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Mobile Computing, IEEE Transactions on

Issue 6 • Date June 2010

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Displaying Results 1 - 17 of 17
  • [Front cover]

    Page(s): c1
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  • [Inside front cover]

    Page(s): c2
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  • Threshold-Based Media Streaming Optimization for Heterogeneous Wireless Networks

    Page(s): 753 - 764
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1679 KB) |  | HTML iconHTML  

    The integration of different wireless access technologies combined with the huge characteristic diversity of supported services in next-generation wireless systems creates a real heterogeneous network. In this paper, we propose a generic practical framework that optimizes media streaming in heterogeneous systems by taking advantage of cost and resource characteristic diversity of the integrated access technologies and the buffering capability of streaming applications. The proposed optimization framework represents a means to compromise the tradeoff between different performance metrics including streaming monetary cost, signaling load, and session quality. Additionally, it accommodates different design challenges including mobility randomness, limited processing capacity, and handoff delay requirements. The simulation results provide important insights on the design of pricing profiles in integrated systems. Additionally, the results show that significant cost savings can be realized using the newly proposed streaming management algorithms and optimization framework. View full abstract»

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  • Achievable Capacity in Hybrid DS-CDMA/OFDM Spectrum-Sharing

    Page(s): 765 - 777
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1575 KB) |  | HTML iconHTML  

    In this paper, we consider DS-CDMA/OFDM spectrum sharing systems and obtain the achievable capacity of the secondary service under different subchannel selection policies in the fading environment. Subchannel selection policies are divided into two categories: uniform subchannel selection, and nonuniform subchannel selection. Uniform subchannel selection is preferred for cases where a priori knowledge on subchannels state information is not available at the secondary transmitter. For cases with available a priori knowledge on subchannels state information, we study various nonuniform subchannel selection policies. In each case, we obtain the optimum secondary service power allocation and the corresponding maximum achievable capacity. Then we present results on the scaling law of the opportunistic spectrum sharing in DS-CDMA/OFDM systems with multiple users. Numerical results show that the optimal subchannel selection is based on the minimum value of the subchannel gain between the secondary transmitter and the primary receiver. View full abstract»

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  • SSUM: Smart Server Update Mechanism for Maintaining Cache Consistency in Mobile Environments

    Page(s): 778 - 795
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5966 KB) |  | HTML iconHTML  

    This paper proposes a cache consistency scheme based on a previously proposed architecture for caching database data in MANETs. The original scheme for data caching stores the queries that are submitted by requesting nodes in special nodes, called query directories (QDs), and uses these queries to locate the data (responses) that are stored in the nodes that requested them, called caching nodes (CNs). The consistency scheme is server-based in which control mechanisms are implemented to adapt the process of caching a data item and updating it by the server to its popularity and its data update rate at the server. The system implements methods to handle disconnections of QD and CN nodes from the network and to control how the cache of each node is updated or discarded when it returns to the network. Estimates for the average response time of node requests and the average node bandwidth utilization are derived in order to determine the gains (or costs) of employing our scheme in the MANET. Moreover, ns2 simulations were performed to measure several parameters, like the average data request response time, cache update delay, hit ratio, and bandwidth utilization. The results demonstrate the advantage of the proposed scheme over existing systems. View full abstract»

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  • QELAR: A Machine-Learning-Based Adaptive Routing Protocol for Energy-Efficient and Lifetime-Extended Underwater Sensor Networks

    Page(s): 796 - 809
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2250 KB) |  | HTML iconHTML  

    Underwater sensor network (UWSN) has emerged in recent years as a promising networking technique for various aquatic applications. Due to specific characteristics of UWSNs, such as high latency, low bandwidth, and high energy consumption, it is challenging to build networking protocols for UWSNs. In this paper, we focus on addressing the routing issue in UWSNs. We propose an adaptive, energy-efficient, and lifetime-aware routing protocol based on reinforcement learning, QELAR. Our protocol assumes generic MAC protocols and aims at prolonging the lifetime of networks by making residual energy of sensor nodes more evenly distributed. The residual energy of each node as well as the energy distribution among a group of nodes is factored in throughout the routing process to calculate the reward function, which aids in selecting the adequate forwarders for packets. We have performed extensive simulations of the proposed protocol on the Aqua-sim platform and compared with one existing routing protocol (VBF) in terms of packet delivery rate, energy efficiency, latency, and lifetime. The results show that QELAR yields 20 percent longer lifetime on average than VBF. View full abstract»

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  • Secure Distance-Based Localization in the Presence of Cheating Beacon Nodes

    Page(s): 810 - 823
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    Secure distance-based localization in the presence of cheating beacon (or anchor) nodes is an important problem in mobile wireless ad hoc and sensor networks. Despite significant research efforts in this direction, some fundamental questions still remain unaddressed: In the presence of cheating beacon nodes, what are the necessary and sufficient conditions to guarantee a bounded error during a two-dimensional distance-based location estimation? Under these necessary and sufficient conditions, what class of localization algorithms can provide this error bound? In this paper, we attempt to answer these and other related questions by following a careful analytical approach. Specifically, we first show that when the number of cheating beacon nodes is greater than or equal to a given threshold, there do not exist any two-dimensional distance-based localization algorithms that can guarantee a bounded error. Furthermore, when the number of cheating beacons is below this threshold, we identify a class of distance-based localization algorithms that can always guarantee a bounded localization error. Finally, we outline three novel distance-based localization algorithms that belong to this class of bounded error localization algorithms. We verify their accuracy and efficiency by means of extensive simulation experiments using both simple and practical distance estimation error models. View full abstract»

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  • Combined Authentication-Based Multilevel Access Control in Mobile Application for DailyLifeService

    Page(s): 824 - 837
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    In current computing environments, collaborative computing has been a central concern in Ubiquitous, Convergent, and Social Computing. "MobiLife?? and "MyLifeBits?? are the leading projects for representing dailylifeservices and their systems require complicate and collaborative network systems. The collaborative computing environments remain in high potential risks for users' security and privacy because of diverse attack routes. In order to solve the problems, we design combined authentication and multilevel access control, which deals with cryptographic methods in a personal database of "MyLifeBits?? system. We propose a scheme which is flexible in dynamic access authorization changes, secure against all the attacks from various routes, a minimum round of protocol, privacy preserving access control, and multifunctional. View full abstract»

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  • Maximum Achievable Throughput in Multiband Multiantenna Wireless Mesh Networks

    Page(s): 838 - 849
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    We have recently witnessed a rapidly increasing demand for, and hence, a shortage of, wireless network bandwidth due to rapidly growing wireless services and applications. It is, therefore, important to develop an efficient way of utilizing this limited bandwidth resource. Fortunately, recent technological advances have enabled software-defined radios (SDRs) to switch from one frequency band to another at minimum cost, thereby making dynamic multiband access and sharing possible. On the other hand, recent advances in signal processing combined with those in antenna technology provide multiple-input multiple-output (MIMO) capabilities, thereby creating opportunities for enhancing the throughput of wireless networks. Both SDRs and MIMO together enable next-generation wireless networks, such as mesh networks, to support dynamic and adaptive bandwidth sharing along time, frequency, and space. In this paper, we develop a new framework that 1) identifies the limits and potential of SDRs and MIMO in terms of achievable network throughput and 2) provides guidelines for designers to determine the optimal parameters of wireless mesh networks equipped with multiband and multiantenna capabilities. View full abstract»

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  • A Coverage Inference Protocol for Wireless Sensor Networks

    Page(s): 850 - 864
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1853 KB) |  | HTML iconHTML  

    After a wireless sensor network (WSN) is deployed, sensor nodes are usually left unattended for a long period of time. There is an inevitable devolution of the connected coverage of the WSN due to battery exhaustion of sensor nodes, intended physical destruction attacks on sensor nodes, unpredictable node movement by physical means like wind, and so on. It is, therefore, critical that the base station (BS) learns in real time how well the WSN performs the given sensing task (i.e., what is the current connected coverage) under a dynamically changing network topology. In this paper, we propose a coverage inference protocol (CIP), which can provide the BS an accurate and in-time measurement of the current connected coverage in an energy-efficient way. Especially, we show that the scheme called BOND, which our CIP requires to be implemented on each sensor node, enables each node to locally self-detect whether it is a boundary node with the minimal communication and computational overhead. The BOND can also be exploited to seamlessly integrate multiple functionalities with low overhead. Moreover, we devise extensions to CIP that can tolerate location errors and actively predict the change of the connected coverage based on residual energy of sensor nodes. View full abstract»

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  • Optimal Accounting Policies for AAA Systems in Mobile Telecommunications Networks

    Page(s): 865 - 880
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    Authentication, Authorization, and Accounting (AAA) deployments are expected to grow significantly in emerging mobile systems as they offer a plethora of services and mobile applications. In current systems, network access servers (NAS) periodically report the service usage of mobile users located within their coverage areas. The periodic reports are used by the billing systems to minimize the incurred capital losses if the serving NAS fails. While shorter reporting intervals are desired for lower losses, they can potentially result in undesirably high signaling load. Because it is prohibitively difficult to obtain optimal reporting intervals in mobile systems due to multitudes of services with different mobility profiles, current accounting standards offer no quantitative measures for selecting a proper reporting interval and AAA systems are typically designed via over provisioning. To address this issue, we propose an adaptive optimization mechanism in multiservice AAA systems which limits the potential loss without excessively generating unnecessary usage reports. Our optimization mechanism embraces the current AAA IETF standards RADIUS and its successor Diameter and does not require any modifications to the AAA protocols nor to the network access servers' implementation, and its implementation scope is limited to the AAA systems. The results demonstrate that our mechanism is robust under various operational conditions, easy to implement, and offers considerable potential for loss control compared to the current static approaches. View full abstract»

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  • Modeling and Optimizing IEEE 802.11 DCF for Long-Distance Links

    Page(s): 881 - 896
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3068 KB) |  | HTML iconHTML  

    Most rural areas in developing countries are isolated due to the lack of appropriate low-cost communication technologies. Previous experiences have shown that IEEE 802.11 can be used for the deployment of large static mesh networks with only minor changes to the MAC layer that enable WiFi transceivers to work properly even for very long distances (up to 100 km in point to point links, and almost 40 km in point to multipoint setups). However, the impact of distance on performance of such long links has not been deeply analyzed. In addition, previous analytical models of IEEE 802.11 DCF cannot be applied because they implicitly assume that the propagation time can be neglected. This paper formally studies the impact of the distance on the behavior of IEEE 802.11 DCF and presents an analytical model of IEEE 802.11 DCF that accounts for distances correctly. The model is validated with simulations and within a controlled experimental framework, based on wireless channel emulation. Finally, we propose adjustments for ACKTimeout, CTSTimeout, SlotTime, and CWmin parameters that improve significantly the performance of DCF over long distances. View full abstract»

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  • Accurate and Energy-Efficient Range-Free Localization for Mobile Sensor Networks

    Page(s): 897 - 910
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    Existing localization algorithms for mobile sensor networks are usually based on the Sequential Monte Carlo (SMC) method. They either suffer from low sampling efficiency or require high beacon density to achieve high localization accuracy. Although papers can be found for solving the above problems separately, there is no solution which addresses both issues. In this paper, we propose an energy efficient algorithm, called WMCL, which can achieve both high sampling efficiency and high localization accuracy in various scenarios. In existing algorithms, a technique called bounding-box is used to improve the sampling efficiency by reducing the scope from which the candidate samples are selected. WMCL can further reduce the size of a sensor node's bounding-box by a factor of up to 87 percent and, consequently, improve the sampling efficiency by a factor of up to 95 percent. The improvement in sampling efficiency dramatically reduces the computational cost. Our algorithm uses the estimated position information of sensor nodes to improve localization accuracy. Compared with algorithms adopting similar methods, WMCL can achieve similar localization accuracy with less communication cost and computational cost. Our work has additional advantages. First, most existing SMC-based localization algorithms cannot be used in static sensor networks but WMCL can work well, even without the need of experimentally tuning parameters as required in existing algorithms like MSL*. Second, existing algorithms have low localization accuracy when nodes move very fast. We propose a new algorithm in which WMCL is iteratively executed with different assumptions on nodes' speed. The new algorithm dramatically improves localization accuracy when nodes move very fast. We have evaluated the performance of our algorithm both theoretically and through extensive simulations. We have also validated the performance results of our algorithm by implementing it in real deployed static sensor networks. To - he best of our knowledge, we are the first to implement SMC-based localization algorithms for wireless sensor networks in real environment. View full abstract»

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  • The IEEE Computer Society Digital Library [advertisement]

    Page(s): 911
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  • IEEE Computer Society CSDA Certification [advertisement]

    Page(s): 912
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  • TMC Information for authors

    Page(s): c3
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  • [Back cover]

    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