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DESIGN AND IMPLEMENTATION OF MIMO-LONG TERM
EVOLUTION-ADVANCED TO SUPPORT LARGER BANDWIDTH
AWS ZUHEER YONIS ALASHQER
A thesis submitted in
fulfillment of the requirement for the award of the
Doctor of Philosophy
Faculty of Electrical and Electronic Engineering
Universiti Tun Hussein Onn Malaysia
2013
VI
ABSTRACT
The migration of mobile communication technologies are divided into four generations.
Long Term Evolution (LTE) is called LTE rel-8, the evolution of LTE led to new
technology referred to as LTE-Advanced, is the true fourth generation (4G) evolution
step, with the first release of LTE (rel-8) which was labeled as “3.9G”. LTE-Advanced
is a mobile broadband access technology founded as a response to the need for the
improvement to support the increasing demand for high data rates. The standard for
LTE-A is a milestone in the development of Third Generation Partnership Project
(3GPP) technologies. Carrier Aggregation is one of the most distinct features of LTE-
Advanced that makes the bandwidth extension of up to 100 MHz thus the theoretical
peak data rate of LTE-A may be even up to 1 Gbps. This proposed system presents new
LTE-Advanced depending on carrier aggregation to obtain better performance of the
system. The new design of LTE-Advanced offers higher peak data rates than even the
initial LTE-A; while the spectrum efficiency has been amended; As a result, the
aggregated LTE-A will support 120 MHz instead of 100 MHz in order to obtain higher
peak data rate access up to 4 Gbps. The system was applied with 8x8 Multiple Input
Multiple Output (MIMO) using different modulation techniques: QPSK, 16 QAM, and
64 QAM. From the simulation results, it is clear that proposed LTE-Advanced with 64
QAM has high values of throughput in case of depending code rate equals to 5/6 with
8x8 MIMO.
VII
ABSTRAK
Penghijrahan teknologi komunikasi mudah alih dibahagikan kepada empat generasi.
Long Term Evolution (LTE) dipanggil LTE rel-8, evolusi LTE yang membawa kepada
teknologi baru yang dikenali sebagai LTE-Lanjutan, adalah generasi yang benar-benar
evolusi generasi keempat (4G), dengan keluaran pertama LTE (rel-8) yang dilabelkan
sebagai "3.9G". LTE-Lanjutan adalah teknologi akses komunikasi mudah alih jalur lebar
yang ditubuhkan untuk menjawab kepada keperluan permintaan yang semakin
meningkat bagi kadar data yang tinggi. Standard untuk LTE-A adalah peristiwa penting
dalam pembangunan teknologi generasi ketiga Partnership Project (3GPP).
Penggabungan Carrier merupakan salah satu ciri yang paling ketara dalam LTE-
Advanced yang membenarkan sambungan jalur lebar sehingga 100 MHz, oleh itu secara
theoretical puncak kadar data LTE-A mungkin melebihi 1 Gbps. Sistem yang
dicadangkan membuka lebaran baru LTE-Advanced namun demikian ia bergantung
kepada penggabungan carrier untuk menghasilkan prestasi yang lebih baik daripada
sistem. Reka bentuk baru LTE-Advanced menawarkan kadar data puncak yang lebih
tinggi daripada permulaan LTE-A, manakala kecekapan spektrum telah dipinda; Secara
kesimpulan, penggabungan LTE-A akan menyokong 120 MHz dan bukannya 100 MHz
untuk mendapatkan kadar data puncak yang boleh mengakses sehingga 4 Gbps. Sistem
ini telah diaplikasikan dengan 8x8 Pelbagai Input Pelbagai Output (MIMO) dengan
menggunakan pelbagai teknik modulasi yang berbeza: QPSK, 16 QAM, dan 64 QAM.
Daripada keputusan simulasi, ia jelas menunjukkan bahawa cadangan LTE-Advanced
dengan 64 QAM mempunyai nilai-nilai yang tinggi pemprosesan dalam kes bergantung
kadar kod sama dengan 5/6 dengan 8x8 MIMO.
VIII
TABLE OF CONTENTS
TITLE I
DECLARATION III
ACKNOWLEDGEMENT V
ABSTRACT VI
TABLE OF CONTENTS VIII
LIST OF FIGURES XIII
LIST OF TABLES XVII
LIST OF PUBLICATIONS AND AWARDS XIX
LIST OF ABBREVIATIONS
XXIII
CHAPTER 1 INTRODUCTION 1
1.1 Problem Statement 2
1.2 Objectives of the Research 3
1.3 Scope of the Research 3
1.4 Contributions of the Research 4
1.5 Outline of The Thesis 4
IX
CHAPTER 2 LTE AND LTE-ADVANVACED 6
2.1 Introduction 6
2.2 System Requirements for LTE and LTE-Advanced 9
2.3 Long Term Evolution Standard 11
2.4 Key Enabling Technologies and Feature of LTE 12
2.4.1 Downlink of Long Term Evolution 13
2.4.2 Uplink of Long Term Evolution 24
2.5 Long Term Evolution-Advanced Standard 26
2.5.1 Carrier Aggregation 27
2.5.2 Peak Data Rates and Throughput 29
2.5.3 Peak Spectral Efficiency 31
2.5.4 Mobility 34
2.5.5 Latency 35
2.6 LTE-Advanced Technologies 35
2.6.1 Multiple Input Multiple Output (MIMO) 36
2.6.2 Coordinated Multi-Point transmission (CoMP) 39
2.6.3 Relaying 40
2.7 Summary
42
X
CHAPTER 3 Carrier Aggregation for LTE-Advanced 43
3.1 Introduction 43
3.2 Carrier Aggregation Schemes in LTE and LTE-Advanced 44
3.2.1 Intra-band Aggregation with Contiguous Component
Carriers
52
3.2.2 Intra-band Aggregation with non-Contiguous Component
Carriers
52
3.2.3 Inter-Band Aggregation with non-Contiguous
Component Carriers
54
3.3 Band Combinations for LTE-CA 61
3.4 Summary
64
CHAPTER 4 Methodology 65
4.1 Introduction 65
4.2 MIMO Physical Downlink of LTE-A System 66
4.3 Design of the Carrier Aggregation in LTE-Advanced
System
70
4.4 Design of the Proposed LTE-Advanced System 72
4.5 MIMO Wideband Mobile Channel Model 80
4.6 Analysis of the Proposed LTE-Advanced System 84
4.7 Operating Bands of LTE-Advanced 97
4.8 Summary
98
XI
CHAPTER 5 RESULTS AND DISCUSSIONS 99
5.1 Introduction 99
5.2 Simulation of Proposed LTE-A Bandwidth using MATLAB
Program
99
5.2.1 LTE-Advanced Downlink Intra Band Contiguous
Component Carriers to Support Channel Bandwidth 40 MHz
102
5.2.2 LTE-Advanced Downlink Intra Band Contiguous
Component Carriers to Support Channel Bandwidth 60 MHz
103
5.2.3 LTE-Advanced Downlink Intra Band Contiguous
Component Carriers to Support Channel Bandwidth 80 MHz
104
5.2.4 LTE-Advanced Downlink Intra Band Contiguous
Component Carriers to Support Channel Bandwidth 100
MHz
105
5.2.5 LTE-Advanced Downlink Intra Band Contiguous
Component Carriers to Support Channel Bandwidth 120
MHz
106
5.2.6 LTE-Advanced Downlink Intra Band non-Contiguous
Component Carriers to Support Channel Bandwidth 40 MHz
107
5.2.7 LTE-Advanced Downlink Intra Band non-Contiguous
Component Carriers to Support Channel Bandwidth 60 MHz
108
5.2.8
LTE-Advanced Downlink Intra Band non-Contiguous
Component Carriers to Support Channel Bandwidth 80 MHz
109
5.2.9 LTE-Advanced Downlink Intra Band non-Contiguous
Component Carriers to Support Channel Bandwidth 100
MHz
110
XII
5.2.10 LTE-Advanced Downlink Intra Band Non-Contiguous
Component Carriers to Support Channel Bandwidth 120
MHz
111
5.3 Throughput Analysis of Proposed LTE-A 112
5.3.1 Throughput of Proposed LTE-A with QPSK Modulation 113
5.3.2 Throughput of Proposed LTE-A with 16 QAM Modulation 117
5.3.3 Throughput of Proposed LTE-A with 64 QAM Modulation 120
5.4 Simulation of Proposed LTE-A Bandwidth using
SystemVue Program
124
5.4.1 LTE-Advanced Downlink Intra Band non-Contiguous
Component Carriers
125
5.4.2 LTE-Advanced Downlink Intra Band Contiguous
Component Carriers
131
5.5 SystemVue and Matlab Differences in Execution of
Proposed LTE-Advanced System
139
5.6 Comparison of Proposed LTE with the LTE and LTE-
Advanced
140
5.7 Summary
141
CHAPTER 6 CONCLUSIONS AND FUTURE WORK 142
6.1 Conclusions 142
6.2 Future Works
146
REFERENCES 148
APPENDIX 154
XIII
LIST OF FIGURES
2.1 The release of 3GPP specifications for LTE 7
2.2 Block diagram for OFDMA 14
2.3 Frequency domain illustration of OFDM 15
2.4 OFDM symbol in the time domain 16
2.5 OFDMA downlink transmitter 17
2.6 OFDMA downlink receiver for user 1 18
2.7 Principles of OFDMA for downlink transmission 21
2.8 Block diagram for SC-FDMA 25
2.9 Carrier aggregation scenarios 28
2.10 Improvement in downlink spectral efficiency going from 2G to 4G
system
33
2.11 Mobility in LTE-Advanced technology 34
2.12 Illustration of SU and MU MIMO systems 37
2.13 MIMO for LTE-Advanced DL and UL transmission 38
2.14 Cooperative MIMO on the LTE-Advanced downlink 40
2.15 Configuration of the relaying network 41
3.1 Types of carrier aggregation for LTE-Advanced 45
3.2 Examples of carrier aggregation 47
3.3 Carrier aggregation in LTE-Advanced 49
3.4 Structure of the MAC and PHY layer of LTE-A 51
3.5 Scenarios of CA with bandwidth 100 MHz 53
XIV
3.6 Definitions for intra band carrier aggregation RF parameters, for
an example with two aggregated carriers
54
3.7 The channel bandwidth for one RF carrier and the corresponding
transmission bandwidth configuration
55
4.1 OFDMA and SCFDMA 66
4.2 LTE-A downlink transmitter for 8x8 MIMO 68
4.3 LTE-A downlink receiver for 8x8 MIMO 69
4.4 Block diagram of downlink data aggregation 71
4.5 Proposed LTE-A system design 73
4.6 Aggregated channel bandwidth for contiguous carrier aggregation 74
4.7 Non-contiguous intra band CA 75
4.8 Interference effects on the system with 7 CC: (a) Schematic
design, (b) Contiguous carrier aggregation, (c) Non-contiguous
carrier aggregation.
77
4.9 Scenario of contiguous CA with bandwidth 120 MHz 78
4.10 Examples of non contiguous CA with bandwidth 120 MHz 79
4.11 MIMO Principle with 8x8 antenna configuration 81
4.12 Two antenna arrays in a scattering environment 82
4.13 Frequency-domain structures for LTE-A 84
4.14 The structure of the downlink resource grid 86
4.15 Types of modulation constellation 87
4.16 Relationship between throughput and no. of component carriers 96
4.17 Relationship among no. of CCs, efficiency and bandwidth in MHz 96
5.1 Data aggregation from the PHY up to MAC interface 100
5.2 LTE-A with channel bandwidth 40 MHz 102
5.3 LTE-A with channel bandwidth 60 MHz 103
5.4 LTE-A with channel bandwidth 80 MHz 104
XV
5.5 LTE-A with channel bandwidth 100 MHz 105
5.6 LTE-A with channel bandwidth 120 MHz 106
5.7 LTE-A non-contiguous CCs with channel bandwidth 40 MHz 107
5.8 LTE-A non-contiguous CCs with channel bandwidth 60 MHz 108
5.9 LTE-A non-contiguous CCs with channel bandwidth 80MHz 109
5.10 LTE-A non-contiguous CCs with channel bandwidth 100MHz 110
5.11 LTE-A non-contiguous CCs with channel bandwidth 120MHz 111
5.12 Throughput diagram with MIMO technique 112
5.13 Throughput of 2x2 MIMO LTE-A using QPSK modulation 114
5.14 Throughput of 4x4 MIMO LTE-A using QPSK modulation 115
5.15 Throughput of 8x8 MIMO LTE-A using QPSK modulation 116
5.16 Throughput of 2x2 MIMO LTE-A using 16 QAM modulation 118
5.17 Throughput of 4x4 MIMO LTE-A using 16 QAM modulation 119
5.18 Throughput of 8x8 MIMO LTE-A using 16 QAM modulation 120
5.19 Throughput of 2x2 MIMO LTE-A using 64 QAM modulation 122
5.20 Throughput of 4x4 MIMO LTE-A using 64 QAM modulation 123
5.21 Throughput of 8x8 MIMO LTE-A using 64 QAM modulation 124
5.22 Schematic design of non-contiguous CCs with aggregated channel
bandwidth 20 MHz
125
5.23 Non-contiguous CCs with aggregated channel bandwidth 20 MHz 126
5.24 Schematic design of non-contiguous CCs with aggregated channel
bandwidth 80 MHz
127
5.25 Non-contiguous CCs with aggregated channel bandwidth 80MHz 127
5.26 Schematic design of non-contiguous CCs with aggregated channel
bandwidth 100 MHz
128
5.27 Non-contiguous CCs with aggregated channel bandwidth 100MHz 129
5.28 Schematic design of non-contiguous CCs with aggregated channel 130
XVI
bandwidth 120 MHz
5.29 Non-contiguous CCs with aggregated channel bandwidth 120
MHz
130
5.30 Schematic design of contiguous CCs with aggregated channel
bandwidth 40 MHz
131
5.31 Contiguous CCs with aggregated channel bandwidth 40 MHz 132
5.32 Schematic design of contiguous CCs with aggregated channel
bandwidth 60 MHz
133
5.33 Contiguous CCs with aggregated channel bandwidth 60 MHz 133
5.34 Schematic design of contiguous CCs with aggregated channel
bandwidth 80 MHz
134
5.35 Contiguous CCs with aggregated channel bandwidth 80 MHz 135
5.36 Schematic design of contiguous CCs with aggregated channel
bandwidth 100 MHz
136
5.37 Contiguous CCs with aggregated channel bandwidth 100 MHz 136
5.38 Schematic design of contiguous CCs with aggregated channel
bandwidth 120 MHz
137
5.39 Contiguous CCs with aggregated channel bandwidth 120 MHz 138
6.1 Agilent W1716EP SystemVue Digital Pre-Distortion Builder 147
XVII
LIST OF TABLES
2.1 3GPP specification release for LTE and LTE-A 8
2.2 Major system requirement for Rel.8 LTE 10
2.3 System Performance Requirements for LTE-A compared to those
achieved in Rel.8 LTE
11
2.4 Requirements of LTE-Advanced 30
3.1 Deployment scenarios of LTE-Advanced 50
3.2 UE Carrier Aggregation Bandwidth Classes 56
3.3 Nominal channel spacing between contiguously aggregated CCs 57
3.4 Minimum channel spacing between contiguously aggregated CCs 58
3.5 Definition of Foffset 59
3.6 Intra band contiguous CA 62
3.7 Inter band non-contiguous CA 63
4.1 Coding rates for QPSK, 16QAM and 64 QAM 88
4.2 Transmission bandwidth configuration NRB in E-UTRA channel
bandwidths
89
4.3 Throughput of 2x2 MIMO 90
XVIII
4.4 Throughput of 4x4 MIMO 91
4.5 Throughput of 8x8 MIMO 91
4.6 Enhancement of data rate with different modulation techniques 92
4.7 Proposed one-layer to four-layer TBS translation 94
4.8 Throughput and efficiency for 8x8 MIMO LTE-A 95
4.9 Operating bands for LTE-Advanced (E-UTRA operating bands) 97
5.1 Highlights the main points of differences between LTE and the
proposed system
140
XVIII
LIST OF ABBREVIATIONS
1G - First Generation
2G - Second Generation
3G - Third Generation
3GPP - Third Generation Partnership Project
4G - Fourth Generation
ACLR - Adjacent Channel Leakage Ratio
AIM - Advanced Interference Management
B.W - Bandwidth
BER - Block Error Rate
BS - Base Station
BTS - Base Transceiver Station
BWGB - Bandwidth Guard Band
CA - Carrier Aggregation
CB - Coding Blocks
CCs - Component Carriers
CDF - Cumulative distribution function
CDMA - Code Division Multiple Access
CM - Cubic Metric
CoMP - Coordinated Multi Point
CP - Cyclic Prefix
C-Plane - Control-Plane
XIX
CRC - Cyclic Redundancy Check
CRS - Cell-specific Reference Symbol
CSI - Channel State Information
CSI-RS - Channel State Information -Reference Signal
CSIT - Channel State Information at the Transmitter
DC - Direct Current
DFT - Discrete Fourier Transform
DFT-S-OFDM - Discrete Fourier Transform–Spread–OFDM
DL - Downlink
DRX - Discontinuous Reception
EDGE - Enhanced Data Rates for GSM Evolution
eNB - enhanced Node B
EPC - Evolved Packet Core
E-UTRA - Evolved Universal Terrestrial Radio Access
E-UTRAN - Evolved UMTS Terrestrial Radio Access Networ
EVM - Error Vector Magnitude
FDD - Frequency Division Duplex
FDMA - Frequency Division Multiple Access
FEC - Forward Error Correction
FFS - For Further Studies
FFT - Fast Fourier Transform
GPRS - General Packet Radio Service
GPS - Global Positioning System
GSM - Global System for Mobile
HARQ - Hybrid Automatic Repeat Request
HeNB - Home eNodeB
HSDPA - High Speed Downlink Packet Access
XX
HSPA - High Speed Packet Access
HSUPA - High-Speed Uplink Packet Access
IDFT - Inverse Discrete Fourier Transform
IFFT - Inverse Fast Fourier Transform
IM3 - Third-order Inter Modulation
IMD - Inter Modulation Distortion
IMT-Advanced - International Mobile Telecommunications - Advanced
IP - Internet Protocol
ISI - Inter Symbol Interference
ITU - International Telecommunications Union
ITU-R - ITU-Radiocommunication
JP - Joint Processing
LTE - Long Term Evolution
LTE-A - Long Term Evolution-Advanced
MA - Multiple Access
MAC - Medium Access Control
MBRs - Maximum Bit Rates
MIMO - Multi Input Multi Output
MISO - Multiple Input Single Output
MU-MIMO - Multi User- Multi Input Multi Output
OCC - Orthogonal Cover Codes
OFDM - Orthogonal Frequency Division Multiplexing
OFDMA - Orthogonal Frequency Division Multiple Access
P - Power
P/S - Parallel to Serial
PA - Power Amplifiers
PAPR - Peak to Average Power Ratio
XXI
PCC - Primary component carrier
Pe - Error Probability
PHY layer - Physical layer
PRB - Physical Resource Block
PS - packet-switching
PUCCH - Physical Uplink Control Channel
QAM - Quadrature Amplitude Modulation
QoS - Quality of Service
QPSK - Quadrature Phase Shift Keyed
RBs - Resource Blocks
Rel-10 - Release-10
Rel-11 - Release-11
Rel-12 - Release-12
Rel-8 - Release-8
Rel-9 - Release-9
RF - Radio Frequency
RRC - Radio Resource Control
RS - Reference Signal
S/P - Serial to Parallel
SAE - System Architecture Evolution
SC-FDMA - Single Carrier Frequency Division Multiple Access
SDM - Spatial Division Multiplexing
SEM - Spectrum Emission Mask
SIMO - Single Input Multiple Output
SISO - Single Input Single Output
SNR - Signal to Noise Ratio
SU-MIMO - Single User- Multi Input Multi Output
XXII
TBs - Transport Blocks
TDD - Time Division Duplexing
TD-LTE - Time Division -Long Term Evolution
TDMA - Time Division Multiple Access
TD-SCDMA - Time Division-Synchronous Code Division Multiple
Access
TSG RAN - TSG Radio Access Network
UE - User equipment
UL - Uplink
UMTS - Universal Mobile Telecommunications System
U-Plane - User-Plane
WCDMA - Wideband Code Division Multiple Access
WiMAX - Worldwide interoperability for Microwave Access
βi - Fraction of Bandwidth Allocated to user i
CHAPTER 1
INTRODUCTION
The specifications of Long Term Evolution (LTE) in 3rd Generation Partnership Project
(3GPP) (Release-8) has recently been completed when work began on the new Long
Term Evolution- Advanced (LTE-A) standard (Release-9 and beyond). LTE-A meets or
exceeds the requirements imposed by International Telecommunication Union (ITU) to
Fourth Generation (4G) mobile systems. These requirements were unthinkable a few
years ago, but are now a reality. Peak data rates of 1 Gbps with bandwidths of 100 MHz
for the downlink, very low latency, more efficient interference management and
operational cost reduction are clear examples of why LTE-A is so appealing for
operators. Moreover, the quality breakthrough affects not only operators but also end
users, who are going to experience standards of quality similar to optical fiber.
In order to reach these levels of capacity and quality, the international scientific
community, in particular the 3GPP are developing different technological enhancements
on LTE. The most important technological proposals for LTE-Advanced are support of
wider bandwidth (carrier aggregation), advanced Multiple Input Multiple Output
(MIMO) techniques, Coordinated Multipoint transmission or reception (CoMP),
relaying and enhancements for Home eNodeB (HeNB) by Cardona, Monserrat and
Cabrejas (2013).
The 3GPP is in the process of development of certain technological proposals to
meet the demanding requirements of LTE-A. At this point, 3GPP has focused its
attention on different points that required technological innovations and one of them is
supporting of wider bandwidth (carrier aggregation) which is the main issue of this
thesis. Carrier aggregation can be defined as one of the most important technologies that
ensure the success of 4G technologies; this concept involves transmitting data in
2
multiple contiguous or non-contiguous Component Carriers (CCs). Each Component
Carrier (CC) takes a maximum bandwidth of 20 MHz to be compatible with LTE
Release 8 (Dahlman, Parkvall, Sköld and Beming, 2008). In addition to the peak data
rate, another motivation for carrier aggregation is to facilitate efficient use of fragmented
spectrum. In LTE-Advanced carrier aggregation, each component carrier can take any of
the channel bandwidths of 1.4, 3, 5, 10, 15, and 20 MHz that are supported by LTE.
Component carriers do not have to be of the same frequency (Taha, Hassanein and Abu
Ali, 2012). Operators with a fragmented spectrum can also provide high data rate
services through carrier aggregation technology. Carrier aggregation also allows
advanced features such as multi-carrier scheduling, interference coordination, quality of
service (QoS) differentiation, carrier load balancing, and heterogeneous deployment to
be used to further increase the spectral efficiency of the system. For instance, with QoS
differentiation, different subscription classes can be created whereby users are assigned
a bandwidth and a preferred carrier on the basis of their level of service agreement.
Multi carrier scheduling can also be used to schedule users in a carrier that is
experiencing less interference, thus improving throughput. Similarly, carrier aggregation
can be used with inter-cell interference coordination techniques to ensure that users are
scheduled in a manner that will generate less interference with surrounding cells.
1.1 Problem Statement
LTE-A has peak data rate limitations, its maximum reaches 1 Gbps due to number of
component carriers which is five. Proposed LTE-Advanced offers considerably higher
data rates than it in the current release of LTE-A. In addition, the spectrum usage
efficiency also has been improved.
In order to achieve these very high data rates it is necessary to increase the
transmission bandwidth over that has been used by the first releases of LTE. The
technique being proposed is termed carrier aggregation or sometimes channels
aggregation. Using LTE-Advanced carrier aggregation, it is possible to utilize several
3
carriers and in this way increase the overall transmission bandwidth. Proposed LTE-
Advanced bandwidth for both types: contiguous and non-contiguous needs a suitable
band which covers the whole bandwidth depending on the standard bands from 3GPP
organization.
1.2 Objectives of the Research
The main objectives of this research are:
1. To improve LTE-A disadvantages by increasing the bandwidth at both sides
(transmitter and receiver), where the current bandwidth is 100 MHz.
2. To increase peak data rate of the proposed system more than 1 Gbps which
represents the peak data rate of LTE-A.
3. To apply MIMO technology on the proposed LTE-A system with 8x8 antennas.
4. To increase the efficiency of the proposed system comparing to efficiency of
LTE and LTE-A systems.
1.3 Scope of the Research
This research is to study high bandwidth internet access anytime anywhere which is
continuously increasing. In order to deliver the main objectives of this research; initial
study of LTE and LTE-A techniques for cellular systems has been done by identifying
critical parameters for performance optimization in cellular systems and deriving the
mathematical formulations. Design the proposed LTE-Advanced system by developing
LTE and LTE-A algorithms so that the new system will have wider bandwidth and
higher peak data rate through Matlab and SystemVue programs. The design of the new
4
system depends on carrier aggregation technique to expand bandwidth and achieve the
main objectives of this research. Finally; the performance and the results of the proposed
algorithm had been compared with LTE and LTE-A technologies (current and new
developed) to highlight the features of the new design.
1.4 Contributions of the Research
LTE-Advanced is an intriguing technology which promises better performance than
LTE, larger bandwidth in proposed LTE-Advanced is the main aim of this study, easily
deployment in the network, increase user throughput for fully multi-media feature
services to exceed 4 Gbps, achieve spectrum flexibility, support scalable bandwidth up
to 120 MHz using spectrum aggregation, achieve backward compatibility includes inter-
working of LTE with 3GPP legacy systems, enable extended multi-antenna deployments
up to 8x8 MIMO and denser infrastructure in a cost-efficient way.
There are two basic solutions for the large bandwidth transmission in mobile
communication systems: the first is to design a large bandwidth system; the second is to
construct a system with a larger transmission bandwidth through collaboration between
different systems. The two solutions coexist and have an effect on each other in the
evolution of mobile communications. These enhancements can be appeared in Rel-11
and Rel-12 of 3GPP and will offer better user experience, lower cost per bit, greener
LTE-A base stations, and efficient self-organizing networks.
1.5 Outline of The Thesis
Chapter 2 provides an overview of the technical background of LTE and LTE-
Advanced. This chapter also explains all the parameter characteristics of throughput,
5
peak data rate, efficiency, mobility, and MIMO technology. This chapter also discusses
the uplink and downlink of LTE in details. Chapter 3 presents the theoretical
specifications of carrier aggregation (CA), component carriers (CCs), inter and intra
band CA including main types of carrier aggregation (Contiguous and non-Contiguous).
Chapter 4 deals with the methodology of the research: design of the proposed Long
Term Evolution-Advanced (LTE-A) system which supports 8x8 MIMO and all the
mathematical analysis relating to the proposed design while Chapter 5 provides results
obtained from the simulations using Matlab and SystemVue programs which can be
divided into two major parts: Intra band contiguous carrier aggregation and non-
contiguous carrier aggregation. In addition to the measurements of LTE-A throughput in
different modulation indexes (QPSK, 16 and 64 QAM), are compared. Finally, Chapter
6 concludes with a summary of the research and recommendation for future work.
6
CHAPTER 2
LTE AND LTE-ADVANVACED
2.1 Introduction
The first release of WCDMA Radio Access developed in Radio Access Network (TSG
RAN) was called release-993 and contained all features needed to meet the IMT-2000
requirements as defined by the International Telecommunications Union (ITU).
This release also included circuit-switched voice and video services, and data
services over both packet-switched and circuits watched bearers. The first major addition
of radio access features to WCDMA was HSPA, which was added in release-5 with High
Speed Downlink Packet Access (HSDPA) and release-6 with Enhanced Uplink. The 3G
evolution continued in 2004 (Holma and Toskala, 2009), when a workshop was
organized to initiate work on the 3GPP Long Term Evolution (LTE) radio interface. The
result of the LTE workshop was that a study item in 3GPP TSG RAN was created in
December 2004. The first 6 months were spent on defining the requirements, or design
targets, for LTE. These were documented in a 3GPP technical report and approved in
June 2005. Most notable are the requirements on high data rate at the cell edge and the
importance of low delay, in addition to the normal capacity and peak data rate
requirements. During the fall of 2005, 3GPP TSG RAN WG1 made extensive studies of
different basic physical layer technologies and in December 2005 the TSG RAN plenary
decided that the LTE radio access should be based on OFDM in the downlink and DFT-
pre-coded OFDM in the uplink. TSG RAN and its working groups then worked on the
LTE specifications and the specifications were approved in December 2007. Work has
7
since then continued on LTE, with new features added in each release refer to Dahlman,
Parkvall and Sköld (2011).
Figure 2.1: The release of 3GPP specifications for LTE (Dahlman, et al., 2008),
(Dahlman, et al., 2011).
3GPP has completed the specification for Long Term Evolution as part of
Release-8 as shown in Figure 2.1; the work on LTE began in 2004 and completed in 2009
and first deployment occurred in 2010. In Release-8, Long Term Evolution (LTE) by
Uhrer, Wrulich, Ikuno, Bosanska, & Rupp (2009) was standardized by 3GPP as the
successor of the Universal Mobile Telecommunication System (UMTS). The targets for
downlink and uplink peak data rate requirements were set to 100 Mbps and 50 Mbps,
respectively, when operating in a 20 MHz spectrum allocation. First performance
evaluations show that the throughput of the LTE physical layer and MIMO enhanced
WCDMA is approximately the same. Basically 3GPP is addressing the requirements to
satisfy the specification of IMT-Advanced (International Mobile Telecommunications-
Advanced) in LTE-Advanced, LTE-Advanced standards are defined in 3GPP Release-10.
8
The specifications for LTE are produced by the Third Generation Partnership
Project according to Cox (2012), in the same way as the specifications for UMTS and
GSM. They are organized into releases, where each of which contains a stable and clearly
defined set of features. The use of releases allows equipment manufacturers to build
devices using some or all of the features of earlier releases, while 3GPP continues to add
new features to the system in a later release. Within each release, the specifications
progress through a number of different versions. New functionality can be added to
successive versions until the date when the release is frozen, after which the only changes
involve refinement of the technical details, corrections and clarifications (3GPP Releases.
2011). Table 2.1 lists the releases that 3GPP have used since the introduction of UMTS,
together with the most important features of each release. Note that the numbering
scheme was changed after Release-99, so that later releases are numbered from 4 through
to 11 (LTE-A).
Table 2.1: 3GPP specification release for LTE and LTE-A (Cox, 2012)
Release Data Frozen New features
R99 March 2000 WCDMA air interface
R4 March 2001 TD-SCDMA air interface
R5 June 2002 HSDPA, IP multimedia subsystem
R6 March 2005 HSUPA
R7 December 2007 Enhancements to HSPA
R8 December 2008 LTE, SAE
R9 December 2009 Enhancements to LTE and SAE
R10 March 2011 LTE-Advanced
R11 September 2012 Enhancements to LTE-Advanced
9
2.2 System Requirements for LTE and LTE-Advanced
Table 2.2 gives the system requirements for the Release-8 LTE. The Release-8 LTE
supports scalable multiple transmission bandwidths including 1.4, 3, 5, 10, 15, and 20
MHz (Holma and Toskala, 2007). One of the most distinctive features is the support for
only the Packet-Switching (PS) mode. Hence, all traffic flows including real time service
with a rigid delay requirement such as voice services is provided in the PS domain in a
unified manner. The target peak data rate is 100 Mbps in the downlink and 50 Mbps in
the uplink. The target values for the average or cell edge user throughput and spectrum
efficiency are specified as relative improvements from those of High Speed Downlink
Packet Access (HSDPA) or High Speed Uplink Packet Access (HSUPA) in the downlink
and uplink, respectively. Here, the average cell spectral efficiency corresponds to
capacity, and the cell-edge user throughput is defined as the 5% value in the Cumulative
Distribution Function (CDF) of the user throughput. Both are very important
requirements from the viewpoint of practical system performance in cellular
environments. In particular, improvement in the cell-edge user throughput is requested to
mitigate the unfair achievable performance between the vicinity of the cell site and cell
edge. After extensive discussions in the 3GPP meetings, it was verified that the
requirements and targets for the Reease-8 LTE were achieved by the specified radio
interface using the relevant techniques.
10
Table 2.2: Major System Requirement for Rel.8 LTE (Sawahashi, Taoka, Tanno, and
Nakamura, 2009)
Bandwidth Support of scalable bandwidths
(1.4, 3, 5, 15 and 20 MHz )
Peak data rate DL 100 MHz
UL 50 MHz
Spectrum efficiency
(vs. Rel. 6 HSDPA/HSUPA)
DL 3- 4 times (avarge)
UL 2- 3 times (cell edge)
User throughput
(vs. Rel. 6 HSDPA/HSUPA)
DL 2- 3 times (avarge)
UL 2- 3 times (cell edge)
The requirements for LTE-Advanced are specified by Fazel and Kaiser (2008).
The following general requirements for LTE-Advanced were agreed upon. LTE-
Advanced will be an evolution of Release-8 LTE. Hence, distinctive performance gains
from Release-8 LTE are requested. Moreover, LTE-Advanced will satisfy all the relevant
requirements for Release-8 LTE.
LTE is requested in LTE-Advanced. Thus, a set of User Equipment (UE) for
LTE-Advanced must be able to access Release-8 LTE networks, and LTE-Advanced
networks must be able to support Release-8 LTE UEs. LTE-Advanced shall meet or
exceed the IMT-Advanced requirements within the ITU-R time plan.
In Table 2.3, the requirements and target values for LTE-Advanced are listed with
those achieved in the Release-8 LTE. The summary of the major issues which depend on
MIMO channel transmissions is highlighted, with respect to the peak data rate.
The target values for the peak frequency efficiency are 2 and 4 fold those
achieved in the Release-8 LTE, i.e., 30 and 15 bps/Hz in the downlink and uplink,
respectively. It is noted, however, that this requirement is not mandatory and is to be
achieved by a combination of base stations (BSs) and high class UEs with a larger
number of antennas. In LTE-Advanced, 1.4 to 1.6 folds improvements for the capacity
11
and cell-edge user throughput are expected from Release-8 LTE for each antenna
configuration.
Table 2.3: System Performance Requirements for LTE-A compared to those achieved in
Rel.8 LTE (Sawahashi, et al., 2009)
DL/UL Antenna
configuration
Rel.8 LTE
achievement
LTE-Advanced
Peak data rate DL - 300 Mbps 1 Gbps
UL - 75 Mbps 500 Mbps
Peak spectrum efficiency
[bps/Hz]
DL - 15 30
UL - 3.75 15
Capacity [bps/Hz/ cell] DL 2x2 1.69 2.4
4x2 1.87 2.6
4x4 2.67 3.7
UL 1x2 0.74 1.2
2x4 - 2.0
Cell- edge user throughput
[bps/ Hz/ cell/ User]
DL 2x2 0.05 0.07
4x2 0.06 0.09
4x4 0.08 0.12
UL 1x2 0.024 0.04
2x4 - 0.07
2.3 Long Term Evolution Standard
The 3GPP Long Term Evolution (LTE) release 8 defines the basic functionality of a new,
high-performance air interface providing high user data rates in combination with low
latency based on MIMO, OFDMA, and an optimized system architecture evolution
(SAE) as main enablers.
LTE was required to deliver a peak data rate of 100 Mbps in the downlink and 50
Mbps in the uplink. This requirement exceeded in the eventual system, which delivers
12
peak data rates of 300 Mbps and 75 Mbps respectively. For comparison, the peak data
rate of WCDMA, in Release-6 of the 3GPP specifications, is 14 Mbps in the downlink
and 5.7 Mbps in the uplink. It cannot be stressed too strongly, however, that these peak
data rates can only be reached in idealized conditions, and are wholly unachievable in any
realistic scenario. A better measure is the spectral efficiency, which expresses the typical
capacity of one cell per unit bandwidth. LTE is required to support a spectral efficiency
three to four times greater than that of Release-6 WCDMA in the downlink and two to
three times greater in the uplink.
Another important issue is latency time, particularly for time critical applications
such as voice and interactive games. There are two aspects to this. Firstly, the
requirements state that the time taken for data to travel between the mobile phone and the
fixed network should be less than five milliseconds, provided that the air interface is
uncongested. Secondly, mobile phones can operate in two states: an active state in which
they are communicating with the network and a low power standby state. The
requirements state that a phone should switch from standby to the active state, after an
intervention from the user, in less than 100 milliseconds.
There are also requirements on coverage and mobility. LTE is optimized for cell
sizes up to 5 km, works with degraded performance up to 30 km and supports cell sizes
of up to 100 km. It is also optimized for mobile speeds up to 15 km/hr, works with high
performance up to 120 km/hr and supports speeds of up to 350 km/hr. Finally, LTE is
designed to work with a variety of different bandwidths, which range from 1.4 MHz up to
a maximum of 20 MHz according to 3GPP TS 25.912 (2006).
2.4 Key Enabling Technologies and Feature of LTE
This chapter provides technical information about main LTE enabling technologies. The
areas covered range from basic concepts to research grade material, including future
13
directions, the main LTE enabling technologies can be presented in downlink physical
layer (OFDMA) and uplink physical layer (SC-FDMA).
2.4.1 Downlink of Long Term Evolution
At this point, the structure of OFDMA and the main principles of downlink transmission
with the main calculations of system capacity are discussed as in the following:
A- Downlink System Model of LTE
Orthogonal Frequency Division Multiple Access (OFDMA) has several advantages over
the Wideband Code Division Multiple Access (WCDMA) technique used in the previous
generations of UMTS. As demonstrated in (Molisch, 2011), OFDMA provides better
performance in terms of spectral efficiency (i.e. how much data can be transmitted for a
given amount of bandwidth) than does WCDMA both for broadcast and for unicast
services. This is due to the lack of inter-symbol interference from multipath channels and
the absence of intra-cell interference because users are orthogonal (i.e. they do not
interfere with each other) in the frequency domain. In addition, the OFDMA transmission
technique scales easily to different bandwidths, so multiple system bandwidth
configurations can be efficiently supported. In addition, low-complexity receivers can be
used with OFDMA.
14
Figure 2.2: Block diagram for OFDMA (Khlifi and Bouallegue, 2012).
OFDMA, frequency-domain scheduling and MIMO processing techniques can be
used. An example of frequency-domain scheduling techniques is frequency-selective
scheduling. In frequency-selective scheduling, users are assigned data only on good
frequency bands (i.e. bands with large gain), which are determined on the basis of
channel quality feedback from the UE. For broadcast services, single-frequency broadcast
networks can be supported. In this case, multiple base stations transmit the same
broadcast signals. The signals are coherently combined at the user, thus improving
performance at the cell edge substantially.
A basic block diagram illustrating OFDMA signal generation for one OFDM
symbol is shown in Figure 2.2 where data symbols from different users are mapped to
different subcarriers depending on the frequency bands assigned to those users. This is
done in the frequency domain. The information is then subjected to an Inverse Fast
Fourier Transform (IFFT) to convert the frequency domain subcarriers into time-domain
signals. A cyclic prefix is then added, and the signal is ready for transmission.
Note that the basic transmission unit for data is a subframe that spans multiple
OFDM symbols. At the receiver, the reverse operation is performed. The cyclic prefix is
removed, and then the time-domain signal is subjected to a Fast Fourier Transform (FFT)
Symbol
Mapping S/P P/S
Append
CP
M-point
IFFT
Subcarrier
Mapping
Channel
Subcarrier
Demapping P/S
Symbol
De-Mapping M-point
FFT
Remove
CP S/P
15
so that the modulation symbols on each subcarrier can be extracted. Each user then
extracts the frequency resource units corresponding to its assigned subcarriers.
Equalization is performed and the data is passed onward for decoding.
Figure 2.3: Frequency domain illustration of OFDM (Ghosh and Ratasuk, 2011).
A frequency-domain illustration of OFDM transmission is shown in Figure 2.3,
where each data symbol is modulated onto one of the subcarriers. The OFDM parameters
must be selected carefully in order to meet LTE requirements while minimizing
overhead. Key design parameters include cyclic-prefix length, subcarrier spacing, and
resource-block size. In LTE, the Direct Current (DC) subcarrier (the subcarrier at the
center frequency) is not used since the performance of this subcarrier can be very poor for
certain transmitter and receiver designs. Thus, the usable subcarriers are located around
this center frequency as shown in Figure 2.3. The subcarrier spacing is the frequency
spacing between two adjacent subcarriers. Small subcarrier spacing means that more
subcarriers are available for a given amount of bandwidth, thus increasing the spectral
efficiency since more data symbols are available for a given amount of bandwidth. In
addition, small subcarrier spacing also ensures that the fading on each subcarrier is
frequency-non-selective. However, performance degrades as subcarrier spacing decreases
due to Doppler shift and phase noise.
16
Doppler shift is caused by UE movement with larger shift as UE velocity
increases. This causes inter-carrier interference whose degradation increases as the
subcarrier spacing decreases. Phase noise is caused by fluctuations in the frequency of the
local oscillator, and will cause inter-carrier interference as well. In order to minimize
performance degradation from phase noise, the subcarrier spacing should be greater than
10 kHz. Furthermore, to support UE up to a speed of 350 km/h, the subcarrier spacing
should be around 9–17 kHz. As a result, a subcarrier spacing of 15 kHz was chosen for
LTE.
Figure 2.4: OFDM symbol in the time domain (Preben, Koivisto, Pedersen, Kovács,
Raaf, Pajukoski and Rinne, 2009).
In LTE, frequency resource is assigned in units of resource blocks. Several factors
must be considered in the selection of the resource block size in frequency. First, it
should be small enough that the frequency selective scheduling (i.e. scheduling data
transmission on good frequency subcarriers) gain is large. Small resource-block size
ensures that the frequency response within each resource block is similar, thus enabling
the scheduler to assign only good resource blocks. However, since the eNB does not
know which resource blocks are experiencing good channel conditions, the UE must
report this information back to the eNB. Thus, the resource-block size must be
sufficiently large that the feedback overhead is not too high. It also should be sufficiently
large to minimize downlink control signaling, which must be used to inform the UE of its
resource allocation. In 3GPP R1-050720, (2005), performance analysis of frequency
CP CP
Data
Time OFDM Symbol
17
selective scheduling was performed. It was found that a resource block of size 200–900
kHz provides good performance. Since, in LTE, a subframe size of 1 ms is used to ensure
low latency, the resource block size in frequency should be small so that small data
packets can be efficiently supported. As a result, 180 kHz (12 subcarriers) was chosen as
the resource-block bandwidth.
A cyclic prefix is needed for OFDMA transmission in order to prevent inter-
symbol interference from previously transmitted OFDM symbols. The OFDM symbol
with cyclic prefix and data is shown in Figure 2.4. Note that the cyclic prefix does not
carry useful data and is removed at the receiver prior to processing. As a result, it is
desirable to have a small cyclic prefix as possible in order to minimize the overhead. In
general, the length is chosen on the basis of the expected delay spread of the propagation
channel plus some margin to allow for imperfect timing alignment.
The block diagram for a downlink OFDMA are shown in Figure 2.5 and Figure
2.6 where the basic flow is very similar to an OFDM system except for now K users
share the L subcarriers, with each user being allocated MK subcarriers. Although in
theory it is possible to have users share subcarriers, this never occur in practice, so ∑k Mk
= L and each subcarrier only has one user assigned to it (Ghosh, Zhang, Andrews &
Muhamed, 2011).
Figure 2.5: OFDMA downlink transmitter (Ghosh, et al., 2011).
18
In OFDM, all subcarriers are assigned to a single user. Hence, for multiple users
to communicate with the BS, the set of subcarriers are assigned to each in a Time
Division Multiple Access (TDMA) fashion. Alternatively, an OFDM-based multiple
access mechanism, namely the OFDMA, assigns sets of subcarriers to different users. In
particular, the total available bandwidth is divided into M sets, each consisting of L
subcarriers.
Figure 2.6: OFDMA downlink receiver for user 1(Ghosh, et al., 2011).
In order to analysis the performance of OFDMA, the transmitted signal of one
user with M allocated subcarriers is expressed as (Zhang, Huang, Liu and Zhang, 2006):
D=[d0 d1 … dM-1]T (2.1)
where [.]T
represents transpose operation and di is the modulated symbol. After
IFFT modulator, the signal vector S will be:
S=F*N TN,M D (2.2)
19
where TN,M the mapping matrix for subcarrier assignment and its element values
are decided by either distributed subcarrier allocation or localized subcarrier allocation.
F*N is the N point IFFT matrix and [.]
* represents conjugate operation. Moreover,
FN=[flT
, f2T, ….,
fN
T ]
T (2.3)
f1= (2.4)
After fading channel and FFT process, the received signal in frequency domain is:
R= H TN,M D+n (2.5)
where
H = diag(HK) (2.6)
and Hk is the frequency channel response at subcarrier k. n is the AWGN noise
vector and
R = [r(O),r(l),..., r(N -1)]T (2.7)
in which r(k) is the received signal at subcarrier k .
Despite the relatively straight forwardness of OFDMA, it has very attractive
advantages. Probably the most important of these is its inherent exploitation of frequency
and multiuser diversities. Frequency diversity is exploited through randomly distributing
the subcarriers of a single user over the entire band, reducing the probability that all the
subcarriers of a single user experience deep fades. Such allocation is particularly the case
when distributed subcarrier assignment is employed. On the other hand, multiuser
20
diversity is exploited through assigning contiguous sets of subcarriers to users
experiencing good channel conditions a study by Yang (2010). Another important
advantage of OFDMA is its inherent adaptive bandwidth assignment. In the Jiang, Song
and Zhang (2010), OFDMA subcarrier structure can support a wide range of bandwidths,
since the transmission bandwidth consists of a large number of orthogonal subcarriers
that can be separately turned on and off; wider transmission bandwidths, as high as 100
MHz, can be easily realized (Dahlman, et al., 2008).
B- Downlink Data Transmission of LTE
For transmission of data over the air interface, it was decided to use a new transmission
scheme in LTE which is completely different from the Code Division Multiple Access
(CDMA) approach of UMTS. Instead of using only one carrier over the broad frequency
band, it was decided to use a transmission scheme referred to as Orthogonal Frequency
Division Multiple Access (OFDMA). OFDMA transmits a data stream by using several
narrow-band subcarriers simultaneously, for example 512, 1024, or even more,
depending on the overall available bandwidth of the channel (e.g. 5, 10, 20 MHz).
As many bits are transported in parallel, the transmission speed on each subcarrier
can be much lower than the overall resulting data rate. This is important in a practical
radio environment in order to minimize the effect of multipath fading created by slightly
different arrival times of the signal from different directions. The second reason this
approach was selected was because the effect of multipath fading and delay spread
becomes independent of the amount of bandwidth used for the channel. This is because
the bandwidth of each subcarrier remains the same and only the number of subcarriers is
changed. With the previously used CDMA modulation, using a 20 MHz carrier would
have been impractical, as the time each bit was transmitted would have been so short that
the interference due to the delay spread on different paths of the signal would have
become dominant (Sauter, 2009).
21
Figure 2.7 shows how the input bits are first grouped and assigned for
transmission over different frequencies (subcarriers). For example, 4 bits (representing a
16-QAM modulation) are sent per transmission step per subcarrier. A transmission step is
also referred to as a symbol. With 64-QAM modulations, 6 bits are encoded in a single
symbol, raising the data rate further. On the other hand, encoding more bits in a single
symbol makes it harder for the receiver to decode the symbol if it was altered by
interference. This is the reason why different modulation schemes are used depending on
transmission conditions.
Figure 2.7: Principles of OFDMA for downlink transmission (Sauter, 2009).
22
In theory, each subcarrier signal could be generated by a separate transmission
chain hardware block. The output of these blocks would then have to be summed up and
the resulting signal could then be sent over the air. Because of the high number of
subcarriers used, this approach is not feasible. Instead, a mathematical approach is taken
as follows.
As each subcarrier is transmitted on a different frequency, a graph which shows
the frequency on the x-axis and the amplitude of each subcarrier on the y-axis can be
constructed. Then, a mathematical function called Inverse Fast Fourier Transformation
(IFFT) is applied, which transforms the diagram from the frequency domain to the time
domain. This diagram has the time on the x-axis and represents the same signal as would
have been generated by the separate transmission chains for each subcarrier when
summed up. The IFFT thus does exactly the same job as the separate transmission chains
for each subcarrier would do, including summing up the individual results.
On the receiver side, the signal is first demodulated and amplified. The result is
then treated by a Fast Fourier Transformation (FFT) function which converts the time
signal back into the frequency domain. This reconstructs the frequency/amplitude
diagram created at the transmitter. At the center frequency of each subcarrier a detector
function is then used to generate the bits originally used to create the subcarrier.
The explanation has so far covered the orthogonal frequency division aspect of
OFDMA transmissions. The Multiple Access (MA) part of the abbreviation refers to the
fact that the data sent in the downlink is received by several users simultaneously.
Control messages inform mobile devices waiting for data which part of the transmission
is addressed to them and which part they can ignore. This is, however, just a logical
separation. On the physical layer, this only requires that modulation schemes ranging
from QPSK over 16-QAM to 64-QAM can be quickly changed for different subcarriers
in order to accommodate the different reception conditions of subscribers (Sauter, 2009).
23
C- Downlink Capacity of LTE
Unlike Time Division Multiple Access (TDMA), OFDMA allows sharing resources
among multiple users accessing the system by allocating to a user only a fraction of the
total bandwidth therefore multiple users can transmit simultaneously on orthogonal
subcarriers. The transmissions from multiple users are orthogonal as long as the relative
delay between the received transmissions is within the Cyclic Prefix (CP) length. In
general, the CP length is several microseconds, to account for the multi-path delay
spread, and therefore makes the timing synchronization within the CP length feasible.
This is in contrast to synchronous WCDMA where sub-chip level synchronization
(generally a small fraction of a microsecond depending upon the chip rate) is required to
guarantee orthogonal transmissions (Khan, 2009). The uplink capacity limit for an
OFDMA system can be written as:
(2.8)
where βi is the fraction of bandwidth allocated to user i. For the case where the
bandwidth is equally divided among the K users transmitting simultaneously, P is
received power for a user, background noise N0 and f ratio between other-cell and own-
cell signal the above formula can be simplified as below:
(2.9)
24
There is no intra-cell (multiple access) interference or Inter Symbol Interference
(ISI) due to orthogonal subcarriers used by different users and 1-tap OFDM subcarrier
equalization.
However, cyclic prefix (guard interval) overhead (typically around 10%) needs to
be taken into account for the OFDM case. Therefore, the capacity of an OFDMA system
can be scaled-down to account for CP overhead as below:
(2.10)
where Ts is the OFDM symbol duration and Δ is the cyclic prefix duration.
2.4.2 Uplink of Long Term Evolution
In the uplink, Single Carrier Frequency Division Multiple Access (SC-FDMA) is
selected due to its ability to provide similar advantages to OFDM, such as orthogonality
among users, frequency domain equalization, and robustness with respect to multipath
operation while maintaining a low power amplifier back-off or de-rating requirement
according to Khan (2009). The key characteristic of single-carrier transmission is that
each data symbol is transmitted using the entire allocated bandwidth. This is different
than OFDM, where each data symbol is transmitted using only one subcarrier.
In LTE, Discrete Fourier Transform–Spread–OFDM (DFT-S-OFDM) is used to
generate the SC-FDMA signal in the frequency domain as shown in Figure 2.8. Note that
generation of the SC-FDMA signal using DFT-S-OFDM is almost identical to that of
OFDM, with the exception of the additional M-point Discrete Fourier Transform (DFT).
Although DFT processing is more computationally intensive than the FFT, efficient
implementation for certain DFT sizes is available. Specifically, DFTs of prime length can
be calculated using efficient FFT algorithms. The method shown in Figure 2.8 generates
SC-FDMA signal in the frequency domain. This allows frequency-domain pulse shaping
to be applied prior to the IFFT to further reduce the cubic metric.
148
REFERENCES
3GPP Technical Report 36.913. Requirements for Further Advancements for Evolved
Universal Terrestrial Radio Access (E-UTRA) (LTE-Advanced). www.3gpp.org.
3GPP Technical Report R1-050720 (2005). Frequency selective scheduling resource
block size for EUTRA downlink. Motorola. RAN1#42. San Diego. CA.
3GPP Technical Report R1-060385 (2006). Cubic Metric in 3GPP-LTE. 3GPP
Motorola. Denver. USA.
3GPP Technical Report R1-084469. Cubic Metric comparison of OFDMA and
Clustered-DFTS-OFDM/NxDFTS-OFDM. 3GPP.
3GPP Technical Report R4-101062 (2010). LTE-A deployment scenarios; TSG-RAN
WG4 Meeting. CA. USA.
3GPP Technical Report RP-100661(2010). Revised Carrier Aggregation for LTE WID.
Nokia Corporation. Seoul. South Korea.
3GPP Technical Report TR 36.814 (2011). Evolved Universal Terrestrial Radio Access
(E-UTRA) further advancements for E-UTRA physical layer aspects, Release 9.
Section 8.1.
3GPP Technical Report TR 36.815. Further advancements for E-UTRA; LTE-Advanced
feasibility studies in RAN WG4. (Release 9). 3GPP. v9.1.0.
3GPP Technical Report TR 36.819 (2011). Coordinated multi-point operation for LTE
physical layer aspects. Release 11.
3GPP Technical Report TR 36.912 Release 10 (2011). LTE; Feasibility study for
Further Advancements for E-UTRA (LTE-Advanced) Technical Report. ETSI TR
136 912 V10.0.0. pp. 22. Version 10.0.0.
149
3GPP Technical Report TR-36.808. Technical specification group radio access network;
Evolved Universal Terrestrial Radio Access (E-UTRA); carrier aggregation; base
station (BS) radio transmission and reception (Release 10).
3GPP Technical Report TS 25.912 (2006). Feasibility study for evolved Universal
Terrestrial Radio Access (UTRA) and Universal Terrestrial Radio Access Network
(UTRAN). V 5.2.0.
3GPP Technical Report TS 25.913 (2009). Requirements for Evolved UTRA (E-UTRA)
and Evolved UTRAN (E-UTRAN). Release 8.
3GPP Technical Report TS 36.101 Release 8 (Dec. 2009) .3rd Generation Partnership
Project; Evolved Universal Terrestrial Radio Access (E-UTRA) Radio
Transmission and Reception (Release 8). Technical specification group radio
access network. pp.14 V6.6.0.
3GPP Technical Report TS 36.101. User Equipment (UE) radio transmission and
reception. Technical specification group radio access network.
3GPP Technical Report TS 36.104. Base Station (BS) radio transmission and reception.
Technical specification group radio access network.
Ahmadi, S. (2009). An overview of next-generation mobile WiMAX technology. Intel
Corporation-Communications Magazine. IEEE.
Akyildiz, I. F., Gutierrez-Estevez, D. M. & Reyes, E. C. (2010). The evolution to 4G
cellular systems: LTE Advanced. Journal of Physical Communication. Vol. 3. No.
4. Elesevier. pp. 217–44.
Cardona, N., Monserrat, J. F. & Cabrejas, J. (2013). LTE-Advanced and next generation
wireless networks: channel modelling and propagation. John Wiley. pp. 13-26.
Cox, C. (2012). An introduction to LTE: LTE, LTE-Advanced, SAE and 4G mobile
communications. John Wiley. UK. pp. 12-288.
Dahlman, E., Parkvall, S. & Sköld, J (2011). 4G LTE/LTE-Advanced for mobile
broadband. Elsevier Ltd. UK. pp.11-380.
150
Dahlman, E., Parkvall, S., Sköld, J. & Beming, P. (2008). 3G evolution : HSPA and LTE
for mobile broadband. Elsevier pp.543.
Fazel K. & Kaiser, S. (2008). Multi-Carrier and Spread Spectrum Systems: From
OFDM and MC-CDMA to LTE and WiMAX. A John Wiley and Sons, Ltd.
Publication: Second Edition. pp. 218-220.
Forsberg, D., Horn, G., Moeller, W. & Niemi, V. (2010). LTE security. John Wiley and
Sons. UK. pp. 255.
Ghosh, A. & Ratasuk, R. (2011). Essentials of LTE and LTE-A. Cambridge wireless
essentials series. UK. pp. 3-161.
Ghosh, A., Zhang, J. & Andrews, J. G. (2011). Fundamentals of LTE. Pearson education
inc. USA. pp.168-245.
Hashimoto, A., Yoshino, H. & Atarashi, H. (2008). Roadmap of IMT-advanced
development. NTTDoCoMo Inc., Tokyo- Microwave Magazine. IEEE.
Holma, H. & Toskala, A. (2007). WCDMA for UMTS – HSPA evolution and LTE.
Fourth edition: John Wiley and Sons. pp.473.
Holma, H. & Toskala, A. (2009). LTE for UMTS –OFDMA and SC-FDMA based radio
access. John Wiley & Sons. pp.4.
Holma, H. & Toskala, A. (2011). LTE for UMTS: Evolution to LTE-Advanced. Second
edition. John Wiley and Sons. pp.13-14.
Holma, H. & Toskala, A. (2012). LTE-Advanced: 3GPP Solution for IMT-Advanced.
John Wiley and Sons: First edition. pp. 5-66.
Hossain, E., Kim, D. I. & Bhargava, V. K. (2011). Cooperative cellular wireless
networks. Cambridge. New York. First published. pp. 427.
Huang, H., Papadias, C. B. & Venkatesan S. (2012). MIMO communication for cellular
networks. Springer. New York. Dordrecht Heidelberg London. pp. 290-295.
Jiang, T., Song, L. & Zhang V. (2010).Orthogonal Frequency Division Multiple Access
fundamentals and applications. Auerbach publications CRC. pp.5.
151
Khan, F. (2009). LTE for 4G Mobile broadband air interface technologies and
performance. Cambridge. USA. pp. 79-148.
Khlifi, A. & Bouallegue, R. (2012). Comparison between performances of channel
estimation techniques for CP-LTE and ZP-LTE downlink systems. Int. Journal of
Computer Networks & Communications Vol.4. No.4. pp. 223-228.
Korowajczuk, L. (2011). LTE, WiMAX and WLAN network design, optimization and
performance analysis. John Wiley. USA. First edition. 2011. pp.440-443.
Kreher, R. & Gaenger, K. (2011). LTE Signaling, troubleshooting, and optimization.
John Wiley and Sons. pp.46.
Lescuyer, P. & Lucidarme, T. (2008). Evolved packet system (EPS): the LTE and SAE
evolution of 3G UMTS. John Wiley and Sons. England. pp.126-127.
Molisch, A. F. (2011). Wireless communications. John Wiley and Sons: Second Edition.
pp.465-670.
Osseiran, A., Monserrat, J. F., Mohr W. (2011). Mobile and wireless communications
for IMT-Advanced and beyond. John Wiley and Sons. pp. 46-47.
Pagès, A. S. (2009). A Long Term Evolution link level simulator. Universitati
Politècnica de Catalunya. pp. 23.
Parkvall, S., Englund, E., Furuskär, A., Dahlman, E., Jönsson, T. & Paravati, A.
(2010). LTE Evolution towards IMT-Advanced and Commercial Network
Performance. Proc. IEEE Ericsson Research. Sweden. pp. 153.
Penttinen, J. T. (2012). The LTE / SAE deployment handbook. John Wiley and Sons. UK.
pp. 300-305.
Preben, M., Koivisto, T., Pedersen, I., Kovács, I., Raaf, B., Pajukoski K. & Rinne M.
(2009). LTE-Advanced: the path towards Gigabit/s in wireless mobile
communications. Proc. Int. Conference on Wireless Communication, Vehicular
Technology, Information Theory and Aerospace & Electronics Systems
Technology. Aalborg. pp. 147-149.
152
Sauter, M. (2009). Beyond 3G – Bringing networks, terminals and the web together
LTE, WiMAX, IMS, 4G devices and the mobile Web 2.0. John Wiley. UK. pp.51-
54.
Sawahashi, M., Taoka, Y. H., Tanno, M. & Nakamura, T. (2009). Broadband radio
access LTE and LTE-Advanced. Proc. IEEE Int. Symposium on Intelligent Signal
Processing and Communication Systems (ISPACS). pp. 224-225.
Schoenen, R. (2009). Long Term Evolution: 3GPP LTE radio and cellular technology.
Taylor & Francis Group. LLC. pp.284.
Sesia, S., Toufik, I. & Baker, M. (2009). LTE – The UMTS Long Term Evolution: from
theory to practice. First edition John Wiley and Sons. pp.8-624.
Sesia, S., Toufik, I. & Baker, M. (2011). LTE – The UMTS Long Term Evolution: from
theory to practice-including Release 10 for LTE-Advanced. Second edition John
Wiley and Sons pp. 623-624.
Taha, A. M., Hassanein, H. S. & Abu Ali, N. (2012). LTE, LTE-Advanced and WiMAX:
towards IMT-Advanced networks. John Wiley. pp. 25-136.
Uhrer, C. M., Wrulich, M., Ikuno, J. C., Bosanska, D. & Rupp, M (2009). Simulating the
long term evolution physical layer. Proc. 17th
European Signal Processing
Conference (EUSIPCO 2009) Glasgow. Scotland. pp.1.
Yahiya, A. (2011). Understanding LTE and its performance. Springer Dordrecht
Heidelberg. New York. pp. 9-14.
Yang, S. (2010). OFDMA system analysis and design. First edtion Boston. Artech
house. USA.
Yonis, A. Z. & Abdullah, M. F. L. (2012). Simulation of novel non-adjacent component
carriers in LTE-Advanced. Proc. IEEE Int. Conf. on electronic devices. system and
application (ICEDSA). pp. 293-298.
Yonis, A. Z., Abdullah, M. F. L. & Ghanim, M. F. (2012) .Design and implementation
of intra band contiguous component carriers on LTE-A. Int. Journal of Computer
Applications. Vol.41. No.14. USA. pp. 25-28.
153
Zemede, M. (2011). LTE-Advanced physical layer design and test challenges: carrier
aggregation. Microwave Journal. UK. pp. 20.
Zhang, X. & Zhou, A. (2013). LTE-Advanced air interface technology. CRC press
Taylor & Francis group. Parkway. pp.1-37.
Zhang, J., Huang, C., Liu, G. & Zhang, P. (2006). Comparison of the link level
performance between OFDMA and SC-FDMA. IEEE Int. Conf. on
communications and networking in China. pp. 1-6.
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