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Mobile Computing, IEEE Transactions on

Issue 10 • Date Oct. 2006

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

    Publication Year: 2006 , Page(s): c1
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    Freely Available from IEEE
  • [Inside front cover]

    Publication Year: 2006 , Page(s): c2
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    Freely Available from IEEE
  • Energy and Spatial Reuse Efficient Network-Wide Real-Time Data Broadcasting in Mobile Ad Hoc Networks

    Publication Year: 2006 , Page(s): 1297 - 1312
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3812 KB) |  | HTML iconHTML  

    In this paper, we present NB-TRACE, which is an energy-efficient network-wide voice broadcasting architecture for mobile ad hoc networks. In the NB-TRACE architecture, the network is organized into overlapping clusters through a distributed algorithm, where the clusterheads create a nonconnected dominating set. Channel access is regulated through a distributed TDMA scheme maintained by the clusterheads. The first group of packets of a broadcast session is broadcast through flooding, where each data rebroadcast is preceded by an acknowledgment to the upstream node. Nodes that do not get an acknowledgment for a predetermined time, except the clusterheads, cease to rebroadcast, which prunes the redundant retransmissions. The connected dominating set formed through this basic algorithm is broken in time due to node mobility. The network responds to the broken links through multiple mechanisms to ensure the maintenance of the connected dominating set. We compare NB-TRACE with four network layer broadcast routing algorithms (flooding, gossiping, counter-based broadcasting, and distance-based broadcasting) and three medium access control protocols (IEEE 802.11, SMAC, and MH-TRACE) through extensive ns-2 simulations. Our results show that NB-TRACE outperforms other network/MAC layer combinations in minimizing energy dissipation and optimizing spatial reuse, while producing competitive QoS performance View full abstract»

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  • Scalable and QoS-Aware Dynamic Slot Assignment and Piconet Partitioning to Enhance the Performance of Bluetooth Ad Hoc Networks

    Publication Year: 2006 , Page(s): 1313 - 1330
    Cited by:  Papers (1)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3853 KB) |  | HTML iconHTML  

    Bluetooth is a radio technology for wireless personal area networks in the 2.4 GHz ISM frequency band and allows short-range devices to be connected in the form of ad hoc networks. The Bluetooth medium access control protocol is based on a strict master/slave concept wherein any communication between slave devices has to go through the master. While this model is simple, the use of such a nonoptimal packet forwarding scheme incurs much longer delays between any two slave-devices as double the bandwidth is used by the master. In addition, if two or more devices want to communicate as a group, this can only be achieved by either multiple unicast transmissions or a piconet-wide broadcast from the master. To handle these issues efficiently, we propose a novel combination of dynamic slot assignment (DSA) and piconet partitioning. With DSA, the piconet master dynamically assigns slots to slaves so as to allow them to communicate directly with each other without any intervention from the master. Our proposed communication architecture provides for enhanced quality of service (QoS), better admission control, and multidevice conversation, which make a multicast-like communication feasible within the piconet. To widen the scope of DSA, we propose a QoS-aware enhanced DSA (EDSA) version where dynamic piconet partitioning and scatternet support are exploited by grouping devices into piconets as per their connection endpoints, enabling it to be employed over a scatternet. We have performed extensive simulations and observe that these schemes drastically enhance Bluetooth performance in terms of the delay and the throughput, while significantly reducing the network power consumption View full abstract»

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  • Improving Awareness in Mobile CSCW

    Publication Year: 2006 , Page(s): 1331 - 1346
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4181 KB) |  | HTML iconHTML  

    The diffusion of mobile devices in the working landscape is promoting collaboration across time and space. Following through this development, we investigate opportunities for improving awareness in mobile environments with a view to enable collaboration under power constraints and transitory network disconnections. We elaborate in particular on synchronous CSCW and expose with it significant details of group awareness, while we contribute a protocol for awareness support over large areas that strikes a balance between energy consumption and notification time. To avoid user disruption, this protocol notifies awareness information in a multicast fashion, while the bandwidth is allocated dynamically among notifications and data requests, thus minimizing the time needed by each one of them and ensuring the isochronous delivery of information to all clients. The efficiency and scalability of our protocol are evaluated with simulation experiments, whereby we compare various notification schemes and finally choose one that changes dynamically over time View full abstract»

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  • A Cross-Layer (Layer 2 + 3) Handoff Management Protocol for Next-Generation Wireless Systems

    Publication Year: 2006 , Page(s): 1347 - 1360
    Cited by:  Papers (74)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2999 KB) |  | HTML iconHTML  

    Next-generation wireless systems (NGWS) integrate different wireless networks, each of which is optimized for some specific services and coverage area to provide ubiquitous communications to the mobile users. It is an important and challenging issue to support seamless handoff management in this integrated architecture. The existing handoff management protocols are not sufficient to guarantee handoff support that is transparent to the applications in NGWS. In this work, a cross-layer (layer 2 + 3) handoff management protocol, CHMP, is developed to support seamless intra and intersystem handoff management in NGWS. Cross-layer handoff management protocol uses mobile's speed and handoff signaling delay information to enhance the handoff performance of mobile IP that is proposed to support mobility management in wireless IP networks. First, the handoff performance of mobile IP is analyzed with respect to its sensitivity to the link layer (layer 2) and network layer (layer 3) parameters. Then, a cross-layer handoff management architecture is developed using the insights learnt from the analysis. Based on this architecture, the detailed design of CHMP is carried out. Finally, extensive simulation experiments are carried out to evaluate the performance of CHMP. The theoretical analysis and simulation results show that CHMP significantly enhances the performance of both intra and intersystem handoffs View full abstract»

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  • Toward Secure Low Rate Wireless Personal Area Networks

    Publication Year: 2006 , Page(s): 1361 - 1373
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2959 KB) |  | HTML iconHTML  

    Low rate wireless personal area networks (LR-WPANs) offer device level wireless connectivity. They bring to light a host of new applications as well as enhance existing applications. Due to their low cost, low power consumption and self-organization features, LR-WPANs are ideal for applications such as public security, battle field monitoring, inventory tracking, as well as home and office automation. Nevertheless, one critical issue, security, needs to be solved before LR-WPANs are commonly accepted. Pursuing security in LR-WPANs is a challenging task. On one hand, wireless communications are inherently susceptible to interception and interference. On the other hand, most devices in LR-WPANs are resource-constrained and lack physical safeguards. This paper presents a systematic analysis of the threats faced by LR-WPANs with respect to the protocol stack defined by IEEE 802.15.4 and the ZigBee Alliance. Attacks are modeled and their impacts are evaluated. Some security problems within the current LR-WPAN security architecture are identified and remedies are suggested. Countermeasures of various attacks are also given View full abstract»

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  • Delay-Sensitive Packet Scheduling for a Wireless Access Link

    Publication Year: 2006 , Page(s): 1374 - 1383
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2576 KB) |  | HTML iconHTML  

    As the delay is a critical QoS factor, packet scheduling over a wireless access link that often becomes congested needs to have the objective of meeting each user's delay requirement. To incorporate the delay into the scheduler design, we consider the objective of maximizing the total utility (UT). However, since a utility-based scheduler that concerns delay requires high complexity, we introduce the concept of marginal utility. Representing the objective as minimizing the total marginal utility (mt), we develop some related properties for maximizing UT and minimizing MT. For the case with fixed service time, we show that the outcome of MT minimization becomes equivalent to that of UT maximization. For the more complicated case of varying service time, the MT minimization sheds light on the design of a simple scheduler. Overall, the marginal utility requires significantly low complexity for packet scheduling compared to the ordinary utility. Through simulations, we confirm that the marginal utility gives a way of flexible scheduling in meeting various delay requirements View full abstract»

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  • MobiEyes: A Distributed Location Monitoring Service Using Moving Location Queries

    Publication Year: 2006 , Page(s): 1384 - 1402
    Cited by:  Papers (31)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2751 KB) |  | HTML iconHTML  

    With the growing popularity and availability of mobile communications, our ability to stay connected while on the move is becoming a reality instead of science fiction as it was just a decade ago. An important research challenge for modern location-based services is the scalable processing of location monitoring requests on a large collection of mobile objects. The centralized architecture, though studied extensively in literature, would create intolerable performance problems as the number of mobile objects grows significantly. This paper presents a distributed architecture and a suite of optimization techniques for scalable processing of continuously moving location queries. Moving location queries can be viewed as standing location tracking requests that continuously monitor the locations of mobile objects of interest and return a subset of mobile objects when certain conditions are met. We describe the design of MobiEyes, a distributed real time location monitoring system in a mobile environment. The main idea behind the MobiEyes' distributed architecture is to promote a careful partition of a real time location monitoring task into an optimal coordination of server-side processing and client-side processing. Such a partition allows evaluating moving location queries with a high degree of precision using a small number of location updates, thus providing highly scalable location monitoring services. A set of optimization techniques are used to limit the amount of computation to be handled by the mobile objects and enhance the overall performance and system utilization of MobiEyes. Important metrics to validate the proposed architecture and optimizations include messaging cost, server load, and amount of computation at individual mobile objects. We evaluate the scalability of the MobiEyes location monitoring approach using a simulation model based on a mobile setup. Our experimental results show that MobiEyes can lead to significant savings in terms of server lo- - ad and messaging cost when compared to solutions relying on central processing of location information View full abstract»

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  • DOA: DSR over AODV Routing for Mobile Ad Hoc Networks

    Publication Year: 2006 , Page(s): 1403 - 1416
    Cited by:  Papers (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1110 KB)  

    We present a lightweight hierarchical routing model, way point routing (WPR), in which a number of intermediate nodes on a route are selected as waypoints and the route is divided into segments by the waypoints. The waypoints, including the source and the destination, run a high-level intersegment routing protocol, while the nodes on each segment run a low-level intrasegment routing protocol. One distinct advantage of our model is that when a node on the route moves out or fails, instead of discarding the whole original route and discovering a new route from the source to the destination, only the two waypoint nodes of the broken segment have to find a new segment. In addition, our model is lightweight because it maintains a hierarchy only for nodes on active routes. On the other hand, existing hierarchical routing protocols such as CGSR and ZRP maintain hierarchies for the entire network. We present an instantiation of WPR, where we use DSR as the intersegment routing protocol and AODV as the intrasegment routing protocol. This instantiation is termed DSR over AODV (DOA) routing protocol. Thus, DSR and AODV - two well-known on-demand routing protocols for MANETs - are combined into one hierarchical routing protocol and become two special cases of our protocol. Furthermore, we present two novel techniques for DOA: one is an efficient loop detection method and the other is a multitarget route, discovery. Simulation results show that DOA scales well for large networks with more than 1,000 nodes, incurring about 60 percent-80 percent less overhead than AODV, while other metrics are better than or comparable to AODV and DSR View full abstract»

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  • Concealed Data Aggregation for Reverse Multicast Traffic in Sensor Networks: Encryption, Key Distribution, and Routing Adaptation

    Publication Year: 2006 , Page(s): 1417 - 1431
    Cited by:  Papers (53)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1540 KB) |  | HTML iconHTML  

    Routing in wireless sensor networks is different from that in commonsense mobile ad-hoc networks. It mainly needs to support reverse multicast traffic to one particular destination in a multihop manner. For such a communication pattern, end-to-end encryption is a challenging problem. To save the overall energy resources of the network, sensed data needs to be consolidated and aggregated on its way to the final destination. We present an approach that 1) conceals sensed data end-to-end by 2) still providing efficient and flexible in-network data aggregation. The aggregating intermediate nodes are not required to operate on the sensed plaintext data. We apply a particular class of encryption transformations and discuss techniques for computing the aggregation functions "average" and "movement detection." We show that the approach is feasible for the class of "going down" routing protocols. We consider the risk of corrupted sensor nodes by proposing a key predistribution algorithm that limits an attacker's gain and show how key predistribution and a key-ID sensitive "going down" routing protocol help increase the robustness and reliability of the connected backbone View full abstract»

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  • Optimal Transmit Power in Wireless Sensor Networks

    Publication Year: 2006 , Page(s): 1432 - 1447
    Cited by:  Papers (53)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1701 KB) |  | HTML iconHTML  

    Power conservation is one of the most important issues in wireless ad hoc and sensor networks, where nodes are likely to rely on limited battery power. Transmitting at unnecessarily high power not only reduces the lifetime of the nodes and the network, but also introduces excessive interference. It is in the network designer's best interest to have each node transmit at the lowest possible power while preserving network connectivity. In this paper, we investigate the optimal common transmit power, defined as the minimum transmit power used by all nodes necessary to guarantee network connectivity. This is desirable in sensor networks where nodes are relatively simple and it is difficult to modify the transmit power after deployment. The optimal transmit power derived in this paper is subject to the specific routing and medium access control (MAC) protocols considered; however, the approach can be extended to other routing and MAC protocols as well. In deriving the optimal transmit power, we distinguish ourselves from a conventional graph-theoretic approach by taking realistic physical layer characteristics into consideration. In fact, connectivity in this paper is defined in terms of a quality of service (QoS) constraint given by the maximum tolerable bit error rate (BER) at the end of a multihop route with an average number of hops View full abstract»

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  • A Distributed Channel Access Protocol for Ad Hoc Networks with Feedback Power Control

    Publication Year: 2006 , Page(s): 1448 - 1459
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1440 KB) |  | HTML iconHTML  

    Distributed power control schemes are extensively employed in the cellular networks and are capable of improving the capacity of the network. However, the power control schemes from the cellular networks suffer from performance degradation due to self and direct-interference and hidden-terminal problems when directly employed in ad hoc networks. Most of the existing channel reservation-based power control protocols for ad hoc networks employ incremental power allocation rather than global allocation of the power to the incoming links; thus, they may not effectively utilize the spatial frequency reuse in the network. This paper presents a distributed channel access protocol that couples the channel reservation and the iterative/global transmission power control schemes in ad hoc networks. The designed protocol considers the convergence problem of the global power control in ad hoc networks. The designed access criteria employ the local admission control based on the sufficient criteria for admissibility and global power control for balancing the SIR (signal to interference ratio) of the links. In the performance evaluation study of the designed protocol, an almost two-fold increase in the throughput and capacity is observed compared to the existing power-controlled protocol for ad hoc networks View full abstract»

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  • On the Construction of a Strongly Connected Broadcast Arborescence with Bounded Transmission Delay

    Publication Year: 2006 , Page(s): 1460 - 1470
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1366 KB) |  | HTML iconHTML  

    Energy conservation is an important concern in wireless networks. Many algorithms for constructing a broadcast tree with minimum energy consumption and other goals have been developed. However, no previous research work considers the total energy consumption and transmission delays of the broadcast tree simultaneously. In this paper, based on an (alpha, beta)-tree, a novel concept to wireless networks, we define a new strongly connected broadcast arborescence with bounded transmission delay (SBAT) problem and design the strongly connected broadcast arborescence (SBA) algorithm with linear running time to construct a strongly connected broadcast tree with bounded total power, while satisfying the constraint that the transmission delays between the source and the other hosts are also bounded. We also propose the distributed version of the SBA algorithm. The theoretical analysis and simulation results show that the SBA algorithm gives a proper solution to the SBAT problem View full abstract»

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  • A Comment on "HEED: A Hybrid, Energy-Efficient, Distributed Clustering Approach for Ad Hoc Sensor Networks'

    Publication Year: 2006 , Page(s): 1471 - 1472
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB) |  | HTML iconHTML  

    We provide a better sufficient condition for the connectivity of cluster heads asymptotically almost surely (a.a.s.) and a tighter bound on the number of cluster heads in HEED (O. Younis and S. Fahmy, 2004) View full abstract»

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  • TMC Information for authors

    Publication Year: 2006 , Page(s): c3
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 2006 , 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