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Author: Xuan Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
In this dissertation, we discuss various aspects of scheduling and resource allocation in multi-user wireless systems. This work starts from how to utilize advanced physical-layer technology to improve the system performance in a multi-user environment. We show that by using superposition coding (SPC) and successive interference cancellation, the system performance can be greatly improved with utility-based scheduling. Several observations are made as the design guideline for such system. Scheduling algorithms are designed for a system with hierarchical modulation which is a practical implementation of SPC. However, when the utility-based scheduling is designed, it is based on the assumption that the system is saturated, {\em i.e.}, users in the system always have data to transmit. It is pointed out in the literature that in a system with stochastic traffic, even if the arrival rate lies inside the capacity region, the system in terms of queue might not be stable with the utility-based scheduling. Motivated by this, we have studied the stability region of a general utility-based scheduling in a multi-user system with stochastic traffic. We show that the stability region is generally less than the capacity region, depends on how to interpret an intermediate control variable, and the resultant stability region may be even non-convex and exhibits undesirable properties which should be avoided. As the utility-based scheduling cannot achieve throughput-optimal, we turn our attentions to the throughput-optimal scheduling algorithms, whose stability region is identical to the capacity region. The limiting properties of an overloaded wireless system with throughput-optimal scheduling algorithms are studied. The results show that the queue length is unstable however the scheduling function of the queue length is stable, and the average throughput of the system converges. Finally we study how to schedule users in a multi-user wireless system with information-theoretic security support, which is focused on the secrecy outage probability. The problem is essentially about how to schedule users, and allocate resources to stabilize the system and minimize the secrecy outage probability. We show that there is a tradeoff between the arrival rate of the traffic and the secrecy outage probability. The relative channel condition of the eavesdropper also plays an important role to the secrecy outage probability. In summary, we showed utility-based scheduling using SPC can improve the system performance greatly, but the utility-based scheduling has limitations: the stability region might not have desired properties. On the contrary throughput-optimal scheduling has its own drawbacks: the traffic cannot be handled properly if the system is overloaded. The further study on the secrecy outage probability gives guideline on how to design a scheduler in a system with information-theoretic security support.
Author: Xuan Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
In this dissertation, we discuss various aspects of scheduling and resource allocation in multi-user wireless systems. This work starts from how to utilize advanced physical-layer technology to improve the system performance in a multi-user environment. We show that by using superposition coding (SPC) and successive interference cancellation, the system performance can be greatly improved with utility-based scheduling. Several observations are made as the design guideline for such system. Scheduling algorithms are designed for a system with hierarchical modulation which is a practical implementation of SPC. However, when the utility-based scheduling is designed, it is based on the assumption that the system is saturated, {\em i.e.}, users in the system always have data to transmit. It is pointed out in the literature that in a system with stochastic traffic, even if the arrival rate lies inside the capacity region, the system in terms of queue might not be stable with the utility-based scheduling. Motivated by this, we have studied the stability region of a general utility-based scheduling in a multi-user system with stochastic traffic. We show that the stability region is generally less than the capacity region, depends on how to interpret an intermediate control variable, and the resultant stability region may be even non-convex and exhibits undesirable properties which should be avoided. As the utility-based scheduling cannot achieve throughput-optimal, we turn our attentions to the throughput-optimal scheduling algorithms, whose stability region is identical to the capacity region. The limiting properties of an overloaded wireless system with throughput-optimal scheduling algorithms are studied. The results show that the queue length is unstable however the scheduling function of the queue length is stable, and the average throughput of the system converges. Finally we study how to schedule users in a multi-user wireless system with information-theoretic security support, which is focused on the secrecy outage probability. The problem is essentially about how to schedule users, and allocate resources to stabilize the system and minimize the secrecy outage probability. We show that there is a tradeoff between the arrival rate of the traffic and the secrecy outage probability. The relative channel condition of the eavesdropper also plays an important role to the secrecy outage probability. In summary, we showed utility-based scheduling using SPC can improve the system performance greatly, but the utility-based scheduling has limitations: the stability region might not have desired properties. On the contrary throughput-optimal scheduling has its own drawbacks: the traffic cannot be handled properly if the system is overloaded. The further study on the secrecy outage probability gives guideline on how to design a scheduler in a system with information-theoretic security support.
Author: Elias Yaacoub
Publisher: John Wiley & Sons
ISBN: 1118074505
Category : Technology & Engineering
Languages : en
Pages : 298
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Book Description
Tackling problems from the least complicated to the most, Resource Allocation in Uplink OFDMA Wireless Systems provides readers with a comprehensive look at resource allocation and scheduling techniques (for both single and multi-cell deployments) in uplink OFDMA wireless networks relying on convex optimization and game theory to thoroughly analyze performance. Inside, readers will find topics and discussions on: Formulating and solving the uplink ergodic sum-rate maximization problem Proposing suboptimal algorithms that achieve a close performance to the optimal case at a considerably reduced complexity and lead to fairness when the appropriate utility is used Investigating the performance and extensions of the proposed suboptimal algorithms in a distributed base station scenario Studying distributed resource allocation where users take part in the scheduling process, and considering scenarios with and without user collaboration Formulating the sum-rate maximization problem in a multi-cell scenario, and proposing efficient centralized and distributed algorithms for intercell interference mitigation Discussing the applicability of the proposed techniques to state-of-the-art wireless technologies, LTE and WiMAX, and proposing relevant extensions Along with schematics and figures featuring simulation results, Resource Allocation in Uplink OFDMA Wireless Systems is a valuable book for?wireless communications and cellular systems professionals and students.
Author: Ian C. Wong
Publisher: Springer Science & Business Media
ISBN: 0387749454
Category : Technology & Engineering
Languages : en
Pages : 126
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Book Description
This book proposes a unified algorithmic framework based on dual optimization techniques that have complexities that are linear in the number of subcarriers and users, and that achieve negligible optimality gaps in standards-based numerical simulations. Adaptive algorithms based on stochastic approximation techniques are also proposed, which are shown to achieve similar performance with even much lower complexity. All the algorithms proposed are clearly presented in concise block diagrams allowing the reader to implement these algorithms in the software of their choice. This book is an accessible reference for researchers and industry practitioners alike.
Author: Marios Nicolaou
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Author: Ian C. Wong
Publisher: Springer
ISBN: 9780387521176
Category : Technology & Engineering
Languages : en
Pages : 0
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Book Description
This book proposes a unified algorithmic framework based on dual optimization techniques that have complexities that are linear in the number of subcarriers and users, and that achieve negligible optimality gaps in standards-based numerical simulations. Adaptive algorithms based on stochastic approximation techniques are also proposed, which are shown to achieve similar performance with even much lower complexity. All the algorithms proposed are clearly presented in concise block diagrams allowing the reader to implement these algorithms in the software of their choice. This book is an accessible reference for researchers and industry practitioners alike.
Author: Anh H. Nguyen
Publisher:
ISBN: 9781303814372
Category :
Languages : en
Pages : 148
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Book Description
In wireless communications, it is of utmost importance to exploit multi-user diversity and at the same time provide satisfactory quality of service for all users. However, these two goals often conflict with each other. On one hand, multiuser diversity is maximized by selecting the user with the best channel condition. On the other, ensuring fairness among users demands the allocation of network resources to those who do not necessarily have the best channel conditions. Whenever a user with a poorer channel condition is selected, there is a certain loss in the overall system throughput. The major objective of this thesis is to find scheduling algorithms that guarantee fairness with minimal performance tradeoff. First, we consider multi-user diversity in a multi-user MIMO system. When zero-forcing beam-forming transmission technique is used, the system needs to find a subset of users such that the transmission to these users results in the highest throughput. As the number of users grows, the complexity of the user subset selection increases exponentially. To address this issue, simple user-subset-selection algorithms have been developed that can perform well and are very close to the optimal ones found through an exhaustive search. Maximizing system throughput is a key factor in ensuring high network performance, but guaranteeing service provision to all users is no less important. To support fairness among users, cumulative distribution function (CDF) scheduling is utilized because of the its capability to precisely control allocation for each user. The CDF scheduling algorithm requires knowledge of the channel distribution among all users. However, the channel distribution or even an approximation of it is hard to obtain in real systems. In this dissertation, two classes of practical, CDF-based scheduling algorithms are developed. They are the non-parametric CDF scheduling (NPCS), used when the channel model is unknown, and the parametric CDF scheduling (PCS), used when the channel model is known. These algorithms are shown to frequently outperform the well-known Proportional Fair (PF) scheduling method, and may be viable alternatives to it. The performance of the developed scheduling technique is then carefully analyzed and verified through simulations under various channel models. In order to apply them in real systems, these algorithms are first proposed for continuous rate transmission. Modified versions are then developed for finite rate transmission and limited feedback resources. Lastly, we analyze throughput of heterogeneous relay OFDMA systems using CDF scheduling with partial feedback. The scheduling problem is even more challenging with the incorporation of relays because of the different coherent time on their two hops. The CDF scheduling algorithm is modified to satisfy short-term fairness among users. In addition, performance of different feedback schemes in a wideband multi-user system are compared. Among the considered schemes, thresholding feedback is numerically shown to have the lowest feedback requirement, given a certain probability of feedback availability.
Author: Ana I. Perez-Neira
Publisher: Academic Press
ISBN: 0080920888
Category : Technology & Engineering
Languages : en
Pages : 188
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Book Description
Cross-Layer Resource Allocation in Wireless Communications offers practical techniques and models for the design and optimisation of cross-layer resource allocation – one of the hottest topics in wireless communications. Resource allocation in wireless networks is traditionally approached either through information theory or communications networks. To break down the barriers between these distinct approaches, this book bridges the physical and network layers by providing cross-layer resource allocation techniques, models, and methodologies. Its unique approach allows optimisation of network resources and will enable engineers to improve signal quality, enhance network and spectrum utilization, increase throughput, and solve the problem of shadowing. Topics covered include different views of spectral efficiency, the role of spatial diversity, of delay in resource allocation, and possible extensions to OFDMA systems. This will be an ideal reference on cross-layer resource allocation between the PHY and MAC layers for R&D and network design engineers and researchers in universities dealing with sensor networks and cognitive systems. Gives a full description of the characteristics of the PHY layer that promote efficient resource allocation strategies Gives special emphasis on cross-layer design for spatial diversity schemes Provides a framework for interaction between the PHY and MAC layers, their parameters of performance and their relationship Presents resource allocation as a cross-layer design based on an optimization of MAC layer parameters with an accurate model of the PHY layer
Author: Bo Ji
Publisher: Morgan & Claypool Publishers
ISBN: 1627059830
Category : Computers
Languages : en
Pages : 132
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Book Description
The last decade has seen an unprecedented growth in the demand for wireless services. These services are fueled by applications that often require not only high data rates, but also very low latency to function as desired. However, as wireless networks grow and support increasingly large numbers of users, these control algorithms must also incur only low complexity in order to be implemented in practice. Therefore, there is a pressing need to develop wireless control algorithms that can achieve both high throughput and low delay, but with low-complexity operations. While these three performance metrics, i.e., throughput, delay, and complexity, are widely acknowledged as being among the most important for modern wireless networks, existing approaches often have had to sacrifice a subset of them in order to optimize the others, leading to wireless resource allocation algorithms that either suffer poor performance or are difficult to implement. In contrast, the recent results presented in this book demonstrate that, by cleverly taking advantage of multiple physical or virtual channels, one can develop new low-complexity algorithms that attain both provably high throughput and provably low delay. The book covers both the intra-cell and network-wide settings. In each case, after the pitfalls of existing approaches are examined, new systematic methodologies are provided to develop algorithms that perform provably well in all three dimensions.
Author: Tianyu Ye
Publisher: Frontiers Media SA
ISBN: 2832538509
Category : Science
Languages : en
Pages : 194
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Book Description
Author: Leonidas Georgiadis
Publisher: Now Publishers Inc
ISBN: 1933019263
Category : Technology & Engineering
Languages : en
Pages : 161
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Book Description
Information flow in a telecommunication network is accomplished through the interaction of mechanisms at various design layers with the end goal of supporting the information exchange needs of the applications. In wireless networks in particular, the different layers interact in a nontrivial manner in order to support information transfer. In this text we will present abstract models that capture the cross-layer interaction from the physical to transport layer in wireless network architectures including cellular, ad-hoc and sensor networks as well as hybrid wireless-wireline. The model allows for arbitrary network topologies as well as traffic forwarding modes, including datagrams and virtual circuits. Furthermore the time varying nature of a wireless network, due either to fading channels or to changing connectivity due to mobility, is adequately captured in our model to allow for state dependent network control policies. Quantitative performance measures that capture the quality of service requirements in these systems depending on the supported applications are discussed, including throughput maximization, energy consumption minimization, rate utility function maximization as well as general performance functionals. Cross-layer control algorithms with optimal or suboptimal performance with respect to the above measures are presented and analyzed. A detailed exposition of the related analysis and design techniques is provided.
