bss - introduction to parameter planning

BSSPAR

Introduction to Parameter Planning

Training DocumentBSSPAR: CTXX 01

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The information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This document is intended for the use of Nokia Networks' customers only for the purposes of the agreement under which the document is submitted, and no part of it may be reproduced or transmitted in any form or means without the prior written permission of Nokia Networks. The document has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility when using it. Nokia Networks welcomes customer comments as part of the process of continuous development and improvement of the documentation.

The information or statements given in this document concerning the suitability, capacity, or performance of the mentioned hardware or software products cannot be considered binding but shall be defined in the agreement made between Nokia Networks and the customer. However, Nokia Networks has made all reasonable efforts to ensure that the instructions contained in the document are adequate and free of material errors and omissions. Nokia Networks will, if necessary, explain issues which may not be covered by the document.

Nokia Networks' liability for any errors in the document is limited to the documentary correction of errors. Nokia Networks WILL NOT BE RESPONSIBLE IN ANY EVENT FOR ERRORS IN THIS DOCUMENT OR FOR ANY DAMAGES, INCIDENTAL OR CONSEQUENTIAL (INCLUDING MONETARY LOSSES), that might arise from the use of this document or the information in it.

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Other product names mentioned in this document may be trademarks of their respective companies, and they are mentioned for identification purposes only.

Copyright © Nokia Oyj 2003. All rights reserved.

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Contents

1 Module Objectives........................................................5

2 Managed Object Classes And Parameter Sets..........6

3 BSC Level Parameters..................................................9

4 BCF Level Parameters................................................10

5 SEG, BTS, TRX, & RTSL Level Parameters..............11

6 ADJC, HOC, & POC Parameters................................12

7 Parameter Dictionaries...............................................137.1 Parameter Properties....................................................13

8 New Parameters & MML's..........................................15

9 Parameters & Timer Handling In PRFILE & PAFILE 169.1 PRFILE.........................................................................169.2 PAFILE..........................................................................17

10 Radio Network Configuration Management.............18

11 Background Database................................................2011.1 Background Loading Of Radio Network Plan...............21

12 Influence of Parameters During Call Phases...........22

13 Optional Features.......................................................24

14 Parameter Planning Impacts......................................2514.1 Channel Configuration..................................................2514.2 Idle Mode Operation.....................................................2514.3 Location Area Design....................................................2614.3.1 Paging vs. Location Updating Traffic............................2714.4 Handover And Power Control.......................................2714.4.1 Handover Types............................................................2814.4.2 Handover Criteria..........................................................2814.5 Adjacencies...................................................................29

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15 The BSS Parameter Planning Course.......................30

16 Key Learning Points...................................................31

17 Review Questions.......................................................32

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1 Module Objectives

At the end of the module, the participant will be able to:

Sketch a BSS Managed Object Hierarchy

Look up the parameters at each level, in a parameter dictionary

Identify parameter value ranges and default settings

Describe the use and benefits of a Background Database

Find the changes to objects, parameters, and MML commands, that occur with each BSS software release

Outline how the progression of a call through various phases, is influenced by the parameter settings for each MO class

Distinguish between the signalling in Idle mode and Dedicated mode

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2 Managed Object Classes And Parameter Sets

Radio Network Management of a cellular network is an important function to ensure that the network is performing all its tasks (e.g. call set-ups and handovers). RNW configuration is a continual process, where parameters may be changed often, because of maintenance work, optimisation, or site re-structuring.

The BSC radio network configuration management provides the operator with the means of controlling the radio network configuration data stored in the BSS Radio Network Configuration Database (BSDATA).

At the top-level user interface of the Nokia NMS, the management of various network elements and managed objects is structured in the hierarchical manner as shown below.

The Nokia NMS keeps a record of the parameters, states, configuration, and other relevant details of each cell in the database. In doing so, the operator can see via the NMS the current parameters. It is possible that different sets of parameters can be stored, building up a history of parameters.

Figure 1. Managed Object Hierarchy

The BSC is the parent object and has a number of child objects below it, some of which in turn have other children below them. The objects may represent real network elements (e.g. BCF, BTS) or functional objects that represent a function of a unit (e.g. Handover Control, Power Control).

The Managed Objects shown in Figure 1 are:

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ADJC FHS

RTSL

TRX HOC POC

BTS

HW-DB

BTS-SW

BCFMABA

BSC


Base Station Controller (BSC)

Base Control Function (BCF)

Base Station (BTS)

Transceiver (TRX)

Radio Timeslot (RTSL)

Handover Control Parameters per cell (HOC)

Power Control Parameters per cell (POC)

Adjacent Cell definitions (ADJC)

Frequency Hopping per cell (FHS)

BCCH Allocation Frequency List (BA)

Mobile Allocation Frequency List (MA)

The following operations on managed objects are supported:

1. Creating and removing objects (BCF, BTS, TRX, ADJC, BA, MA) in the database.

2. Changing of parameter values. The change is distributed and activated immediately.

3. Changes in the following objects are possible on-line, i.e., they do not cause any break in the service: BSC level parameters, handover and power control parameters, adjacent cell definitions, BA frequency lists, most of the cell parameters.

4. Managing frequency hopping (both baseband hopping and radio frequency hopping).

5. Interrogating parameter values.

6. Changing the administrative state (LOCKED/UNLOCKED) of the object (BCF, BTS, TRX, and RTSL).

7. Displaying the operational states of the functional entities (BCF, BTS, TRX, and RTSL).

In an enhancement 'Radio Network MML Improvement' there are improvements for Output Radio Network Configuration and Check Adjacent Cell Data MML commands. There is also a command for checking that the amount of IUO interfering cell definitions does not exceed the allowed maximum.

The enhancement 'Guard Channel Management' enables the use of guarded channels by controlling the maximum TRX transmit power. The FCC, the local regulator in the USA, has set certain emission limits for GSM1900 equipment to

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ensure that an operator on a band does not interfere with another operator on the adjacent bands.

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3 BSC Level Parameters

The BSC level parameters available in software release S10.5 are given in Section 2 of the BSS Radio Network Parameter Dictionary. There are 81 BSC level parameters relating to such things as quality alarms, AMH threshold, AMR performance, and FACCH call set up type allowed. The following is an example of a BSC level parameter definition, found in that dictionary.

Figure 2. A BSC Level Parameter

The meanings of the attributes of the above-mentioned parameter such as range, MML default will be discussed later in this module.

When a value is set for a BSC parameter, every cell under that BSC level uses the same value.

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4 BCF Level Parameters

A BCF is the logical supervision entity of a Base Station cabinet or site. It may contain a number of sectors (BTS's), but it is controlled by a single supervision link (BCFSIG LAPD). The BCF object contains BSC-specific radio network data. The BCF level parameters available in software release S10.5 are given in Section 3 of the BSS Radio Network Parameter Dictionary. There are 21 BCF level parameters. The following is an example of a BCF level parameter definition, found in that dictionary.

Figure 3. Example of a BCF Level Parameter

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5 SEG, BTS, TRX, & RTSL Level Parameters

The BTS, TRX, and RTSL level parameters available in software release S10.5 are given in Sections 5, 15, and 16 of the BSS Radio Network Parameter Dictionary. There are 176 BTS level parameters, 43 TRX level parameters, and 3 RTSL level parameters. The following is an example of a BTS level parameter definition, found in that dictionary.

Figure 4. Example of a BTS Level Parameter

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6 ADJC, HOC, & POC Parameters

Each adjacent cell (ADJC) object contains a description of one of the adjacent cells of a BTS. The handover control object (HOC) contains parameters controlling the handover procedure to and from a BTS. The power control object (POC) contains parameters controlling the power control procedure within a BTS.

The ADJC, HOC, and POC level parameters used in software release S10.5 are given in Section 6, 7, and 8 of the BSS Radio Network Parameter Dictionary. There are 44 ADJC level parameters, 73 HOC level parameters, and 39 POC level parameters.

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7 Parameter Dictionaries

The aim of a parameter dictionary is to assist radio network planning and optimisation engineers and other BSC users, to find certain BSS parameters, their meanings, properties, and relation to the GSM specifications. Parameters that are in other databases or files are not listed here.

There are two parameter dictionaries:

1. BSS Radio Network Parameter Dictionary that contains BSS parameters that can be manipulated using the MML commands given.

2. BSS and NSS RNW Parameter Dictionary that contains BSS and NSS parameters that can be manipulated using the NSS GUI or MML commands given.

The contents of both the above-mentioned dictionaries are changing with software releases, so always use the current relevant or latest versions of the parameter dictionaries available from NOKIA.

7.1 Parameter Properties

The parameter dictionary gives the following properties for each parameter:

• GSM reference: the name of standard in which the parameter is defined

• Q3 name: the name of the parameters that is used on the GUI

• Modification: states how the parameters can be modified, e.g. Online, Offline.

• Range: the range of values that the parameter can take

• MML default value: the default value of the parameter

• Description of what the parameter is used for in the BSS

• Related command(s) that perform a function relevant to this parameter

Note: Optional parameters are marked as OPTIONAL. The name of the optional feature that needs to be activated before the parameter is taken into use is given inside brackets. For example: OPTIONAL (Intelligent Shutdown with Timer Control) means that the parameter is optional and is in use when the feature Intelligent Shutdown with Timer Control is activated.

The activation of an OPTIONAL feature requires a SW licence and appropriate payment.

A typical parameter description given in the BSS and NSS Radio Network Dictionary is shown in Figure 5. The parameter definitions in this dictionary have additional properties such as NMS GUI Range.

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Figure 5. Example from the BSS and NSS RNW Parameter Dictionary

For most parameters, the default value is also the recommended value. An exception to this rule occurs when the default value has turned off a function or feature, which the operator wants to use. Another exception that applies to a small number of parameters is when experience has shown that the recommended value should be somewhat different to the default value.

The default and recommended values are tabulated in a spreadsheet tool that is available as a course resource to all participants.

The recommended parameter values are dependent on the network configuration, local conditions, and the operator. They may change from time to time.

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8 New Parameters & MML's

For every BSS software release, the parameter dictionary is updated. Objects, parameters, MML commands, may be added, removed, or modified.

New parameters are listed in the Section 'Summary of changes' at the beginning of the BSS Radio Network Dictionary. The new parameters are listed according to the RNW Managed Objects such as BSC, BTS, Adjacent Cell, etc.

Figure 6. Summary of changes

Changes to MML's are stated in the Section 'Changes in the command group'.

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9 Parameters & Timer Handling In PRFILE & PAFILE

Parameters are handled in the BSC with the aid of two parameter files:

PRFILE (General Parameter File) and

PAFILE (BSC Control Parameter File)

All the information about controlling the standard and optional features of the BSC is stored in the PRFILE. The file is administered (output the status, or make a modification) with the parameter handling MML program, command group WO.

The PAFILE is used for storing modified values of GSM-BSC parameters.

When an application is started, it first reads its parameters and timers from the PAFILE system file. If the PAFILE system file is empty, the application uses the general default values. The application arranges its internal parameters and timers according to the parameters and timers it has read from the PAFILE system file. If the system file contains values for a timer or a parameter used by the application, the application updates its values.

9.1 PRFILE

The BSC has a group of features that are not included in the basic software, but the customer can choose them to be included in the software (OPTIONAL features). There is also a group of features that are typical in all BSCs, but the extent of their use depends on the delivery (standard features).

All the information about controlling the above features is assembled in the BSC in the PRFILE (General Parameter File). One can modify and interrogate the contents of the file with the Parameter Handling MML (PRHAND) WO command group commands.

The command group menu is:

PARAMETER HANDLING COMMANDS

? ….. DISPLAY MENUC: ….. CHANGE PARAMETER VALUEI: ….. INTERROGATE PARAMETER VALUEP: ….. CREATE NEW PARAMETERL: ….. CREATE NEW PARAMETER CLASSO: ….. LIST AND OUTPUT OPTIONAL FEATURESF: ….. ACTIVATE/DEACTIVATE OPTIONAL FEATUREZ: ….. RETURN TO MAIN LEVEL

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The commands WOP CREATE NEW PARAMETER and WOL CREATE NEW PARAMETER CLASS are not available to the customer, and will probably be removed.

9.2 PAFILE

Parameter Administration provides the operator with the means of outputting and modifying the parameters and timers stored in the BSC Control Parameter File (PAFILE) in the BSC. Timers refer to GSM timers specified in the GSM specifications. It also provides and checks the restrictions and ranges of the parameters and timers, and stores the data in a system file. This file is supplied to all computer units. It is possible to output and modify these parameters and timers by means of the local MML.

PAFILE is used for storing modified values of GSM/BSC parameters. The record number and default value of each parameter are defined to the data types in the system environment. The GSM Timer and BSC Parameter Handling (GPAHAN) EG group commands are used to display and modify the values of GSM timers and BSC parameters.

If parameters or timers are modified with the MMI, the values will be stored in the system file. All applications are supposed to read the system file at regular intervals, as they have to update their relevant parameters. Thus, the modification of parameters is updated in all applications within 5 minutes.

The command group menu is:

GSM TIMER AND BSC PARAMETERS HANDLING COMMANDS

? ….. DISPLAY MENUO: ….. OUTPUT TIMERS/PARAMETERST: ….. MODIFY TIMERP: ….. MODIFY PARAMETERSZ: ….. RETURN TO MAIN LEVEL

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10 Radio Network Configuration Management

To run a mobile network requires managing a number of radio network elements and parameters controlling the functions of the radio network. As the radio network configuration is not static, but changes due to an increasing demand of coverage and capacity, fast and easy-to-use access to the configuration data is required. In addition, changes must not cause unnecessary service breaks.

The Radio Network Configuration Management in the BSC supports managing the radio network structure and data when:

Building the radio network

Expanding the network

Reconfiguring the network

Changing and optimising the functioning of the network

Deploying advanced features into the network

Most of the changes can be done on-line. This means that when making configuration or parameter changes concerning, e.g., a base station, other base stations are not disturbed.

The following Nokia NMS features are typical of those available for network implementation and status verification:

BSS Radio Network Management feature (optional)

Radio Network Manager application

LapD link Manager application

Autoconfiguration Pool Manager application

Uploading Managed Objects application

Printing Radio Network Parameters application

Background Database Manager application

MSC Radio Network Management feature (optional)

Radio Network Planning Data Transfer feature (optional)

Radio Network Plan Management feature (optional)

BSS Split feature

Network Editor feature

Inter-NMS Management feature (optional)

Graphical Adjacency Management feature (optional)

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Consistency Check feature (optional)

Additional Object Information feature (optional)

Transmission Node Management (optional)

Half Rate Management and Dual Rate Management

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11 Background Database

This feature enables the activation of several modified radio network parameters with one command. It can be used to implement a new frequency plan, for example. Parameters are modified to the background database and the whole database is activated by one command, which causes the swapping of the existing, and background databases. A restart to the Base Stations is needed for the changes to take effect.

Typical background parameters are:

BTS parameters:

Background Network Colour Code

Background BTS Colour Code

Background BTS Hopping Mode

Background Underlay BTS Hopping Mode

Background Hopping Sequence Number 1

Background Hopping Sequence Number 2

Background Underlay Hopping Sequence Number

Background MA Frequency list

Background Underlay MA Frequency list

Background MAIO Offset

Background Underlay MAIO Offset

Background MAIO Step

Background Underlay MAIO Step

Adjacent Cell parameters:

Background Network Colour Code

Background BTS Colour Code

Background Frequency Number of BCCH

TRX parameters:

Background Frequency

Background Optimum RX Level Uplink

Background TRX Frequency Type

Background Location Area Code of Interfering Cell 1 .. 10

Background Cell Identification of Interfering Cell 1 .. 10

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Background Level Adjustment of Interfering Cell 1 .. 10

Background C/I estimation weight parameter for Interfering Cell 1 .. 10

Background C/I estimation type for Interfering Cell 1 .. 10

Background direct access level (IUO) –109…-47 dBm

11.1 Background Loading Of Radio Network Plan

A major part of the frequency plan may require changing when new cells or channels are introduced into the network. Sometimes the entire plan is changed.

In an operational network, large changes are critical in regard to the disruption time. The new plan must be taken into use overnight without remarkable degradation in the service.

If the new parameter set is downloaded from the NMS in the conventional way (i.e., first locking a TRX, then changing its frequency, and finally unlocking it), the whole operation for a large network may take too long.

This feature offers a better way to make large changes to the network by downloading into a background database:

New data is downloaded down as a background operation without disturbing traffic. The data may come either from the NMS or from the BSC MML interface.

Downloading errors are tolerated. Possibly interrupted downloading may be repeated without disturbing traffic.

New data can be quickly activated in the network independently from the downloading. Thus, disturbance in the network is remarkably shorter.

Old data stays in the BSC as a back-up copy. It may be reactivated quickly.

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12 Influence of Parameters During Call Phases

The various call phases during a mobile originated call (MOC) are shown below. The parameters set by an operator have a major influence on the signalling that takes place during the call phases.

Figure 7. MOC Call Phases

There are 11 signalling procedures used, during the 15 possible phases of a basic call or other transaction, to provide CS speech or CS data services to a subscriber:

1. The paging procedure used to page a mobile to start the establishment of a mobile terminating call (MTC) with a mobile station (MS).

2. The channel required procedure starts the establishment of a mobile originating call (MOC) or to answer the PAGING REQUEST message.

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MS BTS BSC

AUTHENTICATION (SDCCH)Phase 2 : MM signalling

CIPHERING MODE (SDCCH)Phase 8 : Ciphering

TMSI REALLOCATION (SDCCH)

SETUP (SDCCH)

Phase 2 : MM signalling

CH. REQUEST (RACH)

IMMEDIATE ASSIGN(AGCH)

SERVICE REQUEST (SDCCH)

Phase 1 : Paging, initial MS

CH.RELEASEPhase 4 : Release

ALERTING & CONNECT (FACCH)Phase 2 : MM signalling

CONN. ACK. and MEASUREMENTPhase 15 : Conversation

DISCONNECT & RELEASE (FACCH) Phase 4 : Release

ASSIGNMENT (SDCCH-FACCH)Phase 3 : Basic assignment


3. Channel reservation procedure: used to request a dedicated signalling channel.

4. Channel activation procedure: After a successful reservation of a new channel, the BSC activates it by sending this message to the BTS.

5. The IMMEDIATE ASSIGN message facilitates assignment of the MS onto an SDCCH channel; the IMMEDIATE ASSIGN REJECT message facilitates refusal of the access sent by the MS.

6. The BSC starts the SCCP connection establishment procedure for the MS after receiving the ESTABLISH INDICATION message for the SDCCH establishment from the BTS.

7. Transmission of Transparent L3 messages is used in communication between the MS and the MSC. The BTS and the BSC forward the transparent messages.

8. Ciphering procedure is one of the security procedures designed to protect the subscriber identity and data.

9. Assignment procedure is used in assigning the MS to the correct TCH channel.

10. Channel release procedure is used for releasing a dedicated radio channel.

11. System information broadcasting procedure: The network periodically broadcasts messages on the BCCH. Some of this information influences the cell reselection made by the mobiles.

Cell reselection criterion C1 enables the MS to select a cell based on power level. The C2 reselection criterion may be defined by the operator. This enables avoiding undesirable reselection of a microcell in an environment where there is coverage by both a micro cell and a macrocell.

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13 Optional Features

With the Feature Management MML, the operator is able to list the feature options in the BSC and turn the operator-specific options in the BSC package on or off.

Feature management MML commands are listed below:

list optional features in the software package of the BSC and show if they are on or off

turn an OPTIONAL feature on

turn an OPTIONAL feature off

Each feature may be controlled by a number of additional feature specific parameters. These parameters are handled separately by using corresponding management commands.

The LIST command will show all optional features that are included in that particular SW package. The MML commands related to the feature are shown regardless of the state of the feature, so the operator will be able to see and modify a detailed feature parameter even when the feature has been turned off by the operator at the BSC level.

The TURN ON command will activate the feature to work according to the BSC level, or cell level, parameter settings related to this feature. The TURN OFF command will deactivate the feature in the BSC.

For example: Activate the E-OTD Position Based Services (WOA)

Activate the Position Based Services in BSC with control parameter PBS_USAGE. The parameter is in the off state after the software update and must be set on:

ZWOA: 2, 654, A;

Where:

Parameter class 2 is SYSTEM_FUNCT_CONFIGUR

Parameter number 654 is PBS_USAGE

Activate Feature A

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14 Parameter Planning Impacts

The parameter planning process is a vital step after the network roll out. Parameters available in the Nokia BSS are classified as follows:

BSC, BCF, and BTS parameters

BTS parameters for Adjacent Cell (ADJC)

BTS parameters for Handover Control (HOC)

BTS parameters for Power Control (POC)

BA and MA parameters

TRX & RTSL parameters

LCS related parameters

14.1 Channel Configuration

Firstly, the parameters related to logical channel configuration have to be set:

channel combinations

SDCCH & CCCH capacity, previously calculated

the traffic channels

14.2 Idle Mode Operation

Secondly, the parameters related to idle mode operation must be specified.

Idle mode signalling is directly relevant to LA design, and dedicated mode signalling is relevant to measurement reporting, HOC, and POC.

When the mobile station is in idle mode, it needs some information from the network in order to know the right frequencies, and find the right cells and channel configuration. This information is related to Radio Resource Management and to Mobility Management:

the access parameters to the PLMN

Location Area Identification, which is composed of the Mobile Network Code, the Mobile Country Code and Location Area Code (LAC)

cell identification code

There is also other information meant for Radio Channel Management:

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Base Station Identity Code (BSIC) including Network Colour Code (NCC) and Base Station Colour Code (BCC)

Once the base station is identified within the network, the frequencies must be set for each TRX:

initial frequency

The basic idea in the GSM system is that the mobile is always within the cell offering the best coverage and that the system knows where the MS is. In idle mode the mobility is ensured by setting the following criteria and timers:

Cell Selection, based on C1 or C2 comparison

Location Update

IMSI attach/detach

14.3 Location Area Design

A location area, as defined in GSM specifications, is the smallest area, into which a terminating call towards a mobile subscriber will be paged. In addition, a location area is the area in which a mobile needs not to update its location with its HLR.

Location update is performed in idle mode when the mobile is roaming into a cell having a different location area code (LAC). In connected mode, the mobile will update its location with the network as soon as it becomes idle again, i.e. after call completion.

While handover boundaries affect only mobiles that are in “connected mode”, location area boundaries affect all mobiles in the network, including the (many) idle mobiles.

Location updating causes signalling and processing load across the entire network hierarchy up to the mobile’s HLR. In case of foreign roaming mobiles (tourists), this is often even international signalling traffic. Therefore planning of location area boundaries should be well considered to avoid “oscillating” location updates along a heavily frequented road and to limit load on signalling channels.

Different MSCs cannot use the same LAC, otherwise the BSC will not know to which MSC the mobile belongs.

When planning a dual band or a microcellular network, LACs should be very carefully designed. It is recommended to define the co-located GSM900 and GSM1800 cells (the normal situation) in the same LAC – and of course in the same MSC. This can avoid additional location updates, which would cause very high SDCCH blocking.

Some networks, which have more than one vendor, might have separate MSCs for GSM900 and GSM1800 respectively. Then, to a dual band MS, every cell is

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at the LAC border. This implies that the amount of location updates is very large and consumes a large amount of SDCCH and signalling resources. More SDCCH needs to be assigned to the cells.

14.3.1 Paging vs. Location Updating Traffic

In a location area, there is a trade-off between paging traffic and location updating traffic. This means that concatenating e.g. a large city into a single location area will avoid any location updating traffic, but on the other hand causes a maximum in paging traffic, since every single terminating call within the area is broadcast to every single cell in the area. (Even several times per call attempt, depending on network parameters). This can cause significant traffic loads within the network.

The task is to find the optimum compromise between paging and location updating traffic. This is not trivial, since it is a function of call distribution, user mobility and call arrival statistics. This problem has been studied in literature. There is in fact an analytic minimum of signalling traffic. This minimum however is time-variant, a function of user densities, user mobility and call arrival rates. Therefore, it is not easily calculated. The figure below shows the basic dependency of paging and location updating traffic.

Paging LocUp

# of cells in Loc. area

signallingtraffic

optimum numberof cells in Loc. area

function of user density,cell size, call arrival rate ...function of

user mobility

Figure 8. Trade-off between location update and paging traffic

14.4 Handover And Power Control

For controlling the MS in dedicated mode, two main sets of parameters have to be carefully defined:

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Power Control parameters, threshold definitions to trigger power control commands, as well as the power range of the MS (UL power control) and BTS (DL power control if enabled)

Handover Control parameters, threshold definitions to trigger handover commands, for every type of handovers.

14.4.1 Handover Types

Handover is a basic functionality of cellular networks. Handovers can be distinguished as either intracell, intercell or inter-BSC handovers. Handovers within a single cell (i.e. changing timeslots and/or carrier frequencies) can be handled autonomously by the controlling BSC. Handovers between cells of the same BSC can also be handled by the BSC. Handovers between cells of different BSCs must be handled by the initiating MSC. Handovers between networks (national or international) are mostly supported only when roaming or between two different kinds of networks.

• Intracell same cell, other carrier or timeslot

• Intercell between cells (normal case)

• Inter-BSC between BSC areas

• inter-MSC between MSC areas

• inter- PLMN (only when roaming)

intracellintercell

inter-BSC

Figure 9. Handover Types

14.4.2 Handover Criteria

The adjacent cell parameters must be specified for any handover to be possible. Criteria for a handover are:

Interference, UL and DL

Bad and Good C/I ratio

Uplink quality and downlink quality

Uplink level and downlink level

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Distance

Rapid field drop and MS speed

Better cell, i.e. periodic check (power budget, umbrella handovers)

POC-PC: lower or upper quality/level thresholds (DL/UL)

14.5 Adjacencies

A mobile cannot hand over to a cell that has not been defined as an adjacent cell to the serving cell. In the beginning, it is a good idea to define all possible adjacencies and later the unnecessary ones can be removed. Note that handover control parameters affect all handovers from the cell, whereas adjacent cell parameters only affect one connection.

Most adjacencies must be defined in both directions.

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15 The BSS Parameter Planning Course

The material presented in the modules of this BSSPAR course contains explanations and examples of Base Station Subsystem (BSS) Parameters, including parameters related to Radio Network Planning. The material refers to parameters that are currently available in a Nokia BSS. There are GSM Phase 2 parameters implemented and identified.

All the parameters, which can be found in BSC and NMS, are written in bold format, for example cellReselectHysteresis (HYS)(BTS)(0 .. 14 dB)(4dB).

After the long name of each parameter (e.g. cellReselectHysteresis), there is a short name (e.g. HYS), the object level (e.g. BTS), the range of values (e.g. 0..14dB), and the MML default value (e.g. 4dB).

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16 Key Learning Points

The managed objects in a radio network are structured as a logical hierarchy. This makes handling sites and elements easier and more manageable than with a flat structure. The Managed Objects include the following objects: Base Station Controller (BSC), Base Control Function (BCF), Base Station (BTS)(which has the same meaning as cell and sector, in GSM), Transceiver (TRX), Radio Timeslot (RTSL), Handover Control Parameters per cell (HOC), Power Control Parameters per cell (POC), Adjacent Cell definitions (ADJC), Frequency Hopping per cell (FHS), BCCH Allocation Frequency List (BA), and Mobile Allocation Frequency List (MA).

There are two parameter dictionaries used in BSSPAR:BSS Radio Network Parameter Dictionary, andBSS and NSS RNW Parameter Dictionary.The aim of a parameter dictionary is to assist radio network planning and optimisation engineers and other BSC users, to find certain BSS parameters, their meanings, properties, and relation to the GSM specifications.

The parameter dictionary gives the following properties for each parameter:• GSM reference: the name of standard in which the parameter is defined• Q3 name: the name of the parameters that is used on the GUI• Modification: states how the parameters can be modified, e.g. Online, Offline.• Range: the range of values that the parameter can take• MML default value: the default value of the parameter• Description of what the parameter is used for in the BSS• Related command(s) that perform a function relevant to this parameter

For most parameters, the default value is also the recommended value. The recommended parameter values are dependent on the network configuration, local conditions, and the operator. They may change from time to time.

The Background Database feature enables the activation of several modified radio network parameters, with one command.

For every BSS software release, the parameter dictionary is updated and objects, parameters, MML commands may be added, removed or modified. New parameters are listed in the Section 'Summary of changes' at the beginning of the BSS Radio Network Dictionary. The new parameters are listed according to the Radio Objects such as BSC, BTS, Adjacent Cell, etc.

Idle mode signalling is directly relevant to LA design, and dedicated mode signalling is relevant to measurement reporting, HOC, and POC.

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17 Review Questions

Q1. Draw a diagram in the space below to illustrate the hierarchy of managed objects in a radio network. The diagram should contain BSC, BCF, BTS, TRX, RTSL, HOC, POC, ADJC, FHS, BA, and MA.

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Q2. For the parameters identified below, complete the table:

Parameter Name MS distance averaging window size

BSS RNW Par. Dictionary Page

Q3 name

MML short name

Object level

Range

Default value

Related command(s)

Parameter Name Directed Retry threshold

BSS RNW Par. Dictionary Page

Q3 name

MML short name

Object level

Range

Default value

Related command(s)

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Q3. Which of the following are parameters in the Background Database?

a) Background Network Colour Code

b) Background BTS Colour Code

c) Background BTS Hopping Mode

d) Background Underlay BTS Hopping Mode

e) Background Hopping Sequence Number 1

f) All of the above.

Q4. How many new BSC parameters were introduced between Versions 16V and 17 of the BSS RNW Parameter Dictionary?

a) 81

b) 21

c) 176

d) 43

e) 16

Q5. Which of the following is true about signalling in Idle and Dedicated modes?

a) Idle mode signalling is directly relevant to LA design, and dedicated mode signalling is relevant to measurement reporting, HOC, and POC.

b) Dedicated mode signalling is directly relevant to LA design and idle mode signalling is relevant to measurement reporting, HOC, and POC.

c) Both (a) and (b).

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bss - introduction to parameter planning

Documents

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rtsl level parameters116adjc