Power Efficiency in Broadband Wireless Communications focuses on the improvement of power efficiency in wireless communication systems, especially of mobile devices.
Reviewing cutting-edge techniques for conserving power and boosting power efficiency, the book examines various technologies and their impact on consumer devices.
It considers each technology, first by introducing the main physical layer components in recent wireless communication systems along with their shortcomings, and then proposing solutions for overcoming these shortcomings.
The book covers orthogonal frequency division multiplexing (OFDM) signal generation and formulation and examines the advantages and disadvantages of OFDM systems compared to alternative multiplexing. It introduces one of the main drawbacks of OFDM systems, peak-to-average power ratio (PAPR), and discusses several PAPR techniques.
It also explains how to overcome the main drawbacks of real-world OFDM system applications.
* Considers power amplifier linearization for increasing power efficiency and reducing system costs and power dissipation
* Describes the implementation scenario of the most promising linearization technique, digital predistortion
* Presents some experimental demonstrations of digital predistortion when the device under test is in the loop Because the most costly device in a communication system that has a direct impact on power efficiency and power consumption is the power amplifier, the book details the behavior and characteristics of different classes of power amplifiers.
Describing the evolution of the mobile cellular communication system, it details a cost-effective technique to help you increase power efficiency, reduce system costs, and prolong battery life in next generation mobile devices.

This book focuses on the study and development of one of the most advanced topics in broadband wireless communications systems: power efficiency and power consumption in wireless communications systems, especially of mobile devices. Hence, the main focus of this book is on the most recent techniques for the conservation of power and increase in power efficiency. This is an important topic that has been addressed in recent consumer electronics publications where the main challenge is to prolong the battery life of mobile devices and reduce the system costs. To achieve both of the aforementioned objec-tives in consumer devices, scrutinizing recent technologies and their impact on the consumer devices is vital. We will discuss each of these topics, first by introducing the main physical layer components in recent wireless communications systems and their shortcomings, and then proposing appropriate solutions to overcome these shortcomings.
Because the most costly device in a communication system that has a direct impact on power efficiency and power consumption is the power amplifier, we will study the behavior and characteristics of different classes of power amplifiers in detail. The subsequent topics will deal directly or indirectly to the power amplifiers. The nonlinear behavior of the power amplifier has made it an interesting research area for the last 50 years. Although the nonlinear characteristics of the power amplifer are known, developing its analytical model was a major challenge in the past. There are different power amplifier models that have been researched, including the Saleh model, Taylor series, Ghorbani model, Rapp model, Volterra series, and memory polynomial. The latter is the most optimum model that has been derived; it can be applied for a wide variety of power amplifiers in wireless communications systems. The main feature of this model is that it considers electrical or short-term memory effects. In this book, we will study and analyze this model as well.
This book is organized as follows: Chapter 1 introduces the mobile cellular communications system and reviews its evolution. It also discusses multiplexing techniques and the most optimum multi-plexing solution, which includes spectral efficiency and interference mitigation.
Chapter 2 examines orthogonal frequency division multiplexing (OFDM) signal generation and formulation. As the most recent mul-tiplexing technique, OFDM and its advantages and disadvantages are discussed.
Chapter 3 explains the power amplifier characteristics in wireless communications systems. It is the most costly device in communi-cations systems and its behavior needs to be understood. The main parameters that define a power amplifier, AM-AM and AM-PM, are introduced here and the challenge of nonlinearity and its impact on the output spectrum as well as in-band distortion are shown. Several classes of power amplifiers and the most reliable class in terms of linearity and efficiency are introduced.
In Chapter 4, one of the main drawbacks of OFDM systems, peak-to-average power ratio (PAPR), is introduced and several PAPR techniques are discussed. Moreover, simulation results of a new PAPR technique are included. Two of the most promising techniques, selected mapping and partial transmit sequences, are also presented and explained.
In Chapter 5, the implementation of an optimum PAPR tech-nique and its respective hardware platform is introduced. The main measurement parameter and comparison between simulations will be carried out.
Chapter 6 continues with an introduction to power amplifier lin-earization to increase power efficiency and hence save system costs and power dissipation. Different linearization techniques are introduced and a scheme to overcome the drawbacks of conventional techniques is also presented.
Chapter 7 describes the implementation scenario of digital predis-tortion, the most promising linearization technique.
Chapter 8 presents some experimental demonstrations of digital predistortion when the device under test (DUT) is in the loop.
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Preface xi

Chapter 1 Evolution Of Multiplexing Techniques In Wireless Communications Systems 1

1.1 Introduction 1

1.2 Evolution of Mobile Cellular Networks 2

      1.2.1 First-Generation Cellular Systems 2

      1.2.2 Second-Generation Cellular Systems 3

      1.2.3 Third-Generation Cellular Systems 3

      1.2.4 Future Broadband Wireless Communication 4

1.3 Evolution of Multiplexing Techniques 4

      1.3.1 Frequency Division Multiplexing Access (FDMA) Technique 4

      1.3.2 Time Division Multiplexing Access (TDMA) Technique 6

      1.3.3 Code Division Multiple Access (CDMA) Technique 6

      1.3.4 Orthogonal Frequency Division Multiplexing (OFDM) in 4G 6

      1.3.4.1 OFDM Pros and Cons 7

1.4 Key Technologies 8

      1.4.1 Generalized Frequency Division Multiplexing (GFDM) 8

      1.4.2 Multiple Input Multiple Output (MIMO) 8

      1.4.3 Space Time and Space Frequency Transmission over MIMO Networks 10

1.5 Summary 10

References 10

Chapter 2 Orthogonal Frequency Division Multiplexing Theory 11

2.1 Introduction 11

2.2 History of OFDM 12

2.3 OFDM Blocks 13

2.4 OFDM Mathematical Analysis and Measurements 15

2.5 Summary 19

References 21

Chapter 3 Power Amplifiers In Wireless Communications 23

3.1 Introduction 23

3.2 High Power Amplifiers 25

      3.2.1 Nonlinearity of Power Amplifiers 25

3.3 Characteristics of Power Amplifiers 27

      3.3.1 Efficiency 27

      3.3.1.1 Drain Efficiency 28

      3.3.1.2 Power-Added Efficiency (PAE) 28

      3.3.2 Output Power 28

      3.3.3 Signal Gain 29

      3.3.4 Trade-Off between Linearity and Efficiency 29

      3.3.5 Power Amplifier Two-Tone Test 31

3.4 Classification of Power Amplifiers 34

      3.4.1 Class A 35

      3.4.2 Class B 38

      3.4.3 Class AB 3

      3.4.4 Class C 39

      3.4.5 Class F 41

      3.4.6 Other High-Efficiency Classes 44

3.5 Power Amplifier Memory Effects 4

      3.5.1 Electrical Memory Effects 45

      3.5.2 Electrothermal Memory Effects 46

      3.5.3 Modeling Power Amplifiers 46

      3.5.4 Modeling Power Amplifiers without Memory 46

      3.5.5 Power Amplifier Model with Memory Effects 48

3.6 Power Amplifier Simulations 50

3.7 Summary 56

References 57

Chapter 4 Peak-To-Average Power Ratio 59

4.1 Introduction 59

4.2 The Effect of High PAPR on Power Amplifiers 65

4.3 PAPR Reduction Techniques 69

      4.3.1 Distortion-Based PAPR Reduction Techniques 71

      4.3.1.1 Clipping Method 71

      4.3.1.2 Windowing Method 73

      4.3.1.3 Companding Method 73

      4.3.2 Distortionless-Based PAPR Reduction Methods 74

      4.3.2.1 Coding Method 74

      4.3.2.2 Active Constellation Extension 75

      4.3.2.3 Partial Transmit Sequence 76

      4.3.2.4 Enhanced PTS 77

      4.3.2.5 Selected Mapping Method 80

      4.3.2.6 Tone Reservation Method 86

      4.3.2.7 Dummy Signal Insertion Method 86

      4.3.2.8 DSI-PTS 89

      4.3.2.9 DSI-EPTS 90

      4.3.3 A Discussion on the Current PAPR Reduction Solutions 93

4.4 Design of the Proposed DSI-SLM Scheme 94

      4.4.1 The Proposed DSI-SLM Scheme 95

      4.4.2 DSI-SLM Computational Complexity 101

4.5 Simulation Results and Analysis 105

4.6 Results Discussion 115

4.7 The Optimum Phase Sequence with the Dummy Sequence Insertion Scheme 117

      4.7.1 Design of the OPS-DSI Scheme 117

      4.7.2 System Performance of the OPS-DSI Scheme 125

      4.7.2.1 OPS-DSI Side Information 125

      4.7.2.2 Advantages and Disadvantages of the Proposed OPS-DSI Scheme 126

      4.7.2.3 OPS-DSI Computational Complexity 126

      4.7.2.4 Simulation Results and Analysis 127

      4.7.2.5 Results Discussion 130

4.8 Summary 131

References 132

Chapter 5 Peak-To-Average Power Ratio Implementation 141

5.1 Introduction 141

5.2 Software Implementation Design 142

      5.2.1 MATLAB Simulation Design 143

      5.2.2 C++ Implementation Design 143

      5.2.3 Implementation Platform 143

5.3 Hardware Complexity 144

5.4 Hardware Implementation 146

5.5 Field Programmable Gate Array 149

      5.5.1 The System Generator Tool 150

      5.5.2 System Generator Design Flow 150

5.6 The Prototype of the Dummy Signal Insertion with Selected Mapping Scheme 151

      5.6.1 The Inverse Fast Fourier Transform Prototype 151

      5.6.2 Using Acce1DSP Software to Prototype IFFT 153

      5.6.3 Prototype of the Conventional Selected Mapping Method 155

      5.6.4 Implementation of the DSI-SLM Scheme 156

      5.6.5 Hardware Resource Consumption 158

5.7 FPGA Implementation of the Optimum Phase Sequence with the Dummy Sequence Insertion Scheme 162

      5.7.1 Implementation of the OPS-DSI Transmitter 163

      5.7.2 Implementation of the OPS-DSI Receiver 168

5.8 Implementation of Complex Division in the Receiver 173

      5.8.1 Newton-Raphson Division 174

      5.8.2 Error Analysis 175

      5.8.3 Initial Approximation Techniques 175

      5.8.4 Hardware Structure of the Complex Divider 176

      5.8.5 Divisor Scaling 177

      5.8.6 Newton-Raphson Method 177

      5.8.7 Postscaling of Division Values 178

5.9 Hardware Resource Consumption of the OPS-DSI Scheme 181

5.10 Summary 181

References 182

Chapter 6 Power Amplifier Linearization 185

6.1 Introduction 185

6.2 Power Amplifier Linearization Techniques 189

      6.2.1 The Feedback Linearization Technique 189

      6.2.2 Linear Amplification with Nonlinear Components 190

      6.2.3 Feedforward Linearizers 191

      6.2.4 Predistortion Linearizers 192

      6.2.5 Digital Predistortion 192

      6.2.6 Memory Polynomial Predistortion 195

      6.2.7 Complex Gain Predistortion 196

      6.2.8 The Digital Predistortion Linearization Method 202

      6.2.9 Complex Gain Memory Predistortion 203

6.3 Simulation Results of Applying Complex Gain Memory Predistortion 211

6.4 Summary 223

References 224

Chapter 7 Digital Predistortion Implementation 227

7.1 Introduction 227

7.2 Simulation with Xilinx Blocksets 227

      7.2.1 System Generator 228

7.3 Xilinx Embedded Development Kit 228

7.4 Field Programmable Gate Array 229

      7.4.1 Description 230

      7.4.2 Functional Description 231

7.5 Complex Gain Memory Predistortion Implementation 231

      7.5.1 Complex Multiplier 232

      7.5.2 Lookup Table (LUT) 233

7.6 Complex Divider Implementation 234

7.7 Results of FPGA Implementation 236

7.8 Digital Signal Processing Implementation of Digital Predistortion 239

7.9 DP Block Design 239

      7.9.1 Linear Convergence Adaptation Algorithm 241

      7.9.2 Adaptation Block 243

      7.9.3 Complex Multiplier 244

      7.9.4 Saleh Model Amplifier 245

      7.9.5 The IQ512 Block 246

7.10 Summary 249

References 250

Chapter 8 Experimental Results 251

8.1 Introduction 251

8.2 Experimental Setup 251

8.3 Experimental Results 256

8.4 Comparison between Simulation and Experimental Results 258

8.5 Summary 264

References 264

Appendix A: Complex Baseband Representation Of Band-Pass Signals 267

Appendix B 273

Index 309

Pooria Varahram received his B.Sc. in electrical and electronics engineering from Khajenasir University of Technology in 2002, his M.Sc. in telecommunications engineering from Tarbiat Modares University in 2004, and Ph.D. in wireless communication engineering from the University of Putra Malaysia (UPM) in 2010. He has more than five years of experience in designing and developing a range of electronic and telecommunication-related projects. He has completed his Post PhD in UPM in 2012. He is now senior lecturer in UPM since January 2013. His research interests are PAPR reduction in OFDM systems, linearization of power amplifiers, and microwave power amplifier design.

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