LTE Performance Mgt & Opt_LZT1381554

LTE L15 Performance Management and Optimization

STUDENT BOOK LZT1381554 R1A

LZT1381554 R1A

LTE L15 Performance Management and Optimization

DISCLAIMER This book is a training document and contains simplifications. Therefore, it must not be considered as a specification of the system. The contents of this document are subject to revision without notice due to ongoing progress in methodology, design and manufacturing. Ericsson shall have no liability for any error or damage of any kind resulting from the use of this document. This document is not intended to replace the technical documentation that was shipped with your system. Always refer to that technical documentation during operation and maintenance.

© Ericsson AB 2015 This document was produced by Ericsson. •

The book is to be used for training purposes only and it is strictly prohibited to copy, reproduce, disclose or distribute it in any manner without the express written consent from Ericsson.

This Student Book, LZT1381554, R1A supports course number LZU1089937.

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Table of Contents

Table of Contents 1 LTE PERFORMANCE MANAGEMENT INTRODUCTION .............. 11 1

EPS INTRODUCTION...................................................................... 12

2

EPS QUALITY OF SERVICE ........................................................... 13

3

EPS BEARERS ................................................................................ 14

3.1

EPS DEFAULT BEARER ESTABLISHMENT ............................... 16

3.2

EPS DEDICATED ESTABLISHMENT .......................................... 18

4

LTE RAN EVOLUTION .................................................................... 20

5

LTE PERFORMANCE MANAGEMENT SOLUTION ........................ 22

5.1

PERFORMANCE STATISTICS..................................................... 22

5.2

PERFORMANCE RECORDING ................................................... 24

5.3

PERFORMANCE DATA ANALYSIS ............................................. 25

6

OPTIMIZATION SOLUTION ............................................................ 26

6.1

OPTIMIZATION CONCEPTS ........................................................ 26

6.2

E-UTRAN OBSERVABILITY ......................................................... 28

6.3

OPTIMIZATION WORKFLOW ...................................................... 30

7

E-UTRAN COUNTERS .................................................................... 32

7.1

E-UTRAN COUNTER TYPES ....................................................... 32

7.1.1

PEG COUNTER ......................................................................... 33

7.1.2

GAUGE COUNTER.................................................................... 34

7.1.3

ACCUMULATOR AND SCAN COUNTERS ............................... 35

7.1.4

PROBABILITY DENSITY FUNCTION (PDF) ............................. 36

7.2

E-UTRAN COUNTER EXAMPLES ............................................... 37

7.3

E-UTRAN COUNTER DESCRIPTIONS ........................................ 38

8

SUMMARY ....................................................................................... 40

2 LTE ACCESSIBILITY OPTIMIZATION ............................................ 41

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1

RANDOM ACCESS PROCEDURE .................................................. 42

1.1

CONTENTION BASED RANDOM ACCESS SUCCESS RATE .... 45

1.2

OVERSHOOTING CELL ............................................................... 46

1.3

UPLINK INTERFERENCE ............................................................ 47

1.4

RACH ROOT SEQUENCE PLANNING ........................................ 48

2

INITIAL E-RAB ESTABLISHMENT KPI ........................................... 50

2.1

RRC CONNECTION ESTABLISHMENT ...................................... 51

2.2

S1 SIGNALLING CONNECTION ESTABLISHMENT ................... 54

2.3

INITIAL E-RAB ESTABLISHMENT ............................................... 56

3

E-RAB ADDITION ............................................................................ 58

4

SUMMARY ....................................................................................... 60

3 LTE RETAINABILITY OPTIMIZATION ............................................ 61 1

EUTRAN RETAINABILITY KPI ........................................................ 62

1.1

E-RAB RELEASE PROCEDURE .................................................. 64

1.2

UE CONTEXT RELEASE PROCEDURE ...................................... 66

2

RETAINABILITY INVESTIGATION .................................................. 68

2.1

UE CONTEXT RELEASE FLOW CHARTS .................................. 68

2.2

E-RAB RELEASE FLOW CHART ................................................. 69

2.3

RADIO CONNECTION SUPERVISION ........................................ 70

3

FEATURES THAT IMPROVE RETAINABILITY ............................... 72

3.1

RRC CONNECTION RE-ESTABLISHMENT ................................ 72

3.2

MOBILITY AT POOR COVERAGE ............................................... 77

3.2.1 MOBILITY CONTROL AT POOR COVERAGE CONFIGURATION ................................................................................. 79 3.2.2 MOBILITY CONTROL AT POOR COVERAGE OBSERVABILITY................................................................................... 81 4

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SUMMARY ....................................................................................... 82

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Table of Contents

4 LTE L15 PERFORMANCE MANAGEMENT AND OPTIMIZATION ........................................................................... 83 1

EUTRAN INTEGRITY INTRODUCTION .......................................... 84

1.1

LTE TRAFFIC................................................................................ 84

1.1.1

WEB BROWSING TRAFFIC ...................................................... 85

1.1.2

EMAIL TRAFFIC ........................................................................ 86

1.1.3

VIDEO STREAMING TRAFFIC .................................................. 87

1.1.4

FILE DOWNLOAD TRAFFIC ..................................................... 88

1.1.5

VOICE TRAFFIC ........................................................................ 89

1.2

INTERNET PROTOCOLS USED FOR LTE TRAFFIC ................. 90

1.2.1

TRANSMISSION CONTROL PROTOCOL (TCP) ...................... 90

1.2.2

USER DATAGRAM PROTOCOL (UDP) .................................... 96

1.2.3

HYPERTEXT TRANSFER PROTOCOL (HTTP) ....................... 98

1.2.4

FILE TRANSFER PROTOCOL (FTP) ...................................... 100

1.2.5

VOICE OVER LTE ................................................................... 101

2

EUTRAN THROUGHPUT KPIS ..................................................... 103

2.1

DOWNLINK DRB TRAFFIC VOLUME ........................................ 106

2.2

UPLINK DRB TRAFFIC VOLUME .............................................. 107

2.3

UPLINK LCG TRAFFIC VOLUME ............................................... 108

3

EUTRAN LATENCY KPIS .............................................................. 109

3.1

DOWNLINK LATENCY MEASUREMENT .................................. 110

3.1.1 3.2

DISCONTINUOUS RECEPTION ............................................. 111 EUTRAN PACKET LOSS KPIS .................................................. 112

4

VOIP INTEGRITY........................................................................... 115

5

SUMMARY ..................................................................................... 117

5 LTE MOBILITY OPTIMIZATION .................................................... 119 1

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EUTRAN MOBILITY KPI ................................................................ 120

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1.1

INTRA LTE HANDOVER............................................................. 120

1.2

INTER-FREQUENCY AND WCDMA IRAT HANDOVER ............ 123

1.3

INTRA RBS HANDOVER ............................................................ 124

1.3.1

INTRA RBS HANDOVER PREPARATION .............................. 124

1.3.2

INTRA RBS HANDOVER EXECUTION ................................... 125

1.4

X2 BASED HANDOVER ............................................................. 126

1.4.1

X2 BASED HANDOVER PREPARATION................................ 126

1.4.2

X2 BASED HANDOVER EXECUTION .................................... 127

1.5

S1 BASED HANDOVER ............................................................. 129

1.5.1

S1 BASED HANDOVER PREPARATION................................ 129

1.5.2

S1 BASED HANDOVER EXECUTION .................................... 131

1.6

LTE TO WCDMA MOBILITY ....................................................... 132

1.6.1

COVERAGE-TRIGGERED WCDMA IRAT HANDOVER ......... 133

1.6.2 COVERAGE-TRIGGERED WCDMA SESSION CONTINUITY ....................................................................................... 136 2

CS FALLBACK TO WCDMA OR GSM .......................................... 137

3

OTHER USEFUL MOBILITY FORMULAS ..................................... 139

4

AUTOMATED NEIGHBOR RELATION .......................................... 140

5

UE LEVEL OSCILLATING HANDOVER MINIMIZATION .............. 143

6

AUTOMATED MOBILITY OPTIMIZATION .................................... 145

6.1

INTRA-LTE MOBILITY PROBLEMS ........................................... 146

6.2

FEATURE OVERVIEW ............................................................... 148

6.3

AUTOMATED MOBILITY OPTIMIZATION PARAMETERS ........ 148

7

SUMMARY ..................................................................................... 149

6 LTE AVAILABILITY AND SYSTEM UTILIZATION ....................... 151 1 1.1

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EUTRAN AVAILABILITY ................................................................ 152 EUTRAN CELL AVAILABILITY KPI ............................................ 153

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Table of Contents 2

LICENSE AND RESOURCE UTILIZATION INDICATORS ............ 154

2.1

LICENSES................................................................................... 155

2.1.1

DBB HARDWARE ACTIVATION CODES (HWAC) ................. 155

2.1.2

LTE CONNECTED USER LICENSES ..................................... 156

2.1.3

CUL USE DISTRIBUTION ....................................................... 157

2.1.4

CUL GRACE PERIOD.............................................................. 160

2.1.5

AVERAGE CUL PERCENTILE ................................................ 162

2.1.6

CUL TIME CONGESTION ....................................................... 163

2.1.7

AVERAGE NUMBER OF RRC CONNECTED USERS ........... 164

2.1.8

PEAK NUMBER OF RRC CONNECTED USERS ................... 165

2.1.9

DOWNLINK BASEBAND CAPACITY LICENSE ...................... 166

2.1.10

UPLINK BASEBAND CAPAITY ............................................. 168

2.2

SYSTEM LOAD ........................................................................... 170

2.2.1

DOWNLINK VOLUME .............................................................. 170

2.2.2

UPLINK VOLUME .................................................................... 171

2.2.3

ACTIVE UES ............................................................................ 172

2.2.4

ESTABLISHED E-RABS .......................................................... 174

2.2.5

SESSION TIME ........................................................................ 176

2.3

PHYSICAL RESOURCES ........................................................... 177

2.3.1

PDCCH UTILIZATION.............................................................. 177

2.3.2

PRB UTILIZATION ................................................................... 179

2.4 3

PROCESSOR LOAD................................................................... 183 SUMMARY ..................................................................................... 184

7 LTE CELL AND UE TRACE .......................................................... 185 1

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LTE CELL AND UE TRACE INTRODUCTION .............................. 186

1.1

LTE CELL TRACE....................................................................... 186

1.2

LTE UE TRACE........................................................................... 187

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2

LTE CELL AND UE TRACE CONTENTS ...................................... 188

2.1

INTERNAL EVENTS ................................................................... 188

2.1.1

INTERNAL_EVENT_................................................................ 189

2.1.2

UE_MEAS_ .............................................................................. 190

2.1.3

INTERNAL_PER_ .................................................................... 191

2.1.4

INTERNAL_PROC_ ................................................................. 192

2.2

EXTERNAL EVENTS .................................................................. 193

2.2.1

RRC EXTERNAL EVENTS ...................................................... 194

2.2.2

S1 EXTERNAL EVENTS.......................................................... 195

2.2.3

X2 EXTERNAL EVENTS.......................................................... 196

3

LTE CELL AND UE TRACE DECODING ....................................... 197

3.1

LTE TRACE DECODING EXAMPLE 1 ....................................... 198

3.2

LTE TRACE DECODING EXAMPLE 2 ....................................... 199

3.3

LTE TIMING ADVANCE .............................................................. 200

4

LTE CELL AND UE TRACE COLLECTION AND STORAGE ........ 203

4.1

LTE CELL TRACE FILE COLLECTION AND STORAGE ........... 204

4.2

LTE UE TRACE FILE COLLECTION AND STORAGE ............... 207

4.3

STREAMING OF CELL AND UE TRACE EVENTS .................... 210

4.4

TRACE DEPTH ........................................................................... 211

5

SUMMARY ..................................................................................... 213

8 OSS-RC STATISTICS, CELL AND UE TRACE HANDLING......... 215 1 1.1

LAUNCHING THE OSS-RC DATA COLLECTION GUI .............. 216

2

SYSTEM DEFINED SUBSCRIPTION PROFILES ......................... 217

3

USER DEFINED SUBSCRIPTION PROFILES .............................. 219

3.1 4

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INTRODUCTION ............................................................................ 216

ADDING A USER DEFINED PROFILE ....................................... 221 SUBSCRIPTION PROFILE HELP .................................................. 223

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Table of Contents 5 5.1

LTE CELL AND UE TRACE PARSING .......................................... 224 EXPORTING CELL AND UE TRACE ......................................... 227

6

REAL TIME KPIS ........................................................................... 228

7

NETWORK STATUS DISPLAY USER GUIDE .............................. 230

8

SUMMARY ..................................................................................... 231

9 ADVANCED MO SCRIPTING (AMOS) .......................................... 233 1

INTRODUCTION ............................................................................ 234

1.1

AMOS USER GUIDE .................................................................. 234

1.2

BASIC FUNCTIONS OF AMOS .................................................. 235

1.3

OPENING AN AMOS SESSION ................................................. 236

2

BASIC AMOS COMMANDS........................................................... 237

2.1

‘LC’ COMMAND .......................................................................... 237

2.2

‘PR’ COMMAND .......................................................................... 238

2.3

‘GET’ COMMAND ....................................................................... 239

2.4

‘SET’ COMMAND ........................................................................ 240

2.5

‘UE PRINT -ADMITTED’ COMMAND ......................................... 240

3

PERFORMANCE MANAGEMENT AMOS COMMANDS ............... 241

3.1

‘PST’ COMMAND ........................................................................ 242

3.2

‘PGETS’ COMMAND................................................................... 242

3.3

‘PMOM’ COMMAND.................................................................... 243

3.4

‘PMX’ COMMAND ....................................................................... 244

3.5

‘PGET’ COMMAND ..................................................................... 245

3.6

‘PDIFF’ COMMAND .................................................................... 246

3.7

’PMR’ COMMAND ....................................................................... 247

4

SUMMARY ..................................................................................... 248

10 ABBREVIATIONS ........................................................................ 249 11 INDEX .......................................................................................... 261

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12 TABLE OF FIGURES ................................................................... 263

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LTE Performance Management Introduction

1 LTE Performance Management Introduction

Objectives After completion of this chapter the participants will be able to: 1. Explain the E-UTRAN Performance Management solution 1.1 Explain the E-UTRAN Optimization Solution 1.2 Describe how eNodeB counters are collected and stored 1.3 Describe the eNodeB counter types and structures 1.4 Explain briefly Quality of Service concepts in EPS Figure 1-1: Objectives of Chapter 1

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1

EPS INTRODUCTION The Evolved Packet System (EPS) is made up of the Evolved Packet Core (EPC) and the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) as illustrated in Figure 1-2 below. Packet Switched Networks

2G/3G Core Network

SGi

EPS (Evolved Packet System) EPC (Evolved Packet Core)

Gx

HSS

S10

MME

SGs

S6a

MSC-S

PCRF

PGW

S5/S8 S11

S3

SGSN

WCDMA/GSM RAN

MME

S4

SGW

S1-MME E-UTRAN (Evolved UMTS Terrestrial Radio Access Network )

S1-U X2 LTE Uu

eNodeB

eNodeB

X2

eNodeB

X2

Figure 1-2: EPS Architecture

The EUTRAN provides connectivity between the User Equipment (UE) and EPC over the LTE UTRAN UE interface (LTE Uu) and S1-U interface for user data and S1-MME for signaling. The X2 interface is used to carry signaling between eNodeBs and optionally user when the ‘Data forwarding at intra LTE handover’ feature is used. The Serving Gateway (SGW) and Packet Data Network Gateway (PGW) in the EPC provide connectivity for user plane data from the eNodeB to the external IP Networks over the S5/S8 interface between the SGW and PGW and SGi interface between the PGW and the external IP Networks. The S5 is used when the SGW and PGW belong to the same Operator and S8 is used when they do not, in the case of roaming. The Policy and Charging Rules Function (PCRF) which handles policy control decisions and flow-based charging control communicates with the PGW over the Gx interface. The Mobility Management Entity (MME) is the control node in the EPS and uses the S11 interface to signal to the SGW, the S1-MME to signal to the eNodeB and the S6a to signal to the Home Subscriber Server (HSS). Communication between MMEs is supported by the S10 interface as illustrated in Figure 1-2 above.

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The SGs interface carries signalling information between the MSC-S and MME allowing UEs to be pages in LTE to perform Circuit Switched Fallback (CSFB) from LTE. The SGs interface may also be used to carry SMS over LTE. The S3 interface carries signalling information between the MME and SGSN to support Session Continuity from LTE. The S4 interface carries user data between the SGW and SGSN in the case of Packet Switched Handover (PSHO) from LTE. The MME and UE communicate with Non Access Stratum (NAS) messages carried across the S1-MME and LTE Uu interfaces.

2

EPS QUALITY OF SERVICE The 3GPP specify 9 Quality Class Indicators (QCI) for traffic carried by the EPS as illustrated in the table in Figure 1-3 below from TS23.203.

Priority

Packet Delay Budget

Packet Error Loss Rate

1

2

100 ms

10-2

Conversational Voice

2

4

150 ms

10-3

Conversational Video (Live Streaming)

5

300 ms

10-6

Non-Conversational Video (Buffered Streaming)

4

3

50 ms

10-3

Real Time Gaming

5

1

100 ms

10-6

IMS Signalling

QCI

3

Resource Type

GBR

Example Services

Voice, 6

7

100 ms

10-3

Video (Live streaming) Interactive Gaming

Non-GBR 7

6

8

8

9

9

10-6 300 ms

Video (Buffered Streaming) TCP-based (e.g., www, e-mail, chat, ftp, p2p file sharing, progressive video, etc.

Figure 1-3: Standardized QoS (TS23.203)

The 3GPP standardized QCI values illustrated in Figure 1-3 above can be divided into Guaranteed Bit Rate (GBR) and Non-Guaranteed Bit Rate (Non GBR). It is quite common for LTE Networks to carry only non GBR traffic and introduce GBR QCIs to support Voice over LTE (VoLTE). The Operator can optionally use more QCI values in their Network to support various service level distinctions for users, such as ‘Gold’, ‘Silver’ and ‘Bronze’ subscriptions etc.

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3

EPS BEARERS By definition there are two distinct types of EPS bearer, Default and Dedicated as illustrated in Figure 1-4 below. IMS Signaling (QCI 5) on Default Bearer

LTE QoS

VoIP Traffic (QCI 1) on Dedicated Bearer All other traffic (QCI 9) on Default Bearer

Dedicated Bearer Non-GBR QCI 5 - 9 APN – AMBR UE – AMBR TFT ARP L-EBI

Default Bearer

GBR QCI 1 - 4 GBR MBR TFT ARP L-EBI

Non-GBR QCI 5 - 9 APN – AMBR UE – AMBR APN IP Address ARP

QCI: Quality Class Indicator APN: Access Point Name AMBR: Aggregate Maximum Bit Rate UE: User Equipment TFT: Traffic Flow Template ARP: Allocation Retention Priority L-EBI: Linked EPS Bearer ID GBP: Guaranteed Bit Rate MBR: Maximum Bit Rate

Figure 1-4: Default and Dedicated Bearers

A typical example of the Default and Dedicated Bearers used when VoLTE is implemented using is illustrated in Figure 1-4 above. Full details of the Default and Dedicated Bearer characteristics are given below: GBR: The minimum guaranteed bit rate per EPS bearer. Specified independently for uplink and downlink MBR: The maximum guaranteed bit rate per EPS bearer. Specified independently for uplink and downlink A-AMBR: APN Aggregate maximum bit rate is the maximum allowed total nonGBR throughput to specific APN. It is specified interdependently for uplink and downlink UE -AMBR: UE Aggregate maximum bit rate is the maximum allowed total non-GBR throughput among all APN to a specific UE ARP: Allocation and retention priority is basically used for deciding whether new bearer modification or establishment request should be accepted considering the current resource situation.

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TFT: a Traffic flow template is always associated with a Dedicated Bearer. The TFT can be seen as a filter for IP addresses that routes particular IP packets to different QCI bearers. L-EBI: Stands for Linked EPS bearer ID. A Dedicated Bearer is always linked to Default Bearers.

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3.1

EPS Default Bearer Establishment During establishment of a Default Bearer the QoS requirements are carried in all the messages illustrated in Figure 1-5 below.

NAS Activate Default EPS Bearer Context Request

MME

S1AP Initial Context Setup Request

eNodeB

GTP-C Create Session Request

SGW

PGW

Figure 1-5: Default Bearer Establishment

An example of the QoS Information Elements of a NAS ‘Activate Default EPS Bearer Context Request’ message for QCI 9 are given in Figure 1-6 below.

NAS Activate Default EPS Bearer Context Request EPS Bearer Identity : 5

MME

QCI : (9) QCI 9 Access Point Name Value : ltemobile.apn.mnc18.mcc240.gprs PDN Address : 25.125.184.99 Maximum Bit Rate for Uplink : (254) Indicate higher than 8640 kbps Maximum Bit Rate for Downlink : (254) Indicate higher than 8640 kbps Guaranteed Bit Rate for Uplink : (255) 0 kbps Guaranteed Bit Rate for Downlink : (255) 0 kbps Maximum Bit Rate for Downlink (extended) : (247) 250 Mbps Maximum Bit Rate for Uplink (extended) : (158) 100 Mbps Radio Priority Level Value : (4) Priority level 4 (lowest) APN AMBR for Downlink : 250000 kbps APN AMBR for Uplink : 100000 kbps

Figure 1-6: Default Bearer (QCI 9)

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A Default Bearer may also be used for IMS signaling on QCI 5 as illustrated in the example in Figure 1-7 below.

NAS Activate Default EPS Bearer Context Request EPS Bearer Identity : 6

MME

QCI : (5) QCI 5 Access Point Name Value : ims.mnc18.mcc240.gprs PDN Address : 25.30.1.2 Maximum Bit Rate for Uplink : (247) 8192 kbps Maximum Bit Rate for Downlink : (254) Indicate higher than 8640 kbps Guaranteed Bit Rate for Uplink : (255) 0 kbps Guaranteed Bit Rate for Downlink : (255) 0 kbps Maximum Bit Rate for Downlink (extended) (100) 42 Mbps Maximum Bit Rate for Uplink (extended) : Use the value indicated by Radio Priority Level Value : (1) Priority level 1 (highest) APN AMBR for Downlink : 42000 kbps APN AMBR for Uplink : 8192 kbps

Figure 1-7: Default Bearer (QCI 5)

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3.2

EPS Dedicated Establishment During establishment of a Dedicated Bearer the QoS requirements are carried in all the messages illustrated in Figure 1-8 below.

NAS Activate Dedicated EPS Bearer Context Request

MME

S1AP E-RAB Setup Request

eNodeB

GTP-C Create Bearer Request

SGW

PGW

Figure 1-8: Dedicated Bearer Establishment

The QoS Information Elements of an example NAS ‘Activate Dedicated EPS Bearer Context Request’ message are given in Figure 1-9 below.

NAS Activate Dedicated EPS Bearer Context Request EPS Bearer Identity : 7

MME

Linked EPS Bearer Identity Value : (6) EPS bearer identity value 6 QCI : (1) QCI 1 Maximum Bit Rate for Uplink : 30 kbps Maximum Bit Rate for Downlink : 30 kbps Guaranteed Bit Rate for Uplink : 30 kbps Guaranteed Bit Rate for Downlink : 30 kbps TFT Operation Code : (1) Create new TFT Number of Packet Filters : 4 Packet Filter Identifier : 16 Component Type : (16) IPv4 source address type Address : 10.133.144.22 Radio Priority Level Value : (1) Priority level 1 (highest)

Figure 1-9: Dedicated Bearer (QCI 1)

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The NAS ‘Activate Dedicated EPS Bearer Context Request’ message illustrated in Figure 1-9 is used to set up EPS Bearer Identity 7 to carry voice traffic with QCI 1. Since this Dedicated Bearer is linked to EPS Bearer Identity 7 which is the IMS signaling bearer there is no need to assign a new IP address. Instead this message contains a Traffic Flow Template (TFT) which in this example contains 4 packet filters. Only the first filter for IP address 10.133.144.22 is shown here. Any packets that match the address in the TFT filters are carried with this Dedicated Bearer. Traffic Flow Templates (TFTs) are used by the UE and PGW to filter IP packets to be carried by the Dedicated Bearer. The TFTs are carried in the Non Access Stratum Activate Dedicated EPS Bearer Context Request message that is sent by the MME to the UE. The TFTs are a list of IP addresses that should be carried by the dedicated Bearer.

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LTE L15 Performance Management and Optimization

4

LTE RAN EVOLUTION Before starting to learn about Performance Management and Optimization it is important to understand where this set of activities are situated in the common RAN lifecycle and also to have a basic awareness of the previous stages and how they can affect the Performance Management / Optimization activities. The evolution of a LTE RAN begins with a Business Plan to provide a level of service to a defined area and number of subscribers as illustrated in Figure 1-10 below.

Figure 1-10: EUTRAN Evolution

During the Radio Network Design phase a detailed network plan is produced based on the requirements of the Business Plan. Site locations for the enodeBs must be found during the Site Acquisition phase with detailed drawings produces in the Site Engineering phase. After planning, applications have been approved in the Civil Works phase the eNodeBs are then installed in the Installation phase. During the Integration phase the eNodeBs are commissioned and brought into service. The Initial Tuning begins before any live traffic is carried by the network. During the Initial Tuning phase drive tests are made to ensure that it is possible to make and maintain sessions in the defined coverage area.

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Data collected during these drive tests are then used to analyze and locate any underlying problems related to the design of the network. The results from the Initial Tuning phase are normally antenna azimuth and/or downtilt changes or other network configuration changes. When the Initial Tuning is complete the network can be commercially launched. This may be done with friendly, non-paying users or actual fee paying subscribers. Once the network is carrying live traffic, Performance Management and Optimization can begin and will continue for the lifetime of the network. During this phase network statistics (counters) are collected from the nodes and used to create Key Performance Indicators (KPIs) to gauge the performance of the network against a defined set of targets. A detailed analysis of the network is required if these targets are not met. This is achieved using additional counters or any of the many optimization tools available to the Operator. The results of the optimization phase are normally parameter changes or other network configuration changes. In some instances a drive test may be required to give a better picture of the network performance during this phase. Initial Tuning and Optimization are usually offered as separate services as illustrated in Figure 1-11 below.

Figure 1-11: RAN Services

This course covers the EUTRAN Performance Management and Optimization process as opposed to Initial Tuning.

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LTE L15 Performance Management and Optimization

5

LTE PERFORMANCE MANAGEMENT SOLUTION The Performance Management solution of Ericsson LTE Network can be divided into the following areas: • Performance Statistics; • Performance Recording ; • Performance Data Analysis.

5.1

Performance Statistics User or system defined statistics ‘Subscription Profiles’ on the OSS-RC are used to configure the ‘Performance Monitorings (PMn)’ or ‘Scanners’ on the eNodeB. The PMs (scanners) will collect the required counters and store them in eXtensible Markup Language (XML) format in 15 min Report Output Period (ROP) files. These files are compressed by GZIP and stored on the eNodeB as illustrated in Figure 1-12 below. Performance Monitorings (PMs) (also called ‘scanners’) System Defined Created by the System Defined Subscription Profile (Primary for ENodeB) User Defined Created by the User Defined Subscription Profile

Subscription Profiles System Defined To collect counters required for the predefined reports. (Primary for eNodeB) User Defined Created by a user to collect counters not contained in the predefined profile.

PMS file system

OSS-RC Stats.xml

eNodeB

Stats.xml.gz

Figure 1-12: LTE Performance Statistics

The statistics ROP files are collected by the OSS-RC and stored, un-compressed, in its Performance Management System (PMS) file system as illustrated in Figure 1-12 above. The storage period for statistics files in the PMS file system is controlled by an OSS-RC system administration parameter which by default is set to 3 days.

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The statistics collection and storage parameters for the eNodeB can be viewed in the ‘PmSevice’ Managed Object via Element Manager or Amos. The default values for these parameters are listed in Figure 1-13 below.

ManagedElement +-SystemFunctions +-PmService maxNoOfCounters = 65000 {10000..350000} maxNoOfMonitors = 10 {1..30} maxNoOfPmFiles = 200 {10..200} performanceDataPath = /c/pm_data/ Figure 1-13: eNodeB Statistics Storage Parameters

It is important to know the eNodeB limitation regarding the maximum number of counters that can be activated by the operator, the maximum number of monitors that the eNodeB can handle at the same time, how many files will be stored and also the direction of the performance data files, so the Operator can access it directly via AMOS for example.

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LTE L15 Performance Management and Optimization

5.2

Performance Recording The LTE Performance Recording applications are used to collect events and radio related measurements applicable to either a particular UE in the case of a ‘LTE UE Trace’ or a particular cell in the case of a ‘LTE Cell Trace’. User defined LTE UE Trace or LTE Cell Trace ‘Subscription Profiles’ on the OSS-RC are used to configure the ‘Performance Monitorings (PMn)’ or ‘Scanners’ on the eNodeB. The PMs (scanners) will collect the events and radio related measurements and store them in Binary (Bin) format in 15 min Report Output Period (ROP) files. These files are compressed by GZIP and stored on the eNodeB as illustrated in Figure 1-14 below.

Performance Monitorings (PMs) (also called ‘scanners’) User Defined Created by the User Defined Subscription Profile

Subscription Profiles User Defined Created by a user to collect events and radio related measurements applicable to either a particular UE or cell

Trace LTE UE Trace

PMS file system

OSS-RC

Recording.bin

LTE Cell Trace

eNodeB

Recording.bin.gz

Figure 1-14: LTE Performance Recording

The performance recording ROP files are collected by the OSS-RC and stored, un-compressed in its Performance Management System (PMS) file system as illustrated in Figure 1-14 above. The storage period for performance recording files in the PMS file system is controlled by an OSS-RC system administration parameter which by default is set to 3 days. Only one UE can be selected for recording for each UE trace, but up to 16 simultaneous UE trace recordings can run in parallel for one eNodeB. Six Cell traces can be run in parallel in the eNodeB.

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5.3

Performance Data Analysis Ericsson Network IQ (ENIQ) is an optional tool that may be used to store the counters collected in the E-UTRAN and use them to produce various reports in order to assist with the performance monitoring of the network and troubleshooting. The statistics xml files stored in the OSS-RC PMS file system are processed by the ENIQ application and the counter values are extracted and stored in tables in the Sybase IQ Data Warehouse as illustrated in Figure 1-15 below. BIS: Business Intelligence Server

Business Objects BIS Predefined Reports

Predefined Reports

WAS: Windows Application Server WAS

Reports

User defined Reports

Sybase IQ Data Warehouse

ENIQ OSS-RC

OSS-RC eNodeB

PMS file system

Stats.xml

Stats.xml.gz

Figure 1-15: LTE Performance Data Analysis

The Ericsson LTE ENIQ Basic Report Package provides a number of Business Objects predefined reports based on the most important radio network Key Performance Indicators (KPIs). The ENIQ Business Intelligence Server (BIS) may be used to open and refresh these predefined reports or alternatively the ENIQ Windows Application Server (WAS) may be used to create user defined reports as illustrated in Figure 1-15 above. For troubleshooting purposes it is also possible to get direct access to counter values using the Advanced MO Scripting (AMOS) application. However in this course we will focus on performance management using ENIQ.

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LTE L15 Performance Management and Optimization

6

OPTIMIZATION SOLUTION

6.1

Optimization Concepts What is Optimization? It is important to understand that regardless of the domain (radio or core) and technology (i.e. GSM, WCDMA or LTE) optimization should be seen as a set of processes and activities that are based on the analysis of the system, followed by the elaboration and execution of recommended actions with the goal of assuring that the system is operating in the most efficient way and at its best performance. Thus, this maximizes Operator’s investments as well as end-user satisfaction. In order for the Engineer to be able to carry on with the Optimization tasks, some previous understandings must be in place, such as: • Knowledge on how the system works: What are the basic procedures taken place from the moment the user turns on the phone and place a call/data session to the moment he hangs up and what occurs/might occur in between as well as what may influence each process/element. In our specific case, the elements/processes related to the LTE RAN domain (E-UTRAN); • Awareness / ability to know how the system is performing. This is the concept of the Performance Management itself. It is achieved by means of specific Data Collection Tools, Key Performance Indicators (KPIs), management interfaces, etc. Given that, the engineer should then have the ability to evaluate the performance based on a set of Modules of KPIs and propose recommendations/actions in order to improve them and verify the results afterwards. Within this modules of KPIs to be optimized within the LTE domain (EUTRAN) there will be KPIs related to: • Accessibility: Measures the probability of a user to obtain an E-RAB from the system; • Retainability: Measures the capability of a user to retain the E-RAB once connected, for the desired duration; • Integrity: Measures the ability of the network to provide end-user services with the expected end-user quality and performance (i.e. throughput and latency); • Mobility: Measures the ability of the network to provide the desired service to the user within a certain mobility region seamlessly and continuously; • Availability: Measures the percentage of time that the cell is available; • Load: Will indicate utilization of the cell resources by means of traffic volume and processor load.

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This group of KPIs are part of the Observability model to be discussed further. The concepts of each one as well as the system functions that affects them (i.e. features and/or functionalities), the related Indicators and parameters respective to each one of this modules is the subject of the following chapters as well as some characteristics related to the helping tools and methods. The whole Optimization activity will be a closed loop process and will only end once the wanted result is achieved. The Optimization process can be illustrated by Figure 1-16 below.

Figure 1-16: Optimization Solution

These actions/recommendations are composed usually by changes of system parameters, physical parameters (Antennae) or even hardware changes. Therefore, it is important a good system knowledge by the Engineer.

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6.2

E-UTRAN Observability Observability covers all functions in the E-UTRAN that monitor and analyze the performance and characteristics of the network. This can be done on various levels with different target groups and requirements. The E-UTRAN Observability model is illustrated in Figure 1-17 below.

Key Performance Indicator (KPI) level

End-user Perception

Performance Indicator (PI) level

Procedure level System Characteristics Figure 1-17: EUTRAN Observability Model

The KPI represents the end-user perception of a network on a macro level. KPIs are of interest for an operator’s top-level management. KPI statistics are typically used to benchmark networks against each other and to detect problem areas. KPIs are calculated from PM counters. The reliability, granularity, and accuracy of the data are critical, and the data is collected continuously. As showed before, the network shall be optimized on KPI level in terms of Accessibility, Retainability, Integrity and Mobility, so that the end-user perception can be at its best. The PI represents information at the system level that explains the KPI results. The PI can also be in the form of metrics that show how specific parts of a system perform. PIs do not necessarily have an impact on KPIs. The PI data can be used for planning and dimensioning. This data, typically PM counters, is collected continuously. The Procedure level represents in-depth troubleshooting and measurement system characteristics. It involves measurements on signaling, and procedure and function levels to investigate problems detected at higher levels.

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The amount of data at the Procedure level is enormous and the measurements are generally user-initiated for a specific purpose and area of the network to limit the scope of the measurements. The typical source for this data is the UE Trace and the Cell Trace recording functions. Ericsson has specified KPI formulas to observe the areas of Accessibility, Retainability, Integrity, Mobility and Availability of the EUTRAN according to 3GPP TS32.450 and 32.451. These formulas can be found in the ‘Key Performance Indicators’ (37/1553-HSC 105 50/1) User Description in the LTE RAN Alex library as illustrated in Figure 1-18 below.

Figure 1-18: EUTRAN KPIs and PIs

The Operation and Maintenance/Performance Management folder also contains the ‘License and Resource Use Indicators’ (47/1553-HSC105 50/1) User Description which contains a number of licenses and system and processor load Performance Indicator formulas as illustrated in Figure 1-18 above. There are three separate LTE RAN Alex libraries for Ericsson Radio System Baseband, Digital Unit (DUL, DUS) and Pico RBSs. In this course we will use the Digital Unit (DU) library as illustrated in Figure 1-18 above.

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6.3

Optimization workflow As mentioned before, the whole Optimization process is a cyclic process aiming on enhancing the performance of each group of KPIs within the Observability Model. This process will stop once the desired values are reached and then maintained through a Performance Management routine. For each module, the process will be composed by: •

Collection of Performance Measurements;

•

Performance Analysis;

•

Recommendations / Implementation;

•

Verification

All of this is preceded by a Preparation phase, as shown in Figure 1-19 below.

Figure 1-19: Optimization Workflow

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During the Preparation phase a consistency check is performed to ensure that all design parameters are configured according to the network plan. Any errors corrected at this stage will have a big impact on the subsequent optimization modules. During this stage it should be ensured that the required statistics are being collected by the nodes and that all possible alarms are rectified. The cell availability KPI should also be closely monitored to ensure that all cells are active. Once the preparations have been completed the Optimization of each KPIs module (Accessibility, Retainability, Integrity, Mobility) can be performed. Each module will begin with the Collection of Performance Measurements where the network statistics are collected. The performance is measured using the relevant counters/indicators, then Performance Analysis is performed using network statistics, CTR, UETR, or in some cases drive test. Based on this analysis the Engineer has to come up with recommendations on how the performance can be improved. After the changes have been implemented they must be verified with network performance data. The whole process is repeated until the desired KPI values are reached.

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LTE L15 Performance Management and Optimization

7

E-UTRAN COUNTERS The EUTRAN counter name can be divided into five parts, or counter sub-names, as illustrated in Figure 1-20 below:

pm

Mandatory prefix to differentiate counters from other objects in the Managed Object Model (MOM).

Measurement Family

Describes the measurement level, for example, RRC, PDCP and so on.

Counter Specific

Describes the measurement for the counter and could be divided into three subparts, as follows: The Operation subpart is establishment, modification or termination The Reason/Result subpart is attempt, failure, success, throughput, volume and so on The Direction subpart is UL/DL or Incoming/Outgoing

Filter

Describes the filter that has been applied to the measure, for example Max (maximum)

Cause

Describes the cause for the reason or the result of the operation, for example, if the counter registers when an RRC message is deleted due to failed integrity check, the Cause sub-name would be Integrity.

Example: pmErabEstabSuccAdded This counter counts the total number of successfully added E-RABs per cell. Added E-RABs are all E-RABs present in the S1 message E-RAB Setup Request. Figure 1-20: EUTRAN Counter Name

7.1

E-UTRAN Counter types The counter types supported by the EUTRAN are listed below:

• Peg counter (PEG); • Gauge (GAUGE); • Accumulator counter (ACC); • Scan counter (SCAN); • Probability Density Function (PDF).

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7.1.1

Peg Counter A Peg counter is a counter that is increased by 1 at each occurrence of a specific activity. Figure 1-21 below illustrates the action of a peg counter called ‘pmGuestsIn’ that counts the number of guests in a hotel. In this example, each guest that enters the hotel will result in an increase of the count. Guests leaving will have no impact.

Figure 1-21: Peg Counter

In the illustration in Figure 1-21 above, at the end of the 15-minute ROP period, 7 people have come in (people leaving are not affecting the count), making pmGuestsIn = 7.

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LTE L15 Performance Management and Optimization

7.1.2

Gauge Counter A Gauge counter is a counter that can be increased or decreased depending on the activity in the system. Figure 1-22 below illustrates the action of a gauge counter called ‘pmGuestsInGauge’ that measures the number of guests in the hotel. In this example, each guest that enters the hotel will result in an increase of the count. Each guests leaving will result in a decrease of the count.

Figure 1-22: Gauge Counter

In the illustration in Figure 1-22 above, at the end of the 15-minute ROP period, 8 people came and 4 left, making pmGuestsInGauge = 4. Gauge counters are normally used to ‘remember’ a particular value during the ROP, for example the maximum number of guests that were in the hotel at one time instance during the ROP.

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7.1.3

Accumulator and Scan counters An Accumulator counter is increased by the value of a sample. It indicates the total sum of all sample values taken during a certain time. Figure 1-23 below illustrates the action of an accumulator counter called ‘pmSumSampGuests’ that accumulatively counts the number of guests in a hotel. In this example, as people come and go, there are three samples taken of 7, 9 and 11 people who are actually in the hotel at the sampling time, making a total of pmSumSampGuests = 27.

HOTEL ROLL

Average =

Count at end of ROP: Accumulator and Scan Accumulator counter: pmSumSampGuests=

27 16 0 7

Sample

Scan counter: pmNoOfSampGuests=

0 3 2 1

Sample

Accumulator 27 = =9 Scan 3

To OSS morning

afternoon

evening

Figure 1-23: Accumulator and Scan Counters

A Scan counter is a counter that is increased by 1 each time the corresponding Accumulator counter is increased. It indicates how many samples have been read, and added to the related Accumulator counter. A scan counter can therefore be considered a specific kind of Peg counter. Figure 1-23 above illustrates the action of a scan counter called pmNoOfSampGuests’ that accumulatively counts the number of guests in a hotel. In this example, as people come and go, there are three samples taken of people who are actually in at the time. Therefore the scan counter value will be pmNoOfSampGuests=3. The Accumulator and Scan counters can be used to calculate the average number of events during the ROP. In this example the average number of people in the hotel during the ROP is Accumulator/scan = 27/3 = 9 as illustrated in Figure 1-23 above.

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7.1.4

Probability Density Function (PDF) A Probability Density Function (PDF) counter is a list of range values. A value is read periodically. If the value falls within a certain range, the range counter for that range is increased. All range counter values are collected and stored in a ROP file at the end of each reporting period. Figure 1-24 below illustrates the action of a PDF counter. In this example the NoOfGuests values are split into three ranges: pmNoOfGuests1 = [0], pmNoOfGuests2 = [1-10], pmNoOfGuests3 = [11-25], and a value is read every 3 minutes over a 15-minute ROP period.

Figure 1-24: Probability Density Function

The values returned are 0, 7, 10, 17, 9, then the three range counters are reported as pmNoOfGuests1 = 1, pmNoOfGuests2 = 3, pmNoOfGuests3 = 1 as illustrated in Figure 1-24 above. In ENIQ, these counters will appear under one counter name, with a “Vector Index” column indicating which range the value belongs to. There will be as many rows returned as there are ranges. Some PDF counters are written in compressed format whereby only a small subset of the range is used. For example a PDF counter with 10 ranges could record the following during the ROP: 0, 0, 0, 0, 0, 3, 0, 0, 0, 22, 0 i.e. only a value of 3 for bin #5 and 22 for bin #9. When written in compressed form this would be: 2, 5, 3, 9, 22 where the first number is the number of reported bins followed by bin and bin value in pairs as illustrated in Figure 1-24 above.

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7.2

E-UTRAN Counter Examples Examples of all the E-UTRAN counter types with values for one ROP from a cell in a live Network are given in Figure 1-25 below. PEG: pmErabEstabAttInit The total number of initial E-RAB Establishment attempts. Example: 652 652 ERAB Establishment attempts GAUGE: pmErabMax The peak number of simultaneous E-RAB usage. A peak of 73 simultaneous ERABs Example: 73 ACC: pmErabLevSum The peak number of simultaneous E-RAB usage. Example: 7080

EUtranCellFDD eNodeBxx

SCAN: pmErabLevSamp Average number of Counts the number of times the corresponding ERABs = Sum counters has been incremented. 7080/180 = 39.33 Example: 180 Compressed: pmErabEstabAttInitQci PDF The total number of initial E-RAB setup attempts per QCI One attempt to establish a QCI 1 ERAB Example: 3,1,1,5,207,9,444 207 attempts to establish a QCI 5 ERAB 444 attempts to establish a QCI 9 ERAB Total = 1 + 207 + 444 = 652 Figure 1-25: Counter Type Examples

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7.3

E-UTRAN Counter Descriptions Searching the LTE RAN ALEX library for a counter name (pm…) will produce a hit in the Managed Object Model (MOM) showing the MO class of the counter. Clicking on the MO class will produce a description of the counter as illustrated in the example for the ‘pmUeCtxtRelMme’ in Figure 1-26 below which produces a hit in the ‘EUtranCellFDD’ and ‘EUtranCellTDD’ Managed Object (MO).

Figure 1-26: EUTRAN Counter Descriptions

The example in Figure 1-26 above the counter description in the MOM describes the ‘pmUeCtxtRelMme’ counter including the condition for which it is stepped and the counter type, in this case ‘PEG’. It also states that this counter is not included in any predefined scanner and is reset after the measurement period. For some counters a hit will also be produced in the ‘Flowcharts for Counters’ document as illustrated in the example in Figure 1-19 above. This document contains flowcharts for the main traffic sequences that impact Performance Statistics counters in the eNodeB. The same counter can be found in a TDD library as well.

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An example flow chart for MME Triggered UE Context Release is illustrated in Figure 1-27 below. UE context release is triggered by UE context release command

RBS

UE Context release command

MME

RBS

UE Context release complete

MME

pmUeCtxtRelMme +

No

Data in UL or DL buffer? Yes pmUeCtxtRelMmeAct +

End of UE context release Figure 1-27: MME Triggered UE Context Release

The example flow chart in Figure 1-27 above shows how the ‘pmUeCtxtRelMme’ counter (and ‘pmUeCtxtRelMmeAct’) is triggered. The ‘Flowcharts for Counters’ document may be used in conjunction with the counter description from the MOM to fully explain the action of an eNodeB counter. Note that not all E-UTRAN counters are used in flow charts.

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LTE L15 Performance Management and Optimization

8

SUMMARY The participants should now be able to: 1. Explain the E-UTRAN Performance Management solution 1.1 Explain the E-UTRAN Optimization Solution 1.2 Describe how eNodeB counters are collected and stored 1.3 Describe the eNodeB counter types and structures 1.4 Explain briefly Quality of Service concepts in EPS Figure 1-28: Summary of Chapter 1

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2 LTE Accessibility Optimization

Objectives After completion of this chapter the participants will be able to: 2. Measure LTE Accessibility performance 2.1 Describe the Random Access procedure 2.2 Describe the E-RAB setup procedure and associated counters 2.3 Use eNodeB counters to create E-RAB Accessibility KPIs 2.4 Explain the eNodeB parameters and features that influence Accessibility Figure 2-1: Objectives of Chapter 2

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1

RANDOM ACCESS PROCEDURE Before the initial E-RAB setup procedure takes place it is important to understand the Random Access procedure that is necessary before the initial ERAB is established. The Random Access procedure is also used whenever the need of uplink time synchronization is also identified. The RA process allows multiple UEs using different RA preamble codes to gain simultaneous access to a cell. The RA preamble codes are transmitted in uplink on the PRACH. The preamble codes exhibit very good cross correlation properties, which allows the RBS to detect multiple RA preambles on the same PRACH occasion. There are two different forms of the random access process, Contention Based Random Access (CBRA) and Contention Free Random Access (CFRA). Contention Based Random Access (CBRA) is used by the UE for the initial ERAB establishment process. It involves the UE selecting a random access preamble code from a list of codes available for selection by all UE in the cell. CBRA requires additional signaling to resolve contention that may occur when multiple UE attempts to access the cell in the same PRACH subframe using the same preamble code. The Contention Free Random Access (CFRA) process is enabled by setting the ‘cfraEnable’ parameter to ‘TRUE’. When enabled, a portion of random access preambles should be allocated for CFRA and will be used for incoming handover and PDCCH ordered uplink re-sync. The CFRA process involves three phases and uses a preamble code dedicated to one UE to increase the probability of success of the random access process, leading to faster cell access. CBRA can also be initiated by the network. It is out of scope of this course to explain in detail the RA procedure. Therefore it will be explained only the aspects related to the system performance such as the flow of the procedure focused on the transmission of the preamble and the response; as well as the Open Loop Power Control that will define the initial power of the RA preamble to be sent.

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There are a number of stages involved in the random access process. Two of these stages are common to both the CFRA and the CBRA processes. Figure 2-2 below shows a flow diagram of the random access process and identifies the stages used in the CFRA and CBRA processes.

RA Preamble Assignment

1

Random Access Preamble Random Access Response

CBRA Used for initial E-RAB establishment process.

3

0

2

ManagedElement +-ENodeBFunction +-EUtranCellFDD cfraEnable = TRUE CFRA Used for incoming handover and PDCCH ordered uplink re-sync.

Scheduled Transmission (MSG3) HARQ

Contention Resolution (MSG4) HARQ

4

Figure 2-2: Random Access Procedure

The first step in the CFRA process is the assignment of a dedicated preamble code sequence to the UE. This is shown as step 0 in Figure 2-2 above. Each LTE cell reserves a number of preamble codes for CFRA. Pre assignment of the preamble sequence by the network makes the random access process faster as there is no need for contention resolution. The preamble code required for the random access is sent to the UE by the serving cell. The random access preamble transmission and random access response steps are common to both CFRA and CBRA processes. They are shown as step 1 and step 2 respectively in Figure 2-2 above. The UE transmits random access preamble bursts on the PRACH uplink channel. The network provides information about the PRACH to UE in a system information message. This allows the UE to determine when the PRACH channels are scheduled and the preamble format and code sequence to use. The random access transmission process uses open loop power control. The UE estimates the transmit power required to achieve a specified receive power for the first random access burst. Power ramping is used for subsequent retransmission bursts if they are required. This process continues until the UE successfully receives a response from the RBS, or the maximum number of retransmission attempts is reached.

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LTE L15 Performance Management and Optimization

The random access response message is generated by the RBS and transmitted on the Physical Downlink Shared Channel (PDSCH) to a specific Random Access Radio Network Temporary Identity (RA-RNTI) address. More than one RARNTI address can be included in this message, allowing the setup of random access attempts from multiple UEs in the same PRACH sub frame. The aim of initial random access open loop power control in the uplink is to ensure new connections are established causing minimum interference. The three basic steps employed are shown in Figure 2-3 below.

preambleInitialReceivedTargetPower = -110 { -120..-90 } [Unit: 1 dBm] PREAMBLE _ RECEIVED _ TARGET _ POWER ? preambleInitial Re ceivedT arg etPower - F PREAMBLE -

*PREAMBLE _ TRANSMISSION _ COUNTER - 1+ Ú powerRampingStep

1) UE measures RS

3) The power is ramped up until a response is heard or maximum number of re-attempts is reached

Connection established with minimum interference to other cells

Figure 2-3: Uplink Open Loop Power Control

Open Loop Power Control is used in the uplink to minimize uplink interference when setting up a connection. The EutranCell MO ‘preambleInitialReceivedTargetPower’ parameter illustrated in Figure 2-3 above controls the value of preambleInitialReceivedTargetPower used by the UE.

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1.1

Contention Based Random Access Success Rate The equation illustrated in Figure 2-4 below can provide an approximate indication of the Contention Based Random Access Success Rate.

pmRaSuccCbra The number of successfully detected RA Msg3 for CBRA pmRaAttCbra The number of detected contention-based random access preambles pmRaUnassignedCfraFalse The number of detected Contention Free Random Access preambles that are not allocated to any UE pmRaUnassignedCfraSum The total number of unassigned Contention Free Random Access preambles at each PRACH occasion during the reporting period. pmRaFailCbraMsg2Disc The number of CBRA preambles for which no random access response (RA Msg2) was sent due to expiration of the random access response window. pmRaFailCbraMsg1DiscSched The number of CBRA preambles that are discarded because maximum number of RA Msg3 are already scheduled. pmRaFailCbraMsg1DiscOoc The number of CBRA preambles that are discarded because timing offset of CBRA preamble corresponds to a distance greater than configured cell range. Figure 2-4: Contention Based Random Access Success Rate

It should be noted that the equation in Figure 2-4 above may not be accurate since it estimates the amount of detected preambles and assumes that a detected preamble is a random access attempt. Poor Random Access Success Rate may be due to many factors, including overshooting cell, high uplink interference or poor RACH Root Sequence planning.

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1.2

Overshooting Cell The ‘cellRange’ parameter illustrated in Figure 2-5 below defines the maximum distance from the base station where a connection to a UE can be setup and/or maintained.

cellRange

X

ManagedElement +-ENodeBFunction +-EUtranCellFDD cellRange = 15 { 1..100 } [Unit: 1 km]

pmRaFailCbraMsg1DiscOoc Incremented for each preamble that is discarded because it was detected from a UE outside the configured cell range. The ‘Maximum Cell Range’ (FAJ 121 0869) optional feature is required to support cell ranges >15 km. Figure 2-5: Overshooting Cell

The ‘pmRaFailCbraMsg1DiscOoc’ parameter illustrated in Figure 2-5 above is incremented for each preamble that is discarded because it was detected from a UE outside the configured cell range. This counter can be used to identify an overshooting cell. Prior to L15 this counter was called ‘pmZtemporary66’. If the ‘Enhanced Cell ID in Traces’ (FAJ 121 2025) optional feature is active the ‘INTERNAL_PER_RADIO_UE_MEASUREMENT_TA’ Cell Trace event can be used to give an indication of the distance of a UE to an antenna. More information on this is given in the LTE Cell and UE Trace chapter. If a cell range greater than 15 km is required the ‘Maximum Cell Range’ (FAJ 121 0869) optional feature which supports a maximum cell range of 100 km may be used. The feature includes use of the random access preamble format 1 that is appropriate for the large round trip times in cells with cell range larger than 15 km.

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1.3

Uplink Interference The ‘pmRadioRecInterferencePwr’ PDF counter illustrated in Figure 2-6 below gives the measured Noise and Interference Power on the PUSCH according to 3GPP technical specification 36.214. This counter can be used to identify if a cell has high uplink interference which can be the cause of poor Random Access Success Rate.

pmRadioRecInterferencePwr: 0,139,457290,272646,84684,33072,17023,11251,8475,3359,10791,1112,146,12,0,0 pmRadioRecInterferencePwr

Low Interference

pmRadioRecInterferencePwr: 0,0,0,0,0,0,0,0,0,0,0,0,0,0,585400,314600

High Interference

The measured Noise and Interference Power on PUSCH, according to 36.214 PDF ranges: [0]: N+I