Creating and Editing a Cost Matrix ............................................................................ 29 Saving a Cost Matrix .................................................................................................. 34 Loading a Cost Matrix ................................................................................................ 34 Setting the Display Options for ILSA ......................................................................... 34 Setting the Planning Options for ILSA ....................................................................... 35 Running ILSA ............................................................................................................. 37 Example of Using ILSA for a Localised Re-plan ....................................................... 39 Reviewing ILSA’s Results .......................................................................................... 40 Applying an ILSA Frequency Plan to the Site Database ........................................... 42 Exporting Assignments .............................................................................................. 43 Importing Assignments .............................................................................................. 43

Importing Frequency Plans .............................................................................. 44 Analysing a Frequency Plan ............................................................................ 44 How to Analyse a Frequency Plan ............................................................................ 45

Index

47

ILSA 7.0 User Reference Guide Contents

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ILSA 7.0 User Reference Guide Contents

CHAPTER 1

Introduction to ILSA ILSA is ASSET's automatic frequency planning tool. It enables you to carry out the frequency planning of your 2g network, and analyse the resulting plans. As an optional add-on to ASSET, ILSA is licensed separately.

Obtaining User Assistance Using Online Help

ENTERPRISE products come with a complete system of online Help which you can access in three ways: From the Help menu, click Help Contents. Scroll through the table of contents and choose a relevant topic to display. To search for something particular, from the Help menu, click Help Contents and using the Index tab or Search tab, type in a letter or word to start searching for relevant topics. Press F1 in a dialog box to view context-sensitive help (available for most dialog boxes). If you are using ENTERPRISE within a CITRIX environment, to ensure that the Help graphics are displayed, set your display settings to support more than 256 colours.

ILSA 7.0 User Reference Guide Introduction to ILSA

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Using ENTERPRISE User Reference Guides

If you prefer to read printed content, we also provide User Reference Guides. To view or print these as PDFs (Adobe Acrobat portable document format): 1

Make sure you have Adobe Acrobat Reader installed on your PC. If you do not have this, you can install it from the ENTERPRISE CD, or get it from the Adobe website. Adobe and Acrobat are trademarks of Adobe Systems, Incorporated.

2

Click Start on the taskbar, point to Programs, then AIRCOM International, then ENTERPRISE, then Docs. - or Navigate to the Docs folder in the location where you installed the product. If neither of these exists, please contact your administrator.

3

Double-click the PDF file that you want to view.

If you have a customer web account, you can also download the latest User Reference Guides from our website. Checking Release Notes

Each release of the ENTERPRISE software is accompanied by Release Notes, giving important information on system requirements, installation, known issues, upgrades and so on. These notes are included in the ENTERPRISE CD, or you can download them from our website. For any further documentation, such as application notes and extra reference information, please email the support team at the address described in Obtaining Support on page 12.

Who is This User Reference Guide For? The ENTERPRISE User Reference Guides are intended for different audiences, depending on the particular product. Typical prerequisites include a good understanding of the following: The appropriate telecoms technologies and the associated network planning methods (for planning software) Relational database management, and in particular Oracle database creation and administration procedures (for administrative software) The various parameters utilised for monitoring and optimising networks (for OSS software) Irrespective of the particular product, the following basic knowledge is required: Microsoft Windows concepts The functions of the Microsoft Office suite of tools, in particular Excel

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About the ENTERPRISE User Reference Guides This table describes our range of User Reference Guides: This Guide

Contains Information On

What's New

The main difference between the latest versions of the ENTERPRISE suite.

ENTERPRISE Installation and Administration

Installing and configuring ENTERPRISE, your network, and Oracle databases. Using Administrator to create users and groups, and set permissions. Also contains information on software licensing.

ENTERPRISE Database Reference

The relationships between tables in the database and the contents of each table.

ENTERPRISE User Reference

Functionality that is common to most of the products in the ENTERPRISE suite, including how to access, view, edit and store data.

ENTERPRISE Technical Reference

File formats, as well as antenna and diffraction calculations.

ASSET ACP User Reference

Using ASSET ACP to plan and optimise networks automatically, consider measured data in analysis/optimisation, analyse network performance, identify problematic areas/cells, and related tasks.

ARRAYWIZARD User Reference

Using ARRAYWIZARD to automatically generate pathloss predictions and best server arrays, which gives you instantaneous display of coverage and interference information for pre-selected filters when loaded into ASSET.

ASSET User Reference

Using ASSET, the network planning and analysis tool, to design a range of cellular networks. Includes information on hierarchical network planning, propagation modelling, service and bearer definition, coverage analysis, traffic planning, neighbour planning, measurement data analysis, detailed reporting, analysis arrays and simulation of network performance.

ASSET Technical Reference

Array descriptions and information on some of the algorithms used in ASSET.

ASSET ACP User Reference Guide

Using ASSET ACP to plan and optimise networks automatically, designed as an aid for day-to-day planning. (Optional add-on to ASSET.)

CONNECT User Reference

Using CONNECT, the network transmission and microwave link planning software for full network physical link design and logical link design. Also contains CONNECT-specific reference information.

DATASAFE User Reference

Using DATASAFE, our network configuration tool to implement both small and large scale changes to networks

DIRECT User Reference

Using DIRECT to design telecommunications networks of different network layers. Explains how to plan cellular, PSTN and data networks at a both general and strategic level. Also contains DIRECT-specific reference information.

Financial Analysis User Reference Guide

Using the Financial Analysis module to evaluate and plan for the revenue potential of your network. (Optional add-on to ASSET and ASSET ACP.)

ILSA User Reference Guide

Using ILSA, ASSET's automatic 2g frequency planning tool.

AIRCOM OPTIMA User Reference

Using AIRCOM OPTIMA to view performance data and statistics both with ENTERPRISE and standalone.

RANOPT User Reference

Using RANOPT to efficiently find faults in your network, optimise and validate its performance prior to commercial launch.


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This Guide

Contains Information On

WEBWIZARD User Reference

Using WEBWIZARD to display GIS and report information of network data, including creating layers, regions, nodes, layer types, administering and configuring the system and using the GIS view, explorer and report viewers.

Can You Improve Our User Assistance? We are always trying to improve the online Help and User Reference Guides. If you cannot find the Help you were looking for, need more information, or have any suggestions for improvements, we would be grateful for your feedback. Also, if you are generally satisfied with these resources, we would appreciate any positive feedback. Online Questionnaire

You can help us by completing our brief online questionnaire (http://www.surveymonkey.com/s.aspx?sm=RIRKLcrdvaCzRnUBNx5tcQ_3d_3d). Alternatively, you can contact us directly at [email protected].

Obtaining Support If you have a difficulty you cannot resolve yourself using the online Help or Reference Guides, or you have found a possible fault in the software, you can log a support request. You may also wish to contact us if you want to: Register for a customer web account to access the Support area Obtain further documentation, such as application notes and extra reference information Logging Support Requests Online

To log a support request online:

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1

Go to the AIRCOM website, at www.aircominternational.com.

2

Click the link for Product Support Login.

3

Log in, using your customer web account username and password.

4

In the Technical Support pane, click Online Helpdesk.

5

Click Log New UTS Call.

6

Type the details of your request, and then click Submit.


Contacting us via Telephone or Email

If you wish to contact us directly, here are the contact details of our regional offices: Location

Regional Office

Contact Details

Europe

United Kingdom

Tel : +44 1932 442000 Fax :+44 1932 442005 [email protected]

Middle East, Africa and Central Asia

Belgium

[email protected]

France

[email protected]

Germany

[email protected]

Italy

[email protected]

Sweden

[email protected]

United Arab Emirates

Tel : +971 4 391 2642 Fax :+971 4 391 8141 [email protected]

South Africa

Tel : +27 11 745 1475 Fax : +27 11 465 1517 [email protected]

Americas

Mexico

[email protected]

USA

Tel : +1 214 576 2700 Fax : +1 214 576 2794 [email protected]

Asia and Oceania

Brazil

[email protected]

Singapore

Tel: +65 6372 0548 Fax: +65 6372 0350 [email protected]

China

Tel: +86 2162792779 Fax: +86 2162792855 [email protected]

India

Tel: +91 124 4848200 Fax: +91 124 4517878 [email protected]

When contacting us with a support query, it would help us if you: Give us as much information as possible about the problem and the context in which it occurred State the version and build you are using Have all the details of your query to hand Are logged into the ENTERPRISE application Can send extracts of your data sets if we need them to reproduce your problem


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Obtaining Further Information and Services As well as comprehensive online Help and User Reference Guides and dedicated Product Support, AIRCOM provides: Online Knowledgebase of Articles

If you register for a customer web account, you can view our searchable technical database in the Product Support section of the AIRCOM website. This Knowledgebase contains articles created by our support professionals who have resolved issues for our customers, and is constantly updated, expanded, and refined to ensure that you have access to the very latest information and frequently asked questions. Power Tools

If you register for a customer web account, you can download from a selection of useful power tools, such as file conversion utilities. Latest Copies of the User Reference Guides

If you register for a customer web account, you can download the latest User Reference Guides (PDFs) from our website. If you do this, please check the back of the reference guides for any additions or corrections. Consultancy Services

AIRCOM also provide full radio consultancy services in Network Audits, Business Planning Support, Licence Applications, Radio Network Planning, Telecommunications Research and System Modelling and Propagation Analysis and Modelling. Training

There is a wide variety of courses run by AIRCOM. These courses range from tool training to technology training. For details, contact Competence Development Solutions ([email protected]).

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CHAPTER 2

Automatic Frequency Planning for GSM ILSA is ASSET's automatic frequency planning tool. It enables you to carry out the frequency planning of your 2g network, and analyse the resulting plans. In addition to GSM, ILSA can be used with AMPS, TDMA, PMR, TETRA or iDEN. As an optional add-on to ASSET, ILSA is licensed separately.

Automatic Frequency Planning (ILSA) ILSA (Intelligent Local Search Algorithm) is ASSET's frequency planning tool. Using an advanced heuristic algorithm, incorporating the latest techniques in combinatorial mathematics, ILSA searches for improvements based on user-specified criteria, and greatly speeds up the frequency planning process. Search algorithms specialise in looking for solutions to problems that have too many possible solutions to allow a simple solution. Advanced heuristic search algorithms use the algorithmic equivalent of taking the path that “looks like the best one”. These algorithms use a 'cost' function to determine the most desirable next state, which typically will be the state with the lowest cost. ILSA initialises with a random frequency plan (unless the option is chosen to load the current plan from the database). This means that for any two runs of ILSA, the results may not be the same. Moreover, certain starting frequency plans can allow ILSA to make either more rapid initial improvement or allow a much better plan to be found within a reasonable period of time. ILSA (as its 'Local Search' name implies) reduces the number of options it has for new states derived from a current state. ILSA can give special attention to areas of high cost within the network (analogous to areas of high interference), temporarily ignoring lower cost areas. This allows ILSA to make very rapid initial progress. For example, if ILSA is attempting to plan for a network requiring 60 carrier allocations, with 20 available carriers, and identifies a subset of 10 high cost carrier allocations, then the maximum number of new states that ILSA needs to consider has been reduced from 3.8*1025 to 6.1*1012.

ILSA 7.0 User Reference Guide Automatic Frequency Planning for GSM

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Random changes can be made by ILSA if only low improvement rates are being achieved, or if a dead end is reached. The algorithm monitors its own progress and will behave differently depending on how quickly the cost is decreasing at a given time. This intelligent behaviour enables it to continue finding improvements over long periods of time. The principle behind ILSA's algorithm is that a single number (the cost) measures the effectiveness of any particular frequency plan. The algorithm then tries to minimise the cost over the set of all possible plans. The cost function measures how much interference exists in the network, and what separations have been broken, while taking account of any user-specified 'importance' weightings for different sub-cells.

The Cost Function of the ILSA Algorithm The principle behind the algorithm used in the frequency planning tool is that the effectiveness of any particular frequency plan is measured by a single number (the cost). The algorithm then tries to minimise the cost over the set of all possible frequency plans. The cost function measures how much interference there is in the network, and also allows for the different weights that you may have imposed. For a given frequency plan the value of the cost function is given by the formula:

Where:

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=

The adjacent channel interference caused on allocation i by allocation j (Units: 200*mE or 20,000*km²)

=

The co-channel interference caused on allocation i by allocation j (Units: 200*mE or 20,000*km²)

=

The frequency allocated at allocation i

=

Members of the set of all frequency allocations

=

The retune cost associated with allocation i

=

The fixed or forbidden carrier cost associated with allocation i

=

The separation costs (from equipment, neighbours, exceptions or close separations) between allocations i and j

=

The handover count and intermodulation interference costs associated with allocation i

=

The weighting factor applicable to carrier allocation i


How ILSA Works ILSA (Intelligent Local Search Algorithm) is ASSET's optional frequency planning tool. ILSA uses an extremely advanced heuristic search algorithm, where the latest techniques in combinatorial mathematics evaluate the "penalty cost" of a particular frequency plan and change the frequency allocations to minimise the cost. The algorithm is based on a user-specified Cost Matrix, which associates a set of constraints with variable penalty costs. Constraints with higher associated costs are less likely to be broken, therefore the importance of each constraint should be proportional to its penalty cost. The primary constraints (but not the only ones) in the cost matrix are concerned with a minimum separation between frequencies on: The same cell (intra-cell) The same site but different cell (intra-site) The cell and its neighbours The key objective of ILSA is to minimise the overall 'penalty cost' of the frequency plan. When ILSA is running, it initially concentrates on the high cost areas and therefore makes rapid improvements to the plan. When the rate of progress is reduced, it will try more radical steps to move forward. ILSA constantly searches for improvements and changes are incremental, driven by the penalties you associate with the changes the algorithm can make. By choosing the penalties carefully, you can achieve an effective frequency plan.

The ILSA Process There is a specialist document containing examples of the ILSA process. If you are registered for a customer web account, you can download this document (ILSA2 Application Note) from the Support website. Before starting the ILSA frequency planning process, you may need to verify that improvement is necessary. It may be that the level of improvement needed may not be sufficient to justify a retune, or that the current frequency allocation is close to optimal. In these cases, you may want to employ other optimisation techniques. In any case, if you do choose to use ILSA, it is useful to analyse your existing frequency plan to compare the results with the plan that ILSA produces. To do this, see Analysing a Frequency Plan on page 44. These are the steps you should take when you use ILSA: 1

Analyse any existing plan.

2

Ensure you have the prerequisites for the automatic frequency plan.

3

Set up the filters and other options for ILSA.

4

Load and edit a cost matrix.

5

Run ILSA.

6

Analyse the results to decide whether the plan is acceptable, or an improvement.


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This flow chart shows the process needed to create a good frequency plan with ILSA:

Overview of the ILSA Planning Process

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Creating the Prerequisites for a Frequency Plan There are various inputs to ILSA, some mandatory, and some optional. However, assuming the optional inputs can be produced on a reliable basis, they are recommended in order to provide a realistic frequency plan. You must correctly set up and check the prerequisites before starting to plan using ILSA, because if the inputs are unreliable, then the outputs cannot offer an improvement in network performance. The integrity and accuracy of the information in the Site Database is crucial to an effective plan. The prerequisites for the frequency planning process are: Mandatory Prerequisites

Frequency allocation strategy Site Database with Carrier Layers allocated, and Carriers Required values set for each cell Cost Matrix, with specified carrier separation costs (intra-cell, intra-site) Optional (but recommended) Prerequisites

Interference Table, containing weighted data from a Best Server coverage array and/or Traffic array(s) Neighbours and Exceptions (if appropriate) defined in Site Database You can control the inputs to ILSA through the use of filters, and you can set different filters, cell layers and carrier layers to be considered on a 'plan' or 'read-only' basis, which is useful for a localised re-plan. For example, if you have some newly rolledout sites which need to be planned (amongst existing sites whose frequency allocations need to remain unchanged), you can create filters so that ILSA plans carriers only for the new sites while taking the existing site allocations into account. You can also choose to either create a completely new frequency plan, or use an existing frequency plan as an initial input, and allow ILSA to try to improve it.


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The following sections describe these prerequisites. When you have ensured you have these prerequisites, the next step is to set up ILSA.

Simplified illustration of the inputs into ILSA

About the Frequency Allocation Strategy for ILSA An essential prerequisite for ILSA is that you have correctly defined the appropriate carriers, carrier layers and cell layers to represent your frequency allocation strategy. To check this, ensure that you have already:

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1

Entered the relevant range of frequencies (carriers) into the System Carriers list. For more information, see the ASSET User Reference Guide.

2

Defined the Carriers Layers and Cell Layers you need to represent you network configuration.

3

Assigned the appropriate carriers to the carrier layers (such as BCCH, TCH).

4

Made the relevant associations between the carrier layers and the cell layer(s).

5

Identified 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 (using additional carrier layers with appropriate carriers removed). These might be caused by cross border separation agreements or geographical considerations.


6

Enabled Frequency Hopping and/or DTX in the Site Database, if these are going to be considered by ILSA: 



Frequency Hopping: Follow the steps described in the Configuring Frequency Hopping section in the ASSET User Reference Guide. DTX can be enabled (with an appropriate Voice Activity Factor) on the Cell Config tab in the Site Database

You now need to define the Number of Carriers Required on each cell to be planned.

About the Carriers Required Values Needed for ILSA After you have set up all the necessary carriers, carrier layers, and cell layers for your Frequency Allocation Strategy, you must decide your network capacity configuration. In order to allocate the correct number of carriers in the network, ILSA needs to know the exact carrier requirements for each cell to be planned. Therefore you must ensure that the 'Carriers Required' values in the Site Database are set, otherwise ILSA will not run. There are two ways to set up this essential information for ILSA: 1

Manually for individual cells, by defining the Carriers Required values for each Carrier Layer allocated to the sub-cells, using the Carriers tab in the Site Database. You can also do this for multiple cells using the Global Editor, or you can preset the values in the Templates dialog box. For information on this, see the ENTERPRISE User Reference Guide.

2

Automatically, by using the Static Traffic Analysis tool. For more information, see the ASSET User Reference Guide.

About the Cost Matrix for ILSA ILSA works by finding carrier allocations which minimise the overall cost of the frequency plan. This cost is not a monetary value, but a number that indicates the degree of importance associated with different constraints. The overall 'cost' can consist of: The sum of the cost penalties associated with broken carrier separation constraints (as defined in the Cost Matrix) The amount of interference (area and/or traffic) in the network which will remain with the new plan (as derived from the Interference Table) Using penalty costs helps you determine when you can stop iterating the frequency plan – that is, when your costs have become stable. A Cost Matrix defines the constraints within which ILSA will work and the penalties associated with breaking those constraints.


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This picture shows an example:

Example Cost Matrix

You can create several different cost matrices, and load them at various times for comparison purposes. For more information on defining a Cost Matrix, see Creating and Editing a Cost Matrix on page 29.

About the Interference Table for ILSA An interference table (sometimes known as an interference matrix) can calculate the interference for any cell-pair combination for which there are overlapping predictions. ASSET provides an Interference Table Wizard that can generate its results from either: Coverage area data and (optionally) traffic data - or Measurement data (traffic data only) - or A combination of both For information on creating, loading, saving and viewing interference tables, see About the Interference Table for GSM in the ASSET User Reference Guide.

About the Neighbour Lists and Exceptions for ILSA Neighbours

When ILSA is experimenting with different frequency allocations, it can take into account the neighbour relationships defined in the network. This should help to produce a better quality frequency plan. You can import the neighbour relationships from your real network into the Site Database, or generate neighbour lists automatically using the Neighbour wizard, or manually add or remove neighbours.

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Exceptions

ILSA uses an interference table to assess whether a particular frequency re-use between two cells is good or bad. However, the interference table is created from predictions that may not always match reality. To prevent ILSA using a certain frequency re-use, you can use exceptions to forbid a particular frequency re-use between two cells. Exception relationships between cells can be set manually on the Exceptions tab of the Site Database. For full information on setting the above options in the Site Database, see the ASSET User Reference Guide.

About the Propagation Model, Predictions and Best Server Array for ILSA After you have defined or checked the other prerequisites for ILSA, you may wish to consider and check the following optional (but recommended) inputs: Item

Purpose

Prerequisite

Propagation model

Predicts the coverage of cells, taking into account the RF parameters stored in the site database and the mapping data

The propagation model should be accurate.

Required for array creation, including the Best Server array

Predictions have to be made for of all the sites that will be included in the plan. They must be at an appropriate map data pixel resolution and radius.

Predictions

However, see the next section if you want to use ILSA but are unsure of your model's accuracy.

Use the Best Server array (and Service Area array) to check the coverage pattern. This may indicate any problems which need to be corrected in the Site Database. Best Server array

Needed for the generation of some of the optional inputs to ILSA, including: Neighbours Traffic rasters Interference Tables

The array should be generated at the same resolution as the predictions, over an area that covers all of the service areas of the cells being planned. It is therefore important that the Filter used to create the array includes all the sites to be planned.

Using ILSA with an Inaccurate Propagation Model

If you have little or no confidence in your propagation model, for example because model tuning is still being performed, you can still use ILSA to develop a frequency plan by: Manually entering the carriers required in the Site Database (you can also use Global Editor or pre-set in Template) Manually entering the neighbour lists (by importing directly into the Site Database) Not using the interference table, and allowing ILSA to work solely on separation constraints that you have entered into the cost matrix This method only uses carrier separation constraints to produce a frequency plan, and totally ignores any of the coverage or interference functionality in ASSET. ILSA 7.0 User Reference Guide Automatic Frequency Planning for GSM

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How ILSA Works with an Existing Frequency Plan You can use an existing frequency plan as a major input into ILSA. Such a plan can either exist in the Site Database, or can be imported separately when setting up ILSA. In the case of an existing plan, ILSA can adopt the currently allocated carriers as the initial state of the frequency plan. The ways in which ILSA will arrive at an updated frequency plan will depend on: The planning option chosen in the ILSA Frequency Planner dialog box Which Filters and Cell Layers are used How the Plan or Read-Only options for Filters and Cell Layers are defined How the Cost Matrix is set up, including how it deals with any carriers defined as Fixed or Forbidden

Initialising the ILSA Frequency Plan When you have checked or generated all the prerequisites, you are ready to initialise your ILSA frequency plan. To do this: It is wise to perform a Commit All on the Site Database before you initialise ILSA. If you later choose to Apply the Carriers from the new plan, this would enable you to perform a Restore All to return to the previous situation, if necessary. 1

From the Tools menu, point to GSM Planners and click ILSA Frequency Planner. The following dialog box appears:

If you change the planning data that you want to include in the frequency plan, any existing data in ILSA is overwritten.

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2

In the dialog box that appears, select which planning data you want to use. In the Network pane: Choose

To

Then

Data from memory

Select existing data

Follow steps 3 - 6

File, then browse for a file

Use information from a file that you have previously exported from ENTERPRISE

Follow steps 4 - 6

You can only use ASSET XML network files.

3

If you selected the Data From Memory option in the Network pane, select the filters that you want to use by clicking Import Filters then: 



In the Import Filters wizard that appears, select the folder(s) that contains the filters that are to be considered in your plan, then click Next. Select the checkboxes for the filters that are to be considered. When you plan, the simplest situation is that you use one or more filters, and plan all the included sites. However, you can also use multiple filters so that you assign some of the sites with Plan status and some with Read-Only status. These options are described in Defining Groups of Cells as Plan or Read-Only on page 28. In this case, you may need to use the arrows to reorder the filters in terms of priority. Only a single planning status (plan, read-only, ignore) can be assigned to a cell. Therefore, in cases where a cell might exist in more than one filter, the filter priority is important in deciding which status applies to such a cell. For example, if a cell happens to exist in two filters, one set as Read-Only and the other as Plan, and the former filter is set with a higher priority, then the cell will be considered as read-only for the plan. Click Next.





Select the cell layers you want to consider from the list shown, then click Next. Fine tune the cell layer and filter combination you want to import then click Finish.

4

In the Interference pane, you can select to use the Interference Table in memory (this is not compulsory), or use data from a saved file.

5

In the Handover Counts pane, if you want to use handover counts in the plan, you can select the File option and browse to your file. You can either create this file or import it from AIRCOM OPTIMA. For information on the file format, see the ENTERPRISE Technical Reference Guide.

6

Click the Initialise button. The data you have specified is then loaded into ILSA, a default cost matrix is created and the ILSA Frequency Planning dialog box appears.


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About the ILSA Frequency Planner Dialog Box The ILSA Frequency Planner dialog box comprises a set of menu options which enable you to customise various parameters and constraints for your frequency plan. It also allows you to view the progress of the plan. The following table describes the three panes which appear on the dialog box: Pane

Description

Plan

ILSA can be used to create a completely new frequency plan, or it can take into account an existing plan and try to improve it. The options are: Use Current Plan loads the carrier assignments of the current plan that exists in the Site Database. This may retain a larger number of the original channel allocations and will minimise the number of changes that the frequency planner makes. Choose this option when adding a small number of new sites to an existing network.

– or – Create New Plan starts ILSA planning with an entirely random frequency plan. This is an easy way to remove the constraints of a frequency plan but will take slightly longer to reach an initial acceptable result. Choose this option when: Creating a frequency plan for a new network Carrying out a complete regional retune Implementing a new technique, such as frequency hopping Plan Status

When ILSA is running, this pane will display various information about the plan, its status, time started, what carriers to plan, the initial cost of the plan, the current cost and the iteration.

Interference

When ILSA is running, this pane indicates the average and worst interference in the plan, in terms of coverage area and/or traffic.

About the ILSA File Menu These options are useful so that you can export and import different frequency plans to the project, enabling you to easily compare old and new plans. Menu Option

Enables you

Save Network

To save the complete network. This is equivalent to a normal XML export of the project, except that Templates are not exported.

Export Assignments

To export the current carrier assignments to an XML file.

Import Assignments

To import a previous frequency plan from a saved plan (XML).

Close

To close the ILSA Frequency Planner dialog box. If ILSA has been run, you will receive a warning that any unsaved planning will be lost.

About the ILSA View Menu These options enable you to set up a Plan List for the frequency plan, as well as viewing the latest assignments and progress graph. ILSA must be paused to enable these options.

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Menu Option

Enables you

Plan List

To edit and view the Filter/Cell Layer/Carrier Layer Plan Status (e.g. Plan or Read-Only). For a full description, see Defining Groups of Cells as Plan or Read-Only on page 28.

Assignments

To view the current Carrier Assignments.

Graph

To view the ILSA Cost/Interference progress graph.


About the ILSA Cost Matrix Menu These options enable you to Load, Save or Edit a Cost Matrix. This allows you to have more than one to choose from. The cost matrix which initially gets loaded when you initialise your plan is always the original default matrix, therefore if you wish to load a saved matrix (or create a new one), you must do so at this stage. Menu Option

Enables you

Load

To load a Cost Matrix from a saved .cmf file.

Save

To save the Cost Matrix to a .cmf file format.

Edit

To edit the Cost Matrix (or to create a new one).

Saved Cost Matrices can only be loaded into the same project from which they were produced. For a full description of these options, see Creating and Editing a Cost Matrix on page 29.

About the ILSA Tools Menu These options enable you to Re-Initialise ILSA, Apply the frequency plan to the database, or define customised options. Menu Option

Enables you

Initialise

To Re-Initialise the inputs to ILSA (such as which Filters to include and which Interference Table to use). For a full description, see Initialising the ILSA Frequency Plan on page 24. It performs the same function as closing ILSA and re-starting it through the Tools/GSM Planners menu. Using this option will therefore overwrite any existing ILSA settings.

Apply to Database

To Apply the latest Carrier Assignments (made by ILSA) to the Site Database. This will update the Carriers tab on the Sub-cells with the new Frequency Plan (depending on the options set up in the Plan List), allowing you to analyse the plan by producing arrays and reports. For more information, see Applying an ILSA Frequency Plan to the Site Database on page 42. It is a good idea to perform a Commit All on the Site Database before you Apply the Carriers from ILSA. This would enable you to perform a Restore All to return to the previous situation, if necessary.

Options

To set up specific options. The ILSA Options dialog box comprises two tabs: one with general options such as Auto Save and Refresh Rate; the other with various planning options such as weighting Interference by Area and/or by Traffic. For a full description, see Setting the Planning Options for ILSA on page 35.

About the ILSA Help Menu This gives direct access to the Help topics for ILSA. You can also use the F1 key from any window to obtain context-sensitive Help.


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Defining Groups of Cells as Plan or Read-Only When you are setting up an ILSA plan, you may need to define different groups of cells in the network to be planned, read-only or ignored. You can achieve this by specifying how filter, cell layer and carrier layer combinations are to be considered within the frequency plan. See Example of Using ILSA for a Localised Re-plan on page 39 for an example of how the flexibility of the Plan List can be useful. To do this: 1

Ensure you have initialised ILSA, and from the ILSA View menu, click Plan List. The Plan List dialog box appears. Here is an example:

2

In the Plan List dialog box, in the Status column for each combination: Select

If you want ILSA to

Plan

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

Not plan 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 ILSA when planning other carrier allocations. For example, it may be important to take into account frequency allocations in neighbouring regions. In this case, the filter/cell layer/carrier layer combinations describing the neighbouring regions should be assigned Read Only.

Ignore

Ignore sites satisfying the filter/cell layer/carrier layer criteria. Click here for a tip on when the ignore option may be useful.

ll

Only a single planning status (plan, read-only, ignore) can be assigned to a site. Therefore, in cases where a site might exist in more than one filter, the filter priority is important in deciding which status applies to such a site. If this is the case, ensure you have ordered the filters in terms of priority, as described in Initialising the ILSA Frequency Plan on page 24.

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When planning, the complexity of the filter/cell layer combinations can severely impact the speed at which a solution is reached. If due to the nature of the frequency banding technique chosen, you can disregard a particular cell layer since it has no possible impact on the others, it is advisable to ignore the layer completely. This would happen when considering a dual band network and only planning the 900MHz layer. In this case the 900MHz layer and 1800MHz layer can be considered independent of one another. 3

Now you are ready to edit the cost matrix.

Creating and Editing a Cost Matrix For a definition of the cost matrix, see About the Cost Matrix for ILSA on page 21. As part of the ILSA initialisation process, the default cost matrix is automatically loaded. This is always the original default matrix, therefore if you wish to create and save your own customised matrix (or load a saved matrix), you must do so at this stage. You can create several different cost matrices, and load them at various times for comparison purposes. To edit an existing saved cost matrix, follow the steps described in Loading a Cost Matrix on page 34. To create a new cost matrix: 1

From the ILSA Cost Matrix menu, click Edit to open the original default cost matrix.

2

Follow the options for each of the folders in the Cost Matrix Editor, as described in the following sections.

After you have created or edited a customised cost matrix, ensure that you save it for future use.

Tips for Setting Penalty Costs In most cases, you will need to modify the default values in the Cost Matrix for ILSA, in order to customise the penalty cost weightings to derive a frequency plan suitable for your network. The values that you choose should depend on: Frequency re-use availability Separation constraint values Number of neighbours in the plan Interference base (area, traffic or combination) Amount of traffic (if interference minimisation is traffic based) Cell sizes Interference table size (depends on prediction radius and used interference table creation method)


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Usually when running ILSA, the first priority is to remove the separation constraints. To achieve this, the separation costs must be adequately high. If equipment and neighbour separation costs are not high enough compared with the interference costs, the separations are not completely removed during the frequency planning process. Frequency planning is an iterative process and it is recommended that you study the effect of different cost settings in order to determine the optimal cost values for your purposes.

Carrier Costs and Carrier Layer Costs When you are adding or editing a cost matrix, you can edit the Carrier Costs and Carrier Layer Costs, by clicking the appropriate folder. Carrier Costs

You can set the penalty costs associated with any carriers of particular cells which have been set as Forbidden or Fixed in the Site Database. Only such cells will appear in this window. This picture shows an example:

Example Cost Matrix

Theoretically, Fixed or Forbidden carriers can still be affected (changed) by ILSA. These relate to the penalty costs of ILSA either de-allocating a Fixed carrier or allocating a Forbidden carrier. They should therefore be high values. However, if you wish to explicitly prohibit their allocation, you can select the option described in Setting the Planning Options for ILSA on page 35. Carrier Layer Costs

You can assign a weighting to any of the cell layer/carrier layer combinations (for example you may wish to set a weight of 2 for the BCCH layer, compared to 1 for TCH). Weightings can be used to deter ILSA from breaking constraints on higher weighted layers. To prevent ILSA from retuning allocated (whether fixed or otherwise) carriers on a carrier layer, in the Allow Retune column, deselect the checkbox. To allow ILSA to retune any allocated carriers, in the Allow Retune column select the checkbox and enter a cost. If you enter a high cost, ILSA will be deterred from changing the allocated carriers unless it must do so to obtain a plan with low interference.

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Equipment Costs When you are adding or editing a cost matrix, you can edit the Equipment Costs, by clicking the appropriate folder. These costs relate to Intra-Site, Intra-Cell and Cell Equipment carrier separation constraints. You can set generic separation constraints and associated penalty costs for the sites, cells and equipment in your network. These will be listed for every combination of Cell Layers and Carrier Layers in your network that are to be included in your plan. Under the Equipment column, there are rows stating Site or Cell. For each one, respectively, you can set: A minimum separation constraint (and associated penalty cost) between carriers on the same SITE A minimum separation constraint (and associated penalty cost) between carriers on the same CELL Optionally, you can also set preferred separation constraints, in order to 'fine-tune' the cost matrix (if you do not wish to do this, set the preferred constraints to the same value as the minimum). Example of Separation Constraints:

If the intra-cell separation constraints and associated costs (minimum and preferred) are set as: Min Separation

Min Cost

Pref Separation

Pref Cost

2

1000

4

100

Then the associated penalty costs for any intra-cell allocations made by ILSA's plan would be: Actual Separation achieved by ILSA

Penalty Cost

4 + (preferred)

0

3

100

2

(minimum)

200

1

1000

0

2000

As can be seen, the penalty cost values are summed for each reduction in separation. If only the preferred separation is broken, only the preferred cost is summed. If the minimum and preferred separations are broken, only the minimum cost is summed. Cell Equipment

You can also set intra-cell separation constraints and costs on the basis of the types of Cell Equipment used on each cell. If a cell has cell equipment assigned to it, the separation costs defined for that cell equipment will take precedence over the intra-cell separation costs (defined against the 'Cell' entry). If, on the other hand, no cell equipment is assigned to a cell, the intracell separation costs will be applied. ILSA 7.0 User Reference Guide Automatic Frequency Planning for GSM

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For more information about adding cell equipment, see the ENTERPRISE User Reference Guide.

Neighbour Costs and Exception Costs When you are adding or editing a cost matrix, you can edit the Neighbour Costs or Exception Costs, by clicking the appropriate folder. Neighbour Costs

You can set the penalty costs associated with the minimum separations or preferred separations for cells which are neighbours, and also 2nd order neighbours. These will be listed for every combination of Cell Layers and Carrier Layers in your network that are to be included in your plan. Exception Costs

You can set the penalty costs associated with the minimum separations or preferred separations for cells which have been defined as Exceptions in the Site Database. Only such cells will appear in this window. For full information on setting the above options in the Site Database, see the ASSET User Reference Guide.

Filter Priorities, Handover Counts and Intermodulation Costs When you are adding or editing a cost matrix, you can edit the Filter Priorities or Handover Count or Intermodulation Costs, by clicking the appropriate folder. Filter Priorities

You can view the filter(s) that you are planning for. When using multiple filters, edit the priority column so that if a site is present in more than one filter, the settings are taken from the filter with the highest priority value. Handover Count Costs

A handover counts contain the number of times a handover occurs between any two cells. For information on the input file, see Initialising the ILSA Frequency Plan on page 24. If you wish to Use Handover Counts, select the checkbox and then either: Select Auto Scale to set the scale factor to normalise the handover count to a similar level to all the other costs Enter the Scale factor manually. For example, a factor of 2 will cause ILSA to make the handover count costs twice as important as other costs.

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Intermodulation Interference Costs

You can set costs for 2nd order and 3rd order intermodulations. You can also enter an uplink weighting to be applied to intermodulations that involve uplink frequencies (which cause less significant interference than downlink frequencies). In order to take intermodulation into account, ILSA needs to know the absolute frequencies represented by the carriers. For more information on this, see the ASSET User Reference Guide.

Separation Costs (grid) When you are adding or editing a cost matrix, you can edit the Separation Costs, by clicking the appropriate folder. This will display a movable grid which lists every sub-cell for every combination of Cell Layers and Carrier Layers in your network that are to be included in your plan. You can use this grid to set specific separation costs between sub-cells or between separate carrier layers within a sub-cell. This enables you to allow for known troublespots in the network. Separation Costs work in a similar way to the Exception costs, except that the latter must already be set in the Site Database, whereas the former can be set up in the Cost Matrix independently. There are 3 tabs available at the bottom of the pane: Separation 0 (co-channel), 1 (adjacent channel) and 2. You can set default costs for each of these tabs, which can be overridden in the main grid. There is also a Search button which enables you to find any cell relationship combination in the plan. Costs should change according to the importance that you have assigned to different separations in the network, and to the constraints that you have chosen. The cost of a cell co-channel separation should be greater than the cost of a site co-channel separation, which in turn, is greater than the cost of a neighbour co-channel separation, and so on. When ILSA runs, any Separation Costs set in the grid will always be additional to any of the other costs set up in the cost matrix. Editing Multiple Separation Costs

To enter common cost values for multiple cell relationship combinations: Click and drag the mouse over the required values in the grid, then simply enter the new value. To edit, copy or reset cost values for multiple cell relationship combinations: Click and drag the mouse over the required values in the grid, then right-click, and from the menu that appears, click Set to Default or Copy. If you chose Copy, you can then paste the data onto new combinations. For all costs and separations you can simply copy and paste data by selecting with the mouse, and using the normal keyboard methods to copy and paste the data elsewhere.


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If you use the Reset to Default button to reset all the values to the defaults, this will remove any changed values you may have inserted in the grid.

Saving a Cost Matrix To save a cost matrix 1

From the ILSA Cost Matrix menu, click Save.

2

Browse to the folder where you want to save the plan and enter a name for the plan.

3

Click OK. The plan is saved as a .cmf file.

Saved Cost Matrices can only be loaded into the same project from which they were produced.

Loading a Cost Matrix To load a saved cost matrix 1

From the ILSA Cost Matrix menu, click Load.

2

Browse to the folder where you have saved the plan and select the appropriate .cmf file.

3

Click Open.

The cost matrix is now loaded, and can be viewed and edited, and, if necessary, subsequently saved as the same or a different file.

Setting the Display Options for ILSA To set the options for ILSA's progress display : 1

From the ILSA Tools menu, click Options.

2

On the General tab, you can select: 







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Graph X-Axis. Panel Refresh Rate. The refresh rate simply determines how quickly the Plan Status panel updates while the plan is running. A fast rate updates the cost of the plan for every improvement (cost reduction) made, a slower rate updates after a series of improvements. 5 is the normal default. Log results in Message Log every minute. Auto Save the plan periodically (with updated carrier assignments) as an XML file, setting a time interval and path name.


Setting the Planning Options for ILSA To set the special options for ILSA's planning features: 1

From the ILSA Tools menu, click Options.

2

On the Planning Features tab, you can set the following options: Select

When

Use Frequency Hopping Diversity Gain

Frequency hopping is enabled on your sub-cells and you want ILSA to apply a gain to the interference costs incurred by carrier assignments to these sub-cells during the plan optimisation.

Aggregate carriers required under Site hopping

For Site hopping, you wish ILSA to aggregate the carrier requirement of each subcell across all sub-cells on the site (e.g. if requirements for a 3-cell site are 3, 4, 3, ILSA would allocate 10 carriers for each cell). This is typically used in nominal planning when Traffic Analysis has been used to set carrier requirements. If you do not select this, ILSA presumes that the Site hopping sub-cells have already had their carrier requirements set. This is typically used when ASSET is populated with data from a live network.

Use Antenna Hopping Gain

Antenna hopping is enabled on your sub-cells and you want ILSA to consider this during the plan optimisation.

Use DTX Load Factors as set in the Site Database

You want to reduce the interference caused by sub-cells with DTX enabled. The interference weighting of such cells is multiplied by the Voice Activity Factor set on the Cell Config tab in the Site Database. This means ILSA plans allocations more carefully for non-DTX cells. BCCH carrier allocations are always considered as non-DTX.

Consider Intermodulation Interference

You want ILSA to take intermodulation interference between carriers into account during the plan optimisation. You can specify tolerance values in order to determine the levels of interference that can be ignored. Frequency Bands must have been enabled on the General tab of the Preferences dialog box, found under the File menu option.

Use Group Planning

You want ILSA to allocate frequencies according to a frequency re-use pattern, when group planning has been enabled on the carrier layer. ILSA can only maintain group planning patterns on a cell basis, not on a site basis. For example, at the cell level, all planned carriers will belong to a single group such as A1 or B1, but one of these groups may also be allocated to another cell on the same site.

Exclude Forbidden Carriers

You want to completely prohibit the allocation of forbidden carriers. ILSA normally assigns forbidden carriers a very high cost, meaning they are very unlikely to be used within its output frequency plan. But, by selecting this checkbox, you can ensure that ILSA totally prohibits their allocation.

3

If you have created an interference table as an input to ILSA, you can also choose how ILSA should minimise the interference during its optimisation plan, as explained in the following section.


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Choosing ILSA's Interference Minimisation Criteria (Area or Traffic) In relation to the general planning options for ILSA, you can also set interference minimisation criteria. These options are only relevant if you have created or loaded an Interference Table. An Interference Table is not a mandatory input into ILSA, but it is recommended if you have some confidence in your coverage and/or traffic arrays. This table describes the options available if you want ILSA to also minimise by interference during its frequency planning. Option

Description

Minimise Interference by Traffic

This will be the amount of traffic (mE) affected between any two cells due to co- or adjacent carrier allocation. Use this option if you have reasonable or high confidence in the traffic statistics that you used to generate the interference table. ILSA will pay more attention to reducing interference in the high traffic areas as it formulates the frequency plan. For this option, the interference table must have included a traffic raster.

Minimise Interference by Area

This will be the amount of coverage area (km²) affected between any two cells due to co- or adjacent carrier allocation. Use this option if you have little or no confidence in the traffic statistics that you used to generate the interference table.

Minimise Interference by Combination (both traffic and area)

This can be a combination of traffic and coverage area affected between any two cells due to co- or adjacent carrier allocation. The percentage ratio that you specify will determine which factor is dominant. Use this option if you have only partial confidence in the traffic statistics, or you wish to bias the plan towards the urban areas (which should contain more traffic) while maintaining reasonable quality across the network For this option, the interference table must have included a traffic raster.

For the purposes of normalisation, ILSA multiplies any area (km²) values by a factor of 100, to bring make them compatible with any traffic (mE) values, and subsequently multiplies both area and traffic values by a factor of 200, to bring make them compatible with Carrier Separation Costs set up by the user in the Cost Matrix. This enables ILSA to minimise costs on a like-for-like basis, but also allows the user to customise the Cost Matrix to determine the overall weightings for the frequency plan.

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Running ILSA To start running ILSA: 1

2

Ensure you have: 

Initialised ILSA



Set up the options



Defined the filter/cell layer/carrier layer combinations to be considered



Edited the cost matrix

In the ILSA Frequency Planning dialog box, select: 



3

Use Current Plan to load the initial carrier assignments of the current plan, for example, when adding a small number of new sites to an existing network. This may retain a larger number of the original channel allocations. – or – Create New Plan to start ILSA planning with an entirely random frequency plan, for example, when planning for a new network or implementing a new technique, such as frequency hopping.

Start planning by clicking the Start button. If you have a large cost matrix, leave ILSA running for several hours at a time. However, remember that the rate of improvement decreases with time – so large improvements are made within a relatively short period of time and only modest (but potentially beneficial) improvements are made over many hours.

4

When you decide to stop ILSA running - that is, when a considerable period of time has elapsed without much improvement - click the Stop button. ILSA will only stop itself when the cost of the plan reaches zero. This is really only possible when the planning constraints were very easy to satisfy and is unlikely in a real network. An example might be planning a small network of 10 sites with a full GSM band of carriers!

5

Now you can analyse the results. The Online Help for ASSET contains a Troubleshooting ILSA section.


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What Happens When ILSA Is Running? When you click Start to begin planning, ILSA: Begins initialising, making first-pass frequency allocations to all sub-cells Tries to meet all the rules that have been created in the cost matrix, and simultaneously tries to reduce the average level of interference per carrier Eventually displays Finished with Zero Cost in the Status box indicating that a cost of 0 has been achieved with the current plan Shows the start time, plan ID and number of carriers to plan, initial cost of the plan, cost of the current best plan, the number of completed iterations (screen refreshes not algorithm loops), the average interference per TRX and the worst case interference for a carrier.

The Frequency Planning dialog box

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Example of Using ILSA for a Localised Re-plan If you want to plan frequency allocations for a new site within an existing network, 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 network design to be read-only To achieve this localised re-plan using ILSA, you would do the following: 1

Create three dynamic filters based on polygons with meaningful names, such as AreaForNewSite, BorderAroundNewSite and RestOfPlan.

2

In the ILSA Import Filters wizard, choose to import these three filters and, on the second page of the wizard, order the priority of the filters so AreaForNewSite is at the top and RestOfPlan is at the bottom.

3

From the ILSA View menu, click Plan List and set the cell layer/carrier layer combinations AreaForNewSite and BorderAroundNewSite filters to Plan, and for the RestOfPlan filter to Read Only.

4

In the Carrier Layer Costs folder, select the Allow Retune checkbox for the BorderAroundNewSite filter and add an associated cost of performing the retune. The cost should be high enough to ensure that carriers are re-planned in the border region only if a significant improvement is made - the value really depends on how critical it is to you that the number of changes should be minimised – the more important, the higher the cost. It may take a couple of iterations (without Applying the changes to the database) before the optimal retune cost is found. The cell layer/carrier layer combinations for the RestofPlan filter are not present because you are not planning for it.


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Reviewing ILSA’s Results You can review the latest results of the ILSA frequency plan by: Viewing a graph of cost and interference – you can do this while ILSA is running Viewing the latest carrier assignments and statistics - to do this you need to pause ILSA

Viewing, Saving and Printing the ILSA Graph To view the ILSA Cost/Interference graph while ILSA is running: From the View menu, click Graph. The graph appears showing the cost of the current best plan (in red), the average interference (in green) and the worst interference (in blue). For example:

To save a copy of the graph while the plan is running: 1

In the ILSA graph, click the Snapshot button.

2

Browse to a folder where you want to save the snapshot graph.

3

Choose the type of file (*.bmp or *.jpg).

4

Enter a filename.

5

Click Save.

To print the ILSA Cost/Interference graph:

Page 40

1

In the ILSA graph, click the Print button.

2

In the dialog box that appears, choose the position of the graph on the page or set up any margins, and choose the size required.

3

Click OK.

4

In the dialog box that appears next, select the appropriate printer then click OK to print the graph.


Viewing ILSA's Carrier Assignments and Statistics When ILSA has been stopped, you can view the allocations that have been made in the current best plan. From the ILSA View menu, click Assignments. This dialog box appears:

The Carrier Assignments dialog box displays the: 



Carrier statistics, that is, the number of times each frequency is allocated, and the minimum re-use distance between each site using that frequency Cell statistics, in terms of the interference on each allocation that is made.

What are Acceptable Statistics in an ILSA Plan? When you view the carrier assignments made by ILSA's frequency plan, carrier statistics and cell statistics are displayed. These tips may help you decide whether the statistics are acceptable: If only alternate carriers have been assigned even though you have a contiguous band of carriers, this indicates that the adjacent interference is more dominant than co-channel, which is incorrect. The most common reason for this is that the C/I adjacent offset in the Array Settings dialog box may have the wrong sign. It should be negative (the default for this is –18db). You should not expect a fixed carrier allocation strategy, due to the heuristic algorithm, but, typically, ILSA should produce a fairly uniform distribution of carrier assignments. Clicking the interference column heading enables you to order the assignments to show which caused the most and least cost to the plan. The interference value is the summation of all the associated costs of making that assignment. If this value is less than the minimum separation/retune cost then this is purely an interference cost. If a large number of assignments have high costs then the constraints are proving difficult for ILSA to satisfy. For example, it may have a small range of carriers to choose from, or the separation requirements for the sites, cells or neighbours may be too strict. ILSA 7.0 User Reference Guide Automatic Frequency Planning for GSM

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For multiple second order neighbour paths, a set of the second order neighbours is maintained so that the cost is not experienced more than once. If the resultant cost of the plan is less than the minimum separation cost, that indicates that all the separation constraints were satisfied and therefore the remaining costs of the plan are only based on interference. If this is the case, the assignments might produce a good frequency plan. The statistics are very useful to assess the plan generally, but it is crucial that you use the normal methods in ASSET to analyse and judge the effectiveness of the frequency plan, using the Interference Arrays and Reports. To do this, you must first Apply the Plan to the Database.

Applying an ILSA Frequency Plan to the Site Database It is wise to perform a Commit All on the Site Database before you Apply the Carriers from ILSA. This would enable you to perform a Restore All to return to the previous situation, if necessary. When you view the carrier assignments in the Carrier Assignments dialog box, you can judge whether the results and statistics of ILSA's frequency plan are acceptable or not: If the results are unacceptable to you, for example if BCCH carriers are experiencing worse interference than TCH carriers, then continue planning. If the results are acceptable to you, you can close the dialog box and Apply the frequency plan to the database. To do this: From the ILSA Tools menu, click Apply to Database. This action is immediate, with no warning message. That is why the 'Commit All' mentioned above is important. This will update the Carriers tab on the Sub-cells with the new Frequency Plan (depending on the options set up in the Plan List), allowing you to analyse the plan using arrays and reports. You can also Apply the plan then restart planning. This can improve the quality of the plan, due to a random element within the ILSA algorithm. When you have Applied a plan to the database, perform the plan analysis using the normal methods to verify that an improvement has been made. For information on this, see Analysing a Frequency Plan on page 44. You can also use ILSA's Import Assignments to Apply other plans to the database (using the same procedure as above), in order to carry out comparative analyses between plans. If you have the BCCH prerequisite rule activated, after you Apply the changes, the following message will be displayed: "BCCH allocation prerequisite may have been violated. Use Site/Node Reporter to check for any violations."

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For more information, see the ASSET User Reference Guide.

Exporting Assignments You can export carrier assignments from ILSA to an XML file, even without Applying the plan to the database. You may also want to analyse the carrier assignments that ILSA has made in other software programs. Only data that is applicable to the frequency plan will be exported. To export carrier assignments: 1

From the File menu on the ILSA Frequency Planning dialog box, click Export Assignments.

2

Enter a filename and click OK.

The carrier assignments determined by ILSA are exported to an XML file, enabling you to import them at a later stage, or analyse them in other tools.

Importing Assignments You can import carrier assignments from previous frequency plans. To import carrier assignments: 1

From the File menu on the ILSA Frequency Planning dialog box, click Import Assignments.

2

Browse to the XML file you wish to import.

3

Click OK.

You can then view the imported Carrier Assignments in ILSA, and then either: Run ILSA using the imported plan as a starting point - or Apply the imported plan to the Site Database for Analysis purposes


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Importing Frequency Plans There are various ways to import frequency allocations into the Site Database. For information on this, see the ENTERPRISE User Reference Guide.

Analysing a Frequency Plan You can use ASSET to analyse an existing frequency plan, or to analyse any nominal plan. You can analyse a variety of plans by importing each one into the Site Database. You can also export plans generated by ILSA, and then save them for future analysis and comparisons.

Example of Worst Interferer array including pixel-specific information

Page 44


How to Analyse a Frequency Plan Here are the main steps for analysing an existing or nominal frequency plan: 1

Ensure the current or nominal frequency allocations have been set up or imported in the Site Database.

2

From the Arrays menu, click Array Settings. On the Coverage/Interference tab, choose Co-channel or Adjacent channel or both.

3

Open the Map View window at the desired location.

4

Create one or more interference array(s). You can choose from: 

Worst Interferer



Total Interference



Worst Connection



Average Connection

Descriptions of these array types are given in the ASSET Technical Reference Guide. If you are using a frequency hopping network, choose a connection type array, since these are designed to consider hopping carriers. 5

Display the array(s) on the Map View.

6

After analysing the array(s) visually (and plotting the resulting view, if desired), you can now analyse the plan statistically, by producing an Interference Statistics report. The report gives details of the proportion of interference better and worse than the chosen interference threshold, as well as a breakdown by clutter type and by cell. The Total Covered Area in the report is the area of the Best Server array down to the chosen coverage level. It is also possible to confine the statistics within specified user polygons, for example enclosing urban areas only.

7

Use the Interactive Frequency Analysis to generate a comprehensive report which can analyse and fine-tune the frequency plan based on the Interference Table, Neighbours, Site/Cell Separations and Exceptions.

8

Use the Frequency Plan Reporter to generate a simple report which lists allocations which do not meet specified carrier separation constraints.

9

Display the Frequency Re-use on the Map view, using the Cell Info option under the Data Types list.

It is always necessary to create an Interference Array before generating an Interference Report. This is because the reports always extract their data from the interference array currently in memory. Therefore, after making any changes in the network, you should always carry out both steps consecutively. For more detailed information on the above processes and features, see the ASSET User Reference Guide. ILSA 7.0 User Reference Guide Automatic Frequency Planning for GSM

Page 45

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Index A Algorithms ILSA cost function • 16 Analysis frequency plans • 40, 41, 42, 43, 44 Assignments, carriers • 15, 40, 41, 43, 44

C Carriers assignments • 15, 40, 41, 43, 44 Cost Matrix for ILSA • 17, 21, 27, 29, 34

F Frequency Planning analysing plans • 40, 41, 42, 43, 44 automatically using ILSA • 15 Cost Matrix for ILSA • 17, 21, 27, 29, 34 importing and exporting plans • 42, 43, 44 prerequisites for ILSA • 19

H Handover counts used in ILSA • 32

I ILSA about • 15, 17 , 19 analysing plans • 40, 41, 42, 43, 44 cost function • 16 Cost Matrix • 17, 27, 29, 34 interference tables • 19, 24 prerequisites • 19 running • 37 viewing results • 40 Intermodulation frequency bands • 32, 35 in ILSA • 32, 35

P Planning frequency • 15, 44

ILSA 7.0 User Reference Guide Index

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ILSA User Reference Guide

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