Hybrid Beamforming for Millimeter-Wave Relay-Assisted MIMO Systems

다국어 초록 (Multilingual Abstract)

Conclusion and Future Work
The primary focus of the presented work in this thesis is to address the hybrid transceiver design for next
generation of mobile cellular networks. Keeping this perspective in view, an endeavor was made to propose
the low-complexity solution of hybrid precoding design for a single-user mmWave MIMO system by taking
into account the frequency selective channels. The concept of hybrid beamforming was applied on different
relay-assisted mmWave MIMO communication networks to extend the transmission range, network
coverage and the enhancement of spectral efficiency. The first hybrid beamforming design was proposed
for multi-user MIMO relay system under frequency selective channels. The second hybrid precoding design
was proposed in an attempt to combine the hybrid processing and relay selection strategy to maximize the
performance of system, when channel conditions are not favorable for reliable data transmission. The third
relay-assisted hybrid beamforming was designed by considering a single-user multi-relay MIMO system
under wideband assumption. These relay based architectures enable the mmWave MIMO network efficient
and reliable in outdoor environments. Computer simulations reveal that the proposed hybrid beamforming
algorithms show near-optimal performance under different system configuration parameters.
There is a definite need to address hybrid transceiver design problems by taking into account the estimation
of mmWave channel with acceptable level of accuracy while minimizing the computational burden
associated with this process. Deep learning models may have the potential to address this problem but they
require huge amount of data for training purpose and these algorithms shift the computational complexity
from real-time to off-line training. By exploiting the potential of deep learning frameworks, the
performance of the proposed algorithms for different relay-assisted MIMO networks may be improved and,
it may be considered as a promising future direction to extend the research work in this thesis.

목차 (Table of Contents)

• Chapter 1 Introduction 1
• 1.1 Scope and Main Objectives 3
• 1.2 Key Contributions 4
• 1.3 Organization of the Thesis 8
• Chapter 2 Background 9
• 2.1 Massive MIMO Systems 9
• 2.2 Millimeter-Wave Communications 10
• 2.3 Relay Networks 10
• 2.3.1 Full-Duplex Relay System 11
• 2.4 Millimeter-Wave Relay-Assisted Networks 13
• Chapter 3 Hybrid Wideband Transceiver Design in Millimeter-Wave Single-User
• MIMO System 14
• 3.1 Introduction 14
• 3.1.1 Related Work 15
• 3.1.2 Motivation 17
• 3.2 System Model and Tensor Fundamentals 17
• 3.2.1 System Model 17
• 3.2.2 Problem Formulation 18
• 3.2.3 Tensor Fundamentals 19
• 3.3 Proposed Algorithm-I: Analog Combining Using Multi-linear SVD and
• Analog Precoding with Optimal Phase Extraction for Gain Maximization of
• the Equivalent Baseband Channel 20
• 3.4 Algorithm-II: Analog RF Precoder/Combiner by Using Classification of
• Beamforming Vectors for Gain Maximization of the Equivalent Baseband
• Channel 24
• 3.5 Digital Baseband Processing 28
• 3.6 Complexity Analysis 29
• 3.7 Simulation Results and Discussion 32
• 3.8 Conclusion 38
• Chapter 4 Hybrid Beamforming in Wideband Multi-User MIMO Relay-Assisted
• Network 39
• 4.1 Introduction 39
• 4.2 System Model and Problem Formulation 43
• 4.3 Fully Digital Precoding 47
• 4.4 Analog Beamforming at Source, Relay Node and Destinations 49
• 4.4.1 Source Analog Precoder and Relay Analog Combiner 49
• 4.4.2 Relay Analog Precoder and Destination Analog
• Combiner 55
• 4.4.3 Low Complexity Analytic Solution of Relay Analog
• Precoder 58
• 4.5 Digital Baseband Processing 59
• 4.6 Complexity Analysis 61
• 4.7 Computer Simulations 62
• 4.7.1 Sum Spectral Efficiency Performance 63
• 4.7.2 Performance Evaluation with Number of Antennas at Source,
• Relay and Destinations 66
• 4.7.3 Sum Spectral Efficiency Performance with Number of Data
• Streams 66
• 4.7.4 Sum Spectral Efficiency with Number of Antennas at Source
• and Relay 68
• 4.7.5 Sum Spectral Efficiency Performance with Number of
• Users 69
• 4.7.6 Sum Spectral Efficiency Performance with Number of
• Antennas at Users 69
• 4.8 Conclusion 71
• Chapter 5 Hybrid Precoding and Relay Selection Mechanism in Single-User MultiRelay MIMO System 72
• 5.1 Introduction 72
• 5.2 System Model and Problem Formulation 76
• 5.3 Proposed Analog RF Beamforming Design 80
• 5.3.1 Source Analog Precoder ??? 80
• 5.3.2 Destination Analog RF Combiner ??? 81
• 5.3.3 Relay Analog RF Beamforming 83
• 5.3.3.1 Relay Analog Combiner ?1? 83
• 5.3.3.2 Relay Analog Precoder ?2? 84
• 5.3.3.3 Relay Selection Criteria 85
• 5.4 Digital Baseband Precoding and Combining 85
• 5.4.1 Complexity Analysis 87
• 5.5 Computer Simulations 89
• 5.5.1 Spectral Efficiency Evaluation with ULA and mm-Wave
• Channel 90
• 5.5.2 Spectral Efficiency Performance in Rich Scattering
• Environment 91
• 5.5.3 Spectral Efficiency Performance with UPA and mm-Wave
• Channel 94
• 5.5.4 Impact of Data Transmission Paths on Spectral
• Efficiency 94
• 5.6 Conclusion 96
• Chapter 6 Hybrid Beamforming in Millimeter-Wave Multi-Relay MIMO System
• Under Frequency Selective Channels 97
• 6.1 Introduction 97
• 6.2 System and channel models 99
• 6.3 Fully digital precoding and analog beamforming 103
• 6.3.1 Fully Digital Precoding 103
• 6.3.2 Algorithm-I: Analog Beamforming at Relay Nodes Using
• Multi-Linear SVD 105
• 6.3.3 Algorithm-II: Analog Beamforming at Relay Nodes Using
• Modified EGT for Optimal Phase Extraction 106
• 6.4 Digital Baseband Precoding and Combining 109
• 6.5 Complexity of Proposed Algorithms 110
• 6.6 Simulation Results 112
• 6.7 Conclusion 116
• Chapter 7 Conclusion and Future Work 117
• References 118
• Appedices 133