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LTE eNB

System Description


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COPYRIGHT

This manual is proprietary to SAMSUNG Electronics Co., Ltd. and is protected by copyright.

No information contained herein may be copied, translated, transcribed or duplicated for any commercial

purposes or disclosed to the third party in any form without the prior written consent of SAMSUNG Electronics

Co., Ltd.

TRADEMARKS

Product names mentioned in this manual may be trademarks and/or registered trademarks of their respective

companies.

This manual should be read and used as a guideline for properly installing and operating the product.

Al l reasonable care has been made to ensure t hat th is document is accurate. If you have an y commen ts on

this manual, please contact our documentation centre at the following address:

Address: Document Center 3rd Floor Jeong-bo-tong-sin-dong. 129, Samsung-ro, Yeongtong-gu, Suwon-si,

Gyeonggi -do, Korea 443-742

Homepage: http://www.samsungdocs.com

©2012~2013 SAMSUNG Electronics Co., Ltd. All rights reserved.


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INTRODUCTION

© SAMSUNG Electronics Co., Ltd. page 3 of 91

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INTRODUCTION

Purpose

This description describes the characteristics, features and structure of the LTE eNB.

Document Content and Organization

This manual consists of five Chapters and a list of Abbreviations.

CHAPTER 1. Samsung LTE System Overview

Introduction to Samsung LTE System

Samsung LTE Network Configuration

CHAPTER 2. LTE eNB Overview

Introduction to System

Main Functions

Specifications

Intersystem Interface

CHAPTER 3. LTE eNB Structure

Hardware Structure

Software Structure

CHAPTER 4. Message Flow

Call Processing Message Flow

Data Traffic Flow

Network Sync Flow

Alarm Signal Flow

Loading Flow

Operation and Maintenance Message Flow


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CHAPTER 5. Supplementary Functi ons and Tools

Web-EMT

CLI

RET

ABBREVIATIONS

Definitions of the abbreviations used in this manual.

Conventions

The following types of paragraphs contain special information that must be carefully readand thoroughly understood. Such information may or may not be enclosed in a rectangular

box, separating it from the main text, but is always preceded by an icon and/or a bold title.

NOTE

Indicates additional information as a reference.

WEEE Symbol Information

This marking on the product, accessories or literature indicates that the product and

its electronic accessories should not be disposed of with other household waste at the

end of their working life. To prevent possible harm to the environment or human health

from uncontrolled waste disposal, please separate these items from other types of

waste and recycle them responsibly to promote the sustainable reuse of material

resources.

For more information on safe disposal and recycling, visit our website www.samsung.com/in or

contact our Helpline numbers-18002668282, 180030008282.


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Revision History

VERSION DATE OF ISSUE REMARKS

5.0 06. 2013. - Deleted the Smart Scheduler server related information

(Chapter 5)

- ‘Smart Scheduler server system description’ was

configured independantly.)

4.0 03. 2013. - Smart Scheduler server details were added. (1.2, 2.4,

Chapter 5)

- eMBMS details were added. (1.2, 2.1, 2.2.1, 2.2.3)

- Following terms were changed: UADU CDU, L8HU

RRU, LSM-R LSM, LSM-C CSM

- Supporting capacity was changed (1 Carrier/3 Sector

1 Carrier/9 Sector, 3 L9CA boards)

- Other errors were corrected.

3.0 12. 2012. - System configuration was changed. (L9CA)

- ‘2.1’ was changed.

- ‘2.3’ was changed.

- ‘3.1.1’ was changed.

- ‘3.1.3’ was changed.

- ‘Figure 4.14’ was changed.

2.0 08. 2012. ‘2.3’ was changed.

1.0 08. 2012. First Version


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TABLE OF CONTENTS


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TABLE OF CONTENTS

INTRODUCTION 3

Purpose ................................................................................................................................................. 3

Document Content and Organization.................................................................................................... 3

Conventions ........................................................................................................................................... 4

WEEE Symbol Information .................................................................................................................... 4

Revision History ..................................................................................................................................... 5

CHAPTER 1. Samsung LTE System Overview 10

1.1 Introduct ion to Samsung LTE System ................................................................................... 10

1.2 Samsung LTE Network Conf iguration ................................................................................... 13

CHAPTER 2. LTE eNB Overview 16

2.1

Introduction to System ........................................................................................................... 16

2.2 Main Functions ........................................................................................................................ 18

2.2.1 Physical Layer Processing ...................................................................................................... 18

2.2.2 Call Processing Function ........................................................................................................ 22

2.2.3 IP Processing .......................................................................................................................... 24

2.2.4 SON Function .......................................................................................................................... 25

2.2.5 Easy Operation and Maintenance .......................................................................................... 26

2.3 Specifications .......................................................................................................................... 29

2.4 Intersystem Interface .............................................................................................................. 31

2.4.1 Interface Structure ................................................................................................................... 31

2.4.2 Protocol Stack.......................................................................................................................... 32

2.4.3 Physical Interface Operation ................................................................................................... 36

CHAPTER 3. System Structure 37

3.1 Hardware Structure ................................................................................................................. 37

3.1.1 CDU ......................................................................................................................................... 38

3.1.2 RRU ......................................................................................................................................... 41

3.1.3

Power Supply .......................................................................................................................... 42

3.1.4 Cooling Structure ..................................................................................................................... 43


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3.1.5 External Interface .................................................................................................................... 44

3.2 Software Structure .................................................................................................................. 46

3.2.1

Basic Software Structure ......................................................................................................... 46

3.2.2 CPS Block ............................................................................................................................... 49

3.2.3 OAM Blocks ............................................................................................................................. 52

CHAPTER 4. Message Flow 56

4.1 Call Processing Message Flow .............................................................................................. 56

4.2 Data Traffic Flow ..................................................................................................................... 76

4.3 Network Sync Flow ................................................................................................................. 77

4.4

Alarm Signal Flow ....................................................... ............................................................ 78

4.5 Loading Flow ........................................................................................................................... 79

4.6 Operation and Maintenance Message Flow .......................................................................... 80

CHAPTER 5. Supplementary Functions and Tools 81

5.1 Web-EMT ................................................................................................................................. 81

5.2 CLI ............................................................................................................................................ 82

5.3 RET .......................................................................................................................................... 83

ABBREVIATION 84


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LIST OF FIGURES

Figure 1. Functional Distinctions of E-UTRAN and EPC ................................................. ........... 11

Figure 2. Samsung LTE System Architecture ............................................................................. 13

Figure 3. Inter-System Interface Structure ........................................................... ....................... 31

Figure 4. Protocol Stack between UE and eNB .................................................................... ...... 32

Figure 5. Protocol Stack between eNB and S-GW User Plane ................................................... 33

Figure 6. Protocol Stack between eNB and MME Control Plane ................................................ 33

Figure 7. Inter-eNB User Plane Protocol Stack........................................................ ................... 34

Figure 8. Inter-eNB Control Plane Protocol Stack .................................................... ................... 34

Figure 9. Interface Protocol Stack between eNB and LSM ......................................................... 35

Figure 10. Protocol Stack between eNB and Smart Scheduler Server ....................................... 35

Figure 11. Protocol Stack between Smart Scheduler Server and LSM ....................................... 36

Figure 12. Internal Configuration of eNB .................................................................................... 37

Figure 13. CDU Configuration .................... ........................................................... ..................... 38

Figure 14. RRU Configuration .................... ........................................................... ..................... 41

Figure 15. Power Supply Configuration ...................................................................................... 42

Figure 16. Cooling Structure of CDU ......................................................................................... . 43

Figure 17. CDU External Interface ...................................................... ........................................ 44

Figure 18. RRU’s External Interface ........................................................ ................................... 45

Figure 19. eNB Software Structure .......................................................... ................................... 46

Figure 20. CPS Structure ...................................................... ...................................................... 49

Figure 21. OAM Structure ..................................................... ...................................................... 52

Figure 22. Attach Process........................................................................................................... 57

Figure 23. Service Request Process by UE ................................... ............................................ 59

Figure 24. Service Request Process by Network ........................................................... ............ 61

Figure 25. Detach Process by UE .................................................................. ............................ 62

Figure 26. Detach Process by MME ................................................................... ........................ 63

Figure 27. X2-based Handover Procedure ................................................................................. 64

Figure 28. S1-based Handover Procedure ................................................................................. 66

Figure 29. E-UTRAN to UTRAN PS Handover ....................................................... .................... 69

Figure 30. UTRAN to E-UTRAN PS Handover ....................................................... .................... 71

Figure 31. CS Fallback to UTRAN Procedure (UE in Active mode, No PS HO support) ............ 73

Figure 32. CS Fallback to GERAN Procedure (UE in Active mode, No PS HO support) ............ 74

Figure 33. Data Traffic Flow ........................................................... ............................................. 76

Figure 34. Network Synchronization Flow ................................................................. ................. 77

Figure 35. Alarm flow ....................................................... ........................................................... 78

Figure 36. Loading Signal Flow ....................................................................... ........................... 79

Figure 37. Operation and Maintenance Signal Flow .......................................................... ......... 80


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Figure 38. Web-EMT Interface ............................................................ ....................................... 81

Figure 39. RET Interface ................................................. ........................................................... 83


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CHAPTER 1. Samsung LTE System Overvi ew


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CHAPTER 1. Samsung LTE SystemOverview

1.1 Introduction to Samsung LTE SystemThe Samsung LTE system supports 3GPP LTE (hereinafter, LTE) based services.

LTE is a next generation wireless network system which solves the disadvantages of

existing 3GPP mobile systems allows high-speed data service at low cost regardless of time

and place.

The Samsung LTE system supports the Orthogonal Frequency Division Multiple Access

(OFDMA) for downlink, the Single Carrier (SC) Frequency Division Multiple Access

(FDMA) for downlink, and scalable bandwidths for various spectrum allocation and

provides high-speed data service. It also provides high-performance hardware for improved

system performance and capacity and supports various functions and services.

Compliance Standards

The Samsung LTE system is based on the Rel-8 and Rel-9 standards of the LTE

3rd Generation Partnership Project (3GPP).

The Samsung LTE system consists of the evolved UTRAN Node B (eNB), Evolved Packet

Core (EPC) and LTE System Manager (LSM).

The eNB exists between the EPC and the User Equipment (UE). It establishes wireless

connections with the UE and processes packet calls according to the LTE air interface

standard. The eNB manages the UE in connected mode at the Access Stratum (AS) level.

The EPC is the system located between the eNB and Packet Data Network to perform

various control functions. The EPC consists of the Mobility Management Entity (MME),

Serving Gateway (S-GW) and PDN Gateway (P-GW). The MME manages the UE in idle

mode at the Non-Access Stratum (NAS) level; and the S-GW and the P-GW manage user

data at the NAS level and interworks with other networks.

The LSM provides the man-machine interface; manages the software, configuration,

performance and failures; and acts as a Self Organizing Network (SON) server.


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The figure below shows the functional distinctions between the eNB of E-UTRAN, MME,

S-GW, and P-GW according to the 3GPP standard. The eNB has a layer structure and the

EPC has no layer.

Figure 1. Functional Distinct ions of E-UTRAN and EPC

eNB

An eNB is a logical network component of the Evolved UTRAN (E-UTRAN) which is on

the access side in the LTE system.

eNBs can be interconnected with each other by means of the X2 interface. The eNBs are

connected by means of the S1 interface to the Evolved Packet Core (EPC).

The wireless protocol layer of the eNB is divided into layer 2 and layer 3. Layer 2 is

subdivided into the Media Access Control (MAC) layer, the Radio Link Control (RLC)

layer, and the PDCP layer, each of which performs independent functions. Layer3 has the

Radio Resource Control (RRC) layer.

The MAC layer distributes air resources to each bearer according to its priority, and performs the

multiplexing function and the HARQ function for the data received from the multiple upper

logical channels.

The RLC layer performs the following functions.

Segments and reassembles the data received from the PDCP layer in accordance with

the size specified by the MAC layer

Requests retransmission to recover if data transmission fails in the lower layer (ARQ) Reorders the data recovered by performing HARQ in the MAC layer (re-ordering)

S1

MME

NAS Security

Idle State Mobility

Handling

EPS Bearer Control

S-GW

Mobility Anchoring

P-GW

Packet Filtering

UE IP address allocation

EPC

eNB

Inter Cell RRM

RB Control

Connection Mobility Cont.

Radio Admission Control

eNB MeasurementConfiguration & Provision

Dynamic Resource Allocation(Scheduler)

RRC

PDCP

RLC

MAC

PHY

E-UTRAN


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The PDCP layer performs the following functions.

Header compression and decompression

Encrypts/decrypts user plane and control plane data Protects and verifies the integrity of control plane data

Transmits data including sequence number related function

Removes data and redundant data based on a timer

The RRC layer performs mobility management within the wireless access network,

maintaining and control of the Radio Bearer (RB), RRC connection management, and

system information transmission, etc.

MMEThe MME interworks with the E-UTRAN (eNB) to process the Stream Control

Transmission Protocol (SCTP)-based S1 Application Protocol (S1-AP) signaling messages

for controlling call connections between the MME and the eNB and to process the SCTP-

based NAS signaling messages for controlling mobility connection and call connection

between the UE and the EPC.

The MME is responsible for collecting/modifying the user information and authenticating the

user by interworking with the HSS. It is also responsible for requesting the allocation/

release/change of the bearer path for data routing and retransmission with the GTP-C

protocol by interworking with S-GW.

The MME interworks with the 2G and 3G systems, the SGSN and the MSC for providingmobility and Handover (HO), Circuit Service (CS) Fallback and Short Message Service

(SMS).

The MME is responsible for inter-eNB mobility, idle mode UE reachability, Tracking Area

(TA) list management, choosing P-GW/S-GW, authentication, and bearer management.

The MME supports mobility during inter-eNB handover and the inter-MME handover.

It also supports the SGSN selection function upon handover to a 2G or 3G 3GPP network.

S-GW

The S-GW acts as the mobility anchor during inter-eNB handover and inter-3GPP handover,

and routes and forwards user data packets. The S-GW allows the operator to apply

application-specific charging policies to UE, PDN or QCI and manages the packet

transmission layers for uplink/downlink data.

The S-GW also supports GPRS Tunneling Protocol (GTP) and Proxy Mobile IP (PMIP) by

interworking with the MME, P-GW, and SGSN.

PDN Gateway (P-GW)

The P-GW is responsible for charging and bearer policy according to the policy and

manages charging and transmission rate according to the service level by interworking with

the PCRF. The P-GW also performs packet filtering for each user, IP address allocation foreach UE, and downlink data packet transmission layer management.


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1.2 Samsung LTE Network Configuration

A Samsung LTE system consists of the eNB, LSM, and EPC. The Samsung LTE system

comprising multiple eNBs and EPCs (MME, S-GW/P-GW) is a subnet of the PDN, which

allows the User Equipment (UE) to access external networks. In addition, the Samsung

LTE system provides the LSM and self-optimization function for operation and

maintenance of eNBs.

The following shows the Samsung LTE system architecture.

Figure 2. Samsung LTE System Architecture

eNB

The eNB is located between the UE and EPC. It processes packet calls by connecting to the

UE wirelessly according to the LTE air standard. The eNB is responsible for transmission

and receipt of wireless signals, modulation and demodulation of packet traffic signals,

packet scheduling for efficient utilization of wireless resources, Hybrid Automatic Repeat

Request (HARQ)/ARQ processing, Packet Data Convergence Protocol (PDCP) for packet

header compression, and wireless resources control.

In addition, the eNB performs handover by interworking with the EPC.

UE UE

OFCS

HSS

Uu

S1-U S1-MME

EMS

CSM

eNB

EMS

LSM

OCS

EPC

S5/S8

Gx

S-GW

Sp

TL1

MME

P-GW

Gy

S11 S6a

Gz

Gz

S10

PDN

X2-C

X2-U

SNMP/FTP/UDP

SmartScheduler Server

SNMP/FTP/UDP

RMI

MSS

SC-1

eNB

PCRF


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EPC

The EPC is a system located between the eNB and PDN. The subcomponents of the EPC

are the MME, S-GW and P-GW. MME: Processes control messages using the NAS signaling protocol with the eNB and

performs control plane functions such as UE mobility management, tracking area list

management, and bearer and session management.

S-GW: Acts as the anchor for the user plane between the 2G/3G access system and the

LTE system, and manages and changes the packet transmission layer for downlink/

uplink data.

P-GW: Allocates an IP address to the UE, acts as the anchor for mobility between the LTE

and non-3GPP access systems, and manages/changes charging and the transmission rate

according to the service level.

LTE System Manager (LSM)

The LSM provides the user interface for the operator to operate and maintain the eNB.

The LSM is responsible for software management, configuration management,

performance management and fault management, and acts as a Self-Organizing Network

(SON) server.

Core System Manager (CSM)

The CSM provides the user interface for the operator to operate and maintain the MME,

S-GW, and P-GW.

Master SON Server (MSS)

The MSS interoperates with the local SON server as its higher node, making optimized

interoperation possible for the multi-LSM. The MSS can work with Operating Support

System (OSS) of the service provider who can decide whether to link them.

Home Subscriber Server (HSS)

The HSS is a database management system that stores and manages the parameters and

location information for all registered mobile subscribers. The HSS manages key data such

as the mobile subscriber’s access capability, basic services and supplementary services, and

provides a routing function to the subscribed receivers.

Policy and Charging Rule Funct ion (PCRF)

The PCRF server creates policy rules to dynamically apply the QoS and charging policies

differentiated by service flow, or creates the policy rules that can be applied commonly to

multiple service flows. The P-GW includes the Policy and Charging Enforcement Function

(PCEF), which allows application of policy rules received from the PCRF to each service

flow.


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Online Charging System (OCS)

The OCS collects online charging information by interfacing with S-GW and P-GW.

When a subscriber for whom online charging information is required makes a call, the P-GW

transmits and receives the subscriber’s charging information by interworking with the OCS.

Offline Charging System (OFCS)

The OFCS collects offline charging information by interfacing with S-GW and P-GW.

The OFCS uses the GTP’ (Gz) or Diameter (Rf) interface to interface with the S-GW and

P-GW.

Smart Scheduler Server

The Smart Scheduler server is a system to minimize cell interference through the

cooperation of eNBs. The Smart Scheduler module in the Smart Scheduler server provides

the centralized wireless resource management function for multiple eNBs.

The Smart Scheduler server efficiently compensates the cell interference caused by cell

split to improve the cell edge throughput per unit area.

Smart Scheduler Server

For the further information on the Smart Scheduler Server, please refer the

system description of the Smart scheduler server in separate volume.


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2.1 Introduction to System

An LTE eNB, eNB is located between the UE and the EPC. It provides mobile

communications services to subscribers according to the LTE air interface standard.The eNB transmits/receives radio signals to/from the UE and processes the modulation and

demodulation of packet traffic signals. The eNB is also responsible for packet scheduling

and radio bandwidth allocation and performs handover via interface with the EPC.

The eNB consists of the Cabinet DU (CDU), a Digital Unit (DU), and the Remote Radio

Unit (RRU), a Radio Unit (RU).

The CDU is a digital unit (19-inch shelf) and can be mounted into an indoor or outdoor 19-

inch commercial rack.

The RRU is an RF integration module consisting of a transceiver, power amplifier, and

filter. It transmits and receives traffic, clock information, and alarm/control messages to

and from the CDU. The RRU employs 4Tx/4Rx configuration supporting optic CPRI and

can be installed on an outdoor wall or pole.

The main features of eNB are as follows:

High Compatibility and Interoperability

Because the eNB complies with the specifications released based on the 3GPP standard, ithas high compatibility and Interoperability.

High-Performance Modular Structure

The eNB has high-performance with the use of high-performance processors.

It is easy to upgrade hardware and software because of its modular structure.

Support for Advanced RF and Antenna Solutions

The eNB adopts the power amplifier to support the wideband operation bandwidth and

supports the Multiple Input Multiple Output (MIMO).


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6Rx Multi Antenna Support

The eNB can receive up to 6Rx signals in its own sector as well as from the antenna in

repeater mode.

Separation of CDU and RRU

The eNB consists of the CDU and RRU separately for easy installation and flexible

network configuration. For connection between the CDU and RRU, data traffic signals and

OAM information are transmitted/received through the Digital I/Q and C&M interface

based on the Common Public Radio Interface (CPRI). Physically, optic cables are used.

The CDU and RRU are supplied DC -48 V power from a rectifier respectively.

Flexible Network Configuration

The RRU is not a standalone device; it operates interfacing with the CDU.

The RRU is highly flexible in its installation, and helps with setting up a network in a

variety of configurations depending on the location and operation method.

Easy Installation

The optic interface component that interfaces with the CDU and the RF signal

processing component is integrated into the RRU, which becomes a very small and

very light single unit. The RRU can be installed on a wall, pole, or floor.

In addition, as the distance between the RRU and antenna is minimized, the loss of RF

signals due to the antenna feeder line can be reduced so that the line can provide more

enhanced RF receiving performance than the existing rack-type eNB.

Natural CoolingThe RRU is designed to discharge heat effectively through natural cooling without an

additional cooling device. No additional maintenance cost is needed for cooling the RRU.

Support for Loopback Test between CDU and RRU

The eNB provides the loopback test function to check whether communication is

normal on a Digital I/Q and C & M interface between the CDU and RRU.

Remote Firmware Downloading

By replacing its firmware, the RRU can be upgraded in terms of service and performance.

The operator can download firmware to the RRU remotely using a simple command from

the LSM without visiting the station. As a result, the number of visits is minimized,

leading to reduced maintenance costs and system operation with ease.

Monitoring Port

The operator can monitor the information for the RRU using its debug port.

MBSFN Transmission Support

Since eNB supports MBSFN transmission, same data stream of the time synchronized cells

are transmitted to the same subcarriers at the same time so that the UE can recognize the

data transmitted from multiple cells as the data transmitted from a single cell and the

interference among the cells can be reduced.

The sub-frame of the data stream always uses the extended Cyclic Prefix (CP) to prevent

interference to the delay spread.


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2.2 Main Functions

The main functions of the LTE eNB are as follows:

Physical Layer Processing

Call Processing Function

IP Processing

SON Function

Interfacing with Auxiliary Devices

Easy Operation and Maintenance

Avai labil ity of System Features and Functions

For availability and provision schedule of the features and functions described in

the system manual, please refer to separate documentations.

2.2.1 Physical Layer Processing

The eNB transmits/receives data through the radio channel between the EPC and UE.

To do so, the eNB provides the following functions.

OFDMA/SC-FDMA Scheme

Downlink Reference Signal Creation and Transmission

Downlink Synchronization Signal Creation and Transmission

MBSFN Reference Signal Creation and Transmission

Channel Encoding/Decoding

Modulation/Demodulation

Resource Allocation and Scheduling

Link Adaptation

HARQ

Power Control ICIC

MIMO

OFDMA/SC-FDMA Scheme

The eNB performs the downlink OFDMA/uplink SC-FDMA channel processing that

supports the LTE standard physical layer. The downlink OFDMA scheme allows the

system to transmit data to multiple users simultaneously using the subcarrier allocated to

each user. Depending on the channel status and the transmission rate requested by the user,

the downlink OFDM can allocate one or more subcarriers to a specific subscriber to

transmit data.


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In addition, when all sub-carriers are divided for multiple users, the eNB can select and

assign to each subscriber a sub-carrier with the most appropriate features using the

OFDMA scheme, thus to distribute resources efficiently and increase data throughput.

For uplink SC-FDMA, which is similar to OFDMA modulation and demodulation, a

Discrete Fourier Transform (DFT) is applied to each subscriber in the modulation at the

transmitting side. An inverse Discrete Fourier Transform (IDFT) is applied for minimizing

the Peak to Average Power Ratio (PAPR) at the transmitting side, which allows continuous

allocation of frequency resources available for individual subscribers. As a result, the eNB

can reduce the power consumption of the UE.

Downlink Reference Signal Creation and Transmission

The UE must estimate the downlink channel to perform the coherent demodulation on the

physical channel in the LTE system. The LTE uses the OFDM/OFDMA-based methods fortransmitting and therefore the channel can be estimated by inserting the reference symbols

from the receiving terminal to the grid of each time and frequency. These reference

symbols are called downlink reference signals, and there are 2 types of reference signal

defined in the LTE downlink.

Cell-specific reference signal: The cell specific reference signal is transmitted to every

subframe across the entire bandwidth of the downlink cell. It is mainly used for

channel estimation, MIMO rank calculation, MIMO precoding matrix selection and

signal strength measurement for handover.

UE-specific reference signal: The UE-specific reference signal is used for estimating

channel for coherent demodulation of DL-SCH transmission where the beamformingmethod is used. ‘UE-specific’ means that the reference signal is generally used for

channel estimation of a specified UE only. Therefore, the UE-specific reference signal

is used in the resource block allocated for DL-SCH only, which is transmitted to the

specified UE.

Downlink Synchronization Signal Creation and Transmission

The synchronization signal is used for the initial synchronization when the UE starts to

communicate with the eNB. There are two types of synchronization signals: Primary

Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS).

The UE can obtain the cell identity through the synchronization signal. It can obtain other

information about the cell through the broadcast channel. Since synchronization signals and

broadcast channels are transmitted in the 1.08 MHz range, which is right in the middle of

the cell’s channel bandwidth, the UE can obtain the basic cell information such as cell ID

regardless of the transmission bandwidth of the eNB.


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MBSFN Reference Signal Creation and Transmission

In the enhanced/evolved Multimedia Broadcast Multicast Services (eMBMS) system, the

MBSFN reference signal of the MBSFN sub-frame in addition to the cell-specific referencesignal and UE-specific reference signal used by the existing unicast are used to estimate the

downlink physical channel by inserting the reference symbols that can be recognized by the

reception layerMBSFN reference signal.

The MBSFN reference signal is provided in 7.5 subcarrier spacing in the case of extended

CP to the antenna port number 4.

Channel Encoding/Decoding

The eNB is responsible for channel encoding/decoding to correct the channel errors that

occurred on a wireless channel. In LTE, the turbo coding and the 1/3 tail-biting

convolutional coding are used. Turbo coding is mainly used for transmission of large data packets on downlink and uplink, while convolutional coding is used for control information

transmission and broadcast channel for downlink and uplink.

Modulation/Demodulation

For the data received over the downlink from the upper layer, the eNB processes it through

the baseband of the physical layer and then transmits it via a wireless channel. At this time,

to transmit a baseband signal as far as it can go via the wireless channel, the system

modulates and transmits it on a specific high frequency bandwidth.

For the data received over the uplink from the UE through a wireless channel, the eNB

demodulates and changes it to the baseband signal to perform decoding.

Resource Allocation and Scheduling

To support multiple accesses, the eNB uses OFDMA for downlink and SC-FDMA for

uplink. By allocating the 2-dimensional resources of time and frequency to multiple UEs

without overlay, both methods enable the eNB to communicate with multiple UEs

simultaneously.

When the eNB operates in MU-MIMO mode, the same resource also may be used for

multiple UEs simultaneously. Such allocation of cell resources to multiple UEs is called

scheduling, and each cell has its own scheduler for this function.

The LTE scheduler of the eNB allocates resources to maximize the overall throughput of

the cell by considering the channel environment of each UE, the data transmission volume

required, and other QoS elements. In addition, to reduce interferences with other cells, the

eNB can share information with the schedulers of other cells over the X2 interface.


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Link Adaptation

The wireless channel environment can become faster or slower, better or worse depending

on various factors. The system is capable of increasing the transmission rate or maximizingthe total cell throughput in response to the changes in the channel environment, and this is

called link adaptation.

In particular, the Modulation and Coding Scheme (MCS) is used for changing the

modulation method and channel coding rate according to the channel status. If the channel

environment is good, the MCS increases the number of transmission bits per symbol using

a high-order modulation, such as 64QAM. If the channel environment is bad, it uses a low-

order modulation, such as QPSK and a low coding rate to minimize channel errors.

In addition, in the environment where MIMO mode can be used, the eNB operates in

MIMO mode to increase the peak data rate of subscribers and can greatly increase the cell

throughput.

If the channel information obtained is incorrect or modulation method of higher order or

higher coding rate than the given channel environment is used, errors may occur.

In such cases, the errors can be corrected by the HARD function.

H-ARQ

The H-ARQ is a retransmission method in the physical layer, which uses the stop-and-wait

protocol. The eNB provides the H-ARQ function to retransmit or combine frames in the

physical layer so that the effects of wireless channel environment changes or interference

signal level changes can be minimized, which results in throughput improvement.

The LTE uses the Incremental Redundancy (IR)-based H-ARQ method and regards theChase Combining (CC) method as a special case of the IR method.

The eNB uses the asynchronous method for downlink and the synchronous method for

uplink.

Power Control

When transmitting a specific data rate, too high a power level may result in unnecessary

interferences and too low a power level may result in an increased error rate, causing

retransmission or delay. Unlike in other schemes such as CDMA, the power control is

relatively less important in LTE. Nevertheless, adequate power control can improve

performance of the LTE system.

In the LTE uplink, SC-FDMA is used so that there are no near-far problems that occur in

the CDMA. However, the high level of interference from nearby cells can degrade the

uplink performance.

Therefore, the UE should use adequate power levels for data transmission in order not to

interfere with nearby cells. Likewise, the power level for each UE could be controlled for

reducing the inter-cell interference level.

In the LTE downlink, the eNB can reduce inter-cell interference by transmitting data at

adequate power levels according to the location of the UE and the MCS, which results in

improvement of the entire cell throughput.


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Inter-Cell Interference Coordination (ICIC)

Since the UEs within a cell in LTE use orthogonal resources with no interference between

the UEs, there is no intra-cell interference.However, if different UEs in neighbor cells use the same resource, interference may occur.

This occurs more seriously between the UEs located on the cell edge, resulting in serious

degradation at cell edge.

A scheme used to relieve such inter-cell interference problem on the cell edge is ICIC.

ICIC allows interference signals to be transmitted to other cells in the cell edge area in as

small an amount as possible by allocating a basically different resource to each UE that

belongs to a different cell and by carrying out power control according to the UE’s location

in the cell.

The eNBs exchange scheduling information with each another via X2 interface for

preventing interferences by resource conflicts at cell edges. If the interference of a neighborcell is too strong, the system informs the other system to control the strength of the

interference system.

The ICIC scheme is used to improve the overall cell performance.

MIMO

The LTE eNB supports 2Tx/2Rx or 4Tx/4Rx MIMO by default using multiple antennas.

To achieve this, there must be in the eNB channel card the RF part that can separately

process the baseband part and each path for MIMO processing. The LTE eNB provides

high-performance data services by supporting several types of MIMO.

2.2.2 Call Processing Function

Cell Information Transmission

In a serving cell, the eNB periodically transmits a Master Information Block (MIB) and

System Information Blocks (SIBs), which are system information, to allow the UE that

receives them to perform proper call processing.

Call Control and Air Resource Assignment

The eNB allows the UE to be connected to or disconnected from the network.When the UE is connected to or released from the network, the eNB transmits and receives

the signaling messages required for call processing to and from the UE via the Uu interface,

and to and from the EPC via the S1 interface.

When the UE connects to the network, the eNB performs call control and resource

allocation required for service. When the UE is disconnected from the network, the eNB

collects and releases the allocated resources.


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Handover

The eNB supports intra-frequency or inter-frequency handover between intra-eNB cells,

X2 handover between eNBs, and S1 handover between eNBs. It also processes signalingand bearer for handover. At intra-eNB handover, handover-related messages are transmitted

via internal eNB interfaces; at X2 handover, via the X2 interface; at S1 handover, via the

S1 interface.

To minimize user traffic loss during X2 and S1 handovers, the eNB performs the data

forwarding function. The source eNB provides two forwarding methods to the target eNB:

direct forwarding via the X2 interface and indirect forwarding via the S1 interface.

The eNB allows the UE to receive traffic without loss through the data forwarding method

at handover.

Handover Procedure

For more information on the handover procedure, see the ‘Message Flow’ section

below.

Admiss ion Control ( AC)

The eNB provides capacity-based admission control and QoS-based admission control for

a bearer setup request from the EPC so that the system is not overloaded.

Capacity-based admission control

There is a threshold for the maximum number of connected UEs (new calls/handovercalls) and a threshold for the maximum number of connected bearers that can be

allowed in the eNB. Call admission is determined depending on whether the connected

UEs and bearers exceed the thresholds.

QoS-based admission control

The eNB determines whether to admit a call depending on the estimated PRB usage of

the newly requested bearer, the PRB usage status of the bearers in service, and the

maximum acceptance limit of the PRB (per bearer type, QCI, and UL/DL).

RLC ARQ

The eNB performs the ARQ function for the RLC Acknowledged Mode (AM) only.

When receiving and transmitting packet data, the RLC transmits the SDU by dividing it

into units of RLC PDU at the transmitting side and the packet is retransmitted (forwarded)

according to the ARQ feedback information received from the receiving side for increased

reliability of the data communication.


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QoS Support

The eNB receives the QoS Class Identifier (QCI) in which the QoS characteristics of the

bearer are defined and the GBR, the MBR, and the Aggregated Maximum Bit Rate (UE-AMBR) from the EPC. It provides the QoS for the wireless section between the UE and the

eNB and the backhaul section between the eNB and the S-GW.

Via the air interface, it performs retransmission to satisfy the rate control according to the

GBR/MBR/UE-AMBR values, priority of bearer defined in the QCI, and scheduling

considering packet delay budget, and the Packet Loss Error Rate (PLER).

Via the backhaul interface, it performs QCI-based packet classification, QCI to DSCP

mapping, and marking for the QoS. It provides queuing depending on mapping results, and

each queue transmits packets to the EPC according to a strict priority, etc.

In the Element Management System (EMS), in addition to the QCI predefined in the

specifications, operator-specific QCI and QCI-to-DSCP mapping can be set.

SYNC Handler Function

eNB provides the Synchronization (SYNC) protocol function to the backhaul section

between the eNB and MBMS-GW for each Temporary Mobile Group ID (TMGI) of the

MBMS bearer from MME.

2.2.3 IP Processing

IP QoS

The eNB can provide the backhaul QoS when communicating with the EPC by supporting

the Differentiated Services (DiffServ).

The eNB supports 8 class DiffServ and mapping between the services classes of the user

traffic received from the MS and DiffServ classes. In addition, the eNB supports mapping

between the Differentiated Services Code Points (DSCP) and the 802.3 Ethernet MAC

service classes.

IP Routing

Since the eNB provides multiple Ethernet interfaces, it stores in the routing table the

information on which Ethernet interface the IP packets will be routed to. The routing tableof the eNB is configured by the operator. The method for configuring the routing table is

similar to the standard router configuration method.

The eNB supports static routing settings, but does not support dynamic routing protocols

such as Open Shortest Path First (OSPF) or Border Gateway Protocol (BGP).

IP Multicast Routing

The eNB provides multiple Ethernet interfaces and it stores information on which Ethernet

interface IP packets will be routed to in the routing table.

The routing table of eNB is configured by the operator in the similar way to the router

standard configuration.


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Ethernet/VLAN Interface

The eNB provides Ethernet interfaces and supports the static link grouping, Virtual Local

Area Network (VLAN), and Ethernet CoS functions that comply with IEEE 802.3ad for

Ethernet interfaces. The MAC bridge function defined in IEEE 802.1D is not supported.

The eNB allows multiple VLAN IDs to be set for an Ethernet interface. To support

Ethernet CoS, it maps the DSCP value of the IP header to the CoS value of the Ethernet

header for Tx packets.

2.2.4 SON Funct ion

The SON function supports the self-configuration, self-establishment and self-optimization

function.

Self-Configuration and Self-Establishment

Self-configuration and self-establishment enable automatic setup of radio parameters and

automatic configuration from system ‘power-on’ to ‘in-service’, which minimizes the effort

in installing the system. The detailed functions are as follows.

Self-Configuration

Self-configuration of Initial Physical Cell Identity (PCI)

Self-configuration of initial neighbor information

Self-configuration of initial Physical Random Access Channel (PRACH)

information

Self-Establishment

Automatic IP address acquisition

Auto OAM connectivity

Automatic software and configuration data loading

Automatic S1/X2 setup

Self-test

Self-Optimization

PCI auto-configuration

The SON server of the LSM is responsible for allocating the initial PCI in the self-

establishment procedure of a new eNB, detecting a problem automatically, and

selecting, changing, and setting a proper PCI when a PCI collision/confusion occurs

with the neighbor cells during operation.

Automatic Neighbor Relation (ANR) optimization

The ANR function minimizes the network operator’s effort to maintain the optimal

NRT by managing the NRT dynamically depending on grow/degrow of the neighbor

cells. This function automatically configures the initial NRT of each eNB and

recognizes environment changes, such as cell grow/degrow or new eNB installation

during operation to maintain the optimal NRT. In other words, the ANR function

updates the NRT for each eNB by automatically recognizing topology changes such as

new neighbor cell or eNB installation/uninstallation and adding or removing the Neighbor Relation (NR) to or from the new neighbor cell.


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Mobility robustness optimization

The mobility robustness optimization function is the function for improving handover

performance in the eNB by recognizing the problem that handover is triggered at the

incorrect time (e.g. too early or too late) before, after, or during handover depending

on UE mobility, or handover is triggered to the incorrect target cell (handover to the

wrong cell) and then by optimizing the handover parameters according to the reasons

for the problem.

Random Access Channel (RACH) optimization

The RACH Optimization (RO) function minimizes the access delay and interference

through dynamic management of the parameters related to random access.

The RO function is divided into the initial RACH setting operation and the operation

for optimizing parameters related to the RACH. The initial RACH setting operation is

for setting the preamble signatures and the initial time resource considering theneighbor cells. The operation for optimizing parameters related to the RACH is for

estimating the RACH resources, such as time resource and subscriber transmission

power required for random access, that change depending on time, and for optimizing

the related parameters.

Mobility Load Balancing (MLB)

The MLB function monitors the cell’s load. If the load status satisfies the MLB

execution condition specified by the operator, this function moves a part of the traffic

to a neighbor cell through network-initiated HO. The MLB execution condition is

divided into the load equalization condition among multiple carriers, and the overload

condition of a cell.

2.2.5 Easy Operation and Maintenance

Through interworking with the management systems (LSM, Web-EMT, and CLI), the eNB

provides the maintenance functions such as system initialization and restart, system

configuration management, management of fault/status/diagnosis for system resources and

services, management of statistics on system resources and various performance data and

security management for system access and operation.

Graphics and Text Based Console Interfaces

The LSM manages all eNBs in the network using the Database Management System

(DBMS). The eNB also interworks with the console terminal to allow the operator to

connect directly to the Network Element (NE), rather than through the LSM, and perform

the operations and maintenance.

The operator can use the graphics-based console interface (Web-EMT, Web-based Element

Maintenance Terminal) or the text-based Command Line Interface (CLI) according to user

convenience and work purposes. The operator can access the console interfaces without

additional software. For the Web-EMT, the operator can log in to the system using Internet

Explorer. For the CLI, the operator can log in to the system using the telnet or the Secure

Shell (SSH) in the command window.


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The operator can perform the management of configuration and operational information,

management of fault and status, and monitoring of statistics and so on. To grow/degrow

resources or configure a neighbor list that contains relation of multiple NEs, the operator

needs to use the LSM.

Operator Authentication Function

The eNB provides the authentication and privilege management functions for the system

operators.

The operator accesses the eNB using the operator’s account and password via the CLI.

At this time, the eNB grants the operator an operation privilege in accordance with the

operator’s level.

The eNB also logs the access successes and failures for CLI, login history, and so on.

Highly-Secured Maintenance

The eNB supports the Simple Network Management Protocol (SNMP) and SSH File

Transfer Protocol (SFTP) for security during communications with the LSM, and the

Hypertext Transfer Protocol over SSL (HTTPs) and Secure Shell (SSH) during

communications with the console terminal.

Online Software Upgrade

When a software package is upgraded, the EPC can upgrade the existing package while it is

still running.The package upgrade is done by downloading a new package activating of the new

package. The download and activation of a new package is performed using the Download

menu and Activation menu of the LSM GUI.

When upgrading the package, the service stops temporarily at the ‘change to the new

package’ step because the existing process needs to be stopped so that the new process can

start. Since the operating system does not need to be restarted, the service can be resumed

within several minutes. After upgrading the software, the eNB updates the package stored

in the internal nonvolatile storage.

Call Trace

The eNB supports the call trace function for a specific UE.

The operator can enable trace for a specific UE through the MME. The trace execution

results such as signaling messages are transmitted to the LSM.

IEEE 802.3ah

The eNB provides the IEEE 802.3ah Ethernet OAM function for the backhaul interface.

Although the IEEE 802.3ah OAM is for the physical layer, it is located on the MAC layer

to support the entire IEEE 802.3 PHY; the 802.3ah OAM frame is created and processed

according to the functions defined in the standards.


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The Ethernet OAM functions include the discovery function where the both ends of a link

discover each other to monitor the connectivity continuously and deliver the key link

events such as dying gasp; the remote loopback function; the link monitoring function to

monitor the error packets and deliver an event notification in case of abnormal threshold;

and the variable retrieval function for the 802.3ah standard MIB.

The eNB supports the response to the 802.3ah OAM function triggered by an external

active mode entity, loopback mode operation, and the 802.3ah Ethernet OAM passive

mode such as transmission of event notification.

OAM Traffic Throttl ing

The eNB provides the operator with the function for suppressing the OAM-related traffic

that can occur in the system using the operator command. At this time, the target OAM-

related traffic includes the fault trap messages for alarm reporting and the statistics filesgenerated periodically.

For the fault trap messages, the operator can suppress generation of alarms for the whole

system or some fault traps using the alarm inhibition command, consequently allowing the

operator to control the amount of alarm traffic that is generated. For the statistics files, the

operator can control the amount of statistics files by disabling the statistics collection

function for each statistics group using the statistics collection configuration command.


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2.3 Specifications

Key Specifications

The key specifications of the eNB are as follows:

Category Specifications

Air specification TD-LTE

Operating Frequency 2,300~2,400 MHz

Channel Bandwidth 20 MHz

Capacity 2x2 MIMO with CDD 1 carrier/9 sector

RF Power per Sector 40 W (4Tx Path)

Backhaul Links 100/1000 Base-T (RJ-45, 2 ports)

1000 Base-SX/LX (SFP, 2 ports)

CDU-RRU Interface CPRI 4.1 (Optic 4.9 Gbps)

Holdover 24 h

Input Power

The following table shows the power specifications for LTE eNB. The LTE eNB complies

with UL60950 safety standard for electrical equipment. If the operator wants AC power for

the system input voltage, it can be supplied using an additional external rectifier (installed

by the provider).


CDU -48 VDC (-40~-56 VDC)

RRU

Dimensions and Weight

The following table shows the dimensions and weight of the LTE eNB.


Dimensions (mm) CDU 434 (W) × 385 (D) × 88 (H)

RRU 340 (W) × 106 (D) × 425 (H)

Weight (kg) CDU 12 or less

RRU Approx. 14


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GPSR Specifications

The following table shows the specifications of the LTE eNB’s GPS Receiver (GPSR).


Received Signal from GPS GPS L1 Signal

Accuracy/Stability 0.02 ppm

Ambience Conditions

The following table shows the operating temperature, humidity level and other ambient

conditions and related standard of the CDU.


Temperature Conditiona)

0~50°C

Humidity Conditiona)

10~90 %

The moisture content must not exceed 24 g per 1 m3 of air.

Altitude -60~1,800 m

Vibration - Telcordia GR-63-CORE

- Earthquake

- Office Vibration

- Transportation Vibration

Sound Pressure Level Max. 60 dBA at distance of 0.6 m and height of 1.5 m

EMI FCC Part 15

a) Temperature and humidity are measured at 1.5 m above the floor and at 400 mm away from the front

panel of the equipment.

The following table shows the ambient conditions and related standard of the RRU.


Temperature Conditiona)

-10~50°C

Humidity Conditiona)

5~95 %

The moisture content must not exceed 24 g per 1 m3

of air. Altitude -60~1,800 m

Earthquake Earthquake (Zone4)

Vibration - Telecodia GR-63 Core

- Office Vibration

- Transportation Vibration

Sound Pressure Level Max. 65 dBA at 1.5 m distance and 1 m height.

Dust and waterproof rating IP65

EMI FCC Part 15

a) Temperature and humidity are measured at 1.5 m above the floor and at 400 mm away from the frontpanel of the equipment.


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2.4 Intersystem Interface

2.4.1 Interface StructureThe eNB provides the following interfaces for interworking between NEs.

Figure 3. Inter-System Interface Structure

Interface between eNB and UE

The eNB, in compliance with the 3GPP LTE Uu air interface standard, transmits and

receives control signals and subscriber traffic to and from the UE.

Interface between eNB and S-GW

The interface between S-GW and eNB is 3GPP LTE S1-U, and the physical access

method is GE/FE.

Interface between eNB and MME

The interface between MME and eNB is 3GPP LTE S1-MME, and the physical access

method is GE/FE.

Interface between eNB and neighbor eNB

The inter-eNB interface is 3GPP LTE X2-C/X2-U, and the physical access method is

GE/FE.

Interface between eNB and LSM

The interface between the eNB and the LSM complies with the IETF

SNMPv2c/SNMPv3 standard, the FTP/SFTP standard, and the proprietary standard ofSamsung; the physical connection method is GE/FE.

PDN

EPC

S-GW

PCRF

eNB

UE

P-GW

MME

eNB

S1-U S1-MME

Uu

X2-C

S6a

Gx

SpS5/S8

S11

S10

SNMP/FTP/UDP

CSM

EMS

HSSTL1

eNBSmart Scheduler ServerSNMP/FTP/UDP

SC-1SC-1

LSMX2-U

EMS


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Interface between eNB and Smart Scheduler Server

The interface between the eNB and the Smart Scheduler server complies with the UDP

standard; the physical connection method is GE.

Interface between Smart Scheduler Server and LSM

The interface between the Smart Scheduler server and LSM complies with the

FTP/SNMP/UDP standard; the physical connection method is GE.

2.4.2 Protocol Stack

The inter-NE protocol stack of the eNB is as follows:

Protocol Stack between UE and eNB

The user plane protocol layer consists of the PDCP, RLC, MAC, and PHY layers.The user plane is responsible for transmission of the user data (e.g. IP packets) received

from the upper layer. In the User plane, all protocols are terminated in the eNB.

The control plane protocol layer is composed of the NAS layer, RRC layer, PDCP layer,

RLC layer, MAC layer and PHY layer. The NAS layer is located on the upper wireless

protocol. It performs UE authentication between UE and MME, security control, and

paging and mobility management of UE in the LTE IDLE mode.

In the control plane, all protocols except for the NAS signal are terminated in the eNB.

Figure 4. Protocol Stack between UE and eNB

NAS

RRC

PDCP

RLC

MAC

L1

NAS

S1-AP

SCTP

IP

L2

L1

RRC

PDCP

RLC

MAC

L1

S1-AP

SCTP

IP

L2

L1

UE LTE-Uu eNB

Relay

MMES1-MME


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Protocol Stack between eNB and EPC

The eNB and the EPC are connected physically through the FE and GE method, and the

connection specification should satisfy the LTE S1-U and S1-MME interface. In the user plane, the GTP-User (GTP-U) is used as the upper layer of the IP layer; and in the Control

plane, the SCTP is used as the upper layer of the IP layer.

The figure below shows the user plane protocol stack between the eNB and S-GW.

Figure 5. Protocol Stack between eNB and S-GW User Plane

The figure below shows the control plane protocol stack between the eNB and MME.

Figure 6. Protocol Stack between eNB and MME Control Plane

S1-MME

S1-UeNB

UDP

IP

L2

L1

S-GW

UDP

IP

L2

L1

GTP-U GTP-U

User Plane

PDUs

User Plane

PDUs

S1-MMEeNB

IP

L2

L1

MME

IP

L2

L1

SCTP SCTP

S1-AP S1-AP


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Inter-eNB Protocol Stack

The eNB and the eNB are connected physically through the FE and GE method, and the

connection specification should satisfy the LTE X2 interface. The figure below shows theinter-eNB user plane protocol stack.

Figure 7. Inter-eNB User Plane Protocol Stack

The figure below shows the control plane protocol stack.

Figure 8. Inter-eNB Control Plane Protocol Stack

X2eNB

UDP

IP

L2

L1

eNB

UDP

IP

L2

L1

GTP-U GTP-U

User Plane

PDUs

User Plane

PDUs

X2eNB

IP

L2

L1

eNB

IP

L2

L1

SCTP SCTP

X2-AP X2-AP


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Protocol Stack between eNB and LSM

The FE and GE are used for the physical connection between eNB and LSM, and the

connection specifications must satisfy the FTP/SNMP interface. The figure below showsthe user plane protocol stack between the eNB and LSM.

Figure 9. Interface Protocol Stack between eNB and LSM

Protocol Stack between eNB and Smart Scheduler Server (SC-1)

The eNB must provide the interface in CDU for the interoperation with the Smart

Scheduler server.

Figure 10. Protocol Stack between eNB and Smart Scheduler Server

FTP/SNMPeNB

IP

L2

L1

LSM

IP

L2

L1

TCP UDP

FTP SNMP

TCP UDP

FTP SNMP

UDP

IP

L2

Smart

Scheduler

Protocol

eNB

L1

UDP

IP

L2

Smart

Scheduler

Protocol

Smart Scheduler Sever

L1

SC-1


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Protocol Stack between Smart Scheduler Server and LSM (SNMP/FTP/UDP)

The physical connection uses FE and GE and the connection must be made via FTP/SNMP/UDP

interface. The figure below shows the interface protocol stack between Smart Scheduler serverand LSM.

Figure 11. Protocol Stack between Smart Scheduler Server and LSM

2.4.3 Physical Interface Operation

The eNB is the EPC interface which provides the interface of two types: copper and optic

interface. The interface type can be selected depending on the network configuration.

The number of interfaces to operate can be selected depending on the capacity and required

bandwidth of the eNB.

The types of interface are as follows:

Interface Type Port Type Max Port count

Copper 1000 Base-T (RJ-45) 2

Optic 1000 Base-LX/SX (SFP) 2

FTP/SNMP/UDP

IP

L2

L1

FTP SNMP FTP SNMP

TCP UDP TCP UDP

IP

L2

L1

Smart Scheduler Sever LSM


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2600-00F22GGA2 5.0

CHAPTER 3. System Structure

3.1 Hardware Structure

LTE eNB is the system consists of the Cabinet DU (CDU) which is a common platform

DU, and the Remote Radio Unit (RRU) which is an RU.The CDU is connected to the RRU through CPRI and it can provide up to 1carrier/9sector

service.

The following figure shows the configuration of the LTE eNB.

Figure 12. Internal Configuration of eNB

4Tx/4Rx is supported by default in the CDU, and up to three L9CAs (LTE eNB Channel

card board Assembly) can be mounted. Up to 20 MHz 1 carrier/9 sector can be supported.

Power (-48 VDC)

R

R

U

(8)

R

R

U

(0)

4.9 Gbps CPRI Interface

L9CA

UAMA

Analog 10 MHz1 PPSUDA (9Rx/2Tx)

Rectifier control (RS-485/FE)

EPC

UDE (FE)

Rectifier

GPS

FE/GE

CDU

R

R

U

(1)

…

Alarm/Control

CPRI Interface (Optic)

Clock

Backhaul

Data Traffic + Alarm/Control (Ethernet)

Index


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The L9CA has a capacity of 1 carrier/3 sector (4Tx/4Rx) per board by default.

The four slots of the CDU are multi-board type slots where the UAMA carries out the main

processor function, network interface function, clock generation and distribution function,

provider-requested alarm processing, etc. and the L9CA carries out the modem function.

The power module, fan, and air filter are also installed.

The RRU is an RF integration module consisting of a transceiver, power amplifier, and

filter. It sends and receives traffic, clock information, and alarm/control messages to and

from the L9CA. It employs the 4Tx/4Rx configuration with optic CPRI support.

Each RRU is connected an optic CPRI; up to three RRUs can be connected to a L9CA.

LTE Mult i-Carrier

Multi-Carrier function will be supported after additional schedule, if vendor required.

(to be later)

3.1.1 CDU

The CDU is the multi-board type in which the UAMA that carries out the main processor

function, network interface function, and clock creation and distribution function and the

L9CA that carries out the modem function are mounted. It consists of the power module

(PDPM), FANM-C4, and air filter. The CDU is mounted on a 19 inch rack, with fan

cooling and EMI available in each unit, and supports a RRU and optic CPRI interface.

The following figure shows the CDU configuration:

Figure 13. CDU Configuration

The following table shows the key features and configurations of each board.

Board Quantity Description

UADB 1 Universal platform type A Digital Backplane board assembly

- CDU backboard- Routing signals for traffic, control, clocks, power, etc.

UAMA Air filter

FANM-C4

Power

L9CA


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Board Quantity Description

UAMA 1 Universal platform type A Management board Assembly

- Main processor in the system- Resource allocation/operation and maintenance

- Collects alarms and reports them to the LSM.

- Backhaul support (GE/FE)

- CDU fan alarm processing

- Rectifier alarm interface

- User Defined Ethernet (UDE) and User Defined Alarm (UDA)

- Generation and supply of GPS clocks

L9CA Max. 3 LTE eNB Channel card board Assembly

- Call processing, resource assignment, operation, and maintenance

- OFDMA/SC-FDMA Channel Processing

- CPRI optic interface with RRU (E/O and O/E conversion in CPRI Mux)

- Max 1 Carrier/3 Sector @20 MHz, Max. 4Tx/4Rx (UL-SIMO)

- 3 Optic port

FANM-C4 1 Fan Module-C4

CDU cooling fan module

UAMA

The functions of the UAMA are as follows:

Main processor

The UAMA is the main processor of the eNB. The UAMA performs communication path setup between the UE and the EPC, Ethernet switching within the eNB, system

operation and maintenance. It also manages the status for all hardware/software in the

eNB, allocates and manages resources, collects alarms, and reports all status

information to the LSM.

Network interface

The UAMA directly interfaces with the EPC through the GE/FE and supports a total of

four ports (two optic and two copper ports). If only one type of port (either optic or

copper) is used, ports not in use can be other UDEs.

External interfacing

The UAMA provides Ethernet interface for UDE on the CDU.

The UAMA also provides the path to the alarm information generated in the external

devices (auxiliary devices provided by a service provider), and reports such alarm

information to the LSM.

Reset

The UAMA provides the reset function for each board.

Clock generation and distribution

When the eNB operates independently, the UAMA creates the 10 MHz, even System

Frame Number (SFN) by using the signal [PP2S (Even Clock), Digital

10 MHz] received from the Universal Core Clock Module (UCCM), and distributes itto the hardware blocks in the system.


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These clocks are used to maintain internal synchronization in the eNB and operate the

system.

The UAMA also provides the analog 10 MHz and 1 pps for interworking with

measuring equipments.

The UCCM transmits the time and location information through the Time Of Day

(TOD) path. If it is unable to receive the GPS signal due to fault, it performs the

holdover function to provide the existing normal clock for a specific time period.

L9CA

The functions of the L9CA are as follows:

Subscriber channel processing

The L9CA modulates the packet data received from the UAMA and transmits it

through the CPRI to the RRU. Reversely, it demodulates the data received from theRRU and converts it to the format defined in the LTE physical layer standard and

transmits it to the UAMA.

CPRI interface

The L9CA interfaces with the RRU through CPRI. As the L9CA contains a built-in

Electrical to Optic (E/O) conversion device and an Optic to Electrical (O/E)

conversion device, it can transmit and receive ‘Digital I/Q and C & M’ signals

between remote RRUs. The L9CA can also run loopback tests to check whether the

interface between the L9CA and RRUs is in good condition for proper communication.

If necessary, the operator can run loopback tests using the LSM command.

FANM-C4

The FANM-C4 is the system’s cooling fan used to maintain the internal CDU shelf

temperature. With this fan, the system can operate normally when the outside temperature

of the CDU shelf changes.


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3.1.2 RRU

The RRU is installed outdoor by default, adopts a natural cooling system.

The RRU, having 4Tx/4Rx RF chains, is an integrated RF module consisting of a

transceiver, a power amplifier, and a filter in an outdoor enclosure.

The major functions of the RRU are as follows:

2.3 GHz (2,300~2,400 MHz)

Supports 20 MHz 4Tx/4Rx per RRU

Supports contiguous 20 MHz 1 carrier/1 sector

10 W per path (Total 40 W)

Up/Down RF conversion

Performs LNA function

Amplifies the RF signal level

Suppresses spurious waves from the bandwidth

Includes E/O and O/E conversion module for the optical communication with CDU

Supports Remote Electrical Tilt (RET)

Figure 14. RRU Configuration

In the downlink path, the RRU performs O/E conversion for the baseband signals received

from the CDU via the optic CPRI. The converted O/E signals are converted again into

analog signals by the DAC.

[Front View] [Bottom View]


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The frequency of those analog signals is converted upward through the modulator and then

those signals are amplified into high-power RF signals through the power amplifier.

The amplified signals are transmitted to the antenna through the filter part.

In the uplink path, the RF signals received through the filter of the RRU are low-noise

amplified in the Low Noise Amplifier (LNA) and their frequency is then down-converted

through the demodulator. These down-converted frequency signals are converted to

baseband signals through the ADC. The signals converted into baseband are changed to

E/O through the CPRI and transmitted to the CDU.

The control signals of the RRU are transmitted through the control path in the CPRI.

To save energy, the RRU provides the function to turn on or off the output of the power

amplifier through to the software command set according to traffic changes.

When adjusting the maximum output after the initial system installation, the RRU adjusts

the voltage applied to the main transistor through the software command set in high/low

mode to optimize the efficiency of the system.

3.1.3 Power Supply

The power diagram below shows the type of power supply to the eNB and connection

points.

Figure 15. Power Supply Configuration

U

A

M

A

L

9

C

A

L

9

C

A

L

9

C

A

F

A

N

M

-

C

4

CDU

PDPM

EMI Filter

-48 VDC (-40~-56 VDC)

Rectifier Rectifier

R

R

U

(0)

R

R

U

(1)

R

R

U

(2)

-48 VDC (-40~-56 VDC)

UADB


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The power for UAMA and L9CAs in the CDU is supplied through the Power Distribution

Panel Module (PDPM) and UADB, a backboard. Each board uses the power by converting

the -48 VDC provided into the power needed for each part on the board.

3.1.4 Cooling Structure

CDU

The CDU maintains the inside temperature of the shelf at an appropriate range using a

system cooling fans (FANM-C4),

With this fan, the system can operate normally when the outside temperature of the CDU

shelf changes.

The following shows the heat radiation structure of the CDU.

Figure 16. Cooling Structure of CDU

RRU

The RRU is designed to discharge heat effectively through natural cooling without an

additional cooling device.

FANM-C4 Air Filter


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3.1.5 External Interface

External Interfaces of CDU

The following shows the interfaces of CDU.

Figure 17. CDU External Interface

Unit Interface Description

PWR RTN/-48 V Power Input (RTN/-48 VDC)

FANM-C4 PWR/ALM FAN Module LED

UAMA ACT CPU Active LED

GPS UCCM Status LED

RST Reset Switch (CPU Chip Reset)

DBG SW Debug (UART, RS-232)

UDA User Defined Alarm (Rx: 9 port, Tx: 2 port), Mini Champ

BH0, BH1 Copper Backhaul (100/1000 Base-T), RJ-45

UDE0, UDE1 User Defined Ethernet (100 Base-T), RJ-45

EDBG SW Debug (100 Base-T), RJ-45

REC Rectifier, RS-485

BH2, BH3 1000 Base-LX/SX, SFP

1PPS Test Port 1PPS Output (from UCCM), SMA

A10M Test Port Analog 10 M Output (from UCCM), SMA

GPS GPS ANT Input (to UCCM), SMA

L9CA ACT L9CA ACT LED

RST System reset

DBG0, DBG1 UART DSP Debug, USB

L0~L5 RRU IF (CPRI 4.1), Optic

EDBG Debugger(100 Base-T), RJ-45

Air filter A/F Air filter

-48 V

FANM-C4

ACT GPS RST DBG UDA

Documents

223205200 1 LTE ENB System Description Ver 5 0 RIL en for Call Flow