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Distributed Fault-Tolerance for Event Detection Using Heterogeneous Wireless Sensor Networks

IEEE TRANSACTIONS ON MOBILE COMPUTING 2012年第12期11卷 1994-2007页

作者： Ould-Ahmed-Vall, ElMoustapha Ferri, Bonnie Heck Riley, George F. Intel Corp Software Performance Modeling & Comp Architecture Chandler AZ 85226 USA Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA

This paper presents a general fault-tolerant event detection scheme that allows nodes to detect erroneous local decisions by leveraging the local decisions reported by their neighbors. This detection scheme can handle cases where nodes have different accuracy levels. The derived fault-tolerant estimator is proven to be optimal under the maximum a posteriori (MAP) criterion. An equivalent weighted voting scheme is also derived. Further, two new error models are derived to take into account the neighbor distance and the geographical distributions of the two decision quorums. These models are particularly suitable for detection applications where the event under consideration is highly localized. The fault-tolerant estimator is simulated using a network of 1,024 nodes deployed randomly in a square region and assigned random probabilities of failure. Several estimation schemes that allow nodes to learn their error rates continuously are developed. These error rates are used in the distributed estimation schemes to assign appropriate weights to the nodes in the voting scheme.

关键词： Sensor networks fault tolerance algorithm/protocol design and analysis

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GRaTIS: Free Bits in the Network

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2015年第1期14卷 72-85页

作者： Saha, Dola Dutta, Aveek Grunwald, Dirk Sicker, Douglas Univ Colorado Boulder CO 80309 USA Univ Colorado Dept Elect Comp & Energy Engn Boulder CO 80309 USA Univ Colorado Dept Comp Sci Dept Elect & Comp Engn Boulder CO 80309 USA Univ Colorado Dept Comp Sci Boulder CO 80309 USA

Recent work has examined techniques to estimate the "best" modulation rate for data networks such as 802.11a/g. While accurate rate estimation yields better rate-selection decisions and increased throughput, those methods must still choose between a handful of modulation rates. Each modulation rate is effective in a range of actual signal-to-noise ratios (SNRs) but the limited number of practical rates means that transmitters are often forced to "step down" to a lower data rate despite having a higher SNR than the minimum required for that lower rate. In this paper we describe, evaluate and implement a practical multiuser communication scheme that exploits these discrete "steps" in modulation rates to transmit two packets in the time normally needed to transmit a single packet, increasing aggregate throughput precisely when it is most needed-when the network is busy and suffers from rate unfairness. Because the method transmits a group of packets simultaneously, we call this scheme Group Rate Transmission with Intertwined Symbols, or GRaTIS. In addition to up to 120% improvement in network throughput achieved by GRaTIS, the technique is backward compatible with 802.11 and doesn't require complex DSP algorithms as required by competing methods.

关键词： Wireless communication protocol architecture signal processing systems algorithm/protocol design and analysis reconfigurable hardware

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Bandwidth aggregation for real-time applications in heterogeneous wireless networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2006年第4期5卷 388-403页

作者： Chebrolu, K Rao, RR Univ Calif San Diego Dept Elect & Comp Engn La Jolla CA 92093 USA

A variety of wireless interfaces are available for today's mobile user to access Internet content. When coverage areas of these different technologies overlap, a terminal equipped with multiple interfaces can use them simultaneously to improve the performance of its applications. In this paper, we motivate the advantages that can be had through simultaneous use of multiple interfaces and present a network layer architecture that enables diverse multiaccess services. In particular, we explore in depth one such service provided by the architecture: Bandwidth Aggregation (BAG) for real-time applications. An important aspect of the architecture when providing BAG services for real-time applications is the scheduling algorithm that partitions the traffic onto different interfaces such that the QoS requirements of the application are met. We propose one such algorithm Earliest Delivery Path First (EDPF), that ensures packets meet their playback deadlines by scheduling packets based on the estimated delivery time of the packets. We show through analysis that EDPF performs close to an idealized Aggregated Single Link (ASL) discipline, where the multiple interfaces are replaced by a single interface with same aggregated bandwidth. A prototype implementation and extensive simulations carried using video and delay traces show the performance improvement BAG with EDPF scheduling offers over using just the Highest Bandwidth Interface (HBI) and other scheduling approaches based on weighted round robin.

关键词： network architecture and design video scheduling algorithm/protocol design and analysis implementation simulation

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Buffer Coding for Reliable Transmissions over Wireless Networks

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COMPUTER COMMUNICATIONS 2009年第1期32卷 111-123页

作者： Zheng, Zizhan Sinha, Prasun Ohio State Univ Dept Comp Sci & Engn Dreese Labs Columbus OH 43210 USA

In-network caching is a useful technique for reducing latency and retransmission overhead of lost packets for reliable data delivery in wireless networks. However, in-network caching is challenging to implement in memory constrained devices such as RFIDs and sensors, and also in Wireless LAN (WLAN) gateways for large-scale deployments. In this paper we propose a novel technique for management of in-network caches using XOR coding for optimizing the use of limited buffer space in presence of random and burst packet losses. We identify two critical parameters, coding degree and coding distance for the coding scheme. As a case-study we implement our approach over Snoop and evaluate its performance for WLANs. We further propose a self-adaptive algorithm that tunes coding degree on the fly based on the measured coding behavior and packet loss probability. Using simulations in ns-2, we observe that in our simulation settings, when the size of the retransmission buffer in the gateway is less than 16 packets per TCP flow, the throughput can be enhanced by up to 30% for random losses and up to 20% for burst losses. (C) 2008 Elsevier B.V. All rights reserved.

关键词： Wireless communication algorithm/protocol design and analysis

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A mobile-directory approach to service discovery in wireless ad hoc networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2008年第10期7卷 1242-1256页

作者： Gonzalez-Valenzuela, Sergio Vuong, Son T. Leung, Victor C. M. Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada Chinese Univ Hong Kong Dept Elect Hong Kong Hong Kong Peoples R China Jilin Univ Changchun Peoples R China

We present the Service Directory Placement algorithm (SDPA), a directory-placement scheme that leverages the performance of existing service discovery protocols over wireless ad hoc networks. SDPA promotes the deployment of a nomadic service directory, whose current location in the network varies according to the dynamics of service-discovery queries driven by the users' applications and partial knowledge of the network's topology. SDPA is based on a heuristic approach, whose performance is optimized by formulating the directory-placement problem as a Semi-Markov Decision Process (SMDP) solved by the means of a reinforcement-learning technique known as Q-Learning. Performance evaluations obtained through computer simulations of networks with up to 45 hosts moving at pedestrian speeds reveal average bandwidth savings close to 50 percent over a default broadcast/multicast approach for service discovery once an efficient directory-placement policy is obtained.

关键词： service data communications algorithm/protocol design and analysis ubiquitous computing machine learning

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Back-of-the-Envelope Computation of Throughput Distributions in CSMA Wireless Networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2010年第9期9卷 1319-1331页

作者： Liew, Soung Chang Kai, Cai Hong Leung, Hang Ching (Jason) Wong, Piu (Bill) Chinese Univ Hong Kong Dept Informat Engn Shatin Hong Kong Peoples R China Altai Technol Ltd Shatin Hong Kong Peoples R China

This work started out with our discovery of a pattern of throughput distributions among links in IEEE 802.11 networks from experimental results. This pattern gives rise to an easy computation method, which we term back-of-the-envelop (BoE) computation. For many network configurations, very accurate results can be obtained by BoE within minutes, if not seconds, by simple hand computation. This allows us to make shortcuts in performance evaluation, bypassing complicated stochastic analysis. To explain BoE, we construct a theory based on the model of an "ideal CSMA network" (ICN). The BoE computation method emerges from ICN when we take the limit c -> 0, where c is the ratio of the mean backoff countdown time to the mean transmission time in the CSMA protocol. Importantly, we derive a new mathematical result: the link throughputs of ICN are insensitive to the distributions of the backoff countdown time and transmission time (packet duration) given the ratio of their means c. This insensitivity result explains why BoE works so well for practical 802.11 networks, in which the backoff countdown process is one that has memory, and in which the packet size can be arbitrarily distributed. Our results indicate that BoE is a good approximation technique for modest-size networks such as those typically seen in 802.11 deployments. Beyond explaining BoE, the theoretical framework of ICN is also a foundation for fundamental understanding of very-large-scale CSMA networks. In particular, ICN is similar to the Ising model in statistical physics used to explain phenomena arising out of the interactions of a large number of entities. Many new research directions arise out of the ICN model.

关键词： Access schemes algorithm/protocol design and analysis protocols and wireless

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Exploiting Reactive Mobility for Collaborative Target Detection in Wireless Sensor Networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2010年第3期9卷 317-332页

作者： Tan, Rui Xing, Guoliang Wang, Jianping So, Hing Cheung City Univ Hong Kong Dept Comp Sci Kowloon Hong Kong Peoples R China Michigan State Univ Dept Comp Sci & Engn E Lansing MI 48824 USA City Univ Hong Kong Dept Elect Engn Kowloon Hong Kong Peoples R China

Recent years have witnessed the deployments of wireless sensor networks in a class of mission-critical applications such as object detection and tracking. These applications often impose stringent Quality-of-Service requirements including high detection probability, low false alarm rate, and bounded detection delay. Although a dense all-static network may initially meet these Quality-of-Service requirements, it does not adapt to unpredictable dynamics in network conditions (e. g., coverage holes caused by death of nodes) or physical environments (e. g., changed spatial distribution of events). This paper exploits reactive mobility to improve the target detection performance of wireless sensor networks. In our approach, mobile sensors collaborate with static sensors and move reactively to achieve the required detection performance. Specifically, mobile sensors initially remain stationary and are directed to move toward a possible target only when a detection consensus is reached by a group of sensors. The accuracy of final detection result is then improved as the measurements of mobile sensors have higher Signal-to-Noise Ratios after the movement. We develop a sensor movement scheduling algorithm that achieves near-optimal system detection performance under a given detection delay bound. The effectiveness of our approach is validated by extensive simulations using the real data traces collected by 23 sensor nodes.

关键词： Data fusion algorithm/protocol design and analysis wireless sensor networks

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Optimal Storage Placement for Tree-Structured Networks with Heterogeneous Channel Costs

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IEEE TRANSACTIONS ON COMPUTERS 2011年第10期60卷 1431-1444页

作者： Chiu, Ge-Ming Yen, Li-Hsing Chin, Tai-Lin Natl Taiwan Univ Sci & Technol Dept Comp Sci & Informat Engn Taipei 106 Taiwan Natl Univ Kaohsiung Dept Comp Sci & Informat Engn Kaohsiung 811 Taiwan

This work considers data query applications in tree-structured networks, where a given set of source nodes generate (or collect) data and forward the data to some halfway storage nodes for satisfying queries that call for data generated by all source nodes. The goal is to determine an optimal set of storage nodes that minimizes overall communication cost. Prior work toward this problem assumed homogeneous channel cost, which may not be the case in many network environments. We generalize the optimal storage problem for a tree-structured network by considering heterogeneous channel costs. The necessary and sufficient conditions for the optimal solution are identified, and an algorithm that incurs a linear time cost is proposed. We have also conducted extensive simulations to validate the algorithm and to evaluate its performance.

关键词： algorithm/protocol design and analysis information storage and retrieval network problems

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Biased Random Walks in Uniform Wireless Networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2009年第4期8卷 500-513页

作者： Beraldi, Roberto Univ Roma La Sapienza Dipartimento Informat & Sistemist I-00100 Rome Italy

A recurrent problem when designing distributed applications is to search for a node with known property. File searching in peer-to-peer (P2P) applications, resource discovery in service-oriented architectures (SOAs), and path discovery in routing can all be cast as a search problem. Random walk-based search algorithms are often suggested for tackling the search problem, especially in very dynamic systems-like mobile wireless networks. The cost and the effectiveness of a random walk-based search algorithm are measured by the excepted number of transmissions required before hitting the target. Hence, to have a low hitting time is a critical goal. This paper studies the effect of biasing random walk toward the target on the hitting time. For a walk running over a network with uniform node distribution, a simple upper bound that connects the hitting time to the bias level is obtained. The key result is that even a modest bias level is able to reduce the hitting time significantly. This paper also proposes a search protocol for mobile wireless networks, whose results are interpreted in the light of the theoretical study. The proposed solution is for unstructured wireless mobile networks.

关键词： algorithm/protocol design and analysis random walks mobile ad hoc networks search algorithms

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Optimal resource allocation in overlay multicast

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 2006年第8期17卷 808-823页

作者： Cui, Yi Xue, Yuan Nahrstedt, Klara Vanderbilt Univ Dept Elect Engn & Comp Sci Nashville TN 37325 USA Univ Illinois Dept Comp Sci Urbana IL 61801 USA

Although initially proposed as the deployable alternative to IP multicast, the overlay network actually revolutionizes the way network applications can be built. In this paper, we study the rate allocation problem in overlay-based multirate multicast, which can be understood as a utility-based resource allocation problem. Each receiver is associated with a utility defined as a function of its streaming rate. Our goal is to maximize the aggregate utility of all receivers, subject to network capacity constraint and data constraint. The latter constraint is unique in overlay multicast, mainly due to the dual role of end hosts as both receivers and senders. We use a price-based approach to address this problem. Two types of prices, network price and data price, are generated with regard to the two constraints of the problem. A distributed algorithm is proposed, where each receiver adjusts its flow rate according to the associated network price and data price. The algorithm is proved to converge to the optimal point, where the aggregate utility of all receivers is maximized. We implement our algorithm using an end-host-based protocol. Our protocol purely relies on the coordination of end hosts to accomplish tasks originally assigned to network routers, which makes it directly deployable to the existing network infrastructure.

关键词： multicast algorithm/protocol design and analysis nonlinear programming

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