By Topic

Parallel and Distributed Systems, IEEE Transactions on

Issue 7 • Date July 2014

Filter Results

Displaying Results 1 - 25 of 26
  • Cross-Layer Approach for Minimizing Routing Disruption in IP Networks

    Publication Year: 2014 , Page(s): 1659 - 1669
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (792 KB) |  | HTML iconHTML  

    Backup paths are widely used in IP networks to protect IP links from failures. However, existing solutions such as the commonly used independent model and Shared Risk Link Group (SRLG) model do not accurately reflect the correlation between IP link failures, and thus may not choose reliable backup paths. We propose a cross-layer approach for minimizing routing disruption caused by IP link failures. We develop a probabilistically correlated failure (PCF) model to quantify the impact of IP link failure on the reliability of backup paths. With the PCF model, we propose an algorithm to choose multiple reliable backup paths to protect each IP link. When an IP link fails, its traffic is split onto multiple backup paths to ensure that the rerouted traffic load on each IP link does not exceed the usable bandwidth. We evaluate our approach using real ISP networks with both optical and IP layer topologies. Experimental results show that two backup paths are adequate for protecting a logical link. Compared with existing works, the backup paths selected by our approach are at least 18 percent more reliable and the routing disruption is reduced by at least 22 percent. Unlike prior works, the proposed approach prevents the rerouted traffic from interfering with normal traffic. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Bumping: A Bump-Aided Inertial Navigation Method for Indoor Vehicles Using Smartphones

    Publication Year: 2014 , Page(s): 1670 - 1680
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1436 KB) |  | HTML iconHTML  

    Equipped with accelerometers and gyroscopes, modern smartphones provide an appealing approach to infrastructure-free navigation for vehicles in indoor environments (for example parking garages). However, a smartphone-based inertial navigation system (INS) faces two serious problems. First, it is subject to errors that accumulate over time rather quickly, which may grow to a level that renders the navigation meaningless. Second, without human input or external references, the smartphone can hardly infer its initial position/velocity, which is the basis for distance calculation, since all that a smartphone can learn is its acceleration. This raises a practical concern, as users often need to start indoor navigation precisely when they are uncertain of their current whereabouts. In this paper, we present Bumping , a Bump-Aided Inertial Navigation method that significantly alleviates the above two problems. At the core of this method is a Bump Matching algorithm, which exploits the position information of the readily available speed bumps to provide useful references for the INS. The proposed method is easy to implement, requires no infrastructures, and incurs nearly zero extra energy. We conducted real experiments in tree parking garages of different environmental characteristics. The Bumping method produces an average position error of 4-5 m in these scenarios, improving the accuracy by up to 87.1 percent, compared to the basic inertial navigation method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Constructing Load-Balanced Data Aggregation Trees in Probabilistic Wireless Sensor Networks

    Publication Year: 2014 , Page(s): 1681 - 1690
    Cited by:  Papers (1)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    Data Gathering is a fundamental task in Wireless Sensor Networks (WSNs). Data gathering trees capable of performing aggregation operations are also referred to as Data Aggregation Trees (DATs). Currently, most of the existing works focus on constructing DATs according to different user requirements under the Deterministic Network Model (DNM). However, due to the existence of many probabilistic lossy links in WSNs, it is more practical to obtain a DAT under the realistic Probabilistic Network Model (PNM). Moreover, the load-balance factor is neglected when constructing DATs in current literatures. Therefore, in this paper, we focus on constructing a Load-Balanced Data Aggregation Tree (LBDAT) under the PNM. More specifically, three problems are investigated, namely, the Load-Balanced Maximal Independent Set (LBMIS) problem, the Connected Maximal Independent Set (CMIS) problem, and the LBDAT construction problem. LBMIS and CMIS are well-known NP-hard problems and LBDAT is an NP-complete problem. Consequently, approximation algorithms and comprehensive theoretical analysis of the approximation factors are presented in the paper. Finally, our simulation results show that the proposed algorithms outperform the existing state-of-the-art approaches significantly. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Contiguous Link Scheduling for Data Aggregation in Wireless Sensor Networks

    Publication Year: 2014 , Page(s): 1691 - 1701
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB) |  | HTML iconHTML  

    Wireless sensor networks (WSNs) consist of a large number of battery-powered wireless sensor nodes, and one key issue in WSNs is to reduce the energy consumption while maintaining the normal functions of WSNs. Data aggregation, as a typical operation in data gathering applications, can cause a lot of energy wastage since sensor nodes, when not receiving data, may keep in the listen state during the data collection process. To save this energy wastage, sleep scheduling algorithms can be used to turn the nodes to the sleep state when their radios are not in use and wake them up when necessary. In this paper, we identify the contiguous link scheduling problem in WSNs, in which each node is assigned consecutive time slots so that the node can wake up only once in a scheduling period to fulfil its data collection task. The objective of the problem is to find an interference-free link scheduling with the minimum number of time slots used. In virtue of the contiguous link scheduling, the energy consumption caused by nodes' state transitions can be reduced. We prove the contiguous link scheduling problem in WSNs to be NP-complete, and then present efficient centralized and distributed algorithms with theoretical performance bounds in both homogeneous and heterogeneous networks. We also conduct simulation experiments that corroborate the theoretical results and demonstrate the efficiency of our proposed algorithms. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Distributed Placement of Autonomic Internet Services

    Publication Year: 2014 , Page(s): 1702 - 1712
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (546 KB) |  | HTML iconHTML  

    The optimal placement of service facilities largely determines the capability of a data network to efficiently support its users' service demands. As centralized solutions over large-scale distributed environments are extremely expensive, inefficient or even infeasible, distributed approaches that rely on partial topology and demand information are the only credible approaches to the service placement problem, even at the expense of non-guaranteed optimality. In this paper, we propose a distributed service migration heuristic that iteratively solves instances of the 1-median problem pushing progressively the service to more cost-effective locations. Key to our algorithm is a traffic-aware centrality metric, called weighted conditional betweenness centrality (wCBC), that captures the ability of a node to act as service demand concentrator and is employed in both selecting the nodes and setting their weights for the 1-median problem instance. The assessment of our heuristic proceeds in two steps. First, assuming (ideal) knowledge of the invoked wCBC metric, we carry out a proof-of-concept study that demonstrates the effectiveness of the heuristic over synthetic and real-world topologies as well as its advantages against comparable local-search-like migration schemes. Next, we devise practical protocol implementations that approximate the heuristic using local measurements of transit traffic and preserve the excellent accuracy and fast convergence properties of the algorithm for different routing policies. Our solution applies to a broad range of networking scenarios, and is very relevant to the emerging trends for in-network storage and involvement of the end-user in the creation and distribution of lightweight (autonomic) service facilities. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Distributed Throughput Maximization in Wireless Networks Using the Stability Region

    Publication Year: 2014 , Page(s): 1713 - 1723
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (346 KB) |  | HTML iconHTML  

    In this paper, a game-theoretical framework for the design of distributed algorithms that control the transmission range (TR) of nodes in order to maximize throughput in Wireless Multihop Networks (WMN) is proposed. It is based on the stability region of the link-scheduling policy adopted for the network. The stability region is defined as the set of input-packet rates under which the queues in the network are stable (i.e., positive recurrent). The goal of the TR-control algorithms is to adapt the stability region to a given set of end-to-end flows. In the algorithms, the flows control distributively the nodes' TRs using the stability region in order to enable higher end-to-end packet rates while guaranteeing stability. In order to demonstrate how the algorithms can be designed using the proposed game-theoretical framework, a new TR-control algorithm for IEEE-802.16 WMNs is developed. Its convergence is demonstrated, and a performance bound is calculated. Finally, simulation results show that the algorithm is able to find the optimal TRs more effectively. The TRs achieve throughput levels that are at least 90 percent of the optimal throughput for 72 percent of the simulated scenarios, whereas the classic approach of spatial-reuse maximization does this for 62 percent of the scenarios. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dynamic Aggregate: An Elastic Framework for QoS-Aware Distributed Processing of RFID Data on Enterprise Hierarchy

    Publication Year: 2014 , Page(s): 1724 - 1734
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (734 KB) |  | HTML iconHTML  

    Enterprise RFID data management is highly challenging not only because of the huge volume of data from distributed sources, but particularly because of the dynamic nature of the reader inputs. With user-designated quality of service (QoS) requirements, the data management system must be able to dynamically detect the status changes of the RFID inputs and adjust the processing strategies for continuously maintaining the desired level of QoS. We propose a QoS-aware framework for modeling the enterprise data service problem, and for on-line adaptive processing of distributed RFID data streams. The data processing structure is modeled as a hierarchy of aggregation nodes in accordance with the structure of an organization. Leaf nodes correspond to the RFID streaming inputs. A set of aggregation/deaggregation operations is devised to adjust the processing granularity level based on QoS dynamics. A QoS constrained query issued at any aggregation node is parsed into an aggregation subtree rooted at that node. For QoS-aware processing of the query, several algorithms are designed to dynamically apply proper aggregation/deaggregation operations on selected nodes for raising or lowering the granularity levels or changing the aggregation methods. The goal is to continuously maintain the desired level of QoS under constant variation of the streaming data volume. Prototype development and extensive simulation show that our framework and techniques can handle highly varied RFID streaming inputs and continuously satisfy the QoS constraints. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Expressive, Efficient, and Revocable Data Access Control for Multi-Authority Cloud Storage

    Publication Year: 2014 , Page(s): 1735 - 1744
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (419 KB) |  | HTML iconHTML  

    Data access control is an effective way to ensure the data security in the cloud. Due to data outsourcing and untrusted cloud servers, the data access control becomes a challenging issue in cloud storage systems. Ciphertext-Policy Attribute-based Encryption (CP-ABE) is regarded as one of the most suitable technologies for data access control in cloud storage, because it gives data owners more direct control on access policies. However, it is difficult to directly apply existing CP-ABE schemes to data access control for cloud storage systems because of the attribute revocation problem. In this paper, we design an expressive, efficient and revocable data access control scheme for multi-authority cloud storage systems, where there are multiple authorities co-exist and each authority is able to issue attributes independently. Specifically, we propose a revocable multi-authority CP-ABE scheme, and apply it as the underlying techniques to design the data access control scheme. Our attribute revocation method can efficiently achieve both forward security and backward security. The analysis and simulation results show that our proposed data access control scheme is secure in the random oracle model and is more efficient than previous works. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • From Shortest-Path to All-Path: The Routing Continuum Theory and Its Applications

    Publication Year: 2014 , Page(s): 1745 - 1755
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB) |  | HTML iconHTML  

    As a crucial operation, routing plays an important role in various communication networks. In the context of data and sensor networks, routing strategies such as shortest-path, multi-path and potential-based (“all-path”) routing have been developed. Existing results in the literature show that the shortest path and all-path routing can be obtained from L1 and L2 flow optimization, respectively. Based on this connection between routing and flow optimization in a network, in this paper we develop a unifying theoretical framework by considering flow optimization with mixed (weighted) L1/L2-norms. We obtain a surprising result: as we vary the trade-off parameter θ, the routing graphs induced by the optimal flow solutions span from shortest-path to multi-path to all-path routing-this entire sequence of routing graphs is referred to as the routing continuum. We also develop an efficient iterative algorithm for computing the entire routing continuum. Several generalizations are also considered, with applications to traffic engineering, wireless sensor networks, and network robustness analysis. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Function Computation over Heterogeneous Wireless Sensor Networks

    Publication Year: 2014 , Page(s): 1756 - 1766
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (555 KB) |  | HTML iconHTML  

    The problem of function computation in large scale heterogeneous wireless sensor networks (WSNs) is studied. Suppose n sensors are placed in a disk network area with radius nα, where α is a positive constant. The sensors are located heterogeneously around the sink node, i.e, the density of sensors decreases as the distance from the sink node increases. At one instant, each sensor is assigned an input bit. The target of the sink is to compute a function f of the input bits, where f is either a symmetric or the identity function. Energy-efficient algorithms based on inhomogeneous tessellation of the network are designed and the corresponding optimal energy consumption scaling laws are derived. We show that the proposed algorithms are indeed optimal (except for some polylogarithmic terms) by deriving matching lower bounds on the energy consumption required to compute f. At last, based on the results obtained in this paper as well as those obtained by previous works, some discussions and comparisons are presented. We observe that 1) the heterogeneity extent has a great impact on the computation of both symmetric function and identity function, and 2) the energy usage of computing symmetric function can be significantly smaller than that of computing identity function under certain parameter condition, i.e, performing in-network computation helps save energy. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Further Observations on Smart-Card-Based Password-Authenticated Key Agreement in Distributed Systems

    Publication Year: 2014 , Page(s): 1767 - 1775
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (286 KB) |  | HTML iconHTML  

    This paper initiates the study of two specific security threats on smart-card-based password authentication in distributed systems. Smart-card-based password authentication is one of the most commonly used security mechanisms to determine the identity of a remote client, who must hold a valid smart card and the corresponding password to carry out a successful authentication with the server. The authentication is usually integrated with a key establishment protocol and yields smart-card-based password-authenticated key agreement. Using two recently proposed protocols as case studies, we demonstrate two new types of adversaries with smart card: 1) adversaries with pre-computed data stored in the smart card, and 2) adversaries with different data (with respect to different time slots) stored in the smart card. These threats, though realistic in distributed systems, have never been studied in the literature. In addition to point out the vulnerabilities, we propose the countermeasures to thwart the security threats and secure the protocols. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Link Quality Aware Code Dissemination in Wireless Sensor Networks

    Publication Year: 2014 , Page(s): 1776 - 1786
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB) |  | HTML iconHTML  

    Wireless reprogramming is a crucial technique for software deployment in wireless sensor networks (WSNs). Code dissemination is a basic building block to enable wireless reprogramming. We present ECD, an Efficient Code Dissemination protocol leveraging 1-hop link quality information based on the TinyOS platform. Compared to prior works, ECD has three salient features. First, it supports dynamically configurable packet sizes. By increasing the packet size for high PHY rate radios, it significantly improves the transmission efficiency. Second, it employs an accurate sender selection algorithm to mitigate transmission collisions and transmissions over poor links. Third, it employs a simple impact-based backoff timer design to shorten the time spent in coordinating multiple eligible senders so that the largest impact sender is most likely to transmit. We implement ECD based on TinyOS and evaluate its performance extensively via testbed experiments and simulations. Results show that ECD outperforms state-of-the-art protocols, Deluge and MNP, in terms of completion time and data traffic (e.g., about 20 percent less traffic and 20-30 percent shorter completion time compared to Deluge). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Meeting Deadlines of Scientific Workflows in Public Clouds with Tasks Replication

    Publication Year: 2014 , Page(s): 1787 - 1796
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (595 KB) |  | HTML iconHTML  

    The elasticity of Cloud infrastructures makes them a suitable platform for execution of deadline-constrained workflow applications, because resources available to the application can be dynamically increased to enable application speedup. Existing research in execution of scientific workflows in Clouds either try to minimize the workflow execution time ignoring deadlines and budgets or focus on the minimization of cost while trying to meet the application deadline. However, they implement limited contingency strategies to correct delays caused by underestimation of tasks execution time or fluctuations in the delivered performance of leased public Cloud resources. To mitigate effects of performance variation of resources on soft deadlines of workflow applications, we propose an algorithm that uses idle time of provisioned resources and budget surplus to replicate tasks. Simulation experiments with four well-known scientific workflows show that the proposed algorithm increases the likelihood of deadlines being met and reduces the total execution time of applications as the budget available for replication increases. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Memory-Aware Task Scheduling with Communication Overhead Minimization for Streaming Applications on Bus-Based Multiprocessor System-on-Chips

    Publication Year: 2014 , Page(s): 1797 - 1807
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (669 KB) |  | HTML iconHTML  

    Inter-core communication introduces overheads in task schedules on Multiprocessor System-on-Chips (MPSoCs). Inter-core communication overhead not only negatively impacts the timing performance but also significantly degrades the memory usage for streaming applications running on MPSoC architectures. By minimizing inter-core communication overhead, a shorter period can be applied and system performance (e.g., throughput, memory usage) can be improved. In this paper, we focus on solving the problem of minimizing inter-core communication overhead for streaming applications on bus-based MPSoCs. The objective is to minimize inter-core communication overhead while minimizing the overall memory usage. To solve the problem, we first let tasks with intra-period data dependencies transform to inter-period data dependencies so as to overlap the execution of computation and inter-core communication tasks. By doing this, inter-core communication overhead can be effectively removed. To minimize the overall memory usage, we then perform schedulability analysis and obtain the bounds of the times needed to reschedule each task. Based on the schedulability analysis, we formulate the scheduling problem as an integer linear programming (ILP) model and obtain an optimal schedule. In addition, we propose a heuristic approach to efficiently obtain a near-optimal solution. We conduct experiments on a set of benchmarks from both real-life streaming applications and synthetic task graphs. The experimental results show that the proposed approach can significantly reduce the schedule length and improve the memory usage compared with the previous work. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multicast Capacity in MANET with Infrastructure Support

    Publication Year: 2014 , Page(s): 1808 - 1818
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (243 KB) |  | HTML iconHTML  

    We study the multicast capacity under a network model featuring both node's mobility and infrastructure support. Combinations between mobility and infrastructure, as well as multicast transmission and infrastructure, have already showed effective ways to increase multicast capacity. In this work, we jointly consider the impact of the above three factors on network capacity. We assume that m static base stations and n mobile users are placed in an ad hoc network. A general mobility model is adopted, such that each user moves within a bounded distance from its home-point with an arbitrary pattern. In addition, each mobile node serves as a source of multicast transmission, which results in a total number of n multicast transmissions. We focus on the situations in which base stations actually benefit the capacity improvement, and find that multicast capacity in a mobile hybrid network falls into several regimes. For each regime, reachable upper and lower bounds are derived. Our work contains theoretical analysis of multicast capacity in hybrid networks and provides guidelines for the design of real hybrid systems combing cellular and ad hoc networks. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Omnidirectional Coverage for Device-Free Passive Human Detection

    Publication Year: 2014 , Page(s): 1819 - 1829
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (923 KB) |  | HTML iconHTML  

    Device-free Passive (DfP) human detection acts as a key enabler for emerging location-based services such as smart space, human-computer interaction, and asset security. A primary concern in devising scenario-tailored detecting systems is coverage of their monitoring units. While disk-like coverage facilitates topology control, simplifies deployment analysis, and is crucial for proximity-based applications, conventional monitoring units demonstrate directional coverage due to the underlying transmitter-receiver link architecture. To achieve omnidirectional coverage under such link-centric architecture, we propose the concept of omnidirectional passive human detection. The rationale is to exploit the rich multipath effect to blur the directional coverage. We harness PHY layer features to robustly capture the fine-grained multipath characteristics and virtually tune the shape of the coverage of the monitoring unit, which is previously prohibited with mere MAC layer RSSI. We design a fingerprinting scheme and a threshold-based scheme with off-the-shelf WiFi infrastructure and evaluate both schemes in typical clustered indoor scenarios. Experimental results demonstrate an average false positive of 8 percent and an average false negative of 7 percent for fingerprinting in detecting human presence in 4 directions. And both average false positive and false negative remain around 10 percent even with threshold-based methods. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the Speedup of Recovery in Large-Scale Erasure-Coded Storage Systems

    Publication Year: 2014 , Page(s): 1830 - 1840
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (526 KB) |  | HTML iconHTML  

    Modern storage systems stripe redundant data across multiple nodes to provide availability guarantees against node failures. One form of data redundancy is based on XOR-based erasure codes, which use only XOR operations for encoding and decoding. In addition to tolerating failures, a storage system must also provide fast failure recovery to reduce the window of vulnerability. This work addresses the problem of speeding up the recovery of a single-node failure for general XOR-based erasure codes. We propose a replace recovery algorithm, which uses a hill-climbing technique to search for a fast recovery solution, such that the solution search can be completed within a short time period. We further extend the algorithm to adapt to the scenario where nodes have heterogeneous capabilities (e.g., processing power and transmission bandwidth). We implement our replace recovery algorithm atop a parallelized architecture to demonstrate its feasibility. We conduct experiments on a networked storage system testbed, and show that our replace recovery algorithm uses less recovery time than the conventional recovery approach. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Order-Optimal Information Dissemination in MANETs via Network Coding

    Publication Year: 2014 , Page(s): 1841 - 1851
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    Motivated by various applications in mobile ad-hoc networks (MANETs) that require nodes to share their individual information to each other, we study the multi-message dissemination problem in a MANET, which is to distribute multiple messages to all mobile nodes in the network in parallel. The objective is to minimize the stopping time, i.e., the time taking for all nodes to receive a copy of the whole messages. We consider an intrinsically one-sided protocol based on random linear network coding (RLNC), where all packets forwarded are in the form of random linear combinations of packets received so far. Its supreme performance is demonstrated theoretically for two cases, low mobility and high mobility, according to the node velocity. In particular, we show that, under general settings, our derived upper bounds of the stopping time match the established lower bound in both cases, although the effects of mobility in the two cases are significantly different. Thus, we conclude that RLNC achieves order optimality for fast information dissemination in MANETs. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Peer-Assisted VoD Systems: An Efficient Modeling Framework

    Publication Year: 2014 , Page(s): 1852 - 1863
    Cited by:  Papers (1)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (419 KB) |  | HTML iconHTML  

    We analyze a peer-assisted Video-on-Demand (VoD) system in which users contribute their upload bandwidth to the redistribution of a video that they are downloading or that they have cached locally. Our target is to characterize the additional bandwidth that servers must supply to immediately satisfy all requests to watch a given video. We develop an approximate fluid model to compute the required server bandwidth in the sequential delivery case, as well as in controlled nonsequential swarms. Our approach is able to capture several stochastic effects related to peer churn, upload bandwidth heterogeneity, and nonstationary traffic conditions, which have not been documented or analyzed before. Finally, we provide important hints for the design of efficient peer-assisted VoD systems under server capacity constraints. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • QoS Aware Geographic Opportunistic Routing in Wireless Sensor Networks

    Publication Year: 2014 , Page(s): 1864 - 1875
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1007 KB) |  | HTML iconHTML  

    QoS routing is an important research issue in wireless sensor networks (WSNs), especially for mission-critical monitoring and surveillance systems which requires timely and reliable data delivery. Existing work exploits multipath routing to guarantee both reliability and delay QoS constraints in WSNs. However, the multipath routing approach suffers from a significant energy cost. In this work, we exploit the geographic opportunistic routing (GOR) for QoS provisioning with both end-to-end reliability and delay constraints in WSNs. Existing GOR protocols are not efficient for QoS provisioning in WSNs, in terms of the energy efficiency and computation delay at each hop. To improve the efficiency of QoS routing in WSNs, we define the problem of efficient GOR for multiconstrained QoS provisioning in WSNs, which can be formulated as a multiobjective multiconstraint optimization problem. Based on the analysis and observations of different routing metrics in GOR, we then propose an Efficient QoS-aware GOR (EQGOR) protocol for QoS provisioning in WSNs. EQGOR selects and prioritizes the forwarding candidate set in an efficient manner, which is suitable for WSNs in respect of energy efficiency, latency, and time complexity. We comprehensively evaluate EQGOR by comparing it with the multipath routing approach and other baseline protocols through ns-2 simulation and evaluate its time complexity through measurement on the MicaZ node. Evaluation results demonstrate the effectiveness of the GOR approach for QoS provisioning in WSNs. EQGOR significantly improves both the end-to-end energy efficiency and latency, and it is characterized by the low time complexity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Robust Trajectory Estimation for Crowdsourcing-Based Mobile Applications

    Publication Year: 2014 , Page(s): 1876 - 1885
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (916 KB) |  | HTML iconHTML  

    Crowdsourcing-based mobile applications are becoming more and more prevalent in recent years, as smartphones equipped with various built-in sensors are proliferating rapidly. The large quantity of crowdsourced sensing data stimulates researchers to accomplish some tasks that used to be costly or impossible, yet the quality of the crowdsourced data, which is of great importance, has not received sufficient attention. In reality, the low-quality crowdsourced data are prone to containing outliers that may severely impair the crowdsourcing applications. Thus in this work, we conduct pioneer investigation considering crowdsourced data quality. Specifically, we focus on estimating user motion trajectory information, which plays an essential role in multiple crowdsourcing applications, such as indoor localization, context recognition, indoor navigation, etc. We resort to the family of robust statistics and design a robust trajectory estimation scheme, name TrMCD, which is capable of alleviating the negative influence of abnormal crowdsourced user trajectories, differentiating normal users from abnormal users, and overcoming the challenge brought by spatial unbalance of crowdsourced trajectories. Two real field experiments are conducted and the results show that TrMCD is robust and effective in estimating user motion trajectories and mapping fingerprints to physical locations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Taxonomy of Attacks for Agent-Based Smart Grids

    Publication Year: 2014 , Page(s): 1886 - 1895
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (434 KB) |  | HTML iconHTML  

    Being the most important critical infrastructure in Cyber-Physical Systems (CPSs), a smart grid exhibits the complicated nature of large scale, distributed, and dynamic environment. Taxonomy of attacks is an effective tool in systematically classifying attacks and it has been placed as a top research topic in CPS by a National Science Foundation (NSG) Workshop. Most existing taxonomy of attacks in CPS are inadequate in addressing the tight coupling of cyber-physical process or/and lack systematical construction. This paper attempts to introduce taxonomy of attacks of agent-based smart grids as an effective tool to provide a structured framework. The proposed idea of introducing the structure of space-time and information flow direction, security feature, and cyber-physical causality is innovative, and it can establish a taxonomy design mechanism that can systematically construct the taxonomy of cyber attacks, which could have a potential impact on the normal operation of the agent-based smart grids. Based on the cyber-physical relationship revealed in the taxonomy, a concrete physical process based cyber attack detection scheme has been proposed. A numerical illustrative example has been provided to validate the proposed physical process based cyber detection scheme. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Towards Providing Scalable and Robust Privacy in Vehicular Networks

    Publication Year: 2014 , Page(s): 1896 - 1906
    Cited by:  Papers (1)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (978 KB) |  | HTML iconHTML  

    In vehicular networks, there is a strong correlation between a vehicle's identity and that of the driver. It follows that any effort to protect driver privacy must attempt to make the link between the two harder to detect. One of the most appealing solutions to hiding the identity of a vehicle is the use of pseudonyms, whereby each vehicle is issued one or several temporary identities (i.e., pseudonyms) that it uses to communicate with other vehicles and/or the roadside infrastructure. Due to the large number of vehicles on our roadways and city streets and of the sophistication of possible attacks, privacy protection must be both scalable and robust. The first main contribution of this work is to take a nontrivial step towards providing a scalable and robust solution to privacy protection in vehicular networks. To promote scalability and robustness we employ two strategies. First, we view vehicular networks as consisting of nonoverlapping subnetworks, each local to a geographic area referred to as a cell. Depending on the topology and the nature of the area, these cells may be as large as few city blocks or, indeed, may comprise the entire downtown area of a small town. Each cell has a server that maintains a list of pseudonyms valid for use in the cell. Instead of issuing pseudonyms to vehicles proactively, as virtually all existing schemes do, we issue pseudonyms only to those vehicles that request them. Our second main contribution is to model analytically the time-varying request for pseudonyms in a given cell. This is important for capacity planning purposes since it allows system managers to predict, by taking into account the time-varying attributes of the traffic, the probability that a given number of pseudonyms will be required at a certain time as well as the expected number of pseudonyms in use in a cell at a certain time. Empirical results obtained by detailed simulation confirmed the accuracy of our analytical predictions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Views in a Graph: To Which Depth Must Equality Be Checked?

    Publication Year: 2014 , Page(s): 1907 - 1912
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (241 KB) |  | HTML iconHTML  

    The view of depth k of a node is a tree containing all the walks of length k leaving that node. Views contain all the information that nodes could obtain by exchanging messages with their neighbors. In particular, a value can be computed by a node on a network using a distributed deterministic algorithm if and only if that value only depends on the node's view of the network. Norris has proved that if two nodes have the same view of depth n - 1, they have the same views for all depths. Taking the diameter d into account, we prove a new bound in O(d + d log(n/d)) instead of n - 1 for bidirectional graphs with port numbering, which are natural models in distributed computation. This automatically improves various results relying on Norris's bound. We also provide a bound that is stronger for certain colored graphs and extend our results to graphs containing directed edges. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Web Service Recommendation via Exploiting Location and QoS Information

    Publication Year: 2014 , Page(s): 1913 - 1924
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB) |  | HTML iconHTML  

    Web services are integrated software components for the support of interoperable machine-to-machine interaction over a network. Web services have been widely employed for building service-oriented applications in both industry and academia in recent years. The number of publicly available Web services is steadily increasing on the Internet. However, this proliferation makes it hard for a user to select a proper Web service among a large amount of service candidates. An inappropriate service selection may cause many problems (e.g., ill-suited performance) to the resulting applications. In this paper, we propose a novel collaborative filtering-based Web service recommender system to help users select services with optimal Quality-of-Service (QoS) performance. Our recommender system employs the location information and QoS values to cluster users and services, and makes personalized service recommendation for users based on the clustering results. Compared with existing service recommendation methods, our approach achieves considerable improvement on the recommendation accuracy. Comprehensive experiments are conducted involving more than 1.5 million QoS records of real-world Web services to demonstrate the effectiveness of our approach. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Transactions on Parallel and Distributed Systems (TPDS) is published monthly. It publishes a range of papers, comments on previously published papers, and survey articles that deal with the parallel and distributed systems research areas of current importance to our readers.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
David Bader
College of Computing
Georgia Institute of Technology