Sqi vs Rxqual

8/20/2019 Sqi vs Rxqual

1/73

Aircom International

TECHNICAL REPORT 1 (73)Prepared (also subject responsible if other) No.

Senior Engineer Emerson Eduardo Rodrigues Approved Checked Date Rev Reference

2006-03-286 PA1

Technical report - GPI IRAT HO

Abstract

This is a technical report for the IRAT Handover and Cell reselection project being done inMTN WCDMA network in South Africa


2/73




2006-03-286 PA1

Executive Summary

Huawei and MTN SA performed during the last 7 weeks tests of the Inter Radio accessTechnology (IRAT) mobility between MTN’s 3G and 2G networks in South Africa.

For the 3G to 2G handover a choice between CPICH RSCP and CPICH Ec/No can bedone to trigger the handover. For the initial network launch when there is no or low loadlevel and no major interference problems in the network CPICH RSCP gives a more stableIRAT handover from 3G to 2G. However in areas where there initially is a relatively high

level of interference, such as high-rise buildings, CPICH Ec/No is a more safe choice ofmeasurement quantity for triggering the handover.

One drawback of using CPICH Ec/No is that a relatively high triggering threshold isneeded to have stable handovers in coverage-limited scenarios. This might lead to thatsome users at some locations move to the 2G network even though they could havereasonable 3G coverage.

The choice of measurement quantity for the triggering is a matter of trading pros of onequantity for cons with the other. The decision should be taken bearing in mind the strategyof MTN current network deployment and future network expansions.


3/73




2006-03-286 PA1

Contents

1 INTRODUCTION ...................................................................................................... 6 1.1 B ACKGROUND ............................................................................................... 6 1.2 PURPOSE ..................................................................................................... 6 1.3 MTN’S IRAT MOBILITY STRATEGY .................................................................. 7

2 THEORY ................................................................................................................... 8 2.1 B ACKGROUND TO IRAT HO/CR ..................................................................... 8 2.2 CPICH RSCP .............................................................................................. 8

2.3

CPICH EC/NO .............................................................................................. 8 2.4

UPLINK AND DOWNLINK ................................................................................. 9 2.5 IRAT H ANDOVER ........................................................................................ 10 2.5.1 U2G: Triggering of 2G measurements ....................................................... 10 2.5.2 U2G: Compressed mode measurements................................................... 11 2.5.3 U2G: Handover from UTRAN .................................................................... 12 2.5.4 G2U: Triggering of 3G measurements ....................................................... 14 2.5.5 IRAT Handover strategy and possible parameter settings ......................... 16 2.6 IRAT CELL RESELECTION ............................................................................ 17 2.6.1 U2G: Triggering of measurements............................................................. 17 2.6.2 U2G: Cell ranking ...................................................................................... 19 2.6.3 G2U: measurements ................................................................................. 20

2.6.4

G2U: Cell Ranking ..................................................................................... 21

2.6.5 IRAT cell reselection strategy and possible parameter settings ................. 22 2.7 SIZE OF NEIGHBOUR LIST ............................................................................. 23 2.8 PERFORMANCE INDICATORS ........................................................................ 24 2.8.1 IRAT HO Success Rate (U2G) .................................................................. 24 2.8.2 IRAT HO Success Rate (G2U) .................................................................. 24 2.8.3 Cell reselection outage time U2G .............................................................. 24 2.8.4 Cell reselection outage time G2U .............................................................. 24

3 METHOD ................................................................................................................ 25 3.1 TESTS ........................................................................................................ 25 3.1.1 Test phases ............................................................................................... 25

3.1.2

Test cases ................................................................................................. 25 3.2 TOOLS ........................................................................................................ 26

3.2.1 TEMS Investigation scanner ...................................................................... 26 3.2.2 TEMS Investigation WCDMA 6.0 + Terminals ........................................... 26 3.2.3 TEMS Investigation WCDMA 3.0.3 + Terminal .......................................... 26 3.2.4 Equipment Set up (Initial Phase) ............................................................... 27 3.3 NETWORK LOAD .......................................................................................... 27 3.3.1 Uplink load ................................................................................................ 27 3.3.2 Downlink load ............................................................................................ 27 3.4 TEST PROCEDURES ..................................................................................... 28 3.5 INITIAL PHASE TEST LOCATION ..................................................................... 29 3.6 V ALIDATION PHASE TEST LOCATION .............................................................. 30

3.7

TEST 1: U2G AND G2U HANDOVER BASED ON EC/NO ................................... 31

3.7.1 General comments .................................................................................... 31


4/73




2006-03-286 PA1

3.7.2 Purpose ..................................................................................................... 31 3.7.3 Parameter ................................................................................................. 31 3.7.4 Theory ....................................................................................................... 31 3.7.5 Performance Indicators ............................................................................. 31 3.8 TEST 2: U2G AND G2U HANDOVER BASED ON RSCP .................................... 32 3.8.1 General comments .................................................................................... 32 3.8.2 Purpose ..................................................................................................... 32 3.8.3 Parameter ................................................................................................. 32 3.8.4 Theory ....................................................................................................... 33 3.8.5 Performance Indicators ............................................................................. 33

3.9

TEST 3: U2G AND G2U CELL RESELECTION .................................................. 33 3.9.1 General comments .................................................................................... 33

3.9.2 Purpose ..................................................................................................... 33 3.9.3 Parameters ................................................................................................ 33 3.9.4 Test execution ........................................................................................... 34 3.9.5 Performance Indicators ............................................................................. 34 3.10 TEST PLAN .................................................................................................. 34 3.11 TIME PLAN .................................................................................................. 34

4 RESULTS ............................................................................................................... 35 4.1 INITIAL PHASE ............................................................................................. 35 4.2 V ALIDATION PHASE ...................................................................................... 36

5

CONCLUSIONS ..................................................................................................... 37

5.1 U2G USING CPICH RSCP .......................................................................... 37 5.2 U2G USING CPICH EC/NO .......................................................................... 38 5.3 G2U H ANDOVER (EC/NO AND RSCP) .......................................................... 39 5.4 IDLE MODE BEHAVIOUR (CR U2G AND G2U) ................................................. 39 5.5 SIZE OF NEIGHBOUR LIST ............................................................................. 39 5.6 U2G TRIGGERING: RSCP OR EC/NO ............................................................ 40 5.7 HUAWEI RECOMMENDATION ......................................................................... 40 5.8 FURTHER STUDIES ...................................................................................... 41

6 PROPOSED PARAMETER SETTINGS .................................................................. 42

7 ABBREVIATIONS .................................................................................................. 45

8 REFERENCES ....................................................................................................... 45

9 APPENDIX A - INITIAL PHASE RESULTS ............................................................ 46 9.1 OVERVIEW .................................................................................................. 46 9.2 TEST C ASE GROUP (U2G): .......................................................................... 46 9.3 TEST C ASE GROUP (G2U): .......................................................................... 53 9.3.1 QSC and MRSL ......................................................................................... 53 9.3.2 FDDMRR ................................................................................................... 54

10 APPENDIX B - VALIDATION PHASE RESULTS ................................................... 56 10.1 OVERVIEW .................................................................................................. 56 10.2 EC/NO STRATEGY ....................................................................................... 56

10.3

RSCP STRATEGY ....................................................................................... 60 10.4 IDLE MODE RESULTS .................................................................................... 63


5/73




2006-03-286 PA1

11 APPENDIX C - GENERAL PARAMETERS ............................................................ 65 11.1 3G TO 2G HO PARAMETERS ........................................................................ 65 11.2 2G TO 3G HO PARAMETERS ........................................................................ 67


6/73




2006-03-286 PA1

Revision History

1 Introduction

1.1 Background

Huawei performed an IRAT handover testing service for MTN South Africa. The servicewas focused on a selection of some WCDMA and GSM parameters.

The IRAT handover module was divided into two phases: analysis phase and validationphase. The reason of this was to verify the findings from the initial testing in differentenvironment to get more information to base the parameter settings decision on.

1.2 Purpose

The purposes of this technical report are to:

1. Describe what had been done and technical problems during the project

2. Present results and findings from the tests

3. Conclude the findings

4. Provide final recommendation(s) on parameter settings

This report is divided into four parts: theory, method, results and conclusions


7/73




2006-03-286 PA1

1.3 MTN’s IRAT mobility strategy

MTN strategy regarding the IRAT mobility can be summarised with the following points:

Stay in 3G as long as possible, so as to maximize the enhanced service capacityoffered in 3G.

Use 2G as a safety net, and allow seamless handovers between the 2G and 3Gnetworks.

Move back to 3G as quickly as possible once there is 3G coverage if the UE has togo to 2G due to a lack of 3G coverage.

The identified solution for the short term should be consistent with MTN networkevolution, be it coverage extension or capacity growth.


8/73




2006-03-286 PA1

2 Theory

2.1 Background to IRAT HO/CR

The purpose of IRAT handover functionality is to let a user who cannot access the 3Gnetwork or retain its service in the 3G network handover or reselect to a 2G backbonenetwork instead. Whether or not the users can access/retain the connection to the 3G

network will be dependent on the required and available power in uplink and downlink.

The required power will in among other things be dependent on the pathloss andinterference situation in up and downlink. One way of estimating the pathloss is thereceived signal code power (RSCP) of the CPICH. However the CPICH RSCP does nottake any interference into consideration. The Ec/No of the CPICH is a measurement thattakes both the pathloss and the interference situation into consideration.

2.2 CPICH RSCP

The CPICH Received Signal Code Power (CPICH RSCP) is dependent on the CPICHtransmitted code power, the pathloss. Since the transmitted power on the CPICH isconstant the CPICH RSCP will primarily be affected by the pathloss. Hence a decrease inthe CPICH RSCP will mean that the pathloss in both up and downlink has increased. The

absolute accuracy requirement for the CPICH RSCP measurements is 6-8 dB [1].

2.3 CPICH Ec/No

The CPICH Ec/No is defined as the energy per chip divided by the total in-band

interference. Theoretically it is defined as the CPICH RSCP divided by the RSSI (receivedsignal strength indicator).

CPICH Ec/No = CPICH RSCP / RSSI

Both the CPICH RSCP and the CPICH Ec/No will increase with a decrease in the pathloss.However the Ec/No is both proportional to the pathloss and inversely proportional to theRSSI. Thus, the relation between CPICH Ec/No and pathloss is not linear as in the RSCPcase. Particularly at the cell border in cases where there is mainly one dominant server thebehaviour of the CPICH Ec/No is not completely straightforward.


9/73




2006-03-286 PA1

CPICH RSCP

Pathloss

CPICH Ec/No

RSSI

CPICH RSCP

Pathloss

CPICH Ec/No

RSSI

The figure above describes the principle of the scenario previously mentioned. As can beseen the CPICH Ec/No remains relatively constant since both the pilot signal and the

interfering signals are more or less subject to the same pathloss. Once the thermal noisebecomes the dominant part of the RSSI the CPICH Ec/No also starts to degrade but not assteep as the RSCP degradation. When the signal finally becomes lower than the thermalnoise floor the Ec/No will drop sharply. This description of the scenario is highly simplified.

The advantage with the CPICH Ec/No measurement is that it takes into consideration thedownlink interference situation in the network through its dependency on the RSSI.

The absolute accuracy requirement for the CPICH Ec/No measurements is 1.5-3 dB,which is considerably higher than the requirements for the RSCP [1].

2.4 Uplink and Downlink

None of the previously discussed measurements does directly cater for the uplinkcoverage and interference criteria required for the dedicated channel to retain theconnection. However if the uplink and downlink are relatively balanced from a required andavailable power point of view, one could use the CPICH RSCP to represent the uplink aswell as downlink pathloss. When letting the CPICH RSCP represent the maximumtolerable pathloss for the dedicated channel in both up and downlink one has to take intoconsideration a few issues. The mapping will be dependent on whether or not a ASC(TMA) is used, the UE Tx power class, the downlink maximum code power for the

dedicated channel, the CPICH Tx power etc.

The mapping of the CPICH Ec/No to the up and downlink interference situation is slightlymore complicated. Since the load situation might be different in the up and downlink theCPICH Ec/No has no direct correlation with the uplink interference situation. However inmost cases one could suspect that the downlink load level could be higher than the uplinkload level due to the asymmetric PS radio bearers and the higher power consumption inthe downlink due to soft handover.


10/73




2006-03-286 PA1

2.5 IRAT Handover

2.5.1 U2G: Triggering of 2G measurements

To perform the handover from the 3G network the UE has to conduct measurements onthe 2G frequencies of the 2G neighbour cells. The set up of those measurements areinitiated when the UE is reporting event 2d to UTRAN in a measurement report.

The event 2d happens when the CPICH RSCP of all cells in active set drops below thethreshold usedFreqThresh2dRscp minus the value hysteresis2d /2 for TTT2d milliseconds. Alternatively will the event 2d happen when the CPICH Ec/No of the cells in active setdrops below the threshold usedFreqThresh2dEcno minus the value hysteresis2d /2 forTTT2d milliseconds. After receiving a measurement report with the event 2d UTRAN willsent the message physical channel reconfiguration to the UE for the UE to reconfigure tocompressed mode by spreading factor reduction (SF/2).

time for measurementsTf

= 10 ms

SF=SF0

SF=SF0 /2

SF=SF0

Compressed mode

time for measurementsTf

= 10 ms

SF=SF0

SF=SF0 /2

SF=SF0

Tf

= 10 ms

SF=SF0

SF=SF0 /2

SF=SF0

Tf

= 10 ms

SF=SF0

SF=SF0 /2

SF=SF0

Compressed mode

After this a measurement control message will be sent to the UE containing the monitored

neighbour list for the 2G neighbour cells. The UE will then tune into the frequencies of theneighbouring 2G cells in the neighbour list during the empty slots created in thecompressed frames.

In case there are no 2G neighbours defined for the cells in active set, UTRAN will notcommand the UE into compressed mode since there are no neighbour cell frequencies toperform measurements on.

The compressed mode measurements are stopped either when the UE handover toappropriate 2G cell or if the UE reports the event 2f in a measurement report to UTRAN.UTRAN will then send a measurement control message to the UE to release thecompressed mode measurements.


11/73




2006-03-286 PA1

The event 2f happens when the CPICH RSCP of at least one cell in active set rises abovethe threshold usedFreqThresh2dRscp plus usedFreqRelThresh2fRscp plus the valuehysteresis2f /2 for TTT2f milliseconds. Alternatively the event 2f will happen when theCPICH Ec/No of at least one cell in active set rises above the thresholdusedFreqThresh2dEcno plus usedFreqRelThresh2fEcno plus the value hysteresis2f /2 forTTT2f milliseconds.

2.5.2 U2G: Compressed mode measurements

The measurement control sent after the physical channel reconfiguration also containsinformation about the requirements for the triggering of event 3a. Event 3a happens whenthe CPICH RSCP of all cells in active set drops below the threshold utranThresh3aRscp minus the value hysteresis3a/2 for TTT3a milliseconds or when the CPICH Ec/No of allcells in active set drops below the threshold utranThresh3aEcno minus the valuehysteresis3a/2 for TTT3a milliseconds. In addition to either of the two previous conditionsthe carrier RSSI of the target GSM cell has to be above the threshold gsmThresh3a andthe verified that the BSIC of the target cell is the same as the cell in the monitored list.

The 2G measurements required for the UE to be able to evaluate if the event 3a criteria isfulfilled, are performed in the following way.


12/73




2006-03-286 PA1

The UE measures the RSSI of all carriers in the neighbour list and rank them according tosignal strength. When using compressed mode with gap length 7 slots, the UE is requiredto take 6 samples per gap [1]. Each carrier shall be measured 3 times, which means that 2carriers can be measured per gap. The time to measure and rank all carriers are hencedependent on the number of 2G neighbours in the neighbour list. In one reporting period of480ms the UE can measure 12 neighbours, in 960ms 24 neighbours and so on. The RSSImeasurements are continuously repeated to maintain the ranking of the cells. 3/8 of themeasurement occasions are used for the RSSI measurements.

The UE is also required to attempt BSIC decoding of the 8 highest ranked cells (the

ranking might be continuously changing). The BSIC decoding can only be done if the BSICtransmission is done fully within one transmission gap. In the worst case the UE will need2 attempts to decode the BSIC, which will mean that the decoding will take 5.28secondsper carrier [1]. Half of the measurement occasions are dedicated to BSIC decoding and 1/8of the measurement occasions are dedicated for BSIC reconfirmation, since the BSIC isonly considered as verified for a certain period of time.

If a cell is BSIC decoded and the criteria for event 3a is fulfilled the UE will send ameasurement report indicating the number in the neighbour list for the cell fulfilling thecriteria. This will be the target cell to perform the handover to. Since the BSIC verificationis quite time consuming it could be so that it is not the best ranked cell that is BSICdecoded since the ranking might have changed during the decoding time. If the event

criteria’s are fulfilled the decoded cell will be reported even though it is no longer thestrongest in the ranking. It is therefore desirable to keep the neighbour list as short aspossible as to minimise the probability of this happening and so that the ranking list can bequickly updated.

2.5.3 U2G: Handover from UTRAN

Upon reception of a measurement report indicating the event 3a the RNC attempt toallocate resources in the target GSM cell. If and when the resources are secured a

handover from UTRAN command message is sent from the RNC to the UE. When thehandover is completed the UE will send the message handover complete to the BSC. Thiswill initiate the release of the resources in the UMTS network.

In case the UE fails to connect to the GSM network it will send the message handoverfrom UTRAN failure to UTRAN. If possible the call will be kept and another handoverattempt made.

The flowchart below depictures a successful handover from UMTS to GSM.


13/73




2006-03-286 PA1

All parameters defining the different thresholds used during the UMTS to GSM handoverare set per RNC and per UMTS cell. Hence, for the RNC parameters one value has to befound that can cater for the whole network.

The picture below describes the complete IRAT handover procedure from U2G.


14/73




2006-03-286 PA1

Measurement Quantity ( Ec/No and RSSI )

WCDMA cell

GSM cell

usedFreqRelTresh2fEcno

usedFreqTresh2dEcno hysteresis2d/2

hysteresis2f/2

hysteresis2d/2

utranTresh3aEcno gsmTresh3a

hysteresis3a/2

Reportingevent 2d

Reportingevent 2d

Reporting

event 2f Reportingevent 3a

A user entering compressed mode will be forced to roughly double its Tx power during thepart of the compressed frame when the data is transmitted. For downlink CompressedMode (CM) the available Tx power is increased during the compressed frames but for theuplink the UE max Tx power is setting the limit. If the CM is performed when the UEalready is transmitting close to its maximum output power, it might lead to increased BERand BLER due to the inability of the power control to combat the fast fading dips.

Since there is an increased interference situation in the network due to the compressedmode, it is desirable to have as few users as possible in CM and each user in CM for asshort time as possible. To reduce the number of users in compressed mode, low values onthe triggering thresholds are desirable (i.e. moving into CM late). This would mean thatusers are entering CM at low signal levels/low Ec/No quality levels.

The IRAT handover functionality is further described in [2].

2.5.4 G2U: Triggering of 3G measurements

The measurements performed on the 3G neighbours while on a voice connection in 2G isinitiated at a certain level of signal strength. The parameter QSC defines a signal strengthcriterion, which has to be fulfilled before measurements on the UMTS neighbours areperformed. The threshold can either be set to a level (-98 - -74dBm) for which the GSMsignal strength has to be below before the measurements are performed. The other optionis to set QSC to a level (-78 - -54dBm) for which the signal strength has to be above beforethe measurements are performed. Setting the QSC parameter can also disable theevaluation of the GSM signal strength, so that measurements are never performed orpermanently enabled by setting the QSC to always.


15/73




2006-03-286 PA1

The parameter ISHOLEV defines the load level is the GSM network which should beexceeded before starting to evaluate the reported UMTS measurements. ISHOLEV isdefined as the percent of idle TCH’s than need to be allocated. Hence the value 99%means that measurements on UMTS are always evaluated.

The information on when to measure along with 3G frequency and scrambling codes of the3G neighbouring cells are sent to the UE in the Measurement Information message.

The UE may use the search frames, which are not required for BSIC decoding, for thesemeasurements. If indicated by the parameter SPRIO = YES, the UE may use up to 25

search frames per 13 seconds without considering the need for BSIC decoding in theseframes.

The UE shall report a new best UTRAN cell, which is part of the neighbour cell list, at thelatest 5 seconds after it has been activated under the condition that there is only oneUTRAN frequency in the neighbour cell list and that no new GSM cells are activated at thesame time and under good radio conditions [3]. If a new GSM frequency is activated duringthe measurements, the required minimum reporting time is extended by the time to decodethe BSIC of the new cell.

The reporting of UMTS cell measurements are done in the same measurement reports asthe GSM measurements. Since there is only possible to report 6 cells in the measurement

report the number of reported GSM cells are reduced for a multi RAT capable UE. Theparameter FDDMRR (1-3) defines how many positions in the measurement report thatshould be dedicated to 3G cells.

The GSM measurement report fields RxLev indicates the received signal strength of thereported GSM cells in the neighbour list coded according to [3]. For the reported 3G cellsthe reported value does not indicate the signal strength but represents the CPICH Ec/Nodecodes according to the following formula:

CPICH Ec/N0 [dB] = Reported value / 2 – 24.5

The reporting field BCCH-INDEX represents the position in the neighbour list for the 2G

cells. For the 3G cells it is always reported as 31 (representing only 31 GSM neighbourcells when UMTS neighbour is defined). Finally the reported field BSIC represents theBSIC for the GSM cells and the position in the 3G neighbour list for the 3G cells.

The handover decision is made depending on whether or not the reported CPICH Ec/Noexceeds the value represented by the parameter MRSL. The reporting and evaluation of3G neighbour cells does not affect the locating algorithm used for the ranking andevaluation of reported 2G neighbours.


16/73




2006-03-286 PA1

Filtering

Allocation reply

Inter System Handover

algorithm

ISHOLEV = 99 %

Organizing the list

Urgency condition

Basic ranking

Radio Network functions

evaluations

Sending the list

WCDMA Cell

measurement

Traffic load

TTTTSTB TTTTSTB

% idle TS: 1/6 16, 7%

Add WCDMA cell

to candidate list

% idle TS

ISHOLEV

Ec/No

> MRSL

All parameters used to define the different thresholds used in the G2U handover are all setper GSM cell.

2.5.5 IRAT Handover strategy and possible parameter settings

One desirable parameter setting could be to stay with the voice connection in the 3Gnetwork as long as the quality of the connection is sufficient. When this criteria is no longerfulfilled it could be desirable to move the connection to the 2G network. Finally it could bedesirable to move the connection back to the 3G network again when the quality issufficient, but this is not so important since the end user perception of the voice call shouldbe fairly similar in both 2G and 3G.

When trying to achieve this in practice one has to take many other aspects intoconsideration. One of the considerations is to be able to perform the actual measurementsand the handover before the quality becomes to bad. When in compressed mode theterminal will need to approximately double the power during the compressed slots. This willlead to a reduced coverage since the available power is constant (in uplink). If for exampledriving in high speed out of the coverage region one has to back off the handoverthresholds so that the connection can be maintained during the measurement andrelocation time while still in compressed mode.

The measurement criteria for moving from U2G and G2U previously described can bedescripted as follows:


17/73




2006-03-286 PA1

Evaluate Ec/No3G 2GEvaluate Ec/NoEvaluate Ec/No3G3G

3G 2G3G3G Evaluate RSCP

or

Evaluate Ec/No3G 2GEvaluate Ec/NoEvaluate Ec/No3G3G Evaluate Ec/NoEvaluate Ec/No3G3G 2G2GEvaluate Ec/NoEvaluate Ec/No3G3G

3G 2G3G3G Evaluate RSCP3G3G 2G2G3G3G Evaluate RSCP

or

When moving from U2G either CPICH RSCP or CPICH Ec/No can be chosen asmeasurement quantity. When moving from G2U the standard only allows for CPICH Ec/Nomeasurements to be reported.

Evaluate Ec/No2G 3GEvaluate Ec/NoEvaluate Ec/No2G2G 3G3GEvaluate Ec/No2G 3GEvaluate Ec/NoEvaluate Ec/No2G2G 3G3G

One aspect to consider is the possible ping - pong effects while moving between 3G and2G. If CPICH RSCP is chosen as measurement for the U2G handover, special care has tobe taken when setting the parameter MRSL (Ec/No) for the G2U handover. Since there isno exact relationship between the CPICH Ec/No and the CPICH RSCP it might be so thatthe CPICH Ec/No is better than the value defined by MRSL at the point when the U2Ghandover is triggered due to a low CPICH RSCP. This would then result in a ping - ponghandover from G2U since the criteria CPICH Ec/No > MRSL is fulfilled. However for thevoice service, this scenario can be avoided by not letting the user perform the G2Uhandover at all (ISHOLEV=0% or QSC = never) or by setting the MRSL threshold to a veryhigh value to delay the G2U handover. However the limitation with being in 2G with a voice

service compared to the 3G-voice service is that the availability of the multi-RAB (voice +PS64) in the 3G network.

2.6 IRAT Cell Reselection

2.6.1 U2G: Triggering of measurements

In idle mode the UE is required to start doing measurements on 2G cells and evaluatethem in a cell ranking procedure when the following criteria is fulfilled:

CPICH Ec/No


18/73




2006-03-286 PA1

Where the parameter qQualMin is the minimum acceptable CPICH Ec/No level forcamping on a 3G cell and the parameter sRatSearch defines the offset from qQualMin atwhich levels the measurements should start. Both parameters are set per UMTS cell.

This means that the UE is not required to always measure and evaluate the 2G cells in idlemode. The parameters previously defined are transmitted in the system information SIB3.The neighbour list with 2G neighbours is transmitted to the UE in the system informationSIB11.

The parameter qHyst2 is the hysteresis parameter used for the 3G-cell reselectionevaluation. For a 3G-cell to be replaced by another 3G cell it is required to be at leastqHyst2 dB better (in terms of CPICH Ec/No) for the cell reselection to take place accordingto the picture below.


19/73




2006-03-286 PA1

qHyst2

qHyst2

qHyst2

treSelection treSelection

treSelection

treSelection

qQualMin

CPICH_Ec/No

Time

The blank dotted lineis the serving cells.

Although this hysteresis parameter only effects the 3G-3G cell re-selection it also have animpact on the 3G-2G cell reselection. If the current 3G cell’s CPICH Ec/No drops below thecriteria for 2G measurements, 2G cells will be measured and evaluated and a 3G to 2Gcell reselection performed if the predefined criteria’s are fulfilled. At the same time it couldbe so that there exists a 3G cell with a CPICH Ec/No better than the threshold for 2G

measurement evaluation but at the same time less than qHyst2 dB better than the current3G cell. This would effectively mean that the UE start camping on a 2G cell even thoughthere exist a 3G cell better than the required quality criteria for staying in the 3G network.

2.6.2 U2G: Cell ranking

If the parameter qualMeasQuantity = 2 (CPICH Ec/No used for ranking), the cell ranking isdone in two steps. First a ranking is done based on the signal strength (CPICH RSCP andGSM RxLev), if a GSM cell turnout to be the highest ranked no more ranking is done and a

cell reselection to the GSM cell is done. If a WCDMA cell is strongest, a second ranking isdone based on CPICH Ec/No with only WCDMA cells. If the parameter qualMeasQuantity = 1 (CPICH RSCP) only one cell ranking need to be done with all cells (2G and 3G)included.

The cell ranking between 3G and 2G cells is done in the following way (also described inthe picture below):

R(serving 3G cell) = Qmeas(s) + qHyst1

R(neighbour 2G cell) = Qmeas(n) - qOffset1sn

If the R criterion for the 2G cell is higher than the R criteria for the 3G cell for the timeduration treSelection seconds, a cell reselection to the 2G cell is done.


20/73




2006-03-286 PA1

The quantity Qmeas is the CPICH RSCP for the 3G cell and RxLev for the 2G cell. Theparameter qHyst1 is the hysteresis parameter affecting the signal strength (not the Ec/No),and the parameter qOffset1sn is a parameter used to offset the measured GSM signalstrength in the ranking.

2.6.3 G2U: measurements

The start of the measurements on the 3G cells is, in the same way as for the dedicatedmode, started when the GSM signal strength is either above or below the value indicatedby the parameter QSI .

The parameter can also be set so that measurements on the 3G neighbours are either

never or always performed. The latter alternative is highly desirable in case one wishes toutilise the 3G network as much as possible.


21/73




2006-03-286 PA1

The parameter QSI is defined per GSM cell and is transmitted together with the 3Gneighbour cell list in the system information type 2quater. The UE shall be able to identifyand select a new best UTRAN cell on a frequency, which is part of the 3G Cell Reselectionlist, within 30 seconds after it has been activated under the condition that there is only oneUTRAN frequency in the list and under good radio conditions [3].

For the measured 3G cell to be considered in the cell ranking procedure the Ec/No of themeasured 3G neighbour has to at least fulfil the following criteria:

CPICH Ec/No > FDDQMIN

Where the parameter FDDQMIN can be set from 0 to 7 representing an Ec/No values from –20 to –6 dB. The table below will

UE Mapping of value 0 1 2 3 4 5 6 7

[dB] -20 -6 -18 -8 -16 -10 -14 -12

2.6.4 G2U: Cell Ranking

The cell ranking for the cell reselection from 2G to 3G is done in the following way:

CPICH Ec/No > FDDQMIN (prerequisite for ranking)

AND

CPICH RSCP > RLA(s+n) + FDDQOFF

where the RLA(s+n) is the average (per cell) signal strength of the serving 2G cell and its 2Gneighbours. The parameter FDDQOFF defines an offset for the measured 2G signalstrength (-28 - +28 dB) used to prioritise the 2G or 3G cell in the ranking. There is also a

possibility to set the parameter to - to always prioritise the 3G cell and thereby effectivelydisable the cell ranking procedure. FDDQOFF is defined per 2G to 3G neighbouring cellrelations.

Up to 15 seconds after a U2G cell reselection the parameter FDDQOFF is automaticallyincreased by 5 dB to reduce the risk of ping-pong between 3G and 2G if the desire is to tryto compare the signal strengths.


22/73




2006-03-286 PA1

Measurement

Quantity

FDDQMIN

FDDQOFF

CPICH Ec/No

GSM RLA

CPICH RSCP

t

5 seconds

IRATCC to

WCDMA

CPICH Ec/No

> FDDQMIN CPICH RSCP >

GSM RLA+ FDDQOFF

2.6.5 IRAT cell reselection strategy and possible parameter settings

As in the case of connected mode it could be desirable to set the idle mode parameters sothat the UE is camped on the 3G network as long as it can access the network with a highprobability and with a acceptable quality. However since this probability is dependent onboth the signal strength (pathloss) and quality (Ec/No) of the best 3G cell independently(although they are correlated).

In the current standard the CPICH Ec/No check is always done first, followed by a CPICHRSCP and GSM RxLev comparison. Hence the standard allows for a cell reselectionprocess, which can be described with the following flowchart:

Evaluate Ec/No Evaluate RSCP(relative GSM)

3G 2GEvaluate Ec/NoEvaluate Ec/No Evaluate RSCP(relative GSM)

Evaluate RSCP(relative GSM)

3G3G 2G2G


23/73




2006-03-286 PA1

Since the signal strength evaluation is done by comparing the signal strengths of the 3Gcell with the signal strength of the 2G cells, tuning on cell relation level, of the offset values(qOffset1sn) has to be made. This is only feasible if full co-siting of all 2G and 3G cells aredone. In case of complete co-siting of 3G cells with 2G cells, one single offset couldprobably be used for the whole network. However in the case there are more 2G sites, e.g.indoor sites, hotspot sites etc. the offsets has to be tuned on cell relation level since the 2Gsignal strength could be considerably higher than the 3G signal strength although sufficientto provide a 3G service.

For the G2U cell reselection the current standard can be described with the following flow

chart:

Evaluate Ec/No Evaluate RSCP(relative UMTS)

2G 3GEvaluate Ec/NoEvaluate Ec/No Evaluate RSCP(relative UMTS)

Evaluate RSCP(relative UMTS)

2G2G 3G3G

In this case both the RSCP and the Ec/No criteria should be fulfilled before the cellreselection from G2U is performed. This reduced the probability pf a ping-pong cellreselection between 2G and 3G. Since the signal strength evaluation is here also done by

comparing the 3G and 2G signal strength, parameter tuning on cell relation level isrequired here as well.

2.7 Size of neighbour list

It is always recommended to keep the neighbour lists short, both for the 2G neighbourswhile in 3G and 3G neighbours while in 2G. It is hence crucial that the correct neighboursare defined, and that no unnecessary ones are chosen.

As an example, after IRAT cells change to a cell, which turns out to be less preferable thansome other, a cell reselection in GPRS is required. That process takes time, during whichthe overall throughput and user experience Measurements on IRAT neighbours, is ademanding process for the UE. Therefore, the number of inter-system neighbours must bekept low, around 10. Another reason for keeping the neighbour lists short is the scenariodescribed in the CM theory section.


24/73




2006-03-286 PA1

2.8 Performance Indicators

2.8.1 IRAT HO Success Rate (U2G)

The IRAT handover Success rate is defined as the number of successful IRAT handoversdivided by the number of occasions where an IRAT handover could be expected based onthe signal and quality levels. If the handover is not successful the reason for the failureshould be evaluated. This performance indicator is highly correlated with the drop call rate.This performance indicator is based on subjective evaluation of the logfiles and notnecessary the exact occurrence of a specific message.

2.8.2 IRAT HO Success Rate (G2U)

The IRAT handover Success rate is defined as the number of successful IRAT handoversdivided by the number of occasions where an IRAT handover could be expected based onthe quality levels. If the handover is not successful the reason for the failure should beevaluated. This performance indicator is based on subjective evaluation of the logfiles andnot necessary the exact occurrence of a specific message.

2.8.3 Cell reselection outage time U2G

The cell reselection outage time is measured as the time from starting to read GSMsystem information until the UE is has received a location area update accept messagefrom the GSM network.

2.8.4 Cell reselection outage time G2U

The cell reselection outage time is measured as the time from starting to read UMTSsystem information until the UE is has received a location area update accept messagefrom the UMTS network.


25/73




2006-03-286 PA1

3 Method

3.1 Tests

3.1.1 Test phases

The testing was divided into an initial test phase followed by an analysis phase and avalidation phase. The initial test phase was used to narrow down the possible parametersettings to a few sets. Those parameter settings were later tested in different locations to

find the best possible setting.

The test cases were defined prior to the start of the testing and can be found in “TestSpecifications IRAT HO” and “Validation Specification IRAT HO” documents. After some ofthe test cases during the initial testing was carried out the priorities of the remaining initialtest cases was redone to better utilise the remaining time.

3.1.2 Test cases

3.1.2.1 IRAT Handover

Since the time for the testing was limited many parameters were set to default value or to atheoretical value estimated based on other parameter values. The testing was thenfocused on the following parameters:

usedFreqThresh2dRscp

usedFreqThresh2dEcno

ttt2d

usedFreqThresh2fRscp

usedFreqThresh2fEcnottt2f

utranThresh3aRscp

utranThresh3aEcno

MRSL

sRatSearch

FDDQMIN

FDDMRR

QSC

The strategy for the testing was basically to find an as aggressive value as possible (i.e.

still successful handovers) on each parameter using either CPICH Ec/No or CPICH RSCPas a trigger. This would mean staying as long as possible on the 3G network.


26/73




2006-03-286 PA1

3.2 Tools

3.2.1 TEMS Investigation scanner

TEMS Investigation for WCDMA v6.0 Scanner module was used in the drive routepreparation phase to measure the following items:

CPICH Ec/No

CPICH RSCP

CPICH Scrambling Codes

GSM BCCH carrier RxLev on target cells

C/I on GSM target cells

3.2.2 TEMS Investigation WCDMA 6.0 + Terminals

3.2.2.1 Nokia 6630

The Nokia terminal supports all kinds of handover scenarios in Idle, voice service and PSdata service modes. It always uses compressed mode but do not have so good reportingcapabilities to TIW in terms of BLER, SIR and SIR target etc.

3.2.2.2 Sony Huawei V800

The Nokia terminal supports all kinds of handover scenarios in Idle, voice service and PSdata service modes.

3.2.3 TEMS Investigation WCDMA 3.0.3 + Terminal

3.2.3.1 Motorola A835 (additional equipment for the Validation phase)

The Motorola terminal supports cell reselection in idle mode both from 3G to 2G and backto 3G again as well as voice service handover from 3G to 2G. No other IRAT handoverscenarios are supported.


27/73




2006-03-286 PA1

3.2.4 Equipment Set up (Initial Phase)

RBS RN

C

Uu

Iub

TEMS InvestigationWCDMA

UETR/MTRin OSS-RC

1

Measurement Point

2

Voice Voice

All the equipments within thedotted box is located in car

or portable setup

Call test (B-party)

Long Call Test

TEMSScanner

GPS

3.3 Network Load

3.3.1 Uplink load

It is practically impossible to generate uplink load in an artificial way. Therefore a loadmargin has to be considered when analysing the results.

3.3.2 Downlink load

Increasing the output power on the BCH channel can generate the downlink load. This willnot exactly resemble a real load situation but can be considered an acceptableapproximation of how the system and UE will perform under downlink load. Different loadsituations will have different effects on how many users that are in compressed mode andhow long time they are spending in compressed mode.

Note that the BchPower parameter defines the power on the BCH relative to the power on

the CPICH. The table below shows the load at different BCH power settings assuming thefeeder loss parameter set to 0 dB.


28/73




2006-03-286 PA1

RBS nominal power 17.4W

BchPower[0.1dB]

PTot at RBS [W]) % Load

-31 1.8 10%

30 3.1 18%

60 4.9 28%

80 7.0 40%

100 10.3 59%

3.4 Test procedures

At the test location, before the drive test, the engineer sets up the equipment in the car orthe portable equipment according to the test equipment setting specified in Testspecifications. The engineer also verifies that the UETR is logging and the network is setwith the proper IRAT HO parameter value before starting the drive tests.

During the initial test phase the parameters were changed according to the proceduredescribed in Test Specification. For the Validation phase, three different groups ofparameter settings with three test cases each were predefined.


29/73




2006-03-286 PA1

3.5 Initial Phase test location

Hillbrow, Benrose and the surrounding area have been chosen as the test area for theinitial phase. In this area the GSM coverage is always good, while in UMTS (JHB CBD_2cluster) some RSCP coverage holes and a significant number of low Ec/No-RSCPlocations were detected.The radio environment is deeply influenced by the urban structure, where high blockbuildings, narrow streets and many corners can be seen. All the sites involved in the measurement were set onto Germiston RNC, and for each cellthe BchPower value was set to 20 in order to simulate a certain load on the network.The main reason for that was to get comparable results between RSCP and Ec/Noanalysis strategies.

Geography: All along the route there are hills and flat areas where signal can be seen faraway (Crown Mines) or blocked (Eastgate).


30/73




2006-03-286 PA1

3.6 Validation phase test location

Fourways and the surrounding area have been chosen as the test area for the validationphase. A different test area as well another RNC (Randburg) were chosen for themeasurements, in order to verify the possibility for the adopted parameter settings innumerous places. In this area the GSM coverage is always suitable, while in UMTS(Fourways cluster) some RSCP coverage holes and a significant number of low Ec/No-RSCP locations were detected.The 3G radio environment is floating due to the presence of several kind of clutter areas:urban and sub urban blocks, residential estates and open fields.

Geography: The entire route is changing between hilly and flat areas where signal can beseen far away (e.g. Fairlands).


31/73




2006-03-286 PA1

3.7 Test 1: U2G and G2U handover based on Ec/No

3.7.1 General comments

For this test the predefined settings should be used with a predefined load level.

3.7.2 Purpose

The purpose of the test is to find out the pros and cons of each setting in each

environment.

3.7.3 Parameter

Tested parameters

utranThresh3aEcnousedFreqThresh2dEcnousedFreqThresh2fEcnotimeToTrigger2fMRSLQSI/QSCFDDMRR

measQuantity2 = 2 (Ec/No)utranMeasQuantity3 = 2 (Ec/No)

Parameters fixed during the tests

ueTxPowerThresh6a = 21ueTxPowerThresh6b = 18TimeToTrigger2d = 11sRatSearch = 4FDDQMIN = 7FDDQOFF = 0SPRIO = YESQSCI = 1ISHOLEV = 99

3.7.4 Theory

The procedure should be repeated for each parameter set.

3.7.5 Performance Indicators


32/73




2006-03-286 PA1

Drop call rate

IRAT HO success rate

T3G

T2G

TCMwithoutHO

TCMwithHO

THOCompl

3.8 Test 2: U2G and G2U handover based on RSCP


For this test the predefined settings should be used with a predefined load level.

3.8.2 Purpose

The purpose of the test is to find out the pros and cons of each setting in eachenvironment.

3.8.3 Parameter

Tested parameters

utranThresh3aRscpusedFreqThresh2dRscpusedFreqThresh2fRscptimeToTrigger2fMRSLQSI/QSC

FDDMRRmeasQuantity2 = 1 (RSCP)utranMeasQuantity3 = 1 (RSCP)


ueTxPowerThresh6a = 21ueTxPowerThresh6b = 18TimeToTrigger2d = 11sRatSearch = 4FDDQMIN = 7

FDDQOFF = 0SPRIO = YES


33/73




2006-03-286 PA1

QSCI = 1ISHOLEV = 99

3.8.4 Theory

The procedure should be repeated for each parameter set


Drop call rate

IRAT HO success rate

T3G

T2G

TCMwithoutHO

TCMwithHO

THOCompl

3.9 Test 3: U2G and G2U cell reselection


For this test the predefined setting should be used in each of the predefined environmentsand which each of the predefined load levels.

3.9.2 Purpose

The purpose of the test is to find out the performance with the selected setting

3.9.3 Parameters

Tested parameters

sRatSearchFDDQMIN


utranThresh3aEcnousedFreqThresh2dEcno


34/73




2006-03-286 PA1

usedFreqThresh2fEcnomeasQuantity2 (2 = Ec/No)utranMeasQuantity3 (2 = Ec/No)FDDQOFF= 0FDDMRR = 1SPRIO = YESQSI = 7QSC = 7QSCI = 1ISHOLEV = 99

3.9.4 Test execution

The procedure should be repeated for each parameter set in each environment and foreach load case.


Ec/No vs. RSCP plot when performing the reselection.

Ping pong rate

3.10 Test plan

The tests will be performed with three different sets of parameters per test group:

Strategy Ec/No Strategy RSCP Cell Reselection

e2d -11 -12 -12 -100 -102 -102

e2f 2 2 2 2 3 3

ttt2f 13 13 12 13 13 13e3a -13 -13 -13 -104 -104 -105

MRSL 32 30 29 32 30 29

QSC/QSI 7 8 9 7 8 9

FDDMRR 2 3 3 2 3 3

sRatSearch - - - - - - 8 4 2

FDDQMIN - - - - - - 3 5 7

3.11 Time Plan

Strategy Ec/No


35/73




2006-03-286 PA1

1st parameter set 2005-09-07

2nd

parameter set 2005-09-07

3rd


Strategy RSCP


2nd


3rd


Cell Reselection


2nd


3rd


4 Results

4.1 Initial phase

During the initial phase several triggering thresholds were tested separately or in pairs of

two in the test area. The results of this can be found in Appendix A. Based on those resultsthe test settings were narrowed down to the following table and the load was increased toBCH Power = 40 to test the “brake point” for RSCP measurement.


36/73




2006-03-286 PA1

VTC 1.1 VTC 1.2 VTC 1.3 VTC 2.1 VTC 2.2 VTC 2.3 VTC 3.1 VTC 3.2 VTC 3.3

e2d -11 -12 -12 -100 -102 -102 -11 -11 -11

e2f 2 2 2 2 3 3 2 2 2

ttt2f 13 13 12 13 13 13 13 13 13

e3a -13 -13 -13 -104 -104 -105 -12 -12 -12

sRatSearch 4 4 4 4 4 4 8 4 2

MRSL 32 30 29 32 30 29 29 29 29

QSC/QSI 7 8 9 7 8 9 7 7 7

FDDMRR 2 3 3 2 3 3 1 1 1

FDDQMIN 7 7 7 7 7 7 3 5 7

Ec/No Strategy RSCP Strategy Idle mode

Due to the possibility to use different measurement quantities in the network for IRAT HOevents triggering, three different strategies for parameter testing were created.

The first strategy is based on Ec/No, the second on RSCP and the last one is focusing onthe idle mode behaviour.

During the initial phase we experienced missing messages on the NOKIA 6630: due to thisreason we decided to add an additional terminal (Motorola A835) with the aim to collectmore complete message flows for the analysis.

4.2 Validation phase

During the validation phase the settings described in the table above were used togetherwith an increased BchPower value in the specified location. The results for these tests canbe found in Appendix B.

The analysis of the Nokia 6630 data was more time consuming due to the alreadymentioned problem of some missing messages, so it was more difficult to follow the

message flow during a specific dedicated mode phase (e.g. Call Setup, IRAT HOprocedure). Therefore, sometimes it was almost impossible to find the correct trigger timefor events. On the other hand, the Sony Huawei V800 and the Motorola A835 showed amore consistent message flow. It was also experienced a different UE sensitivity: the V800is more sensitive and due to this fact it was exposed to CM ping-pong effects more thanthe other two mobiles. The A835 instead has less sensitivity in the receiver, and due to theolder SW/HW version, some freezing and some abnormal TIW disconnections wereexperienced.


37/73




2006-03-286 PA1

5 Conclusions

5.1 U2G using CPICH RSCP

The CPICH RSCP is a more stable triggering quantity in areas with low interference andlow signal strength than CPICH Ec/No. When driving out of coverage in such environmentthe RSCP triggering quantity can make sure that the handover is made at a relatively lowpathloss regardless of interference situation. This reduces the probability of the UEremaining in the 3G network at a high pathloss to high for the UE to access the network.

However if the interference situation increases it might not be the pathloss that sets thelimit for the accessibility to the network but the interference. The pathloss where the UEloses its coverage will depend on the link budgets for the required service. This will in turnbe dependent on e.g. availability of ASC (TMA) in the uplink and UE Tx power capability.The plot below shows the UE Tx power distribution for different CPICH RSCP for all testedUE when driving out of coverage in the Fourways area.

UE Tx power

-15

-10

-5

0

5

10

15

20

25

-130,0 -120,0 -110,0 -100,0 -90,0 -80,0 -70,0 -60,0 -50,0 -40,0 -30,0

RSCP

U E T x p o w e r

Total

It can be seen that if selecting the handover threshold for event 3a to –104dBm there arestill margins left to the maximum UE Tx power of 21dBm.


38/73




2006-03-286 PA1

The drawback with using the CPICH RSCP as measurement quantity is its insensitivity toload in both up and downlink. The received power on the pilot channel will always be thesame regardless of load situation in either up or downlink. If the load situation increasesthe UE Tx power and downlink code power will increase necessarily to keep theconnection.

One type of location where this (at a very sparsely loaded network) is a problem, is atplaces which are reached by many overshooting cells without having any dominant server.

Another drawback with the use of CPICH RSCP as a measurement quantity for the U2G

handover and cell change is that CPICH Ec/No has to be used for the G2U handover andcell reselection. If RSCP is used for the U2G triggering there is a potential for ping-pongeffects between 3G and 2G. The ping-pong effects might not be such a big problem for thevoice service since the end user experience is fairly similar in both networks. Hence theMRSL threshold can be set to a very high value or the QSC parameter could be set so thatthe UE never attempt to perform the G2U handover. The drawback of doing this is that theuser does not have the opportunity to access the multi-bearer service while in 2G.

5.2 U2G using CPICH Ec/No

When using CPICH Ec/No as measurement quantity an increase in downlink interferencewill be reflected on the value. Although an increase in uplink interference will not bereflected on the CPICH Ec/No value, it can be assumed that there is a correlation betweenthe uplink and downlink interference levels and rather more interference in the downlink.The problematic location type for the CPICH Ec/No measurement quantity is theenvironment where the moving out of coverage (in terms of pathloss) when theinterference level is low. In such environments the CPICH Ec/No remains relatively gooduntil the thermal noise becomes the dominant part of the RSSI. At that point the CPICHEc/No start to degrade quicker to finally drop heavily when the CPICH RSCP is below thesensitivity of the receiver.

At those levels the UE might be transmitting near its maximum Tx power and theconnection is not very reliable.

Whether or not the IRAT handover is successful at such a location is dependent on howfast the quality is degrading, it might very well be so that a slow moving UE manage tohandover to GSM whereas a fast moving UE fails due to that the connection drops beforethe end of the message flow.

If choosing CPICH Ec/No as the measurement quantity for the triggering it is easy toachieve a balance and hence avoid ping-pong handovers between 3G and 2G since Ec/Nois used both ways. Due to some mobile limitations, ping-pong will occur even when usingCPICH Ec/No in case a high value (such as –11 dB) is used for the event 3a triggering.


39/73




2006-03-286 PA1

5.3 G2U Handover (Ec/No and RSCP)

If CPICH Ec/No is used for the handover triggering the parameter MRSL which controlsthe G2U handover should be set to a value approximately 1 dB higher than the value usedfor the event 2f triggering. This is to avoid ping-pong behaviour, which will increase the riskfor dropped calls during a later handover attempt. If on the other hand CPICH RSCP isused for the triggering it is recommended to either set the parameter QSC to neverperform any measurements (15). In this case the UE will remain in the 2G network until thecall is terminated and the idle mode parameters evaluates on which cell the UE shouldcamp. The drawback with staying with a voice call in 2G as opposed to 3G network is the

lack of opportunity to use the multi-bearer service (Voice +PS).

5.4 Idle mode behaviour (CR U2G and G2U)

If the Reselection from UMTS to GSM is triggered too early, this might force the UE toleave the 3G network for GSM even if the WCDMA coverage is sufficient enough toprovide 3G services. This leads the end user to stay unnecessary time in a technology thatis limiting his opportunities. On the other hand, leaving UMTS too late can increase the riskto stay in a network that is not able to handle end user expectations anymore (Call set-ups

could be blocked/dropped).

The GSM to UMTS cell reselection settings should be consistent with the U2G settings inorder to support the best usage of both technologies.

Since the main strategy is to maintain an end-user as long as possible into the 3Gnetwork, it’s advisable to set the CR parameters with a gap of at least 2 dB betweenthemselves. If the value for the 3G network is set at e.g. –14dB to leave towards GSM asuitable value to return should be –12dB Ec/No.

5.5 Size of neighbour list

When defining the neighbour lists one has to take into account;. the list should be as shortas possible to increase the chance of a successful handover and the cell coverage mightchange with the increase of load. However one has to keep in mind that CPICH Ec/No isused as measurement quantity for both idle mode and G2U active mode, although it mightbe of less importance to always reselect to the strongest cell in idle mode.


40/73




2006-03-286 PA1

5.6 U2G triggering: RSCP or Ec/No

The choice between the CPICH RSCP triggering criteria and the CPICH Ec/No criteria isabout deciding what kind of pros and cons are most important for the network. For thetested areas both CPICH RSCP with a threshold of –104dBm and CPICH Ec/No with athreshold of –13dB works well. However at certain locations one of the measurementquantities performs better than the other and vice versa.

To be able to safely let users handover to the 2G network when the quality is degradeddue to an increased interference situation the CPICH Ec/No has to be used as a

measurement quantity. However to have relatively safe handovers when moving out ofcoverage in a low load situation, a high value of Ec/No has to be used. A CPICH Ec/No of –11dB for the event 3a leads to secure Handovers to the 2G network in most placestested. The biggest drawback with this value is the reduced 3G coverage since the userwill leave the 3G network for the 2G network at levels where the connection can beremained with good quality if the signal strength is sufficient.

The table below sums the pros and cons with the two different measurement quantitiesassuming the threshold for event 3a set to –104 dBm for the RSCP case and –11 dB forthe Ec/No case.

CPICH Ec/No Triggering CPICH RSCP triggering Ensures that users experiencing

high interference are handed over

to 2G.

Stable at low and medium interference

scenarios

Balance the U2G and G2U cell

change with the FDDQMIN

parameter (avoid ping-pong). More time in 3G at medium interference

High threshold needed for stable

handovers when going out of

coverage.

Does not ensure that users experiencing

high interference are handed over to 2G. (i.

High Rise buildings, future load)

Ec/No used for G2U for PS (and CS) -

potential ping pong problems.

Slightly reduced coverage in low

signalstrength - low interference areas.

Pros

Reduced coverage in high signal

strength - medium interferenceareas.

Cons

5.7 Huawei recommendation

In order to ensure a high quality in the network at all locations Huawei initialrecommendation for the IRAT parameter setting in South Africa is to use the CPICH Ec/Nomeasurement quantity for the triggering as a long-term solution.


41/73




2006-03-286 PA1

It’s also possible to use as an intermediate solution the RSCP measurement quantity inisolated and low interfered areas. This indication is given because the RSCP measurementquantity in not really affected by interference problems due to UL or DL load, and becauseactually the network is not fully loaded. The biggest drawback that can be seen using thisstrategy is that after a certain amount of load in the network, the entire parameter settingsinitially “tuned” on the RSCP basis, need then to be reviewed on a CPICH EC/No level.

The recommended values are set as to ensure a high probability of successful U2Ghandovers both when moving out of coverage in coverage limited scenario and whenexperiencing a high level of interference.

5.8 Further studies

During this service the investigation was focused only on the IRAT HO parameters thathave a major impact in the network performance. Below is a list of suggested topics tostudy:

Indoor IRAT HO behaviour

CM starts triggered with UE Tx power (ueTxPowerThresh6a/ ueTxPowerThresh6b)

GSM vs. UMTS traffic load handling made by ISHOLEV parameter

It is suggested that more than one type of TEMS investigation terminal are used for furthertesting.


42/73




2006-03-286 PA1

6 Proposed parameter settings

This section contains the final proposed parameter settings that were evaluated accordingto the results obtained from the Validation phase.

The lists below show the proposed settings both if the Ec/No and if RSCP quantity aremeasured. In both cases, the proposed values for Idle Mode behaviour are added.

CPICH Ec/No

utranThresh3aEcno = -13 usedFreqThresh2dEcno = -12 usedFreqRelThresh2fEcno = 2 (-10) timeToTrigger2d = 11 (320 ms) timeToTrigger2f = 13 (1280 ms)

QSC = 8 (above -78dBm) QSI = 7 (always) MRSL = 29 (-9,5) FDDMRR = 2

sRatSearch = 4 (-14*) FDDQMIN = 7 (-12)

Assumed that qQualMin = -18

CPICH RSCP

utranThresh3aRscp = -104 usedFreqThresh2dRscp = -102 usedFreqRelThresh2fRscp = 3 (-99) timeToTrigger2d = 11 (320 ms) timeToTrigger2f = 13 (1280 ms)

QSC = 8 (above -78dBm) QSI = 7 (always) MRSL = 29 (-9,5) FDDMRR = 2

sRatSearch = 4 (-14*) FDDQMIN = 7 (-12)

bold = Huawei default/recommended value

The proposed parameter settings are not the only possible variation. In border cells areasit’s possible to start CM at higher values because e2d is triggered on a cell basis as well asthe sRatSearch parameter. This could give the UE the needed time to handover in time. Anadditional offset could be added for e2d (e.g. 1dB for Ec/No or 2dBm for RSCP).

If the users in CM are reaching a certain level per cell (e.g. 30%), the Admission Control Algorithm will deny the access to that cell. In fact Compressed mode has a higherprobability to be blocked by Admission Control or by RBS CE limitations -> Requested SoftHO during CM could be rejected, this might lead to a dropped call (release connectionoffset or RF synch lost). During compressed mode the usage of channel elements (CE) ishigher as well the transmitted power from the UE.

In case of using the RSCP strategy it is advisable to monitor the load in the system todetect the point of switching back to Ec/No. A drawback is as well that tuning activities


43/73

Ericsson Internal


EDD/IC/GA Michael Weber TEI/I/RFN Pierluigi Reda, ESA/SK 05:0144 Approved Checked Date Rev Reference

2006-03-28 PA1

during the RSCP phase may need to be re-done due to the different characteristics of themeasurement quantities.


44/73

Ericsson Internal



2006-03-28 PA1

Some rule to decide which measurement quantity could be used to trigger IRAT HO are:

Low load = RSCPMedium to high Load = Ec/No

Low to medium interference = RSCP

Medium to high interference = Ec/No

Isolated area = RSCP

High site density = Ec/No

Border cells = RSCP

Dense urban area = Ec/No

A possible separating for measurement quantity of the area for MTM South Africa could

be:

Ec/No Strategy RSCP Strategy

Pretoria Durban

Randburg Cape Town

Germiston

Bloemfontein (belongs to

GERNC)


45/73

Ericsson Internal



2006-03-28 PA1

7 Abbreviations

GPI Global Parameter Investigation

U2G UMTS to GSM

G2U GSM to UMTS

CM Compressed Mode

CR Cell Reselection

IRAT HO Inter Radio Access Technology Handover

IRAT CR Inter Radio Access Technology Cell Reselection

8 References

[1] 3GPP TS25.133 V4.15.0 (2005-06) (Release 1999)

[2] User Description, Handover 75/1551-HSD10102/1

[3] 3GPP TS 05.08 V8.17.0 (2003-06)


46/73

Ericsson Internal



2006-03-28 PA1

9 Appendix A - Initial phase results

9.1 Overview

The main scope of the Initial phase of the GPI service was to point out the 3G and 2Gnetwork parameters to test and to be investigated. Each parameter was chosenaccordingly to the major effects that a value change could have on both systems.Consequently, the first step was to define two different strategies concerning Ec/No andRSCP measured quantities for IRAT HO event triggering. In addition to this, a separatestrategy was arranged regarding the Idle Mode behaviour (U2G and G2U Cell reselection).

As a staring point, a certain number of Test Cases groups were created, in order to testeach single parameter (or sometimes a small set) both from RSCP and from Ec/No pointof view. The main scope was to figure out what could have been the best behavingparameter values for the next implementation inside the validation phase test cases.

Two different mobiles were used all along the drive tests (TEMS Nokia 6630 and TEMSSonyHuawei V800) in order to collect sufficient data for the analysis.

9.2 Test Case Group (U2G):

The U2G HO analysis was conducted on several parameters that have a major impact onthe IRAT U2G HO procedure: e2d, e2f, e3a, ttt2d and ttt2f.

It was also taken in account the number of ping-pong effects between e2d and e2f, inorder to have a complete figure on the system performance according to the differentparameter settings.

The main objective was to gather all the data coming from the initial phase and to decidewhich were the best behaving values to use for the validation phase Test Cases.

The two tables below (divided by Ec/No and RSCP strategy) show the behaving of e3atriggering during an IRAT HO procedure. The tested parameter was utranThresh3aEcno.The data that were used are referring to the threshold level when the e3a request shouldbe reported by the UE, the average time between e3a itself and the DL HO from UTRANcommand as well the average RSCP-Ec/No levels measured for the AS best serving cellwhen the event occurred.


47/73

Ericsson Internal



2006-03-28 PA1

Test Case Meas. Quantity e3ae3aTo HO

CommandTime As1EcNo As1RSCP

TC 1.1.1 6630 Ec/No -12 0,94 -13,40 -107,56

TC 1.1.1 V800 Ec/No -12 1,17 -13,50 -102,50

TC 1.1.2 6630 Ec/No -13 2,71 -13,00 -102,90

TC 1.1.2 V800 Ec/No -13 0,71 -12,50 -98,83

TC 1.1.3 6630 Ec/No -14 1,38 -12,57 -102,44

TC 1.1.3 V800 Ec/No -14 0,61 -14,25 -101,50

For the Ec/No strategy (table above) it was evident that the best behaving parametersetting was related to TC 1.1.2 and TC 1.1.3: even if the average time between e3a andthe DL HO from UTRAN command is floating, the average measured Ec/No and RSCPlevels for the AS best serving cell when the event occurred resulted consistent with theadopted event 3a triggering settings. The TC 1.1.1 settings were excluded due to thesignificant difference between these evaluated thresholds.

Following the same criteria, the analysis was conducted as well on the RSCP related test

cases. In this scenario, the best behaving test cases for the validation phase were TC1.1.7 and 1.1.8.

Test Case Meas. Quantity e3ae3aTo HO

Command Time As1EcNo As1RSCP

TC 1.1.6 6630 RSCP -102 0,91 -11,71 -102,79

TC 1.1.6 V800 RSCP -102 1,07 -11,80 -100,20

TC 1.1.7 6630 RSCP -104 1,03 -13,20 -106,22

TC 1.1.7 V800 RSCP -104 1,06 -11,57 -105,57

TC 1.1.8 6630 RSCP -105 0,72 -11,75 -106,03

TC 1.1.8 V800 RSCP -105 0,97 -12,50 -106,50

TC 1.1.9 6630 RSCP -106 0,90 -10,50 -105,10

TC 1.1.9 V800 RSCP -106 1,53 -14,50 -104,25

Regarding the parameter usedFreqRelThresh2f(Ec/No or RSCP), the main analysis wasconducted onto the ping-pong effects between the event 2f itself triggering and the event

2d. In this way is possible to have a good figure of the correct triggering of both events, interms of:


48/73

Ericsson Internal



2006-03-28 PA1

right start/stop CM during a call

e2d reporting from the UE to the system that correctly ends with an IRAT U2G HO

incorrect e2d/e2f reporting to the network (this means a misuse of the radioresource by the mobile, since both the events are triggered when not needed).

The tables below show the results coming from this analysis, divided again by Ec/No andRSCP strategy and sorted by UE. The ping-pong effect is taken into account if thesequence e2d-e2f-e2d is happening in a time interval shorter than 25 seconds per call.During the measurements a certain number of compressed mode ping-pong was detected,and it gave a first figure which test cases can be considered as the best behaving.

TC 1.1.1 e2f=2 TC 1.1.2 e2f=1 TC 1.1.3 e2f=3

V800 6630 V800 6630 V800 6630

Time Interval (s) Ping-Pong Ping-Pong Ping-Pong Ping-Pong Ping-Pong Ping-Pong

20 1 0 0 0 0 2

15 2 1 4 1 1 1

10 2 0 1 1 0 1

5 4 0 2 0 0 0

0 5 2 5 2 0 0

Ping Pong ratio 54,22 20,01 52,14 20,11 0,01 0,11

TC 1.1.6 e2f=5 TC 1.1.7 e2f=3 TC 1.1.8 e2f=2 TC 1.1.9 e2f=4

V800 6630 V800 6630 V800 6630 V800 6630

Time Interval (s) Ping-Pong Ping-Pong Ping-Pong Ping-Pong Ping-Pong Ping-Pong Ping-Pong Ping-Pong

20 1 0 0 0 0 0 0 0

15 1 0 0 0 0 1 0 0

10 0 0 0 2 0 1 0 0

5 1 0 0 0 0 0 1 3

0 1 0 2 1 2 0 0 0

Ping Pong ratio 11,01 0,00 20,00 10,20 20,00 0,11 1,00 3,00

An additional indication came from the analysis on the CM usage, both from Ec/No

perspective and from the RSCP point of view. In this case the charts below shows the ratioof total time spent from the UE in compressed mode.


49/73

Ericsson Internal



2006-03-28 PA1

CM usage (Ec/No)

0

20

40

60

80

100

6630 V800 6630 V800 6630 V800

TC 1.1.1 TC 1.1.2 TC 1.1.3

P e r c e n t a g e

CM ratio with NO HO

CM usage (RSCP)

0

20

40

60

80

100

6630 V800 6630 V800 6630 V800 6630 V800

TC 1.1.6 TC 1.1.7 TC 1.1.8 TC 1.1.9

P e r c e n t a g e

CM ratio with NO HO

It’s important to know that in this scenario a significant role is played also by the UE’sbehaviour, because the entire “CM start/stop” or “CM start / IRAT HO performing”procedures are depending from the different UE capabilities.

According to the explained methodology, for the validation phase the value for theparameter usedFreqRelThresh2fEc/No was chosen to 2; the corresponding one for RSCPwas indicated in 2 and 3.

For the e2d triggering (usedFreqThresh2dEcno/RSCP) the analysis was conducted takingin account the total distribution (Ec/No vs. RSCP) of all the samples collected when an e2d

request was reported by the UE. The charts below (Test Cases 1.2 group) show the datacoming from these measurements.


50/73

Ericsson Internal



2006-03-28 PA1

e2d (Ec/No, Thr -11 tested)

-120

-100

-80

-60

-40

-20

0

-25 -20 -15 -10 -5 0

Ec/No

R S C P

6630 V800

e2d (Ec/No, Thr -12 tested)

-120

-100

-80

-60

-40

-20

0

-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0

Ec/No

R S C P

6630 V800

From the charts above it’s evident that both of the tested thresholds are consistent with acorrect e2d triggering, because the e2d reporting itself is happening in most of the cases atthe predefined Ec/No levels, so both the values –11dB and –12dB for Ec/No strategy wereadopted for the validation phase.

Also in this scenario it’s very clear the different UE behaviour, and the V800 showed abetter performance than the 6630.

-11 dB


51/73

Ericsson Internal

TECHNICAL REPORT 51 (73)Prepared (also

Documents

Sqi vs Rxqual