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

LTE Call Flow:PS Redirection to UTRAN

Contact: majachang@gmail.com

Created: 2014_1225

Date and Version Author Change Note

2015_0105 v1.0 Justin MA First version

Main MenuRRC connection release with redirect• Redirection to UTRAN

ECM CONNECTED

A2 event criteria met

RRC Connection Release(including selection of redirection target)

UE Context Release

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)

A2 event measurement report

Data transfer

UE MMEeNB NB & RNC SAE GWMSC /

MSC ServerSGSN

LTE related part of the redirection procedure

Target RAT related part of the redirection procedure

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

Ref: http://awanetwork.blogspot.tw/

Figure: EPS with interface name

Main MenuRRC connection release with redirect• 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, eNBinitiates 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

Main MenuRRC connection release with redirect• 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

Table of Contents

Ref: NSN

LTE Measurement Event – A2

Ref:

Real L3 Call Flow – Message View

Start Time: 2014-11-14 08:00

Timestamp Cell ID Message

0 1545730 RRC_RRC_CONNECTION_REQUEST

0.003 1545730 INTERNAL_PER_RADIO_UE_MEASUREMENT_TA

0.004 1545730 RRC_RRC_CONNECTION_SETUP

0.021 1545730 RRC_RRC_CONNECTION_SETUP_COMPLETE

0.023 1545730 S1_INITIAL_UE_MESSAGE

0.05 1545730 S1_INITIAL_CONTEXT_SETUP_REQUEST

0.057 1545730 RRC_SECURITY_MODE_COMMAND

0.058 1545730 RRC_RRC_CONNECTION_RECONFIGURATION

0.079 1545730 RRC_SECURITY_MODE_COMPLETE

0.086 1545730 RRC_RRC_CONNECTION_RECONFIGURATION_COMPLETE

0.087 1545730 S1_INITIAL_CONTEXT_SETUP_RESPONSE

0.099 1545730 RRC_MEASUREMENT_REPORT

0.123 1545730 RRC_RRC_CONNECTION_RECONFIGURATION

0.146 1545730 RRC_RRC_CONNECTION_RECONFIGURATION_COMPLETE

3.266 1545730 RRC_MEASUREMENT_REPORT

3.266 1545730 RRC_RRC_CONNECTION_RELEASE

3.267 1545730 S1_UE_CONTEXT_RELEASE_REQUEST

3.288 1545730 S1_UE_CONTEXT_RELEASE_COMMAND

3.289 1545730 S1_UE_CONTEXT_RELEASE_COMPLETE

ECM Connected

}

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 reportConfigIdRRC_RRC_CONNECTION_RECONFIGURATION

reportConfigId = 3}

reportConfigToAddModList[2] {

reportConfigId = 3

reportConfig {

reportConfigEUTRA {

triggerType {periodical {

purpose = reportStrongestCells

}}

triggerQuantity = rsrp

reportQuantity = both

maxReportCells = 8

reportInterval = ms5120

reportAmount = r4

}

RRC_RRC_CONNECTION_RECONFIGURATION

Parameters in EA2reportConfigToAddModList[3] {

reportConfigId = 4reportConfig {

reportConfigEUTRA {triggerType {

event {eventId {

eventA2 {a2_Threshold {

threshold_RSRP = 22}

}}hysteresis = 0timeToTrigger = ms256

}}

triggerQuantity = rsrp

reportQuantity = sameAsTriggerQuantity

maxReportCells = 8reportInterval = min60reportAmount = r1

}

RRC_RRC_CONNECTION_RECONFIGURATION

Ref:

-118 dBm

measId=9reportStrongestCells

TimeStamp: 0.098592ID: 1545730RRC_MEASUREMENT_REPORTUL - DCCH {

message {c1 {

measurementReport {criticalExtensions {

c1 {measurementReport_r8 {

measResults {measId = 9measResultPCell {

rsrpResult = 27rsrqResult = 23

}measResultNeighCells {

measResultListEUTRA[0] {physCellId = 295measResult {

rsrpResult = 19rsrqResult = 13

}}measResultListEUTRA[1] {

physCellId = 101measResult {

rsrpResult = 17rsrqResult = 0

}

RRC_MEASUREMENT_REPORT

-113 dBm

-121 dBm

-123 dBm

Above threshold_rsrp= -118dBm

measId=4 reportReconfig 4

TimeStamp: 3.26554

ID: 1545730

RRC_MEASUREMENT_REPORT

UL - DCCH {

message {

c1 {

measurementReport {

criticalExtensions {

c1 {

measurementReport_r8 {

measResults {

measId = 4

measResultPCell {

rsrpResult = 18

rsrqResult = 8

}

RRC_MEASUREMENT_REPORT

-122 dBm

Lower than threshold_rsrp= -118dBm

Real L3 Call Flow – Message View

Start Time: 2014-11-14 08:00

Timestamp Cell ID Message

0 1545730 RRC_RRC_CONNECTION_REQUEST

0.003 1545730 INTERNAL_PER_RADIO_UE_MEASUREMENT_TA

0.004 1545730 RRC_RRC_CONNECTION_SETUP

0.021 1545730 RRC_RRC_CONNECTION_SETUP_COMPLETE

0.023 1545730 S1_INITIAL_UE_MESSAGE

0.05 1545730 S1_INITIAL_CONTEXT_SETUP_REQUEST

0.057 1545730 RRC_SECURITY_MODE_COMMAND

0.058 1545730 RRC_RRC_CONNECTION_RECONFIGURATION

0.079 1545730 RRC_SECURITY_MODE_COMPLETE

0.086 1545730 RRC_RRC_CONNECTION_RECONFIGURATION_COMPLETE

0.087 1545730 S1_INITIAL_CONTEXT_SETUP_RESPONSE

0.099 1545730 RRC_MEASUREMENT_REPORT

0.123 1545730 RRC_RRC_CONNECTION_RECONFIGURATION

0.146 1545730 RRC_RRC_CONNECTION_RECONFIGURATION_COMPLETE

3.266 1545730 RRC_MEASUREMENT_REPORT

3.266 1545730 RRC_RRC_CONNECTION_RELEASE

3.267 1545730 S1_UE_CONTEXT_RELEASE_REQUEST

3.288 1545730 S1_UE_CONTEXT_RELEASE_COMMAND

3.289 1545730 S1_UE_CONTEXT_RELEASE_COMPLETE

ECM Connected

Current cell rsrpLower than threshold_rsrp

= -118dBm

UE Redirection to U900TimeStamp: 3.26623

ID: 1545730

RRC_RRC_CONNECTION_RELEASE

DL - DCCH {

message {

c1 {

rrcConnectionRelease {

rrc_TransactionIdentifier = 3

criticalExtensions {

c1 {

rrcConnectionRelease_r8 {

releaseCause = other

redirectedCarrierInfo {

utra_FDD = 3086

}

RRC_CONNECTION_RELEASE

1. releaseCause is other2. Blind Redirection to 3G,3. UTRA, FDD = 3086 (U900)

Thank you

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