44383099-2G-3G-handover-Ed02

2G-3G Handover

Date Page PSS-TI/GSM Engineering 6/28/2007 1

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2G-3G HANDOVER FIRST OFF

2G-3G Handover



DOCUMENT HISTORY

Version Author(s) Object

1.0 Sherif Abdel Wahab Ervin Farkas

Initial veriosn .

2.0 Sherif Abdel Wahab Ervin Farkas

Results included .

EXECUTIVE SUMMARY

This document describes the 2G-3G Handover feature First Off carried out in Excelcomindo Network. We start by an overview description of Inter-RAT telecommunication procedures including idle mode and dedicated mode procedures. Then we emphasis with a detailed description of the 2G-3G Handover mechanism. A test plan has been developed to show the telecom gain that can be achieved by employing the 2G-3G Handover in heterogeneous networks. This test plan involves both unitary and statistical tests that we explain with initial expectations of telecom gains as well as observations from field. Finally we enumerate recommended parameter settings to be employed on first application of the 2G-3G IOT features, and describes fine tuning strategies.

2G-3G Handover



TABLE OF CONTENTS

2G-3G HANDOVER FIRST OFF ................................................................................................................1

document History ......................................................................................................................................2

Executive Summary ..................................................................................................................................2

Intoduction .................................................................................................................................................5

Feature describtion ...................................................................................................................................7

PRINCIPLE............................................................................................................................................. 7

GAIN .................................................................................................................................................. 7

ALGORITHM ......................................................................................................................................... 7

Classmark Handling ............................................................................................................................. 7

System and Measurement Information ................................................................................................. 8

Cell Reference .................................................................................................................................... 12

Building Neighbor Cells List................................................................................................................ 12

Measurement processing and reporting ............................................................................................. 13

2G to 3G HO Preparation ................................................................................................................. 15

2G to 3G HO Management............................................................................................................... 15

2G to 3G HO Execution..................................................................................................................... 16

PERFORMANCE MANAGEMENT ............................................................................................................... 18

PM Counters....................................................................................................................................... 18

RNO indicators .................................................................................................................................. 19

PARAMETERS ....................................................................................................................................... 20

EQUIPMENT COMPLIANCE ..................................................................................................................... 21

Test plan description ...............................................................................................................................22

UNITARY TESTS.................................................................................................................................... 22

Sites ................................................................................................................................................... 22

Tools .................................................................................................................................................. 22

Protocol & Planning............................................................................................................................ 22

Parameters Tuned .............................................................................................................................. 23

Performance Management ................................................................................................................. 23

STATISTICAL TESTS................................................................................................................................ 23

Sites ................................................................................................................................................... 23

Tools .................................................................................................................................................. 24

Protocol & Planning............................................................................................................................ 24

Performance Management ................................................................................................................. 25

Results.......................................................................................................................................................26

UNITARY TESTS RESULTS......................................................................................................................... 26

2G-3G Handover



First Drive Test Results ........................................................................................................................ 26

Second Drive Test Results ................................................................................................................... 27

STATISTICAL TESTS RESULTS ................................................................................................................... 29

Initial Status........................................................................................................................................ 29

First Parameters Tuning ...................................................................................................................... 29

A_ECNO_HO Parameter Tuning ........................................................................................................ 30

THR_ECNO_HO Parameter Tuning .................................................................................................... 31

T3121 Parameter Tuning.................................................................................................................... 31

RESP_REQ Parameter Tuning.............................................................................................................. 32

FDD_REPORTING_OFFSET And FDD_REPORTING_THRESHOLD....................................................... 32

QOS EVOLUTION .................................................................................................................................. 33

SDCCH And RTCH Traffic................................................................................................................... 33

SDCCH Assignment Failure ................................................................................................................ 34

RTCH Assignment Failure ................................................................................................................... 35

Incoming Handover............................................................................................................................ 36

Outgoing Handover ........................................................................................................................... 37

Call Setup Success Rate (CSSR) .......................................................................................................... 38

Call Drop Rate (CDR) ......................................................................................................................... 39

Conclusion ................................................................................................................................................40

Appendix I. 2G-3G handover Configuration Recommendation for excelcomindo ......................41

Appendix II. 2G-3G Reselection Configuration Recommendation for excelcomindo ..................43

Appendix III. 3G-2G Reselection and HANDOVEr Configuration Recommendation .................44

2G-3G Handover



INTODUCTION

ALU BSS defines a set of telecommunication procedures, to enable inter-system interoperability. This includes 2G-3G Reselection and 2G-3G Handover. The BSS supports also reselection and Handover from 3G networks. Figure 1 summarizes these Inter-RAT interoperability procedures.

In the following paragraphs we introduce each procedures for consistency of the text flow. Detailed description for 2G-3G Reselection, 3G-2G Reselection, and 3G-2G Handover are not tackled in this document to maintain the main scope which is 2G-3G Handover. However default parameter settings, and configuration recommendations related to Excelcomindo network is elaborated in Appendix I

Appendix I, Appendix II Appendix II, and Appendix III Appendix III .

Figure 1- 2G,3G Interoperability procedures

2G-3G Reselection is employed in idle mode, Packet Idle Mode (PIM) and in Packet Transfer Mode (PTM). In Reselection the network instruct the UE/MS when it is allowed to search for 3G cells. This decision is based on comparison of thresholds against a parameter that is supplied by the BSS in system information messages. Qsearch_I, Qsearch_P, and Qsearch_P_PTM are used in ALU BSS for Idle Mode, PIM, and PTM reselection respectively.

In a next step the UE/MS compares performance measure in serving 2G cells (e.g. Signal Strength) to performance measure of measured 3G cells (e.g. CPICH RSCP). By applying an offset value and taking into account minimum access quantity value in 3G, the UE can reselect a 3G cell, while avoiding ping-

Inter-RAT Interoperability

Telecom Procedures

2G->3G 3G->2G

2G->3G Reselection

2G->3G Handover 3G->2G Hard Handover

3G->2G Reselection

Idle Mode Reselection

PIM Reselection

PTM Reselection

Idle Mode Reselection

Cell_FACH State

2G-3G Handover



pong effects and assuring minimum required service level in 3G. For example the UE/MS reselects a 3G cell in idle mode according to the following criteria:

QoffsetFDDCRLARSCPCPICH

And

QFDDEcNoCPICH

___

min__

+>

>

Where FDD_EcNo is the received Energy per Chip of the primary pilot channel of neighbor 3G cell, CPICH_RSCP is the Received Signal Code Power of the primary pilot channel, FDD_Qmin is the minimum threshold of 3GFDD reselection, RLA_C is the 2G quantity measured by the UE/MS and FDD_Qoffset is an offset applied to RLA_C. Similar analogy to reselection criteria for PIM, and PTM is employed. Besides in GMM ready mode, the network can or can not control the reselection criteria based on NETWORK_CONTROL_ORDER.

In the next section we describe in more details the 2G-3G handover feature. We begin this description by describing operation principle of the feature, and the expected gain from employing it in heterogeneous networks like Excelcomindo. Then we give an in depth explanation of the feature algorithm. This is followed by a enumeration of the related parameters, performance metrics, and equipment compliance.

2G-3G Handover



FEATURE DESCRIBTION

Principle

Before B9MR4, only 3G to 2G Handovers are handled by the BSS. It does not allow to take fully benefit from the 3G layer, because the UE/MS must wait for the end of the call to go back to the 3G layer by performing a 2G to 3G Cell Reselection.

From B9MR4, handover towards UTRAN is supported by threshold triggering on Ec/No (R’99 compliant UE/MS). This HO is possible only from TCH/2G to TCH/3G. The MSC may inform the BSS if preference for specific radio access technology shall be applied.

This cause of HO is identified by the cause 31, and is activated by setting the parameter EN_3G_HO at cell level to the value “enabled”.

Gain

The main expected gain is to take more quickly benefit from the 3G layer in terms of load balancing, and quality of service.

By increasing the load of the 3G layer, resources will be freed on the 2G layer, allowing sparing some capacity investments and offering a better quality to the 2G subscribers.

Algorithm

Classmark Handling

A first information is sent in the SYSTEM INFORMATION TYPE3 message (BSS > MS) to indicate to the UE/MS that the sending of UTRAN and CDMA2000 Classmark Sending messages is controlled by the Early Classmark Sending Control parameter.

On call establishment an UE/MS sends a CLASSMARK CHANGE (MS > BSS) message to the network to inform the network about its radio access capability (e.g. It support GSM, UTRAN FDD,CDMA200,…etc). The BSC stores this information for further possible 2G to 3G HO.

The message UTRAN CLASSMARK CHANGE (MS > BSS) is sent by the MS to the network either on requirement from the BSC (by using the CLASSMARK ENQUIRY message in case of inter BSC handover) or following the CLASSMARK CHANGE previously sent by the MS.

2G-3G Handover



The UTRAN CLASSMARK CHANGE message contains the Inter Radio Access Technology Handover info. This information is transparently sent to the MSC (it provides UTRAN with MS capabilities, for a further handover to UTRAN) in case of handover to 3G or in case of inter-BSC handover to 2G.

System and Measurement Information

System information messages are employed to send to the mobile necessary information required to carry out radio access technology measurement. In the following paragraphs we describe the most important system information measurements employed for 2G-3G Handover purpose. A mere understanding of these messages is required for diagnostics of the feature from drive test traces.

SYSINFO Type 3 (Figure 2Figure 2) is a broadcast message that informs UE/MS(s) about the BSS capabilities in idle mode. For example one can find necessary access information in this message. This message indicates to the UE/MS whether the BSS supports early Classmark sending procedure. Also indication about whether SI2Quater is supported or not by the BSS.

Figure 2 - Example of SYSINFO Type3 Message

SYSINFO 2Quater (Figure 3Figure 3) is employed to broadcast to the UE/MS(s) with necessary information to perform measurements on the 3G layer. We can find 2G-3G reselection parameter like Qsearch_I in this message. Also FDD_ARFCN to be monitored by the mobile during idle mode is broadcasted in this message. Finally this message contains Qsearch_C_Initial (Always set to Zero). Qsearch_C_Initial is used instead of Qsearch_C until the mobile is able to acquire value of Qsearch_C from MEASUREMENT INFORMATION message.

2G-3G Handover



Figure 3-Example Of SYSINFO Type SI2Quater

Figure 4Figure 4 Shows an example of System information exchange in idle and dedicated modes.

The message MEASUREMENT INFORMATION (Figure 5Figure 5) is sent in dedicated mode on the SAACH in the following cases:

o If the 2G to 3G handover is enabled for the considered serving 2G cell. o If the MS is a dual mode MS (2G/3G) o If the MSC did not inhibit 2G to 3G handover for that call

One or two instances of this message are necessary to transmit the whole set of information to the MS.

� 3G_BA_IND: “3G sequence number”, used to identify one set of 3G cells information given to the MS. It is reported by the MS as 3G_BA_USED. It is independent from BA_IND and BA_USED already existing for 2G.

� MI_COUNT : Number of MEASUREMENT INFORMATION instances

� MI_INDEX : Number of the current instance of the MEASUREMENT INFORMATION

� Report Type : This information is set to “The MS shall use the MEASUREMENT REPORT message for reporting”

2G-3G Handover



Figure 4 - System and Measurement Information

� 3G Neighbor Cells Description: This element gives to the MS the 3G neighbor cells (up to 8)

� UARFCN (up to 3) : This element contains several sub-elements :

❏ FDDindic0

❏ NR_OF_FDD_CELLS

❏ FDD_CELL_INFORMATION (scrambling code, diversity)

The sending order defines indexes for sorting the 3G cells in the list, used back by the MS when reporting 3G measurement results.

� Qsearch_C: Threshold of the received signal level of the serving cell. The MS shall search for 3G cells only if that received signal level (O&M settable parameter) of the serving cell is below or above (according to value set at OMC) the threshold, including never and always.

� 3G_SEARCH_PRIO: Indicates if 3G cells may be searched when BSIC decoding is required (O&M).

� FDD_REP_QUANT : Indicates the reporting quantify for UTRAN FDD cells (Ec/No)

� FDD_MULTIRAT_REPORTING : Indicates the number of the strongest 3G cells to be reported by the MS in the MEASUREMENT REPORT message (O&M)

� FDD_REPORTING_OFFSET : Indicates the offset that the MS shall apply to 3G measurements before reporting (O&M)

� FDD_REPORTING_THRESHOLD: Indicates the threshold above which the MS shall report the 3G measurements, including never and always. (O&M).

Idle Mode

Dedicated mode

2G-3G Handover



Figure 5-MESUREMENT INFORMATION Example

2G-3G Handover



Cell Reference

The following table lists how 3G cells are identified in the BSS. Analogy can be made to 2G, for readers with less 3G background.

Table 1 - Cell Reference

The parameter CGI_3G_REQD is used to determine the format of 3G cell identification towards the MSC (depends on MSC type)

If CGI_3G_REQD = 1 then 3G cell will be identified on A interface with “Cell Global Identifier” else with “Partial Identifier”.

Building Neighbor Cells List

The global neighbor cell list (containing 2G & 3G cells) is built from the both 2G and 3G neighbor cells lists. The following tables list the respective limitations and specifications for each part:

Building of GSM neighbor cells list

Table 2 - GSM Neighbor Cell List

2G-3G Handover



Building of UMTS neighbor cells list

Table 3 - UMTS Neighbor Cell List

Building of global neighbor cells list

Table 4 - Global Neighbor Cell List

Measurement processing and reporting

CPICH Ec/No: Received energy per chip divided by the power density in the band measured for the primary pilot channel (CPICH). The reference point for the CPICH Ec/No shall be the antenna connector or the UE. The UE/MS measures CPICH Ec/NO for each adjacency 3G cell indicated in the MEASUREMENT INFORMATION message.

If TX Diversity is applied on the primary CPICH, the received energy by chip (Ec) from each antenna shall be separately measured and summed together in Ws to a total received chip energy per chip on the primary CPICH before calculating the Ec/No. The parameter EN_3G_DIVERSITY(n) indicates if the diversity is applied in the 3G cell, and as a consequence, if the EC/No measurement method shall be adapted. Figure 5 shows how this reflects definition of the 3G adjacencies in MEASUERMENT INFORMATION message.

Qsearch_C controls when the UE/MS should perform measurements for 3G adjacencies. By default this parameter is set to “Always search for 3G neighbors”. However appropriate setting of this parameter could reduce number of reporting, and could also reflect operator 3G deployment strategies. Figure 6 and Figure 7 shows two examples of strategies achieved by proper settings of Qsearch_C.

In Figure 6 Qsearch_C is set to 4 so that UTRAN measurement is triggered if GSM signal strength is below -82 dBm. Such scenario is preferable in case 3G cells are supposed to extend GSM coverage. In this case, It becomes reasonable to set Qsearch_C in 0 to 6, as cell reselection and handover becomes necessary only in shortage of GSM coverage. Figure 7 Shows another scenario where Qsearch_C is set to 10 ,so that UTRAN measurements is performed if GSM signal strength is above -70dBm. Such scenario is

2G-3G Handover



preferable in case 3G sites are co-located with 2G sites. This is because in this case the GSM signal strength will be almost always high compared to 3G cells. Hence it makes no sense just to wait until the GSM signal strength is degraded, as 3G signal won’t be good anyway. Recommended setting is “Always search for 3G neighbors”.

Figure 6-Qsearch C=4. UTRAN measurements performed when

Figure 7-Qsearch C=10. UTRAN measurements performed when

For 3G cells, as the 2G to 3G Handover does not care of 3G cell load, only the better 3G cells are taken

2G-3G Handover



into account. The MS can include a 3G cell in the measurement report if (Quantities compared by coded value):

THRESHOLDREPORTINGFDDOFFSETREPORTINGFDDEcNoCPICH _____ ≥+

Measured Ec/No on FDD UTRAN is the average of the measured samples taken over the reporting period which is the duration of one SAACH (480ms). Then at the BSC, The reported Ec/No on UTRAN FDD neighbor cells are averaged using a sliding arithmetic window on a given window length (settable parameter A_ECNO_HO).

2G to 3G HO Preparation

When a new measurement report is reported by the MS, the process re-evaluates the CPICH Ec/No for all 3G cells measurements reported.

For each cellλ, if AV_ECNO(λλλλ) ≥≥≥≥ THR_ECNO, the cell λ shall be added in the list of candidate cells ranked according to AV_ECNO(λ) and 3G cells are systematically placed on top of the list.

The 3G cell having the highest AV_ECNO(λλλλ) is marked as candidate cell for handover. Figure 8 illustrates 2G-3G Handover preparation process.

Figure 8-2G->3G Handover Preparation

2G to 3G HO Management

Handover management shall manage two lists of rejected cells, associated to each connection. The first list of cells to which the MS failed to handover: MS_CELL_REJ_LIST, guarded by the timer T_MS_CELL_REJ. While the timer T_MS_CELL_REJ timer runs, the cells which belong to this list can not be selected in subsequent channel change attempts on this connection. If the list is full, the oldest cell is discarded and the new one is stored. The timer is restarted each time a new cell is added to the MS_CELL_REJ_LIST. When this timer expires, MS_CELL_REJ_LIST is emptied. The size of this list is 4.

The other list of cells to which the handover is temporarily impossible (e.g. for congestion): REJ_CELL_LIST This list is guarded by T7. When T7 expires, this list is emptied. The size of this list is 2*N_PREF_CELLS. These lists are also emptied when receiving an exit and clear message from protocols (except in case of T_HO_REQD_LOST expiry in ECC). Emptying of the lists allows the cells to be reselected for a channel change. Furthermore, the ALU BSS assumes that the MSC tries the target cells

2G-3G Handover



in the order given by the BSS. Figure 9 shows the flow-chart for the algorithm used to manage cell rejection.

Figure 9-Algorithm of handling cell rejection

2G to 3G HO Execution

Figure 10-InterSystem Handover execution

1. The BSC sends HANDOVER REQUIRED message to the GSM MSC containing the UTRAN candidate cell.

2. The MSC sends MAP/E message PREPARE HANDOVER to the UMTS CN.

2G-3G Handover



3. The CN sends RANAP message RELOCATION REQUEST to the Target RNC.

4. Response RELOCATION REQUEST ACKNOWLEDGE is returned to the CN by the target RNC via RANAP.

5. MAP/E message PREPARE HANDOVER RESPONSE is sent by the UMTS CN to the MSC.

6. The MSC initiates the handover execution by sending the message HANDOVER COMMAND to the old BSC.

7. The BSC sends the INTER SYSTEM TO UTRAN HANDOVER COMMAND to the UE/MS. The T3121 timer is started.

8. When target RNC has detected the UE, RELOCATION DETECT message is sent to the CN node.

9. When the RRC connection is established with the target RNC and necessary radio resources have been allocated the UE sends RRC message HANDOVER COMPLETE to the target RNC.

10. Once complete the target RNC sends RANAP message RELOCATION COMPLETE to the CN.

11. CN sends MAP/E message SEND END SIGNAL REQUEST to the MSC.

12. The MSC sends CLEAR COMMAND message to the BSC.

13. The BSC responds with CLEAR COMPLETE message to the GSM

14. The MSC sends MAP/E message SEND END SIGNAL RESPONSE to the UMTS CN to conclude the procedure (this message is not sent until the end of the call).

Upon starting the inter-system handover signaling using INTER SYSTEM TO UTRAN HANDOVER COMMAND T3121 timer starts. This timer stops when the mobile correctly seizure a UTRAN channel. Its purpose is to keep the old channels sufficiently long for the MS to be able to return to the old channels, and to release the channels if the MS is lost. High value of this parameter should satisfy this primary purpose, however very high value could result in congestion in 2G side. Default value is 140 (14 seconds).

2G-3G Handover



Performance Management

PM Counters

The following table enumerates the PM Counters:

Table 5 - PM Counters

2G-3G Handover



RNO indicators

Listed in table below the RNO indicators:

Table 6 - RNO Indicators

2G-3G Handover



Parameters

The following table enumerates all feature related parameters. In bold the main parameters tuned during first off tests.

Logical name Definition Min Max Def Unit Instance

CGI_3G_REQD Controls format of 3G cell identifications sent to the MSC.

0 1 1 None BSC

SCRAMBLING_CODE_3G(n) This parameter indicates the Primary Scrambling Code as defined in 3GPP TS 25.213

0 511 -1 None 3G cell

FDD_ARFCN(n) FDD UTRAN frequency 0 3276.6 -1 MHz 3G cell

EN_3G_DIVERSITY(n) This parameter indicates if diversity is applied for the cell

0 1 0 None 3G cell

Qsearch_C Threshold for searching for 3G cells in dedicated mode depending whether the received signal level of the serving cell is below or above the threshold.

-98 -50 7 dBm cell

THR_ECNO_HO Ec/No threshold above which a handover to UTRAN may be triggered

-110

-47 -91 dBm cell

T3121 This timer is started by sending an INTER SYSTEM TO UTRAN HANDOVER message to the MS and is normally stopped when the MS has correctly seized the UTRAN channel(s). Its purpose is to keep the old channels sufficiently long for the MS to be able to return

0 25,5 14 sec BSC

LAC_3G(n) This parameter indicates the Location Area Code as defined in 3GPP TS 24.008. It is used in the HANDOVER COMMAND message

0 65535 -1 None 3G cell

FDD_REPORTING_THRESHOLD Threshold above which the MS shall report the measurements

0 42 0 dB cell

A_ECNO_HO Window size for Ec/No level averages for 2G to 3G handover

1 31 8 Samfr cell

CI_3G(n) This parameter indicates the Cell Identifier of a 3G cell as defined in 3GPP TS 25.401

0 65535 -1 None 3G cell

FDD_MULTIRAT_REPORTING Number of the strongest 3G cells to be reported by the MS in the measurement report message

0 3 2 None cell

FDD_REPORTING_OFFSET Offset that the MS shall apply to measurements before reporting

0 42 0 dB cell

MNC_3G(n) Mobile Network Code of a neighbor 3G cell of the own PLMN or of a foreign PLMN.

0 999 999 None 3G cell

MCC_3G(n) Mobile Country Code of a neighbor 3G cell of the own or of a foreign PLMN.

0 999 999 None 3G cell

EN_3G_HO This flag enables/disables the 2G-3G handover 0 1 0 None cell

RNC_ID(n) This parameter indicates the RNC Identifier as defined in 3GPP TS 25.401. It is used in HO Required message sent to the MSC.

0 4095 -1 None 3G cell

Table 7 - Parameters

2G-3G Handover



Equipment Compliance

� Supported in Evolium, M4M, and M5M BTSs with B9 MR4

� Supported in G2 BSC with B9 MR4

� Compatible with 3GPP Rel’4 fully compliant UTRAN

� Compatible with ALU UTRAN starting from R5 MR3, Nokia UTRAN since RAN 1.5, Nortel UTRAN and Huawei UTRAN

2G-3G Handover



TEST PLAN DESCRIPTION

Unitary Tests

Sites

ALU 2G Cell IDs: 30301, 30302, 30291

3G Cell ID: 57735

Tools

TEMS measurement tool + Mobile: Sony-Ericsson Z800

Protocol & Planning

Back to

the 2G layerby 3G to 2G

HO

3G layer

2G layer

Test starton the 2G layer

Mobility towardsthe 3G layer untilthe 2G to 3G handover isperformed.

Back to

the 2G layerby 3G to 2G

HO

3G layer

2G layer

Test starton the 2G layer

Mobility towardsthe 3G layer untilthe 2G to 3G handover isperformed.

Figure 11 - Drive Test Protocol

Test type Nb of loops Parameters setting Expected behaviour foreseen duration

CS drive test 20 Feat. Enabled All 2G to 3G handovers should be performed. 4 hours

Table 8 - Drive Test Planning

This test will allow assessing:

• The 2G-to-3G handover duration compared with 3G-to-2G and 2G-to-2G handovers. • The % of 2G-to-3G HO efficiency

• Ping Pong Effect

2G-3G Handover



Parameters Tuned

Parameter instance unit Test-1 Operational Value

Test-2 Operational Value

Qsearch_C Cell dBm 7 7

THR_ECNO_HO Cell dBm -12 -9

T3121 BSC sec 14 14

A_ECNO_HO Cell Samfr 10 10

FDD_REPORTING_THRESHOLD Cell dB 0 6

FDD_REPORTING_OFFSET Cell dB 0 18

Table 9 – Parameters Tuned for Drive Test


2G to 3G HO Performances will be assessed based on following events observed during drive test:

• Number of requested 2G3G HO • Number of attempted 2G3G HO

• Number of preparation fails • Number of successfully 2G3G HO

• Number of ROC observed • % of efficiency rate and % of success rate • Average, min. and max. 2G-to-3G handover duration compared with 3G-to-2G and 2G-to-2G

handovers

Statistical Tests

There is no reference available to the performance of the 2G to 3G HO performance for old Huawei cells (feature was available in Huawei solution but without KPIs commitment from their side).

Sites

• Site: Medan, Indonesia

• Operator: Excelcomindo

• 2G Network: Alcatel-Lucent:

o 742 cells

o connected to 2 legacy BSC and one legacy MFS.

o Pilot defined on 28 cells listed in the following table

BSC LAC CI BSC LAC CI BSC LAC CI

2G-3G Handover



2921_Martabe-1 22251 29211 3026_PmtgSintr-3 22252 30263 3032_KABANJAHE-3 22251 30323

2921_Martabe-2 22251 29212 3027_Parapat-1 22251 30271 3035_Motung-1 22251 30351

2921_Martabe-3 22251 29213 3027_Parapat-2 22251 30272 3035_Motung-2 22251 30352

2976_Sembahe-1 22251 29761 3027_Parapat-3 22251 30273 C057_JuharKaro-7 22251 30577

2976_Sembahe-2 22251 29762 3029_SIBOLANGIT-2 22251 30292 C068_SutomoSiantar-7 22252 30687

2977_KpBntanSn-1 22252 29771 3030_BANDARBARU-1 22251 30301 C068_SutomoSiantar-9 22252 30689

2977_KpBntanSn-2 22252 29772 3030_BANDARBARU-2 22251 30302 3093_TukTuk-1 22251 30931

2977_KpBntanSn-3 22252 29773 3032_KABANJAHE-1 22251 30321 3093_TukTuk-2 22251 30932

3026_PmtgSintr-1 22252 30261 3032_KABANJAHE-2 22251 30322 3093_TukTuk-3 22251 30933

3026_PmtgSintr-2 22252 30262

Table 10 - Cells Used for Statistical Tests

• 3G Network: Huawei: 276 3G external cells defined in OMC-R.

• Core Network: Ericsson

Tools

Alcatel-Lucent A9156-RNO

Protocol & Planning1

The aim of this test is to study QoS evolution, in response to feature parameter setting change. The main goal is to find parameter setting optimization methodology that achieve the gain of the feature, by Handover Multi-Rat Mobiles to 3G whenever possible while preserving Network Quality and stability. Network Quality is preserved by avoiding excessive Call drops or voice interruption. And network stability is preserved by maintaining Signaling load at nominal values and reduce ping-pong effects.

Phase 1. Enable the feature with default ALU parameters. For the pilot cells the following parameters are to be applied.

1 As the feature was rapidly activated before the tests start date, these tests are not carried out in the sequence shown.

2G-3G Handover



Parameter Instance unit Value

Qsearch_C Cell dBm 72

THR_ECNO_HO Cell dBm -15

T3121 BSC sec 14

A_ECNO_HO Cell Samfr 8

FDD_REPORTING_OFFSET Cell dB 0

FDD_REPORTING_THRESHOLD Cell dB 0

Table 11 - Phase 1 Parameters Values

Phase 2. Study the effect of each parameter on 2G, and 3G QoS by tuning each value such that:

� Study effect of Qsearch_C set to a higher value (e.g. -70 above)

� Study effect of Qsearch_C set to a lower value (e.g. -70 below): It is not possible to be tested in Excelcomindo as all 3G cells are collocated with 2G cells

� Study effect of Setting THR_ECNO_HO to 0 “Attempt HO to 3G whatever value EcNo”

� Study effect of Setting THR_ECNO_HO to an optimized value (e.g. -12, -9 dBm)

� Study effect of Setting A_ECNO_HO to a higher value (e.g. 10)

� Study effect of Setting A_ECNO_HO to a lower value (e.g. 4)

� Study effect of Setting FDD_REPORTING_{THRESHOLD,OFFSET} to a higher value (e.g. 6,18)

Phase 4. Final Parameter Fine tuning session and QoS follow-up.


The following RNO reports are used to asses the Feature performance in response to each phase in the previous section3:

2G-3G Handover Procedure Performance:

KPI evolution:

Traffic Evolution:

General Handover Pattern Evolution:

2 Qsearch_C=7 is equivalent to “Always search for 3G cell”.

3 Due to unavailability of 3G statistics in correspondence to parameter changes, only 2G statistics are taken into account

2G-3G Handover



RESULTS

Unitary tests results

First Drive Test Results

20 loops of drive test were performed in order to check 2G3G HO, 2G2G HO and 3G2G HO (for a set of 2G cells - 30301, 30302, 30291 - and 3G cell 57735) for a period of 8 hours. Following number of Handovers were observed:

• 2G3G HO = 20,

• 3G2G HO = 14,

• 2G2G HO = 46

During this drive test no handover failure was observed for either 2G or 3G side. Also there was no ROC observed in 2G side.

In the figure below an overview of HO duration is presented. The duration was computed as time difference between HO command and HO complete messages.

Related to HO duration, from the figure can be observed almost same performance for 3G2G HO and 2G3G HO. Also to be noticed that the maximum duration is around 250 ms, duration which does not impact end user perception. In order to measure exactly effect of this interruption on voice quality, a voice quality assessment audit can be organized. Such an audit was not possible during this First off due to unavailability of a voice quality measurement tool.

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

2G-2G HO 2G-3G HO 3G-2G HO

Average

Maximum

StdDiv

Figure 12 - First Drive Test HO Duration

For the 2G-2G HO there was only one case with duration over 300ms (see max value in graph above). But can be noticed that duration of 2G-2G HO has a standard deviation greater than 2G-3G or 3G-2G, which means that the values are spread between minimum and maximum values. For 2G-3G HO and 3G-2G HO the standard deviation is lower which means that HO durations are concise around the average value.

During 8 hours drive test there were 8 calls dropped from which 7 in 3G due to un-optimized 3G2G HO management and one in 2G due to radio conditions. In the figure below can be observed the evolution of RSCP and ECNO levels on 3G side and also evolution of measured RxLev on 2G side (finally a call drop

2G-3G Handover



occurred even if 2G cell with good level was reported – no emergency HO required on 3G side).

UMTS Measurements

-120

-110

-100

-90

-80

-70

-60

-50

-40

0 . 0 ,000 .4 ,000 .8 ,000 .11 ,000 .15 ,000 .19 ,000 .22 ,000 .26 ,000 .30 ,040 .34 ,060 .38 ,000 .42 ,000 .46 ,000 .50 , 040 .54 ,000 .58 ,001 .1 ,001 .4 ,871 . 7 ,00

1 .11 ,041 .11 ,30

Time [ms]

[dB

m]

-25

-20

-15

-10

-5

0

[dB

]

CPICH_RSCP [dBm]

GSM RxLev [dBm]

CPICH_EcNo [dB]

Compressed ModeCall Drop

Figure 13 - UMTS Measurements Before Call Drop

Second Drive Test Results

Initially in the Excelcomindo network the 3G to 2G HO was not working due to outdated adjacencies relations to the new ALU 2G cells. For the first drive test only for one cell the relations were updated in order to allow the loop test.

Starting with 14th of June all adjacencies were updated and the 3G to 2G HO start to impact the performances observed for 2G to 3G HO (preparation failed rate increased, due to increased number of required HO). In order to check if there is a ping pong present between 2G cells and 3G cells a second drive test was performed on the 2G cell 30323 and 3G cell 57746.

The table below is showing Handover event times during this drive test. It can be observed that in less than 1 minute there are 3 HO commands To and From UTRAN.

12:45:10.93 Handover From UTRAN Command-GSM (DL-DCCH) 12:45:23.15 Inter-System To UTRAN Handover Command 12:45:23.39 Handover To UTRAN Complete (UL-DCCH) 12:45:31.81 Handover From UTRAN Command-GSM (DL-DCCH) 12:45:40.26 Inter-System To UTRAN Handover Command 12:45:40.46 Handover To UTRAN Complete (UL-DCCH) 12:45:48.78 Handover From UTRAN Command-GSM (DL-DCCH)

Table 12 - TO/FROM UTRAN Handover Commands

By analyzing both measurement reports in UTRAN and BSS we observed that 3G-2G Handover is based on CPICH_RSCP Quantity4. We observed also that at Handover decision instances the value of CPICH Ec/No fall in the interval from -7.5 dB and -12 dB (Table 13). As the EC/NO threshold used for 2G-3G Handover was -12 dB it is clear that there will be a ping-pong between 2G and 3G cells.

4 The only way to analyze 3G behavior is by inspecting a drive test measurement as such information was not accessible by the First off team.

2G-3G Handover



As increasing the threshold on 2G side has big impact on number of required HO, also that on 3G side the CPICH EC/NO and RSCP are still at good level when the decision for 3G2G HO is taken, the solution is only adjusting the threshold on 3G side (see “Conclusion” chapter for more recommendations on this topic).

Time Message Type-

All-AS CPICH Ec/No[dB]

All-AS CPICH RSCP[dBm]

12:38:20.46 Handover From UTRAN Command-GSM (DL-DCCH) -12.5 -102. 12:41:17.89 Handover From UTRAN Command-GSM (DL-DCCH) -10. -97. 12:41:45.50 Handover From UTRAN Command-GSM (DL-DCCH) -14. -102. 12:42:09.17 Handover From UTRAN Command-GSM (DL-DCCH) -9. -95. 12:43:44.59 Handover From UTRAN Command-GSM (DL-DCCH) -10. -99. 12:44:26.70 Handover From UTRAN Command-GSM (DL-DCCH) -7.5 -94. 12:44:51.93 Handover From UTRAN Command-GSM (DL-DCCH) -7. -93. 12:45:10.93 Handover From UTRAN Command-GSM (DL-DCCH) -9.5 -96. 12:45:31.81 Handover From UTRAN Command-GSM (DL-DCCH) -8. -93. 12:45:48.78 Handover From UTRAN Command-GSM (DL-DCCH) -11. -98. 12:46:40.59 Handover From UTRAN Command-GSM (DL-DCCH) -11.5 -102. 12:47:53.17 Handover From UTRAN Command-GSM (DL-DCCH) -9.5 -97. 12:49:38.17 Handover From UTRAN Command-GSM (DL-DCCH) -8.5 -97.

Table 13 - CPICH EC/NO and RSCP Level for 3G2G HO Commands

2G-3G Handover



Statistical Tests Results

Initial Status

In the figure below is presented the initial status (05 June) of 2G-3G HO for the cells used for statistical tests. From the figure, it’s clear that very few cells in the network experience 2G-3G Handover , given that the feature was enabled on 40 cells.

Outgoing HO 2G 3G

0

50

100

150

200

2921_M

art

2948_M

art

2976_S

em

2977_K

pB

3025_T

ebi

3026_P

mtg

3027_P

ara

3030_B

AN

3032_K

AB

3039_S

eiR

3093_T

ukT

3098_T

bTg

C057_J

uha

020406080100120

drop bss

drop radio

success

prep fail

% success rate

% effic rate

Figure 14-MultiCell report from 5th of June

Below an overall view of the 2G-3G HO status in 05 June 2007:

• Number of required HO: 355

• Number of attempted HO: 319

• Success rate: 60.28%

• Preparation fail rate: 10.14%

• Drop rate: 32.92%

First Parameters Tuning

A first action done was to change the Qsearch_C and THR_ECNO_HO values as follows:

• For the cells with low number of 2G3G HO required it was changed only Qsearch_C from the value -70(above) to “Always Search for 3G Cells”

• For cells where number of requests was higher we changed Qsearch_C from the value -70(above) to “Always Search for 3G Cells” and THR_ECNO_HO from 0 to -15 [dB]

In the figure below can be observed the impact of changes to the 28 cells under observation:

2G-3G Handover



Figure 15 - 2G3G HO Evolution after Qsearch_C Changed

For the cells on which only Qsearch_C was changed the number of required HO increased by 57.6% and on cells where also THR_ECNO_HO was changed number of required HO increased by 49.9%.

Changing the values for parameters Qsearch_C and THR_ECNO_HO had no impact on numbers of required HO for the cells with 0 required. This problem could be to not correct declaration of 3G adjacencies (incorrect scrambling code defined).

A_ECNO_HO Parameter Tuning

A_ECNO_HO represent the window size for Ec/No level averages for 2G to 3G handover.

One of the first observation done on the 28 cells used for the 2G to 3G HO validation tests was that for some cells the number of required HO is very low (even 0 for some cells).

In order to improve the number of required HO the averaging window was reduced in order to allow a more quick decision for HO request. From the figure below can be noticed that the parameter tuning does not has the expected impact on number of 2G to 3G HO required.

Outgoing HO 2G 3G

0

5

10

15

20

06/06/2007 06/07/2007 06/08/2007 06/09/2007 06/10/2007 06/11/2007 06/12/2007 06/13/2007

0

20

40

60

80

100

120

drop bss

drop radio

success

prep fail

% success rate

% effic rate

•A_ECNO_HO = 8 •A_ECNO_HO = 4

•A_ECNO_HO = 10

THR_ECNO_HO = -12

Figure 16 - Impact of Decreased A_ECNO_HO

Also in next graph can be observed that also increasing the averaging window doesn't decrease the number of requests.

Outgoing HO 2G 3G

0

100

200

300

400

500

600

700

06/01/2007 06/02/2007 06/03/2007 06/04/2007 06/05/2007 06/06/20070

10

20

30

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50

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70

80

drop bss

drop radio

success

prep fail

% success rate

% effic rate

Qsearch_C = -70(above) Qsearch_C = Always Search for 3g

2G-3G Handover



Figure 17 - Impact of Increased A_ECNO_HO

We propose for this parameter the value 10 (default value proposed by ALU is 8) as it increase success and efficiency rate for 2G to 3G HO without to reduce the number of required HO. This increase in success and efficiency rate was due to the fact that by setting A_ECNO_HO to a higher value, fast fluctuation in the radio link are compensated in the averaging process, and handover decision is only performed for the stable radio conditions.

THR_ECNO_HO Parameter Tuning

THR_ECNO_HO parameter defines the Ec/No threshold above which a handover to UTRAN may be triggered.

In order to increase the quality of 2G to 3G HO an increased value of the threshold for 2G to 3G HO decision was used. Can be observed on the figure below that increasing the threshold with 3 dB the success rate was increased by 66%. In combination with the average window size of 10 it brings a very good quality to 2G to 3G HO. A significant improvement in Radio drop was observed as it reduced to more than 25% of its value before the parameter tuning. This directly improved Handover efficiency rate.

Outgoing HO 2G 3G

0

20

40

60

80

100

120

140

160

180

06/06/2007 06/07/2007 06/08/2007 06/09/2007 06/10/2007 06/11/2007 06/12/2007 06/13/20070

10

20

30

40

50

60

70

80

90

100

drop bss

drop radio

success

prep fail

% success rate

% effic rate

•THR_ECNO_HO = -15 •THR_ECNO_HO = -12

•A_ECNO_HO = 10

THR_ECNO_HO = -12

Figure 18 - THR_ECNO_HO Impact

T3121 Parameter Tuning

This timer is started by sending an INTER SYSTEM TO UTRAN HANDOVER message to the MS and is

Outgoing HO 2G 3G

0

50

100

150

200

250

06/06/2007 06/07/2007 06/08/2007 06/09/2007 06/10/2007 06/11/2007 06/12/2007 06/13/2007

0

10

20

30

40

50

60

70

80

90

drop bss

drop radio

success

prep fail

% success rate

% effic rate

•A_ECNO_HO = 8 •A_ECNO_HO = 10 •A_ECNO_HO = 10 THR_ECNO_HO =-12

2G-3G Handover



normally stopped when the MS has correctly seized the UTRAN channel(s). Its purpose is to keep the old channels sufficiently long for the MS to be able to return to the old channels, and to release the channels if the MS is lost.

In order to allow the mobile to return to 2G resources if the HO to 3G is not possible one solution tested was to increase the timer T3121. From the figure below can be noticed that T3121 has no impact on the ROC.

HO_Out_MSC_2G_3G_ROC (HOOMOCUN)

0

1

2

3

4

5

6

7

8

9

01 /06 /20

07

02 /06 /20

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03 /06 /20

07

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07

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07

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07

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07

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13 /06 /20

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07

16 /06 /20

07

17 /06 /20

07

HO_Out_MSC_2G_3G_ROC (HOOMOCUN) T3121 = 1.4s T3121 = 14 sT3121 = 2s

Figure 19 - 2G-3G HO ROC

RESP_REQ Parameter Tuning

This flag controls “Response request” OIE inclusion in HANDOVER REQUIRED. If this parameter is not “Enabled”, due to the fact that HANDOVER REQUIRED messages are not included in IE , so not received by BSC, the counter MC924G (2G 3G HO Preparation Failed) is not incremented. Thus enabling this parameter was necessary during this first off in order to assess explicit Handover rejection from 3G/Core side by.

Alcatel-Lucent recommends to set RESP_REQ to 1 if EN_EXT_DR is set to “Enabled” in order to get a Handover Reject message from the MSC in case all target cells are congested and thus to attempt other procedures.

FDD_REPORTING_OFFSET And FDD_REPORTING_THRESHOLD

FDD_REPORTING_OFFSET represents an offset that the MS shall apply to measurements before reporting.

FDD_REPORTING_THRESHOLD represents the threshold above which the MS shall report the measurements.

In order to check the impact of these parameters we changed the values for some cells where increased number of preparation failed was observed (due to ping pong with 3G network). The aim of this parameter tuning is to let the mobile report only CPICH EcNo values above -12 dB, and hence taking handover decision towards a non-degraded, non-congested 3G cell.

Tested values are:

• FDD_REPORINTING_OFFSET = 18 (default is 0)

• FDD_REPORTING_THR = 6(default is 0)

In the figure below can be observed that there is no impact on preparation failed of these parameters (preparation fail still present).

2G-3G Handover



Outgoing HO 2G 3G

01020304050

06/17/2007

06/17/2007

06/17/2007

06/17/2007

06/17/2007

06/17/2007

06/18/2007

06/18/2007

06/18/2007

06/18/2007

06/18/2007

06/18/2007

06/19/2007

06/19/2007

06/19/2007

06/19/2007

020406080100120

Series4

Series3

Series2

Series1

Series6

Series5

In order to check this behavior also a drive test is planned for this cell.

QoS Evolution

In the following subsections we will demonstrate QoS indicator evolution during the first off Period for the 28 cells under test. In general stable QoS has been observed, and no impact from feature activation nor parameter tuning.

SDCCH And RTCH Traffic

Stable SDCCH traffic, encountered throughout the first off period.

SDCCH traffic

0

100

200

300

400

06 /01 /20

07

06 /03 /20

07

06 /05 /20

07

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07

06 /09 /20

07

06 /11 /20

07

06 /13 /20

07

06 /15 /20

07

06 /17 /20

07

06 /19 /20

07

235240245250255260265270

Erlang total

SDCCH avail avg

Stable RTCH traffic, encountered throughout the first off period.

FDD_REPORTING_OFFSET = 0

FDD_REPORTING_THRESHOLD = 0

FDD_REPORTING_OFFSET = 18

FDD_REPORTING_THRESHOLD = 6

2G-3G Handover



RTCH traffic

0100200

300400500

06 /01 /20

07

06 /03 /20

07

06 /05 /20

07

06 /07 /20

07

06 /09 /20

07

06 /11 /20

07

06 /13 /20

07

06 /15 /20

07

06 /17 /20

07

06 /19 /20

07

250

260

270

280

290

Erlang total

RTCH avail avg

A Interface Traffic

Figures below shows stability of A interface traffic, even with existence with the ping pong effect. It worth noting that this graphs are related to the two BSCs which have the 2G-3G feature activated.

A Traffic

900

950

1000

1050

1100

1150

1200

1250

06 /08 /20

07

06 /09 /20

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06 /10 /20

07

06 /11 /20

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06 /16 /20

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07

06 /18 /20

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Erlang total

A Channel Occupancy

3200000

3400000

3600000

3800000

4000000

4200000

4400000

06 /08 /20

07

06 /09 /20

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06 /10 /20

07

06 /11 /20

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06 /12 /20

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07

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07

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07

06 /20 /20

07

36

37

38

39

40

41

42

43

44

Occupancy

Duration Avg

SDCCH Assignment Failure

Stable SDCCH assignment procedure, throughout the First off period.

2G-3G Handover



SDCCH assignment failure

050000100000

150000200000250000

06 /01 /20

07

06 /03 /20

07

06 /05 /20

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07

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07

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07

012

345

Fail - BSS

Fail - Radio

Success

% Fail

SDCCH Assign Congestion

050000100000150000200000250000

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/20

06

/19

/20

0

0.51

1.52

Congestion

Request

% Congestion

RTCH Assignment Failure

Stable RTCH assignment phase throughout the first off period.

RTCH assign preparation

300003200034000360003800040000

06

/01

/20

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/20

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/20

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/20

0

0.050.10.15

Prep Fail BSS

Congestion

Request

% Prep FailBSS

% Congestion

2G-3G Handover



RTCH assign execution

300003200034000

360003800040000

06 /01 /20

07

06 /03 /20

07

06 /05 /20

07

06 /07 /20

07

06 /09 /20

07

06 /11 /20

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06 /13 /20

07

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07

06 /17 /20

07

06 /19 /20

07

00.050.10.150.20.250.3

Exe Fail BSS

Fail Radio

Success

% Exe Fail BSS

% Fail Radio

Incoming Handover

From the figure below, we observe increase in number of Incoming Inter BSC Handover. This is due to correction of 2G adjacencies definition in 3G side, which also appear in Figure 20.

Incoming Inter BSC handovers

0

500

1000

1500

2000

06 /01 /20

07

06 /03 /20

07

06 /05 /20

07

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07

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07

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07

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07

0

2

4

6

8

Fail - Radio

Fail - BSS

Success

No CIC alloc

Prep Fail

Congestion

% Fail

% Cong

Incoming HO 3G 2G

0

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1000

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2000

06 /01 /20

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07

012

345

Fail BSS

Fail Radio

Success

Prep Fail

% Fail

% Prep Fail

Figure 20

In the figure below it’s clear that 3G-2G Handover dominates 2G-2G handover for this area. All these handover are non-emergency causes, which don’t met operator strategy in Excelcomindo to make the maximum benefit from 3G. Thus a recommendation is highlighted to the operator, to tune 3G-2G handover for emergency causes only.

2G-3G Handover



Incoming HO 3G 2G split

0%20%40%60%80%100%

06 /01 /20

07

06 /03 /20

07

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07

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07

06 /11 /20

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06 /19 /20

07

3G Request

2G Request

Stable Incoming Intra BSC Handover encountered throughout the first off period.

Incoming Intra BSC handovers

0

5000

10000

15000

06 /01 /20

07

06 /03 /20

07

06 /05 /20

07

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07

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06 /13 /20

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07

06 /19 /20

07

0

0.51

1.52

Fail - Radio

Fail - BSS

Success

Prep Fail

Congestion

% Fail

% Cong

Outgoing Handover

Stable outgoing inter BSC Handover encountered throughout the First off period.

Outgoing Inter BSC handovers

050100150200250300

06 /01 /20

07

06 /03 /20

07

06 /05 /20

07

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07

06 /09 /20

07

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07

06 /13 /20

07

06 /15 /20

07

06 /17 /20

07

06 /19 /20

07

024

6810

Drop - Radio

Drop - BSS

ROC

Success

Prep Fail

% Drop

% ROC

Stable outgoing Intra BSC handover encountered during the First off period.

2G-3G Handover



Outgoing Intra BSC handovers

0

5000

10000

15000

06 /01 /20

07

06 /03 /20

07

06 /05 /20

07

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07

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07

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07

06 /19 /20

07

00.51

1.522.5

Drop - Radio

Drop - BSS

ROC

Success

Prep Fail

% Drop

% ROC

The figure below shows evolution of the 2G-3G Handover. From the figure we notice significant improvement in radio drop and efficiency rate after parameter tuning on 15th of June. A High preparation failure is observed after activation of 3g-2G Handover, due to explicit rejection from 3G side as seen by the counter MC924g. This in turn affected success rate, but this should not be interpreted as degradation from 2G side.

Outgoing HO 2G 3G

050010001500200025003000

06 /01 /20

07

06 /03 /20

07

06 /05 /20

07

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020406080100120

drop bss

drop radio

success

prep fail

% successrate

% effic rate

Call Setup Success Rate (CSSR)

Stable CSSR is encountered throughout the period of the First Off.

Call success

0200400

6008001000

06 /01 /20

07

06 /03 /20

07

06 /05 /20

07

06 /07 /20

07

06 /09 /20

07

06 /11 /20

07

06 /13 /20

07

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07

06 /17 /20

07

06 /19 /20

07

97.59898.59999.5100

Call drop

Assign Unsucc

SDCCH drop

% Callsuccess

% Call setup

2G-3G Handover



Call Drop Rate (CDR)

Stable CDR is encountered throughout the period of the first off. This is a strange behaviour, because we have observed improvement in the outgoing 2G-3G Handover Radio drop. The reason for this is that the formula for Call drop HO doesn’t take into account the case for 2G-3G Handover. For this we suggest to change the trigger condition for the counter MC621 to take into account the case of expiry of T3121, without revision to old channel.

A short term solution is to modify the Call_Drop indicator formula to be:

( [MC736] + [MC621] + ( [MC14C] + [MC739]) + [MC921c] + [MC924e] )

Instead of

( [MC736] + [MC621] + ( [MC14C] + [MC739]) + [MC921c])

Call drop

0

100

200

300

400

06 /01 /20

07

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07

06 /19 /20

07

00.20.40.60.811.2

Preemption

Drop - BSSRTC

Drop BSSIntern

Drop - HO

Drop - Radio

% RTCH drop

% Call Drop

One last observation related to RNO is that we were using RNO that parameters related to 2G-3G handover are not present in logical parameter tabs, namely we didn't find these parameters: En_3G_HO,THR_ECNO_HO EN_2G_TO_3G_CELL_RESELECTION, Qsearch_C. CR 32/156152 was issued related to this problem, but was not implemented in B9MR4. Implementation is foreseen in a next release.

2G-3G Handover



CONCLUSION

This document presents First off application of the 2G-3G Handover feature in Excelcomindo network. The feature was tested with Huawei UTAN and Ericsson Core network. After this First off we can conclude the following about the feature:

• The 2G-3G handover feature as implemented in ALU is working well and achieved the main

expected gain, which is taking more quickly benefit from the 3G layer in terms of load balancing, and quality of service.

• The feature can be introduced in other networks.

• Unitary tests showed that call interruption time due to Intersystem handover, is around 190ms, which should not affect end user voice quality. And with simple parameter tuning we can reach high HO efficiency with very low call drop.

• Unitary tests also enabled us to study ping pong phenomena introduced between 2G and 3G due to Intersystem Handover. This ping pong phenomena didn’t cause any network instability (e.g. Congestion or Signaling load). Feedback from other networks will be needed regarding this point.

• We noticed that inconsistent parameter setting in UMTS side result in this ping pong phenomena and the only way to reduce it with current ALU implementation is by joint parameter optimization between 3G to 2G. In Excelcomindo it’s recommended to have 3G-2G Handover based on CPICH EcNo (not on CPICH RSCP) and with enough hysterics introduced.

• A defensive mechanism is needed to be implemented in ALU BSS to prevent such phenomena, also Handover based on CPICH RSCP should be implemented for more tuning flexibility from BSS side.

• Statistical tests enabled us to study impact of all feature parameters on Network statistics

evolution. We showed possibility and methodology to tune different parameters to have high intersystem handover efficiency and low call drop.

• Network QoS indicators were stable during whole first off period. A suggestion on modification of Call drop HO counter triggering condition and Call Drop Indicator formula definition is highlighted.

• Preparation failure due to explicit rejection from 3G side, was noticed after activation of 3G-2G handover widely. This should not be interpreted as degradation, but rather as a defensive mechanism in 3G to avoid overload situation, and mainly drive stability in the network. More feedback from other networks deploying other UTRAN is needed.

• The feature has achieved expectation of Excelcomindo operator for Intersystem operability. This was also done, with support of NE team related to 2G-3G Reselection, 3G-2G Reselection

and 3G-2G Handover features.

2G-3G Handover



APPENDIX I. 2G-3G HANDOVER CONFIGURATION RECOMMENDATION FOR EXCELCOMINDO

The following table lists all 2G-3G Handover parameters template to be applied during the swap. Fine tuning of this parameters should be done on a case by case basis.

Logical name Definition Value Unit Instance

CGI_3G_REQD Controls format of 3G cell identifications sent to the MSC.

1 None BSC

SCRAMBLING_CODE_3G(n) This parameter indicates the Primary Scrambling Code as defined in 3GPP TS 25.213

Depends on 3G neighbors

None 3G cell

FDD_ARFCN(n) FDD UTRAN frequency Depends on 3G neighbors

MHz 3G cell

EN_3G_DIVERSITY(n) This parameter indicates if diversity is applied for the cell


None 3G cell

Qsearch_C Threshold for searching for 3G cells in dedicated mode depending whether the received signal level of the serving cell is below or above the threshold.

7 dBm cell

THR_ECNO_HO Ec/No threshold above which a handover to UTRAN may be triggered

-125 dBm cell

T3121 This timer is started by sending an INTER SYSTEM TO UTRAN HANDOVER message to the MS and is normally stopped when the MS has correctly seized the UTRAN channel(s). Its purpose is to keep the old channels sufficiently long for the MS to be able to return

14 (140 x 0.1 Sec)

sec BSC

LAC_3G(n) This parameter indicates the Location Area Code as defined in 3GPP TS 24.008. It is used in the HANDOVER COMMAND message

Depends on 3G neighbor

None 3G cell

FDD_REPORTING_THRESHOLD Threshold above which the MS shall report the measurements

6 dB cell

A_ECNO_HO Window size for Ec/No level averages for 2G to 3G handover

10 Samfr cell

CI_3G(n) This parameter indicates the Cell Identifier of a 3G cell as defined in 3GPP TS 25.401


None 3G cell

FDD_MULTIRAT_REPORTING Number of the strongest 3G cells to be reported by the MS in the measurement report message

2 None cell

FDD_REPORTING_OFFSET Offset that the MS shall apply to measurements before reporting

18 dB cell

MNC_3G(n) Mobile Network Code of a neighbor 3G cell of the own PLMN or of a foreign PLMN.


None 3G cell

MCC_3G(n) Mobile Country Code of a neighbor 3G cell Depends None 3G cell

5 For cells with high Radio drop or Very low efficiency, it’s recommended to set this parameter to a higher value (e.g. -9 dB). But this will reduce the number of required Handover.

2G-3G Handover



of the own or of a foreign PLMN. on 3G neighbors

EN_3G_HO This flag enables/disables the 2G-3G handover

Enabled None cell

RNC_ID(n) This parameter indicates the RNC Identifier as defined in 3GPP TS 25.401. It is used in HO Required message sent to the MSC.


None 3G cell

2G-3G Handover



APPENDIX II. 2G-3G RESELECTION CONFIGURATION RECOMMENDATION FOR EXCELCOMINDO

The following table lists all 2G-3G Handover parameters template to be applied during the swap. This template aims to Reselect 3G whenever possible. Fine tuning of this parameters should be done on a case by case basis.

Logical name Definition Value Unit Instance

EN_2G_TO_3G_CELL_RESELECTION Enables/Disables the GSM to UTRAN FDD cell reselections and defines the 3G search activation mode for

MS in GMM Ready state.

1 None cell

FDD_FREQUENCY_LIST List of neighbor FDD UTRAN frequencies Depends on 3G network

MHz BSS

FDD_GPRS_Qoffset Offset added to the received level average of the serving cell and of the neighbor GSM cells

for UTRAN FDD cell re-selection in GPRS

(default) -32 dB cell

FDD_Qmin Minimum threshold for Ec/Io for UTRAN FDD cell re-selection.


FDD_Qoffset Offset added to the received level average of the serving cell and of the neighbor GSM cells for UTRAN FDD cell re-selection.


Qsearch_I Threshold for searching for 3G cells depending whether the received level average of the serving cell is below or above

the threshold.

Always search for 3G neighbor cells

dBm cell

Qsearch_P Threshold for searching for 3G cells in GPRS depending whether the received level average of the serving cell is

below or above the threshold


dBm cell

Qsearch_P_PTM Threshold for searching for 3G cells in GPRS packet transfer mode depending whether the received level average of the serving cell is below or above the threshold


dBm cell

2G-3G Handover



APPENDIX III. 3G-2G RESELECTION AND HANDOVER CONFIGURATION RECOMMENDATION

As there are no parameters in ALU BSS related to these procedures, The recommendation here is that to make sure of correct 2G adjacency definition in Huawei UTRAN. Thus whenever an update in 2G cells configuration, it must be reflected in 3G side.

The following Configuration Parameters should be kept up to date:

• LAC

• Cell Id

• NCC

• BCC

• MCC

• MNC

• ARFCN

END OF DOCUMENT

44383099-2G-3G-handover-Ed02

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