4G Mobile Network LTE Vladimir Settey

7/31/2019 4G Mobile Network LTE Vladimir Settey

1/52

Cisco Public 1 2010 Cisco and/or its affiliates. All rights reserved.

4G Mobile NetworksLong Term Evolution (LTE)

Vladimir Settey


2/52

2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 2

The revolution is here (smartphones / tablets / netbooks) Broadband, anytime, anywhere Flat-rate data ? Data growth exponential; revenue growth linear. Scaling the network for data


3/52


Evolution of Mobile Networks

LTE Architecture Overview

EPC Mobility

Services in LTE


4/52



5/52


Voice oriented architecture Re-define fixed wireline services (e.g. SS and IN) SMS is a signalling transport rather than a data service Network transport based on TDM

There was wireless ISDN (aka GSM)

Base Station

Controller

(BSC)

Mobile Switching Center +

Visitor Locatio(MSC/VLR)

n Register

Base Transceiver

System (BTS)Mobile

Station

GSM

Radio

GSM

Radio16/64

kbps

16/64

kbps

64/2048

kbps

64/2048

kbps

LAP-Dm LAP-Dm LAP-D LAP-D

RadioResource

Mgmt RR BTSM BTSM

RR

BSSAP

MobilityMgmt

ConnectionMgmt

BSSAP

DTAP

MobilityMgt

ConnectionMgmt

64 kbps

MTP

TUP

SCCP

TCAP

ISUP

INAP

MAP

BSSMAP

MTP/MTPb

SCCP

MTP/b

SCCP

Home Location

Register (HLR)Service Control

Point (SCP)


6/52


One burst every TDMA frame was sufficient to transport a speechframe with source rate of 13 kbit/s

GSM Phase 2 (circa 1996) added Circuit Switched Data supportoffering 9.6 kbit/s service

High Speed CSD consisted in aggregating multiple timeslot for asingle user but resource intensive

BSC MSC

Modem Interworking Function (IWF)

Modified V.110

3.1 kHz audio

or

V110 64k UDI


7/52


BSCMSC/VLR Gateway MSC

BTS

GSM

Radio

GSM

Radio64 kbps 64 kbps L1bis

MAC

IP

RLC

LLC

SNDCP

Relay MAC

RLC

Nw Services

BSSGP

Relay

L1bis

Nw Services

BSSGP

LLC

SNDCP

L1

L2

IP

UDP

GTP

Relay

L1

L2

IP

UDP

GTP

IP

Packet Control

Unit (PCU)Serving GPRS

Support Node

(SGSN)

Gateway GPRS

Support Node

(GGSN)

IP


8/52


First step towards an all IP network Designed to accommodate greater packet throughput (up to

2Mbits/s announced In reality, can support up to 384 kbit/s)

Core network remains largely unchanged from 2.5G Migration to ATM for Radio Access Transport More control into the RNC

3G RNC

3G MSC

3G SGSN GGSN

IP

ATM/AAL2

ATM/AAL5

Node B

PSTN


9/52


So hopefully WCDMA got it right on packet services

Radio NetworkController (RNC)

3G SGSN GGSN

Iu-ps Gn/Gp

WCDMA

Radio

WCDMA

RadioATM

MAC

IP

RLC

PDCP

Frame

Protocol

AAL2

ATM

AAL2

MAC

RLC

PDCP

ATM

AAL5

IP

UDP

GTP-U

IP

UDP

GTP-U

IP

UDP

GTP-U

ATM

AAL5

L1

L2

IP

UDP

GTP-U

L1

L2

IP

NodeB


10/52


Still Voice over CS bearer on the radio access, data bearer notsuitable (latency, overhead)

Option to transport Voice over IP in the Core (see TS 23.205) Introduction of SS7oIP transport

Iu-cs

IP

MGW MGW

MSC-s MSC-s

HLR

ATM

Iu-UP

L1/2IPAAL2

UDP

RTP

L1/2

IP

M3UA

TCAP

INAP

MAP

SCTP

SCCPBICC

orSIP-T

H.248

Nb-UP


11/52


L1

RLC

PDCP

MAC

UDP

GTP-U

IP

Serving RNC 3G SGSN GGSN

GnIu-ps

IP

UDP

GTP-U

L1

L2

IP

IP

UDP

GTP-U

L1

L2

IP

UDP

GTP-U

L1

AAL5/ATMAAL5/ATM

L1

FrameProtocol

AAL2/ATM

RLC

PDCP

WCDMA

IP

MAC

L1

FrameProtocol

AAL2/ATM

WCDMA

Drift RNC

L1

FP

L1

FP

AAL2 AAL2

Node B

HSDPA Removes Drift RNC and

adds intelligence to the Node B

Direct Tunnel allows

SGSN to remove itselffrom data plane

HSPA+: Distribute RNC

Data plane to Node B

MAC-HS MAC-HSL2


12/52


DL: 384 kps

UL: 384 kbps

DL: Up to

14.4 MbpsUL: 384 kbps

2007 2008 2009 2010+

DL:Up to

14.4 MbpsUL: 5.7 Mbps

DL: 28 MbpsUL: 11 Mpbs

DL: 42 MbpsUL: 11 Mpbs

Rel-99

WCDMA

Rel-5

HSDPA

Rel-6

HSUPA

Rel-7

MIMO 2x2

Rel-8

64 QAM

HSDPA:16 QAM DL

14.4 Mbps

HSDPA: Alwayson scaling

HSUPA:

5.7 Mbps

HSDPA:64 QAM, MIMO

HSUPA: 16QAM

Always on

scaling

HSDPA:64 QAM

and MIMO


13/52


Highlighting the growing importance of IP transport

3G MSC-S

3G SGSN GGSN

Core IP

IP RAN

w/ ATM PW

or Native IP

Node B

PSTN

3G RNC

3G MGW

HLR/HSS

SGW


14/52


Evolved Packet System (EPS) is the technology direction for 3GPPbased networks

Long Term Evolution (LTE) is the next generation 3GPP radio accessnetwork

Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)

System Architecture Evolution (SAE) is the 3GPP next generationstandard for mobile networks providing:Increased Bandwidth

End-to-End IP

Simplified Architecture

Support for multiple radio access technologies

Evolved Packet Core (EPC) is the next generation 3GPP packet coreConsists of (3) main components (MME, SGW, and PGW)


15/52


Radio Side (Evolved UTRAN - EUTRAN)Improvements in spectral efficiency, user throughput, latency

Simplification of the radio network

Efficient support of packet based services: Multicast, VoIP, etc.

Network Side (Evolved Packet Core - EPC)Improvement in latency, capacity, throughput, idle to active transitions

Simplification of the core network

Optimization for IP traffic and services

Simplified support and handover to non-3GPP access technologies


16/52


Higher Bandwidth (>100 kbps per user on average) and improvedlatency

Transmission and transition delays


17/52



18/52


Duplex FDD and TDD

Channel Bandwidth 1.25 20 MHz

Modulation Type QPSK, 16-QAM, 64-QAM

Multiple Access Technique DL: OFDMA, UL: SCFDMA

TDMA Frame Duration 10ms with 1ms subframe

Number of symbols per frame 140

Sub-carrier Spacing 15 kHz

Symbol Duration 66.7 us

Cyclic Prefix 4.69 us, 16.67 us

Multipath Mitigation OFDM / Cyclic Prefix

eNB Synchronization Frequency (FDD, TDD)

Time (TDD, MBSFN)

Forward Error Correction 1/3 Convolutional and Turbo

Advanced Antenna Techniques MIMO 2x2, 4x4


19/52


Frequency

Time"CDMA"(3G)"

OFDM"

TDMA"(2G)"

OFDMA"(LTE & WiMAX)"

Sub-Cha

nnel

(Group

of

Frequencies)

S

ub-Channel

(Groupof

Frequencies)

user A

user B

user C

Frequency

FDMA"

Freque

ncy


20/52


Frequency One Resource Element

Sub-carrier Spacing

15 kHz


21/52


5 MHz 10 MHz

20 MHz

3 MHz

1.4 MHz


22/52


QPSK ( 55% of cell area)

16QAM (18% of cell area)



Maximising the bandwidth made available to the users by selecting theoptimum modulation scheme (QPSK, 16QAM, 64QAM, etc.)


23/52


DownlinkPhysical Broadcast Channel (PBCH)

Physical Downlink Shared Channel (PDSCH)

Physical Downlink Control Channel (PDCCH)

Physical Control Format Indicator Channel (PCFICH)

Physical Hybrid ARQ Indicator Channel (PHICH)

UplinkPhysical Random Access Channel (PRACH)

Physical Uplink Shared Channel (PUSCH)

Physical Uplink Control Channel (PUCCH)


24/52



25/52


3GPP Access

E-UTRANPGWSGWeNodeB

PCRF

OperatorsIP Services

(e.g. video, IMS)

HSS

S11

(GTP-C)

S1-U

(GTP-U)

S2b

(PMIPv6,

GRE)

MME

S5/8 (PMIPv6, GRE)

S6a

(DIAMETER)

S1-MME

(S1-AP)

GERAN

S4 (GTP-C, GTP-U)

UTRAN

SGSN

Trusted

Non-3GPPIP Access

Untrusted

Non-3GPPIP Access

S3

(GTP-C)

S12 (GTP-U)

S10

(GTP-C)

S5/8 (GTP-C, GTP-U)

Gx (DIAMETER) Gxb

SWx (DIAMETER)

STa (RADIUS,

DIAMETER)

ePDG

AAA

SWn

S6b

(DIAMETER)

SWm

(DIAMETER)

SGi

SWa

Gxa

Rx+ (DIAMETER)

S2c

UE

S2a

(PMIPv6, GRE

MIPv4 FACoA)

Gxc

UEUE


26/52


3GPP Access

E-UTRAN PGWSGWeNodeB

PCRF

OperatorsIP Services

(e.g. video, IMS)

HSS

S11

(GTP-C)

S1-U(GTP-U)

S2b

(PMIPv6,

GRE)

MME

S5/8 (PMIPv6, GRE)

S6a

(DIAMETER)

S1-MME

(S1-AP)

GERAN

S4 (GTP-C, GTP-U)

UTRAN

SGSN

Trusted

Non-3GPPIP Access

Untrusted

Non-3GPPIP Access

S3

(GTP-C)

S12 (GTP-U)

S10

(GTP-C)

S5/8 (GTP-C, GTP-U)

Gx (DIAMETER) Gxb

SWx (DIAMETER)

STa (RADIUS,

DIAMETER)

ePDG

AAA

SWn

S6b

(DIAMETER)

SWm

(DIAMETER)

SGi

SWa

Gxa

Rx+ (DIAMETER)

S2c

UE

S2a

(PMIPv6, GRE

MIPv4 FACoA)

Gxc

UEUE

Mobility Management Entity

E-UTRAN Control Plane with 2G/3G interworking

(no user plane handling) Interacts with HSS for user

authentication, profile download, etc. Interacts with eNodeB and SGW for

SGW selection, tunnel control, paging,

handovers, etc. Interacts with SGSN for 2G/3G


27/52


3GPP Access


PCRF

Operators

IP Services(e.g. video, IMS)

HSS

S11

(GTP-C)

S1-U

(GTP-U)

S2b

(PMIPv6,

GRE)

MME

S5/8 (PMIPv6, GRE)

S6a

(DIAMETER)

S1-MME

(S1-AP)

GERAN

S4 (GTP-C, GTP-U)

UTRAN

SGSN

Trusted

Non-3GPPIP Access

Untrusted

Non-3GPPIP Access

S3

(GTP-C)

S12 (GTP-U)

S10

(GTP-C)

S5/8 (GTP-C, GTP-U)

Gx (DIAMETER) Gxb

SWx (DIAMETER)

STa (RADIUS,

DIAMETER)

ePDG

AAA

SWn

S6b

(DIAMETER)

SWm

(DIAMETER)

SGi

SWa

Gxa

Rx+ (DIAMETER)

S2c

UE

S2a

(PMIPv6, GRE

MIPv4 FACoA)

Gxc

UEUE

Home Subscriber Services (HSS)

Centralised database holding user profile:

Interacts with MME for userauthentication and profile download

Stores current location information (e.g.assigned MME, Serving SGW)

One or more subscription profilescontaining IMSI, QoS, Services, etc.


28/52


3GPP Access


PCRF

Operators


HSS

S11

(GTP-C)

S1-U

(GTP-U)

S2b

(PMIPv6,

GRE)

MME

S5/8 (PMIPv6, GRE)

S6a

(DIAMETER)

S1-MME

(S1-AP)

GERAN

S4 (GTP-C, GTP-U)

UTRAN

SGSN

Trusted

Non-3GPPIP Access

Untrusted

Non-3GPPIP Access

S3

(GTP-C)

S12 (GTP-U)

S10

(GTP-C)

S5/8 (GTP-C, GTP-U)

Gx (DIAMETER) Gxb

SWx (DIAMETER)

STa (RADIUS,

DIAMETER)

ePDG

AAA

SWn

S6b

(DIAMETER)

SWm

(DIAMETER)

SGi

SWa

Gxa

Rx+ (DIAMETER)

S2c

UE

S2a

(PMIPv6, GRE

MIPv4 FACoA)

Gxc

UEUE

Serving Gateway

Data plane anchoring for 3GPP access and 2G/

3G bearer plane interworking Anchor point in visited network for

3GPP Access (2G/3G/LTE) Processes all IP packets to/from UE

(QoS control, LI)

Uses network-based mobility towardsPDNGW (GTP or PMIPv6)


29/52


3GPP Access


PCRF

Operators


HSS

S11

(GTP-C)

S1-U

(GTP-U)

S2b

(PMIPv6,

GRE)

MME

S5/8 (PMIPv6, GRE)

S6a

(DIAMETER)

S1-MME

(S1-AP)

GERAN

S4 (GTP-C, GTP-U)

UTRAN

SGSN

Trusted

Non-3GPPIP Access

Untrusted

Non-3GPPIP Access

S3

(GTP-C)

S12 (GTP-U)

S10

(GTP-C)

S5/8 (GTP-C, GTP-U)

Gx (DIAMETER)Gxb

SWx (DIAMETER)

STa (RADIUS,

DIAMETER)

ePDG

AAA

SWn

S6b

(DIAMETER)

SWm

(DIAMETER)

SGi

SWa

Gxa

Rx+ (DIAMETER)

S2c

UE

S2a

(PMIPv6, GRE

MIPv4 FACoA)

Gxc

UEUE

Packet Data Network Gateway (PGW)

Subscriber-aware data plane anchoring for all

access networks Anchor point in home or visited network

for all IP-based access (3GPP or not) Session-based user authentication and

IP address allocation (IPv4/v6)

Processes all IP packets to/from UE(QoS control, PCEF, LI)


30/52


3GPP Access


PCRF

Operators


HSS

S11

(GTP-C)

S1-U

(GTP-U)

S2b

(PMIPv6,

GRE)

MME

S5/8 (PMIPv6, GRE)

S6a

(DIAMETER)

S1-MME

(S1-AP)

GERAN

S4 (GTP-C, GTP-U)

UTRAN

SGSN

Trusted

Non-3GPPIP Access

Untrusted

Non-3GPPIP Access

S3

(GTP-C)

S12 (GTP-U)

S10

(GTP-C)

S5/8 (GTP-C, GTP-U)

Gx (DIAMETER) Gxb

SWx (DIAMETER)

STa (RADIUS,

DIAMETER)

ePDG

AAA

SWn

S6b

(DIAMETER)

SWm

(DIAMETER)

SGi

SWa

Gxa

Rx+ (DIAMETER)

S2c

UE

S2a

(PMIPv6, GRE

MIPv4 FACoA)

Gxc

UEUE

Policy&Charging Rule Function (PCRF)

User and application-aware policy decision point:

Interacts with PGW to enforce persession or per flow policies

Gets event notification from PGW(mobilty and/or traffic related)

Interacts with application for admissioncontrol and policy definitiion

Supports roaming capabilities


31/52


3GPP Access


PCRF

Operators


HSS

S11

(GTP-C)

S1-U

(GTP-U)

S2b

(PMIPv6,

GRE)

MME

S5/8 (PMIPv6, GRE)

S6a

(DIAMETER)

S1-MME

(S1-AP)

GERAN

S4 (GTP-C, GTP-U)

UTRAN

SGSN

Trusted

Non-3GPPIP Access

Untrusted

Non-3GPPIP Access

S3

(GTP-C)

S12 (GTP-U)

S10

(GTP-C)

S5/8 (GTP-C, GTP-U)

Gx (DIAMETER) Gxb

SWx (DIAMETER)

STa (RADIUS,

DIAMETER)

ePDG

AAA

SWn

S6b

(DIAMETER)

SWm

(DIAMETER)

SGi

SWa

Gxa

Rx+ (DIAMETER)

S2c

UE

S2a

(PMIPv6, GRE

MIPv4 FACoA)

Gxc

UEUE

Enhanced Packet Data Gateway (ePDG)

Support for untrusted non-3GPP access

EPC point of attachment for useraccessing over other non-owned access

Terminates IPSec tunnel from UEestablished with IKEv2 & EAP-AKA

Supports network-based IP mobilitytowards the selected PGW (PMIPv6)


32/52


E- UTRAN

MME

eNB

UE

HSS

S6a

(Auth Vectors)

EPS AKA via S6a

Challenge and keysexchange

Mutual Authentication

NAS Integrity/CipheringRRC Integrity and ciphering

U-Plane Ciphering

USIM required for LTE Different set of keys used for ciphering, derived from the same

original K stored in the USIM/HSS


33/52


UE

MME

S-GW

Evolved UTRAN (E-UTRAN) Evolved Packet Core (EPC)

HSS

PCRF

PDN-GW

MAC

RLC

PDCP

OFDMA

NAS

MAC

RLC

PDCP

OFDMA

L2

IP

L1

SCTP

S1-APRRC RRC

L2

IP

L1

SCTP

S1-AP

NAS

S1-MME

36.413

S1-MME

eNodeB


34/52


UE

MME

S-GW


HSS

PCRF

PDN-GW

IP

L1

L2

IP (user)

IPUDP

GTP-U

L1

L2MAC

RLC

PDCP

OFDMA

IP (user)

MAC

RLC

PDCP

OFDMA

IPUDP

GTP-U

L1

L2

IPUDP

GTP-U

L1

L2

PMIP

S1-U S5/S8

S1-U

36.414

GRE GREUDP

PMIP GTP-US5/S8

29.274

(GTP)-

29.275

(PMIPv6)

eNodeB


35/52


UE

MME

S-GW


HSS PCRF

PDN-GW

X2

L2

IP

L1

SCTP

X2-AP

L2

IP

L1

SCTP

X2-AP

X2-C

L2

IP

L1

UDP

GTP-U

L2

IP

L1

UDP

GTP-U

X2-U

36.423 36.424

eNodeB


36/52


UE

eNodeB

MME

S-GW


HSSPCRF

PDN-GW

Gx

L2

IP

L1

SCTP

DIAMETER

Gx

L2

IP

L1

SCTP

DIAMETER

L2

IP

L1

SCTP

DIAMETER

S6a

L2

IP

L1

SCTP

DIAMETER

29.272 29.212

S6a


37/52


Extract from 3GPP TS 23.401 V8.3.0 (2008-09)

A UE shall perform the address allocation procedures for at least one IPaddress (either IPv4 or IPv6)

PDN types IPv4, IPv6 and IPv4v6 are supported

/64 IPv6 prefix allocation via IPv6 Stateless Address autoconfigurationaccording to RFC 4862, if IPv6 is supported (Mandatory)

IPv6 parameter configuration via Stateless DHCPv6 according toRFC 3736 (Optional)

During default bearer establishment, the PDN GW sends the IPv6 prefix

and Interface Identifier to the SGW, and then the S-GW forwards theIPv6 prefix and Interface Identifier to the MME or to the SGSN. The MMEor the SGSN forwards the IPv6 Interface Identifier to the UE.


38/52



39/52


Idle Mode Mobility proceduresUE Initial Attach

Periodic Location Update / Inter- and intra-RAT reselection

UE Detach

Active Mode MobilityIntra-RAT Intra- and inter-area handover

Inter-RAT handover

RRC StatesRRC-IDLERRC-CONNECTED


40/52


3G UE 3G RNC 3G SGSN 3G GGSN HLR

1. Attach Request

2. Identity Request/Response

3. UE Authentication (EAP-AKA) and Ciphering Start

4. User Profile Download

5. Attach Accept/Complete


41/52


3G UE MME S-GW HSS

1. Attach Request

2. Identity Req/Rsp

3. UE Authentication (EAP-AKA) and Ciphering Start

4. User Profile Download

5. Bearer Request

10. Attach Accept/Complete

PCRF

P-GW

6. Bearer Request

Bearer Authorisation

(inc. IP @, policy)

8. Bearer Accept9. Bearer Accept


42/52


13. Update PDP Req

3G UE Old RNC Old SGSN GGSN

2. Relocation Required

5. RAB establishment at target NodeB

1. HO Preparation

Target RNC Target SGSN

3. Fwd Reloc Req

6. Relocation Request Ack

4. Relocation Request

7. Fwd Reloc Ack8. Relocation Command

9. Reconfig Radio

10. SRNS Context Transfer

12. Relocation Detected

15. Update PDP Ack

11. Relocation Detected

Relocation Completion including Radio resource release at Old RNC and RAU procedure

14. Policy Ctrl(optional)


43/52


3. Create Session Req

3G UE MME Old S-GW

2. Path Switch Req

Target S-GW P-GWOld eNB Target eNB

Fwd Data

1. HO prep and exec

Established 2-way Bearer

DL Data

4. Modify Bearer Req

6. Modify Bearer Ack

5. Policy Ctrl

7. Create Session Resp

8. Path Switch Resp

9. Release10. Delete Session Req/Resp

Established 2-way Bearer


44/52


3G UE Old S-GW

8. HO Command

Target S-GW

3. Create Session Req/Resp

P-GWOld MME Target MME

1. HO preparation

14. Modify Bearer Req

16. Modify Bearer Resp

15. Policy Ctrl

5. Create Indirect TunnelReq/Resp

4. HO prep at Target eNB

7. Create Indirect TunnelReq/Resp

6. Fwd Reloc Resp

9. HO Command

2. Fwd Reloc Req

11. HO Notify

10. eNB context transfer

13. Update Session Req

17. Update Session Resp

Relocation Completion including radio resource release at Old

eNB and Session and Fwd tunnel tear down at old MME/SGW

12. Reloc Complete Req/Resp


45/52



46/52


The EPS architecture (3GPP Rel 8)is the first 3GPP all-IP architecture Voice and SMS are still

the cash cows for mobile operators

Migration is critical

User experience must be preserved

CSFB is the interim solution recommended by NGMN IMS is the target solution for Telephony and Multimedia Services OneVoice IMS profile simplifies implementation for VoLTE NGMN and OneVoice initiatives reduce risk of industry fragmentation SMS typically required before voice due to EU regulatory requirements

for data roaming services


47/52


During EPC attach, CSFB UEs are also attached over SGs to MSC MME maintains mapping of TA to LA to determine appropriate MSC toestablish SGs association with SMS can be delivered/sent without FallBack to legacy radio (SGs interface

includes SMS payload capability)

S1-MME

SGs

S11

S6a

IuCS / A

S1-UCSFB UE E-UTRAN

Serving/

PDN GW

MME

UTRAN /

GERANMSC

HSS

Incoming SMS1

SMS is delivered via SGs interface2


48/52


Additional complexity / upgrades required on CS core to support use-case where the MSC sending Page is different to MSC receiving Page

response (i.e. TA to LA mapping is inaccurate due to cell breathing orother circumstances)

This capability (Roaming Retry) requires upgrades on GMSC, VMSCand HLR. Introduces further termination latency.

S1-MME

SGs

S11

S6a

IuCS / A

S1-UCSFB UE E-UTRAN

Serving/PDN GW

MME

CSFB UEUTRAN /GERAN

MSC

HSS

Incoming Call delivered to VMSC whichhas SGs association for this subscriber

1

UE is paged via the SGs interface2

UE retunes to 2G/3G RAT on receipt

of page

3

UE Responds to paging incoming call terminated viastandard 2G/3G procedures

4


49/52


To enable mid-call mobility, S-CSCF anchors call at SCC AS TAS provides end-user services (e.g. IR.92) MGCF provides breakout to PSTN or other CS networks

ISC

Mw

S1-MME

Sv

S11

Mg

SGi(Gm from UE)

S6a

IuCS / A

IuPS / Gb

S3

S1-U

Cx

IMS (HPLMN)

P-CSCF

SR-VCC UE E-UTRANServing/PDN GW

MME

UTRAN /GERAN

MSC Server(SR-VCC)

SGSN(SR-VCC)

I/S-CSCF

HSS

TASSCC AS IP-SM-GW

MGCF

Subscriber has already registeredinto IMS following EPC attach

UE OriginatesCall

1

2


50/52


SCC AS performs leg management hides mobility events from other IMSapplication servers

SR-VCC only works in one direction LTE 2G/3G Requires upgrades on legacy MSC infrastructure

ISC

Mw

S1-MME

Sv

S11

Mg

SGi

(Gm from UE)

S6a

IuCS / A

IuPS / Gb

S3

S1-U

Cx

IMS (HPLMN)

P-CSCF

SR-VCC UE E-UTRANServing/

PDN GW

MME

SR-VCC UEUTRAN /

GERAN

MSC Server

(SR-VCC)

SGSN

(SR-VCC)

I/S-CSCF

HSS

TASSCC AS IP-SM-GW

MGCF

UE retunes to 2G/3GRAT during active call

1

New call legestablished

2

SCC AS performsbearer managementand tears down original

leg

3


51/52


CSFB VoIMS

End-User Services Re-use legacy implementation OneVoice (IR.92) provides baseline. Alloperator proprietary services and extensions

must be ported to IMS.

Regulatory Re-use legacy implementation National regulatory services must beimplemented in IMS.

Service Differentiation Restricted to only services deliverable fromlegacy core.

IR.92 services can be blended with other IMSservices such as presence, RCS, rich

messaging.

End-user Experience Significant post-dial delay. Retuning fromCS back to LTE may take some time

impact to data services.

No retuning required to access CS equivalentservices. Still industry concerns regarding SR-

VCC latency.

Complexity Medium CS core requires upgrades forSGs interface and also to support Roaming

Retry.

High Significant new network infrastructurerequired. SR-VCC extremely complex.

Intensive service porting to ensure full legacyparity.

Cost Unknown upgrades must come fromexisting CS vendors. Believed that legacy

vendors are using this to their advantageto seek premium.

High large investment required for newinfrastructure. However, diverse range of

vendors opens door for innovative deals/solutions.


52/52

Thank you.

Documents

4G Mobile Network LTE Vladimir Settey