01_LTE Radio Access System Overview

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LTE Radio Access System Overview


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Content

LTE / EPS Architecture and Interfaces

EPS Mobility and Connection States

EPS Bearer Concept

E-UTRAN Functionalities

NSN LTE / EPC Solution


NSN Network Architecture Evolution - Summary

Node B RNC SGSN GGSN

Internet

3GPP Rel 6 / HSPA

Direct tunnel

3GPP Rel 7 / HSPA

Internet

Node B RNC

SGSN

GGSN

Direct tunnel

3GPP Rel 7 / Internet HSPA

Internet

Node B

SGSN

GGSN

Node B

(RNC Funct.)

Direct tunnel

3GPP Rel 8 / LTE

Internet

Evolved Node B

MME

SAE GW


LTE/EPS Network Architecture Subsystems

• LTE/EPS architecture is driven by the goal to optimize the system for packet data transfer.

• No circuit switched components

• New approach in the inter-connection between radio access network and core network (S1 interface)

•The EPS architecture is made up of an EPC

(Packet Core Network, also referred as SAE)

and an eUTRAN Radio Access Network (also

referred as LTE)

•The EPC provides access to external packet

IP networks and performs a number of CN

related functions (e.g. QoS, security, mobility

and terminal context management) for idle

(camped) and active terminals

•The eUTRAN performs all radio interface

related functions

IMS/PDN

EPC

eUTRAN

LTE-UE

EPS


LTE/EPS Network Elements Main references to architecture in 3GPP specs.:

TS23.401,TS23.402,TS36.300


TS 36.421

LTE Radio Interface and the X2 Interface

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 150 Mbps(DL), 50Mbps (UL)

• MIMO (Multiple Input Multiple Output) is a major component although optional.

X2

• Inter eNB interface

• Handover coordination without involving the EPC

• X2AP: special signaling protocol

• During HO, Source eNB can use the X2 interface to forward downlink packets still buffered or arriving from the serving gateway to the target eNB.

• This will avoid loss of a huge amount of packets during inter-eNB handover.

(E)-RRC User PDUs

PDCP

RLC

MAC

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

TS 36.300

eNB LTE-Uu

eNB

X2

User PDUs

GTP-U

UDP

IP

L1/L2

TS 36.424

X2-UP

(User Plane)

X2-CP

(Control Plane)

X2-AP

SCTP

IP

L1/L2 TS 36.421

TS 36.422

TS 36.423

TS 36.420 [X2 general aspects & principles)

NAS Protocols

Control Plane User Plane

TS 36.323

TS 36.322

TS 36.321

TS 36.331

TS 29.281

TS 24.301


S1-MME & S1-U Interfaces

S1-MME

• Control interface between eNB and MME

• MME and UE will exchange non-access stratum 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

• S1flex 1 eNB to connect to several MME

S1-U

• User plane interface between eNB and serving gateway.

• It is a pure user data interface (U=User plane).

• S1flex-U also supported: a single eNB can connect to several Serving GWs.

• Which Serving GW a user’s SAE bearer will have to use is signaled from the MME of this user.

MME

Serving

Gateway

S1-MME

(Control Plane)

S1-U

(User Plane)

NAS Protocols

S1-AP

SCTP

IP

L1/L2

User PDUs

GTP-U

UDP

IP

L1/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


LTE/EPS Mobility Areas

Two areas are defined for handling of mobility in LTE/EPS:

Tracking Area (TA)

• It is the successor of location and routing areas from 2G/3G.

• When a UE is attached to the network, the MME will know the UE’s position on tracking area level.

• In case the UE has to be paged, this will be done in the full tracking area.

• Tracking areas are identified by a Tracking Area Identity (TAI).

The Cell

• Smallest entity regarding mobility

• When the UE is in connected mode, the MME will know the UE´s position on cell level

• Cells are identified by the Cell Global Identification (CGI), at the system level, and by the Physical Cell Identification (PCI), at the physical layer


LTE Mobility & Connection States

• Deregistered

• No location information in MME, no IP address or Default Bearer

• Registered

• MME knows location at cell or tracking area level, Default Bearer and IP address allocated for UE.

1.- EPS* Mobility Management (EMM) states

• ECM Idle

• No NAS connection between UE and MME, mobility is based on tracking area and cell reselection, no E-RAB (S1 and Uu), but EPS Default Bearer is still allocated (S5 / S8).

• ECM Connected

• NAS connection established, E-RAB (S1 and Uu) is allocated, mobility based on handover a cell level.

2.- EPS* Connection Management (ECM) states


LTE/EPS Bearer: Identity & Architecture

cell

S1-U LTE-Uu S5/S8

PDN

SGi eNB Serving

Gateway PDN

Gateway

E-UTRAN EPC PDN

•An EPS bearer identity uniquely identifies an EPS bearer for one UE. The EPS Bearer Identity is

allocated by the MME.

•LTE/EPS Bearer spans the complete network, from UE over EUTRAN and EPC up to the connector of

the external PDN.

•The SAE bearer is associated with a quality of service (QoS) usually expressed by a label or QoS

Class Identifier (QCI)

LTE-UE

End-to-End Service

EPS Bearer External Bearer

Radio Bearer S1 Bearer S5/S8 Bearer


EPS Bearers Establishment can be triggered by….

cell

S1-U

UE

S5 PDN

SGi

eNB

Serving

Gateway PDN

Gateway

EPS Bearer External Bearer

MME:This happens typically during

the attach procedure of an UE.

Depending on the information coming

from HSS, the MME will set up an

initial bearer, also known as the

Default EPS bearer. This EPS bearer

provides the initial connectivity of the

UE with its external data network or

IMS platform. MME

S1-MME

S11

PDN Gateway: The external data network

can request the setup of an EPS bearer by

issuing this request via PCRF to the PDN

gateway. This request will include the quality

of service granted to the new bearer. Those

are referred as Dedicated EPS bearers.

UE: Note here the differences to GPRS in 2G/3G networks, where only MS/UE initiated PDP context setup is defined.

PCRF

Gx/S7

Rx

Further Reading in Note Page


The Default Bearer Concept

•Each UE that is attached to the LTE network has at least one bearer available, that is called the default bearer.

•Its goal is to provide continuous IP connectivity towards the EPC (“always-on” concept)

•From the QoS point of view, the default bearer is normally a quite basic bearer

•If an specific service requires more stringent QoS attributes, then a dedicated bearer should be established.

cell

S1-U

UE

S5 PDN

Sgi

eNB

Serving

Gateway

PDN

Gateway

Default EPS Bearer

MME

S1-MME

S11


EPS Bearer QoS Attributes

EPS Bearer QoS Parameters

(To be defined per Bearer)

Default Bearer/Dedicated Bearer

GBR/N-GBR

MBR

UL/DL-TFT

QCI

ARP

EPS Bearer QoS Parameters

(To be defined per User)

AMBR


QoS Class Identifier (QCI) Table in 3GPP

GBR 1

Guarantee Delay budget Loss rate Application QCI

GBR

100 ms 1e-2 VoIP

2

GBR

150 ms 1e-3 Video call

3

GBR

300 ms 1e-6 Streaming

4

Non-GBR 100 ms 1e-6 IMS signaling 5

Non-GBR 100 ms 1e-3 Interactive gaming 6

Non-GBR 300 ms 1e-6 TCP protocols : browsing, email, file download

7

Non-GBR 300 ms 1e-6 8

Non-GBR 300 ms 1e-6 9

Priority

2

4

5

1

6

7

8

9

50 ms 1e-3 Real time gaming 3


EMM & ECM States Transitions

EMM_Deregistered

ECM_Idle

Power On

EMM_Registered

ECM_Connected

Registration (Attach)

• Allocate C-RNTI, GUTI

• Allocate IP address

• Authentication

• Establish security context

• Release RRC connection

• Release C-RNTI

• Configure DRX for paging

EMM_Registered

ECM_Idle

Release due to

Inactivity

•Establish RRC Connection

•Allocate C-RNTI

New Traffic

TAU Deregistration (Detach)

Change PLMN

• Release C-RNTI, GUTI

• Release IP address

Timeout of Periodic TA

Update

• Release GUTI

• Release IP address


E-UTRAN Functionalities

Transfer of user data

Radio channel ciphering and deciphering

Integrity protection

Header compression

Mobility control functions:

Connection setup and release

Load Balancing

Distribution function for NAS messages

NAS node selection function

Synchronization

Radio access network sharing

Subscriber and equipment trace

RAN Information Management

3GPP TS 36.401

Evolved

Node B

(eNB) cell

LTE-Uu

LTE-UE

E-UTRAN consists of one

or more Evolved Node

Bs (eNB)

It replaces the old Node B /

RNC combination

from 3G.

It terminates the complete

radio interface including

physical layer.

It provides all radio

management functions


NSN LTE / EPC Portfolio

Flexi Multiradio BTS LTE

• Evolved Node B (eNB)

Flexi Network Server

• Mobility Management Entity (MME)

Flexi Network Gateway

• S-GW and P-GW


Flexi Multiradio BTS LTE A complete macro high power outdoor 1+1+1 @ 60 W Flexi Multiradio BTS consists of:

system module

3-sector RF module for 60 W per sector/cell

optional AC/DC and battery module

A complete macro high power outdoor 1+1+1 @ 60 W + 60 W Flexi Multiradio BTS consists of:

system module

two 3-sector RF modules for 60 W + 60 W per sector/cell

optional AC/DC and battery module

The Flexi Multiradio BTS provides very high radio downlink output power when using the Flexi 210W 3-sector Radio Module. In the 3-sector BTS, all RF functions are integrated to one single outdoor installable 3U high module. With two 3-sector RF Modules in 2TX MIMO configuration, TX power is 120W per sector/cell (60 W + 60 W).


Flexi Multiradio BTS LTE

Another option especially for feederless and distributed LTE BTS sites is the Flexi Multiradio Remote Radio Head (RRH) that can support one sector with the following integrated features:

two transceivers to support 2TX MIMO

30 W + 30 W output power at antenna connectors

two linear power amplifiers

two RF filters for TX/RX

2 way RX diversity

wide bandwidth support (up to 20 MHz depending on 3GPP band RF variant)

48 V DC input power supply

no fans

OBSAI optical interface to the BTS system module

antenna tilt support


Flexi Network Server

Flexi Network Server (Flexi NS) is a high transaction capacity product on top of Advanced TCA (ATCA). It is optimized for all-IP flat architecture, and is used for control plane-only mobility management entity (MME) functionality.

The Flexi NS is an essential part of the Nokia Siemens Networks LTE and EPS end-to-end offering. The MME has a similar role in LTE as 2G/3G SGSN has in 2G/3G networks.

The Flexi NS is designed to serve as a pure control plane element for all-IP flat networks. Therefore, R8 S4 3G SGSN is considered as a natural evolution step for Flexi NS, leveraging the all-IP, control plane only optimized design.

Flexi NS implements high transaction and connectivity capacity to accommodate the increased signaling load and higher service penetration in an operators’ subscriber base. The product footprint is small, so you can install up to three high capacity units in a standard 19” rack. Flexi NS is power efficient, offering reduction in energy consumption.

Innovative control plane-only architecture of Flexi NS allows implementing session redundancy within a single Flexi NS network element. In case of a failure of any single hardware unit, the subscriber session can be preserved.

Nokia Siemens Networks SGSN has demonstrated market leading reliability levels in live networks over a time period of several years. The same DMX software platform is applied also as a basis for the Flexi NS.


Flexi Network Gateway

The new Flexi NG product family targets current and future mobile networks as well as converged networks. It is targeted to support high-speed packet access (HSPA), evolved high-speed packet access (HSPA+), Internet high-speed packet access (I-HSPA) and Long Term Evolution (LTE) access networks. Different applications, such as gateway GPRS support node (GGSN) or Evolved Packet Core (EPC) gateway, can be installed on same platform.

Flexi NG provides high throughput and signaling capacity to accommodate the traffic growth in next generation networks. The key to Flexi NG performance is in the use of multi-core packet processor (MPP) technology in the control plane and in the user plane. MPPs are designed for fast networking applications and contain several hardware units that accelerate packet data processing. MPP technology is highly flexible and scalable, and enables faster development cycles.

Flexi NG is based on the Nokia Siemens Networks AdvancedTCA (ATCA) hardware platform and Nokia Siemens Networks FlexiPlatform operating software and middleware. FlexiPlatform is a robust, carrier grade Linux based platform, offering versatile services for operation and maintenance (O&M), networking and platform services using the latest technologies available.


NSN O&M Solution – NetAct & iOMS


LTE SON has key operational benefits

Self Quality

Capacity

Coverage

Healing • Error self-detection and

mitigation

• Reduced operator effort

• Faster maintenance

• Reduced outage time

Optimization • Error self-detection and

mitigation

• Reduced operator effort

• Faster maintenance

• Reduced outage time

Configuration • Simplified installation

procedures - less prone to errors

• Faster roll-out

• Fewer drive-tests

• More flexibility in logistics (no site specifics)

• Reduced site planning


Nokia Siemens Networks’ SON is built on our detailed understanding of how networks operate

• Network automation and optimization for various use cases

• Full end-to-end solution combining distributed and centralized SON

• Multi-technology, multi-vendor solution through open 3GPP interfaces

• Flexible system enabling control and stop points

Nokia Siemens Networks SON Suite

Cell outage detection and compensation

Automated neighbor relat.

Interference optimization

Load balancing

Power saving

Plug and Play

Mobility robustness

Drive test minimization

Self Healing / alarm management

LTE SON

2G/3G SON

Open northbound interfaces

SON

Packet

Core

Other vendor network


In all SON use cases the features reside in both element and OSS level

SON Data Multi-vendor Data Network Data CM, FM, PM

WCDMA/GSM LTE Vendor Y Vendor X

• NetAct

Configurator Monitor & Reporter

Optimizer SW Manager

SON Workflow Coordinator

Planning tools

Management Network Engineering

Planning tools Network Operations

… …

Centralized SON

Distributed SON


SON Suite Features

Self- healing

Self- optimization

Self- configuration

• SON Plug and Play

• Automated Neighbor Relations

Management


Management

• Power Saving

• Mobility Load Balancing

• Mobility Robustness Optimization

• Service Quality Optimization

• Minimization of Drive Tests

• Cell Outage Detection, Repair

and Compensation

• Automatic interface alarm

correlation

• SON Plug and Play


Management

LTE WCDMA & GSM


Management

• Power Saving

• Interference Optimization

• Load Balancing

• Alarm Triggered Log Correction

(WCDMA)

• Automatic OMS resiliency

(WCDMA)

• OMS Overload Control

(WCDMA)


See Notes

Documents

01_LTE Radio Access System Overview