Telkomsel LTE FDD Interworking Strategy_V1.1

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www.huawei.com

Telkomsel LTE

Interworking Strategy

(LTE900 + UMTS + GSM)

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Document Revision Record

Date

Versio

n

Description

Remark

Author

22/8/2014 1.0 Initial Version Yeoh Yee Chin (HW)

Remark:

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Overview of Interworking Strategy

Idle Mode

• L900  L900: Intra-frequency reselection based on coverage

• L900  U2100/G1800/G900: Reselection based on coverage

• U2100/G1800/G900  L900: Reselection based on priority

Coverage Trigger Priority Trigger

L900

LTE 900

Cell C

Cell B

Cell A

UMTS 2100

GSM 1800/900

F1 U2100

F2 U2100

F3 U2100

UMTS 2100

• Note: LTE<-> DCS1800 relationship will be defined in Inner City and LTE <-> GSM900 will be

defined in outer city.

G1800/900

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Overview of Interworking Strategy

Connected Mode

• L900  L900: Intra-frequency handover based on coverage

• L900  U2100/G1800/G900: Inter-RAT PS Handover/redirection for PS service, CSFB by

redirection for CS service

• U2100/G1800/G900 L900: Redirection for PS Service

L900

LTE 900

Cell C

Cell B

Cell A

UMTS 2100

F1 U2100

F2 U2100

F3 U2100

Coverage Based

U->L Fast Return (SRAN8.0 above)

UMTS 2100

CSFB

⃰ Note: LTE<-> DCS1800 relationship will be defined in Inner City

and LTE <-> GSM900 will be defined in outer city.

G1800/900

GSM 1800/900*

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LTE<->LTE Intra-Freq – Idle Mode Cell Reselection

• Intra-frequency cell reselection is triggered when UE moves out of the serving cell coverage

area.

• UE starts intra-frequency measurements if:



S

_ServingCell

≤ S

_IntraSearch

• Condition of cell-ranking for the serving cell and neighboring cells:



R

_s

= Q

_meas,s

+ Q

_hyst



R

_n

= Q

_meas,n

– CellQ

_offset

• Condition of cell reselection:



The new cell is ranked higher than the serving cell, R

_n

> R

_s

for a time period of T

_ReselEutran

.



The UE has camped on the serving cell for more than 1second.

L900

LTE

900 LTE

900 Cell C

Cell B

Cell A

Coverage Trigger RS RP Time QRxLevMin -128dBm TReselEutran

Trigger cell reselection

Qmeas,s Qmeas,n Qmeas,s+Qhyst ● - 70dBm SIntraSearch Rn > Rs

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LTE<->LTE Intra-Freq – Idle Mode Cell Reselection

LTE Parameter MML

Command Default value

Recommend value Comments SIntraSearchCfgI nd MOD CELLRESEL CFG Range: NOT_CFG, CFG CFG (configure)

Enable the measurement triggering threshold for intra-frequency cell search

SIntraSearch 29 Range: 0~31 Unit: 2dB 29 [2dB] (-70dBm)

Measurement triggering threshold for intra-frequency cell reselection

Absolute value = 2*QRxLevMin + 2*SIntraSearch (=2*-64 + 2*29 = -128+58= -70dBm)

Qhyst

4 Range: 0~24

Unit:dB

DB4_Q_HYST Hysteresis value for ranking criteria

QRxLevMin

-64 Range: -70~-22

Unit: 2dBm

-64 [2dBm]

(-128dBm) Minimum required RSRP level

TReselEutran

1 Range: 0~7

Unit: s

1 [s] Timer value for EUTRAN cell reselection

QRxLevMin MOD CELLSEL

-64 Range: -70~-22

Unit: 2dBm

-64 [2dBm] (-128dBm)

Minimum required RSRP level for the cell to become a candidate for cell selection

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Inter-RAT – Idle Mode Cell Reselection

• Propose to set L900 to higher reselection priority than U2100 & GSM1800/900.

• LTE capable UE always prefer to camp on LTE due to higher cell priority than UMTS/GSM.

• UE performs cell reselection to F1 U2100 only when LTE signal is low and UMTS signal fulfill the

cell reselection triggering threshold.

• Absolute priority will be set for both LTE and UMTS network to facilitate cell reselection preference

to LTE network. It is not possible to set the same priority for LTE and UMTS network. Absolute

priority is broadcasted in the SIB message and it affects cell reselection process.

• Absolute priority ranges from 0 to 7, where 7 indicate the highest priority and 0 indicate the lowest

priority.

Priority

Telkomsel

System

7 6 LTE 5 4 UMTS 3 2 1 GSM

0 Range use for GSM

Range use for UMTS

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Inter-RAT – Idle Mode Cell Reselection

Reselection from L900 to U2100 Lower Priority Cell

• UE starts inter-RAT measurements if :



S

_ServingCell

≤ S

_{NonIntraSearch}

• UE performs cell reselection to U2100 lower priority inter-RAT cell when all the following

conditions are met:



No cell meets the criteria for reselection to higher priority cells



S

_ServingCell

< Thresh

_serving,Low

for a time period of TReselUTRAN.



S

_{NonServingCell,x}

> Thresh

_x,Low

for a time period of TReselUTRAN.



The UE has camped on the serving cell for more than 1second.

RS RP Time QRxLevMin -128dBm TReselUTRAN

S_ServingCell LTE S_{NonServingCell,x} U2100 (RSCP) - 114dBm SNonIntraSearch - 114dBm - 103dBm ● Threshserving,Low Threshx,Low

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Inter-RAT – Idle Mode Cell Reselection

Reselection from U2100 to L900 Higher Priority Cell

• If different reselection priority are set for different LTE frequency, then UE will search for

the highest priority frequency, if no suitable cell then select second priority frequency.

• UE performs cell reselection to a higher priority inter-frequency cell when all the following

conditions are met:



S

_{NonServingCell,x}

> ThdToHigh for a time period of TResel.



The UE has camped on the serving cell for more than 1second.

RS RP Time QRxLevMin -128dBm TResel

SServingCell U2100

S_{NonServingCell,x} L900

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LTE Parameter MML Command Default value Recommend value Comments CellReselPriority MOD CELLRESEL 1 Range: 0~7 6 for L900

Cell reselection priority of the serving frequency. L900 has higher priority than U2100. SNonIntraSearch CfgInd CFG Range: NOT_CFG, CFG CFG (configure)

Enable the measurement triggering threshold for frequency or inter-RAT cell reselection

SNonIntraSearch 10 Range: 0~31 Unit: 2dB 7 [2dB] (-114dBm)

Measurement triggering threshold for inter-frequency or inter-RAT cell search

Absolute value = 2*QRxLevMin + 2*SNonIntraSearch (=2*-64+2*7 = -128+ 14= -114dBm) ThreshServLow 10 Range: 0~31 Unit: 2dB 7 [2dB] (-114dBm)

Triggering threshold for inter-frequency or inter-RAT cell reselection to a cell on lower priority frequency

Absolute value = 2*QRxLevMin + 2*ThreshServLow (=2*-64+2*7 = -128 + 14= -114dBm) QRxLevMin MOD CELLSEL -64 Range: -70~-22 Unit: 2dBm -64 [2dBm] (-128dBm)

Minimum required RSRP level for the LTE cell to become a candidate for cell selection

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LTE Parameter MML Command Default value Recommend value Comments CellReselPriorityC fgInd ADD UTRANNFREQ NOT CFG Range: NOT_CFG, CFG CFG

(configure) Enable the inter-RAT cell reselection priority

CellReselPriority 1

Range: 0~7 4 for UMTS Cell reselection priority of the neighboring UTRAN frequency.

ThreshXLow 6 Range: 0~31 Unit: 2dB 6 [2dB] (-103dBm)

Minimum RSCP level required for neighboring UTRAN cell to become a candidate for reselection if the priority of the UTRAN frequency is lower than or equal to that of the serving frequency

Absolute value = (2*QRxLevMin + 1) + 2*ThreshXLow [((2*-58+1)+2*6)= -115 + 12= -103dBm]

PmaxUTRAN

33 Range: -50~33

Unit: dBm

24 [dBm] Maximum allowed UE transmission power in UTRAN

QRxLevMin -58 Range: -60~-13 Unit: 2dBm -58 [2dBm] (-115dBm)

Minimum required RSCP level Absolute value = 2*QRxLevMin + 1 (2*-58+1= -116+1= -115dBm) TReselUTRAN ADD CELLRESELUT RAN 1 Range: 0~7 Unit: s

1 [s] Timer value for LTE to UTRAN cell reselection

LTE -> UMTS Inter-RAT – Idle Mode Cell Reselection

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UMTS Parameter MML Command Default value

Recommend

value Comments

SPriority MOD

UCELLSELRESEL 4 4 for U2100 U2100 has lower priority than L900 SibCfgBitMap

ADD UCELLSIBSWITC

H

SIB19-0 SIB19-1 Enable UTRAN send SIB19 messages to UE for UMTS to LTE reselection

NodeBProtclVer MOD UNODEB NA R9 Set NodeB protocol version to R9. If lower than R8, then U2L interworking feature may not working

NPriority

ADD UCELLNFREQPRI

OINFO

NA

Range: 0~7 6 LTE cell reselection priority

ThdToHigh 2 Range: 0~31 Unit: 2dB 9 [2dB] (-110dBm)

RSRP level required for LTE neighboring cell to become a candidate for reselection if the priority of the frequency is higher than that of the serving frequency

Absolute value = 2*EQrxlevmin + 2*ThdToHigh (128 +18= -110dbm) EQrxlevmin -70 Range: -70~-22 Unit: 2dBm -64 [dBm]

(-128dBm) Minimum required RSRP level

UMTS -> LTE Inter-RAT – Idle Mode Cell Reselection

• In the UMTS network, SIB19 includes the absolute priority of the serving cell and the absolute priority of

each LTE frequency. When an LTE frequency has a higher absolute priority than the serving cell, the UE

reselects an LTE cell on this frequency if other additional conditions for LTE cell reselection are also met.

When the absolute priority of each LTE frequency is lower than that of the serving cell, the UE reselects

another UMTS cell if other additional conditions for UMTS cell reselection are also met.

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Recommend value Comments CellReselPriorityCfgI nd ADD GERANNFREQ GROUP(All GERAN carriers within LTE coverage area) 1 1 for

GSM1800/900 Enable the cell reselection priority configuration

CellReselPriority CFG CFG

(configure) GERAN priority is the lowest

ThreshXLow 7 Range: 0~31 Unit: 2dB 7 [2dB] (-99dBm)

Rx signal level threshold used in reselection to neighboring cells on a lower priority GERAN frequency

2*QRxLevMin+2*ThreshXLow (-113 + 7*2 = -99dBm) QRxLevMin 0 Range: 0~45 Unit: 2dBm 1 [2dB] (-113dBm)

Minimum RSSI level to camp on GERAN

2*QRxLevMin-min QRxLevMin(1*2 -115+= -113dBm) TReselGeran ADD CELLRESELG ERAN 1 Range: 0~7 Unit: s

1s Cell reselection duration of GERAN cell reselection

LTE -> GSM Inter-RAT – Idle Mode Cell Reselection

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GERAN Parameter MML Command Default value Recommend value Comments GERANPRI SET GCELLPRIEUTRAN SYS (All GERAN carriers within LTE

coverage area)

1 Range:

0~7

1 GERAN priority is the lowest (Always look for LTE)

EUTRANPRI

6 Range:

0~7

6 LTE cell reselection priority

EUTRANQRXLEVM IN 6 Range: -78~-140 6

(-128dBm) Minimum RSRP level to camp on LTE

THREUTRANHIGH 20

Range: 0~31

9 [2dB] (-110dBm)

If the measured RSRP value of one or more neighboring EUTRAN cells is higher than the value of this parameter, the MS is allowed to reselect a neighboring cell in

EUTRAN whose priority is higher than the GERAN priority. SPTRESEL

ADD GLTENCELL(All GERAN carriers)

Support Support Support cell reselection to LTE cell

GSM -> LTE Inter-RAT – Idle Mode Cell Reselection

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LTE Event for handover/redirection

Event

Meaning

A1

Serving becomes better than threshold

A2

Serving becomes worse than threshold

A3

Neighbor becomes offset better than serving

A4

Neighbor becomes better than serving

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LTE<->LTE Intra-Freq Handover

• Intra-frequency handovers are triggered by event A3.

• When the signal quality in at least one intra-frequency neighboring cell meets the configured

triggering condition of event A3, the UE sends the measurement result to the eNodeB.

• Event A3 entering condition:



Mn + Ofn + Ocn

– Hys > Ms + Ofs + Ocs + Off

• Event A3 leaving condition:



Mn + Ofn + Ocn + Hys < Ms + Ofs + Ocs + Off

L900

LTE

900 LTE

900 Cell C

Cell B

Cell A

Coverage Based

Parameter Value Description

Mn N/A Obtained from UE’s RSRP Measurement of neighbouring intrafreq LTE cells

Ofn 0 Frequency specific offset of the frequency of the neighbour cell

Ocn 0 Cell specific offset of the neighbour cell

Hys 4 Hysteresis parameter for this event. Actual value = IE value * 0.5 (dB)

Ms N/A Obtained from UE’s RSRP Measurement of serving LTE cell

Ofs 0 Frequency specific offset of the serving frequency

Ocs 0 Cell specific offset of the serving cell

RS RP Time TimeToTrigger Event A3 is triggered Ms Mn ●

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LTE<->LTE Intra-Freq Handover

Recommend value Comments IntraFreqHoA3Hyst MOD INTRAFREQ HOGROUP 2 Range: 0~30 Unit: 0.5dB 2

(1dB) Intra-frequency handover hysteresis for event A3

IntraFreqHoA3Offset

2

Range: -30~30 Unit: 0.5dB

2

(1dB) Intra-frequency handover offset for event A3

IntraFreqHoA3TimeToTrig 320

Range: 0~5120ms 320 [ms] Intra-frequency handover time-to-trigger for event A3 IntraFreqHoA3TrigQuan MOD INTRARATH OCOMM RSRP Range: RSRP, RSRQ

RSRP A3 measurement trigger quantity

IntraFreqHoA3RprtQuan RSRP Range: SAME_AS_TRIG_ QUAN(Same as Trig Quan)

RSRP A3 measurement report quantity

IntraFreqHoRprtInterval

240

Range:120ms-60min

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LTE -> UMTS Inter-RAT – PS Connected

• In a coverage-based inter-RAT redirection, event A2 triggers inter-RAT measurements:



Entering condition: Ms + Hys < Thresh



Leaving condition: Ms – Hys > Thresh

• In a coverage-based inter-RAT redirection, event A1 stops inter-RAT measurements:



Entering condition: Ms – Hys > Thresh



Leaving condition: Ms + Hys < Thresh

• The triggering of event B1 indicates that at least one neighboring cell signal quality is higher than

specified threshold:



Entering condition: Mn + Ofn

– Hys > Thresh



Leaving condition: Mn + Ofn + Hys < Thresh

Thresh -103

dBm Threshold for B1 event trigger

Mn N/A Obtained from UE Measurement

Ofn 0 Frequency specific offset of the frequency of the neighbour cell

Hys 2

B1 Hysteresis。

Actual value = IE value * 0.5 (dB) Actual value = 1 dB

InterRatHoUtra nB1TimeToTrig

640

ms Time To Trigger

Ms N/A Obtained from UE Measurement. RSRP

Thresh -116 dBm

(RSRP) Threshold for A2 event

Hys 2

A1A2 Hysteresis.

Actual value = IE value * 0.5 (dB) Actual value = 1 dB

InterFreqHoA1

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LTE -> UMTS Inter-RAT – PS Redirection

LTE Parameter MML Command Default value Recommend

value Comments HoModeSwitch MOD ENODEBALGOS WITCH UtranRedirectS witch:Off UtranRedirectS

witch:On Enable redirection from LTE to UTRAN switch UtranPsHoSwitc

h:Off

UtranPsHoSwitc

h:Off Enable PS handover from LTE to UTRAN switch InterRatHoA1A2TrigQuan MOD INTERRATHOCO MM RSRP Range: RSRP, RSRQ, BOTH

RSRP Inter-RAT A1/A2 measurement trigger quantity

InterRatHoUtranB1Meas Quan

UTRAN_RSCP Range: RSCP,

ECN0, BOTH

RSCP UTRAN measurement trigger quantity

InterRatHoA1ThdRsrp ADD INTERRATHOCO MMGROUP -111 Range: -141~-43 Unit: dBm

-111 [dBm] RSRP threshold for inter-RAT measurement event A1

InterRatHoA2ThdRsrp

-115 Range: -141~-43

Unit: dBm

-115 [dBm] RSRP threshold for inter-RAT measurement event A2

InterRatHoA1A2Hyst

2 Range: 0~30

Unit: 0.5dB

2

(1dB) Hysteresis for inter-RAT measurement event A1/A2

InterRatHoA1A2TimeToT rig

640 Range: 0ms~5120ms

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LTE -> UMTS Inter-RAT – PS Redirection

LTE Parameter MML Command Default value Recommend

value Comments InterRatHoUtranB1Thd Rscp ADD INTERRATHOU TRANGROUP -103 Range: -120~-25 Unit: dBm

-103 [dBm] RSCP threshold for event B1 related to coverage-based inter-RAT HO to UTRAN

InterRatHoUtranB1Hyst 2 Range: -120~-25 Unit: dBm 2 [0.5dB]

(1dB) Hysteresis for inter-RAT HO event B1

InterRatHoUtranB1Time ToTrig

640 Range:

0ms-5120ms

640 [ms] Time-to-trigger for inter-RAT HO event B1

BlindHoPriority ADD UTRANNCELL 0 Range: 0~32 32 for co-locate U2100 cell 0 for other cells

Configure co-locate U2100 F1 cell as blind HO neighboring cell to comply the UE that do not support UTRAN measurement.

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LTE -> GSM Inter-RAT – PS Redirection

value Comments HoModeSwitch MOD ENODEBALGOSW ITCH GeranRedirect Switch-0 GeranRedirect

Switch-1 Enable Redirection to GERAN switch GeranPsHoSwi

tch-0

GeranPsHoSwi tch-0

Enable PS handover to GERAN switch only in future if UE support L2G HO

BlindHoSwitch-0

Disable blind handover switch, take L2G redirection based on measurement BlindHoPriority ADD GERANNCELL 0 Range: 0~32 32 for co-locate G1800/900 cell, 0 for other neighbor cell

Configure GERAN as blind handover neighboring cell InterRatHoGeranB1T hd ADD INTERRATHOGER ANGROUP -95dBm Range: -110~-48 Unit: dBm

-95dBm RSSI threshold for event B1 that is used in HO to GERAN InterRatHoGeranB1Ti meToTrig 640ms Range: 0ms~5120ms

640ms Time to trigger for event B1 related to inter-RAT handover to GERAN

InterRatGeranB1Hyst

1dB Range: 0~30

Unit: 0.5dB

1dB Hysteresis for event B1 related to inter-RAT handover to GERAN

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CS Fallback (CSFB)

• CSFB (CS Fallback Function) is specified by ETSI TS 123 272 v10.6.0 and is a mandatory

requirement which supports “traditional” CS voice in LTE networks prior to IMS (IP

Multimedia Subsystem) deployment.

• In the overlaid coverage of LTE and UMTS, UMTS provides voice service for the multi-mode

UE. When CSFB voice service is initiated, the LTE data service will be handed / redirected

over to UMTS network.

• The benefit of having CSFB is that voice service can be deployed quickly reusing traditional

UMTS core with no additional equipment, thus saving on cost and minimizing new

investment.

• In addition, it also guarantees users data service continuity when re-direction or handover of

the PS service occurs.

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CSFB to UMTS (PS RRC Redirection)

MO call (R8: without RIM)

MME RNC

eNodeB

UE MSC SGSN

2.S1-AP Message with CS Fallback Indicator 1.Extended Service Request

(containing a CS Fallback Indicator)

S1-AP Reponse Message

3.Optional measurement report

5. LAU, combined RAU/LAU, or RAU and LAU

6.CS call establishment procedure S1 UE context release

4. RRC Connection Release with UTRAN frequency

MME RNC

eNodeB

UE MSC SGSN

2.S1-AP Message with CS Fallback Indicator 1.Extended Service Request

(containing a CS Fallback Indicator)

S1-AP Reponse Message 3.Optional measurement report

5. LAU, combined RAU/LAU, or RAU and LAU

6.CS call establishment procedure S1 UE context release

4. RRC Connection Release with UTRAN frequency\cell id\cell System information

MO call (R9: with RIM, Flash CSFB)

(

RIM: RAN Information Management

)

* MT call’s procedure is similar.

* R8 CSFB is adapted in Telkomsel LTE network

PS Suspend PS Suspend

*If the handover switch is turned from E-UTRAN to UTRAN, and UE support the handover, then LOFD-001052 Flash CS Fallback to UTRAN for the UE will be disabled.

That is, all Inter-RAT procedures to the UTRAN including CSFB will preferentially be performed based on handovers if handovers to the UTRAN is enabled and UEs are capable of such handovers.

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LTE -> UMTS Inter-RAT – CSFB by Redirection

Recommend value Comments HoAlgoSwitch _MOD ENODEBALG OSWITCH UtranCsfbSwitch:Off UtranCsfbSwitch

:On Enable CSFB to UTRAN switch HoModeSwitch BlindHoSwitch:Off BlindHoSwitch:O

ff Enable blind HO switch to perform CSFB CsfbHoUtranB1ThdR scp _MOD CSFALLBACK HO -106 Range: -120~-25 Unit: dBm

-100 [dBm] RSCP threshold for event B1 that is used in CSFB to UTRAN CsfbHoUtranTimeToT rig 40 Range: 0ms~5120ms

40 [ms] Time-to-trigger for event B1 that is used in CSFB to UTRAN

LTE -> GSM Inter-RAT – CSFB by Redirection

value Comments HoAlgoSwitch _MOD ENODEBALGO SWITCH GeranCsfbSwitch: Off GeranCsfbSwit

ch:On Enable CSFB to Geran switch HoModeSwitch BlindHoSwitch:Off BlindHoSwitch:

Off Enable blind HO switch to perform CSFB to Geran CsfbHoGeranB1Thd MOD CSFALLBACKH O -95 Range: -110~-48 Unit: dBm

-95 [dBm] RSSI threshold for event B1 that is used in CSFB to Geran

CsfbHoGeranTimeTo Trig

320

Range: 320 [ms] Time-to-trigger for event B1 that is used in CSFB to Geran (Higher than Utran to do CSFB to Utran first)

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UMTS/GSM to LTE Fast Return



Huawei Fast Return from UMTS/GSM to LTE feature enables a UE that moves from an LTE cell to a

UMTS cell through CSFB to quickly return to the LTE network after the CS service ended, by eNodeB

sending target LTE frequency from UMTS/GSM when UE release the CS call, in the RRC

release/Channel release message, not waiting for PS service disconnected.



This feature will help user to return to LTE in time, to utilize LTE network for PS services.



Recommended implementation to UMTS/GSM cells with co-located LTE cells or within fully continuous

LTE coverage area, to avoid UE fail to go back to LTE in areas that LTE coverage is not enough for UE

to register then cause UE lost service before UE reselect back to UMTS.



Since now Telkomsel LTE network is just started, LTE cannot provide fully continuous coverage, so

fast return

is only enabled in co-located 3G/2G cells.



Thus in case if UE make CSFB call to 3G/2G, but UE move to another neighboring cell without co-located LTE

site, then Fast Return wouldn’t trigger, thus UE have to wait all background PS service release (if any),

especially for smartphone user with many background PS connections. Thus user might experience relatively

“slow” back to LTE (typically 1~2 minutes if user is not intended to access internet).

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UMTS -> LTE Fast Return

UMTS Parameter MML Command Default value Recommend value Comments

FastReturnToL

TESwitch

MOD

UCELLHOCO

MM

(all carriers of the UMTS cell which co-site with LTE) HO_UMTS_TO_LTE _FAST_RETURN_S WITCH=0 HO_UMTS_TO_LTE_F AST_RETURN_SWITC H=1

Enable UMTS to LTE Fast Return

FastReturnToL

TESwitch

PERFENH_PS_FAS T_RETURN_LTE_S WITCH=0 PERFENH_PS_FAST_ RETURN_LTE_SWITC H=1

Enable UMTS to LTE Fast Return

GSM ->LTE Fast Return

GSM Parameter MML Command Default value Recommend value Comments