Channel Estimation And Optimal Resource Allocation Of Relay Assisted Communication Systems
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Channel Estimation and Optimal Resource Allocation of Relay Assisted Communication Systems
"Exploding demand for various wireless services has fueled significant development of wireless communication systems and networks in the past few decades. Wireless service providers are continuously striving to improve the design of communication systems and to enable higher data rate and more reliable wireless transmission. A major challenge in designing these systems is the random nature of the wireless transmission media due to the fading process. A recent paradigm shift from the conventional point-to-point communications is relay assisted communications. Motivated by the great success of multiple-input multiple-output (MIMO) wireless communication systems, with multiple transmit and receive antennas, researchers have considered relay assisted communications. Relying on the broadcast nature of the wireless media, a relay assisted communication system emulates a virtual MIMO system and exploits the spatial diversity, also known as cooperative diversity. Cooperative diversity increases the transmission reliability and coverage, without expanding the expenditure of the scarce transmission resources (power and bandwidth). Recently, the research community has witnessed an increasing interest in studying relay assisted communication systems. These studies include proposing novel relaying schemes, exploring ways to maximize the cooperative gain, and investigating the fundamental performance limits of these systems. The bulk of the literature is based on the main assumption that the effect of fading channels (commonly referred to as channel state information) is perfectly known at the destination. In practical communication systems, however, the unknown fading channels are first estimated and the channel estimates are used for decoding the message transmitted by the source. In order to have a more realistic and accurate understanding of the benefits of relay assisted systems, one needs to study the effect of uncertainty, imposed by channel estimation error, on the fundamental performance limits. Such study can guide to a more efficient system design and provide optimal resource allocation between data and training (required for channel estimation). Two widely used relay assisted wireless communication systems are: 1) a one-way relay assisted system, in which there is a source, a relay and a destination, and the relay helps the source by forwarding the overheard message to the destination; 2) a two-way relay assisted system, in which two sources are interested in mutual communication, i.e., one source is the destination of the other source. In this system the relay helps both users by forwarding the overheard messages to the intended destinations. For each system, one can envision different system designs, depending on the specific relaying scheme and the specific signal processing algorithm adopted at the relay. The most commonly used relaying schemes are Amplify-and-Forward (AF) and Decodeand- Forward (DF), where in the former the relay amplifies and forwards the overheard messages, while in the latter, the relay decodes the overheard messages and then forwards them. In this thesis, we consider one-way and two-way AF relay assisted systems with a half-duplex relay. We study the impact of uncertainty, due to channel estimation errors, on the fundamental performance limits. In particular, we consider mean squared error (MSE) and the Bayesian Cramer -Rao lower bound (CRLB) for channel estimation as the estimation theoretic optimality criteria and channel mutual information lower bound and outage probability upper bound as the information theoretic optimality criteria. We explore how the negative effect of channel uncertainty can be mitigated, via optimal transmission resource allocation that maximizes or minimizes a specific optimality criteria. We also compare the bidirectional mutual information lower bounds of direct transmission without the relay, one-way AF relay and two-way AF relay systems. Furthermore, we examine the effect of joint optimization of the media access control and physical layers on the system throughput for one-way AF and DF relay assisted systems"--Abstract.
Analysis and Design of Communication Techniques in Spectrally Efficient Wireless Relaying Systems
This dissertation studies the communication technologies in relaying systems with multiple antennas, especially in the multiple-input multiple-output (MIMO) two-way relaying systems. Both information-theoretic aspects and practical communication strategies are considered and analyzed. For the information-theoretic analysis, an analytical framework for the coverage of MIMO relaying systems based on an outage capacity criterion is proposed. For MIMO two-way relaying systems, different data combining schemes at the relay are compared based on their achievable rates. In addition, optimal time-division (TD) strategies for MIMO two-way decode-and-forward (DF) relaying systems are proposed and analyzed. When the optimal TD strategies are applied, the increase of the achievable rate regions in the system is significant compared to those using the equal TD strategy. For the practical transmission schemes, we propose the self-interference (SI) aided channel estimation and data detection schemes for the broadcast phase of two-way DF relaying systems. Such schemes exploit the SI in two-way DF relaying systems when the superposition coding (SPC) scheme is applied. When the network coding scheme is applied in two-way DF relaying systems, we propose an asymmetric data rate transmission scheme that utilizes the known data bits at the receivers. Such a scheme exploits the a priori known bits at the weak link receiver in the broadcast phase of two-way relaying systems.
Managing Resources for Futuristic Wireless Networks
The key parameter that needs to be considered when planning the management of resources in futuristic wireless networks is a balanced approach to resource distribution. A balanced approach is necessary to provide an unbiased working environment for the distribution, sharing, allocation, and supply of resources among the devices of the wireless network. Equal resource distribution also maintains balance and stability between the operations of communication systems and thus improves the performance of wireless networks. Managing Resources for Futuristic Wireless Networks is a pivotal reference source that presents research related to the control and management of key parameters of bandwidth, spectrum sensing, channel selection, resource sharing, and task scheduling, which is necessary to ensure the efficient operation of wireless networks. Featuring topics that include vehicular ad-hoc networks, resource management, and the internet of things, this publication is ideal for professionals and researchers working in the field of networking, information and knowledge management, and communication sciences. Moreover, the book will provide insights and support executives concerned with the management of expertise, knowledge, information, and organizational development in different types of work communities and environments.