1

Zach Lovell

Agilent Technologies

LTE/SAE Technology Overview &

Challenges

Agenda

LTE Market Overview

LTE & EPC Technology Overview

LTE & EPC Challenges

Short Intro to Agilent in LTE

2

Not just slides! LTE UE from MWC Feb 2009

Wireless evolution: Five competing 3.9G systems

Incre

asi

ng

eff

icie

ncy,

ban

dw

idth

an

d d

ata

rate

s

2GIS-136TDMA

PDCGSMIS-95ACDMA

IS-95Bcdma

HSCSD iMode2.5G GPRSIS-95BCDMA

3GE-GPRSEDGE

IS-95CCDMA2000

W-CDMAFDD

W-CDMATDD

TD-SCDMALCR-TDD

3.5GHSUPA

FDD & TDD1xEV-DO

Release B1xEV-DO

Release A1xEV-DORelease 0

HSDPAFDD & TDD

3.9G3.9GLTE

E-UTRAEDGE

EvolutionHSPA+

802.16eMobile

WiMAXTM

UMBcf 802.20

802.11g

802.11b

802.11a

802.16dFixed

WiMAX TM

802.11n

802.11h

WiBRO

New OFDM Systems! New OFDM System!

3

LTE Activity 2008 2009 2010 2011 2012

UE Device AvailabilityLTE won’t work without devices

Proof of ConceptWill LTE work & deliver the expected performance

IOTAre the standards interpreted in the same way by all

Trials & FOA’sVendor Selection & Testing in near commercial conditions

Early Adopter DeploymentsFirst to market but limited number of deployment sites

Full Commercial DeploymentsBuilding into full coverage network coverage

LTE Market Development Timelines

Prototypes Trial Handsets Commercial Handsets

RF/eNB Focused

Data only

Whole end to end network incl. IMS

Multi-Vendor eUTRAN/EPC

VoiceData

LTE Adoption is Gaining Momentum

14 LTE networks in service by end 2010

31 LTE networks in service by end 2012

4

Agenda

LTE Market Overview

LTE & EPC Technology Overview

LTE & EPC Challenges

Short Intro to Agilent in LTE

LTE/SAE Overview – Introduced in 3GPP Release 8

• Uses Orthogonal Frequency Division Multiple Access (OFDMA) in the Downlink

• Single Carrier Frequency Division Multiple Access (SC-FDMA) in the Uplink

• The LTE radio migration may occur via software upgrades (e.g. soft radios)

The LTE protocol & network architecture is characterized by three requirements:

• Support for the PS domain only. There will be no circuit switched (CS) domain nodes.

• Traditional Voice services are delivered using VoIP served by the IMS

• Tight delay targets for small roundtrip delays

• 5 ms for bandwidths of 5 MHz and greater ; 10 ms for the bandwidths below 5 MHz

• Reduced cost of the system

• Achieved with all IP infrastructure and flattened network architecture

LTE challenges carriers to review deployment & operational procedures

Network Overview - 3GPP R8 – LTE/SAE

Evolved Packet Core Evolved UTRAN

S1-MME

MMEeNB

eNB

Uu

MME

S1-U

PDN-GW

X2

S5SGi

HSS

S6a

PCRFS7

S-GWS10

S11

MRF CSCF ASS1-MME

IMS & other

Operator IP

Services

5

OFDM / OFDMA• Transmission variable up to system bandwidth

• Symbol period is long - defined by subcarrier spacing and independent of system bandwidth

• Users separated by FDMA & TDMA on the subcarriers

• Equalization is easy due to signal on freq domain, and free of multipath up to the CP length

• Ideal for MIMO

• Vulnerable to narrowband distortion and interference

• OFDMA’s dynamic allocation enables better use of the channel for multiple low-rate users and for the avoidance of narrowband fading & interference.

CDMA/W-CDMA• All transmissions at full system bandwidth

• Symbol period is short – inverse of system BW

• Users separated by orthogonal spreading codes

• Equalization and multipath resistance is difficult above 5 MHz

• Needs significant computing power to support MIMO

• Spreading protects from narrowband distortion and interference

LTE Fundamentals - Physical Layer

OFDMA

LTE Fundamentals – Air Interface – UL SC-FDMA

SC-FDMA

Data symbols occupy N*15 kHz for

1/N SC-FDMA symbol periods

60 kHz Frequency

fc

V

CP

15 kHzFrequency

fc

V

CP

OFDMA

Data symbols occupy 15 kHz for

one OFDMA symbol period

• SC-FDMA combines single carrier methods with the frequency allocation flexibility & long symbol time of OFDMA

• While OFDMA transmits 1 symbol per subcarrier in parallel, SC-FDMA transmits symbols in series at N times the

rate and occupies the same bandwidth

• Supports larger bandwidths than OFDMA without the high Gaussian PAR

• Resistant to multi-path due to the constant nature of each subcarrier

6

MIMO creates multiple parallel channels between transmitter and receiver. MIMO is using time

and space to transmit data (space time coding).

MIMO is a family of techniques:

• Use multiple channels to send the same information stream to achieve diversity (transmit

diversity)

• Improve coverage

• Use multiple channels to send multiple information streams (spatial multiplexing)

• Increase throughput

The LTE Air Interface - LTE MIMO

Evolved 3GPP Network Architecture

Evolved Packet Core (EPC)

Serving NetworkGSM/GPRS/EDGE Radio Access Network (GERAN)

UMTS Terrestrial Radio Access Network (UTRAN)

Core & Services Network

CS Core (Voice)

SGSN

MGWMSC

VLR HLRSMS

PCRF

NodeB

RNC

BTS

BSC

PCU

Evolved UTRAN (E-UTRAN)

UE

MS

Uu

Abis

Iub

RNC

Iur

UE

X2

Uu eNB

eNB

PS Core (Data)

GSM-ACS

PS

GPRS-Gb

PS

CS

Iu-CS

Iu-PS

S11

SAE-GW

MME

S5

S4S3

S1-UEvolved Node B

Radio Network Subsystem

Base Station Subsystem

S6a

Gx

SGW

SS7/SIGTRAN

RX

SGi

WCDMA HSPA/HSPA+

GSMEDGEEvolved EDGE

Um

S1-C

S12

Gn InternetOperator’s IP

Services(E.g. IMS, PSS…)

P-GW

GGSN

HSS CSCFMRF /MGW

S10

7

Network Overview - LTE Functional Nodes

eNBeNodeB

Radio Resource Management

• Bearer & Admission control

• RF Measurement Reporting

Scheduling

• Dynamic resource allocation to UE’s

• Transmission of Pages & broadcast information

Network Access Security (PDCP)

• IP header compression

• Ciphering of user data stream

EPC Network Selection

• MME Selection at UE attachment

• User Plane routing to SAE-GW

Combines the functionality of the UMTS NodeB & RNC

Network Overview – EPC Functional Nodes

MMEMobility

Management Entity

EPC Access

• Attachment & Service Request

• Security & Authentication

Mobility

• MME Selection for Intra-LTE handovers

• SGSN Selection for 3GPP I-RAT Handover

UE Tracking and Reach-ability

• Tracking Area List Management (idle or active)

Bearer management

• Dedicated bearer establishment

• PDN GW & SAE-GW selection

Equivalent to the SGSN for the Control Plane

8

Network Overview – EPC Functional Nodes

S-GWSAE Gateway

Packet routing & forwarding

between EPC & eUTRAN

Local Mobility Anchor for Inter eNB handover

I-RAT Mobility Anchor Function

• 3GPP 2G/3G Handover

• Optimized Handover Procedures (e.g. in LTE-CDMA)

Lawful Interception

Equivalent to the SGSN for the User Plane

Network Overview – EPC Functional Nodes

P-GWPDN Gateway

UE IP address allocation

Policy enforcement

(QoS)

Charging support

Lawful Interception

Mobility Anchor between 3GPP & non-3GPP

access systems

Equivalent to the GGSN

9

Network Overview – Control Plane Protocols

UU S1-C S6a

Network Access Security – NAS Ciphering Network Access Security – PDCP Ciphering Network Domain Security – IPsec Encryption

** Both IPv4 & IPv6 supported

Network Overview – User Plane Protocols

UU S1-U SGi /Gm

Application Domain Security – IPSec AKA Network Access Security – PDCP Ciphering Network Domain Security – IPsec Encryption

* SCTP Recommended Transport in TS 29.229 ** Both IPv4 & IPv6 supported

S5/8 Cx

10

EPC Fundamentals – QoS Model

Today’s 3G Services use best effort QoS Class for all PS services

• An LTE user can have up to 24 bearers, each with its own QoS Class

• In the EPC, the QoS parameters are a function of guaranteed & non-guaranteed bit rates defined by 9 QCI labels.

QoS Class

Identifier

L2 Packet

Delay

Budget

L2 Packet

Loss RateExample Services

QCI=1 (GBR) 100 ms 10-2 Conversational Voice

QCI=2 (GBR) 150 ms 10-3 Conversational Video (Live Streaming)

QCI=3 (GBR) 50 ms 10-3 Real Time Gaming

QCI=4 (GBR) 300 ms 10-6 Non-Conversational Video (Buffered Streaming)

QCI=5 (non-GBR) 100 ms 10-6 IMS Signalling

QCI=6 (non-GBR) 300 ms 10-6

Video (Buffered Streaming)

TCP-based (e.g., www, e-mail, chat, ftp, p2p file

sharing, progressive video, etc.)

QCI=7 (non-GBR) 100 ms 10-3 Voice, Video (Live Streaming) Interactive Gaming

QCI=8 (non-GBR) 300 ms 10-6Video (Buffered Streaming)

TCP-based (e.g., www, e-mail, chat, ftp, etc.)QCI=9 (non-GBR) 300 ms 10-6

PDN -GWSGWeNBUE

EPC Fundamentals – QoS Model

RB-ID S1-TEIDUL-TFT RB-ID S1-TEID S5/S8-TEID S5/S8-TEI DL-TFT

UL Service Data Flows DL Service Data Flows

Application / Service Layer

GBR – Service BlockingReal Time

Non GBR – Service Dropping Non Real-Time

Page 20

TFT = Traffic Flow Template

Radio Bearer S1 Bearer S5 Bearer

11

21

• 2x2 MIMO

• HARQ; Round Robin

• Best effort user: fixed SNR (23 dB aprox), UDP transfer

• GBR user: GBR = 10 Mbps, variable SNR, HD video streaming

With decreasing SNR, GBR user maintains desired rate by taking resources from best effort user, until SNR too low to support GBR.

eNB Scheduler and QoS – An LSTI Illustration

Agenda

LTE Market Overview

LTE & EPC Technology Overview

LTE & EPC Challenges

Short Intro to Agilent in LTE

12

Downlink peak data rates (64QAM)

Antenna config SISO 2x2 MIMO 4x4 MIMO

Peak data rate Mbps 100 172.8 326.4

Uplink peak data rates (Single antenna)

Modulation QPSK 16 QAM 64 QAM

Peak data rate Mbps 50 57.6 86.4

eNB

UE1

UE2

UE3

UE4

UE5

Challenges – Adaptive Modulation and Coding

64 QAM

16 QAM

QPSK

Who will have What coverage Where?

64 QAM requires 10dB Carrier to Interference ratio (C/I)

How do you achieve that much isolation without adding more sites?

Evolved Packet Core

Challenges – Collapsed Architecture

eNB

Inter Cell RRM

RB Control

Connection Mobility Control

Radio Admission Control

eNB Measurement

Configuration & Provisioning

Dynamic Resource

Allocation (Scheduler)

RRC

PDCP

RLC

MAC

PHY

Serving Gateway

Mobility

Anchoring

MME

NAS Security

Idle State Mobility Handling

SAE Bearer Control

Internet

S1

E-UTRAN

PDN Gateway

UE IP Address

allocation

Packet Filtering

How do you do RF Performance

Engineering & Optimization, when

all these functions are closed within

the eNB?

What is the

Cost?

13

Challenges – Monitoring Points & Data Sources

Different Data Sources yield different information

and

different levels of cost effectiveness.

Data Sources

Evolved Packet Core (EPC)

PCRF

PDNEvolved UTRAN (E-UTRAN)

UE

Uu

eNB

S11

S-GW

MME

P-GW

S5

S1-U

Evolved Node B

HSS

S6a

Gx

Internet

RXSGi

CSCF MRF

S1-C

UE Device

E.g. Drive Test

Passive Air

Interface Probe

Network Element

Internal Debug

eNB, MME etc.

Network Element

Internal Monitor

CPRI/OBSAI

Interface

Monitoring

Sx, X2, S5/S8 …

P-GW(PCEF)X2

Challenges – How will Voice be Delivered??

Two Leading Proposals for CS Services Delivery over EPS Access in R8

• CS Fallback

• Voice over LTE Generic Access (VoLGA)

CS Fallback

• Currently selected by 3GPP as a Part of Release 8

• Connected to E-UTRAN uses GERAN or UTRAN to Establish CS & SMS Services

• Co-Exist with IMS-based Services in Same Operator’s Network

• CS Service over IMS takes precedence over CS Fallback

VoLGA – Voice over LTE via Generic Access

• Connected and Uses EPS to Establish One or More CS Services, via Legacy CN Infrastructure

• Does Not Require E-UTRAN Coverage Overlap with GERAN or UTRAN Coverage

• Co-Exist with IMS-based Services and CS Fallback in Same Operator’s Network

• Simultaneous Use of VoLGA & IMS Services Possible, while Not So with CS Fallback

Conclusions of Feasibility Studies

• Overlapping Coverage between LTE/EPS and Legacy CS Systems:

• CS Fallback Approach Preferred – but significant issues exist

• Non-Overlapping Coverage between LTE/EPS and Legacy CS Systems:

• VoLGA Approach Preferred

14

Challenges – CS Fallback Architecture

UE E-UTRAN MMELTE-Uu S1-MME

GERAN

UTRAN

Um

Uu

SGSN

MSC

Server

SGs

Gs

A

Iu-cs

Gb

Iu-ps

S3

• Part of Release 8 – TS 23.272

• Forces user off LTE to make a call

• MSC server & SGSN upgrades – New SGs interface

Challenges – CS Fallback E-UTRAN Page, No PS HO

9a. Connection Reject

1a. CS Paging 1a. CS Paging

If the MSC is changed

SGSN

10. CS Call Establishment procedure

6. Location Area Update or Combined RA/LA Update

5. S1 UE Context Release

BSS/RNS

4. S1-AP: S1 UE Context Release Request

UE/MS MME MSC

3a. NACC, 3b. Signalling connection release

eNodeB

2. Optional Measurement Report

9. Paging Response

9b. Location Area Update or Combined RA/LA Update

9a. Signalling Connection Release

S-GW

1b. Extended Service Request

1d. S1-AP message with CS Fallback indicator

1c. CS Paging Reject

7a. Suspend (see TS 23.060)

8. Update bearer(s)

7b. Suspend Request / Response

Potential impact on call setup times (1.5 sec)

User may not be able to maintain LTE data session while in call

Extra

delay

before

starting

the call

setup

procedure

15

• Z1: Reference Point between UE and IWF (VANC)

– Similar to GAN Up Interface between MS and GANC

• Z2: Reference Point between MME and IWF (VANC)

– Similar to Sv interface for Single Radio Voice Call Continuity (SRVCC)

– per TS 23.216

Challenges – VoLGA 3GPP Reference Architecture

UE

BTS/

BSC

NodeB

/RNC

eNodeBS-GW/

PDN-GWS1-UP

IWF

(VANC)SGi

MSC/

VLRA

Iu/A

HSSD

Z1

PCRFRx

Gx

Iu

MMEZ2

S1-MME

The PS challenge still exists between the UE & the IWF

Challenges - KPIs are more than just technical data

Determines Network Optimization Target, Priorities and KPI Definitions

Best Mixed Voice & Data for

everybody

Best High Speed Data for selected

users

Best Coverage What about

Real World Conditions

Handset

profiles

Application

mix

Cell

Geometry

How will CS

services be

delivered?

Expected

Cell

Interference

Usage

Patterns

Business Objectives There are other considerations

16

Monitoring and KPIs – 3GPP Definitions

3GPP defines 5 basic KPI types

Accessibility: Can a connection to the network be obtained

• Provides no QoS information

Retainability: Can a connection to the network be maintained

• Often generalized as the drop call ratio

Integrity: What is the quality of the connection

• Since LTE supports only the PS domain, these measurements revolve around IP throughput and latency.

Mobility: Impact of mobility on the end user

• Measures the success of hand over procedures

Availability: Is the network available to be accessed

• Measured at the cell level

Challenges - KPI Definition

The Accessibility KPI as an example.

• Can be measured on the S1 interface by analyzing the ERAB establishment procedures.

• This is not enough by itself!!!

• In many cases, a service will require multiple radio bearers.

– E.g. Default bearer for signaling & dedicated bearer for media streaming

• The actual service accessibility needs to combine the success rates for both the default and the dedicated radio bearers

• The LTE accessibility KPI focuses on the E-UTRAN itself;

• This is insufficient to measure the accessibility of a specific service end-to-end

– Take a voice call establishment as an example, once a UE has obtained a connection to the access network it must now be able to reach the specific application server (AS) within the IMS.

• The Voice AS (or CSCF) can generally be calculated as:

KPI Definition is not always straight forward !!!

What KPI’s can be computed depends on particular interface(s) being monitored.

17

Agenda

LTE Market Overview

LTE & EPC Technology Overview

LTE & EPC Challenges

Short Intro to Agilent in LTE

Assurance SolutionsSS7, VoIP, IMS, 3G

Infrastructure Vendors

Service Providers

N2X Router Test

Signalling AnalyzerNetwork Analyzer

Triple Play Analyzer

Drive Test, Scanner, Portable Spectrum Analyzer

RF Analysis &Wireless Conformance Test

LTE Solutions across Lifecycle

Network

Plan &

Design

Install &

Commission

Optimize &

Maintain

Monitor &

Manage

Business

Applications

Network

Element

R&D,

Design,

Production

Functional Test

Load Test

IOT

18

Signaling Analyzer Real-Time for LTE/SAE

Increase Test Efficiency & Quality

• Expert Analysis

– Focus on the test not the tool

• Full Visibility

– LTE/SAE protocols & procedures

– Intertechnology Testing, 2G, 3G, VoIP/IMS, ...

• Remove the guess work

– Real –Time Performance Analysis & Benchmarking

– KPI’s & Measurements aligned to standards:

• 3GPP, LSTI & NGMN Requirements

• Decrease Cycle Times

• Parallel / Concurrent Testing

– Multi-User Simultaneous Analysis

• Test automation for centralized regression

LTE Real-Time Troubleshooting & Analysis

• Functional Test, I&V test

• Load and Stress

• Trial, Deployment & Optimization

E6474A DT

Data S/W

Mobile Phone Trace Data

• Active, Neighbor Sets

• Protocol Messaging

RF Receiver Data

•Ec/Io

•Pilots Sets

• Agg Ec/Io, Delay Spread

•Internal GPS timing

•Serial Port Protocol capture

Signaling

AnalyzerTrace Port

E6474A Data Tests

• HTTP, FTP, EMAIL

• WAP, SMS

• DIALUP, VOICE AVAIL

• Audio/Video Streaming

• Video Telephony

Receiver

TCP/IP Performance

• TCP Re-Tx, resets

• IP Throughput

• Duplicate packets

Session Evaluation

• Graphical display of call trace

parameters

• Correlation of IP & Mobile protocols

• Supports IP, PPP, SIP, RTP

The LTE Air Interface - Agilent’s Test Methodology

19

Agilent in Standards

Agilent has been closely involved with ETSI and 3GPP since 1991

• Current delegates

• RAN WG4 (LTE air interface) – Moray Rumney

• RAN WG5 (UE conformance test) – Andrea Leonardi & Muthu Kurmaran

• Agilent has hosted many 3GPP meetings,

• Main focus has been on RF requirements and testing of the Node B and UE

• Currently leading discussions in WG4 on HSPA+ & LTE higher order modulation

Agilent in LSTI (Member since Feb-2008)

• Agilent is active in all Working Groups (POC, IODT, IOT and Trial).

• Providing expertise in Test methodology, Test concepts and specific Test cases.

• Test tools are aligned to demonstrate the capabilities according to the different proof points of LSTI.

• Agilent provides tools for both Network infrastructure and Handset testing

Agilent is a contributor in datacom standards forums:

• ATM forum

• MPLS forum (MFA Forum)

• Metro Ethernet Forum etc.

Agilent LTE Book – Available Now

• LTE and the Evolution to 4G Wireless

• Agilents new LTE book delves into the new 3GPP LTE cellular technology, from both the technical and practical point of view, before its projected deployment in 2010.

• Written by Agilent s measurement experts, this LTE book offers valuable insight into LTE technology and its design and test challenges.

• In this 450-page book you will find chapters covering the following:

– An introduction to LTE

– Air interface concepts & Physical layer

– Upper layer signaling,

– System architecture evolution,

– RF design and verification challenges

– UE Conformance testing

– A look to 4G: LTE-advanced.

SART LTE/SAE Solution

Overview

20

Thank You

Agilent Technologies-- the supplier of choice for your

design and test needs during LTE development

• The leader in design and test tools

– Design and test tools ready when you need them

• First products shipping today

• New measurement products will follow throughout the

technology development cycle

– Committed to new measurement technologies and

active involvement in standards setting

Agilent Technologies

You drive the path to LTE, Agilent clears the way.

3GPP LTE Standards References

3GPP TS Title Interface(s)

24.301 Non-Access-Stratum (NAS) Protocol for Evolved Packet System (EPS); Stage 3 S1-C, S101

24.312 Access Network Discovery and Selection Function (ANDSF) Management Object (MO) S14

29.061 Interworking between PLMN supporting packet based services and PDN SGi

29.118 Mobility Management Entity (MME) - Visitor Location Register (VLR) SGs Interface Specs. SGs

29.168 Cell Broadcast Centre Interfaces with the Evolved Packet Core; Stage 3 SBc

29.212 Policy and Charging Control over Gx Reference Point Gx, Gxa, Gxc

29.214 Policy and Charging Control (PCC) over Rx Reference Point Rx

29.215 Policy and Charging Control (PCC) over S9 Reference Point S9

29.272 MME Related Interfaces Based on Diameter Protocol S6a, S6d, S13, S13’

29.273 EPS; 3GPP AAA Interfaces SWa/d/m/x, STa, S6b, H2, Pi*

29.274 Evolved General Packet Radio Service (GPRS); Tunneling Protocol for Control plane (GTPv2-C) S3-C, S4-C, S5/8-C, S10, S11

29.275 Proxy Mobile IPv6 (PMIPv6) based Mobility and Tunneling Protocols; Stage 3 S2a-C, S2b-C, S5/8-C (PMIP)

29.276 Optimized Handover Procedures and Protocols between EUTRAN Access and cdma2000 HRPD S101

29.277 Optimized Handover Procedures and Protocols between EUTRAN Access and 1xRTT Access S102

29.279 Mobile IPv4 (MIPv4) based Mobility Protocols; Stage 3 S2a-C

29.280 3GPP EPS Sv Interface (MME to MSC) for SRVCC Sv

29.281 GPRS Tunneling Protocol User Plane (GTPv1-U) S1-U, X2-U, S4-U, S5/8-U, S12-U

36.321 E-UTRA; Medium Access Control (MAC) Protocol Specification Uu

36.322 E-UTRA; Radio Link Control (RLC) Protocol Specification Uu

36.323 E-UTRA; Packet Data Convergence Protocol (PDCP) Specification Uu

36.331 E-UTRA; Radio Resource Control (RRC) Protocol Specification Uu, S1, X2, S3

36.413 E-UTRAN: S1 Application Protocol (S1AP) S1-C

36.423 E-UTRAN: X2 Application Protocol (X2AP) X2-C

21

3GPP TR 23.401 / 25.813

Network Overview – LTE – SAE Network Identifiers

• PLMN – Public Land Mobile

Network

• EPS – Evolved Packet

System

• MME – Mobility

Management Entity

• eNB – E-UTRAN Node B

• TAI - Tracking Area ID

• E-UTRAN – Evolved

Universal Radio Access

Network

• C-RNTI – Cell Radio

Network Temporary Identifier

• RA-RNTI – Random Access

RNTI

• UE – User Equipment

• IMEI – International Mobile

Equipment Identity

• IMSI (MSISDN) –

International Mobile

Subscriber Identity

• S-TMSI – SAE Temporary

Mobile Subscriber Identity

Network Overview – LTE Interfaces

• S1-MME: The S1-MME interface provides the control plane protocol between the Evolved UTRAN and MME.

• S1-U: The S1-U interface provides a per bearer user plane tunneling between the Evolved UTRAN and Serving GW.

– It contains support for path switching during handover between eNodeBs.

– S1-U is based on the GTP-U protocol that is also used for Iu user plane in the Rel-7 architecture.

• S3: The S3 interface enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state.

– It is based on the GTP protocol and the Gn interface as defined between SGSNs.

• S4: The S4 interface provides the user plane with related control and mobility support between GPRS Core and the 3GPP Anchor function of Serving GW and is based on the GTP protocol and the Gn reference point as defined between SGSN and GGSN.

• S5: The S5 interface provides user plane tunneling and tunnel management between Serving GW and PDN GW.

– It is used for Serving GW relocation due to UE mobility, and if the Serving GW needs to connect to a non-collocated PDN GW for the required PDN connectivity.

– There are two variants of the S5 interface, one based on the GTP protocol and one IETF variant based on Proxy Mobile IPv6 (PMIP).

22

Network Overview – LTE Interfaces, continued…

• S6a: Enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface) between MME and HSS.

• S7: Provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW. The interface is based on the Gx interface.

• S8a: Is the roaming interface in case of roaming with home routed traffic. It provides user plane with related control between the Serving GW in the VPLMN and the PDN GW in the HPLMN.

– It is based on the GTP protocol and the Gp interface as defined between SGSN and GGSN.

– S8a is a variant of S5 for the roaming (inter-PLMN) case. There is also an IETF variant of called S8b that is based on Proxy Mobile IPv6 (PMIP).

• S10: Is between MMEs and provides MME relocation and MME to MME information transfer

• S11: Is the interface between MME and Serving GW.

• SGi: Is the interface between the PDN GW and the packet data network.

– This interface corresponds to Gi and Wi interfaces and support any 3GPP or non-3GPP access.

• Rx+: Is the interface between the AF and the PCRF.