RA D I O N E T W O R K P L A N N I N G S O LU T I O N S
3-Day ASSET Enterprise Training Course ZTE P&O DEPARTMENT
ASSET V7 3-Day User Training Course Outline 9.00 – 10.30
Break 11.00 – 12.15
Lunch 13.30 – 15.00
Break 15.30 – 17.00
Day 1 Introduction & Overview of Tool Key Concepts Starting a new Project Using the GIS
Day 2 Working with Flags & Filters Planning Neighbours
Day 3 Working with Layered Networks: Modelling Dual-band Networks Dual-band design exercise.
Setting up for Planning. Importing Antennas Defining Models Defining Cell Radii Defining Site Templates Adding Network Elements
Traffic Planning Carrier Requirement Calculation Interference Tables
Working with Antenna Slots Printing & Plotting Report Generation
Predicting Coverage Displaying/Analysing Coverage Creating Polygons
Frequency Planning Analysing Frequency Plans
Fixed link network planning with ASSET
Network Design Exercise: Coverage Planning.
Frequency Planning Exercise
Test Mobile Analysis
ASSET V 7.0 3-Day User Training Course
CONTENTS 1
SCOPE..................................................................................................................................................4
2
INTRODUCTION TO ENTERPRISE..............................................................................................4 2.1 TOOL SUITE....................................................................................................................................4 2.2 THE DATABASE...............................................................................................................................5 2.2.1 What the Database Contains.................................................................................................5 2.2.2 Object Hierarchy...................................................................................................................6 2.2.3 Two-stage Commit.................................................................................................................7
3
SETTING UP A NEW PROJECT......................................................................................................8 3.1 3.2 3.3
4
USING THE GIS...............................................................................................................................15 4.1 4.2 4.3 4.4 4.5
5
STARTING ENTERPRISE...................................................................................................................8 CREATING & CONFIGURING A NEW PROJECT..............................................................................10 STARTING THE PROJECT...............................................................................................................14 OPENING A 2D VIEW....................................................................................................................15 DISPLAYING MAP DATA...............................................................................................................16 ZOOMING/PANNING......................................................................................................................16 FAVOURITES.................................................................................................................................18 DISPLAY INFO BAR.......................................................................................................................19
STARTING TO PLAN COVERAGE..............................................................................................20 5.1 SETTING UP..................................................................................................................................20 5.1.1 Importing Antennas.............................................................................................................20 5.1.2 Setting up a Propagation Model..........................................................................................22 5.1.3 Setting the Nominal Cell Radii............................................................................................24 5.1.4 Setting the Site Display Characteristics..............................................................................25 5.1.5 Defining a Site Template......................................................................................................26 5.2 ADDING SITES/CELLS...................................................................................................................27 5.3 PREDICTING COVERAGE...............................................................................................................29 5.4 DISPLAYING COVERAGE...............................................................................................................31 5.5 ANALYSING COVERAGE................................................................................................................36 5.6 EXERCISE 1: COVERAGE PLANNING.............................................................................................39 5.7 CELL REPEATERS..........................................................................................................................40
6
SITE FILTERS & FLAGS................................................................................................................44 6.1 6.2 6.3 6.4
7
PLANNING NEIGHBOURS............................................................................................................51 7.1 7.2 7.3 7.4 7.5
8
OVERVIEW....................................................................................................................................44 DEFINING & SETTING FLAGS.......................................................................................................45 DEFINING FILTERS........................................................................................................................47 EXERCISE 2: FLAGS & FILTERS....................................................................................................51 INTRODUCTION.............................................................................................................................51 NEIGHBOURS IN THE DATABASE...................................................................................................51 GRAPHICAL NEIGHBOUR ADDITION/DISPLAY..............................................................................53 AUTOMATIC NEIGHBOUR GENERATION........................................................................................54 EXERCISE 3: NEIGHBOUR PLANNING...........................................................................................57
TRAFFIC PLANNING AND CARRIER REQUIREMENTS......................................................58 8.1 INTRODUCTION.............................................................................................................................58 8.2 TERMINAL TYPES.........................................................................................................................58 8.3 TRAFFIC RASTERS........................................................................................................................60 8.4 TRAFFIC ANALYSIS.......................................................................................................................64 8.4.1 Process.................................................................................................................................64
8.4.2 Channel-to-Carrier Maps....................................................................................................64 8.4.3 Frequency Bands.................................................................................................................65 8.4.4 Carrier Layers.....................................................................................................................66 8.4.5 Cell Layers..........................................................................................................................70 8.4.6 Allocating Cell & Carrier Layers using Global Editor.......................................................72 8.4.7 Capturing Traffic.................................................................................................................74 8.4.8 Calculating Carrier Requirements......................................................................................77 8.5 EXERCISE 4: TRAFFIC & CARRIER REQUIREMENT PLANNING.....................................................78 9
FREQUENCY PLANNING..............................................................................................................78 9.1 OVERVIEW....................................................................................................................................78 9.2 INPUTS..........................................................................................................................................78 9.3 INTERFERENCE TABLES................................................................................................................79 9.4 VIEWING THE INTERFERENCE TABLE...........................................................................................81 9.5 ILSA.............................................................................................................................................82 9.5.1 General................................................................................................................................82 9.5.2 Selecting the Plan Type.......................................................................................................83 9.5.3 Cost Matrix Generation.......................................................................................................83 9.5.4 Selecting the Plan List.........................................................................................................87 9.5.5 Setting the Interference Reduction Method.........................................................................88 9.5.6 Configuration Options.........................................................................................................88 9.6 RUNNING ILSA............................................................................................................................90 9.7 INTERFERENCE ARRAYS...............................................................................................................92 9.8 IDENTIFYING BROKEN CONSTRAINTS..........................................................................................96 9.9 PLANNING BSICS.........................................................................................................................97 9.10 CELL INFO DISPLAY.....................................................................................................................98 9.11 FREQUENCY REUSE DISPLAY.....................................................................................................101 9.12 EXERCISE 5: FREQUENCY PLANNING.........................................................................................102
10
DUAL-BAND NETWORKS.......................................................................................................102 10.1 10.2 10.3 10.4
11
OVERVIEW..................................................................................................................................102 SETTING UP................................................................................................................................102 DUAL-BAND COVERAGE............................................................................................................106 EXERCISE 6: DUAL-BAND PLANNING........................................................................................106 ANTENNA SLOTS......................................................................................................................107
11.1 11.2 11.3 12
OVERVIEW..................................................................................................................................107 EXAMPLE 1 – PSEUDO-OMNI SITE..............................................................................................107 EXERCISE 7: ANTENNA SLOTS....................................................................................................110 MICROWAVE LINK PLANNING............................................................................................110
12.1 OVERVIEW..................................................................................................................................110 12.2 CREATING LINKS........................................................................................................................110 12.3 LINK FILTERS..............................................................................................................................114 12.4 VISIBILITY TOOL.........................................................................................................................115 12.5 HEIGHT PROFILER.......................................................................................................................116 12.5.1 Properties...........................................................................................................................117 12.5.2 Additional Toolbar Functions............................................................................................118 12.5.3 Analysing The Profile........................................................................................................119 12.6 EXERCISE 8: MICROWAVE LINK PLANNING................................................................................119 13
GENERATING REPORTS & PLOTS......................................................................................120 13.1 13.2 13.3 13.4 13.5 13.6
INTRODUCTION...........................................................................................................................120 SITE REPORTER...........................................................................................................................120 LINK REPORTER..........................................................................................................................121 CELL INFO REPORTER................................................................................................................122 CHANGE REPORT........................................................................................................................124 PRINTING/PLOTTING...................................................................................................................125
1
S COPE
This document provides notes and supporting material for the standard 3-day ASSET V3.3 User Training Course. It is assumed that the tool has been installed and a suitable database configured by the system administrator. Details of how to install the tool and how to set up a new database source are covered by the ENTERPRISE Administration Course and not by the User Course.
2
I NTRODUCTION TO E NTERPRISE
1
Tool Suite
ENTERPRISE is the name given by AIRCOM for our family of telecommunications system design and management tools. The ENTERPRISE tools share a common Windows NT4.0 platform, Geographical Information System (GIS) and Relational Database core. With ENTERPRISE V3.1 the following tools are available: ASSET
Radio network planning system.
NEPTUNE
GSM Testmobile Logging & Analysis system.
ARCHITECT
Cellular basestation equipment graphical template configuration system.
OPTIMA
GSM Network Performance Monitoring system.
CONNECT
Network Transmission and Microwave Link Planning system.
TARGET
Cellular Engineering Project Management and Tracking System.
TOOLS
A set of utility tools common to all members of the Enterprise family.
This training course deals with how to use ASSET to perform mobile radio communications network design tasks. The following diagram describes the key functional elements of the system and their interrelationship:
R e la t io n a l D a ta b a s e
L A N /W A N
N T W o r k s ta t io n s
P r in t e r / P lo tt e r
2
The Database
The Enterprise database is common to all the tools and can optionally be a Sybase SQL Anywhere 5.0 or Oracle 8 (or later) database. The database would typically reside on a dedicated server computer connected to your network. The Enterprise software is installed and run from client Windows NT 4.0 workstations also connected to the network. In an optional stand-alone configuration it is necessary to install the Sybase or Oracle database on the same PC as the Enterprise client. 1
What the Database Contains
The Enterprise Database stores all of the parameters required to fully describe the network being modelled. For ASSET this includes details of items such as (but not limited to):
Project definition settings (eg map projections, directory settings etc) Switching Equipment Physical Locations Base station Sites Cells & Cell Layers Carriers & Carrier Layers Neighbours & Exceptions Propagation Models Antenna Radiation Patterns Radio Equipment Details (eg TRUs, Combiners, Duxplexors, Feeders, Mast Head Amplifiers etc) Back-haul link details
The full list of items is too large to present here but can be found in the database table descriptions included in the Enterprise Technical Reference. Various database dialogues are used to enter/modify this data but the most commonly used is the Site Database window, which will be covered later in the course.
To view the parameters relating to a particular network element simply highlight the respective element in the tree view and click the Info>> button.
2
Object Hierarchy
One can see from the tree view in the Site Database window that the data is stored in such a way as to reflect the relationship of elements found in a cellular network. The tree structure can take one of three forms:
Logical links, where the inter-relationship of the cellular network describes the hierarchy of site elements.
Physical links, where the relationship between site elements is based on the physical connection in the cellular network.
Location, where the relationship is based on the parenting of network elements to physical locations (also called Properties).
To choose between these tree views, click on Settings at the bottom of the Site Database and toggle between Physical, Logical Links and Location modes.
The logical hierarchy is of particular significance in the tool, as it describes the relational link structure within the back-end relational database used by Asset to store the network data. This hierarchy has two important implications in the tool which users should be aware of: 1
It is not possible to delete objects until subordinate objects are first removed.
2
It is not possible to commit an object until subordinate objects are first committed.
The following diagram illustrates the key hierarchical objects: M SC BSC S it e C e ll LAC P ro p M o d e l A n te n n a S lo t
A n te n n a S u b C e ll
C h a n -to -C a r M a p In te r fe re n c e W g ts R e U s e G ro u p s
S y s te m C a r r ie r s
3
C a r r ie r - la y e r
Two-stage Commit
Data is stored within the database in two types of tables: 1
The COMMITTED tables which contain a master set of data accessible to all users.
2
The DIFFERENCE tables which contain changes with respect to the master COMMITTED tables for each individual user.
When a user makes a change to the database this change is first “APPLIED” which means that the change is stored in that user’s “DIFF” tables and can only be seen by that user. When the user is satisfied that the change is correct and that all users should be aware of the new network data, it is then “COMMITTED” to the master tables using the COMMIT or COMMIT ALL buttons. The COMMIT button commits selected changes whereas the COMMIT ALL button commits all changes made on all sites. This two-stage process for storing data in the database enables users to experiment with new designs without affecting other users until satisfied with the changes.
NOTE If a change has only been “Applied” to the database it is possible to use the Restore button in the Site Database window to revert back to the previous Committed state.
D a ta b a s e
C O M M IT T a b le s
D IF F T a b le s C O M M IT
APPLY
E n te r p r is e U s e r 1
U ser 1 U ser 2
E n te r p r is e U s e r 2
The next time a user restarts the project any committed changes from other users will be visible in the database. If a user tries to commit a change following a committed change to the same object by another user the system will warn the second user that that object has just been modified by another user also and gives the opportunity to cancel the second commit request.
3
S ETTING UP A NEW P ROJECT
1
Starting Enterprise
Once your system administrator has set up the Enterprise database and created a user account for you it is then possible to start Enterprise and create a new project ready for planning work. To start Enterprise go to the Windows Start Menu and look for: Start Programs AIRCOM International Enterprise V3.3 AIRCOM Enterprise Suite. NOTE It is possible to start each of the Enterprise applications independently from the Start menu but in this mode you will only see the menus/features for that tool alone. If you want to use all of the tools and be able to swap between them while planning you need to launch the Enterprise toolbar rather than the individual applications. When the application is first launched it searches for a valid licence. Firstly, it checks for a local licence (looks for a dongle on the local PC parallel port). If this is not found, it proceeds to check the network for a network dongle on a licence server PC. In order to check for a network licence your client PC must be told which network address corresponds to the licence server PC – done by
specifying either the IP address or computer name in the Nethasp.ini file located in your Enterprise program file directory.
NOTE The network licence configuration will normally be arranged by the system administrator. The following window appears on your screen when a valid licence has not been located. It suggests that either your local dongle is not connected or the network dongle cannot be contacted at the IP address you have configured. Check your local dongle or the configuration of your Nethasp.ini file and try again.
If on the second attempt your computer fails to pick up a licence and a local dongle is not being used, it can be concluded that all network licences are presently being used. Proceed to edit the Nethasp.ini to point to another licence server PC or simply wait till one becomes available. Once successfully launched you will see the Enterprise Toolbar along the top of your screen, with tabs for each of the applications mentioned earlier. To log in to the database click the Login button , you will then get an ODBC (Open Database Connectivity) login window like this:
ODBC is a set of database drivers and a manager that allows applications to access databases using a standardised form of SQL (Standard Query Language). Select your datasource from the pick-box, which lists all ODBC sources available to your PC (the source for your Enterprise database should have been configured by your administrator). Then enter your Enterprise username and password given to you by your administrator. When successfully logged on, you will be presented with the Start Project dialogue window, which lists the available projects in the database. The example below shows a database with just one project called “training”:
Projects can either be totally independent entities or they can be configured to share data. Typically different projects are used when planning different networks or when working with different sets of mapping data using different co-ordinate projection systems. To explain this more fully let us first look at what constitutes a project set-up by adding a new project.
2
Creating & Configuring a New Project
To add a new project you must firstly be logged in to the database as a user with “Create Project” permissions – if this is not the case the Add button in the Start Project window will be greyed-out. Now click the Add button to get the following Project Information window:
This is where we can choose to have either a completely new, standalone, project or to share existing network data from another project. Projects created using the New Project data option have a unique set of data tables, whereas projects created using the Share existing Project data option will make use of the same data tables as the project selected to share with, when the project is created. Each project has its own co-ordinate projection settings and directory settings for where the mapping data and coverage predictions are stored.
Projects with shared data are displayed as a hierarchy in the Start Project window. For example, above we show a project Training2 sharing the data with a project called Training, the third project (Training3) does not share data with another project: The question people often ask at this point is “So why would I want to share project data between projects when I could just keep using the existing project?”. The reason for having this feature is for countries where the radio network spans more than one co-ordinate projection system. For example a network in Australia could span seven different UTM (Universal Transverse Mercator) projection zones each requiring different settings to obtain the correct co-ordinate conversion between spherical co-ordinates (eg Lat/Long) and Cartesian co-ordinates (eg x/y grid). Nevertheless the user may wish to store all of the network data in one set of data tables. In this case it would be possible to set up seven different projects, one for each set of map data, all connected to the same set of data tables. NOTE Antennas are the exception to the rule. If a project is created using the “New Project data” option then the data is unique to that project. When importing new antenna patterns from the manufacturers data files (a process we will look at later) it is possible to make the new antennas available to all projects in the database. This means they don’t have to be imported every time you set up a new project. After selecting whether or not to share data from an existing project just click Continue to progress to the Modify Project dialogue:
To set up the project we first need to give it a name and to complete the entries in each of the tabbed sections of the window (eg Co-ord System, Map data directories etc…). Let’s have a look at each of these sections and explain what data is required. NOTE The various directory paths that specify the location of the relevant project map data and any user-created data (e.g. vectors, predictions, favourite views, etc) are normally stored in the database. As a consequence, these settings are available to all users logging in to that project. If a user wishes to temporarily alter these settings without affecting other users (for example, if trailing a different set of map data or creating a set of alternative coverage predictions), it is possible to specify a locally defined set of directories. The latter is achieved by checking the Override Database Directory Settings check-box and in doing the new directory paths get stored in an initialisation file on the local PC. These new settings no longer affect other users. Co-ord System The map co-ordinate projection settings, which correspond to the digital map data to be used, are specified in this tab. These are supplied by the map data vendor and generally found under the Height directory. They specify the conversion system used to map the ‘real’ Earth co-ordinates on to a flat, two-dimensional grid used when planning. Map Projection: Specifies the conversion algorithm used to convert from spherical (LatLong) to cartesian (X-Y grid) co-ordinates. Ellipsoid: Takes into account that the Earth is not spherical, but more ellipsoid in shape by offering corrections to the above algorithm. UTM Zone: Used when the Universal Transverse Mercator (UTM) projection is chosen. Divides the world into 60 zones, each covering 6 degrees of arc.
Map data directories All mapping data as supplied by the vendor is pointed to through this window. The browse button is used to locate and set the network directory containing the respective map data type – the directory setting will then be automatically filled in for you. Not all the types of data suggested here will be available to the project and can be left blank. Browse button Search for folder Select required map folder OK button
NOTE If you are accessing map data on a remote network computer it is best to enter the full network path including computer name (eg \\computer\map_data\country\data_type), rather than the path to a locally mapped network drive (eg F:\map_data\country\data_type). This will avoid problems with different users having different mapped network drive letters. This can be achieved using the Browse feature by navigating through the Network Neighbourhood item to the remote computer and from there to the relevant data directory. User data directories
All of these settings should be completed, the same Browse technique can be used as for the map data settings. Depending on the policy decided upon by your administrator you may store some of these items in shared directories or you may have your own local directories.
The directories relate to: User preferences Specifies a directory where favourite views can be stored and accessed. This data type can be created within Neptune and will be discussed later in the course. Prediction directory Stores coverage predictions created within Enterprise for later use. This directory path is of no consequence within Neptune, as the tool produces its own point predictions from the sites when required rather than mapping whole coverages. This entry can be left blank. Colour palette Specifies which colour palette file to use in preference to the default Windows colour palette. This is simply a text file containing a list of RGB numbers in the order that the desired colours should appear in the palette.
If fewer than 256 colours are specified the remaining palette entries are taken from the default Windows palette. Coverage Array This specifies the default location to store any coverage arrays directory stored by the user(s). User Line data Stores user-created vectors or polygons generated within the Enterprise suite. NOTE It is important that a unique directory is used to store the predictions for each project. The predictions are stored using a numbering scheme based on the database key numbers relating to the project, site and cell – these numbers can be reused between projects and to ensure the predictions are stored correctly they should be kept in separate directories. Map Data Extents This page defines the maximum and minimum easting (x) and northing (y) values of the available map data. These “extents” are required so that when the map view is first opened the view is targeted at the correct part of the world. You can either enter these values manually or click on the Calculate button, which will instruct the application to compute the correct values based on the map data in the directories you specified previously. Info This page allows the user to attach additional descriptions and comments against the project definition.
That completes the project set up. Click the OK button to save the set up. The set up can be modified at a later stage if required, by returning to the Start Project window, highlighting the desired project and then clicking on Info>>.
3
Starting the Project
Having completed the project set up you can then highlight the project in the Start Project window and click Start to open. The application will load the project data from the database into memory ready to start planning. When finished the buttons on the Enterprise toolbar will become enabled. Before Project is Loaded (buttons greyed)
After Project is Loaded (buttons greyed)
4
U SING THE GIS
1
Opening a 2D View
Once you have started a project you can open a new GIS window (2D View) by clicking on the button or by selecting View New 2D View from the menu bar. You will then get the following window:
There are a lot of buttons and information areas included in the 2D view. These are arranged into groups with a similar function – these groups are highlighted in the diagram above. We will look at each of these controls as we progress through the following topics. NOTE It is possible to open multiple 2D view windows if you wish to display different kinds of data simultaneously. This is done simply by clicking the New 2D View button.
2
Displaying Map Data
When a new 2D View is opened it is initially blank. To display items in the view you must select which items you want to view by using the “Add and remove items from view” drop-down tree window . For example to display a coastline you would click this button and then expand the “line data” tree item and select the check-box next to “coastline”. Clicking back in the 2D View area then draws the selected item:
To change the display styles of any object in the view simply double-click over the name for that item in the display list from the drop-down tree. A style menu will then appear offering a range of properties that may be changed relevant to that item. Once you have customised the colours and styles for each item these will be automatically saved on your PC for future sessions. NOTE A word of caution regarding the display of “rasterised” data such as heights or clutter. Before displaying these, please make sure you are not zoomed out too far. This kind of data can require a large amount of RAM to display – the amount being simply a function of the area being displayed divided by the area of a single pixel of the rasterised data. If the area you have selected requires more physical RAM than your PC has available the drawing process will be VERY slow. It is often best to draw some linear data first in order to navigate to the required view area (this requires much less RAM) before displaying the heights/clutter.
3
Zooming/Panning
Practice zooming and panning around the map data using the two-times zoom keys and the grabhand pan . Further zooming and display control functions are available from the 2D View context menu, which is accessed by right clicking in the display pane of the map view.
This context menu is very important and contains some of the most useful display control features such as: Redraw:
Refreshes the screen after manipulating data. Also linked to the Legend window to update all listed data.
Mouse Zoom:
Zooms into a desired location by defining the required area with a resizable box.
Menu Zoom:
In contrast to the above, this function zooms to:
A set multiplication factor (x-) A set window height (-km) A previous view (Last) A defined home view (Home)
Depending on the current view will determine whether zooming in or out will occur. Add to Favourites:
Stores frequently used views (including remembering what was displayed as well as where you were) and to quickly select between them from the favourites pick-box on the top bar of the 2D View window. These can be stored, shared and used by many users.
Organise Favourites:
Offers a way of renaming or removing existing favourites.
Site Symbol Display:
The properties with which sites are displayed in the view may be modified through the corresponding map data category in the Display List menu. These changes are performed on all sites contained within the filter, i.e. modifications occur on groups of sites. Site attributes can be changed on an individual basis by choosing this option from the menu. The desired site must first be selected
from the 2D View. Set Home:
Sets the Home view and specifies the zoom level with which a new 2D View will open up to.
Spend some time becoming familiar with these controls, particularly the Redraw, Mouse Zoom and Add to Favourites functions which are very useful.
4
Favourites
To add a new Favourite view simply set up the view you want and right-click in the display pane to get the context menu. Then select Add to Favourites and you will get the following dialogue:
Give the favourite a unique name, add any comments you want and select which display items to remember along with the favourite view. If you don’t select any of the attributes at the bottom then the favourite will simply store the view location, scale and size but not what was displayed. You can then quickly jump between favourites by selecting the one you want from the pick-box at the top of the 2D view:
NOTE At present it is not possible to modify a favourite once it is defined. If you want to change a favourite you must first delete the old one and re-add it. To delete a favourite go to the 2D view context menu and select Organise Favourites.
5
Display Info Bar
Clicking the
button at the bottom left of the 2D-View window shows the Display Info Bar:
This bar shows various items of information relevant to the current mouse location in the 2D-View. The items shown can be user selected by clicking the configuration dialogue:
button and using the following
Initially the display info bar is “docked” onto the first 2D-View opened. It can be undocked and allowed to float freely or can be docked onto an alternative 2D-View if more than one is open. To undock/dock the display info bar use the
key at the bottom of the 2D-View.
5
S TARTING TO P LAN C OVERAGE
1
Setting Up
Before we can start planning new cell sites and their coverage we need to set up a few important items such as: 1
Details of the antennas we want to use. The propagation models we are going to use to calculate coverage. The range of nominal cell radii we want to use. The display characteristics of our sites in the 2D-view. A site template defining the default characteristics when a site is added. Importing Antennas
The database stores detailed information regarding the antenna types you will use in your network. In particular it stores the horizontal and vertical radiation patterns (or “masks”) used when calculating the coverage from a particular cell. The simplest way of entering this data into the tool is to import it from a file supplied by the antenna manufacturer. The format supported by Enterprise is a well-known and widely supported format known as Planet format antenna files. To import a new antenna into a project you need to go to the File menu and select Import. Then select PlaNet/EET format. A number of different data types can be imported, in this case we want to just use the Antennas format so click on the Antennas tab and select the check-box at the top left to enable the import.
Next click the Add button and you will get an Explorer window where you must navigate to the correct location where your PlaNet format antenna files are stored on the network. Select the antenna files you want to import and click OK to add them to the import list.
If you want to add more then simply return to the Add button and select some more. When you have completed the list of antennas you require click Import to begin importing these into the database. NOTE If you check the Add to all Projects box then the antennas you import will be automatically made available to all projects in the database without the need to import them all again. When the import is complete you can view the new antennas from the Database Equipment Configuration Antennas window.
NOTE To avoid problems later in the process it is a good idea to Commit all of the antennas after you have imported them. 2
Setting up a Propagation Model
To set up a new propagation model go to Asset Tools Propagation Model Editor. Then click Add to create a new model from one of the available types. The available types will depend on the version of the tool you are using but a small dialogue will be presented after clicking Add, which allows you to select the form of model you require. For the purposes of this training we will use the “Standard Macrocell” form of model. Detailed documentation on each of the types of model is available in the manuals and further Application Notes are available on request. After adding a Standard Macrocell model we will set up a basic GSM900 model with some generic parameters. The Standard Macrocell model is based on the well-known Okumura-Hata form of model and these parameter values are derived from the published values for 900MHz. NOTE To obtain accurate coverage predictions it is essential to calibrate the model by comparing its results with measured propagation data for the frequency band you are using and the terrain/clutter environments you want to model. This process is described in detail in the AIRCOM Application Note P-TN-010-DO-003, which is available on request. Normally this calibration process will be carried out by a specialist in your organisation, who will then provide you with the correct settings for the model.
Give the model a new name, set the frequency for which it applies and set the Effective Earth Radius to use (default is the standard 4/3 of the true earth radius, i.e. 8491km).
Now set the basic coefficients of the path loss equation (the equation is given at the bottom of the window for info). For this example we will use a “single-piece” model which has just one set of slope and intercept (K1 & K2) values. It is possible to define models with a two-piece characteristic using the optional K1 (near) and K2 (near) values. For more details, see the model calibration section of the manual.
For training purposes select the Relative Effective Site Antenna Height calculation algorithm.
Select the Bullington method for combining the loss from multiple diffraction knife-edges.
The clutter loss offsets are used to fine-tune the accuracy of your model by allowing for the different loss characteristics in different clutter environments. These will be determined during the calibration process for your model. For training purposes we will ignore these settings – i.e. leave all values at zero.
When finished click on Apply and then Commit to complete the process. 3
Setting the Nominal Cell Radii
When adding new cell sites it is often useful to use nominal cell size hexagons as a guideline for the inter-site spacing you require to achieve good coverage. ASSET allows you to specify a range of cell sizes and to display hexagons while adding sites graphically in the 2D View. Before starting to add sites it is therefore a good idea to set your range of hexagons to an appropriate value. This is done from the Options Hexagon Radii window:
The way this feature works is by setting the “Mid-hexagon” radius. The tool then calculates a range of larger and smaller radii based on this middle size and the split type selected. The choice between “corner” and “face” simply refers to whether the radius refers to the distance from the centre of the hexagon to one of its vertices or to the mid-point of one of its faces. Set your mid-hex radius to 4000 for GSM900, which gives us a range of cell sizes from 250m to 16km with a type of “Face”. 4
Setting the Site Display Characteristics
Finally, before we start adding sites to the network we need to decide how we want to display them, there are various options and styles. To set these display properties, go to the 2D View window, open the display list tree and find the “All Sites” Site Filter item. Select the check-box next to this item to make it visible in the display and then double-click over the text of this item to obtain its display properties settings.
You can experiment with the various settings options here later, but for now set the following:
Style: Fill: Line colour: Fill colour: Size: Hexagon:
Sector Solid Black Yellow Automatic Style: Cloverleaf Fill: None
5
Defining a Site Template
Network elements can be added in the 2D View by selecting the appropriate Add X button and clicking on the location for the new object. When this new object (e.g. Site, MSC or BSC, etc) is added to the database it will have a certain set of characteristics (e.g. number of cells, antenna orientations, models, etc). It saves a lot of time to set these default “template” characteristics now, rather than to add a large number of sites and then configure each one manually in the Site Database. To set a Site Template go to Options Site Templates to get the following window:
Five different types of template can be defined but you can create multiple templates of each type. For example you might have a “Standard 3-Sector Site” template and a “Standard Omni Site” template etc. The currently active template (i.e. the one that will be used when adding a new object) is the one with the highlighted check-box next to it. You will notice that only one template of each type can be selected at any one time. Let’s create a new site template. To do this we must use another of the “context” menus, brought up by right clicking in the white space below the existing default templates:
Then click Add Cell Site to create a new Site Template, you will be prompted for a name for the new template – try “3-cell GSM900 Macro”. To configure the basic template characteristics do the following:
Set the Site hexagon Radius to 2000m for the new template.
Now add three cells to the site by right clicking on the text of the template name and selecting Add Cell; do the above three times.
Now set the model on the General Tab for each cell to be the GSM900 model you created earlier.
Set the antenna type on the Cell Config Tab for each cell to one of the antennas you imported earlier (select a suitable GSM900 sector antenna) and set the antenna height/azimuth for each cell. We will return to the other parameters on the Cell Config page later.
Finally ensure the template selection check-box is selected for the new template you have added so that this one will be used when adding new sites.
You are now ready to start planning your network!
2
Adding Sites/Cells
Now that we have defined all of the key parameters and set up a suitable template we are ready to start planning using the 2D View. First make sure you have some suitable map data displayed (e.g. roads, coastline, terrain etc) and that you have the All Sites site filter turned on in the display tree list.
Presently, the majority of tools found on the perimeter of the 2D View are greyed out. The exceptions to the case are those used for location control and to produce print outs of the current map view. Further to this, are the Selector, Add MSC and Add Property buttons to the left of the view, prompting you to start constructing a network. First we need to add an MSC. To do so click on the Add MSC button and then click on the physical location in the window where you want this network element to be placed. By adding an MSC, a further set of tools becomes enabled, amongst which is the Add BSC button. Only those functions that are applicable to currently placed object are available. Consequently, adding a BSC will enable you to start adding BTS sites to the view. Now select Add Site and you should be able to add cell sites in the same manner as MSCs/BSCs. You will see a ghost outline of your cell hexagon while adding new sites in order to assist you in spacing the sites appropriately.
When adding network element Asset automatically creates associated “Properties” if not exist in the vicinity of the location when you are adding the new element. Properties are physical locations or pieces of “real-estate”. These Properties can be displayed independently of the network elements.
Each network element must sit on a Property but more than one element can be co-sited on a Property. Moving network elements requires moving the Property (which automatically moves the network elements on it) or moving the element between properties. To adjust the location of the sites you have added click the Move Property button , select the object to move by clicking on it and then click again on the new location. Alternatively, this can be achieved through the Site Database by changing the Property coordinates. To delete a network element click on the Delete button and then click on the element to be deleted. The system will ask you to confirm your request before carrying out and deleting the chosen item. Once again it is possible to do through the Site Database. Deleting the element does not delete the Property as well, to delete this you must use the Delete Property button . NOTE When you delete an item from the database it is sent to the Wastebasket and not permanently deleted. If you have made a mistake you can go to the wastebasket and restore the deleted items. This option can be found under the Edit drop down menu. Until you empty the wastebasket an item is not permanently deleted and its identity cannot be duplicated – therefore if you want to reuse an identity (e.g. a site ID) you must permanently delete the item with that ID from the wastebasket first.
3
Predicting Coverage
Once you have added some new cell sites you will want to look at the predicted coverage of them. The first step is to create the coverage prediction calculations (often termed simply “predictions”). Open the coverage predictor from either Asset Tools Coverage/Interference Predictor or from the button on the Asset toolbar. You following window will then appear:
There are three ways of selecting the list of sites you want to calculate predictions for. These are selected with the radio buttons at the top-left of the window: Select a siteAfter selecting this option you can click on a site in the 2D View in order to select just that site for prediction. Filtered
If you select this option you can select a group of sites defined by a “Filter” (we will come back to what Filters are and how to define them later). The default filter is All Sites.
Sites displayed in a view
After selecting this option you can click in a specific 2D View window and the tool will create a list of sites for prediction corresponding to those visible in the view.
When the list of sites for prediction has been set, it is worth checking that a valid model type has been identified on each site (the predictor will list the models found for each site). If you see Unknown or the wrong model name against a site this indicated that you may have made a mistake when assigning the model in the Cell Config tab of either the Site Template you are using or for that specific cell in the Site Database. Correct these before predicting by editing the Cell Configs in the Site Database. With the list of sites for prediction defined you must then set the following: Radius
This is the maximum range from the site that the calculation will be performed to. The calculation radius is normally set on a site-by-site basis ( on the Misc tab for each site in the Site Database). If you want to override the site-defined radius you can do so here and select a calculation radius from the pick-box.
Resolution
The pixel resolution (in metres) that you want the calculation performed at. The list of available resolutions corresponds to the
available height and clutter map data resolutions in your system. If you only have one map data resolution then this box will default to that value. Re-calculate existing predictions
This option allows you to decide whether or not to force the tool to recalculate all predictions in the list you have defined or whether just to recalculate those which need to be recalculated. In latter case the predictor will skip predictions it believes to be up to date and will calculate those where either they don’t yet exist or where parameters have changed on the site invalidating the old prediction.
NOTE Parameter changes which require the recalculation of predictions include: antenna types, azimuths, tilts, heights, site/cell locations, prediction model changes. Changes which simply affect the transmitted power of the cell do not require re-prediction since the prediction is a pathloss calculation rather than a received power calculation. Now simply click the Start button to start the prediction process. The predictor will estimate an overall time requirement to carry out the calculations. The first estimate may not be correct since it needs to learn how fast your PC is. Subsequent time estimates should become more accurate. As the predictions progress you will see a next to each site in the list as that calculation is completed and stored to disk. At any point during the prediction process the calculations may be terminated using the Stop button. When all the predictions are completed the Stop button on the Predictor will revert back to being the Start button and the progress bar will have reached 100%.
4
Displaying Coverage
Displaying coverage can be done in two ways: Displaying individual predictions Individual predictions for sites or cells can be added to the 2D View display using the buttons at the top right of the 2D View. Click on the appropriate button (single cell or single site coverage) and then click on the cell/site you wish to display the prediction for in the 2D View. If a prediction exists it will be added to the 2D View, otherwise you will be given a warning in the Message Log window. A new display item will appear in the display tree list to allow you to remove these predictions from the view when you are finished with them.
The limitation of this method is that multiple predictions are not combined to display the “Best” coverage at each location but are simply overlaid on top of one another. Creating & Displaying a Coverage Array
With this method you first produce an “Array” which combines a number of predictions into a raster which contains the best coverage value for each location and other information regarding the serving cell. This Array can then be added to the 2D View by selecting the appropriate item in the display list tree. Before an array is created it is necessary to ensure that the appropriate parameters with which to do so have been set up correctly. The above is realised through the Array Settings dialogue found at the bottom of the Tools drop down menu.
There are various options and features with this window which we will explore during the course. For now we will accept the default settings when creating the ‘Best Server’ type of array. To create the Array click the Create Array
button to get the following window:
Select Best Server and click Create. You should receive a message in the Message Log window telling you how many subcells were added to the array – if the number was zero you have a problem! Common reasons for getting a “ 0 subcells processed” message are:
No predictions were found for the sites. Check your site configurations and look at the Misc tab in the Site Database to see if there are valid predictions for each site.
No cell and carrier layers are selected in the Array Settings window. (if you have a fresh install of the tool it should select all layers by default).
The site filter selected at the top of the Array creation window is not correct (default should be All, in which case this should not be the problem).
Having successfully created the array you display it by selecting the Coverage Best Server item from the display tree list:
Coverage Bands & Colours Defining what coverage levels and colours are used to display coverage in the “D-view requires the following set up: 1
Select OptionsCoverage Schemas from the Asset toolbar. You will then get the following dialogue showing the available schemas (initially just the default). This is where you define the coverage bands and colours (but not levels) to use:
The term SubCell is used because it is possible to have multiple cell-layers on a cell. Each occurrence of a cell-layer on a cell is known as a SubCell.
2
Click Add to add a new schema, then use the Add, Modify and Remove options to create a new schema, eg:
Each schema can be defined on either a System-wide or User-only basis. 3
Having defined the schema we then need to specify the signal levels corresponding to each colour band. This is done on the Cell-Layer definition. Select OptionsCell-Layers and then Coverage Thresholds:
For each schema it is possible to define the signal levels for each colour band by doubleclicking on the coverage band and entering a threshold value. 4
Finally, when displaying a coverage array it is possible to change the coverage schema being used by double clicking in the Best Server item in the display list:
Service Areas An alternative way of viewing the coverage array you have just created is as a “Service Area” plot showing the geographical areas where each cell is the dominant server rather than the signal strength information. To change from displaying Best Server to Service Area go to the display list and de-select Best Server and select Service Area.
The tool will then re-display the coverage as a service area plot with each cell area shown in a different colour.
The colours are chosen automatically by the tool. To change the way the tool selects the colours go to the Service Area display tree item and double-click over the text in the usual way to obtain its display properties. Details of what the colour parameters mean are given in the Asset User Reference Guide. NOTEThe Service Area colouring algorithm works best with the default Enterprise colour palette and with a screen with 65536 colours or greater. If your screen only has 256 colours you may find that the colours selected are not sufficiently different to distinguish adjacent service areas. You will need to adjust the colour choice parameters to obtain a good display.
5
Analysing Coverage
Asset incorporates some statistical tools for analysing coverage/interference arrays. We will look at interference later. For now lets see how we can examine the coverage of a network. The coverage statistics tool is opened through the button on the 2D View toolbar. This tool allows you to perform analysis on any of the different types of arrays, which you can create. You can either analyse the whole array or a specific part of it by specifying a polygon (i.e. a closed item of linear map data). Creating Polygons To create a new polygon map data item go to the Enterprise Tools Tab.
Select EditorsVector to obtain the vector/polygon editor tool:
To create a new polygon for coverage statistics analysis (as an example), expand the treeview to show the available polygon data and then right-click on the Polygon item to get the following context menu:
Click the Add Vector/Polygon button. You will be prompted to provide a name for the new polygon. Now highlight the new vector in the tree-list and click on Start. Then select the 2D View and click on the points which define the Polygon you want to create. When you are finished click Stop and the last two points will automatically be joined together because you selected Polygon earlier. The Undo button can be used while adding points to step back if you make a mistake. After clicking Stop you can move points by clicking Move and then dragging a point to a new location. When finished click Save to store the new polygon.
The new polygon should now be visible when you redraw and you can change its display properties in the usual way by double clicking on it in the display item tree list.
To analyse your coverage data click the window:
button on the 2D View toolbar to get the following
In this case we want to analyse our Best Server array which we created earlier, so make sure the relevant radio button is selected. The Coverage/Interference category is the level for which you want to analyse the coverage and can be selected from the coverage categories which you defined earlier (these are the same ones used for display purposes). Finally select whether to analyse the whole array or just the part within a specified polygon. To specify the polygon click Define>> to get a window like this:
Expand the tree to find the polygon to use for analysis, select the polygon using the check-box. Then click OK.
Finally, click OK to carry out the coverage analysis and a similar text report below appears:
The analysis is broken down into three parts: 1
The first section shows the analysis parameters such as the coverage level selected, polygons used together with some overall statistics such as the total area and area at target level or greater in km2 and as a percentage of the total.
2
Area statistics broken down by Clutter Category so you can see if you are meeting your coverage objectives in the important areas.
3
Statistics broken down on a cell-by-cell basis.
6
Exercise 1: Coverage Planning
Your trainer will provide you with a polygon defining the geographical area over which to plan a small GSM1800 network. Your objective is to cover 90% of the design area to a level of –85dBm while ensuring that the “urbanised” clutter categories are 75% covered to at least –75dBm.
You can use any number of cells on a site and can optimise the cell orientations but you must use the sector antenna provided and an antenna height of 25m agl. The EiRP of your cells must not exceed 68dBm. Your propagation model should be set-up in accordance with the following Standard Macrocell parameters: Frequency Earth Radius Mobile Height K1 K2 K3 K4 K5 K6 K7 Heff Diff Clutter
1800MHz 8491km 1.5m 160 40 -2.55 0 -13.82 -6.55 0.8 Relative Epstein Peterson No clutter offsets/heights
As a guideline you will require:
A suitable propagation model
A suitable antenna
Nominal cell hexagon radii of suitable size.
A correctly configured site template (it is suggested that you begin with a 3-cell site and then optimise the number/orientation of cells following the initial cell layout)
Then lay down a grid of sites spaced according to your nominal hexagon radius (display the hexagon while adding the sites to help with spacing). Predict the sites and create a coverage array to see how well your plan covers the area. Use the coverage statistics tool to measure exactly how well your plan performs. Adapt the plan by moving/deleting/adding cells until you meet the design criteria. Use the cell count in the Site Database window to see how many cells your plan requires.
7
Cell Repeaters
Asset incorporates facilities for modelling cell repeaters in the network. These are treated as “frequency-selective” repeaters rather than broadband; this means that they are “parented” to a host cell and are assumed to only repeat signals to/from that cell on the carriers used by the cell. The example below shows an area in a network where there is a cell at one end of a valley but the coverage doesn’t completely cover the valley. In this situation it may be appropriate to consider a
cell repeater rather than adding a new cell since the traffic demand will be low and may not justify the cost of a full cell-site.
To add a cell repeater in the valley parented from cell Site0A go to the 2D View toolbar and click the Add Repeater button . Next click on the parent cell you want and drag the resulting repeater to the location where you want it; click again to place the new repeater in the required location. You will see a line connecting the repeater to its parent cell and in the site database you will see a new entry under the relevant cell entry, e.g.:
Before the coverage from the new repeater can be calculated the RF details for it must be defined. These are found under the Config tab of the Site Database for the repeater element, e.g.:
The Tx Antenna details refer to the “coverage” antenna of the repeater; the Rx Antenna details refer to the antenna used to relay the repeated signal to/from the parent cell, e.g.:
L in k t o P a r e n t C e ll (R x A n te n n a )
R e p e a te r C o v e ra g e A n te n n a (T x A n te n n a )
R e p e a te r
NOTE It is essential to set the Rx Antenna Azimuth correctly in order to ensure that the repeater can receive a signal from the parent cell. The Rx Threshold sets the minimum received signal level, which the repeater will treat as a valid signal for amplification and re-transmission. The gain simply specifies the amount of amplification applied to the repeated signal. Having configured the repeater it must then be predicted in the same way as a cell (hence the need to specify the model to use for the repeater on the Config page) and then a coverage array (Best server) can be computed to show the effect of its coverage, e.g.:
For all other subsequent calculations in the tool the repeater coverage area is treated as part of the parent cell coverage area.
6
S ITE F ILTERS & F LAGS
1
Overview
Site Filters are a very important concept and useful feature in Enterprise. Filters provide a logical grouping of site elements according to their properties and/or functions. They are a powerful concept that allows the sub-division of the network into more manageable sections for analysis, diagnosis and display. Filters can either be Static or Dynamic: Static Filters
are simple lists of objects specified by name. These filters are fixed lists which can only be changed by the user adding or deleting object names from the list.
Dynamic Filters
are much more powerful filters which select sites based on various criteria such as:
Object type Status flag settings Cell layers assigned Parenting Geographical location
The items which are selected by dynamic filters are automatically updated when a change is made to any of the parameters which form part of the filter definition criteria. Status flags are one important filter parameter and we will look at these before looking at how to define filters.
2
Defining & Setting Flags
Flags are a method used to distinguish and categorise site elements within a network. To define the status flags for your network go to Enterprise Tools Editors Flags. You will then get the flag definition window shown below.
NOTE Being able to edit flag definitions is something that is often best restricted to certain key users or system administrators. The reason for this is that changing the flag definitions has an immediate impact on any existing filter definitions you have set up and accidentally loosing these can be very disruptive. You will note that there are two different types of flags you can define, one for Sites (e.g. MSCs, BSCs, BTSs, etc) and one for microwave links. The principles are the same for both and we will return to look at the microwave link flags later when we deal with backhaul planning in ASSET. To define a new flag we must first Add a new flag group. Then add the Flags for that particular group. For example we might have a Group called simply “Status” with flag options such as “nominal”, “in-build”, “commissioned”, “on-air”:
When you click Commit Changes these new flag definitions will be written to the permanent database tables. NOTE There is no Apply stage for this process – as soon as the change is made it impacts all users. Hence the warning above about restricting access to this feature. When you have Committed the new flags you will see a new item on the Status page in the Site Database against each network object, e.g.:
The new item is a combo-box, which has the name of your flag group and allows you to select one of the flag options defined. So in this example we can now “flag” each network element according to its roll-out status – this information can then be used (as will see shortly) to define filters to select (for example) all sites which are “on-air” etc. More flag groups can be defined in order to track other important status information, some examples below:
3
Defining Filters
To create a new Site Filter go to the Site Database window and click the Define>> button at the topleft of the window:
You will then get a window showing the existing filters (the All filter is not shown explicitly):
Click Add to define a new filter, which launches a Wizard that will guide you through the definition process:
The Wizard windows are organised into two parts. The left-hand side shows a view of all of the network elements currently matching the criteria of the filter as you define it (in the example above the default criteria are selecting all network elements). The right-hand side of the Wizard changes as we progress through the set up process to show the different criteria options. Give the filter a name and click Next>. Note: In this example we will define a filter to select all “On-Air” sites which lie within our polygon which we defined earlier.
In this first page we define:
Which types of network elements to select
Whether to select only elements with certain cell-layers assigned to them (and if so which layers)
Which flag settings to match.
The following show the settings for each of these for the example:
Selecting the cell-layers to identify on matching sites.
Setting up which flag settings qualify for the filter. In this case the “Status” flag.
Next the “Phase” flag.
Finally the “Region” flag.
Elements can also be selected depending on which switches they are parented to. By default all switches are selected. Additionally an MSC1 appears in the tree, which is not part of the network you have created. By default an MSC is added to the AMPS network.
Now we select our polygon that we defined earlier and add this to the list of geographical areas, which sites must be in to qualify for the filter.
Click Finish to complete the definition and apply the new filter. Note: the filter is only visible to the creator at this stage - you will need to Commit it before other users can use it too (if this is what you want).
The final page allows you to convert your new dynamic filter into a static filter. With static filters you can define/modify them with the options in the lower half of the window.
NOTE The cell-layer filter setting often catches out the unwary! If you have selected the checkbox to filter on cell-layers but have not highlighted any layers then the filter will not find any sites. You must ensure that the correct cell-layers are highlighted if the option is selected. The cellular structure displayed in the Site Database is dependent on the filter being used. Presently this is the All filter (the program’s default), which contains the entire cellular network. If available, different filters can be chosen from the drop down window. By doing so, the database window is updated to show the logical structure of sites specific to that filter.
The new filter can now be used throughout the tool to control which sites various actions are applied to. It can also be used to display the different groups of sites with different characteristics. For example, below the OnAir_in_Polygon sites are shown in Red whereas the All sites are shown in Blue:
To achieve this kind of display simply go to the display tree list and select both filters for display but give each different display properties:
Since the filter is “dynamic” as soon as you change one of the flag settings (e.g. set a new site to On-Air) or move a site inside the polygon it will automatically become included in the filter and will change colour on the display.
4
Exercise 2: Flags & Filters
Using the project you used earlier to produce the nominal network design use the flag editor to create two flags as follows: Status
Phase
Nominal Option Selected Acquired Built On-Air Urban Residential Coverage Main Road Coverage InFill Coverage
After committing these new flags to the database return to Asset and set the flags on some of your sites to appropriate values. Next create a filter called “OnAir-Urban” to pick out all “On-Air” sites within the design area polygon in the “Urban” coverage phase. Display the All filter using sector symbols coloured yellow and the OnAir-Urban filter using red sector symbols.
7
P LANNING N EIGHBOURS
1
Introduction
Creating and managing neighbour lists is an important part of the on-going engineering of any conventional cellular network. Asset stores neighbour lists in the database for each cell layer in the network and also includes some automated Neighbour list generation tools.
2
Neighbours in the database
Neighbours are stored in the database against each cell layer to allow for dual-band networks where a cell may have 900MHz and 1800MHz subcells each with their own set of neighbours. The neighbour lists for each cell can be viewed and modified through the relevant part of the Site Database window:
A neighbour is a handoff relationship from one cell to the neighbour cell. The relationship is directional and if you want handoffs to be possible in both directions you must define the “ mutual” neighbour. In other words if you create a neighbour relationship A B you do not automatically get a neighbour B A, it must be defined if required. To add a new neighbour using the database window, go to the neighbours page as shown above and click the Add button. You will then be prompted to specify the destination cell identity; enter this and click OK to add the neighbour. The new neighbour will be created with a default hysteresis margin. You can change this value by highlighting the neighbour, entering a new margin in the box at the bottom of the neighbour page and clicking Set. You will then need to Apply the changes to the database.
3
Graphical Neighbour Addition/Display
It is often much easier to design neighbour lists graphically since it is then possible to visualise the network coverage, terrain and proximity of cells to one another. To view the neighbour list for a specific cell click on the View Neighbours button on the left-hand toolbar of the 2D View window and then click on the cell in the view for which you want to display the neighbours. A new item will be added to the display showing the neighbours for the selected cell by drawing lines from the cell to each of its neighbours. An example is shown below:
To display neighbour lists for other cells simply repeat the process. The display can quickly become very cluttered and difficult to read with several neighbour lists; it is therefore possible to assign different colours to each list to help differentiate them. To do this go to the display tree list and open the new Neighbours/Exceptions item to show the set of neighbour lists currently being displayed:
As with any other display item, simply double-click on the text of the item in the tree list in order to view/modify the display properties. Make each set of neighbours a different colour and redraw the display to see the new settings, e.g.:
To add new neighbours graphically click on the Add Neighbours button then click on the “source” cell for the neighbour followed by the “destination” cell. You can continue to add more neighbours by clicking on source then destination. Remember, if you aren’t displaying the neighbours for a cell then you won’t see newly added neighbours on the screen as you add them – they will be added to the database but won’t be visible until you display the neighbours for that cell. Deleting neighbours is achieved through the database window – simply highlight the neighbour you wish to delete in the list on the neighbours page and then click Remove. Remember, if you want to delete the neighbour in both directions you must remove it from the list on both cells.
4
Automatic Neighbour Generation
Asset incorporates a tool that automatically generates neighbour lists based on the predicted coverage/cell service areas of your network. This tool is intended to provide a first-pass set of neighbours, which will then be examined by an experienced RF engineer prior to implementation. Neighbour list calculation is a very difficult task. What constitutes a “good” or “bad” neighbour relationship depends on a wide variety of factors; some of these factors cannot be modelled in a planning tool – there is no substitute for experience when it comes to defining neighbour lists but these tools can help to speed up the process. To generate neighbours automatically you first need to create either a Best Server coverage array or an Interference table for the area/sites required. For the time being we shall produce our neighbours based on the former, as this has been created earlier. Select Asset Tools Neighbours Neighbour Wizard. The following window will then appear.
This is the first page of the Wizard that takes you through the various set up options prior to calculating the neighbour lists. You will encounter these Wizards again later when we look at creating Interference Tables and Cost Matrices. In each case the first step in the process is to specify the 2D View window you want to work with (because you may have several open at any one time). By default, the wizard captures the view of the current map window. If you wish to vary the view in anyway or select that of another GIS window, click Select View, followed by the appropriate map view you wish to work with. The wizard will now pick up a snapshot of the new view that will be used. Click Next> to move on to the next screen of the Wizard. Here, you select the means by which you wish to create the neighbours. Both methods work on the same principle, which is to consider the amount of coverage overlap between cells.
When using the Best Server Array, neighbours are calculated from the service area. The tool looks for adjacent pixels from two cell service areas and if sufficient pixels are found that ‘touch’ each other, then a neighbour is created for that pair of cells. Alternatively, neighbours may be created based on the effected coverage area of cells as computed in the Interference Tables. Using the appropriate pixel resolution, the tool converts these areas into a number of overlapping pixels, from which neighbour relationships can be determined. More on Interference tables later. Specifying the minimum number of border/overlapping squares parameter determines how easy, or hard it is for any two cells to be defined as neighbours. Click on Next> to move on to the next page of the wizard:
First set the filter to indicate which group of sites you wish to consider when creating neighbours. The All filter shall be used for the purpose of this exercise. A hard-limit can be set to limit the number of neighbours that the automatic algorithm will create. The final parameter is the default handover hysteresis margin that will be assigned to all newly created neighbours. Now click Next> to get the final screen of the Wizard:
You can specify a file name to store the new neighbours in and any comments you wish to store with them. This can be useful if you want to reload them at a later date. Finally click Finish to calculate the neighbours. A while later, you will receive a message box reporting the number of neighbour relationships created for the number of cells processed:
At this stage the new neighbours are not stored in the database. This gives you the opportunity to review them before adding them to the database. To view the new neighbours not already in the database select Asset Tools Neighbours Analyse. A similar window to the one below will appear on your screen:
To view the neighbours for a cell you must select the cell in the left-hand pane of the analysis window. NOTE Only DIFFERENCES between the newly generated neighbours and those already in the Site Database are displayed. If the Status is “Not in Database” this means that the tool has found a new neighbour which does not currently exist in the Site Database. Conversely if the Status is “Not in File” this means there is a neighbour in the Site Database which does not exist in the newly created lists. The Add All Mutual button at the top of the window, converts all neighbours into a two-way relationship, if they weren’t already so. When you want to store the new neighbours to the database click Update Database. You will then be prompted to choose whether or not to remove any existing neighbours in the database which do not appear in the newly created list or not. If you choose not to remove existing neighbours then the database will contain the old neighbours plus any new ones found rather than a completely fresh list of neighbours.
5
Exercise 3: Neighbour Planning
For the cells in your nominal coverage design perform a neighbour analysis using a “Min border squares” value of 10 and “Max Neighbours” value of 16. Apply the neighbours to the database and display/edit the lists using the database and graphical tools until you are happy that the lists look good. It is important to get these lists correct before we get to frequency planning since they are one of the strongest constraints on how the planner can allocate carriers.
8
T RAFFIC P LANNING R EQUIREMENTS
1
Introduction
AND
C ARRIER
Asset incorporates a set of sophisticated traffic modelling and analysis capabilities, which you can use to model the performance of your network and to calculate new transceiver requirements. These features are designed to work not just with simple single-layer networks but also with multilayered and multi-band/multi-mode networks. In this introductory section we will focus on a simple single-band, single-layer network to start with. Multi-layer/multi-band network planning is dealt with later in the course.
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Terminal Types
Asset models traffic demand by generating traffic density maps for different “types” of terminal. These density maps define the amount of traffic (in Erlangs) offered to the network by each type of terminal on a pixel-by-pixel basis – the pixel size corresponding to one of the available clutter map data resolutions. Terminal Types in Asset are not to be confused with GSM Terminal Classes (which define max output powers etc). A Terminal Type in Asset defines three key characteristics:
How much traffic that type of terminal will generate in total.
How the traffic will be spread geographically.
Which Cell Layers can offer service to the traffic for that Terminal Type.
To define a terminal type select Asset Options Terminal Types to get the following window:
To add a new terminal type click Add. Next change the automatically derived name to one which is more appropriate for your network – for example GSM900. Apply this change.
Next go to the Cell Layers tab to select the layers on which this type of terminal can operate. In this case we should only have one layer, the GSM-Default cell layer. We will return to layers later when we look at HCS and dual-band networks. Highlight the layer name and click > to move it into the assigned pane on the right-hand side. Apply the change.
Now go to the Clutter tab. This is where we start to define the traffic characteristics of this type of terminal. There is a choice of two methods for assigning the traffic on this page. The first method is to “Use Total Traffic and Weights” in which case we calculate and assign a total traffic figure for our network (in Erlangs) entered in the box at the top right. The traffic figure now has to be divided amongst the various clutter classes by assigning a “weights” figure representative of the proportion of users for each category. The alternative is to directly assign a total traffic figure (in Erlangs) to each clutter type. For this example we will use the first method, i.e. Use Total Traffic and Weights. Estimate a total offered traffic figure for the geographical area of your network and enter this value in the Total Traffic box. Then double-click on each clutter type to assign a “weight” to this type. At the end all of the weights will be normalised to provide a percentage figure. One useful way to think of these weights is to enter the number of subscribers you might expect in each of the clutter types. When you have finished entering these values you should have a dialogue which is similar to the one below:
The next two tabbed pages, Vector and Polygon, allow one to assign additional traffic to linear or closed polygon map data features. So for example you might wish to allocate a specific amount of extra traffic to highways or to a polygon defining a well known traffic hot-spot (e.g. shopping mall etc). The process for assigning traffic to these items is the same as before. For the purposes of our example we will leave these blank and only use clutter information. When you are finished click Apply and then Commit to store the Terminal Type definition.
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Traffic Rasters
After defining a Terminal Type we must then calculate the traffic density map for the geographical area of our network. This is done using the Traffic Raster Wizard, found under Asset Tools Traffic Raster Wizard: NOTE One of the options in the Traffic Raster Wizard allows you to spread the assigned terminal traffic only to pixels where there is service from one of the cell sites. You might want to do this if you know the total carried traffic figure for your network (e.g. from network performance counters). If you want to use this option you MUST create a coverage array for your network before running the traffic spread. If you are trying to determine how much of the estimated available traffic is actually served by the network then you would probably not want to limit the traffic spread to just the coverage area of the network. The first page of the Traffic Raster Wizard is the same as the Neighbour Wizard we have already seen:
When satisfied with the captured map view, click Next> to proceed on to the next page of the wizard.
Ensure that the Terminal Type(s) that you want to model traffic for are selected by checking the appropriate box to its left. If they are not selected they will not be included in the traffic analysis. The option check-box at bottom left allows you to choose how to geographically spread the traffic you have assigned to any polygons. In our case we have not chosen to spread any traffic by polygon so this option is not relevant. To illustrate how this option works there are two examples below of a traffic spread across a polygon, one using clutter weights and one not:
Spread With Clutter Weights
Spread Without Clutter Weights
In both cases the total traffic in the polygon is the same but the way it is distributed is different.
Click Next> to get the next page of the Wizard:
Select the resolution you require for the traffic array (from the available map data resolutions) and check that the size of the array that will be created is not too large for your computer; otherwise it will be a slow process. Click Next>.
This is where you can choose to limit the traffic spread to just those pixels where you have network coverage. If you do not have a Best Server array already created or haven’t chosen the correct resolution (from the last page) of the coverage array, then the option will be greyed out (as in the example above). Click Next>.
It is possible to load real traffic-per-cell information from a text file and to use this information for the traffic modelling if desired. To do this you will need to obtain the relevant traffic data and produce a text file with the correct format (see the Enterprise Technical Reference Manual for the format of Traffic Per Cell files, .tpc). This file then needs to be loaded into memory using the Asset Tools Traffic Load Traffic per Cell option before running the Traffic
Wizard. You then select the check-box on this page of the Traffic Wizard to tell the tool to use the loaded traffic per cell information rather than the traffic values in the Terminal Type definition when calculating the geographical traffic spread. Click Next>.
On this last page you get the option to enter a filename to store the traffic raster for future reference. Once you have generated the raster and are happy that it represents a good model of the traffic in your area you might find it useful to save and reload later as a “benchmark”. Click Finish to compute the raster. To display the resulting traffic density map go to the display tree list and select the relevant traffic item, e.g.:
The traffic is displayed as a colour coded density map. You can set the start colour from the palette, the minimum traffic level and step size. You should then get a display of this type:
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Traffic Analysis
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Process
The traffic analysis process is described by the flow chart on the right. Before the process can get under way there are several pre-requisites which must be defined/created, these include:
A suitable traffic density raster A corresponding Best Server array A channel-to-carrier map for you system Defined/assigned carriers and carrier layers A GoS objective and traffic model selection
When these are in place the process is to first “Capture” the traffic which involves calculating how much of the traffic density map each sub-cell can serve. This traffic information must then be stored to the database. Next the tool calculates the number of traffic timeslots required and corresponding carriers based on the channel-to-carrier maps and GoS algorithm selected. The final step is to apply the carrier requirements to the database. The tool assigns the total carrier requirement per sub-cell according to the carrier layer priorities and max-carriers settings in the carrier layer configurations. If the above all sounds confusing and complicated all will hopefully become clear as we go through it step-by-step!
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T r a f fic R a s te r C re a te d
B e s t S e rv e r A rra y C re a te d
C a p tu r e T r a ffic p e r S u b C e ll
A p p ly T r a ffic to D a ta b a s e
C h a n n e l- to c a r r ie r M a p D e fin e d C a r r ie r s & C a r r ie r L a y e r s D e f in e d / A s s ig n e d G oS and T r a ffic M o d e l P a ra m e te rs S e t C o m p u te T im e s lo t & C a r r ie r R e q u ir e m e n ts
A p p ly C a r r ie r R e q u ir e m e n ts to D a ta b a s e
Channel-to-Carrier Maps
A Channel-to-Carrier map in Asset describes to the tool how to convert from a requirement for a certain number of GSM air-interface timeslots to an equivalent number of carriers. This is necessary since not every carrier has the full 8 timeslots available for traffic – some will be reserved for control purposes. To define the Channel-to-Carrier map you want to use go to Asset Options Channel Maps to get this window:
You will find a number of pre-defined mappings already there for you to use but these map not match with your own network requirements. To create a new channel to carrier map, click Add Map, provide it with a name and click OK to finish. The next step is to define the mapping in the right-hand pane. Select your new map from the list in the left-hand pane and you should see a blank list in the righthand pane. There are two columns in the right-hand pane. The first indicates the number of carriers on a cell and the second gives the equivalent number of available traffic timeslots (i.e. excludes any control timeslots). The “Default Number of Channels Per Carrier” field indicates the number of timeslots that will be added when the Add Carrier button is pressed. The exception to the latter is the first carrier added, where one control timeslot is automatically subtracted from the “Default Number of Channels Per Carrier”. Subsequent clicks on the Add Carrier button simply adds the current value in the “Default Number of Channels Per Carrier” field, to provide a cumulative sum of the number of traffic channels available for the number of carriers used. To set the “Default Number of Channels Per Carrier” enter a number in the respective box and click the Apply button. The next Add Carrier action will then use this new increment value. To modify the map afterwards simply highlight the entry you wish to modify, enter a new Max Chans value in the box at the bottom and click Apply to store the values. When you are finished click Close. NOTE It is important that you set the “Default Number of Channels Per Carrier” value before carrying out the traffic analysis. The reason for this is that if the number of timeslots required to support your traffic levels exceeds the number available in the last line of your Channel-to-Carrier map then the tool assumes that any additional carriers are available with the Default value of traffic timeslots on each. A typical value would therefore be 7 or 8. 3
Frequency Bands
Frequency bands divide the mobile radio spectrum into different carrier sets (e.g. GSM900, GSM1800, etc.) which are applied on a carrier layer basis. The use of these bands is optional and set through the general settings of the tool, found under the General tab of the Preferences window.
By considering carriers belonging to different bands, it is possible to restrict the allocation of these to certain carrier layers. Furthermore, the frequency planning algorithm will be able to consider the effects of inter-modulation interference on the network for the various carrier assignments. More on this, later. Every time a project is added, four default bands are created with it and listed in the Frequency Bands dialogue under the Options menu:
Other bands may be added to the list to suit the carriers available for use in your network or to take into account different technologies. This is done, by clicking the Add button to bring up the following window: Within this dialogue we specify the conversion formulas that describe the way in which uplink and downlink frequencies are extracted from their respective carrier numbers (ARFCNs), added in the Carriers dialogue. In some circumstances it might be necessary to have more that one conversion formula per band (e.g. AMPS networks). It is a good practice to start by providing the band with a more descriptive name. In the bottom half of the window, you then specify the appropriate parameters for the conversion formula. These are the starting frequency (A), the frequency step between adjacent carriers (B), the range of carriers for which the formula applies to and finally the uplink and downlink frequency separation. 4
Carrier Layers
We must now set up some carrier layers in our network since before the traffic analysis tool can assign the carrier requirements it generates to the sub-cells in the database there must be some available carrier layers for it to assign them to.
Carrier Layers are a logical grouping of carriers that perform common functions and are assigned to different cell layers. First we must specify which carriers we are allowed to use in our network. To do this click Asset Options Carriers:
Now populate the available carrier list by entering either ranges of carrier numbers (e.g. GSM carrier numbers) or individual carrier numbers. In our example we shall add GSM carrier numbers 1 to 60. Click the Range radio button, enter 1 to 60 and click Add. You should now see a list of carriers from 1 to 60 in the left hand pane:
Now click OK to finish. Now we can define the logical division of our list of available carriers. Click Asset Options Carrier Layers to define these:
A default carrier layer is created automatically when the project is created. In this case it is called GSM-default. In our example we are going to rename this default layer as “BCCH” and flag it as the control layer for our network. Enter a new name, click the Control Layer check-box, and select the appropriate frequency band for use with this layer. Click Apply to save the changes:
Next we assign the specific carrier numbers we wish to use on this layer. In this case we will use carriers 1 to 12 for the control, BCCH layer. Go to the Carriers tab, highlight carriers 1 to 12 in the left-hand pane and click > to assign these for use on this carrier layer. Click Apply to save the changes:
Using frequency bands on the carrier layers impedes any carrier assignments that do not appear on the band that you have chosen to use. The tool will notify you of this fact. The final parameter we must set is the “Maximum Allocatable Carriers” field. This value is very important! It defines the maximum number of carriers that can be assigned from this carrier layer on any one sub-cell. In the case of BCCH we only want 1 BCCH on any one cell so the value is set to 1. We will return to the significance of these values later when we are applying the results of the traffic carrier requirement analysis to the database. Now create a second Carrier Layer by clicking Add at the top of the window. Rename this new layer TCH (i.e. traffic channel carrier layer) and assign carriers 13 to 60 to this layer. Select the appropriate frequency band and ensure the control layer check box is not assigned since this is not a control layer and set the Max Allocatable Carriers value to a figure such as 7 (just an example). This means that on any one cell we can never allocate more than 1 BCCH carrier and 7 TCH carriers, i.e. 8 TRUs in total.
Now Commit both Carrier Layers to the database. 5
Cell Layers
The next step in the configuration process is to ensure that the relational link is established between Cell Layers and Carrier Layers. To do this we go to Asset Options Cell Layers:
As with the carrier layers a cell layer is created automatically when the project is created. In this case it is called GSM-default. Cell layers are used to define logical groups of transceivers on a cell and are often referred to as “sub-cells” when assigned to a cell together with the other RF details. For example we might define different cell-layers for Macro and Micro or for Overlaid and Underlaid – we will return to the concept of cell-layers and how to use them later when we look at HCS planning and Dual-band networks. For now we will just use the default cell-layer. First go to the Coverage Type tab:
As we saw earlier (page 34) this is where we define the coverage display colours and thresholds (under the Define Threshold Values button). It is also where we choose what Channel-to-Carrier
map to use for this cell-layer (and hence the associated carrier-layers). Select the Channel-to-Carrier map you wish to use (e.g. the one you created earlier) and click Apply to save the changes. The other setting on this page is the “Interference Weights” table. We will return to this later when we look at Frequency Planning. For now leave it set to the default setting. Now go to the Carrier Layers tab:
This is where we specify which carrier-layers are to act on which cell layers. In this case we will assign both BCCH and TCH to our GSM-default cell-layer. To do this highlight each carrier-layer in turn and click > to move it to the Allocated pane. You should now end up with:
NOTE The order in which carrier-layers appear in the Allocated list is very important. They should be sorted into the order in which you want carrier requirements to be assigned. For example if you had one BCCH layer and 3 TCH layers and arranged them such that BCCH was at the top of the list followed by TCH1, then TCH2 and TCH3. When you apply the carrier requirements from the traffic analysis, the carrier layers are assigned in the order in which they appear in the list up to their maximum allocatable carriers’ value (see page 65), until all requirements have been assigned. This process should become clearer as we go through the traffic process. In our example the BCCH should be at the top with TCH under. If this is not the case, highlight the appropriate carrier layer and use the keys to reorder them. When satisfied with the changes Apply them to the database.
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Allocating Cell & Carrier Layers using Global Editor
So far we have designed a small single-band network and we have defined the cell and carrier layers, which we will use for frequency planning. At this point though, we have not yet established the link between the cells and the cell/carrier layers in the database. Look in the Site Database at one of your cells and expand the tree to show the sub-cell (which will be the GSM-default one created automatically by the tool at start-up). You can view the available carrier layers by going to the Carriers tab:
You can see the BCCH and TCH Carrier Layers created earlier and allocated to the GSM-Default Cell Layer. However, at this point the layers are not available for use by the tool – this is indicated by the lack of an entry in the “Use” column next to each Carrier Layer one. To make these Carrier Layers available for use we must click the “Allocated” check-box and Apply the change to every assignment. This would be a long and tedious process, if this had to be done manually but fortunately we can use the Global Editor to carry out such a process for us. To open the Global Editor simply click on the Global Edit button at the bottom right-hand corner of the Site Database window. The following window will now appear:
The Global Editor provides the capability to make configuration changes across a number of sites simultaneously. The sites affected by the changes, is dependant on the filter selected at the top left of the window. The different tabbed pages in the Global Editor provide editing options for the corresponding items in the Site Database. This is a very powerful and useful tool and you should spend time familiarising yourself with its editing capabilities. In this case we want to use the Global Editor to make BCCH and TCH Carrier Layers available for use on all sites/cells. To do this go to the Carrier Layers tab:
You will see a combo-box at the top of the tabbed page listing all of the available Cell/Carrier Layer combinations. In this case we have just GSM-Default-BCCH and GSM-Default-TCH. Select GSM-Default-BCCH from the combo box and click the Layer Allocation check-box. This indicates that you wish to make a change to the allocation state of this layer. Next click on the adjacent Allocate/Remove check-box to indicate that we wish to Allocate this layer (leaving the check-box unchecked indicates removal).
Select GSM-Default-TCH from the combo-box and repeat the procedure. Finally click Apply to carry out the global edits. When the Global Editor is finished making the changes return to the Site Database and look at one of the cells you have edited to confirm that the Carrier Layers are now available for use:
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Capturing Traffic
The first step in Asset’s Traffic Analysis process is to combine the information contained in the Traffic Raster created earlier with the Best Server information. Using these two pieces of information it is possible to calculate the total traffic “captured” by the service area of each cell. Go to Asset Tools Traffic Analyse:
Select the filter you want to capture the traffic for (e.g. All), from the combo-box at the top. The extent of the coverage for each of the cells is dependant upon the parameters set-up earlier in the Array Settings dialogue. Those that we are concerned with when capturing traffic are as follows: Min Pred Radius
When you capture the traffic the tool creates a fresh Best Server array to ensure that it is up-to-date and valid. If any of the predictions are smaller than this size you will receive a warning in the Message Log.
Min Service Level
Coverage below this level will not be considered as valid service from the network. If the Best Server at any point is below this level then the traffic from that location will not be captured.
Max TA
If the timing advance from the serving cell at a specific location in the array is beyond this limit then the traffic at that location will not be captured.
Use Cell Layers
Normally, this check box should be selected indicating that you wish to take into account the cell-layer priorities and service areas when capturing the traffic. For instance, you might wish to know how much traffic the OL and UL layers are capturing or the macro/micro layers (these concepts will be covered later in the course). If you do not want to take the cell-layers into account then de-check this box.
Once you have set the appropriate parameters as shown above, click Capture Traffic to begin the analysis. You will receive a report showing the traffic captured by each sub-cell. This report is generated as a plain text file and is displayed using WordPad. The file can be saved for future reference if required:
The report will show each cell and each sub-cell together with the corresponding amount of traffic served. At the bottom you will get an overall figure of the traffic captured. If the total is less that the quantity that you assigned to the terminal type for the spread earlier then this indicates that not all of the traffic available fell within the service area of the network. To store these traffic demand values within the database, click the Apply Traffic to Subcells button.
The traffic values will then be stored in the appropriate traffic field on the sub-cell page of the Site Database, e.g.:
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Calculating Carrier Requirements
From the traffic per cell information it is now possible to calculate the number of carriers (i.e. TRUs) required to provide a specified GoS. This is accomplished using the bottom part of the Traffic Analysis window:
Set the Quality of Service objective you wish to design to and the traffic model (blocking, Erlang B, or queued, Erlang C). The Traffic per Customer figure represents an average subscriber talk time, generally in the region of 90 seconds. From this value the tool can estimate the number of subscribers for each sub-cell in the carrier requirements analysis. Click Analyse to calculate the carrier requirements. You will receive another text report but this time including details of the timeslot and carrier requirements:
The Channels Required column describes the number of GSM TDMA timeslots needed to provide the specified GoS (in this case 1% blocking with Erlang B). This is translated into an equivalent number of carriers using the Channel-to-Carrier map we defined earlier for this cell-layer (see page 65). The last two columns show that at present we have no carriers allocated (i.e. no frequency plan has yet been carried out) and we therefore would have 100% blocking on all our cells. These values become more interesting once we have an existing set of carrier allocations and want to compare the blocking performance with a new traffic distribution.
The final step in the process is to store the carrier requirements into the database, done by clicking on the Apply Carriers Required on SubCells button:
The tool will then take the total carrier requirement for each sub-cell and assign these to the carrier layers on that sub-cell starting with the highest priority carrier layer and working down the list of available carrier layers. In our case we have two layers, BCCH and TCH with the max_allocatable_carriers parameter set to 1 and 7 respectively. For a sub-cell with a total requirement of, say, 6 the tool will assign a requirement of 1 to BCCH and then 5 to TCH. If the requirement was 10 the tool would be unable to assign 2 of the requirements since we have limited the BCCH to 1 and TCH to 7 max (refer back to subsections 5 and 6 for more information). These carrier requirements will ensure that our frequency plan has the correct number of carriers on each sub-cell to provide the GoS that our network requires with the traffic requirements predicted. NOTE It is of course possible to simply manually assign the carrier requirements in the database through the Site Database dialogue or globally using the Global Editor. For example you could set a requirement of 1 BCCH and 2 TCH carriers for every cell using the global editor. However, the traffic planning features should give a more realistic plan of the geographical distribution of carrier requirements.
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Exercise 4: Traffic & Carrier Requirement Planning
Your trainer will provide you with the details for a GSM1800 Terminal Type. Set up this terminal type and carry out a traffic spread/capture/analysis to determine the carrier requirements for the cells in your network. If any of your cells exceed a demand of 6 carriers then add extra sites/cells and re-plan in order to reduce the traffic demands. When you have obtained the carrier requirements apply them to the database and check that they are correctly assigned to BCCH and TCH layers as described in this section.
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F REQUENCY P LANNING
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Overview
AIRCOM’s automatic frequency planning module is called ILSA – standing for Intelligent Local Search Algorithm. ILSA is a very powerful and flexible cost-based soft-constraint driven algorithm designed to provide the best possible frequency plans in even the most difficult network situations. The following section describes the main elements of frequency planning with ILSA. For an indepth treatment of all of the features in the module please refer to the ILSA Application Note; available on request from AIRCOM.
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Inputs
The following diagram illustrates which inputs are required for ILSA and how these are linked:
We have already examined some of these (shown above in grey boxes). The doted arrows describe inputs that are optional to the user. The remaining requirements are to generate an “Interference Table” and to set up and run the ILSA frequency planner (which includes setting the carrier separation constraints and associated cost matrix).
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Interference Tables
The Interference Table is one of the key inputs to the frequency planning algorithm. These tables are generated from the network coverage information and (optionally) from the traffic density raster. The array lists each cell in the network together with all possible interfering cells (i.e. all cells with predictions which overlap that of the cell in question. The larger your predictions the longer the list of possible interferers will be for each cell. For each possible interferer the array contains details of the amount of interfered area and (optionally) traffic if a co- or adjacent channel allocation were to be made by the frequency planner to that pair of cells. To generate the Interference Table for your network you must first have a valid Best Server array and a traffic density raster. With these in place go to Asset Tools Interference Tables Interference Table Wizard. The Wizard has the same familiar first page requiring you to specify which 2D View window to work with.
To proceed onto the next page of the wizard click on Next >, where the required sites and rasters are chosen and used in the generation of the tables.
Sites considered in the calculations are selected through the use of filters or alternatively, by capturing a specific view in which the necessary site elements are present. The resolution and extent of coverage of the various sites are pre-set through the Array Settings window. Amongst the various parameters that are applicable to the calculation of these tables are as follows: Resolution
The map data pixel size with which you wish to create the tables – the latter should normally be set to the same resolution as your predictions but you can specify a different resolution if you think the resulting array will take too much RAM.
Min Pred Radius
If any of the cells have predictions smaller than this size a warning will be produced in the Message Log.
Min Service Level Pixels with a Best Server level lower than this threshold will not be considered to have network service and will not therefore be included in the Interference Table. Use Cell Layers
Indicates that you wish to evaluate the Interference possibilities down to a subcell level, not just to the cell level. This will be required if you have multiple cell layers and wish to model how they interact from an interference viewpoint.
Max TA
Pixels with a serving cell with a timing advance beyond this limit will not be considered to have network service and will therefore not be included in the Interference Table.
In most situations it is essential to gain an understanding of the percentage and the degree to which traffic is affected. This information is a additional input to the frequency planner that imposes stricter levels of interference in relation to the traffic density experienced in different areas. Normally using traffic data produces better frequency plans since it is important to protect high traffic areas (e.g. urban areas) from interference much more than low traffic areas (e.g. agricultural land). To produce interference figures based on the amount of traffic affected, it is necessary to have the appropriate rasters available in the application. One was created earlier using the GSM900 terminal type and shall be used here. Firstly, we must instruct the tool to consider traffic density maps by checking the Use Traffic Data box followed by the required terminal types from the list. When you have set up these options click Next> to move on to the final page of the Wizard:
This page allows you to save the resulting Interference Table to a file for future reference (it is possible to load Interference Tables from file). This can save time if you are regularly re-planning large networks. Click Finish to calculate the Interference Table.
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Viewing the Interference Table
After creating the Interference Table it is possible to examine it using Asset Tools Interference Table View Interference Table.
For each sub-cell, the window shows the coverage area and traffic captured together with a list of the possible interfering cells. Clicking on an interferer, brings up the relevant co- and adjacent channel interference that would arise if frequency allocations of this kind were made to the cells in question. This data is shown to the right of the window. The Co-channel fields relate to the amount of interference, which would result from a co-channel assignment on the serving cell and the selected interferer. The Adjacent Channel fields show the same information but for possible adjacent channel allocations. You can select how to order the list of interferers using the radio buttons at the bottom. Sorting these by affected traffic for example shows the possible interferer where a co-channel allocation with the wanted cell would result in the largest amount of interfered traffic. To view the interference figures for other cells, it is necessary to click on the relevant cell in the 2D View or type in the Cell Id into the Cell field in the view window (above). As you can see this “what if?” interference information is exactly what the automatic frequency planning algorithm requires to be able to determine how good or how bad a particular frequency plan option is. Unfortunately the nature of this table does not lend itself to graphical display and can only be viewed using this viewing window.
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ILSA
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General
To launch the ILSA automatic frequency planning module, click on Asset Tools Frequency Planning Frequency Planning (ILSA). ILSA is a very comprehensive frequency planning system designed to provide maximum flexibility to the user. The trade-off for this flexibility is a degree of complexity in its use.
To provide an in-depth treatment of all of the features AIRCOM have produced an ILSA Application Note (available on request to registered users) which describes all of the capabilities. In the following sections we will learn how to use the key features of ILSA and how to generate a frequency plan for our training network. 2
Selecting the Plan Type
First go to the Plan Type page in ILSA:
Specify whether to create a completely new frequency plan (i.e. ignoring any existing carrier allocations already in the database) or to start with the existing plan in the database and create a new plan based on that. In our training example we don’t have any existing carriers allocated on any sites – we only have carrier requirements. The most appropriate option is therefore “Create New Plan”. 3
Cost Matrix Generation
Next go to the Cost Matrix tab:
ILSA works by finding carrier allocations, which minimise the overall “Cost” of the frequency plan. This cost is composed of two parts: 1
The remaining amount of interference in the network with the new plan.
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The sum of the cost penalties associated with broken carrier separation constraints.
Earlier we created an interference table, which constitutes the first of these pieces of information. The second comes from the Cost Matrix. This is calculated by defining a number of important carrier separation constraints (e.g. carriers allocated to neighbours shouldn’t be closer than 1 carrier apart, carriers allocated to the same cell shouldn’t be closer than the combiner spacing etc) and associating costs or penalties for breaking these separations. To define these separation constraints and create a cost matrix click on the Create Cost Matrix button to launch the set up Wizard:
When you first start the Wizard, the Filter list will be blank. The first thing to do is to Add the filter for those sites for which you wish to create a frequency plan for. In the example above the All filter has been selected. After adding a filter, a list of the available cell and carrier layers present on the chosen sites are listed in the right-hand pane. In the above example we have two layers: GSMDefault: BCCH and GSM-Default: TCH. You can choose to Include or Ignore each of the layers. Flagging a layer as “Ignore” means that it won’t be considered when creating the plan. For example, if you wanted to just plan the BCCH layer first you could ignore the TCH layer and come back and plan it later. In our example we will include both BCCH and TCH since we want to plan both. Individual carrier allocations can be flagged in the database as “fixed” indicating that they shouldn’t be changed:
By selecting “Allow Retune of Fixed Carriers” in the Cost Matrix Wizard it allows the tool to retune these fixed carriers in return for a specified cost (specified in the Retune Cost box next to the Allow Retune of Fixed Carriers check-box). So if you make this cost high the tool will try not to change the fixed carriers unless it must to obtain a plan with low interference. NOTE There is no absolute definition of what constitutes a “high” or “low” cost. The costs are effectively expressed in terms of the equivalent amount of affected traffic in mE. For example if the tool produces a plan which has 421mE of affected traffic in it and has broken one constraint which had a cost of 10,000 then the total plan cost will be 10,421. From experience AIRCOM have pre-assigned some default separation costs, which produce good results in most circumstances. The final parameter on the first page of the Cost Matrix Wizard is the layer “Weight”. This value can be set for each layer set to be planned and acts as a multiplier for any costs on that layer. So for example if we set the weight to 2 for BCCH and 1 for TCH then any costs incurred when constraints are broken on the BCCH layer will be doubled whereas those on the TCH layer will not. This has the effect of discouraging the algorithm from breaking constraints on the BCCH layer to a greater extent than the TCH layer. In our example we will leave both layers with a Weight of 1. Click Next>
The next two pages of the Wizard are closely linked and it is simpler to explain them together (see above). The first page defines the costs which will be incurred by the tool if it breaks one of these six types of carrier separation constraints: Cell
This carrier separations relates to any two carriers allocated to the same cell and is generally determined by your RF combiner performance.
Site
This carrier separation relates to any two carriers allocated to the cells on the same site.
Neighbour This carrier separation relates to any two carriers allocated to cells which are defined as neighbours in the database. Second Order Nbr
This carrier separation relates to any two carriers allocated to cells which share a common neighbour cell – i.e. they are neighbours of a neighbour.
Exception This cost is incurred if allocations are made which break one of the carrier exceptions you have defined in the database. Forbidden As well as “fixing” certain carriers on a cell you can “forbid” specific carriers. This means that the tool should never allocate these carriers on the cell where they are forbidden. If it breaks this constraint then this cost will be incurred. The second page allows you to define the separation sizes (in terms of carrier numbers) for each sub-cell/carrier layer combination. You can define different separations on different layers if you wish. For each separation you have a minimum value and a preferred value. The minimum value is set using the arrow keys adjacent to the value. The preferred value is set by increasing the cost of breaking this preferred separation using the arrow keys adjacent to the Cost of Preference values. The preferred value is automatically incremented to one above the minimum value when the cost is made non-zero. It is not possible to set a preferred value of more than one more than the minimum value. If the tool breaks the preference it will incur the specified cost so a higher cost makes it less likely that the preference will be broken. When the parameters have been set, click Finish to calculate the Cost Matrix for the constraints you have specified. This may take a short while for a large network – be patient. When complete, you will be returned to the ILSA window and you will see the comment “New cost matrix: Not yet saved to file” in the Current Cost Matrix status box. The newly created cost matrix may be saved to file for future use by clicking on the respective Save button on the Cost Matrix page of ILSA.
There are two additional buttons on this page, the Edit Carrier Costs button and the Edit Separation Costs button. The first of these becomes relevant when you have forbidden carriers
on certain cells – clicking this button brings up a dialogue where you can view and edit the costs associated with these individual forbidden carriers. The second button gives a dialogue where you can view and edit, on a sub-cell by sub-cell basis, the separation costs calculated previously. This is useful if you want one cell to have a different cost for the same constraint as another cell. When you have customised the costs in this way it is often useful to save the cost matrix for future reference rather than having to manually recreate it every time. Use the Save button for this. 4
Selecting the Plan List
The Plan List tab allows you to select which cell and carrier layers to plan, which to make readonly and which to ignore.
The list shows each of the filters selected when composing your cost matrix and the cell and carrier layers associated with these cells. By highlighting on each and setting the radio button on the right you can tell the tool whether to Plan, Read Only or Ignore that layer. The most common use of this feature is to selectively re-plan a group of cells within a larger network. To do this create two filters, one with the sites to be planned (eg FilterPlan) and one with all of the other sites (FilterBorder). When you create the cost matrix specify these two mutually exclusive filters in the cost-matrix wizard. When you have created the cost matrix and returned to the Plan List page you will see entries for both filters.
By making the FilterPlan entries Plan and the FilterBorder entries Read Only you can get the tool to retune the smaller group of cells while taking into account the existing carriers assigned to the bordering cells.
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Setting the Interference Reduction Method
Now go to the Intf. Table page in ILSA. This is where we choose how to minimise interference in the network when creating the frequency plan:
If you do not have an Interference Table created then the options will be greyed out and the frequency plan will not be able to take into account the network interference at all. The plan will simply be the result of the separation constraints and the cost-matrix. If you have an Interference Table without traffic data then you will only be given the option to minimise by area. In this case the algorithm will simply be concerned about achieving the lowest km2 of interference and not about where that interference is located. If you have an Interference Table which includes traffic data then you can choose to minimise by Area (as before), by Traffic or by some combination of the two. In the case of minimising by Traffic the algorithm is concerned with achieving the lowest level of mE of interfered traffic. Since we spread our traffic according to the clutter type when creating the traffic density map the result is that the algorithm will tend to place any residual interference in low-traffic areas. Normally minimising by traffic produces the best realistic plans but it does depend on using a reasonably realistic traffic raster for the Interference Table creation. 6
Configuration Options
This page contains a number of selection check-boxes to enable various features to be taken into account when producing the frequency plan.
We will return to the Frequency Hopping options later but briefly the first option allows the algorithm to take into account the diversity gain effect if any of the cells are using frequency hopping. This gain gives an improvement in the C/I and is therefore significant in determining how
good the overall plan is. The amount of gain varies with the size of the hopping group and is computed using a hard-coded look-up table. When using interference tables to produce a frequency plan, ILSA tries to minimise the average interference of the network by maintaining co and adjacent carrier allocations to a minimum. This may be achieved at a cost of a few cells suffering badly from interference. To ensure that these situations do not arise, one can tick the ‘Minimise number of interferers between two cells’ check box. The DTX option allows the algorithm to account for the interference reduction effects of having DTX enabled on the cells. The amount of interference reduction depends on the voice activity factors specified when setting up the DTX option. DTX is enabled using a check-box at the bottom of the Cell Config page of the Site Database dialogue. This is also where the voice activity factor is specified. The ‘Use Group Planning’ option enables planning by pre-defined reuse patterns – group planning. When this is enabled the reuse group pattern associated with the cell-layer(s) will be used when allocating carriers. To set up a new pattern go to Asset Options Groups:
Add a new group and give it an appropriate name (e.g. 4x12 as in the example above). Then go to the groups tab and set up the group definitions in the conventional way – you can either get the tool to auto-assign the carriers or you can manually assign them. Click Apply to store the new pattern. Now go to Asset Options Cell-Layers and select the Group Planning tab for one of the cell-layers:
It is now possible to specify that you want to use a particular reuse group pattern when planning carriers on this cell-layer. To do so select the “Use selected…” check box and pick the pattern you want to assign. Click Apply to save the changes. As long as you have selected Group Planning in ILSA the frequency planner will allocate carriers according to these group definitions. The final option in the list is whether or not to take into account inter-modulation interference when creating the frequency plan and the extent to which it is considered. By selecting this option you are effectively analysing the effects of linear carrier combinations to see if any of the resulting frequencies will interfere with other carrier allocations in the network.
Choosing to use this option requires a couple of additional parameters to be set namely the Tolerance and the linear combination order. The latter describes the degree to which frequency combinations are computed and analysed to see if any potential interference is possible. The former sets an accuracy constraint on these calculations. Due to the vast number of frequency combinations that ILSA will have to perform means that the time it takes to reach the optimum plan will be significantly increased.
6
Running ILSA
When all of the preceding options and parameters have been set up satisfactorily simply click Start on the ILSA main page to commence planning. The status box on the ILSA main page will first show “Initialising” while ILSA gets ready to start planning. A random assignment of carriers will then be made to act as a starting point since we chose New Plan rather than Load from Database. This initial assignment will have a high cost since there will be many broken constraints and considerable interference. ILSA will then start to optimise the plan finding changes to the frequencies allocated which reduce the overall plan cost. It is possible for such an algorithm to get “stuck” in a local minimum where no further improvements can be achieved. ILSA recognises when this has occurred and will make a change to the allocations which it knows will temporarily increase the plan cost but will enable it to investigate a new set of allocations which could lead to an overall plan improvement. This process will continue until a plan
with zero cost is achieved – this happens rarely and it is normally necessary for the user to manually halt the optimisation – check the results and if necessary restart ILSA from where it was halted. As ILSA progresses you can view the cost of the current plan it has developed compared with the cost of its initial “random” assignment. This gives some indication for how far it has progressed but is difficult to interpret. It is often more instructive to view the cost and residual interference levels graphically. To do this, you just select display of the Interference data by clicking the Show checkbox next to the Average and Worst affected traffic information, as below:
You will then be able to view the amount of interfered traffic in the worst cell in the plan and the average interference of the network. This information can also be graphed by clicking the Show graph> button:
Generally the cost function (shown in red) decreases rapidly as the planner finds allocations which don’t break any of the separation constraints (unless it is a particularly difficult plan). After this the remaining cost of the plan will be interference rather than broken constraints. The “worst” cell interference value is shown in blue and will go up and down as the algorithm tries new allocations. The “average” cell interference is shown in green and should trend downwards as the iterations progress.
You can Stop ILSA at any time and can view the assignments it has made using the View Assignments button. If you then want to restart from where it was stopped simply click Continue. The View Assignments button gives the following display:
The left-hand pane of this window shows each of the carriers in use on the selected filter/cell/carrier layers and details of how many times they have been used in the network and the minimum reuse distance. The right-hand pane shows a cell-by-cell breakdown of the assignments and the residual interference level. In both of these panes it is possible to sort the data by column by clicking on the relevant column header. To store your new frequency assignments to the database return to the ILSA main page and click Apply Plan. Until you have done this it is not possible to create and view C/I or C/A data since these are derived from the assignments in the database.
7
Interference Arrays
Once a frequency plan has been created and stored to the database it is then possible to view the resulting interference graphically in the 2D View. This is done through the same array creation window that we used earlier for creating the Best Server arrays. Before using the Array Creation window, it is necessary to set up some initial constraints, such as the type of interference and cell/carrier layer we wish to examine. Call up the Array Settings window, found at the bottom of the Tools drop down menu.
When we talk about “interference” we need to specify to the tool whether we mean co-channel, adjacent-channel or the sum of the two, done by selecting the appropriate radio button on the Interference tab of the window. Select whether you require co or adjacent-channel analysis or the sum of the two. We will return to the other option on this page later. Finally, before creating the array ensure that the correct Cell and Carrier layers have been included for the interference analysis to be performed. This feature allows you to just look at certain layers individually or to look at the plan as a whole.
Next, go to the relevant 2D View and click the
button to get the window below:
There are several options for interference analysis and are described below: Worst/Average Connection
Worst Interferer
These arrays are used when you have frequency hopping cells in the network and you want to model the interference. The Worst Connection calculates what the equivalent interference of the worst hopping group is. Conversely the Average Connection calculates the equivalent interference averaged over all hopping groups.
This is for non-hopping networks and simply calculates the interference between the serving carrier at that location and the strongest interfering carrier.
Total Interference This is also for non-hopping networks and calculates the interference between the serving carrier at that location and summed interference from all cells using the interfering carrier. Now click OK to calculate the interference array. The array you have created can be displayed in the normal way by going to the 2D View and selecting the array from the list of available display items. In this example a Worst Interferer array has been calculated for just C/I:
The display will then show a colour coded map of C/I values (in this example) – the colours are customisable in the usual way by double clicking over the display item’s name:
As with Best Server arrays you can use the Coverage Statistics tool ( ) to compute area-based statistics on the interference in your network. Simply launch the Coverage Statistics tool, select the type of interference array you have created, the level you want to analyse to and any polygons. You will then get a text report giving you statistics on the interference performance, e.g.:
8
Identifying Broken Constraints
The Frequency Plan Reporter provides a facility to quickly identify where the frequency planner may have broken any of the constraints you set. To start this tool go to Asset Reports Frequency Plan Reporter:
Select the filter of sites you want to analyse and set the separation thresholds you want to query against. For example if you want to identify all cells where neighbours have been allocated on channels which are closer than 2 carriers apart, set up the dialogue as follows:
Clicking Generate produces a text file output identifying the constraints broken and giving details of them:
The same can be done for other separations and exceptions. It is also possible to generate a report detailing all f the remaining interference issues and quantifying them together with some overall summary data. Select the Interference report option and click Generate:
9
Planning BSICs
Asset also includes a simple BSIC planner, which auto-assigns the BSICs to maximise the distance between any two cells using the same BSIC. To start this tool select Asset Tools Frequency Planning Plan BSICs:
Select the NCCs that are permitted in your network and the site filter you want to plan the BSICs for, then click OK. The BSICs will then be auto-assigned and can be viewed in the Site Database under the General tab for each cell.
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Cell Info Display
To display information such as the BSICs or carrier numbers in the 2D View you can use the Cell Info display option:
Double click over the name of the display item to set the properties of what will be displayed:
This is a rather complex dialogue with many options and it can be somewhat difficult to set up. Let’s look at some examples to explain how to use it: Displaying BSICs To display the BSICs we first select the method used to search the required items. Searching by Cell Identity enables you to enter a specific cell ID (e.g. Site0A) and display data for that cell alone (this feature works only for one cell at a time – no multiple cell Ids or wildcards work with this method). Searching by Carrier(s) is more flexible and allows you to specify ranges of carriers to search for or wildcards to display all.
In the above example, we have selected the second of the two search engines (i.e. Carrier(s)), to locate all carriers (by using the wildcard “*”) allocated to the various carrier layers (ALL) defined in this project.
Next we move on to the Cell Parameters page and place further constraints on the items we wish to display. By specifying values in the respective boxes, we are effectively filtering out site elements that don’t match any or all of these fields, depending on the radio button selected on this page. A “*” in the box means pick out all entries. One can also specify exact matches if required (e.g. all cells where the BSIC = 14). In this example set the BSIC entry to “*” and clear all other fields.
Now that the appropriate sites have been filtered out, we need to specify the information that we wish to display for those sites still present. Through the Colour tab, we select the information and the properties with which they are displayed. Select the required information from the drop down list, provide it with a colour, and choose the manner in which is displayed by checking the appropriate boxes across the bottom of the window.
The Font page describes the format with which any textual information is presented in the 2D View. Once satisfied with the settings, click OK. Redrawing the display will show the requested data. In our case the Cell Ids and BSICs can be seen:
Displaying Carriers The assigned carriers are displayed in a very similar way. Set up the first page as before, searching by carrier and with a * in the Carriers box. Then go to the Colours tab and remove the check-box selection for the display method of the BSICs (i.e. de-select Text so that the BSICs will not be drawn on-screen).
Next choose Matching Carrier (Ctrl) entry from the drop down list and ensure this is selected as a text draw method as shown below. Repeat the above for Matching Carrier (Traffic) entry. Once finished click OK to store these changes.
Then click in the 2D View and redraw to see the carriers:
11
Frequency Reuse Display
In the Cell Info display list you will notice an item called “Freq Re-Use”. This facility allows you to display cell service areas coloured according to the carriers in use on that cell.
Double click on the item’s name and its respective properties dialogue will appear, through which you define the carriers you wish to display and the colours to be used.
In the above example carriers 1 to 12 will be displayed wherever they are in use and the colouring will start from red and proceed through the palette for each sequential carrier:
This can be very useful when checking the allocations made by the frequency planner.
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Exercise 5: Frequency Planning
Now create a frequency plan for your network by first creating an Interference Table and Cost Matrix as described above. Run ILSA to obtain a frequency plan, apply the carriers to the database and evaluate the C/I and C/A performance of your network using the coverage array tools and statistics analysis.
10 D UAL -B AND N ETWORKS 1
Overview
There are two key methods for modelling dual-band networks with Enterprise V3.1, these are: 1
By defining a single cell with 2 sub-cells (i.e. GSM900 and GSM1800).
2
By defining 2 cells, one with a GSM900 sub-cells and the other with GSM1800 sub-cells.
The following section will take you through how to set a dual-band network using the 2-cell configuration.
2
Setting Up
The following example (based on the project we have been using throughout the course) explains how to set up the dual-band system: We want to set up two cell layers, one for GSM900 and one for GSM1800 since each will have a different set of transceivers. To do this: 1
Rename the GSM-Default cell-layer as GSM900.
2
Create a new cell-layer called GSM1800.
3
Make the GSM1800 cell-layer priority 1 and the GSM900 layer priority 2 (use the + and – keys in the cell layer configuration window, Options Cell Layers). This means that traffic will try to go to the GSM1800 layer first but if the layer threshold parameters are not satisfied it will then go to the GSM900 layer. We will set the layer thresholds later.
4
Define the coverage thresholds for the new cell layer. Set these to the same values as used in the GSM900 layer. If the above is not done your coverage will not appear in the 2D View although you have performed coverage predictions and arrays.
Next we need to have suitable propagation models and antennas for use on our GSM1800 cells, so: 1
Define a new propagation models for both GSM900 and GSM1800 bands – default parameters are given below: Frequency Earth Radius Mobile Height K1 K2 K3 K4 K5 K6 K7 Heff Diff Clutter
2
900MHz 8491km 1.5m 140 38 -2.55 0 -13.82 -6.55 0.7 Relative Epstein Peterson No clutter offsets/heights
1800MHz 8491km 1.5m 160 40 -2.55 0 -13.82 -6.55 0.8 Relative Epstein Peterson No clutter offsets/heights
Import suitable antennas for each layer.
Now we will reconfigure one of our cell sites as an example of how to set up the configuration: 1
Select the cell site you want to make into a dual-band site.
2
At present you will have three GSM900 cells (i.e. the default layer was renamed to GSM900). Now add three new cells to the site (by right-clicking on the text of the Site ID and selecting Add Cell.
3
By default the new cells will have the GSM900 cell assigned since this is the project default layer (i.e. we renamed the GSM-Default layer to GSM900 earlier). We must therefore delete these layers from the new cells and add the GSM1800 layer. To do this use the context menu obtained by right clicking over the text of the sub-cell and select Delete Cell Layer. Now continue by right clicking on the text of the cell ID and selecting Add Cell Layer GSM1800. The configuration should now look like this:
Now we need to ensure that the Cell Config for each cell is correct, i.e. that we have the correct propagation models and antenna details. 1
Select each cell in turn and set up the Cell Config as appropriate. In this example set up the three GSM900 cells with antenna heights of 25m and orientations of 0, 120, 240 degrees. The three GSM1800 cells should have the 1800MHz antenna assigned and orientations of 0, 120, 240 degrees at an antenna height of 23m.
2
Check that on the General page for each cell the propagation model is set to the correct one for the band of that cell.
NOTE Be careful not to accidentally set the propagation model on the sub-cell. Although this would be an alternative way of setting the model for each cell, it is only really used when considering multiple cell layers on each cell. Set the model at the cell level. The final step in the process is to configure the sub-cells: 1
Go to the sub-cell page by clicking on the sub-cell.
2
On the general page we need to set the layer threshold that will determine when mobiles will be served on that layer if no higher priority layer thresholds are met. In our example we will use the signal level threshold to control how traffic moves between layers. On the GSM900 layer set the Signal Threshold to –102dBm. On the GSM1800 layer set it to -75dBm. This will force traffic onto the GSM1800 layer (the higher priority layer) as long as the received level is better than –75dBm otherwise the traffic will go to the GSM900 layer.
3
Finally go to the Antenna/TRU page for each sub-cell on the site and ensure that the cell layer is enabled to transmit through the antennas you have defined (which are defined on antenna slot 1 – we will come back to antenna slots).
3
Dual-Band Coverage
With the site and cells configured it is now possible to create new predictions for the 1800MHz cells and display the different cell service areas. 1
Open the Coverage Predictor and re-run the predictions for your sites – any that are “out-ofdate” (such as the GSM1800 predictions) with be created.
2
Next create a Best Server coverage array and display the Service Area plot. Remember to select the GSM900 and GSM1800 layers for inclusion in the array (through the Array Settings window from the Tools menu) otherwise you won’t see the interaction of the layers.
You should be able to see the different service areas of the GSM900 cells and the GSM1800 cells. In the example below a filter was used to display the Service area for a single site to make it clearer:
So we can now use this new coverage information to carry out Neighbour analysis for the dual-band cells, calculate the traffic each band will “capture” and hence the carrier requirements etc.
4
Exercise 6: Dual-Band Planning
Set up a dual-band site as described in this section and create a cell service area plot (example above) to confirm that you can see the different layers and how the layer priorities/thresholds control the behaviour. Create a dual-band terminal type and assign it to operate on both GSM900 and GSM1800 cell layers. Your trainer will provide suitable traffic values. Now carry out a traffic raster spread with both the dual-band and single band GSM1800 terminals and capture the traffic to show how the different layers capture traffic from different terminals.
11 A NTENNA S LOTS 1
Overview
An antenna slot in Enterprise is a logical grouping of antennas. Cell layers (i.e. groups of transceivers) are mapped to particular slots enabling users to define cell configurations where different transceivers are connected to different antenna systems. A cell layer can actually be mapped to more than one slot if required enabling the user to model systems where distributed antennas are being used (e.g. on a large rooftop).
2
Example 1 – Pseudo-omni Site
Often in rural areas cells are designed to purely provide coverage to a stretch of road and there is no significant capacity requirement. In this case it is common to deploy one transceiver connected through a power splitter to two directional antennas pointing up and down the road, e.g.:
To model this in ASSET we would create a site with a single cell and cell layer but two antenna slots as follows: 1
Create the Site in the usual way.
2
Configure the site to have just one cell with a single sub-cell.
3
On the Cell Config page of the Site Database entry for the cell Add a second antenna slot.
4
Configure slot 1 to have a sector antenna at 0 deg and 25m agl. Slot 2 should have the same antenna but at 180 deg and 25m agl. In the 2D View you should now see a configuration like this:
4
Finally go to the Antenna/TRU page for the sub-cell and ensure that the it is connected to both antenna slots.
Now when the site is predicted and the coverage displayed you will see that both antennas radiate from the same sub-cell:
It is even possible to physically separate the antennas, for example as if they were located at different ends of a long rooftop. To do so, use the Move Antenna button on the left-hand toolbar of the 2D View. When you have repositioned the antenna re-predict the site and recreate the coverage array to see the new coverage:
You will notice that the new antenna location is reflected in the site database by specifying a relative (or optionally an absolute) antenna location with respect to the site location:
3
Exercise 7: Antenna Slots
Create a pseudo-omni site as described in this section. Create the coverage and move the antennas to see the effect of distributed antennas.
12 M ICROWAVE L INK P LANNING 1
Overview
ASSET incorporates a basic back-haul point-to-point link planning facility to enable planners to carry out basic link network topology designs, to decide upon link technology choices and routing plans. Note that this functionality is greatly enhanced and extended when CONNECT is used in conjunction with ASSET.
2
Creating Links
Links are automatically created to the nearest logical predecessor when a network element is added to the 2D View or Site Database. These links can be displayed in the view by enabling the All Links option in the display list tree.
Before adding BTS sites you need to decide on the type of parenting required, that is, either to the nearest BSC or to the nearest distribution node. The above is set through the Preferences dialogue found under the File menu.
Most of the links created by the tool will not be suitable and will require your analysis and intervention. The easiest way of adding a link between two network elements is to use the graphical tools in the 2D View. On the left-hand toolbar of the map view you will find two buttons for adding and deleting links, respectively: . To add a new link, select the Add Link button and then click on the start and end sites for that link. A line will appear in the 2D View showing the new link. If not the case, simply use the redraw option from the context menu to refresh the screen.
The link details are stored in the database and can be viewed/modified through the Asset Database Links window:
In the above example the window is displaying the details for the link that was added between Site3 and Site7. The link is a Microwave one operating with a capacity of 2048Kbs and extends to a length of 2.72km (calculated by the tool). More details of the link are available by clicking the Info>> button, which expands the window to show a number of tabbed pages:
The various pages are described below: The LinkEnd A & B pages define all of the RF characteristics of the radio equipment at each end of the link. These are required to calculate the link budget (see Availability page later).
The Profile page shows the terrain profile along the link with the land coloured according to the clutter across the profile (display colours set in the 2D View). If you have a propagation model with clutter height values defined you may select this model from the combo box and the heights will be added to the terrain height for the profile. A percentage of Fresnel clearance zone may also be displayed. The Rainfall page is where the climatic parameters are set (in accordance with the ITU link availability calculation methods) in order to account for link fading.
The Availability page shows the results of the link budget analysis for each link, as calculated from the parameters entered on the preceding pages. The dialogue shows the computed availability in % and the fade margin available on the link.
The Info page simply gives information on which user created the link and who last modified it.
The final page is the Status page, which shows the Microwave Link Flag settings for this particular link. This functionality is the same as that for Sites. Flags may be defined using the Flag Editor and used to categorise links (and to define link filters).
3
Link Filters
Defining link filters is analogous to the process for defining site filters. In the Link Database window there is a Define>> button. Click this to get the Link Filter window showing the list of available filters (as with site filters the default ALL filter is not show explicitly). Then click Add to get the Link Filter Wizard:
The key difference between link and site filters is that with Link filters it is only possible to filter on status flags.
Click Finish to apply the new filter to the database. Commit the new filter if you want other users to be able to use it. You can use these filters for global editing groups of links (this feature can be found in the Links Database window) or for controlling the display styles of links with different status flag settings, e.g.:
In the display properties for the links it is also possible to colour the links according to the frequency band of the link if desired. This is accessed in the normal way for display properties by double clicking on the item in the display tree list
4
Visibility tool
The Site Visibility tool can be useful when positioning sites for microwave link connectivity purposes (it can also be used to give a quick indication of coverage). The tool draws a coloured area on the 2D View showing the area over which a selected site has an unobstructed view. To display the visibility area from a site click on the Site Visibility button on the left-hand toolbar of the 2D View window. Then click once on the site you want to display visibility for, drag the mouse out to the radius over which to calculate and then click again. You will be prompted to select the calculation resolution, select it and the visibility will be calculated and drawn.
NOTE If you move a site the visibility is automatically recalculated and redrawn. This feature allows the visibility to be used to fine-tune the target location of a site. The visibility is calculated for certain default Tx and Rx antenna heights and earth curvature. To change these as well as the colour go to the display tree list and double-click on the visibility item to see its properties. If you have change the properties refresh the screen for these to take effect.
NOTE If you want different properties for each site then you must remove the “Use Settings as default” check-box.
5
Height Profiler
The 2D view is limited by the fact that it only provides a plan view of the terrain and clutter of an area. The latter is overcome by the Height Profile window, in which a two-dimensional crosssection between two points can be extracted from the map view. This feature is accessed through the Height Profile option under the View menu and is useful for confirming microwave Line-of-Sight or for analysing possible terrain/clutter causes for predicted coverage results.
Before using the tool, it is important to configure the window’s properties in order for the diagnosis to take into consideration required criteria.
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Properties Clicking on this icon brings up the properties window. The general parameters used to configure the height profile are set here.
Diffraction loss will depend on the type of terrain and vegetation. For a given path ray clearance, the diffraction loss will vary from a minimum value for a single knife-edge obstruction to a maximum for a smooth spherical Earth. Within the tool, diffraction loss may be calculated in a number of ways. This is set through the Preferences dialogue found under the File menu and seen here on the left. You have a choice of using a terrain averaging method (best used when considering losses greater than 15dB) or one of four diffraction algorithms supplied with Asset. Note: A full description of these diffraction models are described in the Asset User Reference Manual. The diffraction loss over average terrain is computed for the profile window, using the values set in the General tab and those from the profile itself. These include:
Terminal heights, i.e. BTS to mobile station Frequency band Fresnel Zone Tallest obstruction above the line of sight Distance between the terminals Distance from both terminals to the tallest obstruction.
The clutter categories used within the tool are used simply to describe the distribution of land usage over a region. These categories have no associated height, unless provided with building raster or vector map data. The Clutter tab allows the clutter heights as defined in the Prediction Models to be added to the profile. These are then considered in the path clearance and used to calculate the new approximate diffraction loss. The clutter classes found along the profile can be displayed by checking the appropriate box. The colour associated with each clutter type is changed through the Display List menu within the 2D View. Once the appropriate settings have been configured click on OK to save these and to proceed with using the Height Profile. The profiler can be used in three modes:
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Site to Point
Click on the starting site in the 2D View and then drag the mouse round to the point of interest. As the mouse moves the height profile will be dynamically updated to show the profile from the site to the current mouse location. To confirm that the displayed profile is the one you require click a second time on the desired location.
Site to Site
This mode of operation is similar to the one above, but intended to provide profiles between sites. Select the starting site and then drag the mouse round the view. The profile will ‘snap’ to the nearest site location. Confirm the selection by clicking on the end site.
Point to Point
In this mode neither end of the profile needs to be located at a cell site. In essence it provides the terrain profile between two points. Click on the starting location, move the mouse to the end location and click again.
Cancel
When finished viewing different profiles, it is necessary to disable the profile selection from the 2D view. This avoids further undesired profiles being extracted when moving around the map view.
Additional Toolbar Functions Key
Opens up a legend listing the clutter classes and their respective colours.
Fresnel Zone
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Displays the Fresnel zone for the current profile according to parameters set in the Properties window.
Analysing The Profile
Across the bottom of the window, information relating to the highest obstruction or clearance, the horizontal distance between the two points and the approximated signal (diffraction) loss of the profile are given. The vertical red lines describe the calculated diffraction (knife) edges. In the example below, the predicted signal levels may be under estimated, as the computed diffraction loss may be too high i.e. large number of knife-edges. This may be overcome by changing the diffraction algorithm and/or merging knife-edges in the Prediction Model dialogue (to be covered later).
Further to this, one can see this particular link path would not work at the antenna heights used. The Fresnel zone is fully obstructed.
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Exercise 8: Microwave Link Planning
For your GSM1800 network create a link network to connect your sites back to the BSC and MSC. Check each link to make sure it has a Line-of-Sight and that the 60% Fresnel zone is clear at 38GHz. Take one of the links and carry out a full link budget analysis using the RF parameters provided by your trainer. Adjust the Antenna gains until the link has an availability of better than 99.99%.
13 G ENERATING R EPORTS & P LOTS 1
Introduction
ASSET includes a number of report generation tools (some of which we have already seen earlier in the course) as well as printing/plotting facilities. This section covers the reporting facilities we have not yet examined and the printing facilities.
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Site Reporter
The Site Reporter allows the user to select a wide range of data fields from the Site Database and create a text file report of these fields. To start the Site Reporter select Asset Reports Site Reporter:
Simply select the fields you want included in the report by clicking on the relevant check-boxes. As with most features in Asset it is possible to generate a report for a specific group of sites by specifying a site filter from the list-box at the top of the window. Click Generate to view the resulting report:
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Link Reporter
The Link Reporter provides a similar capability to the Site Reporter but the fields are related to the links defined in the database. To start the Link Reporter go to Asset Reports Link Reporter
As with the Site Reporter simply select the fields you want included in the report by clicking on the relevant check-boxes. Again it is possible to generate a report for a specific group of sites by specifying a site filter from the list-box at the top of the window. Click Generate to view the resulting report:
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Cell Info Reporter
The Cell Info reporter is different in operation to the Site and Link Reporters. The Cell Info reporter is based on the Cell Info display feature looked at earlier during the frequency planning session (see page 99). This reporter can be started from Asset Reports Cell Info.
The set up for this feature is the same as that for the Cell Info display feature. There are two facilities provided by this feature: 1
Searching for cells with Co or Adjacent channels to the target cell.
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Searching for cells with specific carriers assigned.
Search by Cell Identity: Lets look at the first of these options. Searching by Cell Identity makes it possible to enter a cell name in the Cell Identity field and indicate whether to search for other cells with co-channel allocations or adjacent channels. Matching cells will be displayed in the lower pane of the window together with any cell parameters selected in the Cell Parameter page. For example here we have carried out a search for all cells with adjacent channels to those assigned to Site0A (channels 10 and 32 are assigned to Site0A):
In this example we also have selected BSIC and LAC for display from the Cell Parameters page by entering a “*” in the appropriate box, e.g.:
The number of sites considered in the search may be limited through the use of filters. Simply move to the Filter page and select the appropriate filter from the drop down list.
Search by Carrier: With the second option (Search by Carrier), it is possible to find all cells using specified carriers. A wildcard “*” can be used to display all the carriers on the filter of cells selected. For example the following displays all cells with a BCCH on carrier 1:
The resulting information can be stored to a text file for future reference by clicking the Export button.
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Change Report
This window lists all changes that have been applied to the database, but not yet committed. This is a useful feature to see whether any of the changes that you have performed with the intention of other users being able to see it, have not been committed. This dialogue is accessed through Asset Reports Change Report and is shown below:
The button offers you a way of copying the information displayed in the window, so that it can be pasted into a document and from this a hard copy can be produced.
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Printing/Plotting
Asset makes use of the standard Windows NT printer and plotter drivers and as such printing and plotting is very much like any other Windows application. By default the print function will print all of the items currently shown in the 2D View with the same colours and other properties – i.e. the printing is What-You-See-Is-What-You-Get. At present though all plots are square – if the view you are plotting is not square then the print will print the extra area required to make the plot square. The printing buttons are located along the top of the 2D View and are shown and described below:
Print Legend Used to arrange the general layout of data on the final document such as the title and legend.
Enter the various pieces of text information that you want to appear on the plot in the Legend entries. You can specify a custom logo by clicking the Select button and then specifying a Windows Bitmap (.bmp) file containing the logo image. If you need to plot to a specified scale (e.g. if you are plotting on transparency in order to overlay coverage information onto paper maps) then select the Print to Scale option and enter the scale you require. It can often be useful to display the map grid in the 2D View and plot this as well in order to simplify registration of a transparency overlay with the paper map. Finally, if you want to remove certain items from the plot legend but still have them appear in the final document, this can be achieved using the Customised Key option. Select Customised Key check box and then click Key >> to see a list of the available items.
In the above example the height (i.e. terrain) data will appear in the plot but the list of colours associated with different heights will be excluded from the key, reducing considerably the overall size of the list. Page Setup This button provides access to the Windows printer selection and paper layout set-ups. Here one specifies the page orientation, size, source and margins. These settings default to those assigned by the Window’s printer driver. Print Allows the printer, its properties, and the number of copies to be set. Once satisfied with the settings, printing can commence with the currently defined print legend and options. Print Preview Provides an on screen preview of what the final plot will look like. Print Pre-Defined Area
Used to select an area in the 2D View for printing, by enclosing the required area in a user-definable box. The print preview window is immediately launched after its selection.
