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Mobile Computing, IEEE Transactions on

Issue 11 • Date Nov. 2009

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Displaying Results 1 - 14 of 14
  • [Front cover]

    Page(s): c1
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    Freely Available from IEEE
  • [Inside front cover]

    Page(s): c2
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    Freely Available from IEEE
  • A Maximum-Residual Multicast Protocol for Large-Scale Mobile Ad Hoc Networks

    Page(s): 1441 - 1453
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1991 KB) |  | HTML iconHTML  

    Routing problems have become highly challenging because of the popularity of mobile devices. This paper targets power-aware routing when network topologies and data traffic may change quickly in an unpredictable way. We propose a distributed algorithm and its realization to maximize the minimum residual energy of all the nodes for each multicast, where no global information is assumed to be efficiently maintained at any node. A transient multicast tree is established on demand and derived based on the autonomous decisions of intermediate nodes. We prove that the derived tree is loop-free and theoretically optimal in the maximization of minimum residual energy. The performance of the proposed protocol was evaluated over NS2 with a series of simulations for which we have very encouraging results. View full abstract»

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  • Multiradio Channel Allocation in Multihop Wireless Networks

    Page(s): 1454 - 1468
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1886 KB) |  | HTML iconHTML  

    Channel allocation was extensively investigated in the framework of cellular networks, but it was rarely studied in the wireless ad hoc networks, especially in the multihop networks. In this paper, we study the competitive multiradio multichannel allocation problem in multihop wireless networks in detail. We first analyze that the static noncooperative game and Nash equilibrium (NE) channel allocation scheme are not suitable for the multihop wireless networks. Thus, we model the channel allocation problem as a hybrid game involving both cooperative game and noncooperative game. Within a communication session, it is cooperative; and among sessions, it is noncooperative. We propose the min-max coalition-proof Nash equilibrium (MMCPNE) channel allocation scheme in the game, which aims to maximize the achieved data rates of communication sessions. We analyze the existence of MMCPNE and prove the necessary conditions for MMCPNE. Furthermore, we propose several algorithms that enable the selfish players to converge to MMCPNE. Simulation results show that MMCPNE outperforms NE and coalition-proof Nash equilibrium (CPNE) schemes in terms of the achieved data rates of multihop sessions and the throughput of whole networks due to cooperation gain. View full abstract»

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  • Fuzzy Q-Learning Admission Control for WCDMA/WLAN Heterogeneous Networks with Multimedia Traffic

    Page(s): 1469 - 1479
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2041 KB) |  | HTML iconHTML  

    In this paper, admission control by a fuzzy Q-learning technique is proposed for WCDMA/WLAN heterogeneous networks with multimedia traffic. The fuzzy Q-learning admission control (FQAC) system is composed of a neural-fuzzy inference system (NFIS) admissibility estimator, an NFIS dwelling estimator, and a decision maker. The NFIS admissibility estimator takes essential system measures into account to judge how each reachable subnetwork can support the admission request's required QoS and then output admissibility costs. The NFIS dwelling estimator considers the Doppler shift and the power strength of the requested user to assess his/her dwell time duration in each reachable subnetwork and then output dwelling costs. Also, in order to minimize the expected maximal cost of the user's admission request, a minimax theorem is applied in the decision maker to determine the most suitable subnetwork for the user request or to reject. Simulation results show that FQAC can always maintain the system QoS requirement up to traffic intensity of 1.1 because it can appropriately admit or reject the users' admission requests. Also, the FQAC can achieve lower blocking probabilities than conventional JSAC proposed in and can significantly reduce the handoff rate by 15-20 percent. View full abstract»

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  • Throughput Behavior in Multihop Multiantenna Wireless Networks

    Page(s): 1480 - 1494
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3464 KB) |  | HTML iconHTML  

    Multiantenna or MIMO systems offer great potential for increasing the throughput of multihop wireless networks via spatial reuse and/or spatial multiplexing. This paper characterizes and analyzes the maximum achievable throughput in multihop, MIMO-equipped, wireless networks under three MIMO protocols, spatial reuse only (SRP), spatial multiplexing only (SMP), and spatial reuse and multiplexing (SRMP), each of which enhances the throughput, but via a different way of exploiting MIMO's capabilities. We show via extensive simulation that as the number of antennas increases, the maximum achievable throughput first rises and then flattens out asymptotically under SRP, while it increases "almost" linearly under SMP or SRMP. We also evaluate the effects of several network parameters on this achievable throughput, and show how throughput behaves under these effects. View full abstract»

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  • A Real-Time Intelligent Wireless Mobile Station Location Estimator with Application to TETRA Network

    Page(s): 1495 - 1509
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3624 KB) |  | HTML iconHTML  

    Mobile location estimation has received considerable interest over the past few years due to its great potential in different applications such as logistics, patrol, and fleet management. Many mobile location estimation techniques had been proposed to improve the accuracy of location estimation. Location estimation based on artificial intelligence techniques is a recent alternative approach. In this paper, adaptive neuro-fuzzy inference system (ANFIS) is used as a robust location estimator to locate the mobile station (MS) using the MS geo-fencing area data within 9 km from a serving base station. Extensive evaluations and comparisons have been performed, and a set of statistical parameters has been obtained. From the comparison of the proposed ANFIS estimator with the neural-network-based estimators, it is found that ANFIS estimator is faster and more robust. Its average computation time (ACT) is 0.076 sec. While the ACT for multilayer perceptron (MLP) and radial-based function (RBF) neural networks is 0.88 and 1.7, respectively. Whereas on comparing ANFIS with other techniques, it is found that in ANFIS estimator, 67 percent of the estimated location errors do not exceed 149 m, while these for the statistical, multiple linear regression, and geometric are 170, 280, and 2,346 m, respectively. Thus, the results clearly reveal that the proposed ANFIS estimator outperforms all other techniques. View full abstract»

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  • Minimum Latency Broadcasting in Multiradio, Multichannel, Multirate Wireless Meshes

    Page(s): 1510 - 1523
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2647 KB) |  | HTML iconHTML  

    This paper addresses the problem of "efficientrdquo broadcast in a multiradio, multichannel, multirate wireless mesh network (MR2-MC WMN). In such an MR2-MC WMN, nodes are equipped with multiple radio interfaces, tuned to orthogonal channels, that can dynamically adjust their transmission rate by choosing a modulation scheme appropriate for the channel conditions. We choose "broadcast latency,rdquo defined as the maximum delay between a packet's network-wide broadcast at the source and its eventual reception at all network nodes, as the ldquoefficiencyrdquo metric of broadcast performance. We study in this paper how the availability of multirate transmission capability and multiple radio interfaces tuned to orthogonal channels in MR2-MC WMN nodes can be exploited, in addition to the medium's ldquowireless broadcast advantagerdquo (WBA), to improve the ldquobroadcast latencyrdquo performance. In this paper, we present four heuristic solutions to our considered problem. We present detailed simulation results for these algorithms for an idealized scheduler, as well as for a practical 802.11-based scheduler. We also study the effect of channel assignment on broadcast performance and show that channel assignment can affect the broadcast performance substantially. More importantly, we show that a channel assignment that performs well for unicast does not necessarily perform well for broadcast/multicast. View full abstract»

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  • Optimal Selective Transmission under Energy Constraints in Sensor Networks

    Page(s): 1524 - 1538
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2089 KB) |  | HTML iconHTML  

    An optimum selective transmission scheme for energy-limited sensor networks, where sensors send or forward messages of different importance (priority), is developed. Considering the energy costs, the available battery, the message importances and their statistical distribution, sensors decide whether to transmit or discard a message so that the importance sum of the effectively transmitted messages is maximized. It turns out that the optimal decision is made comparing the message importance with a time-variant threshold. Moreover, the gain of the selective transmission scheme, compared to a nonselective one, critically depends on the energy expenses, among other factors. Albeit suboptimal, practical schemes that operate under less demanding conditions than those for the optimal one are developed. Effort is placed into three directions: 1) the analysis of the optimal transmission policy for several stationary importance distributions; 2) the design of a transmission policy with invariant threshold that entails asymptotic optimality; and 3) the design of an adaptive algorithm that estimates the importance distribution from the actual received (or sensed) messages. Numerical results corroborating our theoretical claims and quantifying the gains of implementing the selective scheme close this paper. View full abstract»

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  • A Simple and Approximate Model for Nonsaturated IEEE 802.11 DCF

    Page(s): 1539 - 1553
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3514 KB) |  | HTML iconHTML  

    We propose an approximate model for a nonsaturated IEEE 802.11 DCF network that is simpler than others that have appeared in the literature. Our key simplification is that the attempt rate in the nonsaturated setting can be approximated by scaling the attempt rate of the saturated setting with an appropriate factor. Use of different scaling factors leads to variants of the model for a small buffer and an infinite buffer. We develop a general fixed-point analysis that we demonstrate can have nonunique solutions for the infinite buffer model variant under moderate traffic. Nevertheless, in an asymptotic regime that applies to light traffic, we are able to prove uniqueness of the fixed point and predict the offered load at which the maximum throughput is achieved. We verify our model using ns-2 simulation and show that our MAC access delay results are the most accurate among related work, while our collision probability and throughput results achieve comparable accuracy to (D. Malone et al., 2007), (K. Duffy et al., 2007). View full abstract»

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  • Route Optimization in Nested NEMO: Classification, Evaluation, and Analysis from NEMO Fringe Stub Perspective

    Page(s): 1554 - 1572
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5546 KB) |  | HTML iconHTML  

    Mobile IP is the basic solution to providing host mobility, whereas network mobility (NEMO) refers to the concept of the collective mobility of a set of nodes. The NEMO basic support protocol has been proposed in IETF as a first solution to the problem of network mobility. The main limitation of this basic solution is that it forces triangular routing, i.e., packets are always forwarded through the home agent (HA), following a suboptimal path. This is because each sub-NEMO obtains a care of address (CoA) that belongs to the home prefix of its parent mobile router. Such a CoA is not topologically meaningful in the current location, since the parent mobile router could also be away from home, and hence, packets addressed to the CoA are forwarded through the HA of the parent NEMO. To solve this problem, various extended proposals, with differing approaches and goals, exist for route optimization (RO) in NEMO applications. Their influences on the RO performance have been evaluated by classifying the detailed operations performed within the nested NEMO network, and then each category is analyzed in detail. The modeling of the detailed RO operation is intended to quantify the tradeoffs between the different approaches in order to provide a basis for the selection decision. In particular, the proposed grouping of the different proposals, based on their address configuration strategy, clarifies their similarities and differences, and provides some useful insights into the various methods that have been developed. In conclusion, it is suggested that, when choosing a solution for deploying NEMO, the designer has to balance his choices between the different pros and cons, and the different cases of application that are derived in this paper. View full abstract»

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  • The Orphan Problem in ZigBee Wireless Networks

    Page(s): 1573 - 1584
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4257 KB) |  | HTML iconHTML  

    ZigBee is a communication standard which is considered to be suitable for wireless sensor networks. In ZigBee, a device (with a permanent 64-bit MAC address) is said to join a network if it can successfully obtain a 16-bit network address from a parent device. Parent devices calculate addresses for their child devices by a distributed address assignment scheme. This assignment is easy to implement, but it restricts the number of children of a device and the depth of the network. We observe that the ZigBee address assignment policy is too conservative, thus usually making the utilization of the address pool poor. Those devices that cannot receive network addresses will be isolated from the network and become orphan nodes. In this paper, we show that the orphan problem can be divided into two subproblems: the bounded-degree-and-depth tree formation (BDDTF) problem and the end-device maximum matching (EDMM) problem. We then propose algorithms to relieve the orphan problem. Our simulation results show that the proposed schemes can effectively reduce the number of orphan devices compared to the ZigBee strategy. View full abstract»

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  • TMC Information for authors

    Page(s): c3
    Save to Project icon | Request Permissions | PDF file iconPDF (123 KB)  
    Freely Available from IEEE
  • [Back cover]

    Page(s): c4
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    Freely Available from IEEE

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