LTE Optimization Engineering Handbook

XINCHENG ZHANG is a Professor and Engineer with more than 20 years' experience in wireless communications and is a technical expert for one of China's largest telecom companies, China Mobile Group Design Institute Co., Ltd.

• About the Author xviPreface xviiPart 1 LTE Basics and Optimization Overview 11 LTE Basement 31.1 LTE Principle 31.1.1 LTE Architecture 61.1.2 LTE Network Interfaces 71.2 LTE Services 111.2.1 Circuit]Switched Fallback 121.2.2 Voice over LTE 131.2.3 IMS Centralized Services 161.2.4 Over the Top Solutions 161.2.5 SMS Alternatives over LTE 171.2.6 Converged Communication 191.3 LTE Key Technology Overview 191.3.1 Orthogonal Frequency Division Multiplexing 201.3.2 MIMO 211.3.3 Radio Resource Management 222 LTE Optimization Principle and Method 242.1 LTEWireless Optimization Overview 242.1.1 Why LTE Wireless Optimization 242.1.2 Characters of LTE Optimization 242.1.3 LTE Joint Optimization with 2G/3G 252.1.4 Optimization Target 252.2 LTE Optimization Procedure 262.2.1 Optimization Procedure Overview 262.2.2 Collection of Mass Nerwork Measurement Data 282.2.3 Measurement Report Data Analysis 302.2.4 Signaling Data Analysis 312.2.5 UE Positioning 322.2.5.1 Timing Advance 332.2.5.2 Location Accuracy Evaluation 352.2.5.3 Location Support 362.2.5.4 3D Geolocation 372.2.6 Key Performance Indicators Optimization 422.2.7 Technology Evolution of Optimization 432.3 LTE Optimization Key Point 442.3.1 RF Optimization 442.3.1.1 RSRP/RSSI/SINR/CINR 442.3.1.2 External Interference 482.3.2 CQI versus RSRP and SINR 512.3.2.1 CQI Adjustment 512.3.2.2 SINR Versus Load 542.3.2.3 SINR Versus MCS 562.3.3 Channel Power Configuration 582.3.3.1 RE Power 582.3.3.2 CRS Power Boosting 642.3.3.3 Power Allocation Optimization 662.3.4 Link Adaption 672.3.5 Adaptive Modulation and Coding 692.3.6 Scheduler 702.3.6.1 Downlink Scheduler 722.3.6.2 Uplink Scheduler 742.3.7 Radio Frame 752.3.8 System Information and Timers 762.3.8.1 System Information 762.3.8.2 Timers 812.3.9 Random Access 832.3.10 Radio Admission Control 852.3.11 Paging Control 862.3.11.1 Paging 862.3.11.2 Paging Capacity 922.3.11.3 Paging Message Size 952.3.11.4 Smart Paging 952.3.11.5 Priority Paging 962.3.12 MIMO and Beamforming 972.3.12.1 Basic Multi]Antenna Techniques 1002.3.12.2 2D]Beamforming 1012.3.12.3 2D MIMO and Parameters 1042.3.12.4 Massive]MIMO 1052.3.13 Power Control 1072.3.13.1 PUSCH/PUCCH Power Control 1072.3.13.2 PRACH Power Control 1092.3.14 Antenna Adjustment 1112.3.14.1 Antenna Position 1122.3.14.2 Remote Electrical Tilt 1132.3.14.3 Antenna Azimuths and Tilts Optimization 1172.3.14.4 VSWR Troubleshooting 1182.3.15 Main Key Performance Indicators 120Part 2 Main Principles of LTE Optimization 1233 Coverage Optimization 1253.1 Traffic Channel Coverage 1253.1.1 Parameters of Coverage 1263.1.2 Weak Coverage 1283.1.2.1 DL Coverage Hole 1283.1.2.2 UL Weak Coverage 1283.1.2.3 UL and DL Imbalance 1293.1.3 Overlapping Coverage 1293.1.4 Overshooting 1303.1.5 Tx1/Tx2 RSRP Imbalance 1323.1.6 Extended Coverage 1323.1.7 Cell Border Adjustment 1353.1.8 Vertical Coverage 1373.1.9 Parameters Impacting Coverage 1383.2 ControlChannel Coverage 1384 Capacity Optimization 1404.1 RS SINR 1404.2 PDCCHCapacity 1414.3 PUCCH Capacity 1444.3.1 Factors Affecting PUCCH Capacity 1454.3.2 PUCCH Dimensioning Example 1514.4 Number of Scheduled UEs 1524.5 Spectral Efficiency 1534.6 DLData Rate Optimization 1544.6.1 Limitation Factor 1564.6.2 Model of DL Data Throughput 1574.6.3 UDP/TCP Protocol 1584.6.4 MIMO 1614.6.4.1 DL MIMO 1614.6.4.2 4Tx/4Rx Performance 1634.6.4.3 Transmission Mode Switch 1634.6.4.4 UL MU]MIMO 1644.6.5 DL PRB Allocation and Utilization Mechanism 1654.6.6 DL BLER 1674.6.7 Impact of UE Velocity 1694.6.8 Single User Throughput Optimization 1704.6.8.1 Radio Analysis – Assignable Bits 1714.6.8.2 Radio Analysis – CFI and Scheduling 1714.6.8.3 Radio Analysis – HARQ 1714.6.9 Avarage Cell Throughput Optimization 1724.6.10 Cell Edge Throughput Optimization 1724.6.11 Some Issues of DL Throughput 1734.6.11.1 Antenna Diversity not Balanced 1734.6.11.2 DL Grant is not Enough 1734.6.11.3 Unstable Rate 1754.7 UL Data Rate Optimization 1754.7.1 Model of UL Data Throughput 1764.7.2 UL SINR and PUSCH Data Rate 1764.7.3 PRB Stretching and Throughput 1794.7.4 Single User Throughput Optimization 1804.7.4.1 Radio Analysis – Available PRBs 1814.7.4.2 Radio Analysis—Link Adaptation 1814.7.4.3 Radio Analysis – PDCCH 1824.7.5 Cell Avarage and Cell]edge Throughput Optimization 1824.7.6 Some Issues of UL Throughput 1834.8 Parameters Impacting Throughput 1855 Internal Interference Optimization 1885.1 Interference Concept 1885.2 DLInterference 1905.2.1 DL Interference Ratio 1915.2.2 Balance Between SINR and RSRP 1925.3 UL Interference 1925.3.1 UL Interference Detection 1945.3.2 Generation of UL Interference 1965.3.2.1 Cell Loading Versus Inter]Cell Interference 1965.3.2.2 Unreasonable UL Network Structure 1975.3.2.3 Cross slot interference 1995.3.3 PUSCH Tx Power Analysis 2005.3.4 UL Effect of P0 and α 2025.3.5 PRACH Power Control 2045.3.6 SRS Power Control 2065.3.7 Interference Rejection Combinin 2095.4 Inter]Cell Interference Coordination 2105.5 UL IoT Control 2105.5.1 UL Interference Issues and Possible Solutions 2105.5.2 UL IoT Control Mechanism 2105.5.3 PUSCH UL_SINR Target Calculation 2125.5.4 UL Interference Criteria 2136 Drop Call Optimization 2166.1 Drop Call Mechanism 2166.1.1 Radio Link Failure Detection by UE 2176.1.2 RadioLink Failure Detection by eNB 2206.1.2.1 Link Monitors in eNB 2206.1.2.2 Time Alignment Mechanism 2216.1.2.3 Maximum RLC Retransmissions Exceeded 2246.1.3 RadioLink Failure Optimization and Recovery 2256.2 Reasons of Call Drop and Optimization 2276.2.1 Reasons of E]RAB Drop 2276.2.2 S1 Release 2306.2.3 Retainability Optimization 2336.3 RRC Connection Reestablishment 2336.4 RRC Connection Supervision 2397 Latency Optimization 2447.1 User Plane Latency 2447.2 Control Plane Latency 2477.3 Random Access Latency Optimization 2477.4 Attach Latency Optimization 2487.5 Paging Latency Optimization 2507.6 Parameters Impacting Latency 2508 Mobility Optimization 2548.1 Mobility Management 2558.1.1 RRC Connection Management 2568.1.2 Measurement and Handover Events 2568.1.3 Handover Procedure 2608.1.3.1 X2 Handover 2618.1.3.2 S1 Handover 2678.1.3.3 Key point of X2/S1 Handover 2678.2 Mobility Parameter 2698.2.1 Attach and Dettach 2728.2.2 UE Measurement Criterion in Idle Mode and Cell Selection 2738.2.3 Cell Priority 2768.3 Intra]LTE Cell Reselection 2768.3.1 Cell Reselection Procedure 2788.3.2 Inter]Frequency Cell Reselection 2798.3.3 Cell Reselection Parameters 2828.3.4 Inter]Frequency Reselection Optimization 2838.4 Intra]LTE Handover Optimization 2858.4.1 A3 and A5 Handover 2858.4.2 Data Forwarding 2908.4.3 Intra]Frequency Handover Optimization 2918.4.4 Inter]Frequency Handover Optimization 2928.4.5 Timers for Handover Failures 2968.5 Neighbor Cell Optimization 2978.5.1 Intra]LTE Neighbor Cell Optimization 2978.5.1.1 Neighbor Relations Table 2978.5.1.2 ANR 2988.5.2 Suitable Neighbors for Load Balancing 2998.6 Measurement Gap 2998.6.1 Measurement Gap Pattern 2998.6.2 Measurement Gap Versus Period of CQI Report and DRX 3048.6.3 Impact of Throughput on Measurement Gap 3048.7 Indoor and Outdoor Mobility 3058.8 Inter]RAT Mobility 3068.8.1 Inter]RAT Mobility Architecture and Key Technology 3078.8.2 LTE to G/U Strategy 3098.8.3 Reselection Optimization 3148.8.3.1 LTE to UTRAN 3158.8.3.2 UTRAN to LTE 3198.8.4 Redirection Optimization 3208.8.4.1 LTE to UTRAN 3208.8.4.2 UTRAN to LTE 3228.8.5 PS Handover Optimization 3228.8.5.1 LTE to UTRAN 3228.8.5.2 UTRAN to LTE 3248.8.6 Reselection and Redirection Latency 3258.8.7 Optimization Case Study 3268.9 Handover Interruption Time Optimization 3268.9.1 Control Plane and User Plane Latency 3298.9.2 Inter]RAT Mobility Latency 3328.10 Handover Failure and Improvement 3328.11 Mobility Robustness Optimization 3358.12 Carrier Aggregation Mobility Optimization 3418.13 FDD]TDD Inter]mode Mobility Optimization 3458.14 Load Balance 3468.14.1 Inter]Frequency Load Balance 3468.14.2 Inter]RAT Load Balance 3488.14.3 Load Based Idle Mode Mobility 3498.15 High]Speed Mobile Optimization 3518.15.1 High]Speed Mobile Feature 3538.15.2 Speed]Dependent Cell Reselection 3548.15.3 PRACH Issues 3568.15.4 Solution for Air to Ground 3589 Traffic Model of Smartphone and Optimization 3609.1 Traffic Model of Smartphone 3609.1.1 QoS Mechanism 3629.1.2 Rate Shaping and Traffic Management 3669.1.3 Traffic Model 3719.2 Smartphone]Based Optimization 3729.3 High]Traffic Scenario Optimization 3729.3.1 Resource Configuration 3749.3.2 Capacity Monitoring 3759.3.3 Special Features and Parameters for High Traffic 3779.3.4 UL Noise Rise 3799.3.5 Offload Solution and Parameter Settings 379Part III Voice Optimization of LTE 38310 Circuit Switched Fallback Optimization 38510.1 Voice Evolution 38510.2 CSFB Network Architecture and Configuration 38610.2.1 CSFB Architecture 38610.2.2 Combined Register 38710.2.3 CSFB Call Procedure 39210.2.3.1 Fallback Options 39210.2.3.2 RRC Release with Redirection 39310.2.3.3 CSFB Call Procedure 39510.2.4 Mismatch Between TA and LA 39710.3 CSFB Performance Optimization 40210.3.1 CSFB Optimization 40210.3.1.1 Main Issues of CSFB 40210.3.1.2 CSFB Optimization Method 40310.3.2 CSFB Main KPI 40710.3.3 Fallback RAT Frequency Configuration Optimization 40910.3.4 Call Setup Time Latency Optimization 41110.3.4.1 ESR to Redirection Optimization 41610.3.4.2 Twice Paging 41610.3.5 Data Interruption Time 41810.3.6 Return to LTE After Call Complete 41910.4 Short Message Over CSFB 42210.5 Case Study of CSFB Optimization 42310.5.1 Combined TA/LA Updating Issue 42310.5.2 MTRF Issue 42510.5.3 Track Area Update Reject After CSFB 42510.5.3.1 No EPS Bearer Context Issue 42810.5.3.2 Implicitly Detach Issue 42810.5.3.3 MS Identity Issue 42810.5.4 Pseudo Base Station 42811 VoLTE Optimization 43411.1 VoLTE Architecture and Protocol Stack 43511.1.1 VoLTE Architecture 43511.1.2 VoLTE Protocol Stack 43511.1.3 VoLTE Technical Summary 43811.1.4 VoLTE Capability in UE 43911.2 VoIP/Video QoS and Features 44211.2.1 VoIP/Video QoS 44211.2.2 Voice Codec 44411.2.3 Video Codec 44611.2.4 Radio Bearer for VoLTE 44911.2.5 RLC UM 45411.2.6 Call Procedure 45711.2.6.1 LTE Attach and IMS Register 45811.2.6.2 E2E IMS Flow 45811.2.6.3 Video Phone Session Handling 46211.2.7 Multiple Bearers Setup and Release 46611.2.8 VoLTE Call On]Hold/Call Waiting 46711.2.9 Differentiated Paging Priority 46811.2.10 Robust Header Compression 47011.2.10.1 RoHC Feature 47011.2.10.2 Gain by RoHC 47011.2.11 Inter]eNB Uplink CoMP for VoLTE 47511.3 Semi]Persistent Scheduling and Other Scheduling Methods 47711.3.1 SPS Scheduling 47711.3.2 SPS Link Adaptation 47811.3.3 Delay Based Scheduling 48111.3.4 Pre]scheduling 48211.4 PRB and MCS Selection Mechanism 48411.4.1 Optimized Segmentation 48411.4.2 PRB and MCS Selection 48511.5 VoLTE Capacity 48611.5.1 Control Channel for VoLTE 48711.5.2 Performance of Mixed VoIP and Data 48811.6 VoLTE Coverage 49111.6.1 VoIP Payload and RoHC 49211.6.2 RLC Segmentation 49211.6.3 TTI Bundling 49811.6.4 TTI Bundling Optimization 50211.6.5 Coverage Gain with RLC Segmentation and TTI Bundling 50711.6.6 MCS/TBS/PRB Selection 50911.6.7 Link Budget 51011.7 VoLTE Delay 51311.7.1 Call Setup Delay 51611.7.1.1 Call Setup Time 51611.7.1.2 Reasons for Long Call Setup Time 51611.7.2 Conversation Start Delay 51911.7.3 RTP Delay 52111.7.4 Handover Delay and Optimization 52511.8 Intra]LTE Handover and eSRVCC 52711.8.1 Intra]Frequency Handover 52711.8.2 Inter]Frequency Handover 52811.8.3 Single Radio Voice Call Continuity Procedure 52911.8.4 SRVCC Parameters Optimization 53911.8.4.1 Handover Parameters 53911.8.4.2 SRVCC–Related Timer 53911.8.5 aSRVCC and bSRVCC 54311.8.6 SRVCC Failure 54311.8.7 Reducing SRVCC Voice Gap and eSRVCC 54511.8.7.1 Voice Interruption Time during SRVCC 54511.8.7.2 eSRVCC 54911.8.8 Fast Return to LTE 55211.8.9 Roaming Behavior According to Network Capabilities 55511.9 Network Quality and Subjective Speech Quality 55511.9.1 Bearer Latency 55811.9.2 MoS 56111.9.2.1 Voice Quality 56111.9.2.2 Video Quality 57011.9.3 Jitter 57111.9.4 Packet Loss 57211.9.5 One Way Audio 57511.9.6 PDCP Discard Timer Operation 57611.10 Optimization 57711.10.1 Distribution of Main Indicators of Field Test 58011.10.2 Compression Ratio and GBR Throughput 58411.10.3 RB Utilization 58411.10.4 BLER Issue 58711.10.5 Quality Due to Handover 58911.10.6 eSRVCC Handover Issues 58911.10.7 Packet Loss 59211.10.7.1 Packet Loss due to Poor RF 59211.10.7.2 Packet Loss due to Massive users 59211.10.7.3 Packet Loss Due to Insufficient UL grant 59211.10.7.4 Packet Loss due to Handover 60111.10.7.5 Packet Loss Due to Network Issue 60111.10.8 Call Setup Issues 60111.10.8.1 Missed Pages 60211.10.8.2 IMS Issues 60411.10.8.3 Dedicated Bearer Setup Issues 60911.10.8.4 CSFB Call Issues 61211.10.8.5 aSRVCC Failure 61211.10.8.6 RF Issues 61211.10.8.7 Frequent TFT Updates 61711.10.8.8 Encryption Issue 61811.10.9 Call Drop 61911.10.9.1 Call Drop 61911.10.9.2 Radio Link Failure 62211.10.9.3 RTP]RTCP Timeout 62411.10.9.4 RLC/PDCP SN Length Mismatch 62611.10.9.5 IMS Session Drop 62611.10.9.6 eNB/MME Initiated Drop 63211.10.10 Packet Aggregation Level 63211.10.11 VoIP Padding 63311.10.12 VoIP Ralated Parameters 63511.10.13 Video]Related Optimization 63511.10.13.1 Video Bit Rate and Frame Rate 63711.10.13.2 Video MoS and Audio/Video Sync 63711.10.14 IMS Ralated Timer 63711.11 UE Battery Consumption Optimization for VoLTE 63811.11.1 Connected Mode DRX Parameter 64311.11.2 DRX Optimization 64411.11.2.1 State Estimation 64411.11.2.2 DRX Optimization and Parameters 64411.11.2.3 KPI Impacts with DRX 64811.11.3 Scheduling Request Periodicity and Disabling of Aperiodic CQI 65211.12 Comparation with VoLTE and OTT 65411.12.1 OTT VoIP User Experience 65411.12.2 OTT VoIP Codec 65711.12.3 Signaling Load of OTT VoIP 658Part IV Advanced Optimization of LTE 66312 PRACH Optimization 66512.1 Overview 66512.2 PRACH Configuration Index 66912.3 RACH Root Sequence 67312.4 PRACH Cyclic Shift 67412.4.1 PRACH Cyclic Shift Optimization 67412.4.2 Rrestricted Set 67912.5 Prach Frequency Offset 68212.6 Preamble Collision Probability 68312.7 Preamble Power 68412.8 Random Access Issues 68712.9 RACH Message Optimization 68912.10 Accessibility Optimization 69212.10.1 Reasons for Poor Accessibility 69212.10.2 Accessibility 69312.10.3 Accessibility Analysis Tree 69512.10.4 Call and Data Session Setup Optimization 69712.10.5 RACH Estimation for Different Traffic Profile 69813 Physical Cell ID Optimization 70213.1 Overview 70213.2 PCI Optimization Methodology 70313.2.1 PCI Group Optimization 70513.2.2 PCI Code Reuse Distance 70513.2.3 Mod3/30 Discrepancy Analysis 70813.2.4 Collision and Confusion 70813.3 PCI Optimization 70914 Tracking Areas Optimization 71114.1 TA Optimization 71214.1.1 TA Update Procedure 71314.1.2 TA Optimization and TAU Failure 71514.2 TA List Optimization 71614.3 TAU Reject Analysis and Optimization 71915 Uplink Signal Optimization 72115.1 Uplink Reference Signal Optimization 72115.1.1 Coding Scheme of UL RS 72215.1.2 Correlation of UL Sequence Group 72315.1.2.1 UL Sequence Group Hopping 72515.1.2.2 UL Sequence Hopping 72615.1.2.3 UL Cyclic Shift Hopping 72615.1.3 UL Sequence Group Optimization 72715.2 Uplink Sounding Signal Optimization 72915.2.1 SRS Characters 73015.2.2 Wideband SRS Coverage 73615.2.3 Dynamic SRS Adjustment Scheme 73615.2.4 SRS Selection Dimension and Confliction 73715.2.5 SRS Conflict and Optimization 73916 HetNet Optimization 74116.1 UE Geolocation and Identification of Traffic Hot Spots 74116.2 Wave Propagation Characteristics for HetNet 74516.3 New Features in HetNet 74616.4 Combined Cell Optimization 74716.5 Cell Range Expansion Offset 74816.6 HetNet Cell Reselection and Handover Optimization 75117 QoE Evaluation and Optimization Strategy 75217.1 QoE Modeling 75317.2 Data Collecting and Processing 75617.3 QoE]Based Traffic Evaluation 75717.3.1 Online Video QoE 75717.3.1.1 Video Quality Monitoring Methods 76117.3.1.2 RATE Adaptive Video Codecs 76317.3.1.3 Streaming KPI and QoE 76417.3.1.4 Video Optimization 76617.3.2 Voice QoE 76917.3.3 Data Service QoE 77017.3.3.1 Web browsing 77017.3.3.2 Online Gaming 77417.4 QoE Based Optimization 77618 Signaling]Based Optimization 78018.1 S1] AP Signaling 78018.1.1 NAS signaling 78218.1.2 Inactivity Supervision 78318.1.3 UE signaling Management 78518.2 Signaling radio bearers 78618.3 Signaling Storm 78818.4 Signaling Troubleshooting Method 78818.4.1 Attach Failure 78818.4.2 Service Request Failure 79618.4.3 S1/X2]Based Handover 79618.4.4 eSRVCC Failure 79818.4.5 CSFB Failure 800Appendix 802Glossary of Acronyms 820References 823Index 825