DFCA

GSM/EDGE BSS, Rel. RG20(BSS), Operating Documentation, Issue 10

BSS11052: Dynamic Frequency and Channel Allocation

DN03282742

Issue 6-2Approval Date 2011-10-14

Confidential

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BSS11052: Dynamic Frequency and Channel Alloca-tion

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Table of contentsThis document has 78 pages.

Summary of changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1 Overview of Dynamic Frequency and Channel Allocation . . . . . . . . . . . . 8

2 System impact of Dynamic Frequency and Channel Allocation . . . . . . 112.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.2 Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122.3 Impact on transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.4 Impact on BSS performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.5 User interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.5.1 BSC MMI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.5.2 BTS MMI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.5.3 BSC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.5.4 Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192.5.5 Measurements and counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192.6 Impact on Network Switching Subsystem (NSS) . . . . . . . . . . . . . . . . . . 232.7 Impact on NetAct products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.8 Impact on interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.9 Impact on capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252.10 Interworking with other features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252.11 Impact on mobile stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3 DFCA hopping DFCA mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4 DFCA channel allocation algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304.1 Properties of cyclic frequency hopping . . . . . . . . . . . . . . . . . . . . . . . . . 304.2 Interference control principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324.3 DFCA C/I estimation process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5 Channel ranking and selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425.1 DFCA channel allocation methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425.2 Soft blocking C/I. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435.3 Channel type preference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445.4 Rotation in channel allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455.5 Training sequence code selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455.6 Forced HR mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

6 BIM update process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486.1 C/I statistics collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486.2 Processing of the C/I statistics for BIM update . . . . . . . . . . . . . . . . . . . 486.3 Creating a new BIM entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496.4 Updating an existing BIM entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506.5 Removing a BIM entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516.6 Segment environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516.7 BCCH frequency list. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526.8 DFCA cell identification process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 536.9 BCCH and BSIC conflict management . . . . . . . . . . . . . . . . . . . . . . . . . 53

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7 BSC-BSC interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

8 Automatic configuration changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598.1 Loss of synchronisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598.2 Loss of inter-BSC connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

9 Dynamic Frequency and Channel Allocation management . . . . . . . . . . 619.1 Defining DFCA MA lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619.2 Attaching DFCA MA lists to a BTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639.3 Defining DFCA TRXs of a BTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649.4 Modifying the DFCA mode of a BTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . 649.5 Changing DFCA frequencies during DFCA use . . . . . . . . . . . . . . . . . . . 669.6 Rehoming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 669.7 Optimising intra-cell handover parameters . . . . . . . . . . . . . . . . . . . . . . . 66

10 Frame number and timeslot offsets . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6810.1 Frame number offset for optimised BSIC decoding performance. . . . . . 6810.2 Timeslot offset for better FR SACCH performance. . . . . . . . . . . . . . . . . 6910.3 Flexible Frame number offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

11 Planning Dynamic Frequency and Channel Allocation . . . . . . . . . . . . . . 72

12 Implementing Dynamic Frequency and Channel Allocation overview . . 78

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List of figuresFigure 1 DFCA system architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Figure 2 Example of a resource division in a DFCA BTS . . . . . . . . . . . . . . . . . . 13Figure 3 Protocol stack of the BSC-BSC interface. . . . . . . . . . . . . . . . . . . . . . . . 25Figure 4 Example of BTS configuration in DFCA hopping mode . . . . . . . . . . . . . 29Figure 5 DFCA channel selection process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Figure 6 Principle of cyclic frequency hopping. . . . . . . . . . . . . . . . . . . . . . . . . . . 31Figure 7 Interference relations with FN offsets . . . . . . . . . . . . . . . . . . . . . . . . . . 32Figure 8 Information used by DFCA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Figure 9 DFCA C/I estimations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Figure 10 Good cell average C/I, forced HR mode 'off' . . . . . . . . . . . . . . . . . . . . . 47Figure 11 Bad cell average C/I, forced HR mode 'on' . . . . . . . . . . . . . . . . . . . . . . 47Figure 12 Channel assignment conflict . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55Figure 13 Usage of DFCA MA groups in separate service areas in the BSS . . . . 62Figure 14 FN offset planning rule. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68Figure 15 Example of frequency band split . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

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List of tablesTable 1 Required additional or alternative hardware or firmware . . . . . . . . . . . . 11Table 2 Required software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Table 3 Impact of DFCA on BSC units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Table 4 Counters of Traffic Measurement related to DFCA . . . . . . . . . . . . . . . . 19Table 5 Counters of Resource Availability Measurement related to DFCA . . . . 19Table 6 Counters of BSC Level Clear Code (PM) Measurement related to DFCA .

20Table 7 Counters of DFCA Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Table 8 Counters of DFCA Assignment Measurement . . . . . . . . . . . . . . . . . . . . 21Table 9 Counters of BSC-BSC Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . 22Table 10 Counters of DFCA SAIC Measurement . . . . . . . . . . . . . . . . . . . . . . . . . 22Table 11 Example of the BIM scaling factor calculation . . . . . . . . . . . . . . . . . . . . 38Table 12 DFCA user classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Table 13 Example of LAC-to-SPC mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Table 14 Required software for the feature Flexible Frame number offset . . . . . . 70

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Summary of changes


Summary of changesChanges between document issues are cumulative. Therefore, the latest document issue contains all changes made to previous issues.

Changes made between issues 6-2 and 6-1Chapter, System impact of Dynamic Frequency and Channel Allocation has been modified with Flexi Multiradio, Flexi Multiradio 10, and Flexi Compact version informa-tion.

Impact of feature BSS21507: Flexible MCPA TX Power Pooling has been added to the chapter, System impact of Dynamic Frequency and Channel Allocation.

Two LMU area parameters, LMU Frame number 26-multiplier usage and LMU FN TSL Delay have been added to the chapter, System impact of Dynamic Frequency and Channel Allocation. Effect of the LMU area parameters have been added to chapters, Frame number and timeslot offset system and Planning Dynamic Frequency and Channel Allocation.

Changes made between issues 6-1 and 6-0Architecture in the chapter Overview of Dynamic Frequency and Channel Allocation has been modified with the information related to mcBSC.

Chapter System impact of Dynamic Frequency and Channel Allocation has been modified with the following information related to mcBSC:

• Table 1 and 3 have been modified. • The value range of maximum DFCA MA list and DFCA MA list group ID has been

updated. • BSC parameter ‘identification of mobile allocation frequency list (-) (MAL ID)’ has

been added. • MML value range for the BTS - level parameter ‘DFCA unsynchronized mode MA

frequency list (DUMAL)’ has been added. • Description of BSC-BSC interface in the section Impact on interfaces has been mod-

ified.

The Chapter System impact of Dynamic Frequency and Channel Allocation has been updated with the impact of BSS21391:DFCA support for OSC feature.

• BSC parameters and BTS parameters have been updated. • Interworking with other features has been updated with ‘DFCA support for OSC’.

Changes made between issues 6-0 and 5-2The Chapter System impact of Dynamic Frequency and Channel Allocation has been updated with the impact of BSS21222:Energy Optimized TCH Allocation feature.

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Id:0900d805808cbf16Confidential

Overview of Dynamic Frequency and Channel Alloca-tion

1 Overview of Dynamic Frequency and Channel AllocationDynamic Frequency and Channel Allocation (DFCA) dynamically assigns the optimum radio channel for a new connection. DFCA uses interference estimations derived from the mobile station (MS) downlink (DL) measurement reports and combines them with the timeslot and frequency usage information.

The DFCA channel allocation algorithm selects the radio channel for a connection from a dedicated channel pool based on carrier/interference ratio (C/I) criteria. The idea in DFCA channel selection is to provide enough quality in terms of C/I, so that each con-nection meets its quality of service (QoS) requirements. The different degrees of inter-ference tolerance of different connection types are taken into account in the channel selection process. Examples of the connection types are connections using enhanced full rate speech codec (EFR) or full rate (FR) and half rate (HR) connections using adaptive multi-rate speech codec (AMR).

By dynamically allocating frequency hopping parameters (MA, MAIO) for each individ-ual timeslot, DFCA provides more effective frequency reuse than a static frequency plan. This leads to a significant capacity gain with ensured quality.

The basic DFCA feature is used for circuit-switched traffic only; it does not handle packet-switched traffic or SDCCH channels. The GRPRS/EDGE territory and SDCCH channels are placed on a regular transceiver (TRX) that has been assigned to a separate portion of the frequency band and controlled by the conventional channel allo-cation algorithm. The usage of SDCCH and PS Data Channels on DFCA TRXs is sup-ported with a separate feature. For more information see BSS21161: SDCCH and PS Data Channels on DFCA TRX.

ArchitectureThe main Dynamic Frequency and Channel Allocation (DFCA) functionality is located in the BSC. The DFCA channel allocation algorithm in the BSC controls the radio channel assignments of all DFCA TRXs in all BTSs controlled by the BSC.

The information related to the potential interference situation expected for a certain con-nection comes mainly from mobile stations' (MS) downlink (DL) measurement reports. However, because of the limited amount of information contained in the measurement reports provided by the Mobile Stations (MSs), a statistical estimation of the interference situation is implemented. This is done by means of a background interference matrix (BIM).

The BTSs using DFCA must be synchronised to a global clock reference provided by a location measurement unit (LMU) installed in every BTS site.

The DFCA channel allocation algorithm maintains the real-time knowledge of the radio channel usage situation of all BTSs in the area. This concerns both the BTSs controlled by the BSC itself and the BTSs controlled by other BSCs that have been detected to be interfering or interfered by the local BTSs. To be aware of the radio channel usage in the external BTSs, the DFCA algorithms in different BSCs exchange information between them. This information exchange is provided by the IP-based BSC-BSC connection between the BSCs running the DFCA algorithm. In the BSC-BSC interface, each pair of neighboring BSCs is connected to each other. The BSC-BSC interface is an SCCP over IP connection terminated at the LAN connectors of the BSC signalling units (BCSUs).

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Figure 1 DFCA system architecture

Benefits

• Enhanced qualityDFCA is able to handle different circuit-switched traffic classes (EFR, HR, AMR, 14.4 kbit/s data) individually, and it provides the means to differentiate between users. This is especially powerful when the full benefit of AMR connections is wanted without 100% AMR penetration. By guaranteeing a sufficient C/I level for each user, the network performance in terms of received signal quality (RXQUAL), frame error rate (FER) and dropped call rate can be significantly improved.

• Capacity boosterThe criteria for sufficient C/I for each connection also optimises the interference caused to other connections. This leads to significant capacity gain, as the use of the valuable frequency resources is dynamically optimised. By decreasing the effec-tive frequency reuse distance in the network, DFCA makes it possible to accommo-date more circuit-switched traffic by adding more TRXs to the existing BTSs without quality deterioration. Alternatively, more frequencies can be used on the regular layer and/or the BCCH layer. This increases the performance and capacity available for GPRS/EDGE.

Related topics in Dynamic Frequency and Channel Allocation

• System impact of Dynamic Frequency and Channel Allocation • DFCA hopping DFCA mode • DFCA channel allocation algorithm • Channel ranking and selection • BIM update process • BSC-BSC interface • Automatic configuration changes • Dynamic Frequency and Channel Allocation management • Frame number and timeslot offsets • Planning Dynamic Frequency and Channel Allocation • Implementing Dynamic Frequency and Channel Allocation overview

LMU

BSC 1

IP network

BSC 2

DFCA DFCA

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Other related topics

• Feature Descriptions • Radio Network Performance

• Common BCCH Control • BSS Synchronisation

• Macrocellular • Multi BCF Control

• Value Added Services • Single Antenna Interference Cancellation in BSC

• Integrate and Configure • Connecting and testing BSC-BSC Interface

• Activate • Radio Network Performance

• Activating and Testing BSS11073: Recovery for BSS and Site Synchronisa-tion and BSS20371: BSS Synchronisation Recovery Improvement

• Activating and Testing BSS11052: Dynamic Frequency and Channel Alloca-tion

• Reference • Commands

• MML commands • EB - Frequency List and GPRS Objects Handling • EE - Base Station Controller Parameter Handling in BSC • EF - Base Control Function Handling • EQ - Base Transceiver Station Handling in BSC • ER - Transceiver Handling • W7 - Licence and Feature Handling

• Service Terminal commands • BSC Radio Resource Monitoring

• Counters/Performance Indicators • Circuit-switched Measurements

• 100 DFCA Measurement • 101 DFCA Assignment Measurement • 102 BSC-BSC Measurement • 108 DFCA SAIC Measurement

• Parameters • BSS Radio Network Parameter Dictionary

• Troubleshoot • Alarms

• Failure Printouts (2000-3999) • Base Station Alarms (7000-7999)

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System impact of Dynamic Frequency and Channel Al-location

Id:0900d805808c135fConfidential

2 System impact of Dynamic Frequency and Channel AllocationThe system impact of BSS11052: Dynamic Frequency and Channel Allocation (DFCA) is specified in the sections below.

For more information on the BSS-level synchronisation required by DFCA, see BSS Synchronisation under Feature Descriptions.

DFCA is licence key controlled. Its use is controlled by a capacity licence based on the number of TRXs. For more information on licences, see Licence Management in BSC under Administer.

2.1 RequirementsHardware requirements

Software requirements

Network element Hardware/firmware required

BSC BSC3i or BSC2i or mcBSC is required.

BSC2i requires CP6MX CPU cards in all units, and CPLAN-S panel is also required.

The BSCs that use DFCA and have adjacent service areas must be connected to each other with BSC-BSC connec-tion. This may require LAN cabling, hubs/switches and other networking equipment.

BTS DFCA requires either UltraSite, Flexi EDGE, Flexi Multiradio or MetroSite base stations. The UltraSite base station requires wideband combining or no combiners. DFCA is not supported with RTC combiners.

LMU DFCA requires BSS synchronisation.

This requires that one location measurement unit (LMU) is installed in every BTS site where DFCA is used.

TCSM No requirements

mcTC No requirements

SGSN No requirements

Table 1 Required additional or alternative hardware or firmware

Network element Software release required

BSC S11.5 ED6.1

Flexi EDGE BTS EP2.0

Flexi Multiradio BTS EX4.1 MP1

UltraSite EDGE BTS CX4.1

MetroSiteEDGE BTS CXM4.1

Table 2 Required software

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Table Required software shows the earliest version that supports DFCA.

Other requirementsBSC to BSC interconnection

The DFCA algorithm needs real-time knowledge of the radio channel usage situation of all DFCA BTSs in the area. Near the BSC area borders, some significant interfering BTSs may be controlled by other BSCs. The DFCA algorithms in different BSCs must be able to exchange information between them. The IP-based BSC-BSC interface is used to exchange the information needed by the DFCA algorithms in separate BSCs so that the DFCA can operate as transparently as possible across BSC area borders.

BSS Synchronisation

DFCA requires radio timeslot (RTSL) level synchronisation between base stations to function. The basic RTSL level synchronisation is provided by BSS Synchronisation.

Recovery for BSS and Site Synchronisation or BSS Synchronisation Recovery Improve-ment completes the synchronisation support for DFCA. It follows the synchronisation status of the BTSs and provides information based on which the BSC can change its behaviour and ensure satisfactory operation of DFCA TRXs even when the synchroni-sation has been lost. For more information, see Activating and Testing BSS11073: Recovery for BSS and Site Synchronisation and BSS20371: BSS Synchronisation Recovery Improvement under Activate.

Frequency band supportThe BSC supports DFCA on the following frequency bands:

• GSM 800 • GSM 900 • GSM 1800 • GSM 1900

2.2 RestrictionsWithin a BTS, the use of DFCA is controlled on a per TRX basis. In a BTS using DFCA, there are both DFCA and regular TRXs. The DFCA TRXs do not support any signalling channels and therefore, the BCCH TRX of a BTS must be a regular TRX. With feature SDCCH and PS Data Channels on DFCA TRX, the SDCCH and GPRS/EDGE channels

Talk-family BTS Not supported

MSC/HLR No requirements


NetAct OSS4

LMU, LMU Manager 4.4

LMUB, LMU Manager 1.0 CD1

Flexi Multiradio 10 BTS GF 1.0

Flexi Compact BTS GFC 1.0


Table 2 Required software (Cont.)

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can be carried with DFCA TRX. Otherwise these channels must be placed on regular TRX. Depending on the requirements for the GPRS/EDGE territory size, this may require the operator to define another regular TRX, in addition to the BCCH TRX of a BTS for carrying GPRS/EDGE. Figure Example of a resource division in a DFCA BTS illustrates how the resources can be allocated in a DFCA BTS.

Figure 2 Example of a resource division in a DFCA BTS

The maximum number of DFCA cells in a BSC is 1500 that can be obtained with the capacity of TRXs. If the BSC already contains 1500 DFCA cells, an attempt to create another one fails, and an error message is generated in the MCMU log.

2.3 Impact on transmissionNo impact.

2.4 Impact on BSS performanceOMU signallingNo impact.

TRX signallingNo impact.

Impact on BSC units

Impact on BTS unitsNo impact.

TRX BCCH SDCCH GPRS/EDGE territory

GPRS/EDGE territoryTCH

TCH

TCH

TRX

TRX

TRX

BCCH TRX,fixed frequency

Additional regular TRX,fixed frequency or RF FH

DFCA hopping

DFCA hopping

BSC unit Impact

OMU BSC2i requires a CP6MX (500 MHz) CPU plug-in unit.

MCMU BSC2i requires a CP6MX (500 MHz) CPU plug-in unit.

BCSU BSC2i requires a CP6MX (500 MHz) CPU plug-in unit.

The BSC-BSC interface terminates in the BCSUs.

BCXU The BSC-BSC interface terminates in the BCXUs in mcBSC.

PCU No impact

Table 3 Impact of DFCA on BSC units

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2.5 User interface

2.5.1 BSC MMIThe following command groups and MML commands are used to handle DFCA:

• Base Station Controller Parameter Handling in BSC: EEC, EEF, EED, EES, EEH, EEO • Frequency List and GPRS Objects Handling: EBE, EBT • Base Transceiver Station Handling in BSC: EQO, EQM, EQI, EQA • Transceiver Handling: ERC, ERM, ERO • Base Control Function Handling: EFL • Position Based Services Handling: EXB, EXI • Licence and Feature Handling: W7I, W7M

For more information on the command groups and MML commands, see MML commands under Reference..

2.5.2 BTS MMIDFCA cannot be managed with BTS MMI.

2.5.3 BSC parametersThe following lists the optional radio network parameters related to DFCA that are avail-able when DFCA is used in the network. For more information on the parameters, see BSS Radio Network Parameter Dictionary under Reference.

BSC-level parametersThe BSC-level parameters are organised into the following groups:

Connection type specific C/I targets

These parameters specify the target carrier-to-interference ratio (C/I) for different con-nection types that are used in the DFCA C/I estimation and channel selection process.

The parameters are handled with the EEH and EEO commands.

• C/I target FR (CIF) • C/I target HR (CIH)

The availability of the parameter requires the Half Rate software. • C/I target AMR FR (CIAF)

The availability of the parameter requires the AMR FR software. • C/I target AMR HR (CIAH)

The availability of the parameter requires the AMR Half Rate software. • C/I target 14.4 (CIT)

The availability of the parameter requires the 14.4 kbit/s data software. • C/I target OSC DHR (CIDHR)

The availability of the parameter requires the OSC Double Half Rate software. • C/I target OSC DFR (CIDFR)

The availability of the parameter requires the OSC Double Full Rate software.

For more information, see DFCA C/I estimation process.

C/I offsets


DN03282742 15




• C/I target UL offset (CIUL)This parameter defines an offset that is added to the C/I targets and soft blocking C/I limits of all connection types when uplink interference checks are performed. It is used to compensate for any differences between UL and DL link level performance.

• SAIC DL C/I offset (SCIO)The availability of the parameter requires the Single Antenna Interference Cancella-tion software.For more information, see Single Antenna Interference Cancellation in BSC under Feature Descriptions.

Connection type specific soft blocking C/I limits

These parameters specify the soft blocking C/I limits for different connection types. The soft blocking C/I limits are used in the channel selection process.


• soft blocking C/I FR (SBF) • soft blocking C/I HR (SBH)

The availability of the parameter requires the Half Rate software. • soft blocking C/I AMR FR (SBAF)

The availability of the parameter requires AMR FR software. • soft blocking C/I AMR HR (SBAH)

The availability of the parameter requires the AMR Half Rate software. • soft blocking C/I 14.4 (SBCI)

The availability of the parameter requires the 14.4 kbit/s data software. • soft blocking C/I OSC DHR (SBDHR)

The availability of the parameter requires the OSC Double Half Rate software. • soft blocking C/I OSC DFR (SBDFR)

The availability of the parameter requires the OSC Double Full Rate software.

For more information, see Soft Blocking C/I.

BIM update parameters

These parameters govern the background interference matrix (BIM) update process.


• BIM confidence probability (BCP) • BIM interference threshold (BIT)

• BIM update period (BUP)

• BIM update scaling factor (BUSF) • BIM update guard time (BUGT)

There are also two UTPFIL parameters related to the BIM update process:

• RCS_DFCA_SAMPLE_VALUE_PRM_C • RCS_DFCA_SCALING_FACTOR_PRM_C

For more information, see BIM update process and Processing of the C/I statistics for BIM update.

DFCA channel allocation method

The parameter defines whether DFCA assignments are made primarily to channels that have a connection-specific C/I target level or to channels that have the highest positive C/I difference from the target level.

The parameter is handled with the EEH and EEO commands.

16 DN03282742




• DFCA channel allocation method (DCAM)

For more information, see Channel ranking and selection.

LAC-to-SPC mapping table parameters

These parameters are used to define the location area code (LAC) to signalling point code (SPC) mapping table that is used to identify the BSCs in the BSC-BSC interface.

• mapping entry index (MEI) (read-only parameter)This parameter is handled with the EEC, EEF, EED, and EES commands.

• location area code (LAC)This parameter is handled with the EEC and EEF commands.

• signaling point code (SPC)This parameter is handled with the EEC and EEF commands.

For more information, see BSC-BSC interface.

Mobile allocation frequency list level parameters

• DFCA MA list ID(MALD ID)This parameter is handled with the EBE and EBT commands. With this parameter you can identify the DFCA MA frequency list that is created.

• DFCA MA list state(MALS)With MA list id values 1 - 4200 the MA list state value cannot be changed. With DFCA MA list id values 1 - 64 only DFCA MA list state values 'in use' and 'out of use' are allowed.The parameter is a MA list parameter and it is handled with the EBE and EBT com-mands. In the DFCA case, the parameter also indicates if the list is ready for use or if it has only been created but not yet employed by the DFCA algorithm. Changing the activity state of a DFCA MA list from 'in use' to 'out of use' requires that the DFCA MA list is not connected to any BTS.

• DFCA MA list group ID (DMAG)The value range of the DFCA MA list group ID parameter is 1 to 64 and its default value is 0. This parameter can be modified only when the DFCA MA list is in 'out of use' state.The parameter indicates to which group the DFCA MA list belongs. All the DFCA MA lists that are used in the same geographical service area will be defined to the same DFCA MA list group. If the geographical service areas are apart from each other, then the DFCA MA lists of these areas can be defined to different DFCA MA list groups. The frequencies can be reused freely in DFCA MA lists, which are defined into different groups. The DFCA does not control interference between co-channels and adjacent channels that use the DFCA MA lists, which belong to different DFCA MA list groups. It is the operator's responsibility to take care of that in the radio network planning and the configuring phase.

• DFCA MA List Usage (DMAU)The possible values for the DFCA MA list usage parameter are CS (1), PS (2), and CSPS (3). The default value of the parameter is CSPS (3). This parameter can be modified only when the MALD is in 'out of use' state.The parameter defines the usage of DFCA MA list.

DN03282742 17




• identification of mobile allocation frequency list (-) (MAL ID)The MML value range of an MA frequency list is from 1 to 4200.NetAct Note: With this parameter you can identify the mobile allocation frequency list or the DFCA unsynchronized MA frequency list you are creating.

Expected BSC-BSC interface delay

With this parameter you define the expected BSC-BSC interface delay. This parameter is used for the channel assignment control to prevent simultaneous channel allocations in neighbour BSCs.

• expected BSC-BSC interface delay (EBID)This parameter is handled with the EEH and EEO commands.

BTS-level parameters

• DFCA mode (DMOD)This parameter is handled with the EQO, EQM, and EFL commands. The modification of this parameter requires BTS locking if the DFCA mode of the BTS is changed from 'standby' to DFCA hopping' or from 'DFCA hopping' to 'standby' or 'off'.

• DFCA mobile allocation frequency lists (DMAL)This parameter is handled with the EQO and EQA commands. The modification of this parameter requires BTS locking or locking of all the DFCA TRXs of the BTS if the DFCA mode of the BTS is 'DFCA hopping'.

• DFCA unsynchronized mode MA frequency list (DUMAL)This parameter is handled with the EQO and EQA commands. The modification of this parameter requires BTS locking if the DFCA mode of the BTS is 'DFCA hopping'.The MML value ranges from 0 to 4400. Value 0 detaches the BTS.

• forced HR mode C/I threshold (FHT)

• forced AMR HR mode C/I threshold (FAHT)

• forced HR mode C/I averaging period (FHR)

• forced HR mode hysteresis (FHH)These four parameters are handled with the EQO and EQM commands.Note that if there are several BTS objects in a band in the cell, the value of the parameter has to be the same for all the BTSs in the band.

BCCH TRX allocation preference

• Upper DL RX level threshold for BCCH TRX preference for TCH (UDRB) • Lower DL RX level threshold for BCCH TRX preference for TCH (LDRB).

These parameters define the DL RX level window for BCCH TRX preference. If measured DL RX level is within this window BSC allocates the call to a BCCH TRX, else to a non-BCCH TRX.

TRX-level parameter

• DFCA indication (DFCA)This parameter is handled with the ERC, ERM, and ERO commands.The modification of this parameter requires TRX locking if the DFCA mode of the BTS is 'DFCA hopping'. For more information, see Defining DFCA TRXs of a BTS.

18 DN03282742




LMU area level parameters

• frame number offset (FNO) (range: 0–51)This parameter is handled with the EXB command.The modification of this parameter requires disabling the synchronisation of the BCF chain if the location measurement unit (LMU) in the LMU area is used for BSS syn-chronisation. For more information, see Frame number offset for optimised BSIC decoding performance.

• lmu tsl fn offset (LTO) (range: 0–1)This parameter is handled with the EXB command.The modification of this parameter requires disabling the synchronisation of the BCF chain if the LMU in the LMU area is used for BSS synchronisation. For more infor-mation, see Timeslot offset for better FR SACCH performance.

• FNO 26-multiplier Usage (values: in use, not in use)This parameter controls enabling and disabling of 26 multiplier for frame number offset. When ‘FNO 26-multiplier Usage’ parameter is ‘not in use’, the synchronisa-tion does not follow the 26 period and the interference cannot be separated with the half TSL accuracy.

• lmu fn tsl delay (range: 0–10)The parameter defines, how many symbol periods (a symbol period: ~3.69 micro-seconds) time slot offset for the FN phasing is delayed.

UTPFIL parameters related to intra-cell handovers

• RCS_UNPACK_LEV_THR_PRM_C

• RCS_INTF_LEV_DFCA_PRM_C • RCS_INTF_LEV_DFCA_THR_PRM_C

• RCS_QUAL_LIMIT_DFCA_PRM_C

For more information on the parameters, see Optimising intra-cell handover parameters.

UTPFIL parameters related to power reduction

• DFCA_MAX_PWR_RED_UL

• DFCA_MAX_PWR_RED_DLThese parameters define the maximum power reduction in dB for UL and DL direc-tions, because the power reduction is limited for these directions.

• SFT_MAR_PC_N_BCCHThis parameter is for the power reduction margin in non-BCCH band in dB. It is used to set separate margins for the BCCH and non-BCCH band.

UTPFIL parameter for DFCA LAR usage

• DFCA_LAR_USAGEThis parameter defines if LAR/LER parameters are taken into account when deciding if a BTS is suitable or not for TCH allocation. If this parameter is patched on, C/N blocking is disabled.

UTPFIL parameters for BCCH rotation

• SYI_CELL_UPDThis parameter is used to turn off the BCCH rotation method when RRM tries to change a list every 10 minutes although all the BCCH frequencies are included in the list.

DN03282742 19




UTPFIL parameter for BIM threshold extension in C/I calculation

• BIM_THRESH_EXTThis parameter is used to adjust the accuracy of C/I calculations with a good C/I. This dB value is added into the BSC parameter BIM interference threshold (BIT) when deciding if interfering cell is included in C/I calculations or not. A larger value means more accurate calculations, as the cells with lower interference are also included in calculations.

UTPFIL parameter for TCH allocation preference

• tch_alloc_prefThis parameter defines the preference between DFCA and regular layer, when DFCA is used. With this parameter the preference can be changed to be a DFCA layer (default), regular layer or the preferred layer, which is defined based on the mobile specific measurement results mobile by mobile.

2.5.4 AlarmsThe following alarms can be generated in connection with DFCA:

• 3260 UNKNOWN POTENTIALLY INTERFERING CELL FOR DFCA • 3286 INTER BSC CONNECTION FAILURE DISTURBING DFCA OPERATION • 7764 DFCA USE PREVENTED DUE ANOTHER BSC UNCONTROLLED INTER-

FERENCE • 7765 DFCA NEIGHBOUR CELL CONFLICT • 7768 INCONSISTENT DATA IN DFCA RADIO RESOURCE STATE FILES

For a detailed description of the alarms, see Failure Printouts (2000 - 3999) and Base station alarms 7000-7999 under Reference.

2.5.5 Measurements and countersThe following measurements and counters are related to DFCA.

1 Traffic Measurement

For more information, see 1 Traffic Measurement under Reference.

2 Resource Availability Measurement

Name Number

TCH REL BSC BSC CONFLICT CALL 001217

TCH REL BSC BSC CONFLICT TARG 001218

Table 4 Counters of Traffic Measurement related to DFCA

Name Number

TIME FORCED HR MODE 002081

TIME FORCED AMR HR MODE 002082

Table 5 Counters of Resource Availability Measurement related to DFCA

20 DN03282742




For more information, see 2 Resource Availability Measurement under Reference.

51 BSC Level Clear Code (PM) Measurement

For more information, see 51 BSC Level Clear Code (PM) Measurement under Refer-ence.

100 DFCA Measurement

TIME FORCED HR AND AMRHR MODE 002083

Name Number

INTER BSC DFCA ASSIGN SUCC 051157

INTER BSC DFCA ASSIGN REJ 051158

Table 6 Counters of BSC Level Clear Code (PM) Measurement related to DFCA

Name Number

C/I TARGET 100000

C/I TARGET UL OFFSET 100001

DFCA C/I TARGET UL 100002

DFCA C/I TARGET DL 100003

DFCA C/I TARGET+1 UL 100004

DFCA C/I TARGET+1 DL 100005

DFCA C/I TG+2 UL 100006

... ...

DFCA C/I TARGET+20 UL 100042

DFCA C/I TARGET+20 DL 100043

DFCA C/I > TARGET+20 UL 100044

DFCA C/I > TARGET+20 DL 100045

DFCA C/I TARGET-1 UL 100046

DFCA C/I TARGET-1 DL 100047

... ...

DFCA C/I TARGET-15 UL 100074

DFCA C/I TARGET-15 DL 100075

DFCA C/I < TARGET-15 UL 100076

DFCA C/I < TARGET-15 DL 100077

MOST INTERFERED C/I TARGET UL 100078

MOST INTERFERED C/I TARGET DL 100079

Table 7 Counters of DFCA Measurement

Name Number

Table 5 Counters of Resource Availability Measurement related to DFCA (Cont.)

DN03282742 21




For more information, see 100 DFCA Measurement under Reference.

101 DFCA Assignment Measurement

For more information, see 101 DFCA Assignment Measurement under Reference.

MOST INTERFERED C/I TARGET+1 UL 100080

MOST INTERFERED C/I TARGET+1 DL 100081

... ...

MOST INTERFERED C/I TARGET+20 UL 100118

MOST INTERFERED C/I TARGET+20 DL 100119

MOST INTERFERED C/I > TARGET+20 UL 100120

MOST INTERFERED C/I > TARGET+20 DL 100121

MOST INTERFERED C/I TARGET-1 UL 100122

MOST INTERFERED C/I TARGET-1 DL 100123

... ...

MOST INTERFERED C/I TARGET-15 UL 100150

MOST INTERFERED C/I TARGET-15 DL 100151

MOST INTERFERED < C/I TARGET-15 UL 100152

MOST INTERFERED < C/I TARGET-15 DL 100153

SUCC DFCA ASS 100154

SUCC DFCA ASS HIGH LOAD 100155

SOFT BLOCKED DFCA ASS DUE TO C/I 100156

SOFT BLOCKED DFCA ASS DUE TO C/N 100157

PRIMARY DFCA ALGORITHM ATT 100158

SECONDARY DFCA ALGORITHM ATT 100159

Name Number

MA MAIO 1 101000

DFCA ASS 1 101001

MA MAIO 2 101002

DFCA ASS 2 101003

... ...

MA MAIO 150 101298

DFCA ASS 150 101299

Table 8 Counters of DFCA Assignment Measurement

Name Number

Table 7 Counters of DFCA Measurement (Cont.)

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102 BSC-BSC Measurement

For more information, see 102 BSC-BSC Measurement under Reference.

108 DFCA SAIC MeasurementBefore DFCA SAIC Measurement can be activated, the Single Antenna Interference Cancellation (SAIC) licence must be installed and activated.

For more information, see 108 DFCA SAIC Measurement under Reference.

Name Number

BSC-BSC DELAY 102000

BSC - BSC DENOMINATOR 1 102001

BSC-BSC PEAK DELAY 102002

Table 9 Counters of BSC-BSC Measurement

Name Number

SAIC C/I TARGET 108000

DFCA SAIC DL C/I TARGET 108001

DFCA SAIC DL C/I TARGET + 1 DB 108002

... ...

DFCA SAIC DL C/I TARGET + 20 DB 108021

DFCA SAIC DL C/I > TARGET + 20 DB 108022

DFCA SAIC DL C/I TARGET - 1 DB 108023

... ...

DFCA SAIC DL C/I TARGET - 15 DB 108037

DFCA SAIC DL C/I TARGET < 15 DB 108038

MOST INTERFERED DFCA SAIC DL C/I TARGET 108039

MOST INTERFERED DFCA SAIC DL C/I TARGET + 1 DB

108040

... ...

MOST INTERFERED DFCA SAIC DL C/I TARGET + 20 DB

108059

MOST INTERFERED DFCA SAIC DL C/I > TARGET + 20 DB

108060

MOST INTERFERED DFCA SAIC DL C/I TARGET - 1 DB

108061

... ...

MOST INTERFERED DFCA SAIC DL C/I TARGET - 15 DB

108075

MOST INTERFERED DFCA SAIC DL C/I TARGET < 15 DB

108076

Table 10 Counters of DFCA SAIC Measurement

DN03282742 23




2.6 Impact on Network Switching Subsystem (NSS)No impact.

2.7 Impact on NetAct productsNetAct ConfiguratorNetAct Configurator can be used to configure the radio network parameters related to DFCA. For more information, see BSS RNW Parameters and Implementing Parameter Plans in NetAct Product Documentation. For a list of the radio network parameters, see BSC parameters.

NetAct ReporterFor a list of the measurement types related to DFCA, see Measurements and counters.

NetAct MonitorNetAct Monitor can be used to monitor all alarms related to DFCA. For a list of the alarms, see Alarms.

NetAct PlannerNo impact.

NetAct OptimizerNo impact.

NetAct TracingNo impact.

2.8 Impact on interfacesImpact on radio interfaceNo impact.

Impact on Abis interfaceAbis O&M

Dynamic Frequency and Channel Allocation (DFCA) introduces a new DFCA FU radio definition information element (IE) to communicate to the BTS that a transceiver (TRX) is to operate in the 'DFCA hopping' mode. This IE is included in the BTS_CONF_DATA message, where it replaces the FU radio definition IE in case of a DFCA TRX in a DFCA hopping BTS that is working synchronised with the surrounding network and with the related BSC-BSC interfaces up and running.

The content of the DFCA FU radio definition IE is the same as the content of the FU radio definition IE, except that the Radio definition for 8 TS IE is not included. The Radio def-inition for 8 TS IE normally contains the mobile allocation (MA) list, mobile allocation index offset (MAIO), and hopping sequence number (HSN) parameters for each timeslot of a TRX.

DFCA introduces one negative acknowledgement reason in the Abis O&M interface. It is related to the conflict between DFCA and Intelligent Downlink Diversity (IDD). The BSC is not aware of the possible use of IDD on the BTS side. The BTS rejects any

24 DN03282742




BTS_CONF_DATA message that tries to configure a TRX as a DFCA TRX in an radio frequency hopping (RF hopping) BTS object if the BTS is part of an RF hopping IDD main-auxiliary TRX pair. In such a case, reason SIMULTANEOUS USE OF DFCA AND IDD NOT SUPPORTED is given.

Abis telecom

With DFCA, the Abis telecom gives hopping configuration data also to the BTS. The optional Channel Identification IE has been taken into use in the Abis telecom interface. This is because of the dynamic nature of DFCA channel allocation, where the hopping configuration data is selected separately for each connection.

The DFCA algorithm assigns the MA list, the MAIO, and the training sequence code (TSC) dynamically for each connection that is to be placed on a DFCA hopping TRX. The MA list, MAIO, and TSC are transferred from the BSC to the BTS within the CHANNEL ACTIVATION message. The dynamically assigned hopping parameters are included in the Mobile Allocation and Channel Description IEs that are placed in the Channel Identification IE.

The Mobile Allocation IE provides the MA list that has been determined for the connec-tion on a DFCA hopping TRX. The MA list refers to the frequencies on the cell allocation list that has been transmitted to the DFCA TRXs in the BTS_CONF_DATA message.

The Channel Description IE communicates the MAIO and TSC settings that are deter-mined separately for each connection on a DFCA hopping DFCA TRX.

The Channel Identification IE is an optional element that is added in the CHANNEL ACTIVATION message when a channel activation is performed on a DFCA TRX of a DFCA hopping BTS that is operating synchronised (both the synchronisation status and BSC-BSC interface status of the BTS are OK).

Impact on A interfaceNo impact.

Impact on Gb interfaceNo impact.

BSC-BSC interfaceDFCA introduces a BSC-BSC interface for the transmission of channel allocation related data between DFCA algorithms in different BSCs when there are DFCA cells that inter-fere with each other across the BSC area borders.

The BSC-BSC interface is physically located in any or all of the BSC signalling units (BCSUs) of the BSC. The used protocol stack of the interface is presented in figure Protocol stack of the BSC-BSC interface.

DN03282742 25




Figure 3 Protocol stack of the BSC-BSC interface

The use of MTP3 user adaptation layer (M3UA) and signalling connection control part (SCCP) allows load sharing between BCSUs. It also supports BCSU switchovers. If links have been configured in two BSCUs, the system handles the switchovers without the application noticing it. The DFCA procedures are an extension of the radio network subsystem application part (RNSAP). The complete RNSAP has not been implemented as a part of DFCA.

For more information on configuring the BSC-BSC interface, see Connecting and Testing the BSC-BSC under Integrate and Congfiure.

2.9 Impact on capacityDFCA optimises the use of radio resources which leads to significant capacity gain. By decreasing the effective frequency reuse distance in the network, it is possible to accom-modate more circuit switched traffic by adding more TRXs to the existing BTSs without quality deterioration. Alternatively, more frequencies can be used on the regular layer and/or the BCCH layer, increasing the capacity available for GPRS/EDGE.

2.10 Interworking with other featuresFunctionality required by DFCABSS Synchronisation provides timeslot-level synchronisation between base stations, which is required by DFCA. DFCA needs to have information regarding the TSL, MA list, and MAIO usage in the neighbouring cells to estimate interference. This can only be done if all the BTSs are synchronised to the same clock (GPS).

Software products that are not supportedThe term DFCA BTS refers to a BTS object in which the value of the DFCA mode (DMOD) parameter is 'DFCA hopping'. The term DFCA TRX refers to a TRX that has been indicated as a DFCA TRX with the DFCA indication (DFCA) parameter in a DFCA BTS.

The following software products are not supported in a DFCA BTS:

• Intelligent Underlay-Overlay (IUO) and Intelligent Frequency Hopping (IFH) • Intelligent Coverage Enhancement (ICE) • Extended Cell Range • Antenna Hopping • Baseband hopping

RNSAP+

SCCP

M3UA

SCTP

IP

ethernet

RNSAP+

SCCP

M3UA

SCTP

IP

ethernet

BSC BSC

26 DN03282742




• RF hoppingNote that RF hopping cannot be used together with DFCA hopping when feature SDCCH and PS Channels on DFCA TRX is active and GPRS is used on DFCA TRX.

• BCCH Super Reuse • Double Power TRX for Flexi EDGE BTS (DFCA cannot be used in the same

segment with DPTRXs or IDD TRXs in the BTS)

The following software products are not supported in a DFCA TRX:

• GPRS/EDGENote that GPRS/EDGE is supported on DFCA TRX, when SDCCH and PS data channels feature is in use. For more information, see BSS21161: SDCCH and PS Data Channels on DFCA TRX.

• SDCCH, Dynamic SDCCHNote that SDCCH, Dynamic SDCCH is supported on DFCA TRX, when SDCCH and PS data channels feature is in use. For more information, see BSS21161: SDCCH and PS Data Channels on DFCA TRX.

• Pre-emptionNote that Pre-emption is supported only with SDCCH and PS data channels on DFCA TRX. For more information, see BSS21161: SDCCH and PS Data Channels on DFCA TRX.

• FACCH Call Setup • High Speed Circuit-Switched Data • Intelligent Downlink Diversity (IDD)

The DFCA algorithm does not cater for the 3 dB increase that is gained in the BCCH signal levels of the neighbour DFCA cells when IDD is used in the BCCH TRXs of these cells.

• 4-way uplink diversity • RF hopping

Software products with special considerations for DFCA

• Adaptive Multi-RateThe initial AMR channel rate (IAC) parameter allows you to specify the initial channel rate for adaptive multi-rate (AMR). When forced HR mode is triggered for DFCA, it overrides the initial AMR channel rate parameter. This means that forced HR is used for AMR MSs despite of the value of the initial AMR channel rate parameter.

• Advanced Multilayer Handling (AMH) and Direct Access to Desired Layer/Band (DADL/B) Regular and DFCA channels are seen as one resource group for the load calcula-tions used in AMH and in DADL/B.

• Automated Planning Enhancements (APE)If both DFCA and APE are used in a BTS, the BSC uses the BA list definitions made for APE. To ensure the proper functioning of DFCA, you must include all BCCH fre-quencies that are important for DFCA in the used measurement BA list.

• Common BCCH ControlDFCA cannot be used in a special case of Common BCCH Control, that is, in a BTS where both PGSM 900 and EGSM 900 TRXs are used, and where the BCCH is on the PGSM 900 band.

DN03282742 27




• Enhanced Measurement Report (EMR)With DFCA, it is recommended to specify a separate BCCH frequency list (BA list) containing all DFCA cell BCCH frequencies of the area in addition to the BCCH fre-quencies of the defined adjacent cells to be used for the active MSs in a DFCA BTS. This is to ensure that the MSs are able to report all interfering neighbour cells in the DFCA cell.For enhanced measurement reporting, the BCCH frequency information is not enough. In addition to the BCCH frequency, also BSIC information is needed. Because DFCA needs that MSs listen to all the interfering neighbour cells, it is not possible to define the needed BSICs. To tackle this, the BSC adds the needed BSICs automatically for enhanced measurement reporting to be listened to by the MSs. The BSC uses the BSIC codes found from the neighbour cells' BIM tables. The BSC changes the BSIC codes to be listened by the MSs periodically, so that the BSC can identify all the needed interfered and interfering cells and their BCCH and BSIC codes.Note that without EMR the maximum number of frequencies in a BA list is 32. When EMR is used, the maximum number of frequencies in the BA list depends on the neighbouring definitions. The sum of the defined adjacent cells plus the frequencies not used by any defined adjacent cell cannot exceed 32.

• Half RateRegular and DFCA channels are seen as one resource group for the load calcula-tions used in Half Rate.

• IMSI-based Handover to GSMIMSI-based Handover to GSM is not recommended for simultaneous use with DFCA, because it weakens the functionality of DFCA considerably. IMSI-based Handover to WCDMA can be used with DFCA without restrictions.

• Interference Band RecommendationNot supported for connections that are to be assigned to a DFCA TRX. The DFCA algorithm does not use UL idle channel measurements.

• Power controlThe DFCA algorithm may make initial power reduction based on C/I criteria for the connection on the DFCA TRXs. After the initial power reduction, the power control functions normally.

• Power Optimisation in HandoverNot supported for connections that are to be assigned to a DFCA TRX. The DFCA algorithm makes an initial power control based on C/I for a DFCA connection.

• Flexible MCPA TX Power PoolingDL TX power reduction in call setup is possible directly when DFCA is in use.

• QueuingIf the DFCA algorithm cannot find a proper DFCA channel due to soft blocking, only the non-DFCA resources can be queued for.Queuing is not applied to those DFCA BTSs that have experienced C/I or C/N blocking during the channel search. In this case, the call can only queue for the BTSs within the same cell or to the non-DFCA resources of all BTSs.

• Radio Network SupervisionAs the DFCA algorithm does not use the idle channel uplink interference information that is traditionally updated frequently for each TRX to the BSC channel allocation algorithm, this information is not delivered for the DFCA hopping TRXs to the channel allocation algorithm of the BSC. This is to avoid extra unnecessary process-ing load for the unit of the channel allocation algorithm. As a consequence, the BSC

28 DN03282742




cannot perform in DFCA TRXs the supervision of excessive traffic channel interfer-ence.

• Single Antenna Interference CancellationUsing DFCA with Single Antenna Interference Cancellation (SAIC) enhances the performance of SAIC. DFCA separates circuit-switched (CS) and packet-switched (PS) territories to different TRXs and uses different frequency bands for the PS TRXs. This means that 8-Phase Shift Keying (8-PSK) modulated interference caused by EGPRS connections does not affect SAIC CS connections and interfer-ence can be avoided by using DFCA. In addition, the DFCA channel allocation algo-rithm can be adjusted so that the BSC uses different downlink C/I targets for mobile stations that support SAIC.You can use the SAIC DL C/I offset parameter to lower the downlink C/I values used for SAIC calls in DFCA TCH allocation.

• WCDMA Neighbour Cell Reporting EnhancementThe FDD_REPORTING_THRESHOLD_2 parameter is delivered to dual-mode mobile stations in call-specific MEASUREMENT INFORMATION messages when WCDMA Neighbour Cell Reporting Enhancement is used with DFCA.

• BSS21222: Energy Optimized TCH AllocationThis feature is supported when DFCA feature is used with SDCCH and PS data channels on DFCA feature. Without SDCCH and PS Data Channels on DFCA TRX feature, TCH is allocated according to the DFCA TCH allocation and Energy Opti-mized TCH Allocation is not performed.

• BSS21391: DFCA support for OSCThe DFCA support for OSC feature enables the combined use of the Orthogonal Subchannel (OSC) feature and DFCA. It optimises the radio resource allocation for the Orthogonal Subchannel (OSC) feature by employing the DFCA processes. With the DFCA feature OSC packing rate is higher than without, due to improved quality in the network. This feature supports both OSC Half Rate with SAIC MS and OSC Full Rate with SAIC MS features. Combining OSC and DFCA, the OSC channel specific requirements is accounted for during optimisation of the radio channel, training sequence and user pair selections. Two main areas of improvement interact in a symbiotic manner. Firstly, the OSC feature generates more voice channels, that is, effectively increasing the probability and possibility for DFCA to optimise the resource allocation. Secondly, OSC has associated specific channel C/I requirements, and DFCA is specifically designed to locate the most suitable resource allocation. Thus, substantial gains are obtained through employing DFCA along with OSC.

2.11 Impact on mobile stationsNo impact.

DN03282742 29


DFCA hopping DFCA mode

Id:0900d8058058fb84Confidential

3 DFCA hopping DFCA modeDynamic Frequency and Channel Allocation (DFCA) provides a DFCA frequency hopping mode that allows dynamic timeslot-specific mobile allocation (MA) list and mobile allocation index offset (MAIO) settings, offering a higher degree of freedom for the DFCA algorithm to select the most suitable radio channel for each connection.

DFCA hopping is based on the basic principle of synthesised frequency hopping, where the transceiver (TRX) unit changes the used frequency according to the given hopping sequence. The difference when compared to the traditional radio frequency hopping (RF hopping) mode is that with DFCA hopping, the TRX supports independent cyclic hopping sequences that can be freely selected for each timeslot at channel activation. With RF hopping, the used hopping sequence is the same for all timeslots and it cannot be changed dynamically without BTS locking. With DFCA hopping, the BSC can freely select the MA list, MAIO and training sequence code (TSC) for each traffic channel (TCH) activation, allowing the DFCA algorithm to choose the most suitable radio channel for each new connection based on carrier-to-interference ratio (C/I) criteria. This full freedom in channel selection allows DFCA to achieve the best performance with DFCA hopping mode.

The DFCA hopping mode is only applied in the TRXs dedicated to DFCA use (DFCA TRXs). The BCCH TRX is always in non-hopping mode and the other regular TRXs can use RF hopping or operate on a fixed frequency without frequency hopping. Since the DFCA algorithm takes care of selecting the most suitable frequency hopping parameters for each connection, there is no need to plan frequencies or frequency hopping (FH) parameters for the DFCA TRXs, as each timeslot in a DFCA TRX can use any MAIO and any of the DFCA MA lists. However, the broadcast control channel (BCCH) TRX needs to be assigned a frequency and the regular TRXs (if they exist) also need to be assigned a frequency or the frequency hopping parameters. The general configuration of DFCA hopping BTS is presented in the figure Example of BTS configuration in DFCA hopping mode.

Figure 4 Example of BTS configuration in DFCA hopping mode

BTS

BCCHNo FH

Regular TRX(optional)

No FHor RF FH

DFCA TRX

BCCH SDCCH GPRS/EDGE territory

SDCCH SDCCH GPRS/EDGE territory

DFCA TRX

DFCA TRX

DFCA TRX

Ts levelMA list,MAIO,TSCsettings,HSN=0

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DFCA channel allocation algorithm

4 DFCA channel allocation algorithmThe DFCA channel allocation algorithm is responsible for obtaining the carrier-to-inter-ference ratio (C/I) estimations and performing channel allocation decisions based on those estimations. The flowchart of the channel selection process is shown in figure DFCA channel selection process.

Figure 5 DFCA channel selection process

4.1 Properties of cyclic frequency hoppingBSS synchronisation leads to controlled time division multiple access (TDMA) frame alignment in all BTSs. Generally, the timeslots are coincident so that timeslot 0 occurs simultaneously in all BTSs although it is recommended to shift the TDMA frame align-ment by one timeslot to reduce the interference load on SACCH channels. For more information, see Timeslot offset for better FR SACCH performance.

Calculate BIM scaling factor

Pick TSL, MA and MAIO

Incoming DL&UL check andtransmit power setting

Outgoing DL&UL check

Determine C/I differencefor this TSL, MA and MAIO

All channelschecked

No

Yes

No

Yes

Choose the most suitable

Determine TSC

Above softblocking threshold Block

INPUTS

For each connection

MS measurementreport

For each DFCA BTS

For each BSC

DFCA RR table

DFCA adj-channellookup table

IncomingBIM

OutgoingBIM

C/N check for cell access

Allocate channel

MA, MAIO, TSL,TSC & power level

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DFCA uses cyclic frequency hopping. The cyclic frequency hopping combined with BSS synchronisation and TDMA frame number control means that the frequency usage of every connection is orderly and repetitive, allowing DFCA to have accurate interference control despite the use of frequency hopping.

In cyclic frequency hopping mode, the mobile allocation (MA) list frequencies are used sequentially from the lowest to the highest frequency changing to the next MA list fre-quency for every new TDMA frame. After the highest frequency, the hopping sequence returns to the lowest one. The frequency used in a TDMA frame is calculated with the following equation:

Frequency = (FN + MAIO ) mod MA_length

If two connections (A and B) that use the same timeslot also use the same MA list and the used TDMA frame numbers (FN) and mobile allocation index offsets (MAIOs) satisfy the following equation:

(FNA+ MAIOA) mod MA_length = (FNB+ MAIOB) mod MA_length

the two connections (A and B) always use the same radio channel at the same time and are, therefore, potential co-channel interferers to each other. This is illustrated in figure Principle of cyclic frequency hopping.

Figure 6 Principle of cyclic frequency hopping

freq

Connection

time

Fixedinterference

relations

Interferingconnection

freq

time

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Differences in the TDMA frame number cause offsets in the cyclic frequency hopping sequence. Offset in the frame number means similar offset (modulo MA list length) in the MAIO of the interfering connection as illustrated in figure Interference relations with FN offsets, where the arrows of the circled frequency numbers indicate a co-channel relation. Therefore, a co-channel interference condition exists between connections A and B if the same DFCA MA list is used for both connections (A and B) and the following equation holds true:

(FNA+ MAIOA) mod MA_length = (FNB+ MAIOB) mod MA_length

Figure 7 Interference relations with FN offsets

The deterministic nature of the cyclic frequency hopping when combined with BSS syn-chronisation and TDMA frame number control means that the interference relations closely resemble the situation in a non-hopping network. The radio channel used by each connection at any moment can be calculated on the basis of the used MA list, MAIO, and TDMA frame number. If the connections use the same MA list and the com-bination of used MAIOs and frame numbers is such that co-channel interference occurs, it then occurs constantly all the time for every single burst.

Continuous adjacent channel interference occurs also in the case of MA lists containing adjacent frequencies, provided that the MA lists are of equal length.

4.2 Interference control principleThe DFCA channel selection decisions are based on C/I criteria. Several C/I estimations are produced for each available radio channel. The incoming C/I describes the interfer-ence coming from existing connections that would affect the new connection for which the channel assignment is being performed. The new connection may also cause inter-ference to existing connections using the same or an adjacent radio channel. This is

Cyclic FH without frame number offsets Cyclic FH with frame number offsets

50 52 54 56

0 1 2 3

54 56 50 52

MAIO

MA list 1FN=n

MA list 1FN=n+2

MA list 1FN=n+1

MA list 1FN=n+3

52 54 56 50

0 1 2 3

56 50 52 54

MAIO

MA list 1FN=n

MA list 1FN=n

MA list 1FN=n+1

MA list 1FN=n+1

50 52 54 56

0 1 2 3

50 52 54 56

MAIO

52 54 56 50

0 1 2 3

52 54 56 50

MAIO

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examined by determining the outgoing C/I for every potentially affected existing connec-tion. Both downlink (DL) and uplink (UL) C/I are estimated separately for both outgoing and incoming interference, as illustrated in figure DFCA C/I estimations.

The C/I estimation relies on the fact that the interference relations in a DFCA network are stable and predictable because of BSS synchronisation and controlled use of cyclic frequency hopping. The C/I estimation is performed by combining information from several sources, such as the following:

• mobile station (MS) measurement reports • background interference matrix (BIM) • DFCA radio resource table • DFCA adjacent channel lookup-table

The information that DFCA uses is illustrated in figure Information used by DFCA.

Figure 8 Information used by DFCA

MS measurement reportsThe MS measurement reports are the key input in the C/I estimation. Each MS on a ded-icated channel sends measurement reports to the BSC every 0.48 seconds. The MS measurement report includes the serving channel signal level and the broadcast control channel (BCCH) signal levels of the strongest neighbour cells.

The potential DL C/I towards each of the neighbour cells can be determined by calculat-ing the measured difference between the serving channel signal level and the neighbour cell signal level. Also the possible serving channel downlink power reduction should be accounted for, as shown in the following equation:

C/IDL = RXLEVservingTCH + PWR_reductionDL - RXLEVneighbourBCCH

This C/I represents the worst scenario C/I that would become reality if in the neighbour cell there were an interfering connection and transmission with full power on the same radio channel that is also used in the serving cell.

Non-real time information

Near real time information

real time information

Radio channel usage information

DFCA RRM

Background Interference Matrix

MS measurement reports

UL/DL PC power reductions

Radio channel selection

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Background interference matrixA background interference matrix (BIM) is used to identify all the potentially interfering DFCA neighbour cells. A C/I estimate between the serving cell and the neighbour DFCA cells is saved to the BIM.

The BIM is based on the DL signal level data that the have reported for the serving and the neighbour DFCA cells. It is long-term statistical data that gives a general cell-level view to how the MSs typically experience the signal level ratio between the serving cell and a neighbour cell.

The BSC generates two BIM tables for each DFCA cell:

• incoming interference BIM table that lists the potentially interfering surrounding cells • outgoing interference BIM table that lists the potentially interfered surrounding cells

In addition to these BIM tables the BSC builds and maintains a candidate cell table that is used to identify undefined neighbour cells that the MSs possibly report. The candidate BIM table is based on the neighbour cells' BIMs.

For more information, see DFCA cell identification process.

The BSC starts to create and update the BIM tables automatically as soon as the operator changes the value of the DFCA mode parameter of a BTS to 'standby'. For more information, see BIM update process.

Based on the signal level data reported by the MSs in a cell, the BSC concludes the level of interference each reported neighbour cell is causing for the serving cell. The incoming interference BIM table of the serving cell is formed based on the collected samples of the interference from each neighbour cell that is regarded as a significant interferer.

The generation of the BIM tables can be followed with the EQI command. An example of incoming interference BIM table is shown in the following MML printout:

SEG-0040

BACKGROUND INTERFERENCE MATRIX DATA

INCOMING BACKGROUND INTERFERENCE TABLE

BCCH NCC BCC LAC CELL BTS C/I SIGNALLINGFREQ CODE CODE CODE ID ID RATIO POINT CODE===== ==== ==== ===== ===== ==== ===== ========== 102 5 4 10 1050 12 10 ------ 115 2 2 10 1060 256 18 ------ 30 1 8 20 0040 1000 8 ------

Each interfering neighbour cell is identified by its location area code (LAC), cell identity (CI), and BCCH frequency and BSIC parameter (which is composed of the NCC and BCC parameters). The level of interference is reflected in the C/I value listed for each interfering cell. For the interfering cells controlled by the same BSC, the segment identifier is in the range of 1-4200. If the segment identifier is missing, the inter-fering cell is controlled by another BSC.

The C/I is defined as the value that is exceeded for γ percent of the time based on long term MS measurements statistics gathered from all connections in the cell. The γ is a BSC level parameter BIM confidence probability.

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For more information, see BIM update process.

In the BIM update process, the BSC detects the neighbour cells causing interference that is regarded as significant from the DFCA algorithm point of view. This means that when making channel allocation in DFCA transceivers (TRX) of a DFCA cell, the DFCA algorithm has to be aware of and take into account the resource situation in the cells included in the BIM tables of the DFCA cell. For the interfering cells controlled by the serving BSC, the radio resource data is automatically available. For the interfering cells controlled by other BSCs, a separate interference relation needs to be set up over the BSC-BSC interface. Based on this interference relation, the DFCA algorithms in differ-ent BSCs exchange radio channel usage information to keep each other updated in real time.

The BSC that controls a DFCA cell where significant interference from an external neighbour DFCA cell is detected sets up the interference measurement relation to the neighbour BSC in question and between the two DFCA cells. The local BSC forwards the calculated statistical C/I ratio of the two cells to the interfering BSC, which saves the information in the outgoing interference BIM of the interfering cell.

As mentioned above, an inter-BSC interference measurement relation is always set up by the end experiencing the interference. The relation has always a defined direction. If there are two cells, each controlled by a different BSC, and both cells detect the other one as interfering, measurement relations are set up in both directions.

In cases where both the interfered and the interfering cell are controlled by the same BSC, no separate procedure is needed to update the interfering end. The BSC saves the C/I both in the incoming interference BIM table of the interfered DFCA cell and in the outgoing interference BIM table of the interfering DFCA cell as soon as it detects the local interference relation.

BIMFIL

The content of the incoming interference BIM tables of the DFCA cells is saved to a disk file. The items to be permanently saved are:

• BCCH • BSIC • C/I • Segment id • LAC • CIThe information is updated on the disk every time a change in the fields above takes place. After a marker and cellular management unit (MCMU) restart, the BSC reads the saved BIM tables from the file, enabling an instant recovery of DFCA employment. BIMFIL is read from the file when the state of the BSC licence is changed from 'off' to 'conf' or 'on'.

DFCA radio resource tableThe C/I estimate, which the BSC calculates between the serving cell and a neighbour cell, is realised only if there are ongoing connections using the same radio channel in both of these cells. Therefore, after calculating the C/I values for potential interference coming from the neighbour cells, the DFCA algorithm uses the real-time radio channel usage information to determine the actual C/I.

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The DFCA radio resource (RR) table contains the real-time DFCA channel usage situ-ation in each DFCA cell. Each ongoing connection on a DFCA TRX is listed in the table, together with the information of values for the following:

• RR table index • DFCA segment • DFCA TRX index • DFCA MA ID • DFCA timeslot • DFCA sub-channel • DFCA MAIO • training sequence code • C/I target • soft blocking C/I limit • UL power reduction* • DL power reduction* • serving channel DL RXLEV* • serving channel UL RXLEV* • BIM scaling factor* • DL C/I target • DL soft blocking C/I limit • number of neighbours in a measurement list • BCCH frequency, BSIC, LAC, CI & C/I for up to 20 neighbour cells* (based on mea-

surement reports from the connected MS)

*) the value is updated periodically during the connection

Most of the connection-specific data is constant and remains as it is when saved in the beginning of a connection. The power level, signal level, and neighbour cell C/I informa-tion of every ongoing DFCA connection are also updated during the connection. The handover and power control algorithm of the BSC updates this data every five seconds to the DFCA algorithm. Therefore, this information is not available in absolute real time. However, this small delay has not been found to degrade the performance in any signif-icant way.

The DFCA algorithm uses the power level reduction information of an ongoing interfer-ing connection to make the C/I estimate more accurate, as it is otherwise based on the full power assumption. Ignoring the used power control level leads frequently to too pes-simistic C/I estimates when power control is used.

In addition to maintaining the channel usage information for the cells that are controlled by the BSC in question, the BSC maintains the channel usage information for all the sig-nificant external DFCA cells (controlled by other BSCs) that the MSs have reported about in the cells of the local BSC.

The local BSC sets up external interference measurement relations towards external interfering cells in other BSCs. Neighbour BSCs set up external measurement relations towards the cells controlled by the local BSC whenever they detect these interfering in their own cells. Based on the external measurement relations, the DFCA algorithms in different BSCs exchange channel usage information, power control information, and signal level information over the BSC-BSC interface to keep each other updated in real time or nearly in real time.

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The DFCA radio resource table is maintained and used internally by the DFCA algorithm in the C/I estimation process. The user has a access to this data via the BSC Radio Resource Monitoring service terminal extension. For more information, see BSC Radio Resource Monitoring under Reference.

DFCA adjacent channel lookup-tableAdjacent frequencies may occur within a DFCA MA list and also between two different DFCA MA lists. When taking into use and out of use DFCA MA lists, the BSC automat-ically updates an adjacent channel lookup-table that indicates which DFCA MA list and MAIO combinations may cause adjacent channel interference to each other.

The BSC does not automatically update an adjacent channel lookup-table if the follow-ing rules are broken:

• Any DFCA frequency can only be used on one DFCA MA list which is in 'in use' state.

• If any two DFCA MA lists contain frequencies that are adjacent to each other, the two DFCA MA lists are considered adjacent. Adjacent DFCA MA lists which are in 'in use' state must have the same length (that is, contain the same number of fre-quencies).

An adjacent channel lookup-table is updated for DFCA MA lists when a DFCA MA list is set to 'in use' or 'out of use' state and the rules mentioned above are not broken. This table is maintained and used internally by the DFCA algorithm in the C/I estimation process. The user has an access to this data via the BSC Radio Resource Monitoring service terminal extension.

4.3 DFCA C/I estimation processIn the C/I estimation process, the DFCA algorithm determines the interference that the new user would have with different available timeslot, DFCA MA list, and MAIO combi-nations. For the C/I estimation of an available timeslot, DFCA MA list, and MAIO com-bination the DFCA algorithm searches all BIM neighbours to identify interference caused by the co- and adjacent channel connections. In case of adjacent channel inter-ference, 18 dB offset is used because of a lower interference relation. For each combi-nation, the most restrictive minimum C/I difference is determined, that is, the lowest minimum C/I difference from the C/I estimations for the following:

• incoming DL interference • incoming UL interference • outgoing DL interference • outgoing UL interference

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Figure 9 DFCA C/I estimations

Step 1: BIM scalingThe C/I values in background interference matrix (BIM) tables are based on long-term statistics of all connections in the cell. This statistical nature means that the real C/I of one user towards an interfering cell may be significantly different depending on the user's actual location. For example, if the user is located close to the serving BTS, the high serving signal level usually implies that the C/Is tend to be much higher than the statistical C/I values provided in the BIM tables.

BIM scaling is used to correct the statistical C/I values of BIM tables to better correspond to the user's actual situation. BIM scaling is based on comparing the measured C/I towards the neighbour cells included in the latest measurement report to the corre-sponding C/I values listed in incoming interference BIM table. From this comparison, the differences between the measured and the statistical C/Is can be determined. Finally, the BIM scaling factor corresponding to the average difference is calculated. This BIM scaling factor is then applied to all C/I values taken from the BIM table for C/I estimations for this connection.

Step 2: Incoming DL C/I estimationIn this step, the interfering co- and adjacent channel connections in the neighbour cells are identified and the level of interference coming from each potentially interfering neighbour cell is estimated. The algorithm goes through the cells listed in the incoming

BCCH, BSIC Measured C/I BIM C/I Δ C/I

102,23 8 dB 4 dB 4 dB

114,52 12 dB 7 dB 5 dB

104,12 12 dB 9 dB 3 dB

116,32 15 dB 11 dB 4 dB

108,12 19 dB 15 dB 4 dB

111,43 20 dB 15 dB 5 dB

Average Δ C/I (BIM scaling factor): 4 dB

Table 11 Example of the BIM scaling factor calculation

New connection Existing connection

BTS 1 BTS 6

Incoming DL

OutgoingUL

IncomingUL

Outgoing DL

DN03282742 39




interference BIM table and checks the DFCA radio resource (RR) table for ongoing co- and adjacent channel connections in these cells.

When an interfering connection is found, the latest MS measurement report is examined to see if a directly measured C/I value can be extracted from the measurement report. If the interfering cell is not reported in the latest measurement report, the C/I value from the incoming interference BIM table is used and scaled by the BIM scaling factor that was determined in step 1. The measured or the statistical C/I is adjusted by the actual DL transmit power reduction of the interfering connection that is available in the DFCA RR table.

The most significant incoming DL interference source is identified. If the incoming DL C/I for this interference source is above the target C/I set for the connection type of the new connection, the initial DL transmit power is reduced so that the final C/I corresponds to the target C/I. Note that power can be reduced 10 dB at the maximum. The minimum C/I difference corresponding to the difference between the C/I target and the final C/I caused by the dominant interference source is recorded. Typically, the initial DL transmit power level setting sets this minimum C/I difference to zero, but in high load situations the minimum C/I difference can even be negative, indicating that the C/I target is not achieved.

Step 3: Incoming UL C/I estimationThe UL C/I estimation cannot be done as accurately as the DL C/I estimation, as only DL measurements of the neighbour cell signal levels are available. As a consequence, the UL C/I estimation is based purely on the statistical C/I values available in the BIM tables. Although the BIM tables are based on the DL measurements, a reasonable esti-mation of the UL interference situation can still be derived, based on the fact that the propagation path of the incoming UL interference is the same as the propagation path of the outgoing DL interference.

To estimate the incoming UL C/I, the outgoing interference BIM is used. The estimate can be improved by accounting the relative location of the new connection in the cell that is reflected in the incoming interference BIM scaling factor. If the new user is located close to the cell site, the BIM scaling factor is a high positive value, reflecting that the serving signal path loss is low. If the new user is located at the cell edge, the BIM scaling factor may even be negative, reflecting a high serving signal path loss. The final UL incoming C/I estimate is derived by taking the C/I values from the outgoing interference BIM and scaling them using the incoming interference BIM scaling factor that was deter-mined earlier. Each UL interference contribution is adjusted by accounting for the possible UL transmit power reductions that are available in the DFCA RR table.

The most significant UL incoming interference source is identified. If the incoming UL C/I for this interference source is above the target C/I set for the connection type of the new connection, the initial UL transmit power level for the new connection is reduced so that the final C/I corresponds to the target C/I. Note that power can be reduced 10 dB at the maximum. The minimum difference between the C/ I target and the final C/I caused by the dominant interference source is recorded. Typically, the initial UL transmit power reduction sets this minimum C/I difference to zero, but in high load situations the minimum C/I difference can even be negative, indicating that the C/I target is not achieved.

Note that to enhance the Uplink Time Difference of Arrival (U-TDOA) positioning accuracy initial MS power control for emergency calls is not made as a default value.

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The initial MS power control for emergency calls is controlled by the BSC parameter delay of HO and PC for emergency calls (DEC).

Step 4: Outgoing DL C/I estimationIn this step, the co- and adjacent channel connections in the neighbour cells that may get DL interference from the new connection (=outgoing interference) are identified and the level of interference affecting each of these connections is estimated.

The algorithm goes through the cells listed in the outgoing interference BIM table and checks the DFCA RR table for ongoing co- and adjacent channel connections in these cells. When an interfered connection is found, the DFCA RR table record of the inter-fered connection is examined to see if a directly measured C/I value is available. If the directly measured C/I is not available, the C/I value from the outgoing interference BIM table is used. The value is scaled by the BIM scaling factor of the interfered connection that is listed in the DFCA RR table.

The measured or the statistical C/I is adjusted by the actual DL transmit power reduction that was determined in step 2 for the new connection. The maximum affected outgoing DL interference is identified by calculating the minimum C/I difference for each interfered connection, that is, the difference between the C/I target of the interfered connection (available in the DFCA RR table) and the C/I caused by the new connection. The minimum C/I difference is recorded.

Step 5: Outgoing UL C/I estimationIn this step, the UL interference that would be caused by the new connection to the ongoing connections in nearby cells is estimated. The outgoing UL C/I estimation exploits the fact that the interference propagation path of the outgoing UL interference is the same as the path of the incoming DL interference. Therefore, the incoming inter-ference BIM table is used.

For the outgoing UL C/I estimation, all the C/I values in the incoming interference BIM table are examined. Each C/I value in the incoming interference BIM table is scaled using the BIM scaling factor that is found in the DFCA RR table for the interfered con-nection in question. The UL interference estimate for each of the potentially interfered connection is adjusted by accounting for the possible UL transmit power reduction that was determined in step 3 for the new connection.

The maximum affected outgoing UL interference is identified by calculating the minimum C/I difference for each interfered connection, that is, the difference between the C/I target of the interfered connection (available in the DFCA RR table) and the C/I caused by the new connection. The minimum C/I difference is recorded.

HR-specific considerations in C/I estimationsWhen a half rate (HR) connection is interfering another HR connection, the DFCA inter-ference estimations and the channel search are made as usual. The DFCA resource table indicates the HR sub channels, making it possible to distinguish between two HR connections sharing the same timeslot.

Some special considerations have to be made when a HR connection disturbs a full rate (FR) connection and vice versa.

When a new channel assignment is made as a HR connection and an interfering con-nection uses FR, the DFCA interference estimations and the channel search are per-formed in the usual way related to the incoming interference.

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When a new channel assignment is to be made as a HR connection and an interfered connection uses FR, the resulting outgoing interference to the FR connection is present in every other burst. This means that the interference impact is reduced. This is taken into account in the DFCA algorithm by adding 3 dB to the estimated outgoing interfer-ence C/I when the interfered connection is FR.

When a new channel assignment is to be made as a FR connection and the interfering connection uses HR, the incoming interference for the new connection is split into two parts, each affecting every other burst. The channel search algorithm calculates the C/I values separately for both the interfering HR sub-channels. The resulting incoming C/I from each HR sub-channel is increased by 3 dB.

When a new FR connection interferes an ongoing HR connection, the estimated C/I value for the outgoing interference is used as it is, without any offsets.

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Channel ranking and selection

5 Channel ranking and selectionThe DFCA channel selection is based on the carrier-to-interference ratio (C/I) criteria. The aim is to optimise the C/I and, at the same time, adapt to the differences in the inter-ference tolerance of different user types. To achieve this target, C/I is defined for each of the user classes. The user classes and the default target C/I values are listed in table DFCA user classes.

In the C/I estimation process, the Dynamic Frequency and Channel Allocation (DFCA) algorithm determines the C/I ratio that the new user would experience with different timeslot, mobile allocation (MA) list, and mobile allocation index offset (MAIO) com-binations both in downlink (DL) and uplink (UL) direction. Also, the interference that existing connections in surrounding cells would experience from the new connection is estimated as C/I both in Dl and UL direction for all available channels. For each timeslot, MA list, and MAIO combination, the most restrictive minimum C/I difference is deter-mined.

In general, DFCA channels are divided into two groups according to the minimum esti-mated C/I of the channel:

• channels on and above the connection-type-specific target C/I level (minimum C/I difference >= 0)C/I difference is the difference to the target.

• channels below the target C/I level (minimum C/I difference < 0)

Channels on or above the target level are regarded as good channels and are always the primary target for channel allocation.

In handovers, there is also a third group available: channels with minimum C/I below the connection-type-specific soft-blocking limit parameter. Channels in this group can be allocated for handovers when there are no available channels with minimum C/I on or above the soft-blocking limit. Channels below soft-blocking limit are never allocated for call setup requests.

5.1 DFCA channel allocation methodsThe BSC offers the operator the possibility to select between two DFCA channel alloca-tion methods for selecting a traffic channel (TCH) from the set of available candidate channels that have different minimum C/I estimates. The primary method (method 0) aims at the best performance by maximising the C/I. The secondary method (method 1) aims at a TCH on the target C/I level.

The DFCA channel allocation method (DCAM) parameter can be used to select between the two channel allocation methods 0 and 1. In addition, there is also a third

User class Default C/I target

EFR/FR 14 dB

HR 14 dB

AMR FR 12 dB

AMR HR 12 dB

14.4 kbit/s data 16 dB

Table 12 DFCA user classes

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method that the BSC can automatically switch itself to use, regardless of the selections made by the operator if the processing load of the BSC reaches a critical level.

Method 0With this method the target is to have a channel with the highest minimum C/I difference. To find the channel with the highest C/I, the minimum C/I difference has to be deter-mined for all the available channels. Therefore, this method is computationally intensive. However, the channel search is stopped as soon as an interference free channel is found, meaning an MA, MAIO, and timeslot combination for which a co- or adjacent channel is not allocated in any of the cells found in the incoming or outgoing interference BIM tables.

With this method the power reduction is taken into account in the priorisation of candi-date channels on the target C/I level (minimum C/I difference = 0). On the target C/I level the channel with the highest power reduction (UL and DL summed) is selected.

Method 1With this method, the DFCA algorithm searches for a channel on the target C/I level. In this method, the searching for the channel search is stopped as soon as a channel on the target C/I level is found. If a channel on the target level cannot be found, the second-ary target is to have a channel with C/I as close above the target level as possible. Channels below the target C/I level are the last choice.

Method 1 aims at finding a channel without the need to search through all possible can-didate channels. This method is computationally less intensive, at least when network load is low.

As in method 0, the discovery of an interference free channel means that the channel search is stopped.

Overload protection method When the processing load of the BSC reaches a critical level, the BSC switches auto-matically to a channel allocation method where the target is to have a channel on or above the connection-type-specific target C/I level. Therefore, in processing overload situation the BSC interrupts the channel search as soon as a channel that indicates a positive or zero C/I difference is found. As with the other methods, when an interference free channel is found, the channel search is stopped.

After the automatic switch to the overload protection method, the BSC checks the pro-cessing load of the BSC regularly to detect if the processing load of the BSC has decreased below the critical level, enabling the return to the method preferred by the operator.

5.2 Soft blocking C/IIn addition to the C/I target parameter, each connection type (full rate (FR), half rate (HR), adaptive multi rate (AMR) FR, AMR HR, 14.4 data) has a soft blocking C/I threshold parameter. In the C/I estimation phase, if any of the four C/I estimates calcu-lated for a radio channel candidate drops below the soft blocking limit of the interfered connection, the radio channel candidate is regarded as soft-blocked and unsuitable for allocation.

If there are no acceptable candidate channels (for example, all the candidates fall below the connection-type-specific soft blocking C/I limit), the request is directed towards the

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regular resources of the cell. If there are no free timeslots on any regular transceiver (TRX) of the cell, the channel allocation request is rejected in the examined cell (DFCA soft blocking situation). Directed retry could still be used to move the call setup request to another cell.

For handovers, there is a special rule when a soft blocking limit is applied. Basically han-dovers do not increase the load of the network when compared with the new calls: after a handover, the average C/I of the network remains the same, but after a new call, the average C/I decreases. In the BSC, handovers are categorised into urgent and non-urgent handovers. Urgent handovers include handovers made because of quality reasons. Non-urgent handovers include handovers made to move a call out of the GPRS territory border to allow GPRS upgrade. Non-urgent handovers are typically han-dovers that move calls within a cell or between cells to allow more calls into the network and for this reason a soft blocking limit is used for those handovers. For urgent han-dovers, a soft blocking limit is not used.

In case of an intra-cell handover made because of interference, the DFCA algorithm avoids a situation where a handover is made from a bad channel to a worse one. The DFCA algorithm compares the C/I of the best new channel found and the C/I of the old channel. The handover is made only if the new channel is better than the old one.

5.3 Channel type preferenceIn full rate (FR) channel allocation, the permanent FR channels are preferred to the dual rate (DR) channels according to minimum C/I difference as follows:

In half rate (HR) channel allocation, the permanent HR channels are preferred to the half-occupied and idle DR timeslots according to minimum C/I difference as follows:

Free and good quality channels 1. FR channel with idle MA, MAIO combi-nation

2. FR channel with C/I difference >= 0

3. DR channel with idle MA, MAIO combi-nation

4. DR channel with C/I difference >= 0

Poor quality channels 5 FR channel with C/I difference < 0, but above the soft blocking C/I limit

6. DR channel with C/I difference < 0, but above the soft blocking C/I limit

Extremely poor quality channels (used in urgent and inter-BSC handovers)

7. FR channel with C/I difference < soft blocking limit

8. DR channel with C/I difference < soft blocking limit

DN03282742 45




5.4 Rotation in channel allocationThe DFCA algorithm uses the round robin method to circulate MA lists, MAIOs, and timeslots so that the searching is always started from the MA, MAIO, timeslot combina-tion following the one which was allocated the previous time.

This method makes it possible to allocate channels of equal quality for successive calls one by one using one phone (for example, testing situations). In addition, the MA, MAIO and timeslot combination spreading is better.

5.5 Training sequence code selectionAfter a suitable channel has been found, the BSC determines the most suitable training sequence code (TSC) by examining all the interfering connections. The BSC searches for the TSC that has been used by an interfering connection with the highest carrier-to-interference ratio (C/I). This means that for the selected mobile allocation (MA), mobile allocation index offset (MAIO), and timeslot combination, the minimum C/I dif-ferences are checked TSC by TSC and the one with the highest C/I difference is selected.

Free and good quality channels 1. permanent HR channel with idle MA and MAIO combination

2. permanent HR channel with C/I differ-ence >= 0

3. HR traffic channel (TCH/H) with idle MA and MAIO combination in half-occupied DR timeslot

4. TCH/H with C/I difference >= 0 in half-occupied DR timeslot

5. TCH/H with idle MA and MAIO combina-tion in idle DR timeslot

6. TCH/H with C/I difference >= 0 in idle DR timeslot

Poor quality channels 7. permanent HR channel with C/I differ-ence < 0 but above the soft blocking C/I limit

8. TCH/H in half-occupied DR timeslot with C/I difference < 0 but above the soft blocking C/I limit

9. TCH/H in idle DR timeslot with C/I differ-ence < 0 but above the soft blocking C/I limit

Extremely poor quality channels (used in urgent and inter-BSC handovers)

10. permanent HR channel with C/I differ-ence < soft blocking limit

11. TCH/H in half-occupied DR timeslot with C/I difference < soft blocking limit

12. TCH/H in idle DR timeslot with C/I dif-ference < soft blocking limit

46 DN03282742




The method of the TSC selection aims at avoiding the worst-case situation where a sig-nificant interference source uses the same training sequence code as the new connec-tion. A conflict with a significant interferer would cause the receiver to obtain an incorrect channel estimate and, therefore, lead to a link level performance degradation and a poor adaptive multi rate (AMR) link adaptation performance.

5.6 Forced HR modeDuring low traffic hours it is useful to prefer full rate (FR) mode as FR channels provide better subjective speech quality in these circumstances. In this situation, the existing cell load based rate selection between FR and half rate (HR) method is sufficient. DFCA is most advantageous when HR channels are used all over the DFCA area. This may lead to a situation where it is useful to use HR channels even if there are still sufficient hardware resources available in the cell. In this situation, the existing cell load based rate selection between the FR and HR method is not sufficient.

Forced HR mode is a method for channel rate selection between FR and HR, based on the average of the estimated incoming DL C/Is of DFCA allocations in a cell. The average DL C/I provides a good benchmark of the load of DFCA frequencies and, there-fore, it can be used to trigger HR allocation. When HR allocation is triggered in the cell because of forced HR mode, it is triggered also in the interfering neighbour cells. Forced HR mode provides better HR performance and improves the C/I situation in the cell and its BIM neighbours.

There are band-specific thresholds for HR and AMR HR modes. These thresholds are controlled with the following BTS-level parameters:

• forced HR mode C/I threshold (FHT)

• forced AMR HR mode C/I threshold (FAHT) • forced HR mode C/I averaging period (FHR)

• forced HR mode hysteresis (FHH)

Note that if there are several BTS objects in a band in the cell, the value of the parameter has to be the same for all the BTSs in the band.

DFCA algorithm calculates the C/I over the averaging period and if the C/I is below the threshold, forced HR mode is triggered. Forced HR mode ends when the average C/I reaches the threshold + defined forced HR mode hysteresis.

Figures Good cell average C/I, forced HR mode 'off' and Bad cell average C/I, forced HR mode 'on' illustrate the triggering of forced HR mode.

DN03282742 47




Figure 10 Good cell average C/I, forced HR mode 'off'

Figure 11 Bad cell average C/I, forced HR mode 'on'

In a cell, the following band-specific forced HR modes are possible:

• no forced HR mode • forced HR mode for non-AMR channels • forced HR mode for AMR channels • forced HR mode for non-AMR and AMR channels

When a cell's forced HR mode is, for example, for AMR HR, HR channels are allocated for all AMR MSs, if available. FR channels can be still be allocated for non-AMR MSs.

If there are both broadcast control channel (BCCH) and non-BCCH bands in a cell, the band for circuit-switched (CS) data calls is selected in the following order of prefer-ence:

1. the band without an active forced HR mode2. the band with either an active HR mode or an active AMR HR mode3. the band with both an active HR mode and an active AMR HR mode

Average C/I in cell A

Forced HR modeON threshold

Forced HR modeOFF threshold

Hysteresis

Cell level average C/I0

A

Average C/I in cell A

Cell level average C/I0

A

48 DN03282742


Id:0900d805808cdb39Confidential

BIM update process

6 BIM update processTo have a comprehensive view of the Dynamic Frequency and Channel Allocation (DFCA) radio environment, the BSC collects long term statistical data on how different cells using DFCA generate interference to each other in the network. This data is col-lected by the background interference matrix (BIM) update process.

6.1 C/I statistics collectionThe BIM update process is a repeated periodic activity that is based on the signal level measurement reports from the mobile stations in each DFCA cell. The operator defines a DFCA cell with a BTS parameter DFCA mode (DMOD). BIM update activity takes place if the value of this parameter of a BTS is 'standby' or 'DFCA hopping'.

In the BIM update process, the BSC collects in each DFCA cell samples of carrier-to-interference ratio (C/I) towards each neighbour cell that the MSs in the cell report about. The BSC calculates C/I samples of every received MS measurement report from an active traffic channel (TCH) connection in a DFCA BTS. A sample of C/I is deter-mined as the downlink (DL) signal level difference between the serving cell and a neigh-bour cell. If downlink power control is used on the serving channel, the applied power reduction is taken into account to determine the maximum potential level of the serving TCH as this is compared to the broadcast control channel (BCCH) signal of a neigh-bour cell.

C/I statistics are needed only for the neighbour cells that use DFCA. For the neighbour cells that are controlled by the same BSC and do not use DFCA, the C/I sampling can be ignored. For neighbour cells controlled by another BSC, the check on DFCA use is made only at the end of each BIM update period. Therefore, the C/I statistics have to be collected normally for them.

6.2 Processing of the C/I statistics for BIM updateAt the end of a defined BIM update period, the BSC examines the C/I data collected during the period for each neighbour cell. If the total number of C/I samples collected during the BIM update period for a neighbour cell is less than 1000, the cell is excluded from the BIM update process. This is to ensure the statistical reliability of the BIM. The BIM update period (BUP) parameter is a BSC-level user-defined parameter. The value of the parameter ranges from 10 minutes to 24 hours. BIM updates can also be frozen completely, if needed.

For each neighbour cell that has a sufficient number of samples collected at the end of the BIM update period, the BSC combines the information of the samples to determine a general cell level view about the interference from the neighbour cell in question.

The C/I value combining is started with the value γ which is a BSC-level parameter BIM confidence probability (BCP). The default value of the parameter is 80 percent. The BSC checks first among the C/I samples what is the C/I value that is exceeded for γ percent of the samples for this neighbour in the DFCA cell. This means that the C/I towards the neighbour cell is better than the defined initial C/I value for γ percent of the users.

After defining the initial C/I value the sample amount between different neighbour cells is taken into account. The C/I sample amounts from different neighbour cells can vary quite a lot. This is due to the fact that some neighbour cells are major interferers which

DN03282742 49


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cause interference to the whole area of the cell, while others cause interference just to a small area of the cell. Despite the low sample amount of some cells the C/I can still be very low according to the C/I samples. In the BIM table this means a strong interferer. As the BIM table should show a general view about the C/I values, the C/I values are scaled based on the C/I sample amounts.

The scaling is controlled by the UTPFIL parameters:

• RCS_DFCA_SAMPLE_VALUE_PRM_C, which is defined as a certain C/I value between 0-35 dB (the default value being 35 dB).

• RCS_DFCA_SCALING_FACTOR_DEF_C, which is defined as a per cent value between 0-100 % (the default value being 7 %).

The BSC scales the neighbouring C/I values by using the highest C/I sample amount of the cell. At first, the BSC determines the neighbour cell that has the highest C/I sample amount of the cell. Then, it calculates the C/I sample difference for every neighbour cell. The final C/I value for the neighbour cell is a weighted average between the initial C/I with its real C/I sample amount and the decibel value of the RCS_DFCA_SAMPLE_VALUE_PRM_C parameter and a percentage of the C/I sample dif-ference. The percentage value is defined with the RCS_DFCA_SCALING_FACTOR_DEF_C parameter.

The result is a C/I level that the mobile stations of the DFCA cell experience in general towards the neighbour cell.

6.3 Creating a new BIM entryBased on the results of the BIM update process, the BSC gets information on the neigh-bour DFCA cells that generate interference to a particular DFCA cell. When the DFCA algorithm makes channel allocation decisions in the DFCA cell, it takes into account the interference coming from each interfering neighbour cell. For this purpose, the interfer-ing cells and the level of interference each cell is causing are saved in the incoming interference BIM table of the DFCA cell.

Before a neighbour cell is added to the incoming interference BIM table, the BSC examines the related C/I value to decide if the interference caused is actually significant. The significance of interference is decided based on a user-defined BSC level parame-ter BIM interference threshold (BIT). The default value of the BIT parameter is 35 dB. This means that all the measured BIM neighbours are regarded as significant interferers. The maximum C/I value in the BIM table is 35 dB. The value is saved in the BIM table in the case that the measured C/I is higher than 35 dB. When the BIM table includes all possible interfering neighbour cells, the optimal DFCA performance can be achieved.

Insignificant BIM neighbours can be dropped out of the BIM table by setting the BIM interference threshold lower. So, unnecessary signalling and processing load can be avoided in the BSC. If the C/I value is greater than the value of the BIM interference threshold (BIT) parameter, the interference is regarded as insignificant and no new BIM entry is created in the incoming interference BIM.

As the DFCA algorithm takes also into account the interference that a new connection would cause to the surrounding cells, the BSC must know for each DFCA cell the neigh-bour cells to which the cell is generating interference. For this purpose, the C/I defined in the BIM update process in an interfered cell is also saved in the outgoing interference BIM table of an interfering cell.

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If an interfering cell is controlled by another BSC, the local BSC informs the neighbour BSC about the detected interference relation and the related C/I value between the inter-fered and the interfering cell. This takes place as the local BSC establishes a measure-ment relation over the BSC-BSC interface to the other BSC and between the interfered and the interfering cell. At this point, the remote interfering cell either accepts or rejects the measurement relation establishment request.

If the remote interfering cell is not using DFCA (the value of the BTS parameter DFCA mode (DMOD) is 'off'), it rejects the measurement relation establishment request. This leads to the removal of the interfering cell and the related C/I value from the incoming interference BIM table of the interfered cell that initiated the relation establishment in the other BSC.

If the remote interfering cell is regarded as a DFCA cell (the value of the BTS parameter DFCA mode (DMOD) is 'standby' or 'DFCA hopping'), the BSC that controls the cell confirms the measurement relation and saves the information about the external inter-fered cell and the related C/I in the outgoing interference BIM table of the interfering cell.

The BSC can store up to 100 neighbour cell entries for incoming and outgoing BIM tables in every cell. In some circumstances the outgoing BIM table can be very long or even full of entries for a cell. This means that the cell causes interference to a wide area, and hence unnecessarily performance degradation in neighbour sites. This can be a caused by a non-optimal antenna direction or too high power in the BTS.

6.4 Updating an existing BIM entryBy updating the BIM tables periodically, the changes in the traffic distributions of the DFCA cells can be taken into account. This ensures that the C/I values in the BIM reflect the current reality as closely as possible. For example, the traffic distribution in city center cells may change significantly after people leave work. The value of the BIM update period (BUP) parameter that controls the frequency of the BIM update process can vary from 10 minutes to 24 hours (the default value is 2 hours).

If the C/I from the latest BIM update period and the old value saved in the incoming inter-ference BIM table differ from each other, the information of the two values is combined. This combining forms a statistical filtering process that controls the rate of change of the BIM value. The combining is controlled by a BSC-level, user-defined BIM update scaling factor (BUSF) parameter, denoted as α. The parameter can have values between 0 and 1. It identifies the impact of the latest C/I distribution when it is combined with the long term distribution. The default value for α is 0.5. The combination of the new and the old BIM value is done as follows:

The BSC saves the updated C/I value related to the neighbour cell in question in the incoming interference BIM table of the interfered cell. The BSC also updates the related BIM entry in the outgoing interference BIM table of the interfering cell, if this is controlled by the same BSC. In the case of an external interference relation, the BSC controlling the interfered cell sends a BIM update request to the BSC controlling the remote inter-

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BIM update process


fering cell. Based on the request, the remote BSC updates related BIM entry in the outgoing interference BIM table of the interfering cell.

6.5 Removing a BIM entryIn a constantly changing radio network environment, a cell that was previously found to be a relevant interference source may turn insignificant to be considered in DFCA C/I estimations. In this case, the related interference relation must be terminated.

There are two main reasons to remove a BIM entry from the BIM table:

• If an interfering cell that is included in the incoming interference BIM table of an inter-fered cell is not included in the results of a certain amount of successive BIM updates for the interfered cell, the interference relation is terminated. The number of missing BIM updates that are allowed for an interfering cell is defined by the operator with a BSC level parameter BIM update guard time (BUGT).It is recommended that the BIM update guard time (BUGT) parameter is set to a value high enough so that temporary faults and maintenance outages do not cause the termination of the interference relation. In general, it takes one BIM update period to get a removed BIM entry back to the BIM tables, because new entries are added only at the end of each BIM update period.For example, if the value of the BIM update period (BUP) parameter is 1 hour and the value of the BIM update guard time (BUGT) parameter is 48, the inter-ference relations are preserved for 1 hour x 48 = 48 hours before they are deleted as a consequence of a cell being out of service. It is also possible to allow indefinite outages by setting the value of the BIM update guard time (BUGT) parameter to 63.The interference relation between two cells and the related BIM table entries are also deleted if DFCA is turned off at either end of the relation.

• If the C/I from the latest BIM update period combined with the old value saved in the incoming interference BIM table result in a new C/I value that is greater than the level indicated by the BIM interference threshold (BIT) parameter, the interfer-ence from the interfering cell in question has become insignificant for the DFCA algorithm. The BSC removes the related BIM entry immediately from the incoming interference BIM table of the interfered cell. The BSC also removes the related BIM entry from the outgoing interference BIM table of the interfering cell, if this is con-trolled by the same BSC.In the case of an external interference relation, the BSC that controls the interfered cell sends a measurement relation termination request to the BSC controlling the remote interfering cell. The interfered cell and the related C/I value are removed from the outgoing interference BIM table of the interfering cell in the remote BSC.

6.6 Segment environmentDFCA is controlled on a per BTS basis. The BIM tables that are formed based on the collected C/I data are, however, maintained on cell level (=segment level) between the interfered and the interfering cells. This has significance in segment environment where cells can have several BTSs (with Multi BCF Control in BSC and Common BCCH Control in BSC).

In a multi-band segment, the C/I information is collected only on the frequency band that corresponds to the BCCH frequency band of the neighbour segment that the MS reports

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about. The C/I relation defined between two segments on one frequency band is also used on the secondary frequency band between the segments, if there are such resources in both segments.

The BSC collects the information on the DFCA bands used in each segment. The C/I relation can be accepted if DFCA is used on the same band in the interfering cell and the interfered cell. The DFCA bands are taken from the BTSs that have the DFCA mode (DMOD) parameter value as 'standby' or 'DFCA hopping'. When the status of the DFCA bands changes, the neighbour cells are informed. The cells that have received this infor-mation check the suitability of the bands and start disassembling the C/I relation, when necessary.

As DFCA mode is controlled BTS by BTS, a configuration is possible where only the secondary frequency band of a segment is used for DFCA. As the C/I is determined based on the BCCH of an interfering common BCCH controlled segment, it requires that the necessary DFCA C/I data is collected in the BCCH band of the interfered segments. In a case like this, the operator is required to set the BTS of the BCCH band in 'standby' DFCA mode to have the BIM update procedure working properly.

For interference relations where the interfered single band cell and the interfering multi-band cell BCCH are on different frequency bands, the BSC makes a correction by taking into account the signal level difference between the bands in the interfering cell. The cor-rected C/I value is determined by adding the non BCCH layer offset (NBL) param-eter of the non-BCCH band BTS to the original C/I value.

In the case of an external interference relation, the final correction in the C/I value because of the frequency band differences is made in the BSC that receives the mea-surement relation request and controls the interfering cell. Because the final C/I is deter-mined at the BSC that controls the interfering cell, the final decision on the significance of the detected interference is also decided there. Therefore, the decision on the inter-ference being insignificant can sometimes be made only at the receiving end of a mea-surement relation request. In such a case, the measurement relation request in question is rejected.

It should be noted that DFCA uses the BIM interference threshold (BIT) parameter that is valid in the BSC of the interfering cell. The DFCA algorithm assumes that the threshold values in all the BSCs of the network are the same. However, it is the operator's responsibility to set equal values throughout the network.

The segment level C/I definition of BIM update process does not take into account the differences between segment's BTSs if they are of different BTS site types in the case of Multi BCF Control in BSC.

6.7 BCCH frequency listTo collect reliable C/I statistics and create complete BIM tables where all the relevant potentially interfering cells are listed, the MSs should be able to measure the BCCH fre-quencies of all surrounding cells.

The MSs measure the BCCH frequencies that have been indicated by the BSC. Nor-mally, the BCCH frequency list given to the MSs in active state only contains the BCCH frequencies of the cells that the operator has defined as adjacent. This is sufficient for handover purposes, but if a nearby cell is not defined as an adjacent cell, the MSs never measure the signal level of such a cell. This causes the cell to be an invisible interfer-ence source that cannot be taken into account in the DFCA C/I estimations. If the level

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BIM update process


of interference from the unknown interference source is significant, the performance of DFCA is degraded.

To avoid DFCA performance degradation, the operator should create a BCCH fre-quency list that includes all the BCCH frequencies used in the area. The operator should attach this list as the BCCH frequency list to be used for the active state MSs in the DFCA cells.

When MSs can monitor and measure all the possible BCCH frequencies, the risk for some potential interfering cells of being excluded from the decisions made by the DFCA channel allocation algorithm is minimised. If all possible BCCH frequencies do not fit to the BCCH frequency list, the operator should leave some space for the BCCH frequency list. In that case the BSC rotates the BCCH frequencies to collect all possible interfer-ence sources. The rotation is done in 10 minute cycles by looking for new BCCH fre-quencies to be listened from the BIM candidate table.

6.8 DFCA cell identification processAll the surrounding cells that may cause interference or may be interfered by calls in the serving cell have to be collected into the BIM table. In a continuous DFCA area there can easily be several hundreds of cells in many BSCs so it is not possible to identify all cells with only BCCH and base station identity code (BSIC) codes. Therefore, also the location area code (LAC) and cell identity (CI) codes are needed. As MSs can only report BCCH and BSIC codes to which they can listen, the BSC has to map the codes reported by the MSs into a full cell ID that consists of the BCCH, BSIC, LAC, and CI codes.

For those cells that are configured as handover neighbour cells, the BSC uses neigh-bour cell definition and maps the reported BCCH and BSIC codes into the defined neigh-bour cell. With these neighbour cell definitions the BSC gets some neighbours into the BIM table that are properly identified. In addition to those neighbours, the MSs also report undefined BCCH and BSIC codes which are needed to identify and map the MSs into the right cell. Based on the BIM neighbours that are identified by using neighbour cell definitions, the BSC builds up a BIM candidate table which is used to identify unde-fined neighbour cells. The BSC collects DFCA cell identifications into that table from its handover neighbour cells' BIM tables. When the BSC receives a measurement from an undefined BCCH and BSIC, it uses this candidate BIM table to map the BCCH and BSIC codes into LAC and CI. This kind of a limited set of cell identifications allows the BSC to map the reported BCCH and BSIC codes into the right and closest cell even if the same code would be used more than once in the BSC.

6.9 BCCH and BSIC conflict managementAs MSs are able to report only the combination of BCCH frequency and BSIC, there may in some cases appear conflicts that prevent the normal maintaining of the detected interference relations in the BIM tables. An existing interference relation may become ambiguous or it may not be possible for the MSs to measure the interfering cell signal level anymore. To keep the related interference data in these cases, the BSC freezes this data by locking the incoming interference BIM table entry in question. This prevents the particular interference relation from being terminated.

The interference relations are kept active. This ensures that the information flow regard-ing channel assignments and releases, power level, and neighbour cell updates keeps

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flowing in if the interfering cells are controlled by other BSCs. A locked BIM entry indi-cates a BCCH conflict or a conflict between two (BCCH, BSIC) pairs.

BCCH conflictA BCCH conflict exists if an interfering cell uses the same BCCH frequency as the serving cell. Therefore, this interfering cell cannot be measured by the MSs and it does not appear in the DFCA C/I statistics of the serving cell. Without an explicit locking pro-cedure, this could eventually lead to deletion of the BIM entry based on the BIM update guard time (BUGT) parameter. The locking procedure makes sure that a cell that was previously found interfering is taken into account even after the BCCH frequency has been changed to the same as in the serving cell.

The BSC identifies the BCCH frequency conflict immediately after the BCCH frequency of a DFCA cell is changed and informs the operator about the conflict with the 7765 DFCA NEIGHBOUR CELL CONFLICT alarm. Similarly, when the conflict is removed in a BCCH frequency change, the BSC automatically cancels the alarm, removes the locking, and resumes the normal BIM updates.

BCCH-BSIC conflictIn a BCCH-BSIC conflict, the BSC is not able to identify to which cell the BCCH-BSIC belongs. The BSC has found more than one candidate from its candidate cell table that are using the same BCCH-BSIC. In this case, the BSC raises the 7765 DFCA NEIGH-BOUR CELL CONFLICT alarm. This situation also occurs if the operator changes the BCCH-BSIC combination of one interfering cell to the same as that of another interfering cell. The BSC automatically detects this situation and informs the operator with the 7765 DFCA NEIGHBOUR CELL CONFLICT alarm. When the conflict is removed, the BSC cancels the alarm automatically.

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BSC-BSC interface


7 BSC-BSC interfaceIt is essential for the DFCA algorithm to know the channel usage situation of the cells that are interfering or being interfered by the cells of the local BSC. For the cells con-trolled by other BSCs, this is achieved with the use of a BSC-BSC interface. With the help of the BSC-BSC interface, DFCA can operate as transparently as possible across BSC area borders.

The BSC-BSC interface is used for the transmission of data that needs to be exchanged between DFCA algorithms in different BSCs when DFCA cells that are controlled by the different DFCA algorithms interfere with each other.

Data transfer on the inter BSC connection takes place within measurement relations that have been established between DFCA cells in different BSCs. The DFCA algorithm in a BSC establishes a measurement relation towards another DFCA algorithm in another BSC based on the results of the BIM update process.

When the BIM update process adds a significant interfering cell in the incoming interfer-ence BIM of the interfered cell and the interfering cell is controlled by another BSC, the local DFCA algorithm initiates a measurement relation by sending a request towards the BSC that controls the external interfering cell. Within this request, the initiating end indi-cates the DFCA cell that is the interfered part in the relation and the related level of inter-ference as a carrier-to-interference ratio (C/I) value. The DFCA cell is identified with a combination of the location area code (LAC), cell identity (CI), broadcast control channel (BCCH), and base station identity code (BSIC). If the interfering cell uses DFCA, the BSC that controls it accepts the measurement relation request and adds the interfered cell and the related C/I value as a new entry in the outgoing interference BIM table of the interfering cell in question.

When a measurement relation between two DFCA cells in different BSCs exists, the DFCA algorithm of each end updates its counterpart about every DFCA channel alloca-tion and release that takes place in a DFCA cell of the relation. The interfered end of the relation sends updates about changes in the C/I of the relation, as they take place as a result of the BIM update process. If the operator changes the information used for iden-tifying DFCA cells, this is updated to the other end of a measurement relation. In addi-tion, the DFCA connection-specific power control and neighbour cell C/I data is forwarded to the DFCA algorithm at the other end of the measurement relation as soon as it is received from the local power control and handover algorithm.

Figure 12 Channel assignment conflict

Although all channel allocation messages are sent immediately after a DFCA assign-ment over the BSC-BSC interface, there is some delay before the information reaches the radio resource table of the interfered cells in the target BSCs. Therefore, there is a possibility of a conflict between simultaneous DFCA channel assignments. To prevent a possible call drop in this situation, the BSC controls defined time that the same

BTS3BTS1 BTS2

CHANNEL_ASSIGNMENT(BTS 1, TSL=1, DFCA MA=1, MAIO=3

CHANNEL_ASSIGNMENT(BTS 3, TSL=1, DFCA MA=1, MAIO=3)

BSC BBSC A

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BSC-BSC interface

timeslot (TSL), DFCA mobile allocation (MA), and mobile allocation index offset (MAIO) combination is not allocated between the BIM neighbours in the local and remote BSC. The time is controlled with the BSC parameter expected BSC-BSC interface delay (EBID). In case of conflict, the BSC allocates a new channel for the request and the call procedure continues as usual.

There is also a separate procedure for collecting information on the data transmission delay in the BSC-BSC interface. The results of this procedure are available for the user in the counters of the BSC-BSC measurement. For more information, see 102 BSC-BSC Measurement under Reference.

Addressing in the BSC - BSC interfaceEvery BSC has been assigned an SCCP Signalling Point Code (SPC) during the creation of the A interface. One BSC can have up to 40 active SPC connections. The SPC is used to identify and address a BSC through the BSC-BSC interface. Internally the DFCA algorithm in a BSC must be able to identify each DFCA cell in the area uniquely. For more information, see DFCA cell identification process.

The DFCA algorithm finds out the BSC (SPC) that controls a particular external DFCA cell with a LAC-to-SPC mapping table. The LAC-to-SPC mapping table reduces the sig-nalling and processing load in the BSC-BSC interface by giving the BSC a limited set of neighbour BSCs, from where to search each DFCA cell that is not under its control.

The LAC-to-SPC mapping table is illustrated in table Example of LAC-to-SPC mapping. In the table, each LAC is mapped to 1-6 different SPCs. The operator has to fill in this table so that it contains the LACs used in the DFCA area and the BSCs (SPCs) that control one or more DFCA cells within each LAC.

LAC-to-SPC mapping info

Index LAC SPC

1 10011 10002

24

302

54

1202

923

2 10015 2032

254

0

0

0

0

Table 13 Example of LAC-to-SPC mapping

DN03282742 57


BSC-BSC interface


The DFCA information transferred in the BSC-BSC interface always concerns a partic-ular DFCA cell that is identified by a unique LAC-CI-BCCH-BSIC combination. When the BIM update process discovers a new interfering cell that is controlled by a remote BSC, the local BSC initiates a measurement relation towards the remote BSC. For that, the local BSC has to find out the SPC address of the remote BSC, based on the LAC of the interfering cell in question.

As the first thing, the BSC initiating a measurement relation checks the information related to existing measurement relations to see if, in another DFCA cell, there already is a measurement relation to the remote cell with this new cell. If an existing measure-ment relation is found, the related SPC is also found within the data saved for the rela-tion. The BSC sends a measurement relation initiation request with the found SPC.

If there is no earlier information about the newly discovered cell in the BSC, the BSC sends the measurement relation request to all SPCs found from the LAC-to-SPC table for the LAC.

Error cases

If a LAC is reported but the LAC is not listed in the LAC-to-SPC mapping table, the BSC raises a 3260 UNKNOWN POTENTIALLY INTERFERING CELL FOR DFCA distur-bance alarm.

If the LAC can be identified and the LAC is listed in the LAC-to-SPC mapping table but there are no SPCs defined for this LAC, the BSC assumes that there are no DFCA cells in this LAC and terminates the measurement relation initiation without any error indica-

3 10020 311

265

43

0

0

0

... ...

64 FFFEH 0

0

0

0

0

0

LAC-to-SPC mapping info

Table 13 Example of LAC-to-SPC mapping (Cont.)

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BSC-BSC interface

tion. The related entry in the incoming interference BIM table of the interfered cell is also removed.

DN03282742 59


Automatic configuration changes


8 Automatic configuration changesDynamic Frequency and Channel Allocation (DFCA) hopping requires that the network is working in a synchronised way. The synchronisation is implemented in each base control function (BCF) with a clock synchronisation signal from the location measure-ment unit (LMU). There can, however, be situations where the LMU clock synchronisa-tion is temporarily lost. In these situations, the BSC automatically switches between synchronised and unsynchronised operation in the BTSs that are controlled by the BCF that has lost its synchronisation. This means significant changes in DFCA operation.

Another requirement for efficient DFCA operation in a BTS is that there are no detected problems in connections to the neighbour BSCs that control DFCA cells that cause inter-ference to the BTS. If such connection failures take place during DFCA operation, it leads to the same recovery actions as when the synchronisation of a BTS is lost.

8.1 Loss of synchronisationThe synchronisation of the network is monitored with the Recovery for BSS and Site Synchronisation software that provides the synchronisation status information needed for DFCA purposes. If the LMU clock synchronisation is temporarily lost in a DFCA hopping BTS the DFCA TRXs of the BTS are set in the unsynchronised DFCA mode. This means random radio frequency hopping (RF hopping).

During the unsynchronised DFCA operation, the DFCA algorithm is suspended and the conventional channel allocation procedure is also used in the DFCA transceivers (TRXs). The unsynchronised mode DFCA mobile allocation (MA) list attached to this BTS is taken into use in the DFCA TRXs. The BSC determines the mobile allocation index offset (MAIO) values for DFCA TRXs, based on constant values MAIO offset = 0 and MAIO step = 2.

The hopping sequence number (HSN) to be used in the unsynchronised 'DFCA hopping' mode is defined with the formula (BCCH frequency MOD 63)+1. This guarantees that a different HSN is used in co-located BTS that may still be following the same clock. This also takes care of the HSN reuse distance corresponding to the broadcast control channel (BCCH) reuse distance.

When the BSC gets informed about the loss of synchronisation, it blocks the DFCA TRXs that are in the control of the BCF the synchronisation of which was lost. Prior to the blocking, the BSC applies the forced handover procedure to pre-empt the DFCA TRXs from traffic to avoid dropped calls. The BSC changes the DFCA TRXs to the unsynchronised random frequency hopping operation, performs the related reconfigu-ration actions, requests restart for the DFCA TRXs, and reopens them for use.

When the synchronisation status of a BTS changes back to synchronised, the normal DFCA mode of operation is restored for the DFCA TRXs.

8.2 Loss of inter-BSC connectionThe signalling connection control part (SCCP) of the BSC-BSC interface informs the connected BSC if the connection to another BSC breaks down. When a BSC-BSC con-nection break occurs, the SCCP raises the 2241 SCCP SUBSYSTEM PROHIBITED alarm for the BBI subsystem and the SPC in question. On receiving the information about the BSC-BSC connection failure, the BSC starts a 30-minute timer to control the BSC-BSC connection break. If the BSC-BSC interface is still not working after 30

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Automatic configuration changes

minutes, the BSC starts the actions to tolerate the uncontrolled interference that it may receive from the remote BSC. The BSC first determines the remote cells that are con-trolled by the BSC to which the connection was lost. Then the BSC checks the incoming interference BIM table of every local DFCA cell to see if any of the remote cells is included in the BIM and if the carrier-to-interference ratio (C/I) for any such remote cell is lower than 10 dB. If this is the case, the communication fault may cause excessive uncontrolled interference in the DFCA TRXs of the cell, because the DFCA algorithm operates without up-to-date knowledge on some of its interfering cells.

If an inter-BSC communication fault leads to uncontrolled interference in a DFCA BTS, the BSC raises the 3286 INTER BSC CONNECTION FAILURE DISTURBING DFCA OPERATION alarm for the SPC in question. The alarm informs the user of the DFCA BTSs and the DFCA TRXs that are affected by the failure. If during the inter-BSC com-munication failure radio conditions of a BTS change and lead to uncontrolled interfer-ence, the BSC raises the 7764 DFCA USE PREVENTED DUE ANOTHER BSC UNCONTROLLED INTERFERENCE alarm for the BTS in question. This alarm is a notice and, therefore, not cancelled.

When the BSC raises the 3286 or 7764 alarm for the BTS, the BSC temporarily blocks the DFCA TRXs that are affected by the failure. Before the blocking, the BSC applies the forced handover procedure to pre-empt the DFCA TRXs from traffic to avoid dropped calls. The BSC changes the DFCA TRXs to the unsynchronised random fre-quency hopping operation, performs the related reconfiguration actions, requests restarts for the DFCA TRXs, and reopens them for use.

When the interface fault ceases to exist, the BSC cancels the 3286 INTER BSC CON-NECTION FAILURE DISTURBING DFCA OPERATION alarm and reconfigures the DFCA TRXs back to the normal DFCA mode.

Short inter-BSC communication breaks may be allowed without immediate actions. The allowed break duration when the SCCP informs the BSC about the BSC-BSC connec-tion break and causes the 2241 alarm is adjusted using MML commands. The param-eter set corresponding to the signalling point code (SPC) can be found out with the NFI command. In the parameter set, the allowed break duration is SSP_FILTER_TIMER. The parameter sets are handled with the OC command group. The OCI command is used to print the parameter set and the OCM command to modify the parameter set.

When receiving the information on the return of the inter-BSC communication to a remote BSC, the BSC determines if there are cells where DFCA usage can be recov-ered because of the detected inter-BSC communication status change. The BSC cancels the 3286 INTER BSC CONNECTION FAILURE DISTURBING DFCA OPERA-TION alarm for the BTS and configures the BTS automatically back to the DFCA hopping operation.

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Dynamic Frequency and Channel Allocation manage-ment

Id:0900d805808d0272Confidential

9 Dynamic Frequency and Channel Allocation management

9.1 Defining DFCA MA listsThe operator arranges the available Dynamic Frequency and Channel Allocation (DFCA) frequencies into one or more DFCA mobile allocation (MA) lists. The DFCA MA lists are defined in each BSC where the MA list identification range from 1 to 64 is reserved for DFCA MA lists. It is recommended that a DFCA MA list contains 2, 3, 4 ,6, 8, 12, 13, 16, 17, 24, 26, 32 or 64 frequencies. For more information, see Frequency band management and frequency layering in chapter Planning Dynamic Frequency and Channel Allocation.

The DFCA MA lists have a specific state parameter that can have either of the two values: 'out of use' and 'in use'. When a new DFCA MA list is created, its initial state is always 'out of use'. A DFCA MA list can be attached to a BTS for the actual use only if the list is active, that is, the state of the list is 'in use'.

The maximum number of the DFCA MA lists is 64. It is recommended that all the lists have not been taken into use in the BSC because changing the DFCA frequencies of the DFCA hopping BTS(s) is recommended to be made so that the 'old' DFCA MA lists of the BTS(s) are replaced with the new DFCA MA lists. For more information on changing DFCA MA lists, see Changing DFCA frequencies during DFCA use.

Covering a geographical areaWhen defining the DFCA MA lists, which are used in the same geographical service area, the following rules should be followed:

• All 'in use' state DFCA MA lists will be defined to the same DFCA MA list group • Any DFCA frequency can only be used on one DFCA MA list which is in 'in use'

state. • If any two DFCA MA lists contain frequencies that are adjacent to each other, the

two DFCA MA lists are considered adjacent. Adjacent DFCA MA lists which are in 'in use' state must have the same length (that is, contain the same number of fre-quencies).

• In case the DFCA band includes adjacent frequencies, and multiple MA lists are used, the frequencies must be set in ascending order in every list (see figure Example of frequency band split in chapter Planning Dynamic Frequency and Channel Allocation).

• In adjacent BSCs (the service areas of which are adjacent to each other), DFCA MA lists must be defined in the same way so that DFCA MA lists and DFCA MA lists with identical ID numbers are identical in both BSCs.

Breaking the rules causes an inadequate carrier-to-interference ratio (C/I) estimation, and possibly, degradation in call quality during the DFCA use. This is why a minor per-formance degradation scenario might occur during the change of the DFCA frequency plan if the old plan has DFCA MA lists conflicting with those of the new plan. The deg-radation is not too significant if the frequency plan changes are implemented during a short period of time and with low traffic, typically during the night-time.

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Covering different geographical areasIf the geographical service areas are apart from each other, then the DFCA MA lists of areas can be defined to different DFCA MA list groups. The frequencies can be reused freely in DFCA MA lists, which are defined into different DFCA MA list groups. The DFCA controls the interference between co-channels and adjacent channels of DFCA MA lists that belong to same DFCA MA list group. The DFCA does not control the inter-ference between co-channels and adjacent channels that are using DFCA MA lists, which belong to different DFCA MA list groups. It is the operator's responsibility to take care of that in the radio network planning and the configuring phase.

If DFCA MA lists belongs to different DFCA MA list groups and they are used in sepa-rated geographical areas, then the following rules should be followed:

• The DFCA frequency can be used on several 'in use' state DFCA MA lists, which are defined to different DFCA MA list groups.

• If any two DFCA MA lists, which are defined to different DFCA MA list groups, contain frequencies that are adjacent to each other, then these 'in use' state DFCA MA lists' length can vary (that is, it can contain different number of frequencies).

• If DFCA MA lists which belong to different groups have adjacent frequencies and use multiple MA lists, then the frequencies must be set in ascending order in every list, which belongs to these groups.

This way, different sets of DFCA MA lists can be used in different locations that are apart from each other, as represented in figure Usage of DFCA MA groups in separate service areas in the BSS

Figure 13 Usage of DFCA MA groups in separate service areas in the BSS

Note that the DFCA does not control interference caused by co-channels and adjacent channels of the DFCA MA lists which belong to different DFCA MA list groups. You

BSC

DMAL DMAL DMAL DMAL DMAL

DMALDMAL DMAL

DMAL GroupARFCN

513

DMAL Group

ARFCN513

DN03282742 63




should take the interference control into account when planning and configuring the radio network.

9.2 Attaching DFCA MA lists to a BTSDFCA hopping operation in a BTS requires that the operator has attached one or more DFCA lists for the synchronised DFCA hopping operation. The operator can attach up to 64 DFCA MA lists to a BTS. The activity state of a DFCA MA list must be 'in use' when the lists are attached.

The BSC does not check the number of frequencies on the DFCA MA lists attached to a DFCA BTS and the number of DFCA transceivers (TRX) of the BTS. It is, therefore, possible to have a configuration where the number of DFCA TRXs exceeds the number of frequencies available for DFCA on the DFCA MA lists of the BTS. This does not prevent the operation of DFCA in the BTS. However, this can lead to a situation where the capacity of the DFCA TRXs in the BTS cannot be fully exploited because of the soft blocking that the DFCA algorithm runs into.

The BSC checks on the DFCA MA group level that the following conditions set for the frequencies in the active DFCA MA lists to be attached and the DFCA MA lists of the BTS are met:

• if the DFCA frequency can only be used on one DFCA MA list in the BTS • if any two DFCA MA lists of the BTS contain frequencies that are adjacent to each

other, the two DFCA MA lists are considered adjacent. Adjacent DFCA MA lists must have the same length (that is, contain the same number of frequencies).

If the conditions have been broken, the BSC prevents attaching DFCA MA lists to the BTS.

These rules are also valid for all ‘in use’ state DFCA MA lists that are or will be used in the same geographical area, even though they are not attached to the BTS. The operator should take care that the rules are not broken on the BSC level and between different BSCs belonging to the same geographical area. Breaking the rules causes an inadequate carrier-to-interference ratio (C/I) estimation, and possibly, degradation in call quality.

The DFCA hopping operation also requires that the operator has attached a separate MA list for the unsynchronised mode of DFCA operation. This list is a normal MA list (id 1…4200) defined in the BSC but includes frequencies of the DFCA band. This list is used in the DFCA TRXs with random radio frequency hopping (RF hopping) during the unsynchronised mode of operation. In the unsynchronised DFCA operation the BSC decides the values for the hopping sequence number (HSN) and mobile allocation index offset (MAIO) automatically. For more information, see Loss of synchronisation.

The DFCA MA list attachments for the synchronised operation and the DFCA unsyn-chronised mode MA list can be modified without locking the BTS in question if the value of the DFCA mode (DMOD) parameter of the BTS is 'off' or 'standby'. If the value of the DFCA mode (DMOD) parameter of the BTS is 'DFCA hopping', the modifying of the DFCA MA list attachments for both the synchronised and the unsynchronised operation requires locking the BTS or locking all the DFCA TRXs of the BTS.

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9.3 Defining DFCA TRXs of a BTSDFCA usage in a BTS is controlled TRX by TRX. The operator can define a TRX to be used for DFCA by modifying the TRX-level parameter DFCA indication (DFCA). The parameter can be modified without locking the object, if the value of the DFCA mode (DMOD) parameter of the BTS is 'off' or 'standby'. If the BTS is in the 'DFCA hopping' mode, the procedure requires TRX locking. Even though a TRX is defined as a DFCA TRX, it functions normally until the BTS is switched to 'DFCA hopping' mode.

9.4 Modifying the DFCA mode of a BTSDFCA is activated BTS by BTS using the BTS-level parameter DFCA mode (DMOD). The parameter has three values: 'off', 'standby', and 'DFCA hopping'. Initially, the value of the DFCA mode (DMOD) parameter of a BTS is 'off'. As you start to activate the DFCA, you first have to change the value of the DFCA mode (DMOD) parameter to 'standby'.

Switching DFCA mode from off to standbyThe DFCA 'standby' mode is an interim phase of the activation that is required before the actual DFCA operation. In the 'standby' mode, the DFCA C/I statistics collection with the background interference matrix (BIM) update process is started allowing the poten-tially interfering cells to be identified and saved in the BIM tables by the BSC. In addition, the interference measurement relations between the DFCA cells in different BSCs are established and the associated information updates between the cells are started. All this makes it possible to start the DFCA operation in the cell.

However, this requires that at least one BIM update period in the 'standby' mode has elapsed. Therefore, after changing the DFCA mode from 'off' to 'standby', it is recom-mended that you keep the BTS in the 'standby' state for the duration of at least one BIM update period, and then change the DFCA mode to 'DFCA hopping'. For more informa-tion on the BIM update period (BUP) parameter, see BSS Radio Network Param-eter Dictionary under Reference.

The BTS DFCA mode can be switched from 'off' to 'standby' without BTS locking, because the configuration or the operation of the BTS is not changed when this mode change is made. The BSC prevents switching the DFCA mode directly from 'off' to 'DFCA hopping'.

Switching DFCA mode from standby to offWhen this mode change takes place in a DFCA cell, the BSC deletes the BIM tables of the cell and the BIM entries related to this cell in other DFCA cells. The BSC cancels all the DFCA interference relations associated with this cell.

The BTS DFCA mode can be switched from 'standby' to 'off' without BTS locking.

Switching DFCA mode from standby to DFCA hoppingBefore the DFCA mode can be changed from 'standby' to 'DFCA hopping', the BTS must be locked. After the DFCA mode has been changed, the BTS must be unlocked for the changes and reconfigurations to take place. When this change takes place, the BSC checks that the necessary conditions of DFCA operation are fulfilled. The BSC ensures that

• synchronisation has been enabled with the location measurement unit (LMU) as the synchronisation source

DN03282742 65




• there are only traffic channel (TCH) or not-in-use channel (NOTUSED) timeslots in the DFCA TRXs

• there are no super reuse TRXs defined in the BTS • there are no DFCA TRXs where GPRS is enabled (if GPRS is enabled in the BTS) • there are no extended cell range TRXs in the BTS • Antenna Hopping is not used in the BTS • at least one DFCA MA list has been attached to the BTS • DFCA unsynchronised mode MA list has been defined for the BTS and DFCA

unsynchronised mode MA list length >= (2 * the number of unlocked DFCA TRXs of the BTS) -1

• broadcast control channel (BCCH) TRX's frequency is not defined for the DFCA MA list of the BTS

• baseband hopping is not used in the BTS

This change causes the DFCA TRXs in the BTS to be reconfigured to 'DFCA hopping' mode and the DFCA channel selection algorithm starts working on the channel assign-ments on the DFCA TRXs. The BSC also starts updating the DFCA radio resource (RR) table (both internally and externally) to the neighbour BSCs if there are remote DFCA cells listed in the BIM tables of the local DFCA cells.

The BSC allows the operator to switch a BTS to the 'DFCA hopping' mode even if the BTS is temporarily unsynchronised. If the synchronisation is enabled with the LMU as the synchronisation source but the BTS is temporarily out of synchronisation, the operator unlocks a DFCA BTS in the unsynchronised mode. The BSC automatically reconfigures the BTS to synchronised DFCA hopping operation once the synchronisa-tion from the LMU is available.

Switching DFCA mode from DFCA hopping to standbyBefore the DFCA mode can be changed from 'DFCA hopping' to 'standby', the BTS must be locked. After the DFCA mode has been changed, the BTS must be unlocked for the changes and reconfigurations to take place.

This change causes the DFCA TRXs in the BTS to be reconfigured to the normal oper-ation mode and the conventional channel allocation algorithm starts working on all the channel assignments in the BTS. The BSC also stops updating the DFCA RR table (both internally and externally).

The BIM updating process and maintenance of the BIM tables continues.

Switching DFCA mode from DFCA hopping to offBefore the DFCA mode can be changed from 'DFCA hopping' to 'off', the BTS must be locked. After the DFCA mode has been changed, the BTS must be unlocked for the changes and reconfigurations to take place.

This change causes the DFCA TRXs in the BTS to be reconfigured to the normal oper-ation mode. The conventional channel allocation algorithm starts working on all the channel assignments in the BTS. The BSC stops the DFCA RR table updates related to the modified cell. The BSC also stops the BIM update process and maintenance of the BIM tables for the cell in question. The BIM entries related to the modified cell in the BIM tables of other DFCA cells are deleted and the related interference relations are can-celled.

66 DN03282742




9.5 Changing DFCA frequencies during DFCA useYou can change the DFCA frequencies of the BTSs which use the same band according to the following instructions so that the service impact of the cell reconfiguration phase is minimized:

1. Configure the frequencies to the ‘new’ DFCA MA list(s) that is (are) in 'out of use' state. This is done in the preparation phase.

2. Set the ‘new’ DFCA MA list(s) to 'in use' state.3. Lock a DFCA hopping mode BTS, detach the old DFCA MA list from the BTS, attach

the ‘new’ DFCA MA list to the BTS, and unlock the BTS.4. Repeat the step 3 for all required DFCA hopping mode BTSs.5. Set the ‘old’ DFCA MA list(s) to 'out of use' state.

The BSC checks the adjacent frequency relations between the DFCA MA lists in 'in use' state only after the old list is set to 'out of use' state. If the old list is not set to 'out of use' state, the DFCA algorithm cannot identify the adjacent channel interference. This causes an inadequate carrier-to-interference ratio (C/I) estimation, and possibly, deg-radation in call quality.

9.6 RehomingIn rehoming an existing site is moved from a BSC to another. When moving the site, all parameters of the site are automatically transferred to the new BSC side. The BIM table makes an exception. It is not transferred to the new BSC. So, the BIM table of the site is empty in the new BSC side.

There are two ways to make rehoming for a DFCA site:

• If rehoming concerns just a few sites in the area, the DFCA can be directly set to DFCA hopping mode when the new site is unlocked. Then the BIM table is collected in DFCA hopping mode. During the first BIM collection period the site may have some performance degradation due to uncontrolled interference. However, due to a small number of new sites, the performance degradation is insignificant. As these kinds of changes are typically made in the night-time, the performance has already recovered by the morning, and is back to normal before the busy hours.

• If rehoming concerns several sites, it is recommended to set the DFCA to standby mode before the site is unlocked. The BIM tables are now collected in DFCA standby mode. One day is typically enough in standby mode, and the sites can be set to DFCA hopping mode, for example, the following night.

9.7 Optimising intra-cell handover parametersThe optimal functionality of intra-cell handovers is important for DFCA. During a call, the C/I situation in a cell can change, for example, because of the movement of the interfer-ing calls, so that a good channel that was initially allocated for the call can change to be a bad one. With optimal intra-cell handover parameter settings, good level of quality can be maintained by triggering an intra-cell handover back to a good channel if the quality deteriorates too much. In addition to normal intra-cell handover parameters, four UTPFIL parameters can be used to optimise intra-cell handovers caused by interference or AMR packing/unpacking.

DN03282742 67




• RCS_UNPACK_LEV_THR_PRM_C (parameter ID: 7E)This parameter is used to control handovers caused by AMR unpacking. If the average RxLevel is higher than the value of this parameter, handovers caused by AMR unpacking are not allowed.The value of this parameter can be between 1 and 63. If no value is given, the parameter is not in use.

• RCS_INTF_LEV_DFCA_PRM_C (parameter ID: 7F)This parameter is used to add a lowest priority interference handover to the priority list. This makes it possible to make the handover based on a high RxLevel and inter-ference as an intra-cell handover.This parameter is either on or off. Value 1 means that the parameter is in use. No value or value 0 means that the parameter is not in use. However, the value of this parameter has no effect unless also the RCS_INTF_LEV_DFCA_THR_PRM_C parameter is in use.

• RCS_INTF_LEV_DFCA_THR_PRM_C (parameter ID: 80)This parameter is used to control handovers caused by AMR unpacking and inter-ference based on RxLevel. If the average RxLevel is lower than the value of this parameter, handovers caused by AMR packing/unpacking or interference are not allowed.The value of this parameter can be between 1 and 63. If no value is given, the parameter is not in use.

• RCS_QUAL_LIMIT_DFCA_PRM_C (parameter ID: 81)This parameter is used to control handovers caused by AMR unpacking and inter-ference based on RxQuality. If the average RxQuality is worse than or equal to the value of this parameter, handovers caused by AMR packing/unpacking or interfer-ence are not allowed.The value of this parameter can be between 1 and 7. If no value is given, the param-eter is not in use.

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Id:0900d805808c1d93Confidential

Frame number and timeslot offsets

10 Frame number and timeslot offsets

10.1 Frame number offset for optimised BSIC decoding perfor-manceTo identify a neighbour cell, the mobile station (MS) has to decode the base station identity code (BSIC) transmission by receiving the frequency correction burst and the synchronisation burst during the idle frames. The frequency correction and the synchro-nisation bursts are sent on the broadcast control channel (BCCH) according to a pre-determined schedule, based on the time division multiple access (TDMA) frame numbers. An idle frame occurs once in every 26 TDMA frames for full rate (FR) connec-tions.

Decoding of the BSIC requires a coincidence of the idle frame and the frequency cor-rection and synchronisation burst transmissions. If the frame number offsets are not used, the BCCH multi frames are coincident in all the cells. This significantly decreases the possibility to decode the BSIC, as generally the decoding is possible only every 10 traffic channel (TCH) multi frames. With non-coincident BCCH multi frames, the BSIC decoding is possible more frequently.

The frame number offset (FNO) parameter is location measurement unit (LMU) specific. All the synchronised BTSs of a site and in the same clock distribution chain always have the same frame number (FN) offset. The planning of the FN offsets is, therefore, done on site basis. A simple optimised FN offset planning rule is presented in figure FN offset planning rule.

Figure 14 FN offset planning rule

The BSIC decoding speed improvement may not be very critical, and perfectly accept-able results may also be achieved with simpler planning rules (for example, FN offset = BCF ID, as long as the FN offset varies from site to site).

Another parameter, FNO 26-multiplier Usage controls enabling and disabling of 26 multiplier for frame number offset. Frame Number Offset (FNO) parameter changes synchronisation in 26 frame steps, if FNO 26-multiplier Usage parameter is enabled.

+4+4 +4

+4 +4 +4 +4

+4 +4 +4

+1+1

+1+1 +1

+1+1 +1

+1+1

14 18 20

13 17 21

12 16

MS

DN03282742 69




This causes overlapping of SACCHs, there by degrading SACCH performance by 2-3dB in synchronised networks. The parameter values are ‘in use’ and ‘not in use’. When ‘FNO 26-multiplier Usage’ parameter is ‘not_in_use’, the synchronisation does not follow the 26 period and the interference cannot be separated with the half TSL accu-racy.

10.2 Timeslot offset for better FR SACCH performanceTo support half rate (HR) channels with DFCA, the frame number offsets (FNO) used by the system must be multiples of 26. To implement this, the FNO 26-multiplier Usage parameter is enabled by the operator.

The actual frame number offset being a multiple of 26 leads to a situation where the slow associated control channel (SACCH) frames are transmitted simultaneously throughout the network. As the SACCH bursts are always transmitted independently of discontinuous transmission (DTX), the SACCH does not benefit from the DTX gain at all. In an asynchronous network, the SACCH benefits from the DTX, as in most cases the SACCH is interfered by TCHs that use the DTX.

In case of adaptive multi-rate (AMR) full rate (FR), the carrier-to-interference ratio (C/I) of the channel can be very low, as TCH is very robust. Low C/I condition, together with the lack of DTX gain, can cause very poor SACCH performance. This leads to lost measurement reports and power control commands, and ultimately to degradation in TCH/FR performance.

Solution for full rateThe AMR FR capacity degradation can be avoided using the lmu tsl fn offset (LTO) parameter. This parameter is defined in the BSC for each LMU. The available value range of the parameter is from 0 to 7, but with DFCA only values 0 and 1 are rea-sonable.

Note that you must not give values other than 0 or 1 for the parameter. The BSC does not prevent you from giving illogical values for the parameter with DFCA.

When a different value of timeslot TSL offset is used in every other cell, the coincident SACCH traffic decreases by 50%. The FN for the sending of FR SACCH frame depends on the TSL number. The frame number is different for even and odd TSLs. When SACCH frames for the even TSLs are sent, the frame for the odd ones is idle. The SACCH is sent for TSLs 0, 2, 4, and 6 when FNO 26-multiplier Usage parameter is used. The SACCH is sent for TSLs 1, 3, 5, and 7 when FNO 26-multiplier Usage parameter is used.

Effects of the FN de-alignment to half rateThe FN de-alignment for FR channels causes exceptions in HR sub-channel alignment. If the value of the lmu tsl fn offset (LTO) parameter is set to 1, the TSLs are sent one TSL later than in a cell with the parameter value 0. With HR, every other frame is either for the subchannel 0 or for the subchannel 1. TSLs 1-7 with the parameter value of 0 and TSLs 0-6 with the parameter value of 1 have the same frame number, but TSL 0 with the parameter value of 0 and TSL 7 with the parameter value of 1 have different frame numbers.

If HR is in use in the BTS, the BSC prefers FR allocation to the de-aligned TSL. If the value of the lmu tsl fn offset (LTO) parameter is 0, the de-aligned TSL is TSL 0. If the parameter value is 1, the de-aligned TSL is 7.

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The parameter,lmu fn tsl delay defines how many symbol periods (a symbol period: ~3.69 microseconds) time slot offset for the FN phasing is delayed.

10.3 Flexible Frame number offsetThe feature BSS101562 “Flexible Frame number offset Management” makes possible DFCA usage without the frame number offsets (FNO) multiplier 26. When the feature is activated, the system uses the formula n x 1 to define the frame number offset.

g This feature is supported only by LMUB.

The BSC supports both full rate (FR) and half rate (HR) channels with the feature.

As the FNO does not need to be multiplier of 26, both the FR and HR can benefit gains of the DTX. The DTX gain is about 50%, depending on the call activity. In addition to that, additional gain comes from interference diversity. Without the feature Flexible Frame number offset, the HR channels interfered just own HR sub channel, that is HR


BSC S14 EP5.1 or newer

Flexi EDGE BTS EP2.0 for disabling the FNO 26-multiplier usage

EX4.1 MP1 support for LMU FN Time Slot Delay parameter

Flexi Multiradio BTS EX3.1 support for disabling the FNO 26-multiplier usage

EX4.1 MP1 support for LMU FN Time Slot Delay parameter

UltraSite EDGE BTS CXM8.1 MP1 support for LMU FN Time Slot Delay parameter

CXM4.1 support for disabling the FNO 26-multiplier usage

MetroSite EDGE BTS CXM4.1 support for disabling the FNO 26-multiplier usage

CXM8.1 MP1 support for LMU FN Time Slot Delay parameter

Talk-family BTS Not supported

MSC/HLR No requirements


NetAct OSS5.3 CD2(support for LMU area param-eters: FNO 26-multiplier usage & FNO 26-multiplier usage )

LMU, LMU Manager Not supported

LMUB, LMU Manager 1.0,CD7

Table 14 Required software for the feature Flexible Frame number offset

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sub1 interfered HR sub 1, but when the frame number offset is not multiples of 26, inter-ference source changes from HR sub channel to another sub channel in every SACCH period. This gives robustness against uncontrolled HR interference, for example outside of BIM, as interference of one HR channel cannot cause dropped call for another con-nection alone; a dropped call needs interference from both the half rate sub channels.

When DFCA is used for half rate channels or mixed half rate and full rate channels, it is recommended to use the Flexible Frame number offset, instead of Timeslot offset to optimize SACCH performance. With the feature dropped call rate can be significantly improved when half rate channels are used.

In FNO planning needs to be taken into account so that FNO optimizes also SACCH per-formance in addition of BSIC. The TSL offset does not give any extra gains for FR when Flexible Frame number offset Management feature is used. In the BSIC planning optimal plan can be done by avoiding multiplies of 10 for two neighbouring cells for BSIC decoding and also by avoiding multiplies of 26 between the cell and an interfering neigh-boring cell for optimal SACCH performance.

Frame Number offsets (FNO) multiplier 26 is disabled by using ‘FNO 26-multiplier Usage’ parameter.

For detailed steps on activation of the feature please refer the document Activating and Testing BSS11052: Dynamic Frequency and Channel Allocation.

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Planning Dynamic Frequency and Channel Allocation

11 Planning Dynamic Frequency and Channel AllocationThis section describes the issues related to radio network planning and configuration that you should consider before implementing Dynamic Frequency and Channel Alloca-tion (DFCA).

Note that DFCA is meant to be deployed over a large and continuous area, not only in a few cells. If the DFCA area remains relatively small, the DFCA cells face uncontrolled interference from the surrounding non-DFCA network. This may reduce performance gains.

BSS SynchronisationThe connection level C/I control requires that the BTSs using DFCA and the radio timeslots in them operate in synchronisation with each other. The timeslot (TSL) level of synchronisation for the DFCA BTSs allows the BSC to get precise knowledge of the interference sources when a new channel assignment is to be performed.

The basic TSL level synchronisation is provided by BSS Synchronisation. This is enhanced further by Recovery for BSS and Site Synchronisation or BSS Synchronisa-tion Recovery Improvement that enables automatic recovery actions to ensure satisfac-tory operation of DFCA transceivers (TRX) even when a BTS has lost synchronisation.

BSS synchronisation is provided by a location measurement unit (LMU) that is installed in the BTS site. The LMU provides synchronised clock signal that is distributed to all BTS cabinets. The LMU derives the synchronised clock signal from a global posi-tioning system (GPS) time reference.

Since BSS Synchronisation is a prerequisite for DFCA it must be implemented first. Regarding radio network parameter settings, BTS-site-specific frame number offset (FNO), FNO 26-multiplier Usage, lmu fn tsl delay, and LMU tsl fn offset (LTO) parameters need to be planned and set for the location mea-surement units (LMUs). For more information, see Frame number and timeslot offsets and BSS Synchronisation under Feature Descriptions.

Frequency band management and frequency layeringTo enable DFCA to control interference between cells, the frequency band needs to be split into two parts for DFCA roll-out: the DFCA layer and the regular layer. TRXs on the DFCA layer use only frequencies that are defined by DFCA mobile allocation (MA) lists.

The regular layer consists of broadcast control channel (BCCH) frequencies that are planned as usual. Additionally if feature SDCCH and PS Data Channels on DFCA TRX is not used, another non-DFCA SDCCH channel TRX may be needed in a cell for more signalling or GPRS/EDGE capacity. This kind of a TRX is also regarded as a regular layer TRX.

DFCA layer

DFCA requires separate frequencies that are reserved for DFCA use only. These fre-quencies should not be used in any regular TRX within the area in which DFCA is used. This ensures that DFCA is in full control of the usage of DFCA frequencies and can, therefore, effectively control the interference. The usage of DFCA frequencies for regular TRXs may cause some local DFCA performance degradation because of uncon-trolled interference.

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The DFCA frequencies are further divided into one or more MA lists. A DFCA MA list can contain 1-64 frequencies, and a maximum of 64 different DFCA MA lists is allowed. The DFCA MA lists are defined in each BSC where MA list identification number range 1–64 is reserved for DFCA MA lists.

In addition to the requirement of dedicated frequencies for DFCA, there are also other rules that have to be followed when defining DFCA MA lists:

• Any DFCA frequency can only be used on one DFCA MA list. • If any two DFCA MA lists contain frequencies that are adjacent to each other, the

two DFCA MA lists are considered as adjacent. Adjacent DFCA MA lists must have the same length (that is, contain the same number of frequencies).

• In the case that the DFCA band includes adjacent frequencies, and multiple MA lists are used, the frequencies must be set in ascending order in every list (see figure Example of frequency band split).

• DFCA MA lists in adjacent BSCs (BSCs the service areas of which are adjacent to each other) must be defined in the same way so that DFCA MA lists with identical ID numbers are identical in both BSCs.

Note that some mobile phone models do not work correctly when the hyperframe ends. Due to this problem, the length of the MA list has to be defined so that the hopping sequence continues without any extra frequency hops when the hyperframe ends. The frame number begins from zero. To avoid extra dropped calls due to the problem, the DFCA MA list has to include either 2, 3, 4, 6, 8, 12, 13,16,17, 24, 26, 32 or 64 frequen-cies.

Note that DFCA MA list group ID parameter can be used to make frequency plan more freely. BSC handles DFCA MA lists independently in different MA groups. It is the operator's responsibility to define those DFCA MA lists that are not interfering with each other.

In the following cases, it is recommended or required to use DFCA MA list group to separate DFCA MA lists:

• When a BSC covers more than one geographical areas (cities) and different fre-quency plans are needed for those areas, DFCA MA lists has to be separated with different DFCA MA list group ID parameter value.

• The number of hopping frequencies that can be used for DFCA is not divisible with the DFCA MA list size. For example, if there are 20 frequencies available for DFCA .Then the DFCA MA lists that includes adjacent frequencies has to be of equal length. This leads to a sit-uation where all the frequencies cannot be used due to limitations in MA lists length. In this case frequencies can be divided for example, 8 + 8 + 4 frequencies in a dif-ferent DFCA MA group. This kind of frequency plan may give better performance, though there is one adjacent channel suffering with non-controlled interference, when compared to fully interference controlled 8+8+3 frequency case.

Separate cell allocation lists for regular and DFCA resources

As any of the several DFCA mobile allocation (MA) lists attached to a BTS may be used for DFCA hopping in the BTS, the respective cell allocation (CA) frequency list must include all the frequencies that appear in any of the DFCA MA lists attached to the BTS. Separate CA lists are used for the DFCA TRXs and regular TRXs.

The DFCA CA list contains only the DFCA band frequencies that are used in the DFCA TRXs of the BTS, that is, the frequencies on the attached DFCA MA lists. The regular

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TRXs of the BTS are provided with the CA list that includes the frequencies used in fre-quency hopping in the regular layer of the cell and the frequencies attached to the unsynchronised mode DFCA MA list.

When the operator defines the frequencies for the DFCA MA lists, the restrictions con-cerning the DFCA cell allocation frequencies and radio interface messages of the GSM1800/GSM1900 system have to be taken into account. The following allocation coding methods can be used:

• range 512This allows the encoding of 2-18 frequencies, the frequencies being spread among up to 512 consecutive absolute radio frequency numbers (ARFCNs).

• range 256This allows the encoding of 2-22 frequencies, the frequencies being spread among up to 256 consecutive ARFCNs.

• range 1024This allows the encoding of 2-16 frequencies (17 if frequency 0 is included), the fre-quencies being spread among up to 1024 consecutive ARFCNs.

• variable bit mapThis allows any combination among 112 consecutive ARFCNs.

An example of DFCA MA list's definition is shown in figure Example of frequency band split.

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Figure 15 Example of frequency band split

Regular layer

The accuracy of the BCCH signal level measurements directly impacts the carrier-to-interference ratio (C/I) estimation accuracy and, therefore, DFCA performance. It is recommended to use dedicated BCCH frequencies, ensuring that non-BCCH interfer-ence does not cause errors in the measured BCCH signal levels. Using dedicated BCCH frequencies also leads to shorter BCCH frequency lists, which makes it possible for the mobile stations (MSs) to measure more signal level samples for each BCCH fre-quency and to decode the base station identity codes (BSICs) faster. All this helps in estimating the DFCA C/I accuracy.

Frequencies of the DFCA layer and frequencies of the regular layer should not be mixed. If they are, uncontrolled interference is caused and the advantage gained from DFCA decreases.

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Channel configuration of a cellYou need to decide which TRXs of a cell are DFCA TRXs. Usually there is only one regular TRX (BCCH) and the rest are used by DFCA.

Because DFCA cannot handle packet-switched (PS) traffic or signalling channels, the GPRS/EDGE territory and SDCCH capacity must be placed on the regular layer TRXs.

For more information, see System Impact of Dynamic Frequency and Channel Alloca-tion.

High capacity of the BSC configurationIn the Flexi BSC, the number of the DFCA cells must not exceed 1000 cells. The maximum numbers of TRXs are not limited.

BCCH and BSIC planningBCCH and base station identity code (BSIC) planning must ensure that the same BCCH and BSIC combination is not reused too tight. Normally, there is only a limitation that adjacent handover neighbours cannot have the same identifier.

For DFCA, this rule is not enough. As the MS only reports the BCCH and BSIC combi-nation that it can listen, the BSC has to map this combination into the right cell. If there are several cells that have the same identifier in the area, the BSC may map the identi-fier into a wrong cell. This wrong mapping may cause the DFCA algorithm to malfunc-tion.

The BSC uses handover adjacent definitions and background interference matrix (BIM) neighbour's (interfering or interfered DFCA cell) adjacent definitions for this mapping. If the BSC cannot find the cell identification for the BCCH and BSIC combination from its own neighbour cell definitions, it uses the BIM candidate table to find out the BCCH and BSIC combination. The BIM candidate table is built using the incoming and outgoing BIM tables of the own cell's BIM neighbours. Therefore, a BCCH and BSIC combination has to be unique in the area of a cell's BIM neighbours and their BIM neighbours.

For more information, see DFCA cell identification process.

BA list planningInterference estimation of DFCA is highly dependent on the RX level measurements reported by MSs. Therefore it is important that the MSs measure and report all the BCCH signals they receive, and not only those defined as handover neighbours. This is achieved by using BCCH allocation (BA) lists that contain all the possible BCCH fre-quencies and setting the BA lists to be used in active mode.

For more information, see BCCH frequency list.

Other parametrisation aspectsThe following aspects of traditional handover control and power control should be care-fully considered. This is because DFCA requires appropriate settings for handover and power control for best performance.

• Intra-cell handover should be in use. • Power control should be fast enough.

The power control interval of one second, for example, is suitable. • The RX level and RX quality handover thresholds should be considered.

Because DFCA improves connection quality, the cell size tends to expand. This means that the MS may move beyond the optimal handover position before a

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handover to another cell takes place. Therefore, pay attention to handover thresh-olds regarding the RX level and RX quality.

Interaction with other featuresCheck that there are no incompatible features in use in the DFCA cells or in the DFCA TRXs. For more information, see System Impact of Dynamic Frequency and Channel Allocation.

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Implementing Dynamic Frequency and Channel Alloca-tion overview

12 Implementing Dynamic Frequency and Channel Allocation overviewSteps

1 Plan the frequency band division and parameters.For details, see chapter Planning Dynamic Frequency and Channel Allocation.

You must also consider whether the values of the handover control or power control parameters require changing. If they do, you should implement the changes before acti-vating DFCA.

2 Implement BSS synchronisation.For details, see BSS Synchronisation under Feature Descriptions.

3 Install, configure, and activate the BSC-BSC interface.For details, see Connecting and Testing the BSC-BSC Interface under Integrate and Configure.

4 Activate DFCA.For details, see Activating and Testing BSS11052: Dynamic Frequency and Channel Allocation under Activate.

Documents

DFCA