LTE Call Flow: PS Redirection to UTRAN Contact:
[email protected] Created: 2014_1225 Date and Version
Author
Change Note
2015_0105 v1.0
Justin MA
First version
RRC connection release with redirect •
Main Menu
Redirection to UTRAN UE
eNB
NB & RNC
ECM CONNECTED
MME
SAE GW
MSC / MSC Server
SGSN
LTE related part of the redirection procedure
A2 event criteria met
A2 event measurement report
RRC Connection Release (including selection of redirection target)
UE Context Release
Target RAT related part of the redirection procedure
Target RAT Initial Access -> RRC Connection Setup
Routing Area Update with EPC interaction (including Authentication & Ciphering & Security Mode setup; EPS Bearers to PDP Contexts mapping)
PS session establishment (paging for DL transfer; service request, PDP Contexts activation including RAB setup)
Data transfer
Ref: NSN
LTE EMM and ECM States
Ref: NETMANIAS
Glossary • EPS: Evolved Packet System • ECM: EPS Connection Management • ESM: EPS Session Management • EMM: EPS Mobility Management
Figure: EPS with interface name
Ref: http://awanetwork.blogspot.tw/
RRC connection release with redirect •
Main Menu
Redirection to UTRAN
• Having received RRC: Measurement Report triggered by dedicated Event A2, eNB selects target layer – blind selection based on parameters setting and UE capabilities • Having determined target layer, eNB initiates RRC connection release with redirection by sending RRC: RRC CONNECTION RELEASE message – ReleaseCause is set to “other” – redirectedCarrierInfo IE provides the UE with information on target layer • UE switches to RRC-IDLE mode and searches for suitable cell within indicated layer • If no suitable redirection target is found, redirection procedure is abandoned – RRC Connection and UE Context are not released at this point of time
Ref: NSN
RRC connection release with redirect •
Table of Contents
Main Menu
Redirection to UTRAN
• Having released RRC connection, eNB initiates UE context release by sending S1AP: UE CONTEXT RELEASE REQUEST message to the MME – cause: Radio Network Layer cause: E-UTRAN Generated Reason if redirection towards LTE layer – cause: Radio Network Layer cause: Inter-RAT Redirection if redirection towards other RAT, – these cause values indicate to the MME that the PS service suspension is not required in the EPC • MME orders eNB to release UE dedicated resources and remove UE contexts • MME changes the UE state from ECM-CONNECTED to ECM-IDLE
Ref: NSN
LTE Measurement Event – A2
Ref:
Real L3 Call Flow – Message View Start Time:
2014-11-14 08:00
Timestamp 0 0.003 0.004 0.021 0.023 0.05 0.057 0.058 0.079 0.086 0.087 0.099 0.123 0.146 3.266 3.266 3.267 3.288 3.289
Cell ID 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730
Message RRC_RRC_CONNECTION_REQUEST INTERNAL_PER_RADIO_UE_MEASUREMENT_TA RRC_RRC_CONNECTION_SETUP RRC_RRC_CONNECTION_SETUP_COMPLETE S1_INITIAL_UE_MESSAGE S1_INITIAL_CONTEXT_SETUP_REQUEST RRC_SECURITY_MODE_COMMAND RRC_RRC_CONNECTION_RECONFIGURATION RRC_SECURITY_MODE_COMPLETE RRC_RRC_CONNECTION_RECONFIGURATION_COMPLETE S1_INITIAL_CONTEXT_SETUP_RESPONSE RRC_MEASUREMENT_REPORT RRC_RRC_CONNECTION_RECONFIGURATION RRC_RRC_CONNECTION_RECONFIGURATION_COMPLETE RRC_MEASUREMENT_REPORT RRC_RRC_CONNECTION_RELEASE S1_UE_CONTEXT_RELEASE_REQUEST S1_UE_CONTEXT_RELEASE_COMMAND S1_UE_CONTEXT_RELEASE_COMPLETE
ECM Connected
RRC_RRC_CONNECTION_RECONFIGURATION } measIdToAddModList[0] { measId = 1 measObjectId = 1 reportConfigId = 1 } measIdToAddModList[1] { measId = 2 measObjectId = 1 reportConfigId = 2 } measIdToAddModList[2] { measId = 4 measObjectId = 1 reportConfigId = 4 } measIdToAddModList[3] { measId = 9 measObjectId = 1 reportConfigId = 3 }
measId and reportConfigId
RRC_RRC_CONNECTION_RECONFIGURATION } reportConfigToAddModList[2] { reportConfigId = 3 reportConfig { reportConfigEUTRA { triggerType { periodical { purpose = reportStrongestCells } } triggerQuantity = rsrp reportQuantity = both
maxReportCells = 8 reportInterval = ms5120 reportAmount = r4 }
reportConfigId = 3
RRC_RRC_CONNECTION_RECONFIGURATION
Parameters in EA2
reportConfigToAddModList[3] { reportConfigId = 4 reportConfig { reportConfigEUTRA { triggerType { event { eventId { eventA2 { a2_Threshold { threshold_RSRP = 22 } } } hysteresis = 0 timeToTrigger = ms256 } } triggerQuantity = rsrp
-118 dBm
reportQuantity = sameAsTriggerQuantity maxReportCells = 8 reportInterval = min60 reportAmount = r1
}
Ref:
RRC_MEASUREMENT_REPORT TimeStamp: 0.098592 ID: 1545730 RRC_MEASUREMENT_REPORT UL - DCCH { message { c1 { measurementReport { criticalExtensions { c1 { measurementReport_r8 { measResults { measId = 9 measResultPCell { rsrpResult = 27 rsrqResult = 23 } measResultNeighCells { measResultListEUTRA[0] { physCellId = 295 measResult { rsrpResult = 19 rsrqResult = 13 } } measResultListEUTRA[1] { physCellId = 101 measResult { rsrpResult = 17 rsrqResult = 0 }
measId=9 reportStrongestCells -113 dBm
Above threshold_rsrp = -118dBm
-121 dBm
-123 dBm
RRC_MEASUREMENT_REPORT
measId=4 reportReconfig 4
TimeStamp: 3.26554 ID: 1545730 RRC_MEASUREMENT_REPORT
UL - DCCH { message { c1 {
Lower than threshold_rsrp = -118dBm
measurementReport {
criticalExtensions { c1 { measurementReport_r8 { measResults { measId = 4
measResultPCell { rsrpResult = 18
rsrqResult = 8 }
-122 dBm
Real L3 Call Flow – Message View Start Time:
2014-11-14 08:00
Timestamp 0 0.003 0.004 0.021 0.023 0.05 0.057 0.058 0.079 0.086 0.087 0.099 0.123 0.146 3.266 3.266 3.267 3.288 3.289
Cell ID 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730 1545730
Message RRC_RRC_CONNECTION_REQUEST INTERNAL_PER_RADIO_UE_MEASUREMENT_TA RRC_RRC_CONNECTION_SETUP RRC_RRC_CONNECTION_SETUP_COMPLETE S1_INITIAL_UE_MESSAGE S1_INITIAL_CONTEXT_SETUP_REQUEST RRC_SECURITY_MODE_COMMAND RRC_RRC_CONNECTION_RECONFIGURATION RRC_SECURITY_MODE_COMPLETE RRC_RRC_CONNECTION_RECONFIGURATION_COMPLETE S1_INITIAL_CONTEXT_SETUP_RESPONSE RRC_MEASUREMENT_REPORT RRC_RRC_CONNECTION_RECONFIGURATION RRC_RRC_CONNECTION_RECONFIGURATION_COMPLETE RRC_MEASUREMENT_REPORT RRC_RRC_CONNECTION_RELEASE S1_UE_CONTEXT_RELEASE_REQUEST S1_UE_CONTEXT_RELEASE_COMMAND S1_UE_CONTEXT_RELEASE_COMPLETE
ECM Connected
Current cell rsrp Lower than threshold_rsrp = -118dBm
RRC_CONNECTION_RELEASE TimeStamp: 3.26623
UE Redirection to U900
ID: 1545730
RRC_RRC_CONNECTION_RELEASE DL - DCCH { message { c1 { rrcConnectionRelease { rrc_TransactionIdentifier = 3
criticalExtensions { c1 { rrcConnectionRelease_r8 {
releaseCause = other redirectedCarrierInfo { utra_FDD = 3086 }
1. releaseCause is other 2. Blind Redirection to 3G, 3. UTRA, FDD = 3086 (U900)
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