DTM Overview

7/30/2019 DTM Overview

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Nokia Siemens Networks

GSM/EDGE BSS, rel.

RG20(BSS), operatingdocumentation, issue 01

Feature description

BSS20088: Dual Transfer Mode

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The information in this document is subject to change without notice and describes only the

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Copyright © Nokia Siemens Networks 2010. All rights reserved

f Important Notice on Product SafetyElevated voltages are inevitably present at specific points in this electrical equipment.

Some of the parts may also have elevated operating temperatures.

Non-observance of these conditions and the safety instructions can result in personal

injury or in property damage.

Therefore, only trained and qualified personnel may install and maintain the system.

The system complies with the standard EN 60950 / IEC 60950. All equipment connected

has to comply with the applicable safety standards.

The same text in German:

Wichtiger Hinweis zur Produktsicherheit

In elektrischen Anlagen stehen zwangsläufig bestimmte Teile der Geräte unter Span-

nung. Einige Teile können auch eine hohe Betriebstemperatur aufweisen.

Eine Nichtbeachtung dieser Situation und der Warnungshinweise kann zu Körperverlet-

zungen und Sachschäden führen.

Deshalb wird vorausgesetzt, dass nur geschultes und qualifiziertes Personal die

Anlagen installiert und wartet.

Das System entspricht den Anforderungen der EN 60950 / IEC 60950. Angeschlossene

Geräte müssen die zutreffenden Sicherheitsbestimmungen erfüllen.



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Table of ContentsThis document has 50 pages.

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

1 Overview of Dual Transfer Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2 System impact of Dual Transfer Mode. . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.2 Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.3 Impact on transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.4 Impact on BSS performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.5 User interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.5.1 BSC MMI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.5.2 BTS MMI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.5.3 BSC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.5.4 Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.5.5 Measurements and counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.6 Impact on Network Switching Subsystem (NSS). . . . . . . . . . . . . . . . . . 21

2.7 Impact on NetAct products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.8 Impact on interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2.9 Impact on mobile stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.10 Impact on capacity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.11 Impact on coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.12 Impact on planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2.13 Interworking with other features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3 IMSI co-ordination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4 Paging coordination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

5 GTTP signalling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

6 Radio resource management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

6.1 DTM allocation for PS connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

6.2 DTM multislot classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

6.3 Fragmentation of the PS resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

6.4 Territory management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

7 Dual Transfer Mode call establishment . . . . . . . . . . . . . . . . . . . . . . . . . 39

7.1 Mobile-originated call establishment . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

7.2 Mobile-terminated call establishment. . . . . . . . . . . . . . . . . . . . . . . . . . . 40

8 Handover control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

8.1 Intra-cell handover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

8.2 Inter-cell handover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

8.3 External handover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

8.4 Inter-system handover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

9 Dual Transfer Mode call release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

10 Implementing Dual Transfer Mode overview . . . . . . . . . . . . . . . . . . . . . 50



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List of FiguresFigure 1 E-mail in dual transfer mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 2 Real time video sharing in dual transfer mode . . . . . . . . . . . . . . . . . . . . . 9

Figure 3 DTM state transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 4 Paging coordination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Figure 5 PS paging procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Figure 6 GTTP signalling procedure in uplink. . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Figure 7 GTTP signalling procedure in downlink . . . . . . . . . . . . . . . . . . . . . . . . . 34

Figure 8 DTM multislot allocations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 9 DTM allocation example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 10 MO call establishment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Figure 11 MT DTM call establishment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41



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List of TablesTable 1 Required additional and alternative hardware or firmware . . . . . . . . . . 13

Table 2 Required software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Table 3 Impact of DTM on BSC units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Table 4 Counters of Traffic Measurement related to DTM . . . . . . . . . . . . . . . . . 16

Table 5 Counters of Handover Measurement related to DTM . . . . . . . . . . . . . . 16

Table 6 Counters of BSC Level Clear Code Measurement related to DTM . . . 17

Table 7 Counters of BSC Level Clear Code (PM) Measurement related to DTM .

17

Table 8 Counters of MS Capability Indication Measurement related to DTM . . 18

Table 9 Counters of Packet Control Unit Measurement related to DTM . . . . . . 18

Table 10 Counters of Coding Scheme Measurement related to DTM . . . . . . . . . 18

Table 11 Counters of Enhanced Quality of Service Measurement related to DTM .

18

Table 12 Counters of PS DTM Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Table 13 Counters of 106 CS DTM Measurement . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 14 Multi-slot power reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25



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BSS20088: Dual Transfer Mode Summary of changes

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Summary of changesChanges between document issues are cumulative. Therefore, the latest document

issue contains all changes made to previous issues.

Changes made between issues 3-1 and 3-0

Information on InSite BTS has been removed.


The BSS number has been added to the heading of the document.

Information on InSite BTS has been removed.


The list of Adjacent GSM (ADJC) radio network object parameters in BSC Parameters

has been updated.

Coverage planning in section Impact on planning and Network-Controlled Cell Re-selec-

tion in section Interworking with other features have been updated.

Power budget handover during a DTM call in section Inter-cell handover has been

updated.


Chapters System impact of Dual Transfer Mode and Implementing Dual Transfer Mode

overview have been added to this document.

Chapters Technical Description of Dual Transfer Mode, Requirements for Dual Transfer

Mode, Effect of Dual Transfer Mode on interfaces, and User Interface of Dual Transfer

Mode have been removed. The information has been moved to chapters Overview of

Dual Transfer Mode and System impact of Dual Transfer Mode.

Information on PrimeSite BTSs and 2nd generation BTSs has been removed.

Extended Cell for GPRS/EDGE, and TRAU Bicasting in AMR FR/HR Handover have

been added to chapter System impact of Dual Transfer Mode.

Section GMM/SM signalling in chapter System Impact of Dual Transfer Mode has been

updated for S13.

Information concerning Old BSS to New BSS information element has been added to

chapter Handover , section External Handover . It explains implementing of Dual Transfer

Mode.



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Overview of Dual Transfer Mode

1 Overview of Dual Transfer ModeDual Transfer Mode (DTM) provides mobile users with simultaneous circuit-switched

(CS) voice and packet-switched (PS) data services. This means that users can, for

example, send and receive e-mail during an ongoing phone call. Figure E-mail in dual

transfer mode illustrates how the user A can have a voice call while downloading e-mail

messages.

Figure 1 E-mail in dual transfer mode

Figure Real time video sharing in dual transfer mode illustrates how two DTM users

share a video call.

CS voice call

PS stream

BTS

Packet core

BTS

DTMuser 3

non-DTM MS

BSC/PCU

MSC/HLR

BSC/PCU

Mail server

IP backbone



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BSS20088: Dual Transfer Mode Overview of Dual Transfer Mode

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Figure 2 Real time video sharing in dual transfer mode

In dual transfer mode, the mobile station (MS) is simultaneously in dedicated mode and

in packet transfer mode so that the timeslots allocated for each MS are consecutive and

within the same frequency. In dedicated mode, the MS has a CS connection. In packet

transfer mode, the MS has a PS connection. The CS connection is always a single slot

connection, whereas the PS connection can also be a multislot connection.

The BSC supports only full rate CS connections in dual transfer mode. Simultaneously

obtained packet data rates can be up to 118 kbit/s for EGPRS and 40 kbit/s for

GPRS/CS-4.

Both the CS and PS parts of a DTM call are maintained in the PS territory. A DTM call

starts from an existing CS connection in the CS territory. During the DTM call establish-

ment, the CS connection is handed over to the PS territory and combined with the

related PS resources.

Dual Transfer Mode uses a native split between the circuit-switched (CS) and packet-

switched (PS) parts of the BSC for radio resource management.

The CS connection control in the BSC (CS connection control) handles the following:

User A

DTM MS

User B

DTM MS

BTS

BTS

BSC

BSC

MSC/HLR

GGSN

SGSN

SGSN

IMS

IP

backbone

CS voice call

PS stream



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• speech codec mode selection for the DTM CS connection

• handover control

The packet control unit (PCU) handles the following:

• admission control in the PS territory

• channel allocation for both CS and PS connections

• PS territory management

An MS is in dual transfer mode when it has simultaneous CS and PS connections. It can

enter dual transfer mode only through dedicated mode. If the MS is in idle mode, it

moves to dedicated mode before entering dual transfer mode. If the MS is in packet

transfer mode, the PS connection is released before the MS moves to dedicated mode.

The PCU or the MS re-establishes the PS connection as soon as the MS has a CS con-

nection.

If a CS connection is released when the MS is in dual transfer mode, also the PS con-

nection is released. The PCU or the MS re-establishes the PS connection as soon asthe CS channel release has been completed. If a PS connection is released when the

MS is in dual transfer mode, the MS returns to dedicated mode. The MS returns to idle

mode when it has neither a CS nor a PS connection. Figure DTM state transitions illus-

trates how an MS can move from one mode to another.

Figure 3 DTM state transitions

In the Nokia Siemens Networks implementation, the PCU is a part of the BSC. Termi-

nology is used in the following way:

• The BSC refers to the entire network element. The term is also used when it is not

necessary to distinguish between the CS and PS functionality.

• The PCU refers to the unit that manages PS connections.

RR idle mode/Packet idle mode

Packet transfer mode

Dedicatedmode

Dual transfer mode

PS release

CS release

DTM assignment



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BSS20088: Dual Transfer Mode Overview of Dual Transfer Mode

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• The CS connection control in the BSC (CS connection control) refers to software

that manages CS connections.

Benefits of Dual Transfer Mode

Mobile users require new services. With DTM, you can expand your service portfolio to

offer users enhanced services in a GSM/EDGE network. DTM allows you to provide a

wide range of services that demand a simultaneous CS and PS connection. Mobile

users can use data services, such as file transfer, web browsing, video sharing, and

mobile netmeeting, during a speech call. This makes it possible to launch services

similar to UMTS class A services also in 2G networks. In addition, these services can

be used to complement the 3G coverage in places where there is no 3G network cover-

age.

Compliance

DTM complies with the 3GPP standard (Rel5).

For more information, see section 3GPP 43.055 Dual Transfer Mode in Base Station

SubSystem BSS13, Compliance to 3GPP Rel-6 Specifications of TSG-Geran #33 (Feb-

ruary 2007). The document is available on request via NSN Product Management.

Related topics in Dual Transfer Mode

• System impact of Dual Transfer Mode

• IMSI co-ordination

• Paging co-ordination

• GTTP signalling

• Radio resource management

• Dual Transfer Mode call establishment

• Handover control

• Dual Transfer Mode call release

• Implementing Dual Transfer Mode overview

Other related topics

• RF Power Control and Handover Algorithm

• BSC3100: Radio Network Supervision in BSC

• BSS10016 and BSS10118: Common BCCH Control in BSC

• BSS8032: Direct Access to Desired Layer/Band

• BSS5050, BSS10118, BSS11116 and BSS8085: Dual Band Network Operation

• BSS10004 and BSS6071: Enhanced Speech Codecs: AMR and EFR• BSS10101 and BSS11107: GSM-WCDMA Interworking

• BSS115173: Soft Channel Capacity in BSC

• BSS9006: GPRS System Feature Description

• BSS10091: EDGE System Feature Description

• BSS20089: Extended Dynamic Allocation

• BSS115006: Network-Assisted Cell Change

• BSS11112: Network-Controlled Cell Re-selection

• BSC4015: Extended Cell

• BSS10046: Multi BCF Control in BSC

• Activating and Testing BSS20088: Dual Transfer Mode

• Activating and Testing BSS10083: EGPRS

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• Activating and Testing BSS9006: GPRS

• EA - Adjacent Cell Handling

• EE - Base Station Controller Parameter Handling in BSC

• EQ - Base Transceiver Station Handling in BSC • ER - Transceiver Handling

• TP - GSM Measurement Handling

• WO - Parameter Handling

• 1 Traffic Measurement

• 4 Handover Measurement

• 50 BSC Level Clear Code Measurement

• 51 BSC Level Clear Code (PM) Measurement

• 71 MS Capability Indication Measurement

• 106 CS DTM Measurement

• 72 Packet Control Unit Measurement

• 79 Coding Scheme Measurement

• 97 Enhanced Quality of Service Measurement

• 105 PS DTM Measurement

• BSS Radio Network Parameter Dictionary

• PRFILE and FIFILE Parameter List









































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BSS20088: Dual Transfer Mode System impact of Dual Transfer Mode

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2 System impact of Dual Transfer ModeThe system impact of BSS20088: Dual Transfer Mode (DTM) is specified in the sections

below.

DTM is an application software product and requires a valid licence in the BSC.

2.1 Requirements

Hardware requirements

Software requirements

Frequency band support

The BSC supports DTM on the following frequency bands:

• GSM 800

• GSM 900

• GSM 1800

• GSM 1900

Other requirements

GPRS/EDGE must be available and active in the network.

A Nokia Siemens Networks BSC needs the Gs interface for full paging coordination

support.

Network element Hardware/firmware required

BSC BSC2i or BSC3i

PCU2

BTS No requirements

TCSM No requirements

SGSN No requirements

Table 1 Required additional and alternative hardware or firmware

Network element Software release required

BSC S12 or later

Flexi EDGE BTS No requirements

UltraSite EDGE BTS No requirements

MetroSite EDGE BTS No requirements

Talk-family BTS No requirements

MSC/HLR M11

SGSN SG5

NetAct OSS4.1

Table 2 Required software

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System impact of Dual Transfer Mode

The network must support Network Operation Mode I (NOM I) to provide CS paging

coordination for DTM-capable MSS. In NOM I, the core network provides CS paging

coordination so that CS paging requests to GPRS-attached MSS are sent to the PCU

via the SGSN. The PCU provides CS paging on the packet associated control

channel (PACCH) if the MS is in packet transfer mode. If the MS is in packet idle mode,

it is paged for CS calls on the paging channel (PCH).

In Network Operation Mode II (NOM II), all CS paging requests are sent on the PCH.

This means that if a DTM-capable MS is in packet transfer mode (that is, there is

ongoing data transfer in normal GPRS/EDGE mode), it does not necessarily monitor the

PCH channel and, therefore, does not respond to the CS paging.

2.2 Restrictions

The following restrictions apply to DTM:

• DTM is not supported in the extended area of the cell. DTM is only supported in thenormal area of the cell.

The BSC does not perform coordination of international mobile subscriber

identity (IMSI) for those DTM-capable MSS that are in the extended area of the cell.

This prevents mobile-terminated (MT) DTM call establishment and GPRS transpar-

ent transport protocol (GTTP) signalling in the downlink direction.

• The single-slot operation mode of dual transfer mode is not supported. Only the

multi-slot operation mode is supported.

• CS paging coordination is not provided in Network Operation Mode II (NOM II). CS

paging coordination is provided in NOM I only.

For details on the NOM requirements, see section Other requirements.

•The BSC supports only full rate CS connections in dual transfer mode.

2.3 Impact on transmission

No impact.

2.4 Impact on BSS performance

OMU signalling

No impact.

TRX signallingDTM increases the load on TRX signalling slightly.

Impact on BSC units

BSC unit Impact

OMU No impact

MCMU No impact

BCSU DTM increases the load on the BCSU

slightly.

Table 3 Impact of DTM on BSC units













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Impact on BTS units

No impact.

2.5 User interface

2.5.1 BSC MMI

The following command groups and MML commands are used to handle DTM:

• Base Station Controller Parameter Handling in BSC: EEJ, EEO

• Base Transceiver Station Handling in BSC: EQO, EQV

• Adjacent Cell Handling: EAC, EAM, EAO

• Transceiver Handling: ERO

• GSM Measurement Handling: TPE, TPI, TPM, TPS

• Parameter Handling: WOC, WOI

• Licence and Feature Handling: W7M, W7I

For more information on the command groups and MML commands, see MML com-

mands.

2.5.2 BTS MMI

DTM cannot be managed with BTS MMI.

2.5.3 BSC parameters

BSC radio network object parameters

The following BSC radio network object parameters are related to DTM:

• DTM fragmentation penalty

• DTM PFC packet flow timer

• ISHO preferred for non-DTM MS

SEG-specific BTS radio network object parameters

The following SEG-specific BTS radio network object parameter is related to DTM:

• DTM enabled

Adjacent GSM (ADJC) radio network object parameters

The following adjacent GSM (ADJC) radio network object parameters are related to

DTM:

•DTM enabled

• DTM power budget margin

PCU DTM slightly increases the load on the

PCU. In addition, an active DTM call

decreases PCU connectivity with one16 kbit/s Abis timeslot.

BSC unit Impact

Table 3 Impact of DTM on BSC units (Cont.)



































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• NCCR EGPRS PBGT margin

• NCCR GPRS PBGT margin

For more information on the radio network object parameters, see BSS Radio Network

Parameter Dictionary .

PRFILE parameters

The following PRFILE parameters are related to DTM:

• DL_DTM_TBF_REL_DELAY

• DTM_CALL_ASSIGN_TIMER

• DTM_CALL_PENALTY_TIMER

• DTM_MS_CL_11_SUPPORT_EDA

• MAX_LAPD_LENGTH

• UL_DTM_TBF_REL_DELAY

• UL_DTM_TBF_RELDELAY_EXT

For more information on PRFILE parameters, see PRFILE and FIFILE Parameter List .

2.5.4 Alarms

DTM modifies the description of alarm 7725 TRAFFIC CHANNEL ACTIVATION

FAILURE.

2.5.5 Measurements and counters

The following measurements and counters are related to DTM.

1 Traffic Measurement

For more information, see 1 Traffic Measurement .

4 Handover Measurement

Name Number

DROPS AFTER DTM CS TCH ASSIGNMENT 001233

DTM CS TCH DROPS BETWEEN ASSCOMPL AND

RFCH REL ACK

001234

Table 4 Counters of Traffic Measurement related to DTM

Name Number

DTM MS HO ATTEMPTS TO DTM CELL 004190

DTM MS HO SUCCEEDED TO DTM CELL 004191

DTM MS HO ATTEMPTS TO NON DTM CELL 004192

DTM MS HO SUCCEEDED TO NON DTM CELL 004193

DTM CALL HO FROM DTM CELL SUCCEEDED 004194

DTM HO DUE LACK OF RESOURCES 004195

Table 5 Counters of Handover Measurement related to DTM





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For more information, see 4 Handover Measurement .

50 BSC Level Clear Code Measurement

For more information, see 50 BSC Level Clear Code Measurement .

51 BSC Level Clear Code (PM) Measurement

NON DTM BASED ISHO ATTEMPT 004196

NON DTM BASED ISHO SUCCESS 004197

DTM CALL HO ATTEMPTS TO DTM CELL 004198

DTM CALL HO SUCCESS TO DTM CELL 004199

DTM CALL HO ATTEMPTS TO NON DTM CELL 004200

DTM CALL HO SUCCESS TO NON DTM CELL 004201

Name Number

M TRAFFIC LOAD 0500938

Table 6 Counters of BSC Level Clear Code Measurement related to DTM

Name Number

INCOMING EXTERNAL DTM HO DUE NO PSRESOURCES AVAILABLE

051186

INCOMING EXTERNAL DTM HO DUE TRAFFIC 051187

INTER DTM HO DUE NO PS RESOURCES AVAILABLE 051188

INTRA DTM MO CS TO PS TERRITORY HO 051189

INTRA DTM MT CS TO PS TERRITORY HO 051190

INTRA DTM MT PS TO PS TERRITORY HO 051191

INTRA DTM PS TO CS TERRITORY HO 051192

OUTGOING EXTERNAL DTM HO DUE NO PS

RESOURCES AVAILABLE

051193

OUTGOING EXTERNAL DTM HO DUE DTM DISABLED 051194

OUTGOING EXTERNAL DTM HO DUE PS QUALITY

CONTROL

051195

OUTGOING EXTERNAL DTM HO DUE NO DTM

SUPPORT

051196

OUTGOING EXTERNAL DTM HO TO WCDMA 051197

INTER DTM HO DUE DTM DISABLED 051198

INTER DTM HO DUE PS QUALITY CONTROL 051199

INTER DTM HO DUE NO DTM SUPPORT 051200

Table 7 Counters of BSC Level Clear Code (PM) Measurement related to DTM

Name Number

Table 5 Counters of Handover Measurement related to DTM (Cont.)



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For more information, see 51 BSC Level Clear Code (PM) Measurement .

71 MS Capability Indication Measurement

For more information, see 71 MS Capability Indication Measurement .

72 Packet Control Unit Measurement

For more information, see 72 Packet Control Unit Measurement .

79 Coding Scheme Measurement

For more information, see 79 Coding Scheme Measurement .

97 Enhanced Quality of Service Measurement

For more information, see 97 Enhanced Quality of Service Measurement .

Name Number

TCH RESERV BY DTM MS 071037

REPORTING TIME BY DTM MS 071038

Table 8 Counters of MS Capability Indication Measurement related to DTM

Name Number

UL TBF RELEASES DUE DTM 072201

DL TBF RELEASES DUE DTM 072202

DL RLC CS1 BLKS TO DTM MS 072203

DL RLC CS2 BLKS TO DTM MS 072204

UL RLC CS1 BLKS FROM DTM MS 072205

UL RLC CS2 BLKS FROM DTM MS 072206

Table 9 Counters of Packet Control Unit Measurement related to DTM

Name Number

DL RLC MCS-N BLOCKS TO DTM MS 079010

UL RLC MCS-N BLOCKS FROM DTM MS 079011

Table 10 Counters of Coding Scheme Measurement related to DTM

Name Number

LLC BYTES UL DTM 097041

LLC BYTES DL DTM 097042

Table 11 Counters of Enhanced Quality of Service Measurement related to DTM



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105 PS DTM Measurement

Name Number

MT DTM CALL INITIAL REQUESTS 105000

MT DTM CALL CONTINUATION REQUESTS 105001

MT DTM CALL INITIAL REJECTIONS 105002

MT DTM CALL CONTINUATION REJECTIONS 105003

DTM REJECTIONS NO RESOURCES 105004

DTM REALLOCATION REQUESTS DUE PS QUALITY 105005

DTM REALLOCATION REQUESTS DUE PS OTHER 105006

DTM PS REALLOCATION REJECTIONS 105007

DTM TBF ASSIGNMENT FAILURES 105008

DTM ALLOCATIONS INITIAL 105009

DTM REALLOCATIONS 105010

DTM DURATION SUM FR 105011

DTM DURATION SUM HR

Not in use

105012

DTM FRAGMENTS 105013

TWO DTMS PACKED

Not in use

105014

PEAK OF SIMULTANEOUS DTM CS CONNECTIONS 105015

DTM REQUESTS OF 1 UL PS TSL 105016

DTM REQUESTS OF 2 UL PS TSL 105017

DTM REQUESTS OF 1 DL PS TSL 105018

DTM REQUESTS OF 2 DL PS TSL 105019

DTM REQUESTS OF 3 DL PS TSL

Not in use

105020

DTM ALLOCATIONS OF 1 UL PS TSL 105021

DTM ALLOCATIONS OF 2 UL PS TSL 105022

DTM ALLOCATIONS OF 1 DL PS TSL 105023

DTM ALLOCATIONS OF 2 DL PS TSL 105024

DTM ALLOCATIONS OF 3 DL PS TSL

Not in use

105025

UL DTM TBF ESTABLISHMENTS 105026

DL DTM TBF ESTABLISHMENTS 105027

UL DTM TBF DROPS DUE DOWNGRADE 105028

DL DTM TBF DROPS DUE DOWNGRADE 105029

UL DTM TBF DROPS ABNORMAL 105030

Table 12 Counters of PS DTM Measurement



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For more information, see 105 PS DTM Measurement .

106 CS DTM Measurement

For more information, see 106 CS DTM Measurement .

DL DTM TBF DROPS ABNORMAL 105031

Name Number

MO DTM CALL INITIAL REQUESTS 106000

MO DTM CALL CONTINUATION REQUESTS 106001

MO DTM CALL INITIAL REJECTIONS 106002

MO DTM CALL CONTINUATION REJECTIONS 106003

DTM CS ASSIGNMENT COMMANDS 106004

DTM PACKET ASSIGNMENT COMMANDS 106005

DTM CS REALLOCATION REQUESTS 106006

DTM CS REALLOCATION REJECTIONS 106007

DTM INITIAL ASSIGNMENT FAILURES 106008

DTM REALLOCATION ASSIGNMENT FAILURES 106009

MS LOST DURING ASSIGNMENT 106010

DTM RELEASES DUE PS RELEASE 106011

DTM RELEASES DUE CS RELEASE 106012

DTM RELEASES DUE CS HANDOVER 106013

DTM RELEASES DUE OTHER 106014

IGNORED INITIAL DTM REQUESTS 106015

IGNORED DTM CONTINUATION REQUESTS 106016

DTM IMSI NOT AVAILABLE 106017

DTM ASSIGNMENT COMMANDS 106018

GTTP MESSAGES UL 106019

GTTP MESSAGES DL 106020

GTTP MESSAGES DISCARDED 106021

PACKET NOTIFICATIONS 106022

PACKET NOTIFICATION FAILURES 106023

MS LOST DURING REALLOCATION 106024

Table 13 Counters of 106 CS DTM Measurement

Name Number

Table 12 Counters of PS DTM Measurement (Cont.)



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2.6 Impact on Network Switching Subsystem (NSS)

DX MSC (MSC)/DX HLR (HLR)

The MSC must provide the international mobile subscriber identity (IMSI) of the MSto the BSS in the COMMON ID and HANDOVER REQUEST messages if the MS and the

BSS are DTM-capable and the IMSI is available at the MSC. The MSC must be config-

ured or parameterized so that it can provide the IMSI. If the IMSI is not available during

a CS call establishment, DTM resources cannot be allocated. The Nokia Siemens

Networks MSC supports IMSI delivery from release M11 onwards.

In external handovers, the MSC provides the classmark information of the MS to the

target BSC, so that the target BSC knows whether the MS is DTM-capable (DTM multi-

slot class).

Serving GPRS support node (SGSN)

The MS Radio Access Capability information element (IE), which the SGSN provides,

contains DTM-specific fields.

The SGSN must provide the IMSI of the MS in the base station system GPRS

protocol (BSSGP) DL-UNITDATA protocol data units (PDUs) if the SGSN has a valid

IMSI for the MS. The IMSI must also be included in the PAGING PS and RA

CAPABILITY UPDATE ACK messages. It may also be included in the CREATE BSS

PFC message.

IP multimedia core (IMC)

The Nokia Siemens Networks IMS release 1 (for peer-to-peer PS connections) is

required for Session Initiation Protocol (SIP) sessions, such as DTM MS-to-MS calls

(for example, real time video sharing (RTVS)).

Charging

DTM has no impact on charging. According to the definition of a class A mobile, the CS

and PS components of a DTM call are independent of each other. Therefore, charging

is entirely an operator-specific issue.

2.7 Impact on NetAct products

NetAct Administrator

To enable hardware management with NetAct Administrator, you need to add a PCU2

unit to the product catalogue. DTM has no other impact on NetAct Administrator.

NetAct Monitor

No impact.

NetAct Optimizer

NetAct Optimizer allows you to optimize the capacity of the network in which DTM is

used. You can study DTM-related configuration and performance management data in

map and table formats in Optimizer. The GPRS territory settings algorithm optimizes the

values of the default and dedicated GPRS territories based on the CS and PS traffic

counters and key performance indicators (KPIs). The algorithm takes DTM traffic into

account when the territory settings are determined.













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NetAct Planner

DTM has no direct impact on NetAct Planner. However, DTM can be taken into consid-

eration when network traffic is planned and simulated with NetAct Planner.

NetAct Configurator

NetAct Configurator can be used to configure the radio network parameters related to

DTM. For more information, see BSS RNW Parameters and Implementing Parameter

Plans in Nokia Siemens Networks NetAct Product Documentation. For a list of the radio

network parameters, see chapter BSC parameters.

NetAct Reporter

NetAct Reporter can be used to create reports from measurements related to DTM. For

a list of the measurements, see chapter Measurements and counters.

NetAct Tracing

The values of the following counters of temporary bank flow (TBF) Observation for GPRS Trace are visible in the parameter tables in TraceViewer:

• 025312 TBF DTM FLAG

• 025313 MULTISLOT CLASS

• 025314 DTM MULTISLOT CLASS

In addition, the DTM flag is marked on a graphical report.

2.8 Impact on interfaces

Impact on radio interface

The following messages are related to DTM. Unless otherwise stated, the messages are

sent on the main associated control channel (DCCH).

• DTM ASSIGNMENT COMMAND

• DTM ASSIGNMENT FAILURE

• DTM INFORMATION

• DTM REJECT

• DTM REQUEST

• GPRS INFORMATION

• PACKET ASSIGNMENT

• PACKET NOTIFICATION

• PACKET SYSTEM INFORMATION TYPE 14This message is sent on the packet associated control channel (PACCH).

DTM modifies the following messages:

• GPRS SUSPENSION REQUEST

• SYSTEM INFORMATION TYPE 6

• SYSTEM INFORMATION TYPE 13

Impact on Abis interface

DTM introduces several new layer 3 messages that are transferred transparently over

the Abis interface.







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Impact on A interface

DTM modifies the following messages:

• HANDOVER REQUEST

• HANDOVER REQUIRED

When DTM is in use, both messages include a Dual Transfer Mode information field in

the information element (IE) Old BSS to New BSS information. In addition, the

HANDOVER REQUEST message includes an IMSI IE if the MSC knows the IMSI of the

mobile station (MS).

Impact on Gb interface

DTM modifies the following message:

• SUSPEND PDU

Q3 interface

DTM introduces several parameters and two BTS-level measurement types that have

an effect on the Q3 interface. For more information, see chapters BSC parameters and

Measurements and counters.

BSC-BSC interface

No effect.

2.9 Impact on mobile stations

DTM requires DTM-capable mobile stations (MSS). The MS must support at least DTM

multi-slot class 5.

2.10 Impact on capacity

IMSI coordination

In IMSI coordination, the CS connection control in the BSC (CS connection control)

informs the PCU about all DTM MSS that have a CS connection in the segment.

The PCU keeps an IMSI record for all the DTM-capable MSS that are in dedicated mode

in the DTM-capable cells that are connected to the PCU. For example, if 30% of the

MSS support DTM and the BSC has a total traffic handling capacity of 4000 Erl, about

0.3 x 4000 = 1200 IMSI records are needed per BSC. A single PCU2 can handle about

640 IMSI records.

The signalling load that IMSI coordination generates depends on the amount of DTM-

capable MSS in the network. When the amount of DTM-capable MSS is small, the sig-

nalling load is low. However, when the large majority of the MSS are DTM-capable, IMSI

coordination generates a considerable signalling load between the PCU and CS con-

nection control. If there are several PCUs within the BSC, the load is naturally balanced

between the PCUs.

In an overload situation, CS connection control may not be able to handle all the gener-

ated IMSI coordination messages, and some of the messages may be discarded. This

may have the following consequences:



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• The PCU might not receive an indication that a DTM MS has entered dedicated

mode. If the PCU receives a data PDU for the MS, the downlink temporary block

flow (TBF) establishment fails and the MS is considered as unreachable.

DTM traffic

The DTM traffic handling capacity depends on the CS and PS traffic handling capacity

of the system. Therefore, DTM must be taken into account in PS territory planning. Note

that the CS channel of a DTM call is allocated from the PS territory. Also note that the

DTM CS connection uses a full rate (FR) traffic channel.

A DTM CS radio timeslot (RTSL) in the PS territory cannot be used for data traffic.

Therefore, DTM call allocations can cause fragmentation to the PS timeslots when there

are several simultaneous ongoing DTM calls and the DTM-specific channel allocation

algorithm needs to allocate resources from the middle of the PS territory. When the PS

territory is fragmented, the PCU's capability to give multi-slot allocations for other data

connections decreases. Therefore, if DTM users are expected to contribute consider-

ably to the PS traffic load and the quality of experience (QoE) of the existing data users

cannot be decreased, it may be necessary to evaluate and possibly increase the size of

the PS territory.

The PCU can reallocate DTM resources within the PS territory to maintain the optimal

use of the PS territory. Reallocation causes an interruption in the DTM-PS data transfer.

Therefore, DTM calls are primarily allocated far from the CS-PS territory border. This

minimizes the number of DTM call reallocations, and results in less breaks in the PS

service for DTM users.

PCU connectivity

An active DTM call decreases PCU connectivity with one 16 kbit/s Abis timeslot. This

must be taken into consideration in dimensioning.

DTM CS allocations are handled by PCU2. One DTM CS allocation consumes one

RTSL from the PCU2 connectivity. This should be taken into consideration if the PCU is

limited by the number of RTSLs. If EDGE has been implemented in the network, the

number of connected RTSLs does not usually limit PCU connectivity.

GMM/SM signalling

Short message (SMS) and GPRS mobility management and session management

(GMM/SM) signalling messages are transmitted faster via DCCH signalling links than

using a new TBF (this is due to a TBF establishment delay). For SMS signalling mes-

sages, this only applies if the MS uses GPRS for sending SMSS. For more information

on GMM/SM signalling messages, see chapter GTTP signalling.

2.11 Impact on coverage

From the service perspective, it is best if all the cells within a certain geographical area

support DTM. This guarantees service continuity during cell changes.

DTM offers coverage for services that demand the simultaneous existence of a CS and

a PS connection. For example, when UMTS coverage is not available in the area,

GSM/EDGE coverage can be used.

The multi-slot power reduction of an MS may affect the uplink coverage. This is shown

in table Multi-slot power reduction.













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2.12 Impact on planning

DTM deployment

DTM can only be supported in cells that include a PS territory.

When you are planning on deploying DTM on top of an existing network, you should

follow the typical dimensioning process. Depending on your dimensioning strategy, youneed to calculate either the available capacity or the required capacity. For more infor-

mation, see BTS EDGE Dimensioning , Abis EDGE Dimensioning , and BSC EDGE

Dimensioning .

Coverage planning

In a layered environment it is often so that there is GPRS/EDGE capacity provided on

the coverage layer, whereas the capacity layer serves mainly CS traffic and has only the

minimum required GPRS/EDGE capacity for maintaining the service continuity in the

network. In this case the power budget parameters, NCCR EGPRS PBGT margin and

NCCR GPRS PBGT margin, can be used in the purpose of pushing the mobiles in DTM

call to the coverage layer. For more information about power budget handovers, seeInter-cell handover .

During a DTM call the uplink coverage might be reduced regarding uplink multi-slot allo-

cation. This needs to be taken into account in coverage planning. Multi-slot allocation

depends on the used services and might not be applicable for all services. In other

respects, the coverage of DTM does not differ from the coverage of speech calls and

EDGE connections.

Capacity planning

Capacity planning for DTM is influenced by the following factors:

• RTSL allocation (all DTM RTSLs--both CS and PS--are allocated from the PS terri-

tory)• used DTM applications and the typical DTM traffic profile

• PS territory fragmentation (a DTM CS RTSL cannot be used for PS data transfer)

• DTM call allocations and reallocations

If DTM services, such as RTVS, are used, additional capacity should be considered.

Because of the nature of the DTM connection (a simultaneous CS and PS connection),

DTM influences both CS and PS traffic. To a great extent, the impact of DTM depends

on the following factors in the network:

• penetration of DTM-capable MSS

• used DTM applications

• DTM traffic profile

Number of uplink timeslots Power reduction

1 0 dB

2 0..3 dB

3 1.8..4.8 dB

Table 14 Multi-slot power reduction



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• DTM service pricing

• existing data traffic and traffic mix

• CS traffic/blocking rate

DTM calls are allocated from the PS territory. This makes it possible to multiplex DTMTBFs and normal TBFs on the same timeslots.

A DTM call requires at least two packet data channels in the PS territory. Two channels

are required so that the DTM CS and PS connections can be allocated to the PS terri-

tory. If a territory upgrade is required before the DTM call can be allocated, it may slow

down the call establishment procedure.

When the number of DTM users increases, the average size of the CS territory

decreases. On the PS territory, territory fragmentation and PCU connectivity limitations

may cause blocking to the PS service.

To avoid the short breaks that the DTM call reallocations cause in the DTM PS data

transfer, the PCU allocates PS resources for the DTM users far from the CS-PS territory

border. In highly-loaded PS territories, however, the DTM-specific channel allocation

algorithm may have to allocate resources from the middle of the PS territory. This

causes fragmentation to the PS timeslots which decreases the PCU's capability to give

multi-slot allocations for other data connections. Simulations have shown that PS terri-

tory fragmentation has a negative impact on the QoE of the normal data users when the

ratio of DTM load to normal data load is higher than 20%. If the expected number of DTM

users at service launch is considered to be large, redimensioning of the existing network

is recommended. If the DTM user locations can be identified, some single cells that have

simultaneous DTM users may require more CS and PS RTSLs. Especially the PS terri-

tory may need to be increased if the other data services in the BTS require high data

rates or multi-slot allocations.

2.13 Interworking with other features

GPRS

GPRS must be available and active in the network for DTM to work.

If GPRS is deactivated when DTM is in use, the MSS that have an active DTM connec-

tion keep their CS connection but lose their TBFs.

For more information on GPRS, see BSS9006: GPRS System Feature Description. For

activation instructions, see Activating and Testing BSS9006: GPRS.

EGPRSThe BSC supports DTM data transfer in both GPRS and EGPRS modes.

A DTM TBF is established in EGPRS mode if the MS is EGPRS-capable and if the DTM

call is allocated from a EGPRS-capable PS territory. If not, the DTM TBF is established

in GPRS mode.

For more information on EGPRS, see BSS10091: EDGE System Feature Description.

For activation instructions, see Activating and Testing BSS10083: EGPRS.

Inter-system handover

An inter-system handover takes place between a GSM and a WCDMA network. The

BSC uses the service priority information from both the MSC and the SGSN in the inter-

system handover decision for a DTM-capable MS, if such information is available.





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For more information on how inter-system handovers work with DTM, see chapter Inter-

system handover. For more information on inter-system handover, see BSS10101 and

BSS11107: GSM-WCDMA Interworking .

Adaptive Multi Rate

The BSC selects an adaptive multi rate (AMR) speech codec for a new DTM CS con-

nection if AMR was used on the preceding CS connection of the call.

For more information on AMR, see BSS10004 and BSS6071: Enhanced Speech

Codecs: AMR and EFR .

Common BCCH and Multi BCF

By default, RX-level based traffic channel (TCH) access control is not used in normal

CS channel allocation for evaluating the usability of resources in different BTSs of a

segment. However, it is used as a standard procedure with DTM.

For more information on Common BCCH Control, see BSS10016 and BSS10118:

Common BCCH Control in BSC . For more information on Multi BCF Control, see

BSS10046: Multi BCF Control in BSC .

Radio Network Supervision

DTM has an effect on the following supervisions:

• The Too short mean holding time supervision is not used for channels that are used

for DTM CS connections.

• The Cell channel congestion supervision does not count DTM requests.

Other supervisions are used for DTM CS connections as usual.

For more information on Radio Network Supervision, see BSC3100: Radio Network

Supervision in BSC .

Extended Dynamic Allocation

Extended dynamic allocation (EDA) mode enhances the data transmission capability in

the uplink direction. In EDA mode, it is possible to allocate two PS timeslots in the uplink

direction for a DTM multi-slot class 11 MS. In dynamic allocation (DA) mode, it is

possible to allocate only one PS timeslot in the uplink direction in dual transfer mode.

Note that an MS may reduce its output power depending on the number of allocated

uplink timeslots. The power reduction is not taken into account in the initial DTM alloca-

tion.

For more information on EDA, see BSS20089: Extended Dynamic Allocation.

For more information on DTM allocations, see chapter DTM multi-slot classes.

Queuing and Pre-emption

Queuing is not applied to DTM requests.

The DTM CS channels are not targets of pre-emption procedures (forced release and

forced handover).

For more information on queuing and pre-emption, see Radio Resource Pre-emption

and Queuing .

Soft Channel Capacity

The maximum number of simultaneously active traffic channels in a BSC signalling unit

(BCSU) is determined by the configuration of the unit. With Soft Channel Capacity, the





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BSC regards the DTM CS allocations as active traffic channels, that is, just like normal

CS connections.

For more information on Soft Channel Capacity, see BSS115173: Soft Channel

Capacity in BSC .

Network-Controlled Cell Re-selection

The PCU does not apply network-controlled cell re-selection (NCCR) procedures for

an MS in dual transfer mode. However, NCCR is used normally for DTM-capable MSS

that do not have an ongoing CS connection.

If the PS quality control function triggers NCCR for a DTM call, the BSC performs an

inter-cell handover for the related CS connection.

For more information on NCCR, see BSS11112: Network-Controlled Cell Re-selection.

The NCCR parameters, NCCR EGPRS PBGT margin and NCCR GPRS PBGT margin,

are used in power budget handovers when a mobile is in DTM call. For more information

about power budget handovers, see Inter-cell handover .

Network-Assisted Cell Change

The PCU does not apply network-assisted cell change (NACC) procedures for an MS

in dual transfer mode. However, NACC is used normally for DTM-capable MSS that do

not have an ongoing CS connection.

Note that NACC procedures (that is, the use of PACKET SI STATUS messages) reduce

the PS interruption time when a DTM call is released because of a CS call release and

the PS connection needs to be re-established in normal GPRS/EDGE mode.

For more information on NACC, see BSS115006: Network-Assisted Cell Change.

In-call modification

In-call modification takes place when a CS speech call needs to be changed to a CS

data call. If an in-call modification procedure is started during a DTM call, the BSC

releases the DTM call.

Power control

In a DTM call, the power control algorithm limits the downlink transmission power of the

DTM CS connection to be between [PMAX - 10 dB, PMAX]. PMAX is the maximum

downlink transmission power that can be used in the transceiver (TRX).

Intelligent Underlay-Overlay, Handover Support for Coverage Enhancements, and

Enhanced Coverage by Frequency Hopping

The BSC does not support super-reuse frequencies for GPRS. Therefore, it does not

initiate handovers towards super-reuse resources for ongoing DTM connections. If a

DTM call is started from the super-reuse layer, it leads to a handover to the regular layer.

Like GPRS/EDGE, DTM is not supported in a child cell, that is, in a cell that contains

only super-reuse resources.

For more information on Intelligent Underlay-Overlay, see BSC4016: Intelligent

Underlay-Overlay . For more information on Handover Support for Coverage Enhance-

ments, see BSS7064: Handover Support for Coverage Enhancements. For more infor-

mation on Enhanced Coverage by Frequency Hopping, see BSS8037: Enhanced

Coverage by Frequency Hopping .









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Circuit-switched data

The BSC does not support dual transfer mode for an MS that has an ongoing circuit-

switched data call. The call can be either a high speed circuit switched data (HSCSD)

call or a single-slot data call.For more information on circuit-switched data, see BSS7003 and BSS7037: HSCSD

and 14.4 kbit/s Data Services in BSC .

Direct Access to Desired Layer/Band

Direct Access to Desired Layer/Band (DADL/B) makes it possible to move calls to

capacity layer cells during the CS call setup phase. In many cases, in a layered environ-

ment GPRS/EDGE is implemented mainly on the coverage layer. The capacity layer

serves mainly CS traffic and has only the minimum required GPRS/EDGE capacity for

maintaining the service continuity in the network. Therefore, whenever the BSC detects

during the CS call setup phase that an MS requires DTM service, it prevents the DADL/B

handover from taking place for the MS in question.

For more information on DADL/B, see BSS8032: Direct Access to Desired Layer/Band .

Extended Cell and Extended Cell for GPRS/EDGE

An MS can initiate and receive DTM calls successfully only when it is in the normal area

of the cell. DTM calls are not supported in the extended area of the cell.

For more information on Extended Cell, see BSC4015: Extended Cell . For more infor-

mation on Extended Cell for GPRS/EDGE, see BSS20094: Extended Cell for

GPRS/EDGE .

TRAU Bicasting in AMR FR/HR Handover

Transcoding and rate adaptation unit (TRAU) Bicasting in AMR full rate/half rate(FR/HR) Handover is applied to CS to DTM CS handovers when the channel mode is

changed from AMR HR to AMR FR and conditions for TRAU Bicasting in AMR FR/HR

Handover are met. Because AMR HR for DTM calls is not supported, TRAU Bicasting

in AMR FR/HR Handover is not applied to CS to DTM CS handovers in which the source

channel mode is AMR FR.

For more information on TRAU Bicasting in AMR FR/HR Handover, see BSS10004 and

BSS6071: Enhanced Speech Codecs: AMR and EFR .



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IMSI co-ordination

3 IMSI co-ordinationThe BSC must know the international mobile subscriber identity (IMSI) of a mobile

station (MS) to be able to provide dual transfer mode for DTM-capable MSS. The IMSI

is needed for co-ordination and identification purposes. Without the IMSI, the BSC

cannot co-ordinate the circuit-switched (CS) and packet-switched (PS) resources.

During a CS call establishment, the MSC sends the IMSI to the CS connection control

in the BSC (CS connection control) in a COMMON ID message, provided that the IMSI

of the MS is available at the MSC and that the MSC has been configured to send the

information. In external handovers, the IMSI is sent in the HANDOVER REQUEST

message.

The packet control unit (PCU) needs to know when a DTM MS is in dedicated mode.

This information is needed in PS paging co-ordination, DTM call handling, and GPRS

transparent transport protocol (GTTP) signalling procedures. Therefore, CS connection

control informs the PCU whenever a DTM-capable MS enters or leaves dedicated modein a DTM-capable cell. The PCU keeps a record (IMSI record) of all DTM-capable MSS

that are in dedicated mode in a DTM-capable cell under the PCU.

The IMSI co-ordination procedure consists of the following steps:

1. During the CS call establishment, the MSC sends the IMSI of the MS to CS connec-

tion control in a COMMON ID message.

2. CS connection control sends the IMSI to the PCU.

3. The PCU creates a dedicated IMSI context for the MS that is in dedicated mode.

4. The PCU receives downlink logical link control (LLC) protocol data units (PDUs)

for the MS. Because the PCU has a dedicated IMSI context for the MS, it establishes

a temporary block flow (TBF) in dual transfer mode.

5. When the CS call is released, CS connection control informs the PCU.

6. The PCU removes the dedicated IMSI context from the IMSI record.











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BSS20088: Dual Transfer Mode Paging coordination

Id:0900d80580590b15

4 Paging coordination

CS paging

Dual Transfer Mode (DTM) does not change the circuit-switched (CS) paging proce-dures in the BSC.

• A mobile station (MS) that is not GPRS attached is always paged for CS calls on the

paging channel (PCH).

• In Network Operation Mode I (NOM I), the core network provides CS paging coordi-

nation so that CS paging requests to GPRS-attached MSS are sent to the PCU via

the SGSN. The PCU provides CS paging on the packet associated control

channel (PACCH) if the MS is in packet transfer mode. If the MS is in packet idle

mode, it is paged for CS calls on the PCH.

• In Network Operation Mode II (NOM II), all CS paging requests are sent on the PCH.

This means that if a DTM-capable MS is in packet transfer mode, it does not neces-

sarily monitor the PCH and, therefore, does not respond to the CS paging.

CS paging uses the same channel as the PS services: common control channel

(CCCH) or PACCH during data transfer. The MS needs to monitor only one paging

channel. Figure Paging coordination illustrates the paging process.

Figure 4 Paging coordination

A Nokia Siemens Networks BSC needs the Gs interface for full paging coordinationsupport. The Gs interface is used in Network Operation Mode I (NOM I). If NOM II is

used, the MS may not respond to the CS paging while the MS is in packet transfer state.

Note that it is essential to have dedicated PS timeslots with NOM I to guarantee that

GPRS-attached subscribers can perform routing area (RA) and location area (LA)

update procedures when moving from one RA/LA to another in the network.

PS paging

DTM introduces a packet notification procedure in which a DTM-capable MS can be

paged for PS calls in dedicated mode. This means that instead of paging the MS on the

PCH, CS connection control in the BSC (CS connection control) informs the MS about

the PS paging request by sending a PACKET NOTIFICATION message on the main

CCCH

or Packet data channel

BSC MSC

2GSGSN

A

Gs

Gb

GSM CSvoice calls

GSM CSvoice calls













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Paging coordination

associated control channel (DCCH) if the MS is DTM capable and in dedicated mode

in a DTM-capable cell.

PS paging is illustrated in figure PS paging procedure.

Figure 5 PS paging procedure

1. The SGSN sends a PS paging protocol data unit (PDU) to the PCU.

2. The PCU checks from the international mobile subscriber identity (IMSI) record

whether the MS is in dedicated state.

Because of IMSI coordination, the PCU is always aware of which DTM-capable MSS

are in dedicated state.

3. As the MS is in dedicated mode, the PCU sends the PS paging request to CS con-

nection control.

4. CS connection control sends the PACKET NOTIFICATION message to the MS on

the DCCH.

If the MS is not in dedicated mode, the PCU sends the PS paging request to CS con-

nection control, which then sends it onwards on the PCH as usual.

PS paging PDU

PS paging request

SGSNPCUCS connection

control in the BSCBTSMS

PACKET NOTIFICATION

IMSI record check







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BSS20088: Dual Transfer Mode GTTP signalling

Id:0900d80580590b18

5 GTTP signallingWhen a Dual Transfer Mode (DTM) capable mobile station (MS) is in dedicated mode

in a DTM-capable cell, the CS connection control in the BSC (CS connection control)

and MS can use the main associated control channel (DCCH) for GPRS mobility

management and session management (GMM/SM) signalling. The GMM/SM signal-

ling messages are transmitted within GPRS INFORMATION messages (layer 3

message) using a GPRS transparent transport protocol (GTTP). With GTTP, there is no

need for a separate radio connection (that is, no temporary block flows (TBFs) are

needed for the GMM/SM signalling). Therefore, GTTP provides a fast signalling link for

GMM/SM messages.

GTTP signalling in uplink

When a DTM-capable MS is in dedicated mode in a DTM-capable cell, it can use the

GPRS INFORMATION message to send a logical link control (LLC) protocol data unit

(PDU) to CS connection control on the DCCH. However, the following conditions mustbe met:

• The LLC PDU contains upper layer signalling (that is, a GMM or SM signalling

message) or the LLC PDU is used as a cell update message.

• The length of the message in link access protocol on the Dm channel (LAPDm)

frames is equal to or less than the value of the MAX_LAPD_LENGTH parameter.

The MAX_LAPD_LENGTH parameter specifies the maximum length of the GTTP

message.

Uplink GTTP signalling is illustrated in figure GTTP signalling procedure in uplink.

Figure 6 GTTP signalling procedure in uplink

1. The MS in dedicated mode sends a GPRS INFORMATION message to CS connec-

tion control.

The GPRS INFORMATION message contains the temporary logical link identity

(TLLI) of the MS and the LLC PDU that contains the GPRS signalling message.

2. CS connection control sends the TLLI and LLC PDU to the PCU.

3. The PCU sends the LLC PDU to the SGSN.

GTTP signalling in downlink

When the PCU receives a downlink LLC PDU for a DTM-capable MS that has a CS con-

nection in the cell without ongoing TBFs, the PCU can use GTTP signalling to transmit

the LLC PDU to the MS. However, the following conditions must be met:

GPRS INFORMATION

TLLI, LLC PDU

LLC PDU

SGSNPCUCS connection

control in the BSCBTSMS



















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GTTP signalling

• The downlink LLC PDU contains a signalling message.

This is indicated by the T bit in the QoS Profile information element (IE) in the

BSSGP DL UNITDATA PDU.

•The length of the message in the LAPDm frames is equal to or less than the valueof the MAX_LAPD_LENGTH parameter.

Downlink GTTP signalling is illustrated in figure GTTP signalling procedure in downlink.

Figure 7 GTTP signalling procedure in downlink

1. The SGSN sends the LLC PDU to the PCU.

2. The PCU checks from the international mobile subscriber identity (IMSI) record

whether the MS is in dedicated state.

Because of IMSI co-ordination, the PCU is always aware of which DTM-capable

MSS are in dedicated state.

3. The PCU forwards the LLC PDU to CS connection control.

4. CS connection control uses the GPRS INFORMATION message to send the LLC

PDU to the MS on the main DCCH.

GPRS INFORMATION

LLC PDU

PCUBTSMS SGSN

LLC PDU

CS connectioncontrol in the BSC

IMSI

record check





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35

BSS20088: Dual Transfer Mode Radio resource management

Id:0900d80580590b1b

6 Radio resource managementThe BSC reserves radio resources for a Dual Transfer Mode (DTM) call from the packet-

switched (PS) territory. This makes it possible to share the PS resources between DTM

connections and normal PS connections. DTM allocation to the PS territory provides

multiplexing gain when DTM temporary block flows (TBFs) and normal TBFs are

allocated on the same timeslots. The PCU decides if and how a DTM allocation is made.

6.1 DTM allocation for PS connections

When a DTM call is to be allocated for a mobile station (MS), the DTM circuit-switched

(CS) connection is allocated close to the PS territory border, if possible. If the DTM-

capable MS supports DTM multislot class 5 or 9, the PS timeslot furthest from the CS-

PS territory border is selected for the DTM CS connection. If the DTM-capable MS

supports DTM multislot class 11, the PS timeslot second furthest from the CS PS terri-

tory border is selected for the DTM CS connection.

However, if there are DTM PS allocations for other MSS close to the PS territory border,

the DTM CS connection is allocated to a timeslot that has no DTM PS allocations, if pos-

sible. If such a timeslot cannot be found, a timeslot with a DTM PS allocation is consid-

ered.

Once a suitable timeslot for the DTM CS connection has been found, the DTM PS

resources are reserved for the DTM call so that the DTM CS timeslot and the DTM PS

timeslots form a collective allocation configuration that the DTM-capable MS can

manage within its multislot capability. For more information, see DTM multislot classes.

If there are several alternatives for a DTM allocation, a DTM allocation that avoids the

fragmentation of the PS resources and gives optimal resources for the PS part of theDTM allocation is preferred.

Once a suitable DTM allocation has been found, the PCU tries to search for new

resources for the PS allocations that are currently using the timeslot selected for the

DTM CS connection. If the PCU finds new resources for all affected PS allocations, the

DTM allocation is accepted. If not, the DTM allocation is rejected.

6.2 DTM multislot classes

The BSC supports DTM multislot classes 5, 9, and 11. The multislot capability of an MS

is indicated as a part of the radio access capability information of the MS.

The BSC supports dynamic allocation (DA) and extended dynamic allocation (EDA)modes for uplink TBFs that operate in dual transfer mode. In EDA mode, it is possible

to allocate two PS timeslots in the uplink direction for a DTM multislot class 11 MS. In

DA mode, it is possible to allocate only one PS timeslot in the uplink direction in dual

transfer mode. Figure DTM multislot allocations illustrates how PS and CS resources

can be allocated for multislot classes 5, 9, and 11. The PS and CS resources must be

in consecutive timeslots.







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Radio resource management

Figure 8 DTM multislot allocations

6.3 Fragmentation of the PS resources

A DTM call within the PS territory causes the fragmentation of the PS resources if the

timeslots configured for PS services become scattered because of the DTM CS

resource reservation. If the timeslots configured for PS services are no longer consec-

utive, it is more difficult to make multislot PS allocations for other users. This is becausethe timeslots that belong to a multislot PS allocation must be subsequent. Therefore, the

timeslots that avoid the fragmentation of the PS resources are preferred over the other

timeslots in the DTM channel allocation procedure.

Sometimes, a trade-off situation may occur. For example, DTM allocation candidate A

that increases the fragmentation of the PS resources may give more capacity to the

DTM PS connection than DTM allocation candidate B that does not increase the frag-

mentation of the PS resources. This kind of a situation can be balanced with the DTM

fragmentation penalty parameter.

The DTM fragmentation penalty parameter specifies the fragmentation penalty

that is used in the DTM channel allocation algorithm if a configuration that gives the

highest capacity for the DTM-capable MS must be found. This happens if there are DTM

PS allocations for other MSS near the end of the PS territory.

The capacity of a DTM PS allocation is estimated in terms of radio timeslots. The frag-

mentation penalty is subtracted from the estimated capacity value if the DTM allocation

would increase the fragmentation of the PS resources.

Example:

Figure DTM allocation example illustrates the use of the DTM fragmentation

penalty parameter.

CS

Downlink radio timeslots:

Uplink radio timeslots:

DTM class 5,9,112+2=4 DA

DTM class 5,9,112+2=4 DA

DTM class 9,113+2=5 DA

DTM class 9,113+2=5 DA

DTM class 112+3=5 EDA

0 1 2 3 4 75 6

0 1 2 3 4 75 6

PS

PS CS

CSPS

CS PS

CS PS

PS PS CS

PS CS

PS CS PS

PSCS

PS CS

PS



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BSS20088: Dual Transfer Mode Radio resource management

Id:0900d80580590b1b

Figure 9 DTM allocation example

DTM allocation candidate A contains two DTM PS timeslots. We assume that the DTM-

capable MS gets a 50% share of the first PS timeslot (the other 50% is given to another

PS connection) and a 100% share of the second PS timeslot. We also assume that DTM

allocation candidate A increases the fragmentation of the PS resources and that theDTM

fragmentation penalty parameter has a value of 0.3. The capacity of DTM alloca-

tion A is therefore 1.2 timeslots (0.5 + 1.0 - 0.3 = 1.2).

DTM allocation candidate B contains one DTM PS timeslot. We assume that the DTM-

capable MS gets a 100% share of that PS timeslot. We also assume that DTM allocation

candidate B does not increase the fragmentation of the PS resources. The capacity of

the DTM allocation B is therefore 1.0 timeslots.

In this example, DTM allocation candidate A is selected for the DTM call. This is

because the capacity of DTM allocation candidate A is larger than the capacity of DTM

allocation candidate B. However, had the DTM fragmentation penalty parameter

had a larger value, for example 0.6, then DTM allocation candidate B would have been

selected instead.

The DTM fragmentation penalty parameter can have values between 0 and 1.

Value 0 means that a DTM allocation that does not increase the fragmentation of the PS

resources is not preferred over a DTM allocation that increases the fragmentation of the

PS resources. Value 1 means that a DTM allocation that does not increase the fragmen-

tation of the PS resources is selected instead of a DTM allocation that increases the

fragmentation of the PS resources. However, if the latter one provides one timeslot more

capacity than the former one, the latter one is selected.

6.4 Territory management

The PCU allocates radio resources for DTM calls from the PS territory. This makes it

possible to share the PS resources between DTM PS connections and normal PS con-

nections.

It is not necessary to increase PS capacity when DTM is introduced in the network.

However, when DTM is in use and the size of the PS territory is determined, all timeslots

within the PS territory must be taken into account. This means timeslots configured for

PS use and timeslots configured for DTM CS use. It is advisable to have at least two

default channels in the PS territory.

TSL-0 TSL-1 TSL-2 TSL-3 TSL-4 TSL-5 TSL-6 TSL-7

existingTBF

DTM allocation candidate A:

DTM allocation candidate B:

PS timeslot share:

PS timeslot share: 100%

50% 100%

DTM PS DTM CS DTM PS

DTM CSDTM PS

CS

PS



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Radio resource management

Territory upgrade

The CS connection control in the BSC (CS connection control) initiates a territory

upgrade if the number of timeslots configured for PS use in the PS territory drops below

the dedicated GPRS/EDGE capacity because of the made DTM allocations.The PCU requests a territory upgrade in the following cases:

• If the PS territory is, by default, too small for a DTM allocation (it contains only one

PS timeslot) during an ongoing DTM call establishment.

If the PS territory is too small for a DTM allocation, CS connection control delays the

DTM call establishment for a short period of time and initiates a territory upgrade

procedure, if possible. After a short while, as the upgrade is expected to have fin-

ished, CS connection control continues with the pending DTM call establishment.

• The load on the timeslots configured for PS use increases over the current thresh-

olds.

When the PS load is determined, only the timeslots configured for PS use are taken

into account. The DTM CS timeslots are not considered.

Territory downgrade

The PCU requests a territory downgrade in the following case:

• The load of the timeslots configured for PS use drops below the current thresholds

and the size of the PS territory is larger than the size of the default PS territory.

The PCU ensures that the number of the timeslots configured for PS use does not

drop below the dedicated GPRS/EDGE capacity.

CS connection control triggers a territory downgrade if the CS load increases.

Timeslot types in the PS territory

A DTM CS timeslot is seen as part of the PS territory when the size of the territory is

determined. However, only a timeslot configured for PS use can be interpreted as a ded-

icated GPRS/EDGE timeslot. The PCU interprets a timeslot with a DTM CS connection

as a default GPRS/EDGE timeslot or as an additional GPRS timeslot but never as a ded-

icated GPRS/EDGE timeslot.



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BSS20088: Dual Transfer Mode Dual Transfer Mode call establishment

Id:0900d80580590b1e

7 Dual Transfer Mode call establishment

7.1 Mobile-originated call establishment A Dual Transfer Mode (DTM) capable mobile station (MS) can request a DTM call when

it has a circuit-switched (CS) connection in a DTM-capable cell. The MS requests a DTM

call by sending a DTM REQUEST message to the CS connection control in the BSC (CS

connection control). If the MS has a CS traffic channel (TCH), the DTM REQUEST

message is sent on the fast associated control channel (FACCH). Otherwise, the DTM

REQUEST message is sent on the stand-alone dedicated control channel (SDCCH).

When CS connection control receives a DTM request from a DTM-capable MS, it estab-

lishes, with the PCU, a mobile-originated (MO) DTM call for the MS if the following con-

ditions are met:

• The DTM MS has a TCH allocated for a CS speech call.

• The international mobile subscriber identity (IMSI) of the MS is known.

• The DTM request is received from the normal area (that is, not the extended area)

of the cell.

• The PCU can find suitable radio resources for the DTM call.

The MO DTM call establishment procedure is illustrated in figure MO call establishment.

Figure 10 MO call establishment

1. The MS sends a DTM REQUEST message to CS connection control on the FACCH.

The message contains the temporary logical link identity (TLLI) of the MS and a

channel request description.

2. CS connection control forwards the DTM resource request to the PCU.

PCUBTSMS

DTM resource request

DTM REQUEST

Reply to DTMresource request

DTM ASSIGNMENT COMMAND

ASSIGNMENT COMPLETE

Information that the MS hasmoved to the new resources

PS data sending indual transfer mode

AC and radio resourceallocation for the DTM call

Uplink RLC blockscheduling

CS connectioncontrol in the BSC











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Dual Transfer Mode call establishment

3. The PCU performs admission control (AC) for the DTM call.

4. The PCU allocates radio resources for the DTM call by using the DTM-specific

channel allocation function.

5. The PCU establishes an uplink temporary block flow (TBF) for the MS in dualtransfer mode.

The TBF is in EGPRS mode if the MS supports EGPRS and if the DTM allocation is

made into a PS territory that supports EGPRS. If not, the TBF is in GPRS mode.

6. The PCU sends a reply to the DTM resource request to CS connection control.

The message contains information on the DTM allocation (CS resource and TBF

allocation).

7. CS connection control sends a DTM ASSIGNMENT COMMAND message to the MS

on the FACCH.

The message contains the DTM call assignment (new CS resource and uplink TBF

assignment).

8.The MS moves to the assigned resources and sends an ASSIGNMENT COMPLETE message to CS connection control on the FACCH.

9. CS connection control informs the PCU when the MS has moved to the new

resources.

10. The PCU starts to schedule uplink radio link control (RLC) blocks (that is, uplink

state flags) for the MS on the timeslots that belong to the uplink TBF allocation.

11. The MS sends PS data on the assigned resources in dual transfer mode.

Exceptions in MO call establishment

An MS requests for PS resources on the SDCCH

If a DTM-capable MS sends a DTM REQUEST message on the SDCCH before a trafficchannel assignment, CS connection control does not establish a DTM call but sends a

DTM REJECT message to the MS and continues the CS call establishment as usual.

This is because it is not possible to have a DTM call that consists of a DTM PS connec-

tion and a SDCCH connection.

The DTM REJECT message contains a Wait Indication information element (IE) that

determines how long the MS must wait before it can make a new attempt for packet

access in the same cell. The wait indication time used on the SDCCH channel is two

seconds.

7.2 Mobile-terminated call establishmentWhen the PCU receives a downlink logical link control (LLC) protocol data unit

(PDU) for a DTM-capable MS that is in dedicated mode in a DTM-capable cell, it initiates

a mobile-terminated (MT) DTM call establishment for the MS. The MT DTM call is estab-

lished if the following conditions are met:

• The MS has a TCH allocated for a CS speech call.

• The IMSI of the MS is known.

• The MS is in the normal area (that is, not the extended area) of the cell.

• The PCU can find suitable radio resources for the DTM call.

The MT DTM call establishment procedure is illustrated in figure MT DTM call establish-

ment.













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BSS20088: Dual Transfer Mode Dual Transfer Mode call establishment

Id:0900d80580590b1e

Figure 11 MT DTM call establishment

1. The SGSN sends the PCU a downlink LLC PDU, addressed to an MS. The PCU

does not have a resource reservation for the MS.

The received MS Radio Access Configurator (RAC) IE indicates that the MS

supports DTM.

2. The PCU checks from the IMSI record whether the MS is in dedicated state.

Because of IMSI co-ordination, the PCU is always aware of which DTM MSS are in

dedicated state.

3. As the MS is in dedicated mode, the PCU initiates an MT DTM call establishment

procedure for the MS.

4. The PCU performs AC for the DTM call.

5. The PCU allocates radio resources for the DTM call by using the DTM-specific

channel allocation function.

6. The PCU establishes a downlink TBF for the MS in dual transfer mode.

The TBF is in EGPRS mode if the MS supports EGPRS and if the DTM allocation is

made into a PS territory that supports EGPRS. If not, the TBF is in GPRS mode.

7. The PCU informs CS connection control about the DTM allocation (CS resource and

TBF allocation).

AC and radio resourceallocation for the DTM call

LLC PDU

IMSI record check

MT DTM call initiation

TBF in dual transfer mode

DTM allocation information

Information that the MS hasmoved to the new resources

Downlink RLCblock scheduling

PS data receiving indual transfer mode

PCUCS connection

control in the BSCBTSMS SGSN

DTM ASSIGNMENT COMMAND

ASSIGNMENT COMPLETE



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Dual Transfer Mode call establishment

8. CS connection control sends a DTM ASSIGNMENT COMMAND message to the MS

on the DCCH.

The message contains the DTM call assignment (new CS resource and downlink

TBF assignment).

9. The MS moves to the assigned resources and sends an ASSIGNMENT COMPLETE

message to the network on the FACCH.


resources.

11. The PCU starts to schedule downlink radio link control (RLC) blocks for the MS on

the timeslots that belong to the downlink TBF allocation.

12. The MS receives PS data on the assigned resources in dual transfer mode.



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BSS20088: Dual Transfer Mode Handover control

Id:0900d80580590b21

8 Handover control

8.1 Intra-cell handover In an intra-cell handover, the CS connection control in the BSC (CS connection control)

moves the Dual Transfer Mode (DTM) call to other timeslots within the cell. Both CS con-

nection control and the PCU can trigger an intra-cell handover.

CS connection control may initiate an intra-cell handover if the DTM circuit-switched

(CS) connection needs to be moved to another timeslot because of quality reasons.

The PCU may initiate an intra-cell handover when the following procedures trigger a

DTM reallocation procedure:

• territory downgrade (or territory downgrade permission request)

• PS quality control

• DTM PS resource management

The intra-cell handover procedure consists of the following steps. Except for the first

step, the procedure is identical for a CS-connection-control-initiated and a PCU-initiated

intra-cell handover.

1. CS connection control requests new resources for the DTM call from the PCU.

This step only applies to a CS-connection-control-initiated intra-cell handover.

2. The PCU determines a new DTM allocation for the MS.

3. Once the PCU has found new resources for the DTM call, it stops scheduling the

packet-switched (PS) resources that belong to the old DTM allocation and informs

CS connection control about the new DTM allocation.

4.CS connection control sends a DTM ASSIGNMENT COMMAND message to the MSon the associated control channel (DCCH).

The message contains the new CS resource and a reassignment for the ongoing

temporary block flows (TBFs).

5. The MS moves to the assigned resources and sends an ASSIGNMENT COMPLETE

message to the network on the fast associated control channel (FACCH).


resources.

7. The PCU resumes the uplink state flag (USF) and/or radio link control (RLC) block

scheduling for the MS on the new PS resources.

8. The MS continues the DTM call on the new resources.

An intra-cell handover is performed for the CS connection also when the MS is movedfrom the CS territory to the PS territory in DTM call establishment.

The following intra-cell handovers are not allowed for DTM calls:

• handovers between regular and super re-used transceivers (TRX)

• load-based handover between the BTSs in the segment

8.2 Inter-cell handover

CS connection control handles the handover procedure for DTM calls. Therefore, the

PCU does not apply the network controlled cell re-selection (NCCR) or network

assisted cell change (NACC) procedures for a DTM-capable MS when it is in dedi-

















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Handover control

cated mode. The PCU may, however, request an inter-cell handover for a DTM call in

the following cases:

• PS quality control triggers a cell change for the DTM PS connection.

• MT DTM call establishment fails because of lack of resources.

When CS connection control performs an inter-cell handover for a DTM-capable MS, it

favours cells that support DTM to provide and maintain the DTM service for the MS. This

means that CS connection control must know whether the adjacent cell supports DTM.

This information is provided by the adjacent cell parameter DTM enabled. When an

inter-cell handover is triggered, CS connection control searches the neighbor cells for

DTM support. The adjacent cells in which the DTM enabled parameter is enabled and

which are not overloaded or have a smaller load than the serving cell, are put on top of

the candidate cell list. This preference for DTM-capable adjacent cells overrides the

preference rules that are normally followed, that is, the value of the TCH in handover

parameter that defines the traffic channel allocation in intra-BSC inter-cell handovers.

CS connection control triggers an inter-cell handover for a DTM CS connection byapplying existing handover algorithms. In the handover, the CS connection is moved to

the CS territory of the target cell and the DTM call in the source cell is released. After

the handover has been completed, CS connection control sends a DTM INFORMATION

message to the MS on the DCCH if the target cell supports DTM. The DTM call is then

re-established in the target cell.

For more information on existing handover algorithms, see RF Power Control and

Handover Algorithm.

The following inter-cell handovers are not allowed for DTM calls:

• MSC-controlled traffic reason handover

• BSC-initiated traffic reason handover • umbrella handover

• inter-cell direct access

• intelligent underlay overlay (IUO) handover to a child cell

MO DTM call establishment or DTM call reallocation fails because of lack of

resources

If a mobile-originated (MO) DTM call establishment or a DTM call reallocation fails

because of lack of resources in the PCU, CS connection control searches for another

DTM-capable cell in which the DTM call can be established or re-established. CS con-

nection control performs a handover to another DTM capable cell when Equation 1 is

true.EQUATION 1

AV_RXLEV_NCELL(n) > RxLevMinCell(n) + MAX(0, Pa)

AND

PBGT(n) > dtmPowerBudgetMargin(n)

where

Pa = (MsTxPwrMaxGSM(ADJ)(n) - P) or (MsTxPwrMaxGSM1x00(ADJ)(n) - P)

P = Maximum power of an MS





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A power budget (PBGT) handover back to the source cell is allowed for the same call

after a guard time of 255 seconds.

If an inter-cell handover, triggered by an unsuccessful MO DTM call establishment

attempt, cannot be performed, or if the handover does not succeed, CS connectioncontrol rejects the DTM call request.

If an inter-cell handover, triggered by an unsuccessful DTM CS call reallocation attempt,

cannot be performed, or if the handover does not succeed, CS connection control

releases the DTM call by performing an intra-cell handover from the PS territory to the

CS territory of the cell.

DTM PS connection reallocation caused by PCU quality control

When the PCU requests an inter-cell handover for a DTM PS connection because of

quality reasons, CS connection control searches for another DTM-capable cell in which

the DTM call can be re-established. CS connection control performs a handover for a

DTM CS connection when Equation 1 is true.

A PBGT handover back to the source cell is allowed for the same call after a guard time

of 255 seconds.

Inter-cell handover from a non-DTM-capable cell to a DTM-capable cell

When a DTM-capable MS has a CS call in a non-DTM-capable cell, CS connection

control can move the call to a DTM-capable cell to provide the DTM service. CS connec-

tion control performs a handover for a CS connection when Equation 2 is true.

EQUATION 2

AV_RXLEV_NCELL(n) > RxLevMinCell(n) + MAX(0, Pa)

AND

HoMarginPBGT(n) > PBGT(n) > dtmPowerBudgetMargin(n)

where

Pa = (MsTxPwrMaxGSM(ADJ)(n) - P) or (MsTxPwrMaxGSM1x00(ADJ)(n) - P)

P = Maximum power of an MS

When the handover is a BSC internal inter-cell handover, a PBGT handover back to the

source cell is allowed for the same CS connection when both the PBGT handover

equation (for details on the PBGT handover equation, see chapter Target cell evaluation

according to radio criteria in RF Power Control and Handover Algorithm) and Equation

3 (reversed PBGT handover equation) are true. The reversed PBGT handover equation

prevents consecutive PBGT handovers between the source cell and the serving cell.

EQUATION 3 (reversed PBGT handover equation)

PBGT(SERV_CELL) < dtmPowerBudgetMargin(SERV_CELL) - 2dB

where

PBGT(SERV_CELL) = (A - AV_RXLEV_NCELL(SOURCE_CELL)) -

(B - AV_RXLEV_DL_HO - (BsTxPwrMax - BS_TX_PWR))

where





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A = MsTxPwrMaxGSM(ADJ)(n) or MsTxPwrMaxGSM1x00(ADJ)(n)

B = MsTxPwrMaxGSM(BTS) or MsTxPwrMaxGSM1x00(BTS)

When the handover is an external handover, a PBGT handover back to the source cell

is allowed for the same CS connection after a guard time of 255 seconds.

Inter-cell handover for a DTM CS connection during DTM deactivation

When DTM is deactivated in a cell, CS connection control searches for another DTM-

capable cell in which the DTM call can be re-established. CS connection control

performs a handover for a DTM CS connection when Equation 1 is true.

When the handover is a BSC internal inter-cell handover, a PBGT handover back to the

source cell is allowed for the same CS connection when both the PBGT handover and

Equation 3 are true. For details on the PBGT handover equation, see chapter Target cell

evaluation according to radio criteria in RF Power Control and Handover Algorithm.

When the handover is an external handover, a PBGT handover back to the source cell

is allowed for the same call after a guard time of 255 seconds.If an inter-cell handover cannot be performed for a DTM CS connection, or if the

handover does not succeed, CS connection control releases the DTM call by performing

an intra-cell handover from the PS territory to the CS territory of the cell.

Power budget handover during a DTM call

A PBGT handover for a DTM CS connection is performed as for a normal CS connection

with one exception: the power budget value is evaluated against the NCCR EGPRS PBGT

margin (GPM) or NCCR GPRS PBGT margin (EPM) parameter instead of the Ho

Margin pbgt (PMRG) parameter. The NCCR EGPRS PBGT margin parameter is used

if the DTM MS is EGPRS capable and the NCCR GPRS PBGT margin parameter is

used if the DTM MS is not EGPRS capable. By these parameters it is possible to prior-

itize DTM-capable cells over non-DTM-capable cells, because a higher margin can be

set for non-DTM-capable cells than for DTM-capable cells. Moreover, by these param-

eters it is possible to push the DTM calls to the cells that provide GPRS/EGPRS capacity

(for example the coverage layer) while keeping the normal CS calls in the cells with

minimum GPRS/EDGE capacity (for example the capacity layer).

8.3 External handover

In an external handover, an MS with an ongoing connection moves to another cell so

that the BSC changes. When an external handover is triggered, the source BSC sends

a HANDOVER REQUIRED message to the MSC. The message contains the information

element (IE) Old BSS to New BSS information that is used to pass field elements fromthe old BSS to the new BSS. For a DTM-capable MS that has or is requesting a DTM

allocation, the Old BSS to New BSS information IE contains a Dual Transfer Mode infor-

mation field.

During the external handover procedure, CS connection control performs the handover

for the CS connection as normal and releases the DTM allocation in the source cell.

After the handover has been completed (that is, when the target cell has received the

HANDOVER COMPLETE message), CS connection control sends a DTM INFORMATION

message to the MS on the main DCCH if the new cell supports DTM and the MS had or

requested a DTM call in the old cell.

Old BSS to new BSS IE is an optional element in the HANDOVER REQUEST message.

The MSC sends this message to the target BSC. If the MSC does not support delivering



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the IE to target BSC, the DTM INFORMATION message is not sent to the MS and the

MS has to read the DTM capability of the target cell from the system information broad-

cast in the cell before the MS can request the new DTM connection. This causes a pro-

longed interruption time in the DTM connection during the external handover.

8.4 Inter-system handover

In an inter-system handover, an MS connection is transferred from the GSM system to

the wideband code division multiple access (WCDMA) system.

For more information on inter-system handover, see BSS10101 and BSS11107: GSM-

WCDMA Interworking .

DTM-capable MSS

When an inter-system handover is triggered for a DTM-capable MS, CS connection

control performs the handover for the CS connection as usual. If the MS had an ongoing

DTM call, CS connection control releases the DTM allocation in the source cell.

The SGSN may include the Service UTRAN CCO IE in the BSSGP DL UNITDATA PDU

or the CREATE BSS PFC PDU messages to control the inter-system handover proce-

dure. The Service UTRAN CCO IE indicates whether an inter-system handover should

be performed.

The Service UTRAN CCO IE contains service priority information. If the value of the

WCDMA FDD NCCR enabled parameter is Y (that is, the inter-system network-con-

trolled cell re-selection (IS-NCCR) procedures are enabled in the BSC) and the DTM-

capable MS has a CS connection, the PCU sends the received Service UTRAN CCO

information to CS connection control. If the value of the WCDMA FDD NCCR enabled

parameter is N and the DTM-capable MS has a CS connection, the PCU ignores the

received Service UTRAN CCO information. If the DTM-capable MS does not have a CS

connection, normal ISNCCR is performed.

In addition to the service priority information received from the SGSN, CS connection

control receives priority information from the MSC. This means that CS connection

control can receive conflicting service handover recommendations from the SGSN and

the MSC. Therefore, CS connection control applies the following rules to inter-system

handovers:

1. If the Service Handover IE received from the MSC states that CS connection control

must not perform an inter-system handover for the MS, CS connection control does

not initiate an inter-system handover for the MS in question.

2.

If the MSC does not forbid an inter-system handover for the MS, CS connectioncontrol bases the inter-system handover decision on the service priority information

received from the SGSN.

3. If CS connection control has not received any service priority information from the

SGSN, it bases all inter-system handover decisions on the information included in

the Service Handover IE it received from the MSC.

4. If neither the SGSN nor the MSC has sent any service priority information to CS con-

nection control or if CS connection control did not recognize the received informa-

tion, CS connection control performs an inter-system handover as usual, based on

load and signal level thresholds.

For more information on inter-system handover, see BSS10101 and BSS11107:

GSM-WCDMA Interworking .

Non-DTM-capable MSS









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CS connection control initiates an inter-system handover to a non-DTM-capable MS as

soon as at least one WCDMA radio access network (RAN) cell is available and the fol-

lowing conditions are met:

• The MS supports WCDMA.• The MS has a normal CS call.

• The value of the ISHO_SUPPORT_IN_BSCparameter is TRUE.

• The value of the ISHO preferred for non-DTM MS parameter is TRUE.

Note that when the value of the ISHO preferred for non-DTM MS parameter

is FALSE, normal inter-system handover (ISHO) is performed. When the value is

TRUE, the non-DTM-capable MS is moved to an available WCDMA cell as soon as

possible. If the value of the ISHO_SUPPORT_IN_BSC parameter is FALSE, ISHO is

not triggered regardless of the value of the ISHO preferred for non-DTM MS

parameter.





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BSS20088: Dual Transfer Mode Dual Transfer Mode call release

Id:0900d80580590b24

9 Dual Transfer Mode call release A Dual Transfer Mode (DTM) call is released when an inter-cell handover is performed

for the circuit-switched (CS) connection or when either a CS or packet-switched (PS)

connection is released. Both the PCU and the CS connection control in the BSC (CS

connection control) can initiate a DTM call release.

PCU-initiated DTM call release

The PCU releases the PS resources allocated for the DTM call and informs CS connec-

tion control that the mobile station (MS) has returned to dedicated mode. CS connection

control then initiates an intra-cell handover to move the CS connection to the CS terri-

tory.

The PCU informs CS connection control as soon as the temporary block flows (TBFs)

have been released. The PCU applies similar TBF release delay procedures to DTM

TBFs that are used to normal TBFs. You can adjust the length of the DTM TBF release

delays with the following DTM-specific PRFILE parameters:

DL_DTM_TBF_REL_DELAY , UL_DTM_TBF_REL_DELAY , and

UL_DTM_TBF_RELDELAY_EXT.

CS-connection-control-initiated DTM call release

CS connection control initiates a DTM call release when the CS call is released or when

an inter-cell handover is performed for the MS. In a CS-connection-control-initiated DTM

call release, CS connection control informs the PCU that the DTM call needs to be

released. The PCU then releases the PS resources allocated for the DTM call. If the

DTM call is released because of a CS call release, the MS returns to packet idle mode.

After this, the PS connection can be re-established in normal GPRS/EDGE mode if the

MS or the PCU has more data packets to send. Note that the PCU is unable to re-estab-lish the PS connection in normal mode until CS connection control releases the DTM-

CS resource reservation. If the DTM call is released because of an inter-cell handover,

the MS moves to a new cell and performs a cell update or routing area update procedure

if the new cell is DTM-capable. After this, the PS connection can be re-established in

dual transfer mode if the MS or the PCU has more data packets to send.





BSS20088: Dual Transfer ModeImplementing Dual Transfer Mode overview

10 Implementing Dual Transfer Mode overview

Steps

1 Activate IMSI delivery in the MSC.

In a Nokia Siemens Networks MSC, international mobile subscriber identity (IMSI)

delivery is active when the value of the COMMON ID INFORMATION SUPPORTED

BSSAP parameter is YES.

For more information, see Base Station Controller Handling in MSC in Nokia Siemens

Networks MSC/HLR Product Documentation.

2 Check the value of the BSS TO BSS INFO SUPPORTED parameter in the MSC.

The BSS TO BSS INFO SUPPORTED parameter specifies whether the transparent

passing of information from an old BSS to a new BSS via the MSC is supported. The

value of the parameter must be YES.

For more information, see section External handover and Base Station Controller

Handling in MSC in Nokia Siemens Networks MSC/HLR Product Documentation.

3 Activate DTM in the BSC.

For detailed activation steps, see Activating and Testing BSS20088: Dual Transfer

Mode.



Documents

DTM Overview