Distributed Throughput Optimal Scheduling for Wireless Networks PDF Download

Author: Shuang Xia
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 39

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Book Description
Recent advancement in distributed scheduling algorithms mainly focuses on designing CSMA-type protocols to achieve maximum network throughput in a fully distributive manner. However, it is inherently difficult for distributed scheduling algorithms to promise hard deadlines and a good performance in the presence of heavy-tailed traffic. To encounter this, there are two distributed throughput optimal scheduling to be proposed, which is timely-throughput optimal scheduling and throughput optimal scheduling with heavy-tailed traffic. The timely-throughput optimal scheduling distributed determines the optimal transmission times for network users so that the largest set of traffic rates of network users can be supported, while ensuring timely data delivery within hard deadlines. Then, the distributed throughput optimal scheduling with heavy-tailed traffic is proposed, which makes the scheduling decision based on the queue lengths raised to the ?-th power. It is demonstrated that DMWS-? is throughput optimal with respect to moment stability in the sense that if the traffic arrivals rates are within the network stability region, all network users with light-tailed traffic arrivals always have bounded queueing delay with finite mean and variance.

Author: Libin Jiang
Publisher: Springer Nature
ISBN: 3031799925
Category : Computers
Languages : en
Pages : 144

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Book Description
In this book, we consider the problem of achieving the maximum throughput and utility in a class of networks with resource-sharing constraints. This is a classical problem of great importance. In the context of wireless networks, we first propose a fully distributed scheduling algorithm that achieves the maximum throughput. Inspired by CSMA (Carrier Sense Multiple Access), which is widely deployed in today's wireless networks, our algorithm is simple, asynchronous, and easy to implement. Second, using a novel maximal-entropy technique, we combine the CSMA scheduling algorithm with congestion control to approach the maximum utility. Also, we further show that CSMA scheduling is a modular MAC-layer algorithm that can work with other protocols in the transport layer and network layer. Third, for wireless networks where packet collisions are unavoidable, we establish a general analytical model and extend the above algorithms to that case. Stochastic Processing Networks (SPNs) model manufacturing, communication, and service systems. In manufacturing networks, for example, tasks require parts and resources to produce other parts. SPNs are more general than queueing networks and pose novel challenges to throughput-optimum scheduling. We proposes a "deficit maximum weight" (DMW) algorithm to achieve throughput optimality and maximize the net utility of the production in SPNs. Table of Contents: Introduction / Overview / Scheduling in Wireless Networks / Utility Maximization in Wireless Networks / Distributed CSMA Scheduling with Collisions / Stochastic Processing networks

Author: Sheu-Sheu Tan
Publisher:
ISBN: 9781267995414
Category :
Languages : en
Pages : 160

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Book Description
We develop channel aware scheduling and resource allocation schemes with cross-layer optimization for several problems in multiuser wireless networks. We consider problems of distributed opportunistic scheduling, where multiple users contend to access the same set of channels. Instead of scheduling users to the earliest available idle channels, we also take the instantaneous channel quality into consideration and schedule the users only when the channel quality is sufficiently high. This can lead to significant gains in throughput compared to system where PHY and MAC layers are designed separately and the wireless fading channels are abstracted as time invariant, fixed rate channels for scheduling purposes. We first consider opportunistic spectrum access in a cognitive radio network, where a secondary user (SU) share the spectrum opportunistically with incumbent primary users (PUs). Similar to earlier works on distributed opportunistic scheduling (DOS), we maximize the throughput of SU by formulating the channel access problem as a maximum rate-of-return problem in the optimal stopping theory framework. We show that the optimal channel access strategy is a pure threshold policy, namely the SU decides to use or skip transmission opportunities by comparing the channel qualities to a fixed threshold. We further increase the spectrum utilization by interleaving SU's packets with periodic sensing to detect PU's return. We jointly optimize the rate threshold and the packet transmission time to maximize the average throughput of SU, while limiting interference to PU. Next, we develop channel-aware opportunistic spectrum access strategies in a more general cognitive radio network with multiple SUs. Here, we additionally take into account the collisions and complex interaction between SUs and sharing of resources between them. We derive strategies for both cooperative settings where SUs maximize their sum total of throughputs, as well as non-cooperative game theoretic settings, where each SU tries to maximize its own throughput. We show that the optimal schemes for both scenarios are pure threshold policies. In the non-cooperative case, we establish the existence of Nash equilibrium and develop best response strategies that can converge to equilibria, with SUs relying only on their local observations. We study the trade-off between maximal throughput in the cooperative setting and fairness in the non-cooperative setting, and schemes based on utility functions and pricing that mitigate this tradeoff. In addition to maximizing throughput and fair sharing of resources, it is important to consider network/scheduling delays for QoS performance of delay-sensitive applications. We study DOS under both network-wide and user-specific average delay constraints. We take a stochastic Lagrangian approach and characterize the corresponding optimal scheduling policies accordingly, and show that they have a pure threshold structure. Next, we consider the use of different types of channel quality information, i.e., channel state information (CSI) and channel distribution information (CDI) in the opportunistic scheduling design for MIMO ad hoc networks. CSI is highly dynamic in nature and provides time diversity in the wireless channel, but is difficult to track. CDI offers temporal stability, but is incapable of capturing the instantaneous channel conditions. We design a new class of cross-layer opportunistic channel access scheduling framework for MIMO networks where CDI is used in the network context to group the simultaneous transmission links for spatial channel access and CSI is used in the link context to decide when and which link group should transmit based on a pre designed threshold. We thereby reap the benefits of both the temporal stability of CDI and the time diversity of CSI. Finally, we consider a novel application of cross layer optimization for communication of progressive coded images over OFDM wireless fading channels. We first consider adaptive modulation based on the instantaneous channel state information. An algorithm is proposed to allocate power and constellation size at each subchannel by maximizing the throughput. We next consider both the variance and the average of the throughput when deciding the constellation size for adaptive modulation. Simulation results confirm that cross-layer optimization with adaptive modulation enhances system performance.

Author: Siva Theja Maguluri
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
It is well known that the MaxWeight scheduling algorithm is throughput-optimal in wireless networks. However, its complexity is exponential in the number of links in an ad hoc network. In this work, we consider a greedy variant of the MaxWeight algorithm, called Longest Queue First (LQF). A synchronous version of LQF is known to be throughput-optimal under a topological condition called local pooling. Here we study an asynchronous version of LQF which is suitable for implementation in networks with variable packet sizes. We show that asynchronous LQF is also throughput-optimal under the local pooling condition.

Author: Akula Aneesh Reddy
Publisher:
ISBN:
Category :
Languages : en
Pages : 342

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Book Description
Wireless scheduling is a fundamental problem in wireless networks that involves scheduling transmissions of multiple users in order to support data flows with as high rates as possible. This problem was first addressed by Tassuilas and Ephremides, resulting in the celebrated Back-Pressure network scheduling algorithm. This algorithm schedules network links to maximize throughput in an opportunistic fashion using instantaneous network state information (NSI), i.e., queue and channel state knowledge across the entire network. However, the Back-Pressure (BP) algorithm suffers from various drawbacks - (a) it requires knowledge of instantaneous NSI from the whole network, i.e. feedback about time-varying channel and queue states from all links of the network, (b) the algorithm requires solving a global optimization problem at each time to determine the schedule, making it highly centralized. Further, Back-pressure algorithm was originally designed for wireless networks where interference is modeled using protocol interference model. As recent break-throughs in full-duplex communications and interference cancelation techniques provide greatly increased capacity and scheduling flexibility, it is not clear how BP algorithm can be modified to improve the data rates and reduce the delay. In this thesis, we address the drawbacks of Back-Pressure algorithm to some extent. In particular, our first work provides a new scheduling algorithm (similar to BP) that allows users to make individual decisions (distributed) based on heterogeneously delayed network state information (NSI). Regarding the complexity issue, in our second work, we analyze the performance of the greedy version of BP algorithm, known as Greedy Maximal Scheduling (GMS) and understand the effect of channel variations on the performance of GMS. In particular, we characterize the efficiency ratio of GMS in wireless networks with fading. In our third and fourth work, we propose and analyze new scheduling algorithms that can benefit from new advancements in interference cancelation techniques.

Author: Igor Kadota
Publisher:
ISBN:
Category :
Languages : en
Pages : 79

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Book Description
An increasing number of applications rely on wireless networks for distributing information. Communicating time-sensitive data such as position, video, voice and telemetry, can be particularly challenging in wireless networks due to packet losses. In this thesis, we consider a single-hop wireless network, in which a base station is sending time-sensitive data packets to a set of clients. Our goal is to study transmission scheduling strategies for real-time traffic. Even though this problem has been explored in the literature, we present novel results that provide useful insight into the optimal scheduling problem. Previous work considered the problem of maximizing the throughput of networks with instantaneous feedback and without feedback. We address the general case of delayed feedback. Delayed feedback is particularly important for communication systems in which the round trip delay is much greater than the packet transmission time, and it has a significant impact on the scheduling decisions and network performance. In addition, we consider the case of clients receiving multiple parallel packet flows with heterogeneous deadlines. It is a well-known result that the Shortest Time to Extinction (STE) policy optimizes the throughput in wired networks. In this thesis, we establish a class of wireless networks for which the STE policy is throughput-optimal, i.e. minimizes the expected number of packets that expire due to the deadlines. Finally, we study the wireless network from the perspective of the Age of Information (AoI). This recently proposed performance metric represents the freshness of the information at the clients. We use Dynamic Programming to formulate and solve the problem of characterizing the scheduling policy that minimizes the AoI. The AoI metric is compared with throughput, and insights are drawn from numerical results. Simulations suggest that AoI-optimal policies are always throughput-optimal, while the converse is not true.

Author: Yi Chen
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
In this dissertation, we discuss throughput-optimal scheduling design in multiuser wireless networks. Throughput-optimal scheduling algorithm design in wireless systems with flow-level dynamics is a challenging open problem, especially considering that the majority of the Internet traffic are short-lived TCP controlled flows. In future wireless networks supporting machine-to-machine and human-to-human applications, both short-lived dynamic flows and long-lived persistent flows coexist. How to design the throughput-optimal scheduling algorithm to support dynamic and persistent flows simultaneously is a difficult and important unsolved problem. Our work starts from how to schedule short-lived dynamic flows in wireless systems to achieve throughput-optimality with queue stability. Classic throughput-optimal scheduling algorithms such as the Queue-length based Maxweight scheduling algorithm (QMW) cannot stabilize systems with dynamic flows in practical communication networks. We propose the Head-of-Line (HOL) access delay based scheduling algorithm (HAD) for flow-level dynamic systems, and show that HAD is able to obtain throughput-optimality which is validated by simulation.As the Transmission Control Protocol (TCP) is the dominant flow and congestion control protocol for the Internet nowadays, we turn our attention to the compatibility between throughput-optimal schedulers and TCP. Most of the existing throughput-optimal scheduling algorithms have encountered unfairness problem in supporting TCP-controlled flows, which leads to undesirable network performance. Motivated by this, we first reveal the reason of the unfairness problem, then study the compatibility between HAD and TCP with different channel assumptions, and finally analyze the mean throughput performance of HAD. The result shows that HAD is compatible with TCP.Since the assumption of an infinite buffer size in the existing theoretical analysis of throughput-optimality is not practical, we analyze the queueing behaviour of the proposed throughput-optimal scheduling algorithm to provide useful guidelines for real system design by using the Markov chain analytic model. We propose the analytic model for the queuing and delay performance for the HAD scheduler, and then further develop an approximation approach to reduce the complexity of the model. Finally, we propose a throughput-optimal scheduling algorithm for hybrid wireless systems with the coexistence of persistent and dynamic flows. Then, to generalize the throughput-optimal scheduling, the control function in the scheduling rule is extended from a specific one to a class of functions, so that the scheduling design can be more flexible to make a tradeoff between delay, fairness, etc. We show that the hybrid wireless networks with coexisting persistent flows and dynamic flows can be stabilized by our proposed scheduling algorithm which can obtain throughput-optimality.In summary, we solve the challenging problem of designing throughput-optimal scheduling algorithm in wireless systems with flow-level dynamics. Then we show that our algorithm can support TCP regulated flows much better than the existing throughput-optimal schedulers. We further analyze the queueing behaviour of the proposed algorithm without the assumption of infinite buffer size that is often used in the throughput-optimality analysis in the literature, and the result provides a guideline for the implementation of our algorithm. At last, we generalize the proposed scheduling algorithm to support different types of flows simultaneously in practical wireless networks.

Author: Nathaniel Matthew Jones
Publisher:
ISBN:
Category :
Languages : en
Pages : 138

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Book Description
Optimal routing and scheduling algorithms have been studied for decades, however several practical issues prevent the adoption of these network control policies on the Internet. This thesis considers two distinct topics in distributed network control: (i) maximizing throughput in wireless networks using network coding, and (ii) deploying controllable nodes in legacy networks. Network coding is a relatively new technique that allows for an increase in throughput under certain topological and routing conditions. The first part of this thesis considers jointly optimal routing, scheduling, and network coding strategies to maximize throughput in wireless networks. We introduce a simple network coding strategy and fully characterize the region of arrival rates supported. We propose a centralized dynamic control policy for routing, scheduling, and our network coding strategy, and prove this policy to be throughput optimal subject to our coding constraint. We further propose a distributed control policy based on random access that optimizes for routing, scheduling, and pairwise coding, where pairwise coding captures most of the coding opportunities on random topologies. We prove this second policy to also be throughput optimal subject to the coding constraint. Finally, we reduce the gap between theory and practice by identifying and solving several problems that may occur in system implementations of these policies. Throughput optimal policies typically require every device in the network to make dynamic routing decisions. In the second part of this thesis, we propose an overlay routing architecture such that only a subset of devices (overlay nodes) need to make dynamic routing decisions, and yet maximum throughput can still be achieved. We begin by formulating an optimization problem that searches for the minimum overlay node placement that achieves maximum throughput. We devise an efficient placement algorithm which solves this problem optimally for networks not subject to interference constraints. Then we propose a heuristic control policy for use at overlay nodes, and show by simulation that this policy performs optimally in all studied scenarios.

Author: Matthew Ryan Johnston
Publisher:
ISBN:
Category :
Languages : en
Pages : 246

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Book Description
In wireless networks, transmissions must be scheduled to opportunistically exploit the time-varying capacity of the wireless channels to achieve maximum throughput. These opportunistic policies require global knowledge of the current network state to schedule transmissions eciently; however, providing a controller with complete channel state information (CSI) requires signicant bandwidth. In this thesis, we investigate the impact of control information on the ability to effectively schedule transmissions. In particular, we study the tradeoff between the availability and accuracy of CSI at the scheduler and the attainable throughput. Moreover, we investigate strategies for controlling the network with limited CSI. In the first half of the thesis, we consider a multi-channel communication system in which the transmitter chooses one of M channels over which to transmit. We model the channel state using an ON/OFF Markov process. First, we consider channel prob- ing policies, in which the transmitter probes a channel to learn its state, and uses the CSI obtained from channel probes to make a scheduling decision. We investigate the optimal channel probing strategies and characterize the tradeoff between probing frequency and throughput. Furthermore, we characterize a fundamental limit on the rate at which CSI must be conveyed to the transmitter in order to meet a constraint on expected throughput. In particular, we develop a novel formulation of the op- portunistic scheduling problem as a causal rate distortion optimization of a Markov source. The second half of this thesis considers scheduling policies under delayed CSI, re- sulting from the transmission and propagation delays inherent in conveying CSI across the network. By accounting for these delays as they relate to the network topology, we revisit the comparison between centralized and distributed scheduling, showing that there exist conditions under which distributed scheduling outperforms the optimal centralized policy. Additionally, we illustrate that the location of a centralized controller impacts the achievable throughput. We propose a dynamic controller placement framework, in which the controller is repositioned using delayed queue length information (QLI). We characterize the throughput region under all such policies, and propose a throughput-optimal joint controller placement and scheduling policy using delayed CSI and QLI.

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.