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Mobile Computing, IEEE Transactions on

Issue 11 • Date Nov. 2011

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Displaying Results 1 - 19 of 19
  • [Front cover]

    Publication Year: 2011 , Page(s): c1
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  • [Inside front cover]

    Publication Year: 2011 , Page(s): c2
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  • On the Throughput of MIMO-Empowered Multihop Cognitive Radio Networks

    Publication Year: 2011 , Page(s): 1505 - 1519
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2868 KB) |  | HTML iconHTML  

    Cognitive radio (CR) and multiple-input multiple-output (MIMO) are two independent physical layer technologies that have made significant impact on wireless networking. CR operates on the channel/band level to exploit white space across spectrum dimension while MIMO operates within the same channel to improve spectral efficiency within the same band. In this paper, we explore MIMO-empowered CR network, which we call CRNMIMO, to achieve the ultimate flexibility and efficiency in dynamic spectrum access and spectrum utilization. Given that CR and MIMO handle interference at different levels (across channels vs. within a channel), we are interested in how to jointly optimize both so as to maximize user throughput in a multihop network. To answer this question, we develop a tractable mathematical model for CRNMIMO, which captures the essence of channel assignment (for CR) and degree-of-freedom (DoF) allocation (for MIMO) within a channel. Based on this mathematical model, we use numerical results to show how channel assignment in CRN and DoF allocation in MIMO can be jointly optimized to maximize throughput. More important, for a CRNMIMO with AMIMO antennas at each node, we show that joint optimization of CR and MIMO offers more than AMIMO-fold throughput increase than a CRN (without MIMO). View full abstract»

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  • Strictly Localized Sensor Self-Deployment for Optimal Focused Coverage

    Publication Year: 2011 , Page(s): 1520 - 1533
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1326 KB)  

    We consider sensor self-deployment problem, constructing FOCUSED coverage (F-coverage) around a Point of Interest (POI), with novel evaluation metric, coverage radius. We propose to deploy sensors in polygon layers over a locally computable equilateral triangle tessellation (TT) for optimal F-coverage formation, and introduce two types of deployment polygon, H-polygon and C-polygon. We propose two strictly localized solution algorithms, Greedy Advance (GA), and Greedy-Rotation-Greedy (GRG). The two algorithms drive sensors to move along the TT graph to surround POI. In GA, nodes greedily proceed as close to POI as they can; in GRG, when their greedy advance is blocked, nodes rotate around POI along locally computed H- or C-polygon to a vertex where greedy advance can resume. We prove that they both yield a connected network with maximized hole-free area coverage. To our knowledge, they are the first localized sensor self-deployment algorithms that provide such coverage guarantee. We further analyze their coverage radius property. Our study shows that GRG guarantees optimal or near optimal coverage radius. Through extensive simulation we as well evaluate their performance on convergence time, energy consumption, and node collision. View full abstract»

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  • Sweep Coverage with Mobile Sensors

    Publication Year: 2011 , Page(s): 1534 - 1545
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1105 KB) |  | HTML iconHTML  

    Many efforts have been made for addressing coverage problems in sensor networks. They fall into two categories, full coverage and barrier coverage, featured as static coverage. In this work, we study a new coverage scenario, sweep coverage, which differs with the previous static coverage. In sweep coverage, we only need to monitor certain points of interest (POIs) periodically so the coverage at each POI is time-variant, and thus we are able to utilize a small number of mobile sensors to achieve sweep coverage among a much larger number of POIs. We investigate the definitions and model for sweep coverage. Given a set of POIs and their sweep period requirements, we prove that determining the minimum number of required sensors (min-sensor sweep-coverage problem) is NP-hard, and it cannot be approximated within a factor of 2. We propose a centralized algorithm with constant approximation ratio 3 for the min-sensor sweep-coverage problem. We further characterize the nonlocality of the problem and design a distributed sweep algorithm, DSWEEP, cooperating sensors to provide efficiency with the best effort. We conduct extensive simulations to study the performance of the proposed algorithms. Our simulations show that DSWEEP outperforms the randomized scheme in both effectiveness and efficiency. View full abstract»

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  • Model and Protocol for Energy-Efficient Routing over Mobile Ad Hoc Networks

    Publication Year: 2011 , Page(s): 1546 - 1557
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1011 KB) |  | HTML iconHTML  

    Many minimum energy (energy-efficient) routing protocols have been proposed in recent years. However, very limited effort has been made in studying routing overhead, route setup time, and route maintenance issues associated with these protocols. Without a careful design, an energy-efficient routing protocol can perform much worse than a normal routing protocol. In this paper, we first show that the minimum energy routing schemes in the literature could fail without considering the routing overhead involved and node mobility. We then propose a more accurate analytical model to track the energy consumptions due to various factors, and a simple energy-efficient routing scheme PEER to improve the performance during path discovery and in mobility scenarios. Our simulation results indicate that compared to a conventional energy-efficient routing protocol, PEER protocol can reduce up to 2/3 path discovery overhead and delay, and 50 percent transmission energy consumption. View full abstract»

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  • Optimal Resource Allocation for Pervasive Health Monitoring Systems with Body Sensor Networks

    Publication Year: 2011 , Page(s): 1558 - 1575
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1916 KB) |  | HTML iconHTML  

    Pervasive health monitoring is an eHealth service, which plays an important role in prevention and early detection of diseases. There are two major challenges in pervasive health monitoring systems with Body Sensor Networks (BSNs). The first challenge is the sustainable power supply for BSNs. The second challenge is Quality of Service (QoS) guarantee for the delivery of data streams. In this paper, we optimize the resource allocations to provide a sustainable and high-quality service in health monitoring systems. Specifically, we formulate and solve two resource optimization problems, respectively. In the first optimization problem, steady-rate optimization problem, we optimize the source rate at each sensor to minimize the rate fluctuation with respect to the average sustainable rate, subject to the requirement of uninterrupted service. The first optimization problem is solved by a proposed analytical solution. The second optimization problem is formulated based on the optimal source rates of the sensors obtained in the steady-rate optimization problem. In the second optimization problem, we jointly optimize the transmission power and the transmission rate at each aggregator to provide QoS guarantee to data delivery. The second optimization problem is converted into a convex optimization problem, which is then solved efficiently. In the simulations, we demonstrate that the proposed optimized scheme enables the pervasive health monitoring system to provide a sustainable service with guaranteed low delay and low Packet Loss Rate (PLR) to subscribers. View full abstract»

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  • BUBBLE Rap: Social-Based Forwarding in Delay-Tolerant Networks

    Publication Year: 2011 , Page(s): 1576 - 1589
    Cited by:  Papers (243)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1780 KB) |  | HTML iconHTML  

    The increasing penetration of smart devices with networking capability form novel networks. Such networks, also referred as pocket switched networks (PSNs), are intermittently connected and represent a paradigm shift of forwarding data in an ad hoc manner. The social structure and interaction of users of such devices dictate the performance of routing protocols in PSNs. To that end, social information is an essential metric for designing forwarding algorithms for such types of networks. Previous methods relied on building and updating routing tables to cope with dynamic network conditions. On the downside, it has been shown that such approaches end up being cost ineffective due to the partial capture of the transient network behavior. A more promising approach would be to capture the intrinsic characteristics of such networks and utilize them in the design of routing algorithms. In this paper, we exploit two social and structural metrics, namely centrality and community, using real human mobility traces. The contributions of this paper are two-fold. First, we design and evaluate BUBBLE, a novel social-based forwarding algorithm, that utilizes the aforementioned metrics to enhance delivery performance. Second, we empirically show that BUBBLE can substantially improve forwarding performance compared to a number of previously proposed algorithms including the benchmarking history-based PROPHET algorithm, and social-based forwarding SimBet algorithm. View full abstract»

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  • Investment and Pricing with Spectrum Uncertainty: A Cognitive Operator's Perspective

    Publication Year: 2011 , Page(s): 1590 - 1604
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1496 KB) |  | HTML iconHTML  

    This paper studies the optimal investment and pricing decisions of a cognitive mobile virtual network operator (C-MVNO) under spectrum supply uncertainty. Compared with a traditional MVNO who often leases spectrum via long-term contracts, a C-MVNO can acquire spectrum dynamically in short-term by both sensing the empty “spectrum holes” of licensed bands and dynamically leasing from the spectrum owner. As a result, a C-MVNO can make flexible investment and pricing decisions to match demands of the secondary unlicensed users. Compared to dynamic spectrum leasing, spectrum sensing is typically cheaper, but the obtained useful spectrum amount is random due to primary licensed users' stochastic traffic. The C-MVNO needs to determine the optimal amounts of spectrum sensing and leasing by evaluating the trade-off between cost and uncertainty. The C-MVNO also needs to determine the optimal price to sell the spectrum to the secondary unlicensed users, taking into account wireless heterogeneity of users such as different maximum transmission power levels and channel gains. We model and analyze the interactions between the C-MVNO and secondary unlicensed users as a Stackelberg game. We show several interesting properties of the network equilibrium, including threshold structures of the optimal investment and pricing decisions, the independence of the optimal price on users' wireless characteristics, and guaranteed fair and predictable QoS among users. We prove that these properties hold for general SNR regime and general continuous distributions of sensing uncertainty. We show that spectrum sensing can significantly improve the C-MVNO's expected profit and users' payoffs. View full abstract»

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  • Feedback-Based Closed-Loop Carrier Synchronization: A Sharp Asymptotic Bound, an Asymptotically Optimal Approach, Simulations, and Experiments

    Publication Year: 2011 , Page(s): 1605 - 1617
    Cited by:  Papers (3)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2487 KB) |  | HTML iconHTML  

    We derive an asymptotically sharp bound on the synchronization speed of a randomized black box optimization technique for closed-loop feedback-based distributed adaptive beamforming in wireless sensor networks. We also show that the feedback function that guides this synchronization process is strong multimodal. Given this knowledge that no local optimum exists, we consider an approach to locally compute the phase offset of each individual carrier signal. With this design objective, an asymptotically optimal algorithm is derived. Additionally, we discuss the concept to reduce the optimization time and energy consumption by hierarchically clustering the network into subsets of nodes that achieve beamforming successively over all clusters. For the approaches discussed, we demonstrate their practical feasibility in simulations and experiments. View full abstract»

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  • Recognizing Multiuser Activities Using Wireless Body Sensor Networks

    Publication Year: 2011 , Page(s): 1618 - 1631
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2605 KB) |  | HTML iconHTML  

    The advances of wireless networking and sensor technology open up an interesting opportunity to infer human activities in a smart home environment. Existing work in this paradigm focuses mainly on recognizing activities of single user. In this work, we focus on the fundamental problem of recognizing activities of multiple users using a wireless body sensor network, and propose a scalable pattern mining approach to recognize both single- and multiuser activities in a unified framework. We exploit Emerging Pattern-a discriminative knowledge pattern which describes significant changes among activity classes of data-for building activity models and design a scalable, noise-resistant, Emerging Pattern-based Multiuser Activity Recognizer (epMAR) to recognize both single- and multiuser activities. We develop a multimodal, wireless body sensor network for collecting real-world traces in a smart home environment, and conduct comprehensive empirical studies to evaluate our system. Results show that epMAR outperforms existing schemes in terms of accuracy, scalability, and robustness. View full abstract»

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  • Gossip-Enabled Stochastic Channel Negotiation for Cognitive Radio Ad Hoc Networks

    Publication Year: 2011 , Page(s): 1632 - 1645
    Cited by:  Papers (2)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1297 KB) |  | HTML iconHTML  

    The presence of a predefined control channel in ad hoc wireless networks is a common assumption widely accepted by the research community. However, it may not always be the case in some future networking scenarios with high-network dynamics and strong user diversity, such as cognitive radio (CR) ad hoc networks. This paper investigates channel negotiation in CR ad hoc networks without a predefined control channel by introducing a novel gossip-enabled stochastic channel negotiation (GES-CN) framework. The channel negotiation process is first formulated as an optimization problem, aiming to improve the probability of successful channel negotiation in the CR network while achieving sufficient suppression on the interferences to the primary networks. With the GES-CN framework, we develop an analytical model on the probability of successful channel negotiation as well as the resultant overhead in terms of the number of channel negotiation attempts made before achieving a successful channel negotiation process via an absorbing Markov chain. Numerical results demonstrate the merits of the proposed GES-CN framework and validate the developed analytical model. We conclude that the proposed GES-CN framework is an excellent candidate for the future distributed CR ad hoc networks with high dynamics and heterogeneity. View full abstract»

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  • Photo Retrieval Based on Spatial Layout with Hardware Acceleration for Mobile Devices

    Publication Year: 2011 , Page(s): 1646 - 1660
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3719 KB) |  | HTML iconHTML  

    A new photo retrieval system for mobile devices is proposed. The system can be used to search for photos with similar spatial layouts efficiently, and it adopts an image segmentation algorithm that extracts features of image regions based on K-Means clustering. Since K-Means is computationally intensive for real-time applications and prone to generate clustering results with local optima, parallel hardware architectures are designed to meet the real-time requirement of the retrieval process. Experiments show that the proposed algorithm in the photo retrieval system obtains better mean average precision than other methods, and it is tested with image recognition problems. The robustness of the algorithm is also evaluated with noise and image blurring. Besides, the proposed K-Means hardware can provide a trade-off between the execution time and the retrieval performance on the software and hardware cosimulation platform. The contribution of this work is twofold. The first is the development of a photo retrieval framework for mobile devices, where a new texture feature is employed in the algorithm to enhance the retrieval performance. The other is the integration of the K-Means hardware accelerator and the photo retrieval system. The hardware architecture is analyzed, and the specifications are compared with previous works. View full abstract»

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  • IEEE Computer Society OnlinePlus Coming Soon to TMC

    Publication Year: 2011 , Page(s): 1661
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  • Transactions on Computers EssentialSets Available

    Publication Year: 2011 , Page(s): 1662
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  • CPS Handles the Details for you [advertisement]

    Publication Year: 2011 , Page(s): 1663
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  • Distinguish yourself with the CSDP [advertisement]

    Publication Year: 2011 , Page(s): 1664
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  • TMC Information for authors

    Publication Year: 2011 , Page(s): c3
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  • [Back cover]

    Publication Year: 2011 , Page(s): c4
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Aims & Scope

Mobile Computing, as proposed in this Transactions, focuses on the key technical issues related to (a) architectures, (b) support services, (c) algorithm/protocol design and analysis, (d) mobile environments, (e) mobile communication systems, (f) applications, and (g) emerging technologies.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Prasant Mohapatra
Interim Vice-Provost and CIO
Professor, Dept. Computer Science
University of California, Davis, USA
pmohapatra@ucdavis.edu