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Speaker: Dr. Phone Lin, Professor

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Evolution for 3G

Long Term Evolution (LTE)

Architecture, Protocol Stack, and Functionality

Introduction to E-UTRAN

Protocol Stack, and Functionality

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International Telecommunication Union (ITU)

Identified the frequencies around 2GHz for

International Mobile Telephony 2000 (IMT 2000)

IMT 2000 spectrum allocation at 2GHz LTE, WCDMA

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Air Interface

UTRA-UTRAN Long Term Evolution (LTE) Study Item (TSG-RAN)

Network Architecture

System Architecture Evolution (SAE) Study Item (TSG-SA)

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Objective:

To develop a framework for the evolution of the 3GPP radio-access

technology towards a high-data-rate, low-latency and packet-

optimized radio-access technology

Metric Requirement

Peak data rate DL: 100Mbps (3 to 4 times to that of HSDPA)

UL: 50Mbps (2 to 3 times to that of HSUPA)

Mobility support Up to 500kmph but optimized for low speeds from 0 to 15kmph

Control plane latency

(Transition time to active state)

< 100ms (for idle to active)

User plane latency < 5ms

Control plane capacity > 200 users per cell

Coverage (Cell sizes) 5 100km with slight degradation after 30km

Spectrum flexibility 1.25, 2.5, 5, 10, 15, and 20MHz

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Architecture and Protocol Stack

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EUTRAN

Evolved

Packet

Core (EPC)

GERAN

SGSN

S1-MME

Iu

Gb

S3 S4

S5 Operator IP

Service

(IMS)

SGi

S6a

S7

S2bS2a

LTE-Uu

MME

Serving

Gateway

S1-U

S10

Rx+

Wm*

S6c

Wn*Wa*

WLAN

Access NW

PDNGateway

ePDG

S7b

PCRF

Non 3GPP

IP Access

S7a

3GPP AAA

Server

Wx*

HSS

UTRAN S12

S11E-NBX2

8

Evolved Packet System (EPS) Architecture

EPS consists of LTE (Long Term Evolution), which is dedicated to the

evolution of the radio interface, and SAE (System Architecture Evolution), which

focuses on Core Network architecture evolution.

LTE E-UTRAN

SAE EPC (Evolved Packet Core)

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Evolved Radio Access Network (eRAN)

Consists of the eNodeB (eNB)

Offers Radio Resource Control (RRC) functionality

Radio Resource Management, admission control, scheduling, ciphering/deciphering of userand control plane data, and compression/decompression in DL/UL user plane packet headers

Serving Gateway (SGW)

Routes and forwards user data packets

Acts as the mobility anchor for the user plane- During inter-eNB handovers

- Between LTE and other 3GPP technologies

Pages idle state UE when DL data arrives for the UE

Packet Data Network Gateway (PDN GW)

Provides connectivity to the UE to external packet data networks

A UE may have simultaneous connectivity with more than one PDN GW

Performs policy enforcement, packet filtering, and charge support

Acts as mobility anchor between 3GPP and no-3GPP technologies

Mobility Management Entity (MME)

Manages and stores UE contexts- UE/user identities, UE mobility state, user security parameters

Paging message distribution 9

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LTE-Uu

S1-MME

Reference point for the control plane protocol between E-

UTRAN and MME. It uses Stream Control TransmissionProtocol (SCTP) as the transport protocol

10

L1

UE

RLC

MAC

PDCP

RRC

NAS

L1

RLC

MAC

PDCP

L1

L2

IPSCTP

S1-AP

Relay

L1

SCTP

S1-AP

NAS

L2

IP

eNodB MMES1-MMELTE-Uu

RRC

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S11 (MME-SGW)

GPRS Tunnelling Protocol for the control plane (GTP-C)

Has the same protocol stack as

- S10 (MME-MME)- S5 or S8a (SGW-PGW)

- S4 (SGSN-SGW)

- S3 (SGSN-MME)

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L1

UDP

GTP-C

L2

IP

MME

L1

UDP

GTP-C

L2

IP

SGWS11

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UE - PGW user plane with E-UTRAN

UE - PGW user plane with 3G access via the S4 interface

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L1

UE

RLC

MAC

PDCP

Application

L1

RLC

MAC

L1

L2

UDP/IP

Relay

L1

GTP-U

L2

UDP/IP

eNodB PDN GWS1-ULTE-Uu

PDCP

IP

GTP-U

L1 L1

L2

UDP/IP

Relay

SGW

GTP-U GTP-U

L2

UDP/IP

IP

S5/S8a SGi

GSM RF

UE

PDCP

Application

GSM RF L1bis

L2

UDP/IP

Relay

L1

GTP-U

L2

UDP/IP

NodB PDN GWIuUu

PDCP

IP

GTP-U

L1 L1

L2

UDP/IP

Relay

SGW

GTP-U GTP-U

L2

UDP/IP

IP

S5/S8a SGi

MAC

RLC

MAC

RLC

GSM RF L1bis

L2

UDP/IP

Relay

SGSN

PDCP GTP-U

MAC

RLC

S4

L1 L1

L2

UDP/IP

Relay

GTP-U GTP-U

L2

UDP/IP

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Protocol Stack, Functionality

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internet

eNB

RB Control

Connection Mobility Cont.

eNB MeasurementConfiguration & Provision

Dynamic Resource

Allocation (Scheduler)

PDCP

PHY

MME

S-GW

S1

MAC

Inter Cell RRM

Radio Admission Control

RLC

E-UTRAN EPC

RRC

Mobility

Anchoring

EPS Bearer Control

Idle State Mobility

Handling

NAS Security

P-GW

UE IP address

allocation

Packet Filtering

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The S1 control plane interface(S1-MME) The SCTP layer provides the

guaranteed delivery of

application layer messages. The transport network layer is

built on IP transport, similarly tothe user plane but for thereliable transport of signalling

messages SCTP is added on topof IP.

The application layer signallingprotocol is referred to as S1-AP(S1 Application Protocol).

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SCTP

IP

Data link layer

Physical layer

S1-AP

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S1 User Interface

Provides non guaranteed

delivery of user plane PDUs

between the eNB and the S-GW.

The transport network layer

is built on IP transport and

GTP-U is used on top ofUDP/IP to carry the user

plane PDUs between the eNB

and the S-GW.

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GTP-U

UDP

IP

Data link layer

Physical layer

User plane

PDUs

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EPS Bearer Service Management function: Setup, modify, release.

Mobility Functions for UEs in EMM-CONNECTED: Intra-LTE Handover

Inter-3GPP-RAT Handover.S1 Paging function

NAS Signalling Transport function

S1-interface management functions

Error indication and ResetInitial Context Setup Function supports the establishment of the necessary overall initial

UE Context in the eNB to enable fast Idle-to-Activetransition.

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Architecture

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eNB

MME / S-GW MME / S-GW

eNB

eNB

S1

S1

S1

S1X2

X2X2

E-UTRAN

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The X2 control plane interface (X2-CP) The transport network layer is built on SCTP on

top of IP.

The application layer signalling protocol isreferred to as X2-AP (X2 Application Protocol).

Functions Intra LTE-Access-System Mobility Support for UE

in EMM-CONNECTED:

- Context transfer from source eNB to target eNB;

- Control of user plane tunnels between sourceeNB and target eNB;

- Handover cancellation.

Uplink Load Management; General X2 management and error handling

functions:

- Error indication.

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X2 user plane interface (X2-U)

The X2-U interface provides non

guaranteed delivery of user plane

PDUs between eNBs. The transport network layer is built

on IP transport and GTP-U is used

on top of UDP/IP to carry the user

plane PDUs.

The X2-U interface protocol stack is

identical to the S1-U protocol stack.

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The physical layer performs the following main functions: Error detection on transport channel;

Support for Hybrid ARQ;

Power weighting;

Physical channel modulation/demodulation & link adaptation; Frequency and time synchronization;

Physical layer mapping;

Support for handover

Support for multi-stream transmission and reception (MIMO)

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Downlink: OFDM/OFDMA

Uplink: SC-FDMA (Single Carrier-Frequency Division

Multiple Access)

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Layer 2 is split intothe followingsublayers:

Medium AccessControl (MAC)

Radio LinkControl (RLC)

Packet DataConvergenceProtocol (PDCP)

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The main service and functions include: Transfer of upper layer PDUs supporting Acknowledged

Mode (AM) or Unacknowledged Mode (UM);

- The UM mode is suitable for transport of Real Time (RT)services because such services are delay sensitive and

cannot wait for retransmissions.- The AM mode, on the other hand, is appropriate for non-RT

(NRT) services such as file downloads.

Transparent Mode (TM) data transfer;

- The TM mode is used when the PDU sizes are known a priori

such as for broadcasting system information. Error Correction through ARQ

- CRC check provided by the physical layer; no CRC needed atRLC level

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Segmentation according to the size of the TB:- only if an RLC SDU does not fit entirely into the TB

- then the RLC SDU is segmented into variable sized RLC PDUs,which do not include any padding;

Re-segmentation of PDUs that need to be retransmitted- if a retransmitted PDU does not fit entirely into the new TB

used for retransmission then the RLC PDU is re-segmented

Concatenation of SDUs for the same radio bearer;

In-sequence delivery of upper layer PDUs except at HO;

Duplicate Detection;

Protocol error detection and recovery;

SDU discard;

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A red dotted line indicates the occurrence of

segmentation

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RLC header

RLC PDU

n n+1 n+2 n+3RLC SDU

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Logical channels

(characterized by the

information that is transferred)

Control channels

(carry control plane info)

Traffic channels

(carry uer plane info)

Broadcast Control

Channel (BCCH)

(DL channel for

broadcasting system

control info)

Paging Control

Channel (PCCH)

(DL channel for

transfering paging)

Common Control

Channel (CCCH)

(UL channel for

transmitting control info

and used by UE without

RRC connection)

Multicast Control

Channel (MCCH)

(DL p2m channel for

transmitting MBMS

control info

Dedicated Control

Channel (DCCH)

(p2p channel bidirectional

channel for exchanging

control information and used

by Ues with RRC connection

Dedicated Traffic

Channel (DTCH)

(Bidirectional channel

dedicated to single UE)

Multicast Traffic

Channel (MTCH)

(DL p2m channel for

transmission of MBMS

data)

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The main services and functions include: Mapping between logical channels and transport channels;

Multiplexing/demultiplexing of RLC PDUs belonging to oneor different radio bearers into/from transport blocks (TB)

delivered to/from the physical layer on transport channels; Traffic volume measurement reporting;

Error correction through HARQ;

Priority handling between logical channels of one UE;

Priority handling between UEs by means of dynamicscheduling;

Transport format selection;

Padding.

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Transport channels

(characterized by how the data is

transferred over radio interface)

Downlink channels Uplink channels

Broadcast

Control (BCH)

(fixed transport

format)

Paging

Channel (PCH)

(required to be

broadcast)

Downlink SharedChannel (DL-SCH)

(HARQ, dynamic link

adaptation, support for UE

DRX, dynamic and semi-

static resource allocation)

MulticastChannel (MCH)

(support for SFN

combining and

semi-static resource

allocation)

Random Access

Channel (RACH)

(limited control

information, collision

risk)

Uplink Shared

Channel (UL-SCH)

(HARQ, dynamic link

adaptation, support for UE

DRX, dynamic and semi-

static resource allocation)

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Difference

No dedicated transport

channel- CTCH of UTRAN is not required

All data broadcast in on

MBMS and on MTCH

CCCH DCCH DTCH

UL-SCHRACH

Uplink

Logical channels

Uplink

Transport channels

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BCCHPCCH CCCH DCCH DTCH MCCH MTCH

BCHPCH DL-SCH MCH

Downlink

Logical channels

Downlink

Transport channels

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DL-SCH and UL-SCH time-frequency resources are dynamicallyshared between

users in both uplink and downlink

Downlink Scheduling Dynamically determine, in each 1 ms interval, which terminal(s)

that are supposed to receive DL-SCH transmission and on whatresources.

- Resource block is a unit spanning 180kHz in the frequency domain

Responsible for selecting- Transport-block size, Modulation scheme, and Antenna mapping

Channel-dependent scheduling Channel Quality Indicator (CQI)

All mobile terminals in the cell observe the same referencesignals transmitted by the eNodeB

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Uplink Scheduling ENodeB

- Assings the time-frequency resources to mobile terminal

- Controls the TF the mobile terminal shall use

- No outband control signaling

Mobile Terminal

- Selects from which radio bearer the data is taken Logical channel multiplexing

Estimating the uplink channel quality

require a sounding reference signal transmitted from eachmobile terminal for which the eNodeB wants to estimatethe uplink channel quality

- overhead.

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Transport Block (TB) In each Transmission Time Interval (TTI), at most one transport

block of a certain size is transmitted over the radio interface

Transport Format (TF)

specifies how the TB is to be transmitted over the radiointerface.

information about the transport-block size

modulation scheme

antenna mapping.

Rate control Transport-format selection.

- By varying the transport format, the MAC layer can thus realizedifferent data rates.

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Principles N-process Stop-And-Wait HARQ is used to transmit

and retransmit TB

Upon reception of a TB, the receiver makes an

attempt to decode the TB and informs the transmitterabout the outcome of the decoding operationthrough a single ACK/NAK bit

- indicating whether the decoding was successful or if aretransmission of the transport block is required.

Downlink: DL-SCH Asynchronous adaptive HARQ

- the retransmissions are scheduled similarly to theinitial transmissions.

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Uplink: UL-SCH Synchronous HARQ;

- the time instant for the retransmissions is fixed once theinitial transmission has been scheduled

Maximum number of retransmissions configured per UE

Combination with RLC ARQ Small round trip time and low overhead

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The main service and functions for User plane Header compression/decompression: ROHC Transmission and Retransmission of user data In-sequence delivery of upper layer PDU at HO for RLC AM

Duplicate detection of lower layer SDUs Ciphering of user plane data and control plane data Integrity protection of control plane data

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PDCP

SAE Bearers

ROHC ROHCIntegrity

Protection

Ciphering Ciphering Ciphering Ciphering

NAS Signalling

User Plane Control Plane

ROHC: Robust Header Compression

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for Downlink Data

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The main services and functions include: Broadcast of System Information related to the NAS

Broadcast of System Information related to the AS

Paging

Establishment, maintenance and release of an RRCconnection between the UE and the E-UTRAN

Security Function: key management

Establishment, maintenance and release of point to pointRadio bearers

Mobility functions Establishment, configuration, maintenance and release of

Radio Bearers for MBMS services

QoS management functions

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RRC_IDLE PLMN selection

UE specific DRX configured by NAS

Broadcast of system information

Paging

Cell re-selection mobility

The UE shall have been allocated an id which uniquely

identifies the UE in a tracking area No RRC context stored in the eNB

UE keeps its IP address in order to rapidly move toLTE_ACTIVE when necessary

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LTE_IDLE: RRC_IDLE State

mobile terminal sleeps most of the time in order to reducebattery consumption.

LTE_ACTIVE: Mobile terminal is active with transmitting and receiving

data

IP address and Cell Radio-Network Temporary Identifier

(C-RNTI) assignments RRC_CONNECTED state

IN_SYNC: uplink is synchronized

OUT_OF_SYNC: uplink is not synchronized

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LTE_DETACHED:

No RRC entity

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UE Inter AS

Anchor

HSSOld

MME/UPE

3. Send old registrationinformation

4. Send user information

11. Configure IPBearer QoS

12. Attach Accept

13. Attach Confirm

9. Selection of IntersystemMobility Anchor GW

MME/UPE

1. Network Discovery andAccess System Selection

5. Authentication

2. Attach Request

8. Confirm Registration

10. User Plane Route Configuration

7. Delete UE registration information

6. Register MME

Evolved

RAN

RRC IDLE

LTE

DEATTACH

RRC IDLELTE

DEATTACH

RRC

CONNECTED

RRC

CONNECTED

LTE

ACTIVE

LTE

DEATTACH

LTE ACTIVE

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Intra E-UTRAN

Mobility Management in ECM-IDLE

Mobility Management in ECM-CONNECTED

Example Intra-MME/Serving Gateway HO Procedure

- The HO procedure is performed without EPC

involvement, i.e. preparation messages are directly

exchanged between the eNBs.

- The release of the resources at the source side during

the HO completion phase is triggered by the eNB.

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Legend

packet data packet data

UL allocation

2. Measurement Reports

3. HO decision

4 . Handover Request

5. Admission Control

6. Handover Request Ack

7.RRC Conn. Reconf. incl.

mobilityControlinformation

DL allocation

Data Forwarding

11. RRC Conn. Reconf. Complete

17. UE Context Release

12. Path Switch Request

UE Source eNB Target eNB Serving Gateway

Detach from old cell

and

synchronize to new cell

Deliver buffered and in transitpackets to target eNB

Buffer packets fromSource eNB

9 . S yn ch ro nisation

10. UL a llocat ion + TA for UE

packet data

packet data

L3 signalling

L1/L2 signalling

User Data

1. Measurement Control

16.Path Switch Request Ack

18. ReleaseResources

HandoverCompletion

HandoverExecution

HandoverPreparation

MME

0. Area Restriction Provided

13. User Plane updaterequest

15.User Plane updateresponse

14. Switch DL path

SN Status Transfer8.

End Marker

End Marker

packet data

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0 The UE context within the source eNB contains information regarding roaming restrictions which whereprovided either at connection establishment or at the last TA update.

1 The source eNB configures the UE measurement procedures according to the area restriction information.

Measurements provided by the source eNB may assist the function controlling the UE's connection mobility.

2 UE is triggered to send MEASUREMENT REPORT by the rules set by i.e. system information, specification etc.

3 Source eNB makes decision based on MEASUREMENT REPORT and RRM information to hand off UE.

4 The source eNB issues a HANDOVER REQUEST message to the target eNB passing necessary information to

prepare the HO at the target side (UE X2 signalling context reference at source eNB, UE S1 EPC signalling contextreference, target cell ID, KeNB*, RRC context including the C-RNTI of the UE in the source eNB, AS-configuration,

E-RAB context and physical layer ID of the source cell + MAC for possible RLF recovery). UE X2 / UE S1 signalling

references enable the target eNB to address the source eNB and the EPC. The E-RAB context includes necessary

RNL and TNL addressing information, and QoS profiles of the E-RABs.

5 Admission Control may be performed by the target eNB dependent on the received E-RAB QoS information to

increase the likelihood of a successful HO, if the resources can be granted by target eNB. The target eNB

configures the required resources according to the received E-RAB QoS information and reserves a C-RNTI and

optionally a RACH preamble. The AS-configuration to be used in the target cell can either be specifiedindependently (i.e. an "establishment") or as a delta compared to the AS-configuration used in the source cell

(i.e. a "reconfiguration").

6 Target eNB prepares HO with L1/L2 and sends the HANDOVER REQUEST ACKNOWLEDGE to the source eNB.

The HANDOVER REQUEST ACKNOWLEDGE message includes a transparent container to be sent to the UE as an

RRC message to perform the handover. The container includes a new C-RNTI, target eNB security algorithm

identifiers for the selected security algorithms, may include a dedicated RACH preamble, and possibly some

other parameters i.e. access parameters, SIBs, etc. The HANDOVER REQUEST ACKNOWLEDGE message may also

include RNL/TNL information for the forwarding tunnels, if necessary. 47

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7 The target eNB generates the RRC message to perform the handover, i.eRRCConnectionReconfigurationmessage including the mobilityControlInformation, to be sent bythe source eNB towards the UE. The source eNB performs the necessary integrity protection andciphering of the message. The UE receives the RRCConnectionReconfigurationmessage withnecessary parameters (i.e. new C-RNTI, target eNB security algorithm identifiers, and optionallydedicated RACH preamble, target eNB SIBs, etc.) and is commanded by the source eNB toperform the HO. The UE does not need to delay the handover execution for delivering theHARQ/ARQ responses to source eNB.

8 The source eNB sends the SN STATUS TRANSFER message to the target eNB to convey the

uplink PDCP SN receiver status and the downlink PDCP SN transmitter status of E-RABs for whichPDCP status preservation applies (i.e. for RLC AM). The uplink PDCP SN receiver status includes atleast the PDCP SN of the first missing UL SDU and may include a bit map of the receive status ofthe out of sequence UL SDUs that the UE needs to retransmit in the target cell, if there are anysuch SDUs. The downlink PDCP SN transmitter status indicates the next PDCP SN that the targeteNB shall assign to new SDUs, not having a PDCP SN yet. The source eNB may omit sending thismessage if none of the E-RABs of the UE shall be treated with PDCP status preservation.

9 After receiving the RRCConnectionReconfigurationmessage including the

mobilityControlInformation , UE performs synchronisation to target eNB and accesses the targetcell via RACH, following a contention-free procedure if a dedicated RACH preamble was indicatedin the mobilityControlInformation, or following a contention-based procedure if no dedicatedpreamble was indicated. UE derives target eNB specific keys and configures the selected securityalgorithms to be used in the target cell.

10 The target eNB responds with UL allocation and timing advance.

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11 When the UE has successfully accessed the target cell, the UE sends theRRCConnectionReconfigurationCompletemessage (C-RNTI) to confirm the handover, along withan uplink Buffer Status Report, whenever possible, to the target eNB to indicate that thehandover procedure is completed for the UE. The target eNB verifies the C-RNTI sent in theRRCConnectionReconfigurationCompletemessage. The target eNB can now begin sending data tothe UE.

12 The target eNB sends a PATH SWITCH message to MME to inform that the UE has changedcell.

13 The MME sends an UPDATE USER PLANE REQUEST message to the Serving Gateway.

14 The Serving Gateway switches the downlink data path to the target side. The Serving gatewaysends one or more "end marker" packets on the old path to the source eNB and then can releaseany U-plane/TNL resources towards the source eNB.

15 Serving Gateway sends an UPDATE USER PLANE RESPONSE message to MME.

16 The MME confirms the PATH SWITCH message with the PATH SWITCH ACKNOWLEDGEmessage.

17 By sending UE CONTEXT RELEASE, the target eNB informs success of HO to source eNB and

triggers the release of resources by the source eNB. The target eNB sends this message after thePATH SWITCH ACKNOWLEDGE message is received from the MME.

18 Upon reception of the UE CONTEXT RELEASE message, the source eNB can release radio and C-plane related resources associated to the UE context. Any ongoing data forwarding maycontinue.

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Simultaneous, tightly integrated, and efficientlyprovisioning of unicast and MBMS services.

MBMS can be provided on a set of cells dedicated to

MBMS transmission and/or on a set of cells

supporting both unicast and MBMS transmissions

MBMS transmission from several eNBs may be

coordinated

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MBMS

GW

eNB

MCE|

|

|

M1

M3

M2

MBMS GW: MBMS Gateway

MCE: Multi-Cell/Multicast Coordination Entity

M1: user plane interface

M2: E-UTRAN internal control plane interface

M3: control plane interface between E-UTRAN and EPC

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Multi-cell/multicast Coordination Entity (MCE) Allocation of the radio resources used by all eNBs in the

MBSFN area for multi-cell MBMS transmissions usingMBSFN operation.

decides the further details of the radio configuration

- modulation and coding scheme. Is involved in MBMS Session Control Signalling.

E-MBMS Gateway (MBMS GW) sending/broadcasting of MBMS packets with the SYNC

protocol to each eNB transmitting the service. uses IP Multicast as the means of forwarding MBMS user

data to the eNB.

performs MBMS Session Control Signalling (Sessionstart/stop) towards the eUTRAN.

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MCH

MCH

MCH

or

DL-SCH

MCH

MCH

MCH

or

DL-SCH

single cell

transmission

on MCH or DL-SCH

from MBMS dedicated

cell

mutlicell transmission

on MCH

from MBMS dedicated cells

multicell transmission

on MCH

from mixed cells

single cell

transmission

on MCH or DL-SCH

from a mixed cell

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Radio Bearer Control (RBC) The establishment, maintenance and release of Radio

Bearers involve the configuration of radio resourcesassociated with them.

Considerations

- Overall resource situation in EUTRAN,- QoS requirements of in-progress sessions

- QoS requirement for the new service

Radio Admission Control (RAC)

Admit or reject the establishment requests for new radiobearers.

Ensure high radio resource utilization and at the sametime to ensure proper QoS for in-progress sessions

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Connection Mobility Control (CMC) Management of radio resources in connection with idle or

connected mode mobility.

In idle mode

- the cell reselection algorithms are controlled by setting ofparameters that define the best cell and/or determine whenthe UE should select a new cell.

- E-UTRAN broadcasts parameters that configure the UEmeasurement and reporting procedures.

In connected mode,- the mobility of radio connections has to be supported.

- Handover decisions may be based on UE and eNBmeasurements.

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Dynamic Resource Allocation (DRA) - Packet Scheduling (PS) Allocate and de-allocate resources to user and control plane packets.

Selection of radio bearers whose packets are to be scheduled andmanaging the necessary resources

- QoS requirements associated with the radio bearers,

- Channel quality information for UEs,

- Buffer status,

- Interference situation

Inter-cell Interference Coordination (ICIC) Manage radio resources such that inter-cell interference is kept under

control.

A multi-cell RRM function that needs to take into account informationfrom multiple cells.

- resource usage status

- traffic load situation

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Load Balancing (LB) Handle uneven distribution of the traffic load over

multiple cells.

Influence the load distribution in such a manner that radio

resources remain highly utilized Result in hand-over or cell reselection decisions

Inter-RAT Radio Resource Management

Management of radio resources in connection with inter-

RAT mobility, The handover decision may take into account the involved

RATs resource situation as well as UE capabilities andOperator policies.

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This version of the specification does not support X2 connectivity of HeNBs.

The S1 interface is defined as the interface:

Between the HeNB GW and the Core Network,

Between the HeNB and the HeNB GW,

Between the HeNB and the Core Network,

Between the eNB and the Core Network.

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The HeNB GW appears to the MME as an eNB. TheHeNB GW appears to the HeNB as an MME. The S1interface between the HeNB and the EPC is the samewhether the HeNB is connected to the EPC via a HeNBGW or not.

The HeNB GW shall connect to the EPC in a way thatinbound and outbound mobility to cells served by theHeNB GW shall not necessarily require inter MMEhandovers. One HeNB serves only one cell.

The functions supported by the HeNB shall be the sameas those supported by an eNB (with the possibleexception of NNSF) and the procedures run between aHeNB and the EPC shall be the same as those betweenan eNB and the EPC.

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[1] 3GPP. GPRS enhancements for E-UTRAN access. 3GPP TS 23.401 v8.0.0 2007-12[2] 3GPP. Architecture enhancements for non-3GPP accesses. 3GPP TS 23.402 v8.0.0

2007-12

[3] 3GPP. 3GPP SAE: Report on technical options and conclusions. 3GPP TR 23.882v1.4.2, 2006-10

[4] 3GPP. 3GPP SAE: CT WG1 aspects. 3GPP TR 24.801 v0.5.1, 2007-12

[5] 3GPP. E-UTRA and E-UTRAN; Radio interface protocol aspects. 3GPP TR 25.813v7.1.0, 2006-10

[6] 3GPP. Feasibility study for evolved UTRA and UTRAN. 3GPP TR 25.912 v7.1.0,2006-10

[7] 3GPP. Requirements for E-UTRA and E-UTRAN. 3GPP TR 25.913 v7.1.0, 2006-10

[8] 3GPP. 3GPP SAE: CT WG4 aspects. 3GPP TR 29.803 v0.5.0, 2007-11

[9] 3GPP. 3GPP SAE: CT WG3 aspects. 3GPP TR 29.804 v0.3.0, 2007-11

[10] 3GPP. E-UTRA and E-UTRAN; Overall description; 3GPP TS 36.300 v8.3.02007-12

[11] Hannes, E., Adners, F., Jonas, K., Michael, M., Stefan, P., Johan, T., and Mattias,W., Technical Solutions for the 3G Long Term Evolution, IEEE CommunicationMagazine, March 2006.