Download or read book Exploiting Wireless Broadcast Property to Improve Performance of Distributed Algorithms and Mac Protocols in Wireless Networks written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Wireless Networks Model and Optimization Based Approaches to Clock Synchronization Random Access MAC and Video Streaming written by Nikolaos M. Freris and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We, via a model and optimization-based approach, address three issues related to wireless networks: clock synchronization, medium access control (MAC) and scalable video streaming. In Chapter 2 we develop, study and simulate a new model-based distributed network clock synchronization protocol. In a network of clocks, a given node is taken as reference and is associated with the time evolution t. We introduce and analyze a stochastic model for clocks, in which the relative speedup of a clock with respect to the reference node, called the skew, is characterized by an exponential transformation of an Orstein-Uhlenbeck process. We study the properties of our model, namely moment and sample path properties of the stochastic processes, and calculate its Allan variance. We show how our model can be used to translate the time of a clock to another clock's units. We study the problem of synchronizing clocks in a network, which amounts to estimating the instantaneous relative skews and relative offsets, i.e., the differences in the clock readouts, by exchange of time-stamped packets between pairs of nodes in the network. Based on a stochastic model for delays, we derive a scheme for obtaining relative skew measurements in a communication link by sending two time-stamped packets from node i to node j in order to obtain a noisy measurement of their relative skew. We develop an algorithm for filtering relative skew measurements across a link (i,j) in order to estimate the logarithm of the relative skew. We study the properties of the algorithms and provide theoretical guarantees on their performance. We also develop an online, centralized, model-based, asynchronous skew estimation algorithm for optimal filtering of the time-stamps in the entire network, as well as an efficient distributed suboptimal scheme which demonstrates near-optimal performance in simulations. Furthermore, we study some implementation issues, and present a scheme for pairwise relative offset estimation given skew estimates. We use the distributed asynchronous algorithm to obtain nodal offset estimates from relative offset estimates. We combine our findings into developing a new protocol for clock synchronization, namely the Model-Based Clock Synchronization Protocol (MBCSP). We present a comparative simulation study of its performance versus the leading scheme by Solis et al. (2006); the results show that MBCSP performs better in terms of skew, offset and delay estimation. Finally, we have performed trace-driven simulation based on time-stamps obtained from Berkeley motes. Our scheme outperforms that of Solis et al. by 45%, where we used the accuracy in predicting the receipt time-stamp at the sender as the clock synchronization metric. In Chapter 3, we study random access based MAC in the framework of network utility maximization (NUM). There has been much recent interest in protocol design for wireless networks based on maximizing a network utility function. A significant advance is the observation that a decomposition of the Lagrangian suggests an approach where transmissions are scheduled to minimize back-pressure. However, a satisfactory MAC protocol that can realize such a scheduling algorithm is notably missing, and we develop one potential scheme. We present a candidate random access MAC protocol that extends an existing algorithm by Gupta and Stolyar (2006) in calculating the access probabilities. We also consider the online adaptation of access probabilities using local information about queue lengths and active links. We provide OPNET simulation results to compare the performance of our scheme with the leading schemes. We estimate the capacity region of our scheme by simulation for various topologies and multiple flows. Our simulation studies indicate that our extension in conjunction with an implementation of back-pressure significantly outperforms the slotted-time algorithm of Gupta and Stolyar (2006). In Chapter 4, we present performance bounds for random access based MAC using carrier-sense multiple access (CSMA). In recent work, it was shown that a distributed CSMA-based MAC protocol is throughput-optimal which, in turn, implies that the class of controlled distributed random access MAC protocols can support the entire capacity region. It is challenging to study the performance of such schemes in terms of mean delays and compare it with some known results on the performance of centralized scheduling. We modify the model of Jiang and Walrand (2008) to obtain Markov chain models that incorporate the queue lengths as well as the information about the independent set, for single-hop networks. We show that the delay of the new models yields an upper bound on the delay of the original models. We derive upper and lower bounds on the mean total delay at the steady-state, and show that these bounds coincide with those for max-weight scheduling. Finally, we develop a method of deriving upper and lower bounds for random-access schemes by using linear programs (LPs). We present an optimization program for minimizing the upper bounds. In Chapter 5, we consider multihomed scalable video streaming systems where each video is concurrently transmitted over several access networks to a client. The problem is to determine which video packets of a video stream to transmit, and associate each video packet with an access network, so that the video quality at the client is maximized under measured network conditions. We present a network model and a video distortion model to capture the network conditions and video distortion characteristics, respectively. We develop a mathematical formulation to find the streaming strategy for maximizing the average video quality at the client. While the formulation can be optimally solved using exhaustive search or dynamic programming, doing so takes a prohibitively long time, and is not practical for real-time video streaming servers. In order to efficiently solve the problem in real time, we propose several suboptimal convex problems along with two heuristic algorithms. We conduct extensive trace-driven simulations to evaluate the algorithms using real network conditions and actual scalable video streams. We compare our algorithms against the rate control algorithms defined in the Datagram Congestion Control Protocol (DCCP) standard. The simulation results show that our algorithms significantly outperform current systems while being TCP-friendly. For example, compared to DCCP, our algorithms achieve at least 10 dB quality improvement and result in up to 83% packet delivery delay reduction. Finally, we study the trade-off between efficiency and optimality: One of the heuristic algorithms runs faster and is suitable for large-scale streaming systems, while the other one achieves better video quality and is more appropriate for smaller streaming servers. The convex programming approach demonstrates a good trade-off between running time and performance.

Download or read book Adding More Phy to the Mac written by Michael König and published by Createspace Independent Publishing Platform. This book was released on 2017-07-11 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Traditional wireless algorithms all too often ignore the special qualities of the wireless medium. In this thesis, we propose new wireless transmission primitives for various applications and evaluate each of them on a wireless sensor network. In particular, we focus on integrating two properties into our primitives: the availability of transmission power control and the capture effect. First, we consider the problems of traffic prioritization and running multiple wireless algorithms in parallel. We propose a technique allowing to simultaneously run multiple algorithms of different priorities, with minimal overhead in terms of bandwidth and latency. This is done by assigning each priority a range of admissible received signal strengths at each node, and employing the capture effect to automatically enable reception of only the strongest incoming signal. The setup is transparent to the algorithms: each appears to have complete access to the network's resources as long as no algorithm of a higher priority wishes to use them. We discuss which properties of the network graph and the wireless hardware are beneficial to our technique. Second, we demonstrate the feasibility of achieving constructive interference using commodity wireless sensor nodes. In contrast to previous work, our technique does not rely on global external events as reference, but instead aims to minimize the errors in clock synchronization and transmission timing. Our evaluation shows that our technique is able to achieve constructive interference in over 30% of cases, even after multiple minutes of sleep. Third, we propose a class of transmission primitives which decouple packets' synchronization headers from their payloads, such that two or more different senders may contribute to a single received packet. We explore 2 applications: 1) enabling reception attempts of very weak packets, e.g., across a network chasm, and 2) the injection of shorter packets into longer ongoing transmissions. We investigate ways to vastly reduce the problems incurred by using a mismatching synchronization header for reception. In practice, we are able to successfully decode up to 30% of cross-chasm packets and up to 70% of injected packets. Fourth, we examine how transmission power control can improve wireless schedules. Based on the classic RAND scheduling algorithm we develop a version employing power control called PowerRAND. The schedules generated by PowerRAND are 20-25% shorter, i.e., achieve a 25-33% higher throughput than RAND. Our practical evaluation shows that these schedules are just as feasible in practice. Further, we discuss how power control provides flexibility to schedules in the face of changing environments.

Download or read book Design and Analysis of Medium Access Control Protocols for Broadband Wireless Networks written by Lin Cai and published by . This book was released on 2009 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: The next-generation wireless networks are expected to integrate diverse network architectures and various wireless access technologies to provide a robust solution for ubiquitous broadband wireless access, such as wireless local area networks (WLANs), Ultra-Wideband (UWB), and millimeter-wave (mmWave) based wireless personal area networks (WPANs), etc. To enhance the spectral efficiency and link reliability, smart antenna systems have been proposed as a promising candidate for future broadband access networks. To effectively exploit the increased capabilities of the emerging wireless networks, the different network characteristics and the underlying physical layer features need to be considered in the medium access control (MAC) design, which plays a critical role in providing efficient and fair resource sharing among multiple users. In this thesis, we comprehensively investigate the MAC design in both single- and multi-hop broadband wireless networks, with and without infrastructure support.

Download or read book Distributed Medium Access Control in Wireless Networks written by Ping Wang and published by Springer Science & Business Media. This book was released on 2013-03-23 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: This brief investigates distributed medium access control (MAC) with QoS provisioning for both single- and multi-hop wireless networks including wireless local area networks (WLANs), wireless ad hoc networks, and wireless mesh networks. For WLANs, an efficient MAC scheme and a call admission control algorithm are presented to provide guaranteed QoS for voice traffic and, at the same time, increase the voice capacity significantly compared with the current WLAN standard. In addition, a novel token-based scheduling scheme is proposed to provide great flexibility and facility to the network service provider for service class management. Also proposed is a novel busy-tone based distributed MAC scheme for wireless ad hoc networks and a collision-free MAC scheme for wireless mesh networks, respectively, taking the different network characteristics into consideration. The proposed schemes enhance the QoS provisioning capability to real-time traffic and, at the same time, significantly improve the system throughput and fairness performance for data traffic, as compared with the most popular IEEE 802.11 MAC scheme.

Download or read book Online Learning for Exploiting Diversity in Adaptive Wireless Networks written by Nikhil Gulati and published by . This book was released on 2015 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: The landscape for wireless systems and networks is changing rapidly with new emerging communication paradigms such as machine-to-machine communication (M2M), heterogeneous cellular network (HetNets), cognitive radio, and new WiFi technologies. As a result of this shift, there is a significant focus on making wireless networks self aware, self-reliant and adaptive, both at the edge and at the core. Fundamentally, wireless communication is still limited by noise, attenuation and interference. As the networks become dense, continuos evolution of current wireless infrastructure and technologies is required. While, the information theorists try to understand the fundamental capacity limits of these complex networks, the wireless engineers, try to achieve these limits and extract every bit of performance from all the layers of the network stack. In this dissertation, we focus on the role of diversity provided by modern antenna systems, in enabling an adaptive wireless system. Specifically, we focus on algorithms for exploiting the diversity offered by reconfigurable antenna systems tightly integrated with an agile wireless device. With the introduction of reconfigurable antennas, there was a departure from the notion that a wireless device has no control over the wireless channel. Reconfigurable antenna systems are capable of operating under multiple radiation states which provide multiple channels, potentially providing an opportunity to select a state for optimizing a communication link and/or a network state. This additional degree of freedom comes with an overhead to acquire information about the state of all the channels, a need for a strategy to select the optimal state, and most importantly an ability to learn the changes in the channel state in order to adapt. Traditionally techniques rely on prior knowledge of the channel which is often not available or heuristics which don't scale well. With these goals in mind, we utilize online learning based on multi-armed bandit theory to design algorithms to control and adapt the state of a reconfigurable antenna system. We investigate the trade-off between the amount and the frequency with which the channel state information is collected and its effect on the system performance. We demonstrate the effectiveness of an online sequential learning algorithm to select an optimal antenna state for throughput optimization in a single user wireless system similar to 802.11x WiFi devices. Further, we develop online learning algorithms for channel selection in a distributed multi-user network for enhancing interference management techniques. For both these network settings, we analyze the cost of learning under an unknown statistical model of the channel and compare it with an oracle with full prior knowledge. We characterize the performance of the proposed algorithms with link quality metrics derived from the channel information. We show promising results with improved performance in key metrics such as signal-to-noise ratio (SNR), link throughput, and network sum rate. Finally, we leverage a software defined radio platform to experimentally evaluate the usefulness of these algorithms in real-world scenarios. Finally, we also develop an online model learning technique using Gaussian Mixture Model to identify intruders in the network. We formulate the problem as a physical layer authentication problem where device signatures are generated using the pattern diversity offered by the reconfigurable antennas. The proposed algorithm learns the distribution of channel-based device signatures and distinguishes between an intruder and a legitimate user. We successfully show that the proposed technique can reduce the false alarm rates while achieving very low miss detection rate.

Download or read book Energy and Spectrum Efficient Wireless Network Design written by Guowang Miao and published by Cambridge University Press. This book was released on 2015 with total page 387 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides the fundamental principles and practical tools needed to design next-generation wireless networks that are both energy- and spectrum-efficient.

Download or read book Wireless Sensor Networks written by Ananthram Swami and published by John Wiley & Sons. This book was released on 2007-10-24 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: A wireless sensor network (WSN) uses a number of autonomous devices to cooperatively monitor physical or environmental conditions via a wireless network. Since its military beginnings as a means of battlefield surveillance, practical use of this technology has extended to a range of civilian applications including environmental monitoring, natural disaster prediction and relief, health monitoring and fire detection. Technological advancements, coupled with lowering costs, suggest that wireless sensor networks will have a significant impact on 21st century life. The design of wireless sensor networks requires consideration for several disciplines such as distributed signal processing, communications and cross-layer design. Wireless Sensor Networks: Signal Processing and Communications focuses on the theoretical aspects of wireless sensor networks and offers readers signal processing and communication perspectives on the design of large-scale networks. It explains state-of-the-art design theories and techniques to readers and places emphasis on the fundamental properties of large-scale sensor networks. Wireless Sensor Networks: Signal Processing and Communications : Approaches WSNs from a new angle – distributed signal processing, communication algorithms and novel cross-layer design paradigms. Applies ideas and illustrations from classical theory to an emerging field of WSN applications. Presents important analytical tools for use in the design of application-specific WSNs. Wireless Sensor Networks will be of use to signal processing and communications researchers and practitioners in applying classical theory to network design. It identifies research directions for senior undergraduate and graduate students and offers a rich bibliography for further reading and investigation.

Download or read book Handbook of Algorithms for Wireless Networking and Mobile Computing written by Azzedine Boukerche and published by CRC Press. This book was released on 2005-11-28 with total page 1042 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Handbook of Algorithms for Wireless Networking and Mobile Computing focuses on several aspects of mobile computing, particularly algorithmic methods and distributed computing with mobile communications capability. It provides the topics that are crucial for building the foundation for the design and construction of future generations of mobile and wireless networks, including cellular, wireless ad hoc, sensor, and ubiquitous networks. Following an analysis of fundamental algorithms and protocols, the book offers a basic overview of wireless technologies and networks. Other topics include issues related to mobility, aspects of QoS provisioning in wireless networks, future applications, and much more.

Download or read book Wireless Algorithms Systems and Applications written by Yingshu Li and published by Springer. This book was released on 2008-10-15 with total page 595 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the Third Annual International Conference on Wireless Algorithms, Systems, and Applications, WASA 2008, held in Dallas, TX, USA, in October 2008. The 35 revised full papers presented together with 3 keynote talks and 15 invited lectures were carefully reviewed and selected from numerous submissions. Providing a forum for researchers and practitioners, from the academic, industrial and governmental sectors, the papers address current research and development efforts of various issues in the area of algorithms, systems and applications for current and next generation infrastructure and infrastructureless wireless networks.

Download or read book Exploiting Wireless Broadcasting Nature for High throughput 802 11 Mesh Networks written by Jian Zhang and published by . This book was released on 2008 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wireless mesh networking (WMN) has seen great research and commercial interests recently. It is considered a promising technology for implementing wireless community networks. Although the ubiquitous and low-cost Wi-Fi devices make IEEE 802.11 a prevailing choice for wireless mesh networks, the current IEEE 802.11 protocols cannot achieve full utilization of network capacity in wireless mesh networks. When dealing with multi-hop transmissions, IEEE 802.11 MAC presents low efficiency in coordinating concurrent transmissions, ineffectiveness in avoiding interference. In this dissertation, we demonstrate the factors that lead to low capacity in 802.11 mesh netowrks, and we survey the existing work on improving the network throughput. A large class of previous work focuses on coping with the interference, i.e., curbing the negative effect of broadcast nature of wireless signaling. In contrast, another set of work introduced here tries to exploit the wireless broadcasting, and it exhibits promising potential for large throughput gain in mesh networks. We propose three methods that further take advantage of wireless broadcasting. They all aim at achieving high throughput in WMNs, while exploiting the broadcasting nature in different aspects. The first work passively makes use of wireless broadcasting in that it collects wireless link information through mere listening. Specifically, we present a non-intrusive method to model and estimate 802.11 link bandwidth based on radio signal-to-noise ratio (SNR). In a more active way, the second method enables mesh senders to probes their receivers for their MAC statuses so that their following transmissions can be more efficient. Owing to wireless broadcasting, multiple receivers are probed simultaneously with one single probing and their diversity/correlations are speculated. With the diversity information, we propose a smart scheduling strategy. We show that such diversity information can greatly improve throughput of mesh senders. Furthermore, the third method proactively uses the packet redundancy caused by wireless transmissions in local area of a network. Such redundancy are usually ignored or even avoided on purpose by traditional protocols. In contrast, we show that it provides an abundant repository of packets for performing network coding. We propose a new protocol called BEND, which enables each potential forwarder to proactively mix/encode the packets that either are intended to or are overheard by this node. This proactive mixing significantly increases the coding opportunities in the network, leading to high capacity gain.

Download or read book Design and Analysis of Opportunistic MAC Protocols for Cognitive Radio Wireless Networks written by Hang Su and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As more and more wireless applications/services emerge in the market, the already heavily crowded radio spectrum becomes much scarcer. Meanwhile, however, as it is reported in the recent literature, there is a large amount of radio spectrum that is under-utilized. This motivates the concept of cognitive radio wireless networks that allow the unlicensed secondary-users (SUs) to dynamically use the vacant radio spectrum which is not being used by the licensed primary-users (PUs). In this dissertation, we investigate protocol design for both the synchronous and asynchronous cognitive radio networks with emphasis on the medium access control (MAC) layer. We propose various spectrum sharing schemes, opportunistic packet scheduling schemes, and spectrum sensing schemes in the MAC and physical (PHY) layers for different types of cognitive radio networks, allowing the SUs to opportunistically utilize the licensed spectrum while confining the level of interference to the range the PUs can tolerate. First, we propose the cross-layer based multi-channel MAC protocol, which integrates the cooperative spectrum sensing at PHY layer and the interweave-based spectrum access at MAC layer, for the synchronous cognitive radio networks. Second, we propose the channel-hopping based single-transceiver MAC protocol for the hardware-constrained synchronous cognitive radio networks, under which the SUs can identify and exploit the vacant channels by dynamically switching across the licensed channels with their distinct channel-hopping sequences. Third, we propose the opportunistic multi-channel MAC protocol with the two-threshold sequential spectrum sensing algorithm for asynchronous cognitive radio networks. Fourth, by combining the interweave and underlay spectrum sharing modes, we propose the adaptive spectrum sharing scheme for code division multiple access (CDMA) based cognitive MAC in the uplink communications over the asynchronous cognitive radio networks, where the PUs may have different types of channel usage patterns. Finally, we develop a packet scheduling scheme for the PU MAC protocol in the context of time division multiple access (TDMA)-based cognitive radio wireless networks, which is designed to operate friendly towards the SUs in terms of the vacant-channel probability. We also develop various analytical models, including the Markov chain models, M=GY =1 queuing models, cross-layer optimization models, etc., to rigorously analyze the performance of our proposed MAC protocols in terms of aggregate throughput, access delay, and packet drop rate for both the saturation network case and non-saturation network case. In addition, we conducted extensive simulations to validate our analytical models and evaluate our proposed MAC protocols/schemes. Both the numerical and simulation results show that our proposed MAC protocols/schemes can significantly improve the spectrum utilization efficiency of wireless networks.

Download or read book UTILITY BASED RESOURCE ALLOCATION STRATEGIES AND PROTOCOL DESIGN FOR SPECTRUM ADAPTIVE WIRELESS NETWORKS written by and published by . This book was released on 2009 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: Resource allocation strategies, including power control, rate adaptation, and dynamic spectrum access, have been the keys to improving the performance of dynamic (mobile) wireless networks. In this dissertation, we propose several resource optimization schemes for various wireless network architectures, with the goal of maximizing the system throughput and/or minimizing the total energy consumption. These schemes are integrated into the design of distributed medium-access control (MAC) protocols. We propose a game theoretic power control scheme for single-channel ad-hoc networks, and design an efficient MAC protocol, called GMAC, that implements such a scheme in a distributed fashion. GMAC allows for multiple potential transmitters to contend for the channel through an admission phase that these transmitters to determine their appropriate transmission powers. Successful contenders proceed concurrently following the admission phase. We then study the operation of spectrum-agile (cognitive) radios in multi-channel, multi-hop wireless network setting. Two principal cases are considered: exclusive-occupancy and interference-based channel models. For the case of exclusive-occupancy channel models, we design a MAC protocol that exploits the "dual receive" capabilities of the radios to maximize the network throughput. We then propose a cross-layer framework for joint adaptive load/medium access controls. Under this framework, the traffic loads of individual node are adapted based on local MAC parameters. For the case of interference-based channel models, when system throughput is the primary performance metric, we apply "price-based" iterative water-filling (PIWF) algorithms for resource allocation. When energy consumption is the primary metric, we propose a selfish update algorithm and an incentive-based update algorithm for minimizing the power consumption while satisfying the rate and power mask requirements. These algorithms are implemented by having nodes repeatedly negotiate their best power/spectrum to reach a good Nash Equilibrium. An efficient multi-channel MAC protocol is proposed to facilitate the radio negotiation and convergence phase. Simulation results indicate that our proposed protocols achieve significant throughput/energy improvements over existing protocols.

Download or read book MAC Protocols Design and a Cross layered QoS Framework for Next Generation Wireless Networks written by Essaïd Sabir and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present dissertation deals with the problem of under-utilization of collision channels and other related problems in wireless networks. It deals with the design of random access protocols for wireless systems and provides a mathematical framework for performance evaluation of multihop based heterogeneous wireless networks. This thesis is divided into three parts. In the first part, we propose new versions of slotted aloha incorporating power control, priority and hierarchy. Our simulations were important to understand the behaviour of such a system and the real impact of involved parameters (transmit power, transmit rate, arrival rate, hierarchy order). Both team problem (common objective function is maximized) and game problem (each user maximizes its own objective) were discussed. Introducing hierarchy seems to provide many promising improvement without/or with a low amount of external information. We also proposed two distributed algorithms to learn the desired throughput. Next, we developed in the second part an analytical Framework to evaluate performances of multihop based heterogeneous Wireless networks. We built a cross-layer model and derived expression of stability, end-to-end throughput and end-to-end delay. Furthermore, we provided an accurate approximation for the distribution of end-to-end delay in multihop ad hoc networks (operating with slotted aloha protocol). As a direct application, we highlighted how streaming and conversational flows could be supported in this class of ubiquitous networks. The third part of this thesis is devoted to understanding and modelling of IEEE 802.11e DCF/EDCF-operated multihop ad hoc networks. We indeed built a complete and simple APPLICATION/NETWORK/MAC/PHY cross-layered model with finite retries per packet per flow. We analyzed the stability of forwarding queues and derived expression of end-to-end throughput. We finally proposed a Fountain code-based MAC layer to improve the throughput/fairness over the network.

Download or read book Cross layer Adaptive Transmission Scheduling in Wireless Networks written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A new promising approach for wireless network optimization is from a cross-layer perspective. This thesis focuses on exploiting channel state information (CSI) from the physical layer for optimal transmission scheduling at the medium access control (MAC) layer. The first part of the thesis considers exploiting CSI via a distributed channel-aware MAC protocol. The MAC protocol is analysed using a centralized design approach and a non-cooperative game theoretic approach. Structural results are obtained and provably convergent stochastic approximation algorithms that can estimate the optimal transmission policies are proposed. Especially, in the game theoretic MAC formulation, it is proved that the best response transmission policies are threshold in the channel state and there exists a Nash equilibrium at which every user deploys a threshold transmission policy. This threshold result leads to a particularly efficient stochastic-approximation-based adaptive learning algorithm and a simple distributed implementation of the MAC protocol. Simulations show that the channel-aware MAC protocols result in system throughputs that increase with the number of users. The thesis also considers opportunistic transmission scheduling from the perspective of a single user using Markov Decision Process (MDP) approaches. Both channel state information and channel memory are exploited for opportunistic transmission. First, a finite horizon MDP transmission scheduling problem is considered. The finite horizon formulation is suitable for short-term delay constraints. It is proved for the finite horizon opportunistic transmission scheduling problem that the optimal transmission policy is threshold in the buffer occupancy state and the transmission time. This two-dimensional threshold structure substantially reduces the computational complexity required to compute and implement the optimal policy. Second, the opportunistic transmission scheduling problem is formulated as an infinite horizon.

Download or read book Wired Wireless Internet Communication written by Vassilis Tsaoussidis and published by Springer. This book was released on 2013-05-29 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the 11th International Conference on Wired/Wireless Internet Communications, WWIC 2013, held in St. Petersburg, Russia, during June 5-7, 2013. The 21 revised full papers presented were carefully reviewed and selected from numerous submissions. The papers are organized in topical sections on: MAC and scheduling; mobility; fixed networks; services and security; sensor networks; services; and wireless.

Download or read book Efficient Network Camouflaging in Wireless Networks written by Shu Jiang and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Camouflaging is about making something invisible or less visible. Network camouflaging is about hiding certain traffic information (e.g. traffic pattern, traffic flow identity, etc.) from internal and external eavesdroppers such that important information cannot be deduced from it for malicious use. It is one of the most challenging security requirements to meet in computer networks. Existing camouflaging techniques such as traffic padding, MIX-net, etc., incur significant performance degradation when protected networks are wireless networks, such as sensor networks and mobile ad hoc networks. The reason is that wireless networks are typically subject to resource constraints (e.g. bandwidth, power supply) and possess some unique characteristics (e.g. broadcast, node mobility) that traditional wired networks do not possess. This necessitates developing new techniques that take account of properties of wireless networks and are able to achieve a good balance between performance and security. In this three-part dissertation we investigate techniques for providing network camouflaging services in wireless networks. In the first part, we address a specific problem in a hierarchical multi-task sensor network, i.e. hiding the links between observable traffic patterns and user interests. To solve the problem, a temporally constant traffic pattern, called cover traffic pattern, is needed. We describe two traffic padding schemes that implement the cover traffic pattern and provide algorithms for achieving the optimal energy efficiencies with each scheme. In the second part, we explore the design of a MIX-net based anonymity system in mobile ad hoc networks. The objective is to hide the source-destination relationship with respect to each connection. We survey existing MIX route determination algorithms that do not account for dynamic network topology changes, which may result in high packet loss rate and large packet latency. We then introduce adaptive algorithms to overcome this problem. In the third part, we explore the notion of providing anonymity support at MAC layer in wireless networks, which employs the broadcast property of wireless transmission. We design an IEEE 802.11-compliant MAC protocol that provides receiver anonymity for unicast frames and offers better reliability than pure broadcast protocol.