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© 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
© Ericsson AB 2010 Ericsson Internal 2010-01-073
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.
© Ericsson AB 2010 Ericsson Internal 2010-01-074
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.
© Ericsson AB 2010 Ericsson Internal 2010-01-075
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.
© Ericsson AB 2010 Ericsson Internal 2010-01-076
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.
© Ericsson AB 2010 Ericsson Internal 2010-01-077
Key parameter for irat HANDOVER-2/4
› 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
© Ericsson AB 2010 Ericsson Internal 2010-01-078
Key parameter for irat HANDOVER-3/4
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
estimated quality of the currently used WCDMA RAN
frequency is above a certain threshold +
usedFreqThresh2dRscp
usedfreqRelThresh2fRscp
Default
Setting
Current
Setting
RangeDefinitionParameter Name
© Ericsson AB 2010 Ericsson Internal 2010-01-079
Key parameter for irat HANDOVER-4/4
-1dB0dB-10 to 10Relative threshold for event 3a versus event 2d (the
estimated quality of the currently used WCDMA RAN
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
RangeDefinitionParameter Name
© Ericsson AB 2010 Ericsson Internal 2010-01-0710
Key parameter for IDLE RESELECTION-1/2
› Below is the graph to show the threshold for cell reselection from GSM to WCDMA.
© Ericsson AB 2010 Ericsson Internal 2010-01-0711
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
RangeDefinitionParameter Name
© Ericsson AB 2010 Ericsson Internal 2010-01-0713
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.
© Ericsson AB 2010 Ericsson Internal 2010-01-0714
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。
© Ericsson AB 2010 Ericsson Internal 2010-01-0715
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.
© Ericsson AB 2010 Ericsson Internal 2010-01-0716
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.
© Ericsson AB 2010 Ericsson Internal 2010-01-0717
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
© Ericsson AB 2010 Ericsson Internal 2010-01-0718
Scenario 2: irat handover from wcdma to gsm – 2/3
› 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.
› Event3a occurs at EcNo=-12.5dB, RSCP=-99dBm.
› From measurement report, the gsm-Carrier RSSI has recorded -74dBm.
› 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
© Ericsson AB 2010 Ericsson Internal 2010-01-0719
Scenario 2: irat handover from wcdma to gsm – 3/3
› 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.
› Event3a occurs at EcNo=-13.5dB, RSCP=-101dBm.
› From measurement report, the gsm-Carrier RSSI has recorded -69dBm.
› 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.
› Multiple IRAT handover failure were encountered due to IRAT physical channel failure.
Measurement control
© Ericsson AB 2010 Ericsson Internal 2010-01-0720
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.
› From measurement report, the gsm-Carrier RSSI has recorded -75dBm.
› 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.
› IRAT Cell Change has been triggered mainly due to parameter’ poorqualitydetected = ON
Measurement
control
© Ericsson AB 2010 Ericsson Internal 2010-01-0721
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
© Ericsson AB 2010 Ericsson Internal 2010-01-0722
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.