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DEEKSHA TECH GROUP

Module 4

LTE Protocols and Channels

AgendaRelationship between

Protocols Architecture Interfaces

Layer 2 Functions and Data Flow

Multiplexing of Channels

Channel Types Logical Transport Physical

LTE Interfaces

Radio Interface and X2 Interface

TS 36.421

User PDUsUser PDUs

GTP-UGTP-U

UDPUDP

IPIP

L1/L2L1/L2

TS 36.424

X2-UP(User Plane)

X2-CP(Control Plane)

X2-APX2-AP

SCTPSCTP

IPIP

L1/L2L1/L2TS 36.421

TS 36.422

TS 36.423

TS 36.420[X2 general aspects & principles)

TS 29.281

LTE-Uu Air interface of EUTRAN Based on OFDMA in downlink and SC-FDMA

in uplink FDD and TDD duplex methods Scalable bandwidth: from 1.4 up to 20 MHz Data rates up to 100 Mbps (DL), 50Mbps

(UL)

(E)-RRC(E)-RRCUser PDUsUser PDUs

PDCPPDCP

RLCRLC

MACMAC

LTE-L1 (FDD/TDD-OFDMA/SC-FDMA)LTE-L1 (FDD/TDD-OFDMA/SC-FDMA)

TS 36.300

NAS ProtocolsNAS Protocols

Control Plane (CP) User Plane (UP)

TS 36.323

TS 36.322

TS 36.321

TS 36.331

TS 24.301

TS 36.2xx

X2 Inter eNB interface Handover coordination without involving the

EPC X2AP: signaling Application protocol During HO, Source eNB forward downlink

packets buffered or arriving from the serving gateway to the target eNB.

This will avoid loss of packets during inter-eNB handover.

S1-MME & S1-U Interfaces

MME

ServingGateway

S1-MME(Control Plane)

S1-U(User Plane)

NAS ProtocolsNAS Protocols

S1-APS1-AP

SCTPSCTP

IPIP

L1/L2L1/L2

User PDUsUser PDUs

GTP-UGTP-U

UDPUDP

IPIP

L1/L2L1/L2

TS 36.411

TS 36.411

TS 36.412

TS 36.413

TS 36.414

TS 36.410[S1 general aspects & principles]

eNB

TS 29.281

TS 36.410[S1 general aspects & principles]

TS 24.301

S1-MME Control interface between eNB and MME MME and UE will exchange NAS signaling

via eNB through this interface. E.g.: if a UE performs a tracking area

update the TRACKING AREA UPDATE REQUEST message will be sent from UE to eNB and the eNB will forward the message via S1-MME to the MME.

S1AP:S1 Application Protocol

S1-U User Plane interface between eNB and serving

gateway. It is a pure user data interface Which Serving GW a user’s SAE bearer will have to

use is signaled from the MME of this user.

EUTRAN and EPC - S1 Flex

1

2

3

eNB 1 Single S1-MME Single S1-U

eNB 2 Single S1-MME Multiple S1-US1Flex-U

eNB 3 Multiple S1-MMES1Flex Single S1-U

eNB 4 (Not shown in picture)

- Multiple S1-MMES1Flex- Multiple S1-US1Flex-U

S10 and S6a InterfaceS6a

(Control Plane)

MME HSS

S6a Appl.S6a Appl.

TCP/SCTPTCP/SCTP

IPIP

L1/L2L1/L2

DIAMETERDIAMETERMME

S10(Control Plane)

UDPUDP

IPIP

L1/L2L1/L2

GTP-CGTP-CTS 29.274 TS 29.272

S6a Interface between the MME and the HSS The MME uses it to retrieve subscription

and authentication information from HSS (handover/tracking area restrictions, external PDN allowed, QoS, etc.) during attaches and updates

The HSS can during these procedures also store the user’s current MME address in its database.

S10 Interface between different MMEs Used during inter-MME tracking area

updates (TAU) and handovers Inter-MME TAU: The new MME can

contact the old MME, to retrieve data about identity (IMSI), security information (security context, authentication vectors) and active SAE bearers (PDN gateways to contact, QoS, etc.)

Obviously S10 is a pure signaling interface, no user data runs on it.

S11 Interface

ServingGateway

MME

S11(Control Plane)

UDPUDP

IPIP

L1/L2L1/L2

GTP-CGTP-CTS 29.274

S11 Interface between MME and a Serving

GW A single MME can handle multiple

Serving GW each one with its own S11 interface

Used to coordinate the establishment of SAE bearers within the EPC

SAE bearer setup can be started by the MME (default SAE bearer) or by the PDN Gateway.

S5/S8 Interface (3GPP Candidate based on GTP)

ServingGateway

PDNGateway

PDNSGi

S5/S8 3GPP

User PDUsUser PDUs

GTP-UGTP-U

UDPUDP

IPIP

L1/L2L1/L2

GTP-CGTP-C

Control Plane

User Plane

TS 29.274 TS 29.281

S5/S8 (3GPP candidate) Interface between Serving GW and PDN GW S5: If Serving GW and PDN GW belong to the same network (non-roaming case) S8:If this is not the case (roaming case) S8 = S5 + inter-operator security functions Mainly used to transfer user packet data between PDN GW and Serving GW Signaling on S5/S8 is used to setup the associated bearer resources If S5/S8 implemented by GTP protocol

S5/S8 Interface (IETF Candidate based on PMIPv6)

ServingGateway

PDNGateway

PDNSGi

S5/S8 IETF

Control Plane

User Plane

User PDUsUser PDUs

MIPv6 Tunneling

Layer (GRE)

MIPv6 Tunneling

Layer (GRE)

IPv4/IPv6IPv4/IPv6

L1/L2L1/L2

PMIPv6PMIPv6

IPv4/IPv6IPv4/IPv6

TS 29.275 TS 29.275

S5/S8 (IETF candidate) Interface between Serving GW and PDN GW S5: If Serving GW and PDN GW belong to the same network (non-roaming case) S8:If this is not the case (roaming case) S8 = S5 + inter-operator security functions Mainly used to transfer user packet data between PDN GW and Serving GW Signaling on S5/S8 is used to setup the associated bearer resources If S5/S8 implemented by using Mobile IPv6 with some IETF enhancements.

Gx and Gxc Interface

P-GW

IMS/PDN

PCRF

Gx (Control Plane)

SGi

Gx ApplicationGx Application

SCTPSCTP

IPIP

L1/L2L1/L2

DIAMETERDIAMETER

S-GW

Gxc (Control Plane)

Gx ApplicationGx Application

SCTPSCTP

IPIP

L1/L2L1/L2

DIAMETERDIAMETER

S5/S8

TS 29.212 TS 29.212

Gxc Interface between the S-GW and the PCRF

(Policy and Charging Rule Function) It is only needed in case the S5/S8 interface

is based on PMIP (IETF candidate) This will help S-GW to map data between IP

service flows in S5/S8 and GTP tunnels in the S1-U interface, controlled by PCRF

Gx (S7) Interface between the PDN GW and the

PCRF It allows: PCRF to setup of a SAE bearer with

appropriate QoSPDN GW to request for the QoS of an SAE

bearer to setup from PCRFto indicate EPC status changes to the PCRF to

apply a new policy rule.

PMIP

Rx and SGi InterfaceRx

(Control Plane)

PDNGateway

PDN

PCRF

RX ApplicationRX Application

SCTPSCTP

IPIP

L1/L2L1/L2

DIAMETERDIAMETER

SGi(User Plane)

ApplicationApplication

UDP or TCPUDP or TCP

IPv4/IPv6IPv4/IPv6

L1/L2L1/L2

TS 29.214

TS 29.061

Rx Interface between PCRF (Policy & Charging

Rules Function) and the external PDN network/operators IMS (in general, towards the Service Domain)

Standardized in 3GPP TS 29.214: “ Policy and Charging Control over the Rx reference point (release 8)”

SGi Interface used by the PDN GW to send and

receive data to and from the external data network or Service Platform

It is either IPv4 or IPv6 based This interface corresponds to the Gi

interface in 2G/3G networks Standardized in 3GPP TS 29.061:

“Interworking between the Public Land Mobile Network (PLMN) supporting packet based services and Packet Data Networks (PDN)

S9 Interface

SCTPSCTP

IPIP

L1/L2L1/L2

DIAMETERDIAMETER

S9 ApplicationS9 Application

hPCRF

S9(Control Plane)

vPCRF

TS 29.215

S9 Interfaces between the hPCRF and the vPCRF is used in roaming cases. It is used in the VPLMN for enforcement of dynamic control polices from

the hPLMN. It is standardized in 3GPP TS 29.215: “ Policy and Charging Control over

the S9 reference point (Release 8)”.

S3 and S4 InterfaceS4

(Control Plane + User Plane)

2G/3GSGSN

MMEServing

Gateway

S3(Control Plane)

UDPUDP

IPIP

L1/L2L1/L2

GTP-CGTP-C

UDPUDP

IPIP

L1/L2L1/L2

GTP-UGTP-U

User PDUsUser PDUsTS 29.274

TS 29.281GTP-CGTP-CTS 29.274

S3/S4 Interfaces between EPC and 2G/3G packet switched core network domain They would allow inter-system changes between EPS and 2G/3G The S3 is a pure signaling interface used to coordinate the inter-system change

between MME and SGSN The S4 contains user plane and control plane interface and it is located between SGSN

and Serving SAE GW. These 2 interfaces are based on the Gn interface between the SGSN and the GGSN. This would allow to either forward packet data from EUTRAN via Serving SAE GW to

SGSN (and then to GGSN) or from 2G/3G RAN to SGSN to Serving SAE GW to PDN GW.

S12 Interface

ServingGateway

UDPUDP

IPIP

L1/L2L1/L2

GTP-UGTP-U

User PDUsUser PDUs

RNC

S12(User Plane)

TS 29.281

S12 Interfaces between EPC and 3G Radio access network It would allow inter-system changes between LTE and 3G The S12 is the user plane interface used for tunneling user data directly

between the Serving GW and the RNC. This would allow to forward packet data from 3G RAN to Serving GW to PDN

GW. It is based on the Gn interface between the SGSN and the GGSN and

therefore uses the GTP-U protocol.

Summary Control Plane

Summary User Plane

Protocols Details

“Thank you”