Huawei eRAN3.0 CSFB Feature Introduction

Apr. 2006

Node B Products of Huawei

Huawei eRAN3.0CSFB Feature Introduction

HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

eRAN2.2 eRAN3.0eRAN2.1

CSFB to UTRAN• PS HO• PS redirection

CSFB to GERAN• PS HO• PS redirection• CCO

CSFB to CDMA2000 1xRTT

Flash CSFB to UTRAN

Flash CSFB to GERAN

CSFB to GERAN• CCO with NACC

Next Evolutions

Adaptive blind CSFB

CSFB Steering

CSFB with eMPS

CSFB to UTRAN with LAI

CSFB to GERAN with LAI

Released

Planning

Planned

Huawei CSFB Feature Roadmap


Chapter One ： Feature Introduction

Architecture and functionalities Mobile Originating call Mobile Terminating call SMS Emergency call

Page 3

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 4

CSFB: brief introductionCSFB: brief introduction

Circuit Switched Fallback (CSFB, 3GPP TS23.272)The CS fallback in EPS enables the provisioning of voice and other CS-domain services (e.g. SMS/ LCS) by reuse of CS infrastructure when the UE is served by E‑UTRAN.

Circuit Switched Fallback (CSFB, 3GPP TS23.272)The CS fallback in EPS enables the provisioning of voice and other CS-domain services (e.g. SMS/ LCS) by reuse of CS infrastructure when the UE is served by E‑UTRAN.

This function is only available in case E‑UTRAN coverage is overlapped by either GERAN coverage or UTRAN coverage.

This function is only available in case E‑UTRAN coverage is overlapped by either GERAN coverage or UTRAN coverage.


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CSFB: Architecture and functionalitiesCSFB: Architecture and functionalities

S1-MME

S1-U

S11

E-UTRAN

MME

S-GW

S5

SGSN

HSS/HLR

S6a

S4

S3

S12

Iu-ps

Gb

PDN-GW

SGi

S7

MSC/VLR

A

Iu-cs

Gr

SGs

G/U/L handset

•Multi-mode G/U/L•CSFB capable•Support of procedures: Combined EPS/IMSI Attach, Update, Detach.

•Deriving a VLR number and LAI from the TAI of the current cell, or using a default VLR number and LAI.•Maintaining SGs association with MSC/VLR for EPS/IMSI Attached UE•Triggering paging to eNodeB (when MSC-S pages the UE)•Initiating IMSI Detach at EPS Detach

GERAN

UTRAN

•Need to be R8 ready•Maintaining SGs association with MME

•Forwarding paging request for CS domain to the UE.•Directing the UE to the target CS capable cell. (PS HO/redirection with or without SIBs).

C/D

PCRF

Rx

Internet / intranet / Operators & 3rd

Party Applications

Gs

for the mobility management and paging procedures between EPS and CS domain.



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CSFB: Mobile Originating call CSFB: Mobile Originating call

RAT change (and selection) is under full network control (eNodeB triggers the RAT change towards to 2G/3G based on the UE’s capability\measurement\SPID indication from MME.)

NodeB RNC

eNodeB SAE-GW

3G

LTE

MSC-VLR

SGs

HSS/HLR

Inte

r-sy

stem

ch

ang

e

6.Initiate voice call

MME

7.IAM

1. Ext Service RQ (CSFB indicator)

SGSN

4. PS HO or PS redirection

5. eNB direct the UE to G/U

2. S1 AP Message (CSFB indicator)

3.optional measurement



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CSFB: Mobile Terminating call CSFB: Mobile Terminating call

NodeB RNC

eNodeB SAE-GW

3G

LTE

MSC-VLR

SGs

2. Paging RQ (Domain indicator: CS)

8.P

agin

g R

espo

nse

HSS/HLR

Inte

r-sy

stem

ch

ang

e

9.Voice call establishment

MME

1.IAM

SGSN

7. eNB direct the UE to G/U

5.measurement 4. S1 AP Message (C

SFB indicator)

6. PS HO or PS redirection

3. Ext Service RQ (CSFB indicator)



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MMERNCeNodeBUE MSC SGSN

Handover Command

1. Extended Service Request (containing a CS Fallback Indicator)

Handover Command

S1-AP Response Message

3. Optional measurement report

4. PS handover preparation phase

5.CS call establishment procedure with LAU or combined RAU/LAU

6.PS handover execution phase

2. S1-AP Message (containing a CS Fallback Indicator)


3. S1-AP message with CS Fallback indicator

2.Extended Service Request (containing a CS Fallback Indicator)

Service Request

S-GWP-GW

Paging

1.Paging Request

4. Subsequent procedure similar to that in a mobile-originated case, with the CS call establishment procedure replaced with a Paging Response message

CSFB to UMTS (PS HO) CSFB to UMTS (PS HO)

MO call MT call



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CSFB to UMTS (PS RRC Redirection w/o RIM) CSFB to UMTS (PS RRC Redirection w/o RIM)

MO call (R8: without RIM)


2.S1-AP Message with 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


2.S1-AP Message with CS Fallback Indicator




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



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

MO call (R9: with RIM)

*MT call’s procedure is same.

PS Suspend PS Suspend



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CSFB to GERAN (PS HO) CSFB to GERAN (PS HO)

MO call MT callMMEBSCeNodeBUE MSC SGSN

Handover Command

1. Extended Service Request (containing a CS Fallback Indicator)

Handover Command


3. Optional measurement report

4a. PS handover preparation phase

4b.Suspend

5.CS call establishment procedure with LAU or combined RAU/LAU

6.PS handover execution phase

S-GWP-GW

Update Bearers

2. S1-AP Message (containing a CS Fallback Indicator)


3. S1-AP message with CS Fallback indicator


Service Request

S-GWP-GW

Paging

1.Paging Request

4. Subsequent procedure similar to that in a mobile-originated case, with the CS call establishment procedure replaced with a Paging Response message

BSC

In case GERAN or UE can’t support DTM (Dual transfer Mode) the PS service will be suspended



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CSFB to GERAN (PS RRC Redirection w/o RIM) CSFB to GERAN (PS RRC Redirection w/o RIM)

MMEBSCeNodeBUE MSC SGSN

2.S1-AP Message (containing a CS Fallback

Indicator)




6.Suspend

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



4. RRC Connection Release with GERAN frequency group


2.S1-AP Message (containing a CS Fallback Indicator)




6.Suspend




4. RRC Connection Release with GERAN frequency group\Cell id\Cell system information

MO call (R8: without RIM)MO call (R9: with RIM)



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CSFB to GERAN (CCO w/o RIM) CSFB to GERAN (CCO w/o RIM)

MO call (w/o RIM)


4. MobilityFromEUTRACommand (CCO optionally with NACC)

2.S1-AP Message (containing a CS Fallback Indicator)




7.Suspend



5. S1 UE context release

In case GERAN or UE can’t support DTM (Dual transfer Mode) the PS service will be suspended



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CSFB to UTRAN: Three mechanismsCSFB to UTRAN: Three mechanisms

R8 PS Handover: base on the inter-RAT PS handover procedures

R8 PS redirection: RRC release with“redirectedCarrierInfo”IE to UE

R9 PS redirection: RRC release with a carrier frequency and UTRAN cell’s SIBs acquired by RIM procedures before CSFB.



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CSFB to GERAN: Four mechanismsCSFB to GERAN: Four mechanisms

R8 PS Handover: base on the inter-RAT PS handover procedures

R8 PS redirection: RRC release with“redirectedCarrierInfo”IE to UE

R9 PS redirection: RRC release with a carrier frequency list and cell’s SIBs acquired by RIM procedures before CSFB.

R8 CCO with NACC: HandoverCommandWith target cell and SI



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CSFB: SMSCSFB: SMS

UE is EPS/IMSI attached and the CS access domain is chosen by the UE and/or the home PLMN for delivering short messages.

SMS support is based on the connectionless SGs reference point between the MME and the MSC Server and use of NAS signalling between the UE and the MME.

The MO SMS and MT SMS are signalled over SGs and do not cause any CS Fallback to GERAN/UTRAN RATs, and consequently does not require any overlapped GERAN/UTRAN coverage.

UE MME MSC HLR SMSC

1.EPS/IMSI attach

2.UE triggered Service Request

3. Uplink NAS Transport

4.Uplink Unitdata

5.Forward Short Message

4a.Downlink Unitdata

4a.Downlink NAS Transport

6.Delivery report

No CS Fallback is performed for SMS



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CSFB: Emergency callCSFB: Emergency call

E-UTRAN may use the emergency indication for selecting a particular radio access network (2G or 3G) for CS emergency handling.

If PS handover is initiated, E-UTRAN may indicate priority level of the CSFB to the target RAT, in order to prepare radio resource at target RAT in appropriate way, e.g. priority allocation of the RAB resource.

UE MME MSC RNC

Extended Service Request with Emergency Call Indication

S1-AP message with Emergency Call

Indication

eNB indicates in the Source RNC to Target RNC Transparent container that PS handover was

triggered due to CSFB and emergency purpose

eNB


Chapter Two: CSFB Algorithm at eNB

是

否

CSFB触发：是否盲切换

收到CS Fallback Indicator

开始

CSFB测量

CSFB决策

CSFB执行

结束

测量超时或异常

Triggering phase

The eNodeB receives a CS Fallback Indicator from the

MME. If the eNodeB supports blind handovers to an

inter-RAT system, it performs a blind handover without

delivering the measurement configuration to the UE.

Otherwise, the eNodeB delivers the measurement

configuration to the UE. Compared with measurement-

based handovers, blind handovers can reduce the

access delay. Therefore, blind handovers take

precedence over measurement-based handovers.

Blind handovers, however, have an impact on the

handover success rate.


The eNodeB delivers

the inter-RAT

measurement

configuration, and the

UE performs inter-RAT

measurements

accordingly.

In abnormal cases, eNB

performs blind

procedure.

The eNodeB executes

CSFB to enable the UE

to initiate the voice call

in the target cell.

The ongoin2g PS

services of the UE might

be handed over to the

target cell or suspended

in the source cell.

MeasurementPhase

DecisionPhase

ExecutionHandover

The eNodeB checks

the measurement

results and

generates a list of

candidate cells.


R8 CSFBR8 CSFB

eRAN2.0/2.1

Blind Scenario ： A list of candidate cells is generated on the basis of the blind handover priorities, which are determined by

both the RAT-specific priorities and the cell-specific priorities. The RAT-specific priorities used in blind handovers for CSFB are defined through the InterRatHighestPri,

InterRatSecondPri, and InterRatLowestPri parameters.

Measure Scenario ： eNB sends the UE the measurement configuration, according to which the UE performs measurements on the

specified system. The measurement configuration sent to the UE contains the configuration information for only the RATs and frequencies that are supported by the UE.

eNB selects the best cell from UE’s measurement report.

Mn is the measurement result of the neighboring cell. Ofn is the frequency-specific offset for the frequency of the neighboring cell. Hys is the hysteresis for event B1. Thresh is the threshold for event B1. The values of Thresh are set on the basis of the measurement quantities of each RAT.The Received Signal Code Power (RSCP) threshold for CSFB to UTRAN, Ec/No threshold for CSFB to UTRAN, threshold for CSFB to GERAN, and threshold for CSFB to CDMA2000 1xRTT are specified through the CsfbHoUtranB1ThdRSCP, CsfbHoUtranB1ThdECN0, CsfbHoGeranB1Thd, and CsfbHoCDMAB1ThdPS parameters respectively.

ThreshHysOfnMn B1 entering condition:


Flash CSFB ( R9 redirection with SIBs ） Flash CSFB ( R9 redirection with SIBs ）

2G/3G Access

LTE Access

RIM :RAN information exchanging

SGSN

GSM/UMTS GSM/UMTS CoreCore

MME

LTE CoreLTE Core

Flash CSFB:

• Saving 1s for UMTS compare with R8 CSFB

• Saving 2s for GSM compare with R8 CSFB

Frequency and target cell system information

Frequency and target cell system information

Key Point:1. eNB request system information from BSC/RNC

when establish Inter-RAT neighbor relation;

2. BSC/RNC reply system information. If system

information update ， BSS/RNC notify eNodeB and

send the latest information;

3. Core Network doesn’t handle the message, only

forward;

4. eNB doesn’t translate message from

BSC/RNC ， send to UE directly;

5. eNB fill out the target frequency and related neighbor

cell information in RRC_Release message.

BSC/RNC

RA

N

information

RA

N in

form

atio

n

req

ue

st

eRAN2.2


CSFB to UTRAN/GERAN with LAICSFB to UTRAN/GERAN with LAI

LAI Based CSFB:

1. Priority to select target GU cells with same

LAC as UE registered in GU NW during

CSFB to avoid LAU (0.5s~3s).

2. Support National Roaming Ue to select

suitable fallback RAT/Cell bases on LAI

Indicator among multi-PLMNs.

TA3/LA1

TAI/LAI

MME

LTE LTE CoreCore

GUL

GUL

GUL

TA1/LA1

TA2/LA2

Select same LA to CSFB

CSFB to LA1

eRAN3.0

Step1: eNB receives “Registered LAI” from MMEMME sends “Registered LAI” to eNB via “Initial Context Setup Request” or “UE Context Modification Request” message.

Step2: eNB selects target network with LAI consideration1> Blind case: following the priority below. 1>Neighboring cell with the same LAI with “Registered LAI”; 2>Neighboring cell with the same PLMN with “registered LAI”; 3>Neighboring cell with the same PLMN with the UE current serving PLMN.2>Measurement case: 1>if any of the neighboring frequency’s cell PLMN is the same with “Registered LAI”, or if any of the neighboring frequency’s cell PLMN is the same with the UE current serving PLMN, and the UE supports the RAT and the frequency, eNB will send these frequency to UE for measuring. 2>eNB will choose the same LAI from the measurement reports.


CSFB key parameters

MO Parameter ID DescriptionCSFallBackBlindHoCfg InterRatHighestPri Indicates the high-priority system to be considered in blind handovers for CS

fallback. It is UTRAN by default.CSFallBackBlindHoCfg InterRatSecondPri Indicates the medium-priority system to be considered in blind handovers for CS

fallback. It is GERAN by default. If this parameter is set to null, the system with the medium blind handover priority is not specified. In this case, only the blind handovers to the high-priority system are applicable.

CSFallBackBlindHoCfg InterRatLowestPri Indicates the low-priority system to be considered in blind handovers for CS fallback. It is CDMA2000 by default. If this parameter is set to null, the system with the low blind handover priority is not specified. In this case, only the blind handovers to the high- and medium-priority systems are applicable.

CSFallBackBlindHoCfg UtranLcsCap Indicates the Location Services (LCS) capability of the UTRAN.

CSFallBackBlindHoCfg GeranLcsCap Indicates the Location Services (LCS) capability of the GERAN.

CSFallBackBlindHoCfg CdmaLcsCap Indicates the Location Services (LCS) capability of the CDMA2000.

CSFallBackHo CsfbHoUtranTimeToTrig Indicates the time-to-trigger for event B1 that is used in CS fallback to UTRAN/GERAN/CDMA2000. When CS fallback to UTRAN/GERAN/CDMA2000 is applicable, this parameter is set for UEs and used in the evaluation of whether to trigger event B1. When detecting that the signal quality in at least one UTRAN/GERAN/CDMA2000 cell meets the entering condition, the UE does not send a measurement report to the eNodeB immediately. Instead, the UE sends a report only when the signal quality continuously meets the entering condition during the time-to-trigger. This parameter helps decrease the number of occasionally triggered event reports, the average number of handovers, and the number of wrong handovers, and thus helps prevent unnecessary handovers. For details, see 3GPP TS 36.331.

CSFallBackHo CsfbHoGeranTimeToTrig

CSFallBackHo CsfbHoCDMATimeToTrig


MO Parameter ID DescriptionCSFallBackHo CsfbHoUtranB1ThdRSCP Indicates the RSCP threshold for event B1, which is used in CS fallback to UTRAN.

When CS fallback to UTRAN is applicable, this parameter is set for UEs and used in the evaluation about whether to trigger event B1. This parameter indicates the RSCP requirement for the UTRAN cells to be included in the measurement report. A UE sends a measurement report related to event B1 to the eNodeB when the RSCP in at least one UTRAN cell exceeds this threshold and other triggering conditions are met. For details, see 3GPP TS 36.331.

CSFallBackHo CsfbHoUtranB1ThdECN0 Indicates the Ec/No threshold for event B1, which is used in CS fallback to UTRAN. When CS fallback to UTRAN is applicable, this parameter is set for UEs and used in the evaluation about whether to trigger event B1. This parameter indicates the Ec/No requirement for the UTRAN cells to be included in the measurement report. A UE sends a measurement report related to event B1 to the eNodeB when the Ec/No in at least one UTRAN cell exceeds this threshold and other triggering conditions are met. For a cell with large signal fading variance, set this parameter to a large value to prevent unnecessary handovers. For a cell with small signal fading variance, set this parameter to a small value to ensure that the handover is performed in time. For details, see 3GPP TS 36.331.

CSFallBackHo CsfbHoGeranB1Thd Indicates the RSSI threshold for event B1 that is used in CS fallback to GERAN. A UE sends a measurement report related to event B1 to the eNodeB when the RSSI in at least one GERAN cell exceeds this threshold and other triggering conditions are met. For details, see 3GPP TS 36.331.

CSFallBackHo CsfbHoCDMAB1ThdPS Indicates the pilot strength threshold related to event B1, which is used in CS fallback to CDMA2000. A UE sends a measurement report related to event B1 to the eNodeB when the pilot strength in at least one CDMA2000 cell exceeds this threshold and other triggering conditions are met. For details, see 3GPP TS 36.331.


MO Parameter ID Default Value Actual Unit MML CommandCSFallBackBlindHoCfg

InterRatHighestPri UTRAN UTRAN, GERAN, CDMA2000

UTRAN, GERAN, CDMA2000

None MOD CSFALLBACKBLINDHOCFGLST CSFALLBACKBLINDHOCFG

CSFallBackBlindHoCfg

InterRatSecondPri GERAN UTRAN, GERAN, CDMA2000, NULL

UTRAN, GERAN, CDMA2000, NULL



InterRatLowestPri CDMA2000 UTRAN, GERAN, CDMA2000, NULL

UTRAN, GERAN, CDMA2000, NULL



UtranLcsCap OFF(Off) OFF(Off), ON(On) OFF, ON None MOD CSFALLBACKBLINDHOCFGLST CSFALLBACKBLINDHOCFG


GeranLcsCap OFF(Off) OFF(Off), ON(On) OFF, ON None MOD CSFALLBACKBLINDHOCFGLST CSFALLBACKBLINDHOCFG


CdmaLcsCap OFF(Off) OFF(Off), ON(On) OFF, ON None MOD CSFALLBACKBLINDHOCFGLST CSFALLBACKBLINDHOCFG


MO Parameter ID Default Value Actual Unit MML Command

CSFallBackHo CsfbHoUtranTimeToTrig

40ms 0ms, 40ms, 64ms, 80ms, 100ms, 128ms, 160ms, 256ms, 320ms, 512ms, 480ms, 640ms, 1024ms, 1280ms, 2560ms, 5120ms

0ms, 40ms, 64ms, 80ms, 100ms, 128ms, 160ms, 256ms, 320ms, 512ms, 480ms, 640ms, 1024ms, 1280ms, 2560ms, 5120ms

ms MOD CSFALLBACKHOLST CSFALLBACKHO

CSFallBackHo CsfbHoGeranTimeToTrig

40ms ms MOD CSFALLBACKHOLST CSFALLBACKHO

CSFallBackHo CsfbHoCDMATimeToTrig

40ms ms MOD CSFALLBACKHOLST CSFALLBACKHO

CSFallBackHo CsfbHoUtranB1ThdRSCP

-106 -120~-25 -120~-25 dBm MOD CSFALLBACKHOLST CSFALLBACKHO

CSFallBackHo CsfbHoUtranB1ThdECN0

-13 -48~0 -24~0 0.5dB MOD CSFALLBACKHOLST CSFALLBACKHO

CSFallBackHo CsfbHoGeranB1Thd

-103 -110~-48 -110~-48 dBm MOD CSFALLBACKHOLST CSFALLBACKHO

CSFallBackHo CsfbHoCDMAB1ThdPS

-34 -63~0 -31.5~0 0.5dB MOD CSFALLBACKHOLST CSFALLBACKHO

Switches are not shown here. Please refer to CSFB FPD.

HUAWEI TECHNOLOGIES Co., Ltd. HUAWEI Confidential Page 26

Chapter Three: Algorithm Relationship

LOFD-001033 CS Fallback to UTRAN depends on LOFD-001019 PS Inter-RAT Mobility

between E-UTRAN and UTRAN.

LOFD-001034 CS Fallback to GERAN depends on LOFD-001020 PS Inter-RAT Mobility

between E-UTRAN and GERAN.

LOFD-001035 CS Fallback to CDMA2000 1xRTT depends on LOFD-001021 PS Inter-RAT

Mobility between E-UTRAN and CDMA2000.

LOFD-001052 Flash CS Fallback to UTRAN depends on LOFD-001033 CS Fallback to UTRAN.

LOFD-001053 Flash CS Fallback to GERAN depends on LOFD-001034 CS Fallback to GERAN.

LOFD-001068 CS Fallback with LAI to UTRAN depends on LOFD-001033 CS Fallback to

UTRAN.

LOFD-001069 CS Fallback with LAI to GERAN depends on LOFD-001034 CS Fallback to

GERAN.

Page 26


Chapter Four: Use Case

G/U G/U coveragecoverage

LTELTEcoveragecoverageUL dual

mode UE

Camping (LTE) Voice (G/U) Back to LTE

PLMN selection indicator in SIM card

Frequency priority in network system information broadcast

CSFB to G/U to make the CS call

Idle UE:Frequency priority in G/U

system information broadcast Active UE:PS redirectionPS HO based on service

Deployment Scenario No IMS support in LTE/SAE or roaming. E‑UTRAN coverage is overlapped by either GERAN coverage or UTRAN coverage.


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Huawei eRAN3.0 CSFB Feature Introduction