3g irat idle mode and parameter setting-libre

3G Irat, IDLE MODE and

parameter setting

China unicom3g, Shanxi.

© Ericsson AB 2010 Ericsson Internal 2010-01-072

Contents

1. Introduction

2. Pre-requisite

3. IRAT operation

4. Key parameter of IRAT handover

5. Key parameter of Idle Mode Cell Reselection

6. Drive test introduction

a. Drive test detail

b. Scenario 1 – Cell reselection from WCDMA to GSM

c. Scenario 2 – IRAT Handover from WCDMA to GSM

d. Scenario 3 – IRAT Cell Change and Cell Reselection from WCDMA to GSM

7. Conclusion


introduction

› This slide is to explain the 3G/2G inter-operational that Ericsson conducted in

China Unicom 3G, Tai Yuan, Shan Xi province.

› The slide is mainly to explain basic function, drive test cases, how does the

setting impact to the IRAT handover as well as IRAT drive test samples.

› The document shall provide some suggestion on the most suitable IRAT

setting at the end of the document.


PRE-Requisite

› Prior to test on the IRAT. There are some data and information need to be checked and data consistency has played a major role in performing IRAT handover and cell reselect from WCDMA to GSM successfully.

› External GSM NB defined in RNC must be consistent with BSC. Below are some of the information that we need to check:

– CI

– LAC

– BCCH

– BSIC (NCC + BCC)

› Pre-defined IRAT parameters in RNC shall be checked according.


IRAT Operation

› 3G/2G inter-operationality can be mainly divided into 2 section.

– Idle Mode

› UE could be reselect from WCDMA to GSM in idle mode and vice versa.

– Connected Mode

› UE could be perform IRAT handover from WCDMA to GSM at CELL_DCH.


Key parameter for irat HANDOVER-1/4

Measurement Quantity(Ec/No and RSCP)

WCDMA cell

GSM cell

usedFreqTresh2fEcno

usedFreqTresh2dEcnohysteresis2d/2

hysteresis2f/2

hysteresis2d/2

utranRelTresh3aEcno

gsmTresh3a

hysteresis3a/2

Reporting event 2d

Reporting event 2d

Reporting event 2f

Reporting event 3a

› Below is the graph to show the Event 2d, Event 2f, and Event 3a.



› Below are some of the key parameter involved in the IRAT handover.

0Speech=0,

PS=-2,

HS=-20

-20 to

20

Offset per UeRc-state that is added to the 2d, 2f, 3a

and 2b Ec/No thresholds. Coverage trigger offset per

UeRc.

serviceOffset2dEcNo

-12dB-12dB-24 to 0Threshold for event 2d (the estimated quality of the

currently used WCDMA RAN frequency is below a

certain threshold). Used if measurement quantity is

configured to be Ec/No.

usedFreqThresh2dEcNo

-100dBm-104dBm-115 to

-5

Threshold for event 2d (the estimated power level of

the currently used WCDMA RAN frequency is below

a certain threshold). Used if measurement quantity is

configured to be RSCP.

usedFreqThresh2dRscp

0Speech=0,

PS=-3,

HS=0

-50 to 50Offset per UeRc-state that is added to the 2d, 2f, 3a

and 2b Ec/No thresholds. Coverage trigger offset per

UeRc.

serviceOffset2dRSCP

0dB0dB0 to

14.5dB

Hysteresis used for event 2d.hysteresis2d

320ms320ms0, 10,

20,…,

320,….,

5000ms

Interval time between detection of event 2d and

sending of the measurement report, when the

measurement quantity is CPICH EC/NO. If event 2d

condition is fulfilled during at least a time greater than

or equal to timeToTrigger2dEcno milliseconds, then

event 2d occurs. A setting of 5000 disables the 2d

Ec/No measurement.

timetotrigger2dEcNo

Default Setting

Current

Setting

RangeDefinitionParameter Name



2dB2dB0 to 20Relative threshold for event 2f versus event 2d. The

estimated quality of the currently used WCDMA RAN

frequency is above a certain threshold +

usedFreqThresh2dEcno .

usedfreqRelThresh2fEcno

0dB0dB0 to

-14.5

Hysteresis used for event 2f.hysteresis2f

1280ms1280ms0; 10;

20;…….

1280;….

2560,.

5000 ms

Interval time between detection of event 2f and

sending of the measurement report, when the

measurement quantity is CPICH EC/NO. If event 2f

condition is fulfilled during at least a time greater than

or equal to timeToTrigger2fEcno milliseconds, then

event 2f occurs.

timetotrigger2fEcno

3dB3dB0 to 20Relative threshold for event 2f versus event 2d. The


frequency is above a certain threshold +

usedFreqThresh2dRscp

usedfreqRelThresh2fRscp

Default Setting

Current

Setting




-1dB0dB-10 to 10Relative threshold for event 3a versus event 2d (the


frequency is below a certain threshold +

usedFreqThresh2dEcno and the estimated quality

of the GSM system is above a certain threshold in the

same time interval) for WCDMA RAN, when the 2d

measurement quantity is CPICH Ec/No.

utranRelThresh3aEcno

-3dB0dB-20 to 20Relative threshold for event 3a versus event 2d (the

estimated power level of the currently used WCDMA

RAN frequency is below a certain threshold +

usedFreqThresh2dRscp and the estimated power

level of the GSM carrier is above a certain threshold

in the same time interval) for WCDMA RAN, when the

2d measurement quantity is CPICH RSCP.

utranRelThresh3aRscp

100ms100ms0; 10;

20;..

100;…

1280;…

2560;….

5000 ms

Interval time. If event 3a condition is fulfilled during at

least a time greater than or equal to timeToTrigger3a

milliseconds, then event 3a occurs.

timetotrigger3a

-95dBm-95dBm-115 to 0Threshold for event 3a (the estimated quality of the

currently used WCDMA RAN frequency is below a

certain threshold and the estimated quality of the

GSM system is above a certain threshold) for GSM.

gsmThresh3a

0dB0dB0 to

7.5dBHysteresis used for event 3a.

hysteresis3a

Default Setting

Current

Setting



Key parameter for IDLE RESELECTION-1/2

› Below is the graph to show the threshold for cell reselection from GSM to WCDMA.


Key parameter for IDLE RESELECTION-2/2

› This is the cell reselection parameter during idle mode.

4dB4dB-32..20Decision on when measurements on GSM neighbors

are performed which is made using this parameter in

relation with Squal. The parameter is defined per cell.

sRatsearch

-18dB-18dB-24..0

[step

1dB]

Minimum required quality level in the cell measured in

the UE. The parameter is defined per serving cell and

per WCDMA neighbor.

qQualmin

-115dBm-115dBm-115..-

25; 100

(not

sent)

Minimum signal strength level received in the UE.

The parameter is defined per serving cell and per

WCDMA neighbor and GSM neighbor.

qRxlevmin

4dB4dB0..40Hysteresis value of the serving cell to be used for cell

ranking.

qHyst1s

0dB0dB-50..50Signal strength offset between source and target cell

to be used for cell ranking based on CPICH RSCP or

EcNo. The parameter is defined per WCDMA

neighbor relation and per GSM neighbor relation.

qOffset1n

2s2s0..31Reselection time control of cell selection and

reselection. The time-to-trigger for cell reselection

occurs in seconds. The parameter is defined per cell.

treSelection

Default Setting

Current

Setting


DriVE TEST

introduction


Drive test detail

There are 3 scenario drive tests shall be done on idle mode, connected mode on

CS and PS services respectively:

› Idle mode to reselect from WCDMA to GSM.

› CS12.2 drive test from WCDMA site towards IRAT border.

› HSDPA PS call was done from WCDMA site to the IRAT border area.


Drive route detail

› Blue arrow line to show the

direction of the IRAT

handover and idle mode cell

reselection tests were carried

out.

› The drive route was located

along 太茅路 from 小店 south

bound to 桥家大院。


Scenario 1: Idle mode cell reselection from WCDMA TO

GSM – 1/2

› Sratsearch was configured at 0dB, it can be found from SIB3, Layer3 messages.

› Idle mode cell reselection from WCDMA happened at EcNo = -21dB.


Scenario 1: Idle mode cell reselection from WCDMA TO

GSM – 2/2

› Sratsearch was configured at 4dB, it can be found from SIB3, Layer3 messages.

› Idle mode cell reselection from WCDMA happened at EcNo = -15.5dB.


Scenario 2: irat handover from wcdma to gsm – 1/3

› Drive test was carry out with the parameter setting; usedfreqthresh2dEcno = -12dB, usedfreqthresh2dRscp = -104dBm that were configured at the tested utrancells.

› Event2d triggered at EcNo=-12dB.

› Event3a occurs at EcNo=-12.5dB, RSCP=-102dBm.

› From measurement report, the gsm-Carrier RSSI has recorded -66dBm.

› Targeted GSM with ARFCN@CH113 to be IRAT handover from WCDMA at event3a has fulfilled better than gsmthresh3a = -95dBm, and worse than usedFreqThresh2dEcno+ utranRelThresh3aEcno = -12+0dB = -12dB.

Measurement control



› Drive test was carry out with the parameter setting; usedfreqthresh2dEcno = -16dB, usedfreqthresh2dRscp = -100dBm that were configured at the tested utrancells.

› Event2d triggered at RSCP=-100dBm.



› Targeted GSM with ARFCN@CH113 to be IRAT handover from WCDMA at event3a has fulfilled better than gsmthresh3a = -95dBm, and worse than usedFreqThresh2dRscp+ utranRelThresh3aRscp = -100+0dBm = -100dBm.

Measurement control



› Drive test was carry out with the parameter setting; usedfreqthresh2dEcno = -12dB, usedfreqthresh2dRscp= -100dBm that were configured at the tested utrancells.

› Event2d triggered at EcNo=-102dBm.




› Multiple IRAT handover failure were encountered due to IRAT physical channel failure.

Measurement control


Scenario 3: irat CELL Change from wcdma to GPRS – 1/2

› Drive test was carry out with the parameter setting; usedfreqthresh2dEcno = -12dB, usedfreqthresh2dRscp = -104dBm, serviceOffset2dEcNo=-2dB for PS, -20dB for HS and serviceOffset2dRscp=-3dB.

› Event2d triggered at EcNo=-12dB.

› Event3a occurs at EcNo=-13dB, RSCP=-102dBm.



› IRAT Cell Change has been triggered mainly due to parameter’ poorqualitydetected = ON

Measurement

control


Scenario 3: irat CELL Change from wcdma to GPRS – 2/2

› Drive test was carry out with the parameter setting; usedfreqthresh2dEcno = -16dB, usedfreqthresh2dRscp = -100dBm, serviceOffset2dEcNo=-2dB for PS, -20dB for HS and serviceOffset2dRscp=-3dB.

› Neither Event2d nor Event3a triggered due to HS was not suppose to handover to GPRS due to the strategy required by China Unicom.

› Finally, UE goes to idle mode and cell reselection to GPRS. › GPRS was initiated at GSM with ARFCN 113, BSIC 33.› IRAT Cell Change does not occurs due to parameter’ poorqualitydetected = OFF

Measurement

control


CONCLUSION

With the multiple combination of the drive test setting either in idle mode, or

connected mode. It is recommended to configure the below setting for

smooth IRAT handover transition, better overall network throughput and as

well as network KPI.

› Recommend to configure Sratsearch = 4

› usedfreqthresh2dEcno = -12dB

› usedfreqthresh2dRscp = -104dBm

› Mobility phase 2: HStoDchTrigger: poorqualitydetected = OFF

It is recommended to switch OFF the poorqualitydetected parameter mainly

to provide the better DL throughput to the subscriber while mobilised, to

improve the PS DCR as not every UE was support the HS downswitch to

Cell_DCH due to poorqualitydetected feature enabled.

3g irat idle mode and parameter setting-libre

Documents

ericsson internal

g irat

suitable irat

irat operation4

irat cell change

dreporting event

conclusion ericsson

freporting event