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Distributed Computing in Sensor Systems (DCOSS), 2012 IEEE 8th International Conference on

Date 16-18 May 2012

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  • DCOSS 2012 - IEEE International Conference on Distributed Computing in Sensor Systems [Cover art]

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  • [Title page i]

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  • Proceedings IEEE International Conference on Distributed Computing in Sensor Systems - DCOSS 2012 [Title Page iii]

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  • Copyright (c) 2012 by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved. [Copyright page]

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  • 2012 8th IEEE International Conference on Distributed Computing in Sensor Systems - DCOSS 2012 - Table of contents

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  • DCOSS 2012 Foreword

    Page(s): xi
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  • Conference Organization

    Page(s): xii - xiii
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  • [Keynotes]

    Page(s): xiv - xv
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    Summary form only given. Provides abstracts for the articles appearing in the conference proceedings CD. View full abstract»

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  • Should I Stay or Should I Go? Maximizing Lifetime with Relays

    Page(s): 1 - 8
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    As sensor mobility becomes more and more universal, Wireless Sensor Network (WSN) configurations that utilize such mobility will become the norm. We consider the problem of maximizing the lifetime of a wireless connection between a transmitter and a receiver using mobile relays. Initially, all relays are positioned arbitrarily on the line between the transmitter and the receiver and have arbitrary battery capacities. Energy is consumed in proportion to the distance traveled for mobility and in proportion to an exponential function of the distance over which information is sent for communication. Relays can move to different locations as long as they have the energy to do so. The objective is to find positions and thus transmission ranges for the nodes that maximize the lifetime of the network. We study two models. The first is more restrictive, and corresponds to the case where relays are allowed to be set once at time zero (single deployment), while the second model corresponds to the case where relays can be adjusted multiple times (multiple deployments). We show how to compute an optimal solution for the case of no movement cost for both models. We consider a discrete version of the single deployment model, in which relays must be deployed on grid points. We provide two algorithms for this case: a dynamic programming algorithm and a binary search algorithm on potential lifetimes. We prove that both algorithms are FPTASs for the non-discrete problem, if batteries are not too small. Based on these algorithms and on additional ideas we develop a number of heuristics for the multiple deployments model. We evaluate them using simulations and compare them with the lower bound of relays not moving at all and the upper bound of cost-free movement. Our simulations - across a range of mobility and transmission costs, sensible starting locations and battery capacities - demonstrate the benefit of moving over remaining at initial locations even for single deployment. View full abstract»

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  • Network Lifetime Maximization in Delay-Tolerant Sensor Networks with a Mobile Sink

    Page(s): 9 - 16
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    In this paper we investigate the network lifetime maximization problem in a delay-tolerant wireless sensor network with a mobile sink by exploiting a nontrivial tradeoff between the network lifetime and the data delivery delay. We formulate the problem as a joint optimization problem that consists of finding a trajectory for the mobile sink and designing an energy-efficient routing protocol to route sensing data to the sink, subject to the bounded delay on data delivery and the given potential sink location space. Due to NP-hardness of the problem, we then propose a novel optimization framework, which not only prolongs the network lifetime but also improves the other performance metrics including the network scalability, robustness, and the average delivery delay. We finally conduct extensive experiments by simulations to evaluate the performance of the proposed algorithm against other heuristics. The experimental results demonstrate that the proposed algorithm outperforms the others significantly in terms of network lifetime prolongation. View full abstract»

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  • Achieving High Lifetime and Low Delay in Very Large Sensors Networks Using Mobile Sinks

    Page(s): 17 - 24
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    For smaller scale wireless sensor networks (WSN) it has been clearly shown that a single mobile sink can be very beneficial with respect to the network lifetime. Yet, how to plan the trajectories of many mobile sinks in very large WSNs in order to simultaneously achieve lifetime and delay goals has not been treated so far. In this paper, we delve into this difficult problem and propose a heuristic framework using multiple orbits for the sinks' trajectories. The framework is carefully designed based on geometric arguments to achieve both, high lifetime and low delay. In simulations, we compare two different instances of our framework, one conceived based on a load balancing argument and one based on a distance minimization argument, with a set of different competitors spanning from statically placed sinks to battery-state aware strategies. We find our heuristics to perform very favorably: both instances outperform the competitors in both, lifetime and delay. Furthermore, and probably even more importantly, the heuristic, while keeping its good delay and lifetime performance, scales well with an increasing number of sinks. View full abstract»

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  • Efficient Mobile Data Collection with Mobile Collect

    Page(s): 25 - 32
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    The main task of most deployed wireless sensor networks is data collection. While a number of solutions have been designed for static networks, there are currently no widely used data collection algorithms for mobile sensor networks. In this paper, we concentrate on scenarios where many nodes, both data sources and sinks, move along a certain track in one direction, a scenario that is common in sports events. Rather than designing a new protocol from scratch, we extend an existing data collection protocol with lightweight mechanisms to make it efficient for mobility. Our extensive simulations and results in a test bed that includes mobile robots demonstrate that our solution is able to achieve high packet delivery rates at low energy consumption. For our target scenario, our solution more than doubles packet delivery rates when the network is sparse. Our solution also works well in scenarios with a higher degree of mobility where nodes move according to a more demanding random waypoint model. View full abstract»

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  • Throughput Maximization in Mobile WSN Scheduling with Power Control and Rate Selection

    Page(s): 33 - 40
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (243 KB) |  | HTML iconHTML  

    We study a data dissemination scenario in which data items are to be transmitted to mobile clients via one of the stationary data access points (APs) that the clients pass by en route to their destinations. The scheduler dedicates sequences of consecutive timeslots of an AP to downloading a data item to a client during the time window in which it is in range, which corresponds to assigning a job (the client's download) to a machine (the AP) among many. The transmission rate chosen for each assignment partly corresponds to setting a machine's speed, but it also has subtler effects. The APs may control transmission power to tune its transmission range making sure that no interference occurs with neighboring APs' transmissions. The problem is a generalization of an already NP-hard parallel-machine scheduling problem in which jobs' release times and deadlines depend on the machine to which they are assigned. We define this joint timeslot, power control, and rate assignment problem formally and apply both new algorithms and adaptations of existing algorithms to it. We evaluate these algorithms through simulations which show that our proposed algorithms achieve near-optimal throughput. View full abstract»

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  • Coverage Estimation in Heterogeneous Visual Sensor Networks

    Page(s): 41 - 49
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    Coverage estimation is one of the fundamental issues in many applications of sensor networks. Coverage estimation in visual sensor networks (VSNs) is more challenging than in conventional 1-D scalar sensor networks (SSNs) due to the directional sensing characteristic of cameras and the existence of visual occlusions in crowded environments. Moreover, deployment of heterogeneous visual sensors and existence of heterogeneous targets in the sensing field makes the coverage estimation problem even more challenging. In this paper, we study the coverage estimation problem in heterogeneous VSNs. We first investigate into a new target detection model, referred to as the "certainty-based target detection" as compared to the traditional "occupancy-based target detection" to facilitate the formulation of the visual coverage estimation. By adopting the new target detection model, we then derive the closed-form solution for the visual coverage estimation problem in heterogeneous VSNs. Our formulation also allows us to take both the presence of visual occlusions and boundary effect into consideration. Results from simulation validate the theoretical formulation, especially when the boundary effect is considered. View full abstract»

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  • Adaptive Synchronization Control with Multi-level Buffer in Wireless Multimedia Sensor Networks

    Page(s): 50 - 57
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    In Wireless Multimedia Sensor Networks (WMSNs), data fusion and collaborative in-network processing operations often require effective multimedia synchronization control. Extensive researches have been done in the traditional networks. Most of these works assume that there exists a powerful synchronization controller in the network. However, for WMSNs, the in-network processing of the multimedia content is usually performed based on the resource-constrained sensors. Traditional synchronization control algorithms fail to run on the low-end hardware platform. In this paper, we propose an adaptive synchronization control scheme with multi-level buffer to address this problem. Main contributions of this paper are as follows. (i) To overcome the resource constraint of WMSNs, we perform the synchronization control in a distributed way by combining the sensors in the stream transmission path. (ii) By evaluating the current network state, we adjust the level number of the buffer adaptively to balance the delay and delay jitter. (iii) Through analyzing the buffer state of each level, we propose an efficient packet scheduling scheme to reduce the delay jitter actively. (iv) We implement the proposed scheme and verify its effectiveness in our practical WMSNs platform. The experiment results show that the proposed scheme can maintain the streams synchronization effectively with the low-end sensors. View full abstract»

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  • LoCaF: Detecting Real-World States with Lousy Wireless Cameras

    Page(s): 58 - 66
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    The Internet of Things (IoT) integrates wireless sensors to provide online and real-time access to the state of things and places. However, many interesting real-world states are difficult to detect with traditional scalar sensors. Tiny wireless camera sensor nodes are an interesting alternative as a single camera can observe a large area in great detail. However, low image resolution, poor image quality, and low frame rates as well as varying lighting conditions in outdoor scenarios make the detection of real-world states using these lousy cameras a challenging problem. In this paper we introduce a framework that addresses this problem by providing an end-to-end solution that includes energy-efficient image capture, image enhancement to mitigate low picture quality, object detection with low frame rates, inference of high-level states, and publishing of these states on the IoT. The framework can be flexibly configured by end-users without programming skills and supports a variety of different applications. View full abstract»

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  • Kinsight: Localizing and Tracking Household Objects Using Depth-Camera Sensors

    Page(s): 67 - 74
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    We solve the problem of localizing and tracking household objects using a depth-camera sensor network. We design and implement Kin sight that tracks household objects indirectly -- by tracking human figures, and detecting and recognizing objects from human-object interactions. We devise two novel algorithms: (1) Depth Sweep -- that uses depth information to efficiently extract objects from an image, and (2) Context Oriented Object Recognition -- that uses location history and activity context along with an RGB image to recognize object sat home. We thoroughly evaluate Kinsight's performance with a rich set of controlled experiments. We also deploy Kinsightin real-world scenarios and show that it achieves an average localization error of about 13 cm. View full abstract»

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  • Timely Report Delivery in Social Swarming Applications

    Page(s): 75 - 82
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    In social swarming applications, participants equipped with 3G and WiFi-capable smart phones are tasked to provide reports (possibly voluminous ones that include full-motion video) about their immediate environment to a central coordinator. In this paper, we consider the problem of timely delivery of these reports: each report has an associated deadline and the goal of the system is to retrieve as many reports as possible (or retrieve the most valuable reports), while satisfying each report's deadline. Reporters can use their cellular interface to upload their reports, but can also ask neighbors (using their faster WiFi interface) to help upload parts of their reports. Under an assumption that WiFi transmission delays are negligible, we first show that there exists a polynomial time optimal solution using an earliest-deadline-first (EDF) strategy for achieving the goals described above. In practice, WiFi delays are not negligible: in this case, it turns out that the scheduling problem is strongly NP-hard. We formulate two heuristic algorithms, and show, through simulations with real-world measurements, that these heuristics perform 2-4× better than without peer-assistance, and within 60% of an upper-bound on the optimal. View full abstract»

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  • Personal Marks and Community Certificates: Detecting Clones in Wireless Mobile Social Networks

    Page(s): 83 - 91
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (269 KB) |  | HTML iconHTML  

    We consider the problem of detecting clones in wireless mobile ad-hoc networks. We assume that one of the devices of the network has been cloned. Everything, including saved passwords, certificates and secret keys. We propose a solution in networks of mobile devices carried by individuals - composed by nodes that can communicate by short-range technology like bluetooth or Wi-Fi, and links appear and disappear according to social relationships between users. Our idea is to use social physical contacts, securely collected by wireless personal smart phones, as a biometric way to authenticate the owner of the device and detect the clone attack. We introduce two mechanisms: Personal Marks and Community Certificates. Personal Marks is a simple cryptographic protocol that works well when the adversary is an insider, a malicious node in the network that tries to use the stolen credentials in the social community of the original device that has been cloned. Community Certificates works well when the adversary is an outsider, a node that has the goal of using the stolen credentials when interacting with other nodes that are far in the social network from the original device. When combined, these mechanisms provide an excellent protection against this very strong attack. We prove our ideas and solutions with extensive simulations in both simulated and real world scenarios - with mobility traces collected in a real life experiment. View full abstract»

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  • A Mobile Terminal Based Trajectory Preserving Strategy for Continuous Querying LBS Users

    Page(s): 92 - 98
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    Location privacy is one critical factor concerned by mobile users of Location Based Service (LBS). Location privacy of mobile users includes two parts: current position information and trajectory information. The problem of position anonymity in Ad Hoc & sensor networks has been widely studied during past years. Nevertheless, most of existing privacy preserving solutions either need a third part server or require a large number of users. This paper proposes a simple and distributed trajectory preserving strategy, called Virtual Avatar (VAvatar). VAvater adopts a virtual path programming resolution, which does not need any third-part server (agent), to achieve trajectory information anonymity for continuous querying users of LBS. On the other hand, attackers may have strong ability to make mobility predictions by analyzing spatio-temporal relation of historical communication data. In order to prevent users from such threatening, VAvatar takes following two strategies: noisy location selecting strategy and query scheduling strategy to interrupt spacial and temporal relationships between position data. Theoretical analysis and experiments show that VAvatar provides efficient protection of trajectory privacy for mobile users with tolerable energy cost. View full abstract»

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  • A Ubiquitous Publish/Subscribe Platform for Wireless Sensor Networks with Mobile Mules

    Page(s): 99 - 108
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    Existing publish/subscribe architectures for wireless sensors networks only support stationary sensors interconnected with each other. They cannot handle mobile sensors or remote sensors that are sparsely deployed. In this paper, we propose a novel ubiquitous publish/subscribe system that supports data access from both mobile sensors and stationary sensors. Our system utilizes mobile phones as data mules to relay subscriptions and published data between broker and remote sensors. It provides content-based publish/subscribe services from sensors deployed anywhere without depending on any network infrastructure. We implement our publish/subscribe platform on real hardwares and test it in a hiking trail application. The application allows users to subscribe for sensing data from both stationary sensors and mobile sensors along hiking trails. Extensive experiments are conducted in an outdoor testbed to evaluate the system performances such data delay, number of data received and communication overhead. View full abstract»

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  • Power-Efficient Algorithms for Fourier Analysis over Random Wireless Sensor Network

    Page(s): 109 - 115
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    Reduced execution time and increased power efficiency are important objectives in the distributed execution of collaborative signal processing tasks over wireless sensor networks. The power-efficient implementation of the Fourier transform computation is an exemplar of distributed data communication and processing task widely used in the signal processing field. Past work has presented some energy-efficient in-network Fourier transform computation algorithms devised only for uniformly sampled one-dimensional (1D) sensor data. However the circumstance that sensors are randomly distributed over a 2D plane may be more practical, therefore the conventional two-dimensional Fast Fourier Transform (2D FFT) defined for data sampled on uniform grids is not directly applicable in such environments. We address this problem by designing a distributed hybrid structure consisting of local Nonequispaced Discrete Fourier Transform (NDFT) and global FFT computation. Firstly, NDFT method is applied in a suitable choice of clusters to get the initial uniform Fourier coefficients with allowable estimation error bounds. We experiment with classical linear as well as generalized interpolation methods to compute NDFT coefficients within each cluster. A separable 2D FFT is then performed over all these clusters by employing our proposed energy-efficient 1D FFT computation that reduces communication costs using a novel bit index mapping strategy for data exchanges between sensors. The proposed techniques are implemented in a SID net-SWANS platform to investigate the communication costs, execution time, and energy consumption. Our results show reduced execution time and improved energy consumption when compared with existing work. View full abstract»

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  • Distributed Subspace Projection in Wireless Sensor Networks Using Computational Codes

    Page(s): 116 - 123
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    In this paper, we develop a new power-efficient algorithm for Wireless Sensor Networks (WSN) in order to obtain, in a distributed manner, the Projection of an observed sampled spatial field on a subspace of lower dimension. This is an important problem that is motivated in various applications where there are well defined subspaces of interest (e.g. spectral maps in cognitive radios). As opposed to traditional Gossip Algorithms used for subspace projection assuming separation of channel coding and computation, our algorithm combines Computational Coding and a modification of existing Gossip Algorithms, achieving important savings in convergence time and yielding an exponential decrease in energy consumption as the size of the network increases. View full abstract»

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  • In-Network Computation of the Transition Matrix for Distributed Subspace Projection

    Page(s): 124 - 131
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    In this paper, we develop a novel strategy to compute the transition matrix for the projection problem in a distributed fashion through gossiping in Wireless Sensor Networks. So far, the transition matrix had to be computed off-line by a third party and then provided to the network. The Subspace Projection Problem is useful in various application scenarios (e.g. spectral spatial maps in cognitive radios) and consists of projecting the observed sampled spatial field into a subspace of interest with lower dimension. Although the actual exact computation of the optimal transition matrix is not feasible in a distributed way, we develop an algorithm that is based on well known results from linear algebra and a distributed genetic algorithm in order to compute an approximation of the optimal matrix to a desired precision. View full abstract»

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  • An O(log n) Distributed Approximation Algorithm for Local Broadcasting in Unstructured Wireless Networks

    Page(s): 132 - 139
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    The unstructured multi-hop radio network model, with asynchronous wake-up, no collision detection and little knowledge on the network topology, is proposed for capturing the particularly harsh characteristics of initially deployed wireless adhoc and sensor networks. In this paper, assuming such a practical model, we study a fundamental problem of both theoretical and practical interests--the local broadcasting problem. Given a set of nodes V where each node wants to broadcast a message to all its neighbors that are within a certain local broadcasting range R, the problem is to schedule all these requests in the fewest timeslots. By adopting the physical interference mode land without any knowledge on neighborhood, we give a new randomized distributed approximation algorithm for the local broadcasting problem with approximation ratio O (log n) where nis the number of nodes. This distributed approximation algorithm improves the state-of-the-art result in [22] by a logarithmic factor. View full abstract»

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