LTE Features-II
LTE CS Fallback (CSFB)
LTE→ UMTS
LTE→ GSM
Introduction
This report aim to explain all about CSFB feature trial that has been tested on one site
in Lattakia “American Road-LTK014”.
Why We Need CSFB? CSFB to GSM
– CSFB to GSM Implementation
– Enhancement Feature
– CSFB to GSM Signaling-MTC
– CSFB to GSM Signaling-MOC
CSFB Procedure
CSFB KPIs
CSFB to UMTS
– CSFB to UMTS Implementation
– Enhancement Feature
– Enhancement Feature-Implementation
– CSFB to UMTS Signaling-MTC Important Notes
– CSFB to UMTS Signaling-MOC
?Why We Need CSFB
When LTE was introduced there was practically no option for voice
communication. To support voice and other CS services there is two options:
Voice Over LTE (VoLTE) CS Fallback (CSFB)
• VoLTE is the true solution for voice When a mobile phone starts a voice
communication over the all-IP LTE call the network move the UE to a
network. UMTS (3G) or GSM (2G) network.
• It uses the IMS (IP Multimedia The UE use the other network to
Subsystem) to initiate, connect and initiate the call and complete the call.
terminate voice communication. After the call is over UE again move
back to the LTE network.
• The service is heavily dependent on
many new core network elements.
CSFB Procedure
CSFB to UMTS Implementation
Prerequisite features: We need to define both way
Level Feature
CS Fallback to GERAN and UTRAN
FAJ CXC
LTE-UMTS Relations first.
LTE Site “CsfbToGeranUtran” FAJ 121 0856 CXC4010956
WCDMA Session Continuity, Feature for CS (Main in
LTE Site Coverage-Triggered FAJ 121 0493 CXC4010616
“WcdmaSessionContinuity“ CSFB)
SGSN-MME CS Fallback to GSM and WCDMA FAJ 121 0835 CXC4030106
“CsFallbackLte” Feature for PS (not related to
MSC-S LTE to CS Fallback FAJ 121 0793 -
CSFB but needed instead of
WCDMA RAN CS Voice Fallback from LTE FAJ 121 1610 -
HO for PS data)
MO (LTE Cell Level) Reason Parameter name Recommended Value
UtranFreqRelation Adjust CSFB parameters csFallbackPrio 3
UtranFreqRelation Adjust CSFB parameters mobilityActionCsfb 0 (RELEASE_WITH_REDIRECT) 2
3
GeranFreqGroupRelation Adjust CSFB parameters csFallbackPrio 2
GeranFreqGroupRelation Adjust CSFB parameters mobilityActionCsfb 0 (RELEASE_WITH_REDIRECT
Enhancement Feature
“RWR to LTE : Release With Redirect to LTE” feature is needed to redirect the user to LTE after CS call release.
Without this feature, the CSFB terminal will stay in 3G until going to idle mode before going back to LTE. And in case there is ongoing PS
session, this user needs to wait about 15 min of inactivity before going back to LTE (FACH to URA in 10s then URA to Idle in 15 min). The
RWR feature will accelerate the revert back to LTE in order to increase the time on LTE.
Upon implementing RWR to LTE, the LTE capable terminal will be moved back to LTE if there is LTE coverage in other states than idle.
The states when the redirect order is sent to the device, are configurable by the operator.
There are six triggering points that can be activated. These are:
normalRelease - RWR to LTE at normal release
fastDormancy - at fast dormancy
dchToFach - at channel switch from DCH to FACH
fachToUra - at channel switch from FACH to URA
csFallbackCsRelease - after CS fallback at CS release
csFallbackDchToFach - after CS fallback at channel switch from DCH to FACH
No triggering will take place while CS speech is ongoing.
Enhancement Feature-Implementation
We will enable the redirect trigger at CSFB CS call release.
In the case there is PS session, we will wait until DCH to FACH channel switch or fast dormancy occurs to trigger the redirect to LTE.
Action Level Reason Feature name Recommended Value
RNC Side Activate RWR to LTE Feature ReleaseRedirectLte 1
Not Important for the Iur Level
MO (UMTS Side) Reason Parameter name Recommended Value
IurLink Adjust RWR parameters releaseRedirect 1
IurLink Adjust RWR parameters releaseRedirectEutraTriggers.csFallbackCsRelease 1
IurLink Adjust RWR parameters releaseRedirectEutraTriggers.fastDormancy 1
IurLink Adjust RWR parameters releaseRedirectEutraTriggers.csFallbackDchToFach 0
IurLink Adjust RWR parameters releaseRedirectEutraTriggers.normalRelease 0
IurLink Adjust RWR parameters releaseRedirectEutraTriggers.fachToUra 0
IurLink Adjust RWR parameters releaseRedirectEutraTriggers.dchToFach 1
Enhancement Feature-Implementation
Date CR Code CR Responsible RNC Site Cell MO Parameter Current Value Recommended Value Reason
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UA releaseRedirect 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UB releaseRedirect 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UC releaseRedirect 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UX releaseRedirect 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UY releaseRedirect 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UZ releaseRedirect 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UA,EutranFreqRelation=1650 redirectionOrder 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UB,EutranFreqRelation=1650 redirectionOrder 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UC,EutranFreqRelation=1650 redirectionOrder 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UX,EutranFreqRelation=1650 redirectionOrder 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UY,EutranFreqRelation=1650 redirectionOrder 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046UZ,EutranFreqRelation=1650 redirectionOrder 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046U.* releaseRedirectEutraTriggers.csFallbackCsRelease 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046U.* releaseRedirectEutraTriggers.dchToFach 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046U.* releaseRedirectEutraTriggers.fastDormancy 1 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046U.* releaseRedirectEutraTriggers.csFallbackDchToFach 0 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046U.* releaseRedirectEutraTriggers.normalRelease 0 Adjust RWR parameters
8-Nov-17 12022018-1 Rachad AL_RNC_02 UtranCell=ALP046U.* releaseRedirectEutraTriggers.fachToUra 0 Adjust RWR parameters
Cell Level Parameter from EutranFreqRelation MO
Cell Level Parameter from UtranCell MO (Not exist (exist in Dumb file )
in Dumb file, only by command )
Iur not important
CSFB to UMTS Signaling-MTC
CSFB to UMTS Signaling-MOC
CSFB to GSM Implementation
Required MOs:
– GeraNetwork=1, We need to define both
– GeranFreqGroup=1,
– GeranFrequency=1, //arfcnValueGeranDl way LTE-GSM Relations.
– GeranFreqGroupRelation=1,
Required features:
Level Feature FAJ CXC
GSM Side Activate GSM-LTE Cell Reselection - -
LTE Side Activate GERAN Session Continuity Coverage-Triggered FAJ 121 0495 CXC4010618
MO (LTE Cell Level) Reason Parameter name Recommended Value
UtranFreqRelation Adjust CSFB parameters csFallbackPrio 3
3
UtranFreqRelation Adjust CSFB parameters mobilityActionCsfb 0 (RELEASE_WITH_REDIRECT) 4
GeranFreqGroupRelation Adjust CSFB parameters csFallbackPrio 4
GeranFreqGroupRelation Adjust CSFB parameters mobilityActionCsfb 0 (RELEASE_WITH_REDIRECT
Enhancement Feature
GSM-LTE Cell Reselection (FAJ 123 155):With this feature a GSM/LTE capable terminal
in GSM is able to perform cell reselection to LTE in both idle and packet transfer mode
LTE as soon as coverage from LTE is available and the call on GSM is finished.
Below 2G parameters can be tuned to enable GSM-LTE Cell Reselection after activating
the license of this feature:
Parameter LTE 1800 Freq. Relation Comment
EARFCN 1625 (or 1650) LTE Frequency
PRIOCR ON Enable priority based Cell Reselection
QRXLEVMINE 10 qRxLevMin for LTE (-120)
RATPRIO 7 LTE Cell Reselection priority
CSFB to GSM Signaling-MTC
CSFB to GSM Signaling-MOC
CSFB KPIs
CSFBtoWCDMARatio=[pmUeCtxtRelCsfbWcdma]/([pmUeCtxtRelMme]+[pmUeCtxtRelAbnormalEnb]+[pmUeCtxtRelNormalEnb])*100
Meaning: The ration of UE Release messages due to CSFB to UMTS network.
CSFBtoGSMRatio=[pmUeCtxtRelCsfbGsm]/([pmUeCtxtRelMme]+[pmUeCtxtRelNormalEnb]+[pmUeCtxtRelAbnormalEnb])*100
Meaning: The ration of UE Release messages due to CSFB to GSM network.
The appeared
values are just
an example for
the results of
the KPIs
during the
tests.
The two mentioned KPIs are included in the report named “LTE” at BO inside “Rasha” folder
Important Notes
The Following parameters do not have any
must To be able to perform License for relation with CSFB. They only defined the
The network CSFB, the SIM should
The
Cell
the SGs “GSM-LTE preferred system in idle and connected
support have CS profile feature” mode for LTE users, hence, the highest
the
interface between activation by Core.
Reselection
r the priority (7) should be on LTE:
MSC and the MM
E to
To see the caller number, were requested fo
, We
support CS Fallbac
k. CLIP service should be trial sites only
r the
activated on the SIM need to order it fo connectedModeMobilityPrio
profile as well. rest. MO: EUTRANFreqRelation=7
MO: UTRANFreqRelation=3
MO: GERANFreqGroupRelation=2
the cellReselectionPriority
UMTS has
MO: EUTRANFreqRelation=7
priority over
G SM a packet
ing If there is during correct TAC/LAC MO: UTRANFreqRelation=6/5 (C1/C2)
perf o rm
when transfer or mapping is essent
ial for MO: GERANFreqGroupRelation=2
ill go
CSFB→ We w terminating it w ill successful CS pa ging
enario call, Core
with the 1 sc originating (The Table was se
nt to
st mobilityAction
then plemented
S) paused Team an d im MO: EUTRANFreqRelation=1 (HO)
(CSFB to UMT be
er the call successfully)
proceed aft MO: UTRANFreqRelation=2 (HO)
MO: GERANFreqGroupRelation=0 (RWR)
ends.
Summary
Tests were done successfully for both UMTS and GSM.
The return features were tested successfully.
The Trial is done successfully in Lattakia, and we will wait the security
approval to officially activate this service on our network.
After the approval, we will implement the CSFB to all sites with priority to
UMTS network over GSM.
