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mmWave Massive MIMO

mmWave Massive MIMO
A Paradigm for 5G

by Shahid Mumtaz,Jonathan Rodriguez,Linglong Dai

  • Publisher : Academic Press
  • Release : 2016-12-02
  • Pages : 372
  • ISBN : 0128044780
  • Language : En, Es, Fr & De
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mmWave Massive MIMO: A Paradigm for 5G is the first book of its kind to hinge together related discussions on mmWave and Massive MIMO under the umbrella of 5G networks. New networking scenarios are identified, along with fundamental design requirements for mmWave Massive MIMO networks from an architectural and practical perspective. Working towards final deployment, this book updates the research community on the current mmWave Massive MIMO roadmap, taking into account the future emerging technologies emanating from 3GPP/IEEE. The book's editors draw on their vast experience in international research on the forefront of the mmWave Massive MIMO research arena and standardization. This book aims to talk openly about the topic, and will serve as a useful reference not only for postgraduates students to learn more on this evolving field, but also as inspiration for mobile communication researchers who want to make further innovative strides in the field to mark their legacy in the 5G arena. Contains tutorials on the basics of mmWave and Massive MIMO Identifies new 5G networking scenarios, along with design requirements from an architectural and practical perspective Details the latest updates on the evolution of the mmWave Massive MIMO roadmap, considering future emerging technologies emanating from 3GPP/IEEE Includes contributions from leading experts in the field in modeling and prototype design for mmWave Massive MIMO design Presents an ideal reference that not only helps postgraduate students learn more in this evolving field, but also inspires mobile communication researchers towards further innovation

Analysis of Millimeter Wave and Massive MIMO Cellular Networks

Analysis of Millimeter Wave and Massive MIMO Cellular Networks
A Book

by Tianyang Bai

  • Publisher : Unknown Publisher
  • Release : 2016
  • Pages : 396
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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Millimeter wave (mmWave) communication and massive multiple-input multiple-output (MIMO) are promising techniques to increase system capacity in 5G cellular networks. The prior frameworks for conventional cellular systems do not directly apply to analyze mmWave or massive MIMO networks, as (i) mmWave cellular networks differ in the different propagation conditions and hardware constraints; and (ii) with a order of magnitude more antennas than conventional multi-user MIMO systems, massive MIMO systems will be operated in time-division duplex (TDD) mode, which renders pilot contamination a primary limiting factor. In this dissertation, I develop stochastic geometry frameworks to analyze the system-level performance of mmWave, sub-6 GHz massive MIMO, and mmWave massive MIMO cellular networks. The proposed models capture the key features of each technique, and allow for tractable signal-to-interference-plus-noise ratio (SINR) and rate analyses. In the first contribution, I develop an mmWave cellular network model that incorporates the blockage effect and directional beamforming, and analyze the SINR and rate distributions as functions of the base station density, blockage parameters, and antenna geometry. The analytical results demonstrate that with a sufficiently dense base station deployment, mmWave cellular networks are capable to achieve comparable SINR coverage and much higher rates than conventional networks. In my second contribution, I analyze the uplink SINR and rate in sub-6 GHz massive MIMO networks with the incorporation of pilot contamination and fractional power control. Based on the analysis, I show scaling laws between the number of antennas and scheduled users per cell that maintain the uplink signal-to-interference ratio (SIR) distributions are different for maximum ratio combining (MRC) and zero-forcing (ZF) receivers. In my third contribution, I extend the sub-6 GHz massive MIMO model to mmWave frequencies, by incorporating key mmWave features. I leverage the proposed model to investigate the asymptotic SINR performance, when the number of antennas goes to infinity. Numerical results show that mmWave massive MIMO outperforms its sub-6 GHz counterpart in cell throughput with a dense base station deployment, while the reverse can be true with a low base station density.

Hybrid Analog/digital Signal Processing for MmWave Massive-MIMO Communications

Hybrid Analog/digital Signal Processing for MmWave Massive-MIMO Communications
A Book

by Alireza Morsali

  • Publisher : Unknown Publisher
  • Release : 2021
  • Pages : 329
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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"Massive multiple-input multiple-output (MIMO) and millimeter-wave (mmWave) communications are established as key technologies for fifth generation (5G) and beyond (5G\&B) networks. However, the practical implementation of mmWave massive-MIMO systems remains challenging. Conventional MIMO systems are implemented using the fully-digital (FD) architecture, in which signal processing is performed in the digital domain by means of dedicated processors and/or digital circuitry. At the transmitter, the digital baseband output signals are then converted to analog signals for transmission, which requires a dedicated radio frequency (RF) chain per antenna element. For the large-scale antenna arrays envisaged for massive-MIMO systems, however, the FD architecture is impractical due to the huge power consumption and production costs.One the most effective solutions to this problem is hybrid analog/digital (A/D) beamforming (HBF). In this approach, an additional signal processing layer in the analog domain, referred to as analog beamformer, is added between the RF chains and the antenna elements. In effect, by properly designing the analog beamformer, it becomes possible to reduce the number of RF chains while achieving a performance comparable to the FD architecture.There are three parts to this thesis all of which have a common goal, which is to achieve the performance of FD systems with HBF. In the first part, we consider HBF at the transmitter side and study the minimum number of required RF chains for realizing a given FD~precoder with the \hp~architecture. We further investigate HBF designs based on the single RF chain architecture for mmWave massive-MIMO systems. We present three novel beamformer designs which achieve the performance of FD precoding systems. Finally, we extend these results to MIMO-OFDM systems.The second part studies HBF at the receiver. Particularly, we propose a novel hybrid structure for realizing a given FD combiner with the minimum number of required RF chains.We then focus on a more practical scenario where phase-shifters can realize a finite number of phase angles. Accordingly, we propose a modified hybrid structure by introducing an additional degree of freedom, i.e., phase-offset between the finite-resolution phase-shifts and optimize this parameter via close approximations. Robust hybrid combiners are then studied for the case of imperfect channel knowledge at the receiver.In the final part of this thesis, we explore the hybrid A/D structure as a general framework for signal processing in massive and ultra-massive-MIMO systems. To exploit the full potential of the analog domain, we first focus on the analog signal processing (ASP) network. We investigate a mathematical representation suitable for any arbitrarily connected feed-forward ASP network comprised of the common RF hardware elements in the context of hybrid A/D systems, i.e., phase-shifter and power-divider/combiner. A novel ASP structure is then proposed which is not bound to the unit modulus constraint, thereby facilitating the hybrid A/D systems design. We then study MIMO transmitter and receiver designs to exploit the full potential of digital processing as well.An optimization model based on the proposed structure is presented that can be used for hybrid A/D system design. Finally, precoding and combining designs under different conditions are discussed as examples"--

Mmwave Massive Mimo

Mmwave Massive Mimo
A Paradigm for 5g

by Shahid Mumtaz,Linglong Dai,Jonathan Rodriguez

  • Publisher : Academic Press
  • Release : 2016-11-01
  • Pages : 475
  • ISBN : 9780128044186
  • Language : En, Es, Fr & De
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"mmWave Massive MIMO: A Paradigm for 5G" is the first book of its kind to hinge together related discussions on mmWave and Massive MIMO under the umbrella of 5G networks. New networking scenarios are identified, along with fundamental design requirements for mmWave Massive MIMO networks from an architectural and practical perspective. Working towards final deployment, this book updates the research community on the current mmWave Massive MIMO roadmap, taking into account the future emerging technologies emanating from 3GPP/IEEE. The book's editors draw on their vast experience in international research on the forefront of the mmWave Massive MIMO research arena and standardization. This book aims to talk openly about the topic, and will serve as a useful reference not only for postgraduates students to learn more on this evolving field, but also as inspiration for mobile communication researchers who want to make further innovative strides in the field to mark their legacy in the 5G arena. Contains tutorials on the basics of mmWave and Massive MIMOIdentifies new 5G networking scenarios, along with design requirements from an architectural and practical perspectiveDetails the latest updates on the evolution of the mmWave Massive MIMO roadmap, considering future emerging technologies emanating from 3GPP/IEEEIncludes contributions from leading experts in the field in modeling and prototype design for mmWave Massive MIMO designPresents an ideal reference that not only helps postgraduate students learn more in this evolving field, but also inspires mobile communication researchers towards further innovation

Massive MIMO in 5G Networks: Selected Applications

Massive MIMO in 5G Networks: Selected Applications
A Book

by Long Zhao,Hui Zhao,Kan Zheng,Wei Xiang

  • Publisher : Springer
  • Release : 2017-12-21
  • Pages : 93
  • ISBN : 3319684094
  • Language : En, Es, Fr & De
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This SpringerBrief focuses mainly on the basic theory and applications of massive MIMO in 5G networks. The significance of massive MIMO for 5G or future communications is first briefly discussed. Then, the basic theory of massive MIMO technology is comprehensively analyzed, i.e., a variety of 5G scenarios and their improvements are described when massive MIMO is taken into account. Art physical-layer techniques and various networking techniques for interference mitigation and resource scheduling are introduced as well. This SpringerBrief also examines the selected applications of massive MIMO in 5G networks, i.e., massive MIMO-aided millimeter communications and energy transfer. The physical-layer design, multiple access control (MAC) mechanism and networking techniques are discussed for millimeter-wave communications aided by massive MIMO technology. Then, massive MIMO is covered for hybrid information and energy transfer. A downlink precoder and a uplink pilot scheme is proposed for single cell networks, and both non-cooperative and cooperative energy transfer in multi-cell are presented. Communication researchers in the area of MIMO technology, as well as researchers and practitioners working in millimeter communications and energy transfer seeking new research topics, and topic areas with communication system design, centralized and distributed algorithms, will find this brief useful as a reference. Advanced-level students studying communication engineering will also find this book useful as a secondary text.

Channel Estimation for Millimeter Wave Massive MIMO Communication

Channel Estimation for Millimeter Wave Massive MIMO Communication
A Book

by You You

  • Publisher : Unknown Publisher
  • Release : 2020
  • Pages : 329
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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5G Physical Layer Technologies

5G Physical Layer Technologies
A Book

by Mosa Ali Abu-Rgheff

  • Publisher : John Wiley & Sons
  • Release : 2019-09-17
  • Pages : 592
  • ISBN : 1119525497
  • Language : En, Es, Fr & De
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Written in a clear and concise manner, this book presents readers with an in-depth discussion of the 5G technologies that will help move society beyond its current capabilities. It perfectly illustrates how the technology itself will benefit both individual consumers and industry as the world heads towards a more connected state of being. Every technological application presented is modeled in a schematic diagram and is considered in depth through mathematical analysis and performance assessment. Furthermore, published simulation data and measurements are checked. Each chapter of 5G Physical Layer Technologies contains texts, mathematical analysis, and applications supported by figures, graphs, data tables, appendices, and a list of up to date references, along with an executive summary of the key issues. Topics covered include: the evolution of wireless communications; full duplex communications and full dimension MIMO technologies; network virtualization and wireless energy harvesting; Internet of Things and smart cities; and millimeter wave massive MIMO technology. Additional chapters look at millimeter wave propagation losses caused by atmospheric gases, rain, snow, building materials and vegetation; wireless channel modeling and array mutual coupling; massive array configurations and 3D channel modeling; massive MIMO channel estimation schemes and channel reciprocity; 3D beamforming technologies; and linear precoding strategies for multiuser massive MIMO systems. Other features include: In depth coverage of a hot topic soon to become the backbone of IoT connecting devices, machines, and vehicles Addresses the need for green communications for the 21st century Provides a comprehensive support for the advanced mathematics exploited in the book by including appendices and worked examples Contributions from the EU research programmes, the International telecommunications companies, and the International standards institutions (ITU; 3GPP; ETSI) are covered in depth Includes numerous tables and illustrations to aid the reader Fills the gap in the current literature where technologies are not explained in depth or omitted altogether 5G Physical Layer Technologies is an essential resource for undergraduate and postgraduate courses on wireless communications and technology. It is also an excellent source of information for design engineers, research and development engineers, the private-public research community, university research academics, undergraduate and postgraduate students, technical managers, service providers, and all professionals involved in the communications and technology industry.

Hybrid Precoding Algorithms for Millimeter-wave Massive MIMO Systems

Hybrid Precoding Algorithms for Millimeter-wave Massive MIMO Systems
A Book

by Osama Alluhaibi

  • Publisher : Unknown Publisher
  • Release : 2018
  • Pages : 329
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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Cell-free Massive MIMO and Millimeter Wave Channel Modelling for 5G and Beyond

Cell-free Massive MIMO and Millimeter Wave Channel Modelling for 5G and Beyond
A Book

by Manijeh Bashar

  • Publisher : Unknown Publisher
  • Release : 2019
  • Pages : 329
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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Low Complexity NOMA Design for Millimeter-Wave Massive MIMO System

Low Complexity NOMA Design for Millimeter-Wave Massive MIMO System
A Book

by 邱奕棠

  • Publisher : Unknown Publisher
  • Release : 2018
  • Pages : 88
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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Power Detector Circuits for Transmitters in a Millimeter-wave Massive MIMO System

Power Detector Circuits for Transmitters in a Millimeter-wave Massive MIMO System
A Book

by Anonim

  • Publisher : Unknown Publisher
  • Release : 2015
  • Pages : 329
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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Millimeter Wave and Massive MIMO Communications for Next-generation Wireless Systems

Millimeter Wave and Massive MIMO Communications for Next-generation Wireless Systems
A Book

by Ahmed Abulkareem Nageeb Youssef Alkhateeb

  • Publisher : Unknown Publisher
  • Release : 2016
  • Pages : 448
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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Multiple-input multiple-output (MIMO) communication is expected to play a central role in future wireless systems through the deployment of a large number of antennas at the transmitters and receivers. In low-frequency systems, massive MIMO offers high multiplexing gains that boost system spectral efficiency. In millimeter wave (mmWave) systems, the deployment of large antenna arrays at both the base station and mobile users is necessary to guarantee sufficient received signal power. Realizing these systems in practice, however, requires addressing several key challenges: (i) fully-digital solutions are costly and power hungry, (ii) channel training and estimation process has high overhead, and (iii) precoders design optimization problems are non-trivial. In this dissertation, precoding and channel estimation strategies that address these challenges are proposed for both mmWave and massive MIMO systems. The proposed solutions adopt hybrid analog/digital architectures that divide precoding/combining processing between RF and baseband domains and lead to savings in cost and power consumption. Further, the developed techniques leverage the structure and characteristics of mmWave and massive MIMO channels to reduce the training overhead and precoders design complexity. The main contributions of this dissertation are (i) developing a channel estimation solution for hybrid architecture based mmWave systems, exploiting the sparse nature of the mmWave channels, (ii) designing hybrid precoding algorithm for multi-user mmWave and massive MIMO systems, (iii) proposing a multi-layer precoding framework for massive MIMO cellular systems, and (iv) developing hybrid precoding and codebook solutions for frequency selective mmWave systems. Mathematical analysis as well as numerical simulations illustrate the promising performance of the proposed solutions, marking them as enabling technologies for mmWave and massive MIMO systems.

Massive MIMO and Millimeter Wave Communications for 5G and Beyond Wireless Systems

Massive MIMO and Millimeter Wave Communications for 5G and Beyond Wireless Systems
A Book

by Bohan Zhang

  • Publisher : Unknown Publisher
  • Release : 2020
  • Pages : 173
  • ISBN : 9781392574072
  • Language : En, Es, Fr & De
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In massive MIMO, with a large number of antennas deployed at the base station, many mobile stations can be served simultaneously via multiuser beamforming over the same frequency band. With the high spatial resolution in massive MIMO, simple linear precoding (e.g., zero-forcing) can achieve almost optimal performance. In millimeter wave communications, the large available spectrum can easily support bandwidths of 1 GHz, which can enable gigabit-per-second data rates. In this dissertation, we study several challenging problems in massive MIMO and millimeter wave communications.

Spatial Modulation Schemes and Modem Architectures for Millimeter Wave Radio Systems

Spatial Modulation Schemes and Modem Architectures for Millimeter Wave Radio Systems
A Book

by Ahmed Raafat

  • Publisher : Unknown Publisher
  • Release : 2020
  • Pages : 158
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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The rapid growth of wireless industry opens the door to several use cases such as internet of things and device-to-device communications, which require boosting the reliability and the spectral efficiency of the wireless access network, while reducing the energy consumption at the terminals. The vast spectrum available in millimeter-wave (mmWave) frequency band is one of the most promising candidates to achieve high-speed communications. However, the propagation of the radio signals at high carrier frequencies suffers from severe path-loss which reduces the coverage area. Fortunately, the small wavelengths of the mmWave signals allow packing a large number of antennas not only at the base station (BS) but also at the user terminal (UT). These massive antenna arrays can be exploited to attain high beamforming and combining gains and overcome the path-loss associated with the mmWave propagation. In conventional (fully digital) multiple-input-multiple-output (MIMO) transceivers, each antenna is connected to a specific radio-frequency (RF) chain and high resolution analog-to-digital-converter. Unfortunately, these devices are expensive and power hungry especially at mmWave frequency band and when operating in large bandwidths. Having this in mind, several MIMO transceiver architectures have been proposed with the purpose of reducing the hardware cost and the energy consumption.Fully connected hybrid analog and digital precoding schemes were proposed in with the aim of replacing some of the conventional RF chains by energy efficient analog devices. These fully connected mapping requires many analog devices that leads to non-negligible energy consumption. Partially connected hybrid architectures have been proposed to improve the energy efficiency of the fully connected transceivers by reducing the number of analog devices. Simplifying the transceiver's architecture to reduce the power consumption results in a degradation of the attained spectral efficiency.In this PhD dissertation, we propose novel modulation schemes and massive MIMO transceiver design to combat the challenges at the mmWave cellular systems. The structure of the doctoral manuscript can be expressed asIn Chapter 1, we introduce the transceiver design challenges at mmWave cellular communications. Then, we illustrate several state of the art architectures and highlight their limitations. After that, we propose scheme that attains high-energy efficiency and spectrum efficiency. In chapter 2, first, we mathematically describe the state of the art of the SM and highlight the main challenges with these schemes when applied at mmWave frequency band. In order to combat these challenges (for example, high cost and high power consumption), we propose novel SM schemes specifically designed for mmWave massive MIMO systems. After that, we explain how these schemes can be exploited in attaining energy efficient UT architecture. Finally, we present the channel model, systems assumptions and the transceiver devices power consumption models.In chapter 3, we consider single user SM system. First, we propose downlink (DL) receive SM (RSM) scheme where the UT can be implemented with single or multiple radio-frequency chains and the BS can be fully digital or hybrid architecture. Moreover, we consider different precoders at the BS and propose low complexity and efficient antenna selection schemes for narrowband and wideband transmissions. After that, we propose joint uplink-downlink SM scheme where we consider RSM in the DL and transmit SM (TSM) in the UL based on energy efficient hybrid UT architecture.In chapter 4, we extend the SM system to the multi-user case. Specifically, we develop joint multi-user power allocation, user selection and antenna selection algorithms for the broadcast and the multiple access channels.Chapter 5 is presented for concluding the thesis and proposing future research directions.

Hybrid Massive MIMO Precoding in Cloud-RAN

Hybrid Massive MIMO Precoding in Cloud-RAN
A Book

by Tho Le-Ngoc,Ruikai Mai

  • Publisher : Springer
  • Release : 2018-11-28
  • Pages : 149
  • ISBN : 3030021580
  • Language : En, Es, Fr & De
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This book covers the design and optimization of hybrid RF-baseband precoding for massive multiple-input multiple-output (MIMO)-enabled cloud radio access networks (RANs), where use cases such as millimeter-wave wireless backhauling, fully-loaded cellular networks are of interest. The suitability and practical implementation of the proposed precoding solutions for the Cloud RAN architecture are also discussed. Novel techniques are examined for RF precoding optimization in combination with nonlinear precoding at baseband, and the superiority of joint RF-baseband design is verified. Moreover, the efficacy of hybrid RF-baseband precoding to combat intercell interference in a multi-cell environment with universal frequency reuse is investigated, which is concluded to be a promising enabler for the dense deployment of base stations. This book mainly targets researchers and engineers interested in the challenges, optimization, and implementation of massive MIMO precoding in 5G Cloud RAN. Graduate students in electrical engineering and computer science interested in the application of mathematical optimization to model and solve precoding problems in massive MIMO cellular systems will also be interested in this book.

Generalized Spatial Modulation with Massive MIMO Over MmWave Channel for Next Generation Wireless Communication Systems

Generalized Spatial Modulation with Massive MIMO Over MmWave Channel for Next Generation Wireless Communication Systems
A Book

by Liang Kai Chang

  • Publisher : Unknown Publisher
  • Release : 2015
  • Pages : 329
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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5G Mobile Communications

5G Mobile Communications
A Book

by Wei Xiang,Kan Zheng,Xuemin (Sherman) Shen

  • Publisher : Springer
  • Release : 2016-10-13
  • Pages : 691
  • ISBN : 3319342088
  • Language : En, Es, Fr & De
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This book provides a comprehensive overview of the emerging technologies for next-generation 5G mobile communications, with insights into the long-term future of 5G. Written by international leading experts on the subject, this contributed volume covers a wide range of technologies, research results, and networking methods. Key enabling technologies for 5G systems include, but are not limited to, millimeter-wave communications, massive MIMO technology and non-orthogonal multiple access. 5G will herald an even greater rise in the prominence of mobile access based upon both human-centric and machine-centric networks. Compared with existing 4G communications systems, unprecedented numbers of smart and heterogeneous wireless devices will be accessing future 5G mobile systems. As a result, a new paradigm shift is required to deal with challenges on explosively growing requirements in mobile data traffic volume (1000x), number of connected devices (10–100x), typical end-user data rate (10–100x), and device/network lifetime (10x). Achieving these ambitious goals calls for revolutionary candidate technologies in future 5G mobile systems. Designed for researchers and professionals involved with networks and communication systems, 5G Mobile Communications is a straightforward, easy-to-read analysis of the possibilities of 5G systems.

A Genetic Algorithm for Channel Estimation in Switch-based Hybrid Analog/digital MmWave Massive MIMO Systems

A Genetic Algorithm for Channel Estimation in Switch-based Hybrid Analog/digital MmWave Massive MIMO Systems
A Book

by Alec Poulin

  • Publisher : Unknown Publisher
  • Release : 2020
  • Pages : 329
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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"Massive MIMO is one of the main technologies proposed to meet the stringent requirements of the upcoming 5G standard for wireless communications. However, the cost and the energy consumption of the RF chains in massive MIMO systems precludes the use of a traditional scheme where each antenna is equipped with one RF chain. This has lead to the introduction of hybrid analog/digital systems, where an analog module between the antennas and the digital baseband processor allows a reduced number of RF chains.This thesis addresses the problem of pilot-based channel estimation in hybrid analog/digital massive MIMO systems for future mmWave communications. To further reduce system cost and implementation complexity of the analog module, we consider an alternative architecture derived from RF switches as opposed to the phase shifters in the conventional literature. The estimation problem is modelled as a combinatorial optimization problem where the aim is to minimize the MSE between the real channel and the estimated channel over a finite set of allowed values for the switches. To solve the estimation problem, a GA is developed for the novel switch-based hybrid analog/digital massive MIMO architecture. Simulations of MIMO transmission over realistic mmWave channel models show that the proposed GA is able to estimate channels as accurately as, if not more than, an existing solution using phase shifters"--

Massive MIMO Millimeter Wave Channel Estimation and Localization

Massive MIMO Millimeter Wave Channel Estimation and Localization
A Book

by Macey Charles Ruble

  • Publisher : Unknown Publisher
  • Release : 2018
  • Pages : 110
  • ISBN : 9876543210XXX
  • Language : En, Es, Fr & De
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Cell-Free Massive MIMO

Cell-Free Massive MIMO
Scalability, Signal Processing and Power Control

by Giovanni Interdonato

  • Publisher : Linköping University Electronic Press
  • Release : 2020-09-09
  • Pages : 75
  • ISBN : 9179298087
  • Language : En, Es, Fr & De
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The fifth generation of mobile communication systems (5G) is nowadays a reality. 5G networks are been deployed all over the world, and the first 5G-capable devices (e.g., smartphones, tablets, wearable, etc.) are already commercially available. 5G systems provide unprecedented levels of connectivity and quality of service (QoS) to cope with the incessant growth in the number of connected devices and the huge increase in data-rate demand. Massive MIMO (multiple-input multiple-output) technology plays a key role in 5G systems. The underlying principle of this technology is the use of a large number of co-located antennas at the base station, which coherently transmit/receive signals to/from multiple users. This signal co-processing at multiple antennas leads to manifold benefits: array gain, spatial diversity and spatial user multiplexing. These elements enable to meet the QoS requirements established for the 5G systems. The major bottleneck of massive MIMO systems as well as of any cellular network is the inter-cell interference, which affects significantly the cell-edge users, whose performance is already degraded by the path attenuation. To overcome these limitations and provide uniformly excellent service to all the users we need a more radical approach: we need to challenge the cellular paradigm. In this regard, cell-free massive MIMO constitutes the paradigm shift. In the cell-free paradigm, it is not the base station surrounded by the users, but rather it is each user being surrounded by smaller, simpler, serving base stations referred to as access points (APs). In such a system, each user experiences being in the cell-center, and it does not experience any cell boundaries. Hence, the terminology cell-free. As a result, users are not affected by inter-cell interference, and the path attenuation is significantly reduced due to the presence of many APs in their proximity. This leads to impressive performance. Although appealing from the performance viewpoint, the designing and implementation of such a distributed massive MIMO system is a challenging task, and it is the object of this thesis. More specifically, in this thesis we study: Paper A) The large potential of this promising technology in realistic indoor/outdoor scenarios while also addressing practical deployment issues, such as clock synchronization among APs, and cost-efficient implementations. We provide an extensive description of a cell-free massive MIMO system, emphasizing strengths and weaknesses, and pointing out differences and similarities with existing distributed multiple antenna systems, such as Coordinated MultiPoint (CoMP). Paper B) How to preserve the scalability of the system, by proposing a solution related to data processing, network topology and power control. We consider a realistic scenario where multiple central processing units serve disjoint subsets of APs, and compare the spectral efficiency provided by the proposed scalable framework with the canonical cell-free massive MIMO and CoMP. Paper C) How to improve the spectral efficiency (SE) in the downlink (DL), by devising two distributed precoding schemes, referred to as local partial zero-forcing (ZF) and local protective partial ZF, that provide an adaptable trade-off between interference cancelation and boosting of the desired signal, with no additional front-haul overhead, and that are implementable by APs with very few antennas. We derive closed-form expressions for the achievable SE under the assumption of independent Rayleigh fading channel, channel estimation error and pilot contamination. These closed-form expressions are then used to devise optimal max-min fairness power control. Paper D) How to further improve the SE by letting the user estimate the DL channel from DL pilots, instead of relying solely on the knowledge of the channel statistics. We derive an approximate closed-form expression of the DL SE for conjugate beamforming (CB), and assuming independent Rayleigh fading. This expression accounts for beamformed DL pilots, estimation errors and pilot contamination at both the AP and the user side. We devise a sequential convex approximation algorithm to globally solve the max-min fairness power control optimization problem, and a greedy algorithm for uplink (UL) and DL pilot assignment. The latter consists in jointly selecting the UL and DL pilot pair, for each user, that maximizes the smallest SE in the network. Paper E) A precoding scheme that is more suitable when only the channel statistics are available at the users, referred to as enhanced normalized CB. It consists in normalizing the precoding vector by its squared norm in order to reduce the fluctuations of the effective channel seen at the user, and thereby to boost the channel hardening. The performance achieved by this scheme is compared with the CB scheme with DL training (described in Paper D). Paper F) A maximum-likelihood-based method to estimate the channel statistics in the UL, along with an accompanying pilot transmission scheme, that is particularly useful in line-of-sight operation and in scenarios with resource constraints. Pilots are structurally phase-rotated over different coherence blocks to create an effective statistical distribution of the received pilot signal that can be efficiently exploited by the AP when performing the proposed estimation method. The overall conclusion is that cell-free massive MIMO is not a utopia, and a practical, distributed, scalable, high-performance system can be implemented. Today it represents a hot research topic, but tomorrow it might represent a key enabler for beyond-5G technology, as massive MIMO has been for 5G. La quinta generazione dei sistemi radiomobili cellulari (5G) è oggi una realtà. Le reti 5G si stanno diffondendo in tutto il mondo e i dispositivi 5G (ad esempio smartphones, tablets, indossabili, ecc.) sono già disponibili sul mercato. I sistemi 5G garantiscono livelli di connettività e di qualità di servizio senza precedenti, per fronteggiare l’incessante crescita del numero di dispositivi connessi alla rete e della domanda di dati ad alta velocità. La tecnologia Massive MIMO (multiple-input multiple-output) riveste un ruolo fondamentale nei sistemi 5G. Il principio alla base di questa tecnologia è l’impiego di un elevato numero di antenne collocate nella base station (stazione radio base) le quali trasmettono/ricevono segnali, in maniere coerente, a/da più terminali utente. Questo co-processamento del segnale da parte di più antenne apporta molteplici benefici: guadagno di array, diversità spaziale e multiplazione degli utenti nel dominio spaziale. Questi elementi