294233574-LTE-Call-Flow-PS-Redirection-to-UTRAN-V2015-0105-V1-0.pdf

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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