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Mobile Computing, IEEE Transactions on

Issue 6 • Date Nov.-Dec. 2005

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Displaying Results 1 - 17 of 17
  • [Cover 2]

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

    Page(s): c2
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  • A mobility prediction architecture based on contextual knowledge and spatial conceptual maps

    Page(s): 537 - 551
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1240 KB) |  | HTML iconHTML  

    User Mobility prediction represents a key component in assisting handoff management, resource reservation, and service preconfiguration. However, most of the existing approaches presume that the user travels in an a priori known pattern with some regularity; an assumption that may not always hold. This paper presents a novel framework for user mobility prediction that can accurately predict the traveling trajectory and destination using knowledge of user's preferences, goals, and analyzed spatial information without imposing any assumptions about the availability of users' movements history. This framework thus incorporates the notion of combining user context and spatial conceptual maps in the prediction process. The main objective of this notion is to circumvent the difficulties that arise in predicting the user's future location when adequate knowledge about the history of user's traveling patterns is not available. Using concepts of evidential reasoning of Dempster-Shafer's theory, the user's navigation behavior is captured by gathering pieces of evidence concerning different groups of candidate future locations. These groups are then refined to predict the user's future location when evidence accumulates using the Dempster rule of combination. Simulation results are presented to demonstrate the performance of the proposed framework. View full abstract»

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  • A user pattern learning strategy for managing users' mobility in UMTS networks

    Page(s): 552 - 566
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1080 KB) |  | HTML iconHTML  

    Third-generation mobile systems provide access to a wide range of services and enable mobile users to communicate regardless of their geographical location and their roaming characteristics. Due to the growing number of mobile users, global connectivity, and the small size of cells, one of the most critical issues regarding these networks is location management. In recent years, several strategies have been proposed to improve the performance of the location management procedure in 3G mobile networks. In this paper, we present a user pattern learning strategy (UPL) using neural networks to reduce the location update signaling cost by increasing the intelligence of the location procedure in UMTS. This strategy associates to each user a list of cells where she is likely to be with a given probability in each time interval. The implementation of this strategy has been subject to extensive tests. The results obtained confirm the efficiency of UPL in significantly reducing the costs of both location updates and call delivery procedures when compared to the UMTS standard and with other strategies well-known in the literature. View full abstract»

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  • An analysis of error inducing parameters in multihop sensor node localization

    Page(s): 567 - 577
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1112 KB) |  | HTML iconHTML  

    Ad hoc localization of wireless sensor nodes is a fundamental problem in wireless sensor networks. Despite the recent proposals for the development of ad hoc localization algorithms, the fundamental behavior in systems using measurements has not been characterized. In this paper, we take a first step toward such a characterization by examining the behavior of error inducing parameters in multihop localization systems in an algorithm independent manner. We first derive the Crame Rao Bound for Gaussian measurement error for multihop localization systems using distance and angular measurements. Later on, we use these bounds on a carefully controlled set of scenarios to study the trends in the error induced by the measurement technology accuracy, network density, beacon node concentration, and beacon uncertainty. By exposing these trends, the goal of this paper is to develop a fundamental understanding of the error behavior that can provide a set of guidelines to be considered during the design and deployment of multihop localization systems. View full abstract»

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  • An efficient fault-tolerant distributed channel allocation algorithm for cellular networks

    Page(s): 578 - 587
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB) |  | HTML iconHTML  

    A channel allocation algorithm in a cellular network consists of two parts: a channel acquisition algorithm and a channel selection algorithm. Some of the previous works in this field focused on centralized approaches to allocating channels. But, centralized approaches are neither scalable nor reliable. Recently, distributed dynamic channel allocation algorithms have been proposed, and they have gained a lot of attention due to their high reliability and scalability. But, in most of the algorithms, the cell that wants to borrow a channel has to wait for replies from all its interference neighbors and, hence, is not fault-tolerant. In this paper, we propose a new algorithm that is fault-tolerant and makes full use of the available channels. It can tolerate the failure of mobile nodes as well as static nodes without any significant degradation in service. View full abstract»

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  • ATP: a reliable transport protocol for ad hoc networks

    Page(s): 588 - 603
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1248 KB) |  | HTML iconHTML  

    Existing works have approached the problem of reliable transport in ad hoc networks by proposing mechanisms to improve TCP's performance over such networks, In this paper, we show through detailed arguments and simulations that several of the design elements in TCP are fundamentally inappropriate for the unique characteristics of ad hoc networks. Given that ad hoc networks are typically stand-alone, we approach the problem of reliable transport from the perspective that it is justifiable to develop an entirely new transport protocol that is not a variant of TCP. Toward this end, we present a new reliable transport layer protocol for ad hoc networks called ATP (ad hoc transport protocol). We show through ns2-based simulations that ATP outperforms default TCP as well as TCP-ELFN and ATCP. View full abstract»

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  • Design and analysis of time-based code allocation schemes in W-CDMA systems

    Page(s): 604 - 615
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1352 KB) |  | HTML iconHTML  

    Efficient resource allocation for requests is an important issue in the radio resource management. In the third generation mobile communication systems, Orthogonal Variable Spreading Factor (OVSF) codes are used for spreading codes. In this paper, we consider the OVSF code allocation problem for supporting real-time services in which the service time of a request can be obtained a priori. The impact of the remaining time factor on the OVSF code allocation in W-CDMA systems is investigated. Two time-based allocation schemes are proposed for code assignment and reassignment. This paper represents the first attempt on addressing the remaining time impact on the OVSF code allocation. Simulation results show that the time-based allocation schemes have better performance on reducing the blocking probability and the reassignment cost. View full abstract»

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  • Distributed fair scheduling in a wireless LAN

    Page(s): 616 - 629
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB) |  | HTML iconHTML  

    Fairness is an important issue when accessing a shared wireless channel. With fair scheduling, it is possible to allocate bandwidth in proportion to weights of the packet flows sharing the channel. This paper presents a fully distributed algorithm for fair scheduling in a wireless LAN. The algorithm can be implemented without using a centralized coordinator to arbitrate medium access. The proposed protocol is derived from the Distributed Coordination Function in the IEEE 802.11 standard. Simulation results show that the proposed algorithm is able to schedule transmissions such that the bandwidth allocated to different flows is proportional to their weights. An attractive feature of the proposed approach is that it can be implemented with simple modifications to the IEEE 802.11 standard. View full abstract»

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  • Dynamical mobile terminal location registration in wireless PCS networks

    Page(s): 630 - 640
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB) |  | HTML iconHTML  

    In this paper, we propose a mobile terminal (MT) location registration/update model. In this model, the registration decision is based on two factors-the time elapsed since last call arrival and the distance the MT has traveled since last registration. It is established that the optimal registration strategy can be represented by a curve. Only when the state of the system reaches this curve is a registration performed. In order for an MT to calculate its traveled distance, an interactive implementation scheme and a distance calculation algorithm are developed. When the call interarrival times are independent and geometrically distributed, the proposed model becomes a distance-based model and, in this case, the optimal registration strategy is of threshold structure. For the distance-based model, a single sample path-based ordinal optimization algorithm is devised. In this algorithm, without any knowledge about the system parameters, the MT observes the system state transitions, estimates the ordinal of a set of strategies, and updates the registration strategy adaptively. Since only a single sample path is used, this algorithm can be implemented online. Several numerical examples are provided to compare the proposed model and the existing ones. View full abstract»

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  • Location management of correlated mobile users in the UMTS

    Page(s): 641 - 651
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB) |  | HTML iconHTML  

    In this paper, we propose concurrently searching for correlated mobile users in mobile communications networks. Previous work either focuses on locating a single mobile user or assumes that the locations of mobile users are statistically independent. We first propose a mobility model in which the movements of mobile users are statistically correlated. Next, we use the theory of Markov chain to derive the joint probability density function of the locations of mobile users. In addition, we propose a novel approach to discover the correlations among the locations of mobile users without explicitly calculating the joint probability density function. Our simulation results indicate that exploring the correlations among the locations of mobile users could significantly reduce the average paging delay and increase the maximum stable throughput. View full abstract»

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  • Subcarrier allocation and bit loading algorithms for OFDMA-based wireless networks

    Page(s): 652 - 662
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (792 KB) |  | HTML iconHTML  

    Orthogonal Frequency Division Multiple Access (OFDMA) is an emerging multiple access technology. In this paper, we consider OFDMA in the context of fixed wireless networks. This paper addresses the problem of assigning subcarriers and bits to point-to-point wireless links in the presence of cochannel interference and Rayleigh fading. The objective is to minimize the total transmitted power over the entire network while satisfying the data rate requirement of each link. We formulate this problem as a constrained optimization problem and present centralized algorithms. The simulation results show that our approach results in an efficient assignment of subcarriers and transmitter power levels in terms of the energy required for transmitting each bit of information. However, centralized algorithms require knowledge of the entire network topology and channel characteristics of every link. In a practical scenario, that would not be the situation and there is a need for distributed rate allocation algorithms. To address this need, we also present a distributed algorithm for allocating subcarriers and bits in order to satisfy the rate requirements of the links. View full abstract»

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  • Annual index

    Page(s): tm05
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    Page(s): 663
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  • [Advertisement]

    Page(s): 664
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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