Atoll comes with GSM/GPRS/EDGE station templates, but you can also create and modify station templates. The tools for working with station templates can be found on the Radio toolbar (see Figure 6.8).
Figure6.8: The Radio toolbar
In this section, the following are explained:
• "Creating or Modifying a Station Template"
Creating or Modifying a Station Template
Creating or Modifying a Station Template
When you create a station template, Atoll bases it on the station template selected in the Station Template Properties dialogue. The new station template has the same parameters as the one it is based on. Therefore, by selecting the existing station template that most closely resembles the station template you want to create, you can create a new template by only modifying the parameters that differ.
As well, you can modify the properties of any station template.
To create or modify a station template:
1. In the Radio toolbar, click the arrow to the right of the list.
2. Select Manage Templates from the list. The Station Template Properties dialogue appears.
3. You can now create a new station template or modify an existing one:
- To create a new station template: Under Station Templates, select the station template that most closely resembles the station template you want to create and click Add. The Properties dialogue appears.
- To modify an existing station template: Under Station Templates, select the station template whose properties you want to modify and click Properties. The Properties dialogue appears.
4. Click the General tab of the Properties dialogue. In this tab (see Figure 6.9), you can modify the following: the Name of the station template, the number of Sectors, each with a transmitter, the Hexagon Radius, i.e., the theoretical radius of the hexagonal area covered by each sector, the HCS Layer, the Cell Type, the Max. TRXs/Sector, the Min. Range, the Max. Range, and the BSIC Domain.
Figure6.9: Station Template Properties dialogue – General tab
- Under Main Antenna, you can modify the following: the antenna Model, 1st Sector Azimuth, from which the azimuth of the other sectors are offset to offer complete coverage of the area, the Height of the antenna from the ground (i.e., the height over the DTM; if the transmitter is situated on a building, the height entered must include the height of building), the Mechanical Downtilt, and the Additional Electrical Downtilt.
- Under Propagation, you can modify the following: the Propagation Model, Radius, and Resolution for both the Main Matrix and the Extended Matrix. For information on propagation models, see Managing Calculations in Atoll.
5. Click the Transmitter tab. In this tab (see Figure 6.10), you can modify the following:
- Under Transmission, you can select to enter either Power and Total Losses or EIRP (Effective Isotropically Radiated Power). If you select EIRP, you can enter the value yourself, without defining power and losses for the transmitter.
If you select Power and Total Losses, Atoll calculates losses and noise according to the characteristics of the equipment assigned to the transmitter. Equipment can be assigned using the Equipment Specifications dialogue which appears when you click the Equipment button. Atoll will calculate the EIRP with the following formula:
EIRP = Power + Gain - Losses
For information on the Equipment Specifications dialogue, see "Transmitter Description".
Figure6.10: Station Template Properties dialogue – Transmitter tab
If you want transmitters created with this station template to be active by default, select the Active check box.
- Transmitter Type: If you want Atoll to consider transmitters created using this template as potential servers as well as interferer(s), set the transmitter type to Intra-Network (Server and Interferer). If you want Atoll to consider transmitters created using this template only as interferers, set the type to Extra-Network (Interferer Only). No coverage for an Interferer Only transmitter will be calculated for coverage predictions.
This enables you to model the co-existence of different networks in the same geographic area. For more information on studying interference between co-existing networks, see "Modelling the Co-existence of Networks".
6. Click the Configurations tab. In this tab (see Figure 6.11), you select the configuration used for GSM and GPRS/EDGE stations.
- Under GPRS/EDGE Properties, you must select the GPRS/EDGE Transmitter check box if the transmitters are going to be packet-switched capable transmitters, select a Coding Scheme Configuration from the list. For information on creating a coding scheme configuration, see "Coding Scheme Configuration".
Note: When you model EDGE Evolution on the transmitter side Atoll has to consider:
- The support of high order modulations and the use of turbo codes in specific coding schemes which can be found in the selected GPRS/EDGE Configuration.
In addition, EDGE Evolution can be modelled on the terminal side through:
- The support of dual antenna terminals (Mobile Station Receive Diversity) and enhanced single antenna terminals (Single Antenna Interference Cancellation). Atoll offers a statistical modelling of these through the use of an EDGE evolution configuration, with the effect of SAIC or diversity already included both in the coding scheme admission thresholds and on the throughput versus C (or C/I) graphs.
- The support of multi-carriers which can be set up on the terminal side.
For more information, see "Creating or Modifying a GSM/GPRS/EDGE Terminal".
- For all transmitters, you can select a codec configuration from the list. For information on creating a coding scheme configuration, see "Codec Configuration".
Figure6.11: Station Template Properties dialogue – Configurations tab
7. Click the Neighbours tab. In this tab (see Figure 6.12), you can modify the Max Number of Intra-Technology Neighbours and the Max Number of Inter-Technology Neighbours. For information on defining neighbours, see "Planning Neighbours".
Figure6.12: Station Template Properties dialogue – Neighbours tab
8. Click the Other Properties tab. The Other Properties tab will only appear if you have defined additional fields in the Sites table, or if you have defined an additional field in the Station Template Properties dialogue.
9. When you have finished setting the parameters for the station template, click OK to close the dialogue and save your changes.
• "Copying Data from One Station Template to Another"
Copying Data from One Station Template to Another
Copying Data from One Station Template to Another
You can copy properties from one template to another template by using the Station Templates table.
To copy properties from one template to another template:
1. Click the Data tab in the Explorer window.
2. Right-click the Transmitters folder. The context menu appears.
3. Select Network Settings > Station Templates from the context menu. The Station Templates table appears.
4. In the Stations Templates table, copy the settings in the row corresponding to the station template you want to copy from and paste them into the row corresponding to the station template you want to modify.
• "Modifying a Field in a Station Template"
Modifying a Field in a Station Template
Modifying a Field in a Station Template
To modify a field in a station template:
1. In the Radio toolbar, click the arrow to the right of the list.
2. Select Manage Templates from the list. The Station Template Properties dialogue appears.
3. Select the template in the Available Templates list.
4. Click the Fields button.
5. In the dialogue that appears, you have the following options:
- Add: If you want to add a user-defined field to the station templates, you must have already added it to the Sites table (for information on adding a user-defined field to a table, see "Adding a Field to an Object Type’s Data Table") for it to appear as an option in the station template properties. To add a new field:
i. Click the Add button. The Field Definition dialogue appears.
ii. Enter a Name for the new field. This is the name that will be used in database.
iii. If desired, you can define a Group that this custom field will belong to. When you open an Atoll document from a database, you can then select a specific group of custom fields to be loaded from the database, instead of loading all custom fields.
iv. In Legend, enter the name for the field that will appear in the Atoll document.
v. For Type, you can select from Text, Short integer, Long integer, Single, Double, True/False, Date/Time, and Currency. If you choose text, you can also set the field Size (in characters), and create a Choice list, by entering the possible selections directly in the Choice list window and pressing ENTER after each one.
vi. Enter, if desired, a Default Value for the new field.
vii. Click OK to close the Field Definition dialogue and save your changes.
- Delete: To delete a user-defined field:
i. Select the user-defined field you want to delete.
ii. Click the Delete button. The user-defined field appears in strikethrough. It will be definitively deleted when you close the dialogue.
- Properties: To modify the properties of a user-defined field:
i. Select the user-defined field you want to modify.
ii. Click the Properties button. The Field Definition dialogue appears.
iii. Modify any of the properties as desired.
iv. Click OK to close the Field Definition dialogue and save your changes.
6. Click OK.
• "Deleting a Station Template".
Deleting a Station Template
Deleting a Station Template
To delete a station template:
1. In the Radio toolbar, click the arrow to the right of the list.
2. Select Manage Templates from the list. The Station Template Properties dialogue appears.
3. Under Station Templates, select the station template you want to delete and click Delete. The template is deleted.
In Atoll, a station is defined as a site with one or more transmitters sharing the same properties. With Atoll, you can create a network by placing stations based on station templates. This allows you to build your network quickly with consistent parameters, instead of building the network by first creating the site, then the transmitters, and finally by adding subcells and TRXs.
To place a new station using a station template:
1. In the Radio toolbar, select a template from the list.
2. Click the New Transmitter or Station button () in the Radio toolbar.
3. In the map window, move the pointer over the map to where you would like to place the new station. The exact coordinates of the pointer’s current location are visible in the Status bar.
4. Click to place the station.
Tips:
• To place the station more accurately, you can zoom in on the map before you click the New Station button. For information on using the zooming tools, see "Changing the Map Scale".
• If you let the pointer rest over the station you have placed, Atoll displays its tip text with its exact coordinates, allowing you to verify that the location is correct.
You can also place a series of stations using a Atoll template. You do this by defining an area on the map where you want to place the stations. Atoll calculates the placement of each station according to the defined hexagonal subcell radius in the station template. For information on defining the subcell radius, see "Creating or Modifying a Station Template".
To place a series of stations within a defined area:
1. In the Radio toolbar, select a template from the list.
2.Click the Hexagonal Design button (), to the left of the template list. A hexagonal design is a group of stations created from the same station template.
Note: If the Hexagonal Design button is not available (), the hexagonal subcell radius for this template is not defined. For information on defining the cell radius, see "Creating or Modifying a Station Template".
3. Draw a zone delimiting the area where you want to place the series of stations:
a. Click once on the map to start drawing the zone.
b. Click once on the map to define each point where the border of the zone changes direction.
c. Click twice to finish drawing and close the zone.
Atoll fills the delimited zone with new stations and their hexagonal shapes. Station objects such as sites and transmitters are also created and placed into their respective folders.
You can work with the sites and transmitters in these stations as you work with any station object, adding, for example, another antenna to a transmitter.
Placing a Station on an Existing Site
Placing a Station on an Existing Site
When you place a new station using a station template as explained in "Placing a New Station Using a Station Template", the site is created at the same time as the station. However, you can also place a new station on an existing site.
To place a station on an existing site:
1. On the Data tab, clear the display check box beside the Hexagonal Design folder.
2. In the Radio toolbar, select a template from the list.
3. Click the New Station button () in the Radio toolbar.
4. Move the pointer to the site on the map. When the frame appears around the site, indicating it is selected, click to place the station.
A base station consists of the site, one or more transmitters, various pieces of equipment, and radio settings such as, for example, subcells. You will usually create a new base station using a station template, as described in "Placing a New Station Using a Station Template". This section describes the following elements of a base station and their parameters:
Definition of a Base Station
• "Site Description"
Site Description
Site Description
The parameters of a site can be found in the site’s Properties dialogue. The Properties dialogue has one tab:
• The General tab (see Figure 6.2):
Figure6.2: New Site dialogue
- Name:Atoll automatically enters a default name for each new site. You can modify the default name here. If you want to change the default name that Atoll gives to new sites, see the Administrator Manual.
- Position: By default, Atoll places the new site at the centre of the map window. You can modify the location of the site here.
Tip: While this method allows you to place a site with precision, you can also place sites using the mouse and then position them precisely with this dialogue afterwards. For information on placing sites using the mouse, see "Moving a Site Using the Mouse".
- Altitude: The altitude, as defined by the DTM for the location specified under Position, is given here. You can specify the actual altitude under Real, if you wish. If an altitude is specified here, Atoll will use this value for calculations.
- Comments: You can enter comments in this field if you wish.
• "Transmitter Description"
Transmitter Description
Transmitter Description
The parameters of a transmitter can be found in the transmitter’s Properties dialogue. When you create a transmitter, the Properties dialogue has four tabs: the General tab, the Transmitter tab, the TRXs tab, the AFP tab (see "Allocating Frequencies, BSICs, HSNs, MALs, and MAIOs"), and the Configurations tab. Once you have created a transmitter, its Properties dialogue has four additional tabs: the Intra-Technology Neighbours tab (see "Allocating or Deleting Neighbours Using the Intra-Technology Neighbours Tab of the Transmitter Properties Dialogue"), the Inter-Technology Neighbours tab), the Propagation tab (see Managing Calculations in Atoll), and the Display tab (see "Display Properties of Objects").
• The General tab:
- Name: By default, Atoll names the transmitter after the site it is on, adding an underscore and a number. You can enter a name for the transmitter, but for the sake of consistency, it is better to let Atoll assign a name. If you want to change the way Atoll names transmitters, see the Administrators Manual.
- ID: You can enter an ID for the transmitter. This is a user-definable network-level parameter for cell identification.
- Site: You can select the Site on which the transmitter will be located. Once you have selected the site, you can click the Browse button () to access the properties of the site on which the transmitter will be located. For information on the site Properties dialogue, see "Site Description". You can click the New button to create a new site on which the transmitter will be located.
-Under HCS Layer:
- You can select the HCS Layer (Hierarchical Cell Structure layer) for the transmitter.
- Once you have selected the HCS layer, you can click the Browse button () to open the properties of the HCS layer.
- You can enter a specific HCS layer threshold for this transmitter. The threshold defined in the HCS Layer properties is considered only if no value is entered in this field.
For information on the HCS layer Properties dialogue, see "Setting HCS Layers".
- Under Antenna Position, you can modify the position of the antennas (main and secondary):
- Relative to Site: Select this option if you want to enter the antenna positions as offsets with respect to the site location, and then enter the x-axis and y-axis offsets, Dx and Dy, respectively.
- Coordinates: Select this option if you want to enter the coordinates of the antenna positions, and then enter the x-axis and y-axis coordinates, X and Y, respectively.
• The Transmitter tab (see Figure 6.3):
Figure6.3: Transmitter dialogue - Transmitter tab
- Active: If this transmitter is to be active, you must select the Active check box. Active transmitters are displayed in red in the Transmitters folder of the Data tab.
Note: Only active transmitters are taken into consideration during calculations.
- Transmitter Type: If you want Atoll to consider the transmitter as a potential server as well as an interferer, set the transmitter type to Intra-Network (Server and Interferer). If you want Atoll to consider the transmitter only as an interferer, set the type to Extra-Network (Interferer Only). No coverage for an Interferer Only transmitter will be calculated for coverage predictions.
This feature enables you to model the co-existence of different networks in the same geographic area. For more information on how to study interference between co-existing networks, see "Modelling the Co-existence of Networks".
- Transmission: Under Transmission, you can select to enter either Power and Total Losses or EIRP (Effective Isotropically Radiated Power). If you select EIRP, you can enter the value yourself, without defining power and losses for the transmitter.
If you select Power and Total Losses, Atoll calculates losses and noise according to the characteristics of the equipment assigned to the transmitter. Equipment can be assigned using the Equipment Specifications dialogue which appears when you click the Equipment button. Atoll will calculate the EIRP with the following formula:
EIRP = Power + Gain - Losses
-On the Equipment Specifications dialogue (see Figure 6.4), the equipment you select and the gains and losses you define are used to initialise total transmitter DL losses. UL losses are not modelled in GSM/GPRS/EDGE projects.
-TMA: You can select a tower-mounted amplifier (TMA) from the list. You can click the Browse button () to access the properties of the TMA. For information on creating a TMA, see "Defining TMA Equipment".
-Feeder: You can select a feeder cable from the list. You can click the Browse button () to access the properties of the feeder. For information on creating a feeder cable, see "Defining Feeder Cables".
-BTS: You can select a base transceiver station (BTS) equipment from the BTS list. In GSM, only the downlink losses are modelled. You can click the Browse button () to access the properties of the BTS. For information on creating a BTS, see "Defining BTS Equipment".
-Feeder Length: You can enter the feeder length at transmission.
- Miscellaneous Losses: You can enter miscellaneous losses at transmission.
- Receiver Antenna Diversity Gain: This field is not used for GSM/GPRS/EDGE projects.
- Loss Related to Repeater Noise Rise: This field is not used for GSM/GPRS/EDGE projects.
Figure6.4: The Equipment Specifications dialogue
Note: You can modify the Total Losses at transmission if you wish. Any value you enter must be positive.
- Antennas:
- Height/Ground: The Height/Ground box gives the height of the antenna above the ground. This is added to the altitude of the site as given by the DTM. If the transmitter is situated on a building, the height entered must include the height of building.
- Main Antenna: Under Main Antenna, the type of antenna is visible in the Model list. You can click the Browse button () to access the properties of the antenna. The other fields, Azimuth, Mechanical Downtilt, and Additional Electrical Downtilt, display additional antenna parameters.
- Under Secondary Antennas, you can select one or more secondary antennas in the Antenna column and enter their Azimuth, Mechanical Downtilt, Additional Electrical Downtilt, and % Power, which is the percentage of power reserved for this particular antenna. For example, for a transmitter with one secondary antenna, if you reserve 40% of the total power for the secondary antenna, 60% is available for the main antenna.
For information on working with data tables, see "Working with Data Tables".
- Under GPRS/EDGE Properties, you must select the GPRS/EDGE Transmitter check box if the transmitter is going to be a packet-switched capable transmitter. You can select a Coding Scheme Configuration from the list. You can click the Browse button () to access the properties of the configuration. For information on creating a coding scheme configuration, see "Coding Scheme Configuration".
Note: When you model EDGE Evolution on the transmitter side Atoll has to consider:
- The support of high order modulations and the use of turbo codes in specific coding schemes which can be found in the selected GPRS/EDGE Configuration.
In addition, EDGE Evolution can be modelled on the terminal side through:
- The support of dual antenna terminals (Mobile Station Receive Diversity) and enhanced single antenna terminals (Single Antenna Interference Cancellation). Atoll offers a statistical modelling of these through the use of an EDGE evolution configuration, with the effect of SAIC or diversity already included both in the coding scheme admission thresholds and on the throughput versus C (or C/I) graphs.
- The support of multi-carriers which can be set up on the terminal side.
For more information, see "Creating or Modifying a GSM/GPRS/EDGE Terminal".
- Under GSM Properties, you can select Codec Configuration from the list. You can click the Browse button () to access the properties of the codec configuration assigned to the GSM transmitter. For information on creating a coding scheme configuration, see "Codec Configuration".
• "Subcell Definition"
Subcell Definition
Subcell Definition
In Atoll, a subcell refers to the characteristics of a group of TRXs on a transmitter sharing the same radio characteristics, the same quality (C/I) requirements, and other settings.
The initial settings of a subcell of a transmitter depend on the cell type selected for the transmitter. Assigning a different cell type to a transmitter changes the characteristics of the subcells (for information on the cell type, see "Cell Types"). Once the cell type has been selected, the initial values of the subcell, taken from the cell type, can be modified, with the exception of the TRX type. If you modify the cell type afterwards, for all transmitters based on that cell type, Atoll offers you the choice of keeping current parameters or resetting them to the new cell type parameters.
The properties related to subcells are found on the TRXs tab of the Properties dialogue of the transmitter to which it is assigned.
The TRXs tab has the following subcell-related options:
• Under Cell Type:
- Name: You can select the name of the Cell Type on which the transmitters subcells will be based from the list. You can click the Browse button () to access the properties of the cell type.
- Relevant Frequency Band: The Relevant Frequency Band displays the frequency band that will be used to calculate the path loss matrix for the transmitter. The frequency band is the band used by the BCCH TRX type under Subcell (TRX groups) Settings on the same tab.
- Cell Reselect Offset: The offset which is applied to the reception threshold to determine the Reselect Criterion (C2) in idle mode. The C2 value is used to select a server and as a display parameter in coverage predictions.
- Max. No. of TRXs: The maximum number of TRXs that the transmitter can have. The value entered here will be taken instead of the global value defined during dimensioning.
• Under Extended Cells, you can enter the minimum and maximum range of an extended subcell. Normally, coverage of a GSM cell is limited to a 35 km radius. Extended GSM cells enable the operator to overcome this limit by taking this delay into consideration when defining the timing advance for users in the extended cells. Extended cells may cover distances from 70 to 140 km from the base station. For more information on extended cells, see "Defining Extended Cells".
- Min. Range: You can enter the distance from the transmitter at which coverage begins.
- Max. Range: You can enter the maximum range from the transmitter of its coverage.
Note: Although coverage may be restricted within the set minimum range and maximum range, interference from the transmitter is not limited within these ranges.
• Under Identification:
- BSIC Domain: You can select the BSIC (Base Station Identity Code) domain from the list. You can click the Browse button () to access the properties of the selected BSIC domain. For information on BSIC domains, see "Defining BSIC Domains and Groups".
- BSIC: The BSIC (Base Station Identity Code) colour code is associated with a defined BCCH so that a mobile can identify the base station to which both a particular BCCH and BSIC are assigned. The BSIC is derived from the NCC (Network Colour Code) and the BCC (BTS Colour Code).
To assign a BSIC number to the current transmitter, you can assign a number from the BSIC Domain by selecting it from the list. You can also enter the BSIC number in the format NCC-BCC. When you click Apply, Atoll converts the entered NCC-BCC number into the single-number BSIC format. For information on the BSIC, see "Defining the BSIC Format".
- BCCH: The BCCH text box displays the frequency of the BCCH (TS0 of the BCCH TRX) of the current transmitter. If the BCCH subcell, under Subcell (TRX Groups) Settings on the TRXs tab, is in synthesized frequency hopping (SFH) mode, you can enter the MAL channel which will be TS0.
- NCC-BCC: The NCC (Network Colour Code), identifying the operator, and the BCC (BTS Colour Code), identifying the base station are displayed in the NCC-BCC text box. The NCC and BCC are integers from 0 to 7.
• Under Subcells, the information displayed depends on the type of subcell information selected from the Display list, Standard Data, Traffic Data, AFP Indicators:
- Standard: The information displayed is the standard information defining the subcell. The initial settings are from the selected cell type and can be modified with the exception of the TRX Type:
- TRX Type: The TRX Type can be one of the default TRX types available in the GSM/GPRS/EDGE project template:
BCCH: The broadcast control channel (BCCH) carrier
TCH: The default traffic (TCH) carrier
TCH_EGPRS: The EDGE traffic (TCH_EGPRS) carrier.
TCH_INNER: The inner traffic (TCH_INNER) carrier.
- Frequency Domain: The frequency domain assigned to the TRX group. Only channels belonging to this frequency domain will be allocated to TRXs of this group during manual or automatic frequency planning.
Note: The frequency domains assigned to the BCCH subcell and to the TCH subcell must reference the same frequency band, unless you are modelling dual-band transmitters. For information on dual-band transmitters, see "Advanced Modelling of Multi-Band Transmitters".
- Excluded Channels: The defined frequency domain can have, as part of its definition, a list of excluded channels. Addition excluded channels for this subcell can be added in the Excluded Channels column.
- Required TRXs: The number of TRXs required for the subcell. For subcells with the BCCH TRX Type, the number of requested TRXs must be "1," the default value. For subcells with the TCH, TCH_EGPRS or TCH_INNER TRX Type, the value in the Required TRXs column is a result of network dimensioning, which depends on the traffic demand and the required quality.
- Traffic Load: The Traffic Load indicates the usage rate of TRXs; its value must be from 0 to 1. The value in the Traffic Load column can be either user-defined or the result of network dimensioning, in which case it will be the same value for all subcells covering the same area (e.g. BCCH and TCH).
The traffic load is used to calculate interference and in automatic frequency planning.
- DL Power Reduction: The reduction of power relative to the transmitter power. The DL Power Reduction is used to model the power reduction of TCH TRXs, TCH_EGPRS and of TCH_INNER TRXs. TCH_INNER TRXs are concentric subcells, in other words, subcells that transmit a power lower than that used by the BCCH TRX and by TCH TRXs.
Note: DL power reduction can also be used to model in a simple way the coverage reduction of a 1800 subcell compared to the BCCH 900 subcell, assuming that all subcells are transmitting at the same power. Atoll also enables advanced multi-band transmitter modelling. For more information, see "Advanced Modelling of Multi-Band Transmitters" and the Administrator Manual.
- Reception Threshold (dBm): The reception threshold defines the minimum reception level for the subcell. I can be used as the minimum subcell reception sensitivity if the link budget is correctly defined.
- C/I Threshold (dB): The minimum signal quality for the TRX Type. The C/I Threshold can be used in interference studies and in the AFP.
- DTX Supported: The DTX Supported check box is selected if the subcell supports DTX (Discontinuous Transmission) technology. Subcells supporting DTX can reduce the interference they produce by the defined voice activity factor.
- Timeslot Configuration: The timeslot configuration defines the distribution of circuit, packet and shared timeslots for the subcell. For information on timeslot configurations, see "Timeslot Configurations".
- Hopping Mode: The frequency hopping mode supported by the selected TRX type. The hopping mode can be either "Base Band Hopping mode (BBH)" or "Synthesized Hopping mode (SFH)." If frequency hopping is not supported, select "Non Hopping."
- Allocation Strategy: The allocation strategy used during manual or automatic frequency planning. There are two available allocation strategies:
Free: Any of the channels belonging to the frequency domain can be assigned to TRXs.
Group Constrained: Only channels belonging to a same frequency group in the frequency domain can be assigned. You can use the Preferred Frequency Group to define the preferred group of frequencies when using the AFP.
- Max. MAL Length: The maximum length of the mobile allocation list (MAL), in other words, the maximum number of channels allocated to the TRXs of the subcell during automatic frequency planning if the Hopping Mode is either SFH (Synthesized Frequency Hopping) or BBH (Base Band Hopping) and if the Allocation Strategy is Free.
- HSN Domain: Only hopping sequence numbers (HSN) belonging to the selected HSN domain will be allocated to subcells during manual or automatic frequency planning. The HSNs are allocated if the Hopping Mode is either SFH (Synthesized Frequency Hopping) or BBH (Base Band Hopping).
- HSN: The hopping sequence number (HSN) of the subcell. All TRXs of the subcell have the same HSN. The HSN can be entered manually or allocated automatically. This parameter is used if the Hopping Mode is either SFH (Synthesized Frequency Hopping) or BBH (Base Band Hopping).
- Lock HSN: When the Lock HSN check box is selected, the subcell’s currently assigned HSN is kept when a new AFP session is started.
- Synchronisation: The value entered in the Synchronisation column is used during frequency hopping; frequency hopping is synthesized among all TRXs of subcells with the same string of characters in the Synchronisation column. By default, the name of the site is used as the value in the Synchronisation column, synchronising frequency hopping for all TRXs on the same site. However, you can, for example, enter different values for each subcell to define synchronisation at the subcell level, or different values for each group of sites to define synchronisation by sites group.
- Preferred Frequency Group: When the Group Constrained allocation strategy is selected, in any hopping mode (including non-hopping), the AFP tries to assign frequencies from the preferred group during automatic allocation. The preferred frequency group is a soft constraint used by the AFP to assign frequencies to TRXs. When the AFP is unable to assign a frequency from the preferred group, and allocates a frequency from outside the group, a corresponding cost is taken into account. The preferred group can also be the result of allocation if the AFP model is able to allocate patterns based on the azimuth.
- AFP Weight: Enter an AFP weight. The AFP weight is used to increase or decrease the importance of a subcell during automatic frequency planning. The value must be a real number. The higher the AFP weight is, the higher the constraint on the TRX type. The AFP weight artificially mulitplies the cost which has to be minimised by the AFP.
- % Max. Interference: The maximum level of interference allowable during automatic frequency planning. The interference is defined as a percentage of area or traffic, as defined during the calculation of the interference matrices.
- Mean Power Control Gain (dB): The average reduction in interference due to power control in downlink. This gain is used when calculating interference generated by the subcell. Interference generated by the subcell is reduced by this value during C/I calculations.
- Default TRX Configuration: The default TRX Configuration selected in this column is applied to all TRXs belonging to the subcell. By selecting the default TRX Configuration, the maximum number of coding schemes in GPRS and in EDGE is set at the TRX type level. You can also define the TRX Configuration for each TRX.
- EDGE Power Backoff (dB): The average power reduction for EDGE transmitters due to 8PSK, 16QAM and 32QAM modulations in EDGE. This has an impact on the EDGE service zone which can be seen in traffic analysis and EDGE predictions.
- Number of Antennas (Transmission Diversity): The number of antennas the subcell can use for transmission. In most cases, a transmitter will transmit with only one antenna, however, some transmitters are capable of transmission diversity. By transmitting on more than one antenna, the signal experiences a gain of 3 dB. An additional transmission diversity gain can be defined per clutter class in order to correctly model gain due to the environment.
- Lock the number of required TRXs: This option can be used by an AFP model which has the capability to optimise (i.e., increase or decrease) the number of required TRXs where the only goal is maximising the amount of correctly served traffic. In other words, you might have fewer TRXs than required if they are not subject to any interference and the amount of correctly served traffic will be larger. When you select this option, the number of required TRXs is blocked for that subcell.
Note: If some subcell fields are empty (e.g., HSN domain, frequency domain, C/I Threshold), Atolluses the default values of the selected Cell type. For more information, see "Creating a Cell Type".
- Traffic Data: The information displayed describes the traffic of the cell. Because subcells share the traffic of the transmitter, in most cases, the traffic data for all TRXs is displayed together. All fields can be modified with the exception of the TRX Type, Effective Rate of Traffic Overflow, and Traffic Load.
- TRX Type: The TRX Type can be one of the default TRX types available in the GSM/GPRS/EDGE project template:
BCCH: The broadcast control channel (BCCH) carrier
TCH: The default traffic (TCH) carrier
TCH_EGPRS: The EDGE traffic (TCH_EGPRS) carrier.
TCH_INNER: The inner traffic (TCH_INNER) carrier.
- Total Circuit Demand (Erlangs): The circuit demand indicates the amount of Erlangs necessary to absorb the circuit-switched demand. This value can be either user-defined or the result of a traffic capture, in which case it will be the same value for all subcells covering the same area (e.g., BCCH and TCH).
- Total Packet Demand (TS): The packet demand indicates the amount of timeslots necessary to absorb the packet-switched demand. This value can be either user-defined or the result of a traffic capture, in which case it will be the same value for all subcells covering the same area (e.g., BCCH and TCH).
Circuit and packet demands can be imported into this table from a real network. These value will then be taken into account for dimensioning or KPI calculation if these calculations are not based on the default traffic capture.
- Half-Rate Traffic Ratio (%): The percentage of half-rate voice traffic in the subcell. This value is used to calculate the number of timeslots required to respond to the voice traffic demand.
- Target Rate of Traffic Overflow (%): The target rate of traffic overflow is used during traffic analysis to distribute the traffic between subcells and layers. The traffic located in the inner zone or in the service zone of a high priority cell (see the figures below) contributes to the traffic demand of the inner subcell or the high priority cell respectively. If the target rate of traffic overflow is greater than 0, a part of this traffic is re-injected, so that it also contributes to the demand of outer zone (or to the low priority cell respectively). The key performance indicators calculation (and dimensioning process) transforms the traffic demand into a served demand on one hand and an effective overflow on the other hand. If effective overflow rates are higher than target overflow rates, it means there is a capacity reserve. If it is the other way around, it means that more TRXs are needed. If rates are equal, the network is correctly optimised.
Figure6.6: Overflow between concentric cells
Figure6.7: Overflow between HCS layers
Important: The target rate of traffic overflow and the half-rate traffic ratio must be the same for BCCH and TCH subcells. If the values are different for BCCH and TCH subcells, Atoll will use the values for the target rate of traffic overflow and the half-rate traffic ratio from the BCCH subcell.
- Effective Rate of Traffic Overflow (%): The percentage of traffic overflowing from a subcell. The effective rate of traffic overview is a result of the calculation of key performance indicators.
- Traffic Load: The Traffic Load indicates the usage rate of TRXs; its value must be from 0 to 1. The value in the Traffic Load column can be either user-defined or the result of network dimensioning, in which case it will be the same value for all subcells covering the same area (e.g. BCCH and TCH).
The traffic load is used to calculate interference and in automatic frequency planning.
- AFP Indicators: The information displayed comes from the results of an AFP model; it is displayed for informational purposes only and can not be edited.
- Total Cost: The total cost is the combination of the AFP Separation Cost, the Additional Cost, and the AFP Congestion cost.
- AFP Separation Cost: The separation cost is the cost to the system when separation rules are not respected between subcell pools. If separation constraints are violated, this has a direct effect on the interference level.
- Additional Cost: The additional cost is combination of other costs such as interference, the cost of carrying modifications, and not respecting the preferred TRX group.
- AFP Blocking Cost: The AFP blocking cost is the part of the cost where traffic is considered as blocked due to a lack of resources.
- AFP Congestion: The AFP congestion is the soft blocking cost, an estimation of the level of congestion for a pool of subcells (e.g., BCCH and TCH are considered as a pool of subcells since they are managed together). In other words, a highly congested pool of subcells will be a source of a high level of interference.
Note: The subcells of the entire GSM/GPRS/EDGE document are found in the Subcells Table: Standard Data. You can open the Subcells Table: Standard Data by right-clicking the Transmitters folder in the Data tab of the Explorer window and then selecting Network Settings > Subcells Table: Standard Data from the context menu. In addition, you can access specific views of the subcell table. The table containing the information regarding traffic data, or the AFP indicators, can be accessed by right-clicking the Transmitters folder in the Data tab of the Explorer window and then selecting Network Settings > Subcells Table: Traffic data, (or AFP Indicators,from the context menu.
• "TRX Definition".
TRX Definition
TRX Definition
In Atoll, the TRX refers to the transmission/reception card. In GSM/GPRS/EDGE projects, frequencies and channels are defined using TRXs. In non-hopping or base-band hopping mode, a single frequency or channel can be assigned to each TRX. In synthesised frequency hopping mode, more than one frequency can be assigned to each TRX.
The number of timeslots supported by a TRX defines the multiplexing factor of the frequency using that TRX.
In Atoll, TRXs are modelled using defined TRX types. Three TRX types are available in the GSM/GPRS/EDGE project template:
• BCCH: The broadcast control channel (BCCH) carrier
• TCH: The default traffic (TCH) carrier
• TCH_EGPRS: The EDGE traffic (TCH_EGPRS) carrier.
• TCH_INNER: The inner traffic (TCH_INNER) carrier.
The TRXs and their properties are found on TRXs tab of the Properties dialogue of the transmitter to which they are assigned.
Note: The TRXs of the entire GSM/GPRS/EDGE document are found in the TRXs Table. You can access the TRXs Table by right-clicking the Transmitters folder in the Data tab of the Explorer window and then selecting Network Settings > TRXs Table from the context menu.
The TRXs tab has the following TRX-related options:
• Under TRXs, the table lists each TRX allocated to the transmitter. The initial settings are from the selected cell type and can be modified:
- Index: This is the identification number of the TRX. The number must be an integer and can be user-defined or assigned automatically by Atoll when you close the dialogue.
- TRX Type: The TRX Type can be one of the default TRX types available in the GSM GPRS EDGE project template:
- BCCH: The broadcast control channel (BCCH) carrier
- TCH: The default traffic (TCH) carrier
- TCH_EGPRS: The EDGE traffic (TCH_EGPRS) carrier.
- TCH_INNER: The inner traffic (TCH_INNER) carrier.
- Channels: The channels allocated to the TRX. You must specify 1 channel per TRX if the hopping mode for the TRX type is "Non Hopping" or "Base Band Hopping," and more than one channel per TRX if the hopping mode for the TRX type is "Synthesized Hopping." You can enter channels directly (separating them with a comma, a semi-colon, or a space) or you can enter a range of channels separating the first and last channel with a hyphen (for example, entering "1-5" corresponds to "1 2 3 4 5"). You can also select a channel from the list which offers you channels from the frequency domain assigned to the TRX type that this TRX is based on.
- MAIO: The MAIO (Mobile Allocation Index Offset) is used in frequency hopping (BBH or SFH) to avoid intra-site collisions caused by two sites using the same or adjacent channels. This value is an integer ranging from 0 and N-1 (where "N" is the number of channels used in the hopping sequence). You can enter the MAIO or it can be allocated automatically using the AFP.
- Lock Channels and MAIO: When the Lock Channels and MAIO check box is selected, the TRX’s currently assigned channels and MAIO are kept when a new AFP session is started.
- TRX Configuration: The TRX Configuration selected defines the highest coding scheme index number possible in GPRS and in EDGE. For the TRX Configuration to be used fully, the terminal must be capable of using a coding index number that is as high as that of the TRX Configuration. Otherwise, capacity will be limited by the highest index number supported by the terminal.
- EDGE Power Backoff (dB): The average power reduction for EDGE transmitters due to 8PSK, 16QAM and 32QAM modulations in EDGE. This has an impact on the EDGE service zone which can be seen in traffic analyses and EDGE predictions.
- TRX Rank: The TRX Rank is determined by the AFP. It indicates the quality of that TRX. The higher the TRX rank, the higher the cost, in terms of the risk of interference. In other words, when you are trying to improve the solution proposed by the AFP tool, you must concentrate on the TRXs with the highest TRX rank first.
-Inter-technology DL Noise Rise: This noise rise represents the interference created by the mobiles of an external network on the mobiles served by this TRX on the downlink. This noise rise will be taken into account in all interference-based calculations involving this TRX. For more information on inter-technology interference, see "Modelling Inter-Technology Interference".
