By Topic

Parallel and Distributed Systems, IEEE Transactions on

Issue 4 • Date April 2013

Filter Results

Displaying Results 1 - 21 of 21
  • Editor's note: Reviewer appreciation program

    Page(s): 625 - 628
    Save to Project icon | Request Permissions | PDF file iconPDF (165 KB)  
    Freely Available from IEEE
  • A Secure Protocol for Spontaneous Wireless Ad Hoc Networks Creation

    Page(s): 629 - 641
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2324 KB) |  | HTML iconHTML  

    This paper presents a secure protocol for spontaneous wireless ad hoc networks which uses an hybrid symmetric/asymmetric scheme and the trust between users in order to exchange the initial data and to exchange the secret keys that will be used to encrypt the data. Trust is based on the first visual contact between users. Our proposal is a complete self-configured secure protocol that is able to create the network and share secure services without any infrastructure. The network allows sharing resources and offering new services among users in a secure environment. The protocol includes all functions needed to operate without any external support. We have designed and developed it in devices with limited resources. Network creation stages are detailed and the communication, protocol messages, and network management are explained. Our proposal has been implemented in order to test the protocol procedure and performance. Finally, we compare the protocol with other spontaneous ad hoc network protocols in order to highlight its features and we provide a security analysis of the system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Bayesian-Inference-Based Recommendation in Online Social Networks

    Page(s): 642 - 651
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (807 KB) |  | HTML iconHTML  

    In this paper, we propose a Bayesian-inference-based recommendation system for online social networks. In our system, users share their content ratings with friends. The rating similarity between a pair of friends is measured by a set of conditional probabilities derived from their mutual rating history. A user propagates a content rating query along the social network to his direct and indirect friends. Based on the query responses, a Bayesian network is constructed to infer the rating of the querying user. We develop distributed protocols that can be easily implemented in online social networks. We further propose to use Prior distribution to cope with cold start and rating sparseness. The proposed algorithm is evaluated using two different online rating data sets of real users. We show that the proposed Bayesian-inference-based recommendation is better than the existing trust-based recommendations and is comparable to Collaborative Filtering (CF) recommendation. It allows the flexible tradeoffs between recommendation quality and recommendation quantity. We further show that informative Prior distribution is indeed helpful to overcome cold start and rating sparseness. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • CDS-Based Virtual Backbone Construction with Guaranteed Routing Cost in Wireless Sensor Networks

    Page(s): 652 - 661
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1374 KB) |  | HTML iconHTML  

    Inspired by the backbone concept in wired networks, virtual backbone is expected to bring substantial benefits to routing in wireless sensor networks (WSNs). Virtual backbone construction based on Connected Dominating Set (CDS) is a competitive approach among the existing methods used to establish virtual backbone in WSNs. Traditionally, CDS size was the only factor considered in the CDS-based approach. The motivation was that smaller CDS leads to simplified network maintenance. However, routing cost in terms of routing path length is also an important factor for virtual backbone construction. In our research, both of these two factors are taken into account. Specifically, we attempt to devise a polynomial-time constant-approximation algorithm that leads to a CDS with bounded CDS size and guaranteed routing cost. We prove that, under general graph model, there is no polynomial-time constant-approximation algorithm unless P = NP. Under Unit Disk Graph (UDG) model, we propose an innovative polynomial-time constant-approximation algorithm, GOC-MCDS-C, that produces a CDS D whose size I D is within a constant factor from that of the minimum CDS. In addition, for each node pair u and v, there exists a routing path with all intermediate nodes in D and path length at most 7 · d(u, v), where d(u, v) is the length of the shortest path between u and v. Our theoretical analysis and simulation results show that the distributed version of the proposed algorithm, GOC-MCDS-D, outperforms the existing approaches. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characterization and Management of Popular Content in KAD

    Page(s): 662 - 671
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (901 KB) |  | HTML iconHTML  

    The endeavor of this work is to study the impact of content popularity in a large-scale Peer-to-Peer network, namely KAD. Based on an extensive measurement campaign, we pinpoint several deficiencies of KAD in handling popular content and provide a series of improvements to address such shortcomings. Our work reveals that keywords, which are associated with content, may become popular for two distinct reasons. First, we show that some keywords are intrinsically popular because they are common to many disparate contents: in such case we ameliorate KAD by introducing a simple mechanism that identifies stopwords. Then, we focus on keyword popularity that directly relates to popular content. We design and evaluate an adaptive load balancing mechanism that is backward compatible with the original implementation of KAD. Our scheme features the following properties: 1) it drives the process that selects the location of peers responsible to store references to objects, based on object popularity; 2) it solves problems related to saturated peers that would otherwise inflict a significant drop in the diversity of references to objects, and 3) if coupled with a load-aware content search procedure, it allows for a more fair and efficient usage of peer resources. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Complete EAP Method: User Efficient and Forward Secure Authentication Protocol for IEEE 802.11 Wireless LANs

    Page(s): 672 - 680
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1250 KB) |  | HTML iconHTML  

    It is necessary to authenticate users who attempt to access resources in Wireless Local Area Networks (WLANs). Extensible Authentication Protocol (EAP) is an authentication framework widely used in WLANs. Authentication mechanisms built on EAP are called EAP methods. The requirements for EAP methods in WLAN authentication have been defined in RFC 4017. To achieve user efficiency and robust security, lightweight computation and forward secrecy, excluded in RFC 4017, are desired in WLAN authentication. However, all EAP methods and authentication protocols designed for WLANs so far do not satisfy all of the above properties. This manuscript will present a complete EAP method that utilizes stored secrets and passwords to verify users so that it can 1) fully meet the requirements of RFC 4017, 2) provide for lightweight computation, and 3) allow for forward secrecy. In addition, we also demonstrate the security of our proposed EAP method with formal proofs. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Coordinated Self-Configuration of Virtual Machines and Appliances Using a Model-Free Learning Approach

    Page(s): 681 - 690
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1831 KB) |  | HTML iconHTML  

    Cloud computing has a key requirement for resource configuration in a real-time manner. In such virtualized environments, both virtual machines (VMs) and hosted applications need to be configured on-the-fly to adapt to system dynamics. The interplay between the layers of VMs and applications further complicates the problem of cloud configuration. Independent tuning of each aspect may not lead to optimal system wide performance. In this paper, we propose a framework, namely CoTuner, for coordinated configuration of VMs and resident applications. At the heart of the framework is a model-free hybrid reinforcement learning (RL) approach, which combines the advantages of Simplex method and RL method and is further enhanced by the use of system knowledge guided exploration policies. Experimental results on Xen-based virtualized environments with TPC-W and TPC-C benchmarks demonstrate that CoTuner is able to drive a virtual server cluster into an optimal or near-optimal configuration state on the fly, in response to the change of workload. It improves the systems throughput by more than 30 percent over independent tuning strategies. In comparison with the coordinated tuning strategies based on basic RL or Simplex algorithm, the hybrid RL algorithm gains 25 to 40 percent throughput improvement. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Exploiting Concurrency for Efficient Dissemination in Wireless Sensor Networks

    Page(s): 691 - 700
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1044 KB) |  | HTML iconHTML  

    Wireless sensor networks (WSNs) can be successfully applied in a wide range of applications. Efficient data dissemination is a fundamental service which enables many useful high-level functions such as parameter reconfiguration, network reprogramming, etc. Many current data dissemination protocols employ network coding techniques to deal with packet losses. The coding overhead, however, becomes a bottleneck in terms of dissemination delay. We exploit the concurrency potential of sensor nodes and propose MT-Deluge, a multithreaded design of a coding-based data dissemination protocol. By separating the coding and radio operations into two threads and carefully scheduling their executions, MT-Deluge shortens the dissemination delay effectively. An incremental decoding algorithm is employed to further improve MT-Deluge's performance. Experiments with 24 TelosB motes on four representative topologies show that MT-Deluge shortens the dissemination delay by 25.5-48.6 percent compared to a typical data dissemination protocol while keeping the merits of loss resilience. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fault Tolerance in Distributed Systems Using Fused Data Structures

    Page(s): 701 - 715
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1659 KB) |  | HTML iconHTML  

    Replication is the prevalent solution to tolerate faults in large data structures hosted on distributed servers. To tolerate f crash faults (dead/unresponsive data structures) among n distinct data structures, replication requires f + 1 replicas of each data structure, resulting in nf additional backups. We present a solution, referred to as fusion that uses a combination of erasure codes and selective replication to tolerate f crash faults using just f additional fused backups. We show that our solution achieves O(n) savings in space over replication. Further, we present a solution to tolerate f Byzantine faults (malicious data structures), that requires only nf + f backups as compared to the 2nf backups required by replication. We explore the theory of fused backups and provide a library of such backups for all the data structures in the Java Collection Framework. The theoretical and experimental evaluation confirms that the fused backups are space-efficient as compared to replication, while they cause very little overhead for normal operation. To illustrate the practical usefulness of fusion, we use fused backups for reliability in Amazon's highly available key-value store, Dynamo. While the current replication-based solution uses 300 backup structures, we present a solution that only requires 120 backup structures. This results in savings in space as well as other resources such as power. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Feasibility of Polynomial-Time Randomized Gathering for Oblivious Mobile Robots

    Page(s): 716 - 723
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (498 KB) |  | HTML iconHTML  

    We consider the problem of gathering n anonymous and oblivious mobile robots, which requires that all robots meet in finite time at a nonpredefined point. While the gathering problem cannot be solved deterministically without assuming any additional capabilities for the robots, randomized approaches easily allow it to be solvable. However, the randomized solutions currently known have a time complexity that is exponential in n with no additional assumption. This fact yields the following two questions: Is it possible to construct a randomized gathering algorithm with polynomial expected time? If it is not possible, what is the minimal additional assumption necessary to obtain such an algorithm? In this paper, we address these questions from the aspect of multiplicity-detection capabilities. We newly introduce two weaker variants of multiplicity detection, called local-strong and local-weak multiplicity, and investigate whether those capabilities permit a gathering algorithm with polynomial expected time or not. The contribution of this paper is to show that any algorithm only assuming local-weak multiplicity detection takes exponential number of rounds in expectation. On the other hand, we can obtain a constant-round gathering algorithm using local-strong multiplicity detection. These results imply that the two models of multiplicity detection are significantly different in terms of their computational power. Interestingly, these differences disappear if we take one more assumption that all robots are scattered (i.e., no two robots stay at the same location) initially. We can obtain a gathering algorithm that takes a constant number of rounds in expectation, assuming local-weak multiplicity detection and scattered initial configurations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Finding All Maximal Contiguous Subsequences of a Sequence of Numbers in O(1) Communication Rounds

    Page(s): 724 - 733
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (575 KB) |  | HTML iconHTML  

    Given a sequence A of real numbers, we wish to find a list of all nonoverlapping contiguous subsequences of A that are maximal. A maximal subsequence M of A has the property that no proper subsequence of M has a greater sum of values. Furthermore, M may not be contained properly within any subsequence of A with this property. This problem has several applications in Computational Biology and can be solved sequentially in linear time. We present a BSP/CGM algorithm that solves this problem using p processors in O(|A|=p) time and O(|A|=p) space per processor. The algorithm uses a constant number of communication rounds of size at most O(|A|=p). Thus, the algorithm achieves linear speedup and is highly scalable. To our knowledge, there are no previous known parallel BSP/CGM algorithms to solve this problem. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Geocommunity-Based Broadcasting for Data Dissemination in Mobile Social Networks

    Page(s): 734 - 743
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1283 KB) |  | HTML iconHTML  

    In this paper, we consider the issue of data broadcasting in mobile social networks (MSNets). The objective is to broadcast data from a superuser to other users in the network. There are two main challenges under this paradigm, namely 1) how to represent and characterize user mobility in realistic MSNets; 2) given the knowledge of regular users' movements, how to design an efficient superuser route to broadcast data actively. We first explore several realistic data sets to reveal both geographic and social regularities of human mobility, and further propose the concepts of geocommunity and geocentrality into MSNet analysis. Then, we employ a semi-Markov process to model user mobility based on the geocommunity structure of the network. Correspondingly, the geocentrality indicating the “dynamic user density” of each geocommunity can be derived from the semi-Markov model. Finally, considering the geocentrality information, we provide different route algorithms to cater to the superuser that wants to either minimize total duration or maximize dissemination ratio. To the best of our knowledge, this work is the first to study data broadcasting in a realistic MSNet setting. Extensive trace-driven simulations show that our approach consistently outperforms other existing superuser route design algorithms in terms of dissemination ratio and energy efficiency. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • LOBOT: Low-Cost, Self-Contained Localization of Small-Sized Ground Robotic Vehicles

    Page(s): 744 - 753
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1139 KB) |  | HTML iconHTML  

    It is often important to obtain the real-time location of a small-sized ground robotic vehicle when it performs autonomous tasks either indoors or outdoors. We propose and implement LOBOT, a low-cost, self-contained localization system for small-sized ground robotic vehicles. LOBOT provides accurate real-time, 3D positions in both indoor and outdoor environments. Unlike other localization schemes, LOBOT does not require external reference facilities, expensive hardware, careful tuning or strict calibration, and is capable of operating under various indoor and outdoor environments. LOBOT identifies the local relative movement through a set of integrated inexpensive sensors and well corrects the localization drift by infrequent GPS-augmentation. Our empirical experiments in various temporal and spatial scales show that LOBOT keeps the positioning error well under an accepted threshold. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Lower Bound for Node Buffer Size in Intermittently Connected Wireless Networks

    Page(s): 754 - 766
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1836 KB) |  | HTML iconHTML  

    We study the fundamental lower bound for node buffer size in intermittently connected wireless networks. The intermittent connectivity is caused by the possibility of node inactivity due to some external constraints. We find even with infinite channel capacity and node processing speed, buffer occupation in each node does not approach zero in a static random network where each node keeps a constant message generation rate. Given the condition that each node has the same probability p of being inactive during each time slot, there exists a critical value pc(λ) for this probability from a percolation-based perspective. When p <; pc(λ), the network is in the supercritical case, and there is an achievable lower bound (In our paper, “achievable” means that node buffer size in networks can achieve the same order as the lower bound by applying some transmission scheme) for the occupied buffer size of each node, which is asymptotically independent of the size of the network. If p > pc(λ), the network is in the subcritical case, and there is a tight lower bound Θ(√n) for buffer occupation, where n is the number of nodes in the network. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On-Chip Sensor Network for Efficient Management of Power Gating-Induced Power/Ground Noise in Multiprocessor System on Chip

    Page(s): 767 - 777
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1043 KB) |  | HTML iconHTML  

    Reducing feature sizes and power supply voltage allows integrating more processing units (PUs) on multiprocessor system on chip (MPSoC) to satisfy the increasing demands of applications. However, it also makes MPSoC more susceptible to various reliability threats, such as high temperature and power/ground (P/G) noise. As the scale and complexity of MPSoC continuously increase, monitoring and mitigating reliability threats at runtime could offer better performance, scalability, and flexibility for MPSoC designs. In this paper, we propose a systematic approach, on-chip sensor network (SENoC), to collaboratively predict, detect, report, and alleviate runtime threats in MPSoC. SENoC not only detects reliability threats and shares related information among PUs, but also plans and coordinates the reactions of related PUs in MPSoC. SENoC is used to alleviate the impacts of simultaneous switching noise in MPSoC's P/G network during power gating. Based on the detailed noise behaviors under different scenarios derived by our circuit-level MPSoC P/G noise simulation and analysis platform, simulation results show that SENoC helps to achieve on average 26.2 percent performance improvement compared with the traditional stop-go method with 1.4 percent area overhead in an 8*8-core MPSoC in 45 nm. An architecture-level cycle-accurate simulator based on SystemC is implemented to study the performance of the proposed SENoC. By applying sophisticated scheduling techniques to optimize the total system performance, a higher performance improvement of 43.5 percent is achieved for a set of real-life applications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Robust Tracking of Small-Scale Mobile Primary User in Cognitive Radio Networks

    Page(s): 778 - 788
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1187 KB) |  | HTML iconHTML  

    In cognitive radio networks (CRNs), secondary users must be able to accurately and reliably track the location of small-scale mobile primary users/devices (e.g., wireless microphones) in order to efficiently utilize spatial spectrum opportunities, while protecting primary communications. However, accurate tracking of the location of mobile primary users is difficult due mainly to the CR-unique constraint, i.e., localization must rely solely on reported sensing results (i.e., measured primary signal strengths), which can easily be compromised by malicious sensors (or attackers). To cope with this challenge, we propose a new framework, called Sequential mOnte carLo combIned with shadow-faDing estimation (SOLID), for accurate, attack/fault-tolerant tracking of small-scale mobile primary users. The key idea underlying SOLID is to exploit the temporal shadow fading correlation in sensing results induced by the primary user's mobility. Specifically, SOLID augments conventional Sequential Monte Carlo (SMC)-based target tracking with shadow-fading estimation. By examining the shadow-fading gain between the primary transmitter and CRs/sensors, SOLID 1) significantly improves the accuracy of primary tracking regardless of the presence/absence of attack, and 2) successfully masks the abnormal sensing reports due to sensor faults or attacks, preserving localization accuracy and improving spatial spectrum efficiency. Our extensive evaluation in realistic wireless fading environments shows that SOLID lowers localization error by up to 88 percent in the absence of attacks, and 89 percent in the presence of the challenging "slow-poisoning” attack, compared to the conventional SMC-based tracking. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Scheduling Sensor Data Collection with Dynamic Traffic Patterns

    Page(s): 789 - 802
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2099 KB) |  | HTML iconHTML  

    The network traffic pattern of continuous sensor data collection often changes constantly over time due to the exploitation of temporal and spatial data correlations as well as the nature of condition-based monitoring applications. In contrast to most existing TDMA schedules designed for a static network traffic pattern, this paper proposes a novel TDMA schedule that is capable of efficiently collecting sensor data for any network traffic pattern and is thus well suited to continuous data collection with dynamic traffic patterns. In the proposed schedule, the energy consumed by sensor nodes for any traffic pattern is very close to the minimum required by their workloads given in the traffic pattern. The schedule also allows the base station to conclude data collection as early as possible according to the traffic load, thereby reducing the latency of data collection. We present a distributed algorithm for constructing the proposed schedule. We develop a mathematical model to analyze the performance of the proposed schedule. We also conduct simulation experiments to evaluate the performance of different schedules using real-world data traces. Both the analytical and simulation results show that, compared with existing schedules that are targeted on a fixed traffic pattern, our proposed schedule significantly improves the energy efficiency and time efficiency of sensor data collection with dynamic traffic patterns. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Secure SOurce-BAsed Loose Synchronization (SOBAS) for Wireless Sensor Networks

    Page(s): 803 - 813
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1694 KB) |  | HTML iconHTML  

    We present the Secure SOurce-BAsed Loose Synchronization (SOBAS) protocol to securely synchronize the events in the network, without the transmission of explicit synchronization control messages. In SOBAS, nodes use their local time values as a one-time dynamic key to encrypt each message. In this way, SOBAS provides an effective dynamic en-route filtering mechanism, where the malicious data is filtered from the network. With SOBAS, we are able to achieve our main goal of synchronizing events at the sink as quickly, as accurately, and as surreptitiously as possible. With loose synchronization, SOBAS reduces the number of control messages needed for a WSN to operate providing the key benefits of reduced energy consumption as well as reducing the opportunity for malicious nodes to eavesdrop, intercept, or be made aware of the presence of the network. Albeit a loose synchronization per se, SOBAS is also able to provide 7.24 μs clock precision given today's sensor technology, which is much better than other comparable schemes (schemes that do not employ GPS devices). Also, we show that by recognizing the need for and employing loose time synchronization, necessary synchronization can be provided to the WSN application using half of the energy needed for traditional schemes. Both analytical and simulation results are presented to verify the feasibility of SOBAS as well as the energy consumption of the scheme under normal operation and attack from malicious nodes. View full abstract»

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

    Page(s): 814 - 824
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1243 KB) |  | HTML iconHTML  

    We present Speculative Authorization (SPAN), a prediction technique that reduces authorization latency in enterprise systems. SPAN predicts requests that a system client might make in the near future, based on its past behavior. SPAN allows authorization decisions for the predicted requests to be made before the requests are issued, thus virtually reducing the authorization latency to zero. We developed SPAN algorithms, implemented a prototype, and evaluated it using two real-world data traces and one synthetic data trace. The results of our evaluation suggest that systems employing SPAN are able to achieve a reduced authorization latency for almost 60 percent of the requests. We analyze the tradeoffs between the hit rate and the precision of SPAN predictions, which directly affect the corresponding computational overhead. We also compare the benefits of deploying both caching and SPAN together, and find that SPAN can effectively improve the performance of those systems which have caches of a smaller size. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On Data Staging Algorithms for Shared Data Accesses in Clouds

    Page(s): 825 - 838
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1267 KB) |  | HTML iconHTML  

    In this paper, we study the strategies for efficiently achieving data staging and caching on a set of vantage sites in a cloud system with a minimum cost. Unlike the traditional research, we do not intend to identify the access patterns to facilitate the future requests. Instead, with such a kind of information presumably known in advance, our goal is to efficiently stage the shared data items to predetermined sites at advocated time instants to align with the patterns while minimizing the monetary costs for caching and transmitting the requested data items. To this end, we follow the cost and network models in [1] and extend the analysis to multiple data items, each with single or multiple copies. Our results show that under homogeneous cost model, when the ratio of transmission cost and caching cost is low, a single copy of each data item can efficiently serve all the user requests. While in multicopy situation, we also consider the tradeoff between the transmission cost and caching cost by controlling the upper bounds of transmissions and copies. The upper bound can be given either on per-item basis or on all-item basis. We present efficient optimal solutions based on dynamic programming techniques to all these cases provided that the upper bound is polynomially bounded by the number of service requests and the number of distinct data items. In addition to the homogeneous cost model, we also briefly discuss this problem under a heterogeneous cost model with some simple yet practical restrictions and present a 2-approximation algorithm to the general case. We validate our findings by implementing a data staging solver, whereby conducting extensive simulation studies on the behaviors of the algorithms. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • WILL: Wireless Indoor Localization without Site Survey

    Page(s): 839 - 848
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1038 KB) |  | HTML iconHTML  

    Indoor localization is of great importance for a range of pervasive applications, attracting many research efforts in the past two decades. Most radio-based solutions require a process of site survey, in which radio signatures are collected and stored for further comparison and matching. Site survey involves intensive costs on manpower and time. In this work, we study unexploited RF signal characteristics and leverage user motions to construct radio floor plan that is previously obtained by site survey. On this basis, we design WILL, an indoor localization approach based on off-the-shelf WiFi infrastructure and mobile phones. WILL is deployed in a real building covering over 1600 m2, and its deployment is easy and rapid since site survey is no longer needed. The experiment results show that WILL achieves competitive performance comparing with traditional approaches. 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