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
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential
Chapter One : Feature Introduction
Architecture and functionalities Mobile Originating call Mobile Terminating call SMS Emergency call
Page 3
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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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Page 5
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)
MMERNCeNodeBUE MSC SGSN
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)
MMERNCeNodeBUE 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
MMERNCeNodeBUE 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)
*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
S1-AP Response Message
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)
MMERNCeNodeBUE MSC SGSN
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
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)
1.Extended Service Request (containing a CS Fallback Indicator)
S1-AP Reponse Message
3.Optional measurement report
6.Suspend
5.LAU, combined RAU/LAU, or RAU and LAU
7.CS call establishment procedure
S1 UE context release
4. RRC Connection Release with GERAN frequency group
MMEBSCeNodeBUE MSC SGSN
2.S1-AP Message (containing a CS Fallback Indicator)
1.Extended Service Request (containing a CS Fallback Indicator)
S1-AP Reponse Message
3.Optional measurement report
6.Suspend
5.LAU, combined RAU/LAU, or RAU and LAU
7.CS call establishment procedure
S1 UE context release
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)
MMEBSCeNodeBUE MSC SGSN
4. MobilityFromEUTRACommand (CCO optionally with NACC)
2.S1-AP Message (containing a CS Fallback Indicator)
1.Extended Service Request (containing a CS Fallback Indicator)
S1-AP Response Message
3.Optional measurement report
7.Suspend
6.LAU, combined RAU/LAU, or RAU and LAU
8.CS call establishment procedure
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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Page 15
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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Page 16
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
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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.
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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.
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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:
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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
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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.
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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
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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.
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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
None MOD CSFALLBACKBLINDHOCFGLST CSFALLBACKBLINDHOCFG
CSFallBackBlindHoCfg
InterRatLowestPri CDMA2000 UTRAN, GERAN, CDMA2000, NULL
UTRAN, GERAN, CDMA2000, NULL
None MOD CSFALLBACKBLINDHOCFGLST CSFALLBACKBLINDHOCFG
CSFallBackBlindHoCfg
UtranLcsCap OFF(Off) OFF(Off), ON(On) OFF, ON None MOD CSFALLBACKBLINDHOCFGLST CSFALLBACKBLINDHOCFG
CSFallBackBlindHoCfg
GeranLcsCap OFF(Off) OFF(Off), ON(On) OFF, ON None MOD CSFALLBACKBLINDHOCFGLST CSFALLBACKBLINDHOCFG
CSFallBackBlindHoCfg
CdmaLcsCap OFF(Off) OFF(Off), ON(On) OFF, ON None MOD CSFALLBACKBLINDHOCFGLST CSFALLBACKBLINDHOCFG
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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.
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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.
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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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