Coherent Cooperative Relaying in Low Mobility Wireless Multiuser Networks PDF Download
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Author: Stefan Berger
Publisher: Logos Verlag Berlin GmbH
ISBN: 383252536X
Category :
Languages : en
Pages : 337
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Book Description
In this thesis, several important aspects of cooperative wireless multiuser networks are investigated. The focus lies on coherent two-hop relaying networks where several amplify-and-forward (AF) relays assist the communication between multiple source-destination pairs. First, the impact of local oscillator (LO) imperfections and I/Q imbalance at the relays on two-hop relaying is investigated. A special focus lies on the comparison between frequency division duplexing (FDD) and time division duplexing (TDD) relays. Based on the observation that the direction in which a channel between two wireless nodes is measured has an impact on the estimate, phase synchronization requirements for coherent relaying networks are then found. Several channel estimation protocols that differ in the direction in which the single-hop channels are measured are furthermore identi'ed and their performance is compared. Next, a very simple phase synchronization scheme is presented that provides a set of relays with a common LO phase. Two coherent beamforming schemes, namely multiuser zero-forcing (MUZF) and multiuser minimum mean squared error (MMSE) relaying, are then investigated. Finally, a real-world demonstrator for distributed wireless communication networks (called RACooN Lab) is presented. It was used to implement coherent cooperative communication schemes on a practical two-hop relaying network.
Author: Stefan Berger
Publisher: Logos Verlag Berlin GmbH
ISBN: 383252536X
Category :
Languages : en
Pages : 337
Get Book Here
Book Description
In this thesis, several important aspects of cooperative wireless multiuser networks are investigated. The focus lies on coherent two-hop relaying networks where several amplify-and-forward (AF) relays assist the communication between multiple source-destination pairs. First, the impact of local oscillator (LO) imperfections and I/Q imbalance at the relays on two-hop relaying is investigated. A special focus lies on the comparison between frequency division duplexing (FDD) and time division duplexing (TDD) relays. Based on the observation that the direction in which a channel between two wireless nodes is measured has an impact on the estimate, phase synchronization requirements for coherent relaying networks are then found. Several channel estimation protocols that differ in the direction in which the single-hop channels are measured are furthermore identi'ed and their performance is compared. Next, a very simple phase synchronization scheme is presented that provides a set of relays with a common LO phase. Two coherent beamforming schemes, namely multiuser zero-forcing (MUZF) and multiuser minimum mean squared error (MMSE) relaying, are then investigated. Finally, a real-world demonstrator for distributed wireless communication networks (called RACooN Lab) is presented. It was used to implement coherent cooperative communication schemes on a practical two-hop relaying network.
Author: Henry Ruben Lucas Schulten
Publisher: Logos Verlag Berlin GmbH
ISBN: 3832555862
Category : Technology & Engineering
Languages : en
Pages : 198
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Book Description
Body-centric wireless sensor networks are expected to enable future technologies such as medical in-body micro robots or unobtrusive smart textiles. These technologies may advance personalized healthcare as they allow for tasks such as minimally invasive surgery, in-body diagnosis, and continuous activity recognition. However, the localization of individual sensor nodes within such networks or the determination of the entire network topology still pose challenges that need to be solved. This work provides both theoretic and simulative insights to enable the required sub-millimeter localization accuracy of such sensors using magneto-inductive networks. It identifies inherent localization issues such as the asymmetry of the position estimation in magneto-inductive networks and outlines how such issues may be addressed by using passive relays or cooperation. It further proposes a novel approach to recognize the entire structure of a magneto-inductive network using simple impedance measurements and clusters of passive tags. This approach is evaluated extensively by simulation and experiment to demonstrate the feasibility of low-cost human body posture recognition.
Author: Gregor Dumphart
Publisher: Logos Verlag Berlin GmbH
ISBN: 3832554831
Category : Technology & Engineering
Languages : en
Pages : 261
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Book Description
Utilizing magnetic induction for wireless communication, wireless powering, passive relaying, and localization could enable massive wireless sensor applications with tiny nodes in challenging media, foremost biomedical in-body sensor networks. This work investigates the performance limits of these unique wireless systems with hardly any assumptions. As a foundation, a general system model and an interface to communication theory are developed. A major part of this work identifies two crucial magneto-inductive fading channels: that between randomly oriented coils and that caused by a nearby swarm of resonant passive relay coils. The analysis yields important technological implications. Based thereon, an investigation of wirelessly-powered in-body sensors is conducted, revealing their active and passive data transmission capabilities. Finally, a treatise of magneto-inductive node localization develops algorithms that perform near identified accuracy limits in theory and practice.
Author: Georgios Psaltopoulos
Publisher: Logos Verlag Berlin GmbH
ISBN: 3832528245
Category : Technology & Engineering
Languages : en
Pages : 203
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Book Description
Author: Celal Eşli
Publisher: Logos Verlag Berlin
ISBN: 9783832524845
Category : Electrical engineering
Languages : en
Pages : 0
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Book Description
Employing multiple antennas at the transmitter and receiver sides has been identified as the key enabler for high spectral efficiency in point-to-point communication, since it facilitates multiplexing of several data streams in space rather than in time/frequency. In this work, we are interested in achieving spatial multiplexing through efficient cooperative relaying schemes, even if both the transmit and receive antennas are distributed. To this end, we focus on wireless multiuser networks and aim at designing novel cooperative communication protocols, developing corresponding transmission and signal processing techniques, and optimizing the network performance.In the first part, we consider coherent multiuser amplify-and-forward (AF) relaying, where a set of source-destination (S-D) terminal pairs communicate concurrently over the same physical channel and a set of AF relay nodes assist the communication in a half-duplex scheme. We study various relay gain allocation schemes and system imperfections such as phase-noise and noisy channel estimates; investigate the necessary amount of channel information at relays and distributed computation of relay gains; and finally propose clustered relays networks.We shift our focus to decode-and-forward (DF) relaying in the second part, and address both multiuser one- and two-way multiple-input multiple-output (MIMO) relaying. First we consider two MIMO terminals exchanging information via a single MIMO relay node, and then, extend this scenario to the case of simultaneous MIMO communication of multiple S-D pairs. Therein, we investigate achievable rate regions, propose various relay transmit covariance optimizations, and consider channel estimation uncertainty.
Author: Lifeng Lai
Publisher:
ISBN:
Category : Computer networks
Languages : en
Pages : 152
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Book Description
Abstract: The presence of multiple users in the wireless network offers users with an opportunity to cooperate. Adopting tools from network information theory, this thesis investigates the utilities of user cooperation under various scenarios and examines the validity of cooperation assumption in energy limited networks. We first consider the construction of cooperation strategies for a wireless network composed of three nodes and limited by half-duplex and total power constraints. We show that noisy feedback plays a crucial role in devising efficient cooperation schemes for various channels. For the relay channel, we propose a new cooperation scheme that exploits the wireless feedback gain. Our analysis of the achievable rate of this scheme reveals the diminishing feedback gain at both the low and high signal-to-noise ratio regimes. Inspired by the proposed feedback strategy, we identify a greedy cooperation framework applicable to both the multicast and three-way channels. Our performance analysis reveals the asymptotic optimality of the proposed greedy approach in the wireless network setting. We then establish the utility of user cooperation in facilitating secure wireless communications. In particular, the four-terminal relay-eavesdropper channel is introduced and an outer-bound on the optimal rate-equivocation region is derived. Several cooperation strategies are then devised and the corresponding achievable rate-equivocation regions are characterized. The gain offered by the proposed cooperation strategies is then proved theoretically and validated numerically in the Additive White Gaussian Noise channel. We also examine user cooperation from game theoretic perspective. Using game theoretic framework, the critical role of altruistic nodes in encouraging cooperation is established, both for small and large scale networks. In a small network, where nodes utilize decode-and-forward scheme to cooperate, we show that a relay node, with appropriate strategy and location, successfully turns the Nash Equilibrium from no-cooperation to full-cooperation. In the large scale network, we show that it is sufficient to have a vanishingly small fraction of the nodes to be altruistic, i.e., relay nodes, in order to ensure full cooperation from all the nodes in the network.
Author: Etienne Auger
Publisher: Logos Verlag Berlin GmbH
ISBN: 3832532099
Category : Computers
Languages : en
Pages : 262
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Book Description
This book details promising communication schemes and channel modeling for a pervasive wireless access network (PWAN). Such a network is formed by nodes equipped with heterogeneous antenna arrangements and placed up to 10 m apart from each other. Nodes can be static when they belong to the infrastructure or have limited mobility when they are carried by a person. This scenario is extremely interesting for relay-based applications and fills the gap between the body area network that has a coverage up to 1 m and the wireless local area network that has a coverage up to 100 m. When a PWAN is jointly considered with high node density, it allows for node cooperations, and idle or infrastructure nodes can support the communication of source-destination pairs. With an adequate signaling scheme, the PWAN can operate as a virtual antenna array and ultimately achieve multiple-input multiple-output (MIMO) gains in a distributed way. Until now these networks have been studied using oversimplified channel models that were frequency flat and designed for cellular low node density networks. The novelty of this book is the study of a PWAN under realistic channel conditions and hardware constraints.
Author: Junqian Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"Relay-based cooperative communication provides tremendous benefits for next generation wireless networks. In this work, we propose a selective decode-and-forward (DF) multi-relay one-way and two-way network implementing regularized Weighted Decision Feedback Differential Coherent (WDFDC) receivers. The non-regularized WDFDC receivers have been employed in One-Way Relay Network (OWRN) and achieve significant performance gains over conventional differential detection (CDD). However, as shown in our work, non-regularized WDFDC receivers produce a BER increase phenomenon at high SNR due to decision feedback error propagation and intermittent transmissions between relay nodes and destination. To address this problem, a WDFDC receiver based on a regularized linear predictor (RLP) is proposed for a single link transmission and applied to relay-destination channels in OWRN and Two-Way Relay Network (TWRN). Analytical performance bounds are derived for systems with both non-regularized and regularized receivers. Extensive simulation results demonstrate that the use of regularized WDFDC receivers yields significant performance gains over non-regularized receivers at high SNR without noticeable performance degradation at low SNR. In addition, we propose a General (G)-TWRN model with various transmission protocols. For each protocol, optimum threshold is derived and applied to destinations. Analytical performance bounds are also derived for all protocols. Finally, realistic relays with phase-only, magnitude-only and combined phase-magnitude erasure regions are proposed for G-TWRN. We observe that the combined phase-magnitude method achieves the highest diversity and lowest performance loss with respect to ideal relays in the mid-low SNR region. The performance difference between three methods becomes smaller as the SNR increases." --
Author: Stefan Valentin
Publisher: Sudwestdeutscher Verlag Fur Hochschulschriften AG
ISBN: 9783838118581
Category :
Languages : en
Pages : 224
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Book Description
Cooperative relaying is a promising approach to improve data rate and coverage in wireless networks. Although the benefits of cooperation have been consistently shown in theory, the performance of realistic cooperative networks is still not clear. Bridging this gap between theory and practice is the objective of this thesis. This is done in three steps. First, practical selection relaying protocols are analyzed under realistic assumptions. Second, efficient protocol extensions are described and, third, a prototype for cooperative Wireless Local Area Networks (WLANs) is demonstrated. Based on theoretical findings and extensive field measurements, this thesis provides insight into the performance regions of realistic cooperative networks and into implementing cooperative devices. Furthermore, the basic elements of cooperative systems are introduced and a concise taxonomy of common designs is given. This text is, thus, helpful for researchers and engineers who implement cooperative systems, plan to support their networks by relaying, or look for an introduction in the field.
Author: Gi Wan Choi
Publisher:
ISBN:
Category : Mobile communication systems
Languages : en
Pages :
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Book Description
In recent years, global mobile data traffic has been increasing exponentially as mobile devices pervade our daily lives. To cope with the ever growing demands for higher data rates and seamless connectivity, one solution is to drastically increase the number of macro base stations in the conventional cellular architecture. However, this results in high deployment costs. Deploying low-power nodes such as relays that do not require a wired backhaul connection within a macrocell is one of cost-effective ways to extend high data rate coverage range. Relays are typically deployed to increase signal strength in poor coverage areas or to eliminate dead spots. But more importantly, relays provide a natural diversity, called cooperative diversity. In addition to a direct signal from a base station, extra copies of the same signal are forwarded from relays. Utilizing this diversity at the destination can yield significant performance enhancements. Thus, cooperative relay strategies need to be considered to enable high data rate coverage in a cost-effective manner. In this dissertation, we consider a simple single-relay network and present low-complexity and power-efficient cooperative relay designs that can achieve low error rate. We first study decode-and-forward (DF) relay networks with a single antenna at each node, where the relay decodes the received signal and forwards the re-encoded information to the destination. In DF relay scheme, decoding at the relay is not perfect and the error-propagation phenomenon is a detrimental problem, preventing the destination from collecting the cooperative diversity. To enable cooperative diversity in DF relay networks, we adopt link-adaptive power-scaling relay strategies where the relay scales the transmission power of the re-encoded signal based on the reliability of the source-relay link. We generalize power-profile designs and analyze the diversity order enabled by the general power-profile designs. We provide necessary and sufficient conditions for the designs to enable full cooperative diversity at the destination. In the second part of this dissertation, we extend the power-scaling relay strategy to DF multi-input multi-output (MIMO) relay networks, where multiple antennas are adopted at each node, and show that full cooperative diversity can also be achieved here. To collect spatial diversity provided by multiple antennas without using maximum-likelihood equalizers (MLEs) or near-ML detectors which exhibit high complexity, channel-controlled automatic repeat request (CC-ARQ) scheme is developed for DF MIMO relay networks to enable spatial diversity with linear equalizers (LEs) maintaining low-complexity. We also show that joint cooperative and spatial diversity can be achieved at the destination when the power-scaling strategy and the CC-ARQ with LEs are combined. Finally, amplify-and-forward (AF) MIMO relay designs, where the relay simply amplifies the received signal and forwards it to the destination, are studied with consideration of peak-power constraints at the relay. One practical concern for AF relaying is that the output signal at the relay may suffer from large peak-to-average power ratio (PAR), which may cause nonlinear distortion and/or saturation in the transmitted signal due to the limited linear range of power amplifiers. Thus, we first investigate peak-power constrained power-scaling strategies and find a sufficient condition to enable joint cooperative and spatial diversity at the destination. Based on this study, we propose simple and practical AF MIMO relay designs with peak-power constraint at the relay. CC-ARQ is also applied to AF MIMO relay networks to reduce the decoding complexity.
