LTE Parameter tuning PDF

Preview

Summary

LTE Parameters and Tuning Course Code: LT1001 Duration: 2 days Technical Level: 3 ... delivering knowledge, maximizing performance... LTE courses include: n LTE/SAE Engineering Overview n LTE Air Interface n LTE Radio Access Network n Cell Planning for LTE Networks n LTE Evolved Packet Core Network ...

Description

Accelerat ing t he world's research.

LTE Parameter tuning ahmed salah

Related papers

Download a PDF Pack of t he best relat ed papers 

LT E Air Int erface Training Manual Figures Figures Fadi Momani

An Int roduct ion t o LT E 2nd Ahmed Chaouli Cell search and cell select ion in UMT S LT E Applicat ion Not e Fressilya Tampubolon

LTE Parameters and Tuning Course Code: LT1001

Duration: 2 days

Technical Level: 3

... delivering knowledge, maximizing performance...

LTE courses include: n

LTE/SAE Engineering Overview

n

LTE Air Interface

n

LTE Radio Access Network

n

Cell Planning for LTE Networks

n

LTE Evolved Packet Core Network

n

4G Air Interface Technologies

n

LTE Technologies, Services and Markets

Wray Castle – leading the way in LTE training

www.wraycastle.com

LTE PARAMETERS AND TUNING

First published 2010 Last updated June 2011 WRAY CASTLE LIMITED BRIDGE MILLS STRAMONGATE KENDAL LA9 4UB UK

Yours to have and to hold but not to copy The manual you are reading is protected by copyright law. This means that Wray Castle Limited could take you and your employer to court and claim heavy legal damages. Apart from fair dealing for the purposes of research or private study, as permitted under the Copyright, Designs and Patents Act 1988, this manual may only be reproduced or transmitted in any form or by any means with the prior permission in writing of Wray Castle Limited. All of our paper is sourced from FSC (Forest Stewardship Council) approved suppliers.

© Wray Castle Limited

LTE Parameters and Tuning

ii

© Wray Castle Limited

LT1001/v2

LTE PARAMETERS AND TUNING

CONTENTS Section 1

Introduction

Section 2

Cell Structure, Configuration and Dimensioning

Section 3

Frequency Planning

Section 4

Idle Mode Parameters

Section 5

Connected Mode Parameters

Glossary

LT1001/v2

© Wray Castle Limited

iii

LTE Parameters and Tuning

iv

© Wray Castle Limited

LT1001/v2

LTE Parameters and Tuning

SECTION 1

INTRODUCTION

LT1001/v2

© Wray Castle Limited

1.i

LTE Parameters and Tuning

1.ii

© Wray Castle Limited

LT1001/v2

Introduction

CONTENTS Parameter Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.1 LTE Cell Configuration Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.2 Self-Optimizing Networks (SONs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.3 Self-Configuration and Self-Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.4 Channel Bandwidths and Subcarriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.5 Frequency Bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.6 Bandwidth Applicability in LTE Bands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.7 LTE Air Interface Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.8 System Information Broadcasting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.9 System Information Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.10 LTE Radio Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.11

LT1001/v2

© Wray Castle Limited

1.iii

LTE Parameters and Tuning

1.iv

© Wray Castle Limited

LT1001/v2

Introduction

OBJECTIVES At the end of this section you will be able to: ■

identify the functional entities and interfaces that are relevant to air interface parameters

■

suggest key LTE configurations parameters for the eNB

■

outline the procedures for self-configuration

■

outline the aims and process that could form part of a self-optimization process

■

summarize the LTE air interface spectrum band and bandwidth options

■

summarize the LTE air interface protocol stack and identify those protocols most relevant to radio resource management on the air interface

■

describe the system information broadcasting mechanism used in LTE and relate this to parameter identification

■

LT1001/v2

define the key radio measurements for LTE

© Wray Castle Limited

1.v

LTE Parameters and Tuning

1.vi

© Wray Castle Limited

LT1001/v2

Introduction

Parameters also determine interactions with neighbour cells for reselection and for handover

EPC

Some procedures require communication between eNBs over the X2 interface

Key parameters for LTE air interface impact the relationship between the UE and a serving cell on the eNB

Parameter Scope The architecture for the LTE RAN (Radio Access Network) is IP-based and very simple in terms of functional nodes. Management for all functions that occur within a cell is performed by the eNB, which in effect includes the functions that for 2G and 3G would have been performed by the BSC or RNC. Thus when considering the operation and the parameters for the air interface it is largely independent of the RAN and the core network. Nevertheless, some functions, particularly for an SFN (Single Frequency Network) configuration, are dependent on communication between eNBs. Therefore the behaviour and functions supported over the X2 interface do have a bearing on air interface operation. This is not to say that the performance of the air interface is independent of the RAN (Radio Access Network) as a whole or of the core network. The provision of adequate QoS (Quality of Service) on the air interface is only possible with appropriately dimensioned and managed resources for transmission and switching in the network as a whole. The importance of QoS management in this context depends on the type of services offered in the LTE network of interest.

LT1001/v2

© Wray Castle Limited

1.1

LTE Parameters and Tuning

Cell Configuration Parameters

eNB

FDD/TDD Frequency band Channel bandwidth Frequency allocation Cyclic prefix UL/DL switching point (TDD only) Control channel configuration Channel Power offsets Cell ID MIMO configuration

LTE Cell Configuration Parameters In addition to the standard cell parameters that are common with any other cellular technology there are a number of LTE-specific parameters that are required for successful LTE system operation. In the main, these parameters relate to the configuration of the physical layer and the way that control channels are mapped into it. In turn, the settings for these parameters are driven by spectrum availability, the feature set to be used and appropriate dimensioning for expected traffic and signalling loads.

1.2

© Wray Castle Limited

LT1001/v2

Introduction SON Aims continuously optimized and matched UL and DL coverage optimized DL and UL capacity of the system balanced trade-off between coverage and capacity interference reduction controlled cell-edge capacity minimized human intervention in network management and optimization tasks energy savings

SON functions

SON functions

OAM

Self-Optimizing Networks (SONs) A great deal of emphasis has been placed on a standardized approach to an network that is to some degree self-configuring. This concept is known as SON (Self-Optimizing Network). In general the principle of SON is that performance measurements received in real time from the network can be used to vary configuration parameters in the RAN. In the past, configuration parameters have been the sole preserve of optimization or network design engineers and most would be set at static or semi-static values. In a SON performance, analysis by an application is used to set, and crucially also to change, key parameters as network conditions change. The overall aim in this automation of the optimization process is to use resources in the most efficient way and at the same time maximize coverage and capacity.

Further Reading: 3GPP TR 36.902, TS 36.300; 22.4

LT1001/v2

© Wray Castle Limited

1.3

LTE Parameters and Tuning eNB power on (coms link active)

Basic set-up Self-Configuration

Configuration of IP address and detection of OAM Authentication of eNB and network

(Pre-operational state)

Association with a S-GW Downloading of eNB software (and operational parameters)

Initial radio configuration

Neighbour list configuration Coverage/capacity related parameter configuration

Self-Optimization (Operational state)

Optimization /adaptation

Neighbour list optimization Coverage and capacity control

Self-Configuration and Self-Optimization The self-configuration process is designed to allow a new eNB to obtain the basic configuration needed for system operation through automatic initialization procedures. The self-configuration process occurs while the eNB is in the ‘pre-operational’ state. In this state the eNB is powered on and has an active communications link, but the RF unit is not yet switched on. Once the eNB has obtained an initial radio configuration the RF unit is powered on and it becomes operational. At this point the self-optimizing process can begin. The self-optimization process allows the eNB to fine tune radio parameters in response to network activity.

Further Reading: 3GPP TR 36.902, TS 36.300; 22

1.4

© Wray Castle Limited

LT1001/v2

Introduction

20 MHz/1200 15 MHz/900 10 MHz/600 5 MHz/300 3 MHz/180 1.4 MHz/72

Channel bandwidths (bandwidth/subcarriers)

Channel Bandwidths and Subcarriers E-UTRA/LTE is designed to work in a variety of bandwidths ranging from 1.4 MHz to 20 MHz. The version of OFDMA (Orthogonal Frequency Division Multiple Access) employed by LTE is similar to the versions employed by WiMAX or DVB, but with a few key differences. In systems such as WiMAX, OFDMA schemes occupying different channel bandwidths employ different subcarrier spacing, meaning that there is a different set of physical layer parameters for each version of the system. The E-UTRA (Evolved Universal Terrestrial Radio Access) scheme allows for two fixed subcarrier spacing options; 15 kHz in most cases, with an optional 7.5 kHz spacing scheme, only applicable for TDD operation providing broadcast multimedia. Fixing the subcarrier spacing reduces the complexity of a system that can support multiple channel bandwidths.

Further Reading: 3GPP TS 36.211, 36.101:5.5, 36.104:5.5

LT1001/v2

© Wray Castle Limited

1.5

LTE Parameters and Tuning

FDD

TDD

Band

UL Range (MHz)

DL Range (MHz)

Band

UL/DL Range (MHz)

1 2 3 ... 7 8 ... 13 ... 20 ... 24

1920 – 1980 1850 – 1910 1710 – 1785 ... 2500 – 2570 880 – 915 ... 777 – 787 ... 832 – 862 ... 1626.5 – 1660.5

2110 – 2170 1930 – 1990 1805 – 1880 ... 2620 – 2690 925 – 960 ... 746 – 756 ... 791 – 821 ... 1525 – 1559

33 34 35 36 37 38 39 40

1900 – 1920 2010 – 2025 1850 – 1910 1930 – 1990 1910 – 1930 2570 – 2620 1880 – 1920 2300 – 2400

Frequency Bands There is considerable regional variation in the availability of spectrum for LTE operation and this is reflected in the standards. Along with flexibility in bandwidth there is considerable flexibility for spectrum allocation. There are no requirements for minimum band support nor for band combinations. It is assumed that this is determined by regional requirements. The standards currently identify 19 bands for FDD operation, ranging from frequencies of approximately 700 MHz through to frequencies in the range 2.7 GHz. There are also eight bands identified for TDD operation ranging from approximately 1900 MHz to 2.6 GHz. Considerable scope has been left in the standards to add more frequency bands as global requirements evolve.

Further Reading: 3GPP TS 36.101; 5.5, TS 36.104; 5.5

1.6

© Wray Castle Limited

LT1001/v2

Introduction FDD Band 1.4 MHz 3 MHz

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 17 18 19 20 21

TDD

5 MHz 10 MHz 15 MHz 20 MHz

Band 1.4 MHz 3 MHz

5 MHz 10 MHz 15 MHz 20 MHz

33 34 35 36 37 38 39 40

...

...

...

...

...

...

Bandwidth Applicability in LTE Bands Not all bandwidths are mandatory in all bands. Those bandwidths that are mandatory for a UE supporting each given band are shown in the table.

Further Reading: 3GPP TS 36.101; 5.6.1

LT1001/v2

© Wray Castle Limited

1.7

LTE Parameters and Tuning RRC

MAC

System information broadcasting Paging Connection management Temporary identity management Handover management QoS management NAS signalling direct transfer

Logical to transport channel mapping Scheduling Priority handling Random access procedure RNTI management HARQ process management

UE NAS EMM ECM

eNB Data Traffic

EPC NAS

NAS

EMM ECM

Data Traffic

AS

RRC

(Access Stratum)

RRC

PDCP

PDCP

RLC

RLC

MAC

MAC

Physical Layer

Physical Layer

LTE Air Interface Protocols The AS (Access Stratum), much of which for UMTS resided in the RNC, is located in the eNB for LTE. In addition, the functionality and complexity of RRC has been significantly reduced relative to that in UMTS. The main RRC functions are outlined in the diagram. The RRC is in overall control of radio resources in each cell and is responsible for collating and managing all relevant information related to the active UEs in its area. In regard of the control of radio resources and procedures that relate to the way radio resources are handled, RRC works very closely with the layer 2 protocol MAC (Medium Access Control). In effect, MAC micro-manages the key procedures in response to overall management of activity by RRC. Each eNB is responsible for managing inter-cell handovers between all the cells it controls. When handover to a cell on another eNB site is required the eNB will pass details of the current UE context to its neighbour. This includes details of identities used, historical measurements taken and active EPS bearers.

Further Reading: 3GPP TS 36.300, 36.331

1.8

© Wray Castle Limited

LT1001/v2

Introduction

eNB

Essential and basic frequently transmitted parameters

All other parameters with flexible scheduling indicated in SIB 1

SIB 1

MIB

SIB 2-13

SystemInformation message

IE BCCH MasterInformationBlock (40 ms periodicity)

BCH

DL-SCH

SystemInformationBlockType1 (80 ms periodicity)

SystemInformation (Other SIBs)

System Information Broadcasting System information provides the main means of advertising the configuration and parameters applicable in a cell. For LTE the BCH (Broadcast Channel) carries only basic information and acts as a pointer to broader system information related to the NAS (Non-Access Stratum), such as PLMN identity (network code and country code) and AS details such as cell ID and tracking area identity; all of which is carried in the downlink dynamically scheduled resource (DL-SCH). LTE has been designed with network sharing in mind and system information can carry details of up to six sharing PLMNs. A ‘bootstrap’ approach is adopted for system information broadcasting on the LTE air interface. The physical layer is primarily a dynamically scheduled resource with very little permanently defined capacity. Therefore, although a BCH transport channel and corresponding physical layer resource exist, this is only used to carry the MIB (Master Information Block). The position of the MIB can be determined by the UE as it performs initial synchronization with the cell. The MIB contains only basic information enabling the UE to find and read the RRC message SystemInformationBlockType1. This message in turn provides the scheduling information for the RRC SystemInformation messages being transmitted on the cell. SystemInformation messages contain one or more information elements, each of which will be a SIB (System Information Block). It is the SIBs that provide the complete set of system information for a UE. The operator determines which SIBs are transmitted, and how frequently, dependent on configurations, capabilities and services supported.

Further Reading: 3GPP TS 36.331; 5.2

LT1001/v2

© Wray Castle Limited

1.9

LTE Parameters and Tuning Type

Key Information

MIB

DL bandwidth, PHICH configuration, system frame number

SIB 1

SIB scheduling list, PLMN ID(s), TAC, cell barring info, cell selection parameters, frequency band info

SIB 2

Detailed cell barring info, UL frequency allocation, UL bandwidth, MBSFN information

SIB 3

Cell reselection information

SIB 4

Intra-frequency neighbour-cell descriptions

SIB 5

Inter-frequency E-UTRA neighbour-cell descriptions, cell-specific reselection parameters

SIB 6

Inter-RAT UMTS neighbour-cell descriptions, frequency-specific reselection parameters

SIB 7

Inter-RAT GSM/GPRS neighbour-cell descriptions, frequency-specific reselection parameters

SIB 8

Inter-RAT CDMA2000 neighbour-cell descriptions, frequency- and cell-specific reselection parameters

SIB 9

Home eNB name (text)

SIB 10

ETWS (Earthquake and Tsunami Warning System) primary notification

SIB 11

ETWS secondary notification

SIB 12

CMAS (Commercial Mobile Alert Service) notification

SIB 13

MBSFN information

System Information Messages The table provides a summary of the contents of the MIB, SystemInformationType1 message and SIB Types 2–13 currently defined for LTE operation.

Further Reading: 3GPP TS 36.331; 6.2.2, 6.3.1

1.10

© Wray Castle Limited

LT1001/v2

Introd...