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Mobile Computing, IEEE Transactions on

Issue 2 • Date Feb. 2014

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Displaying Results 1 - 18 of 18
  • Leveraging Social Networks for P2P Content-Based File Sharing in Disconnected MANETs

    Page(s): 235 - 249
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    Current peer-to-peer (P2P) file sharing methods in mobile ad hoc networks (MANETs) can be classified into three groups: flooding-based, advertisement-based, and social contact-based. The first two groups of methods can easily have high overhead and low scalability. They are mainly developed for connected MANETs, in which end-to-end connectivity among nodes is ensured. The third group of methods adapts to the opportunistic nature of disconnected MANETs but fails to consider the social interests (i.e., contents) of mobile nodes, which can be exploited to improve the file searching efficiency. In this paper, we propose a P2P content-based file sharing system, namely SPOON, for disconnected MANETs. The system uses an interest extraction algorithm to derive a node's interests from its files for content-based file searching. For efficient file searching, SPOON groups common-interest nodes that frequently meet with each other as communities. It takes advantage of node mobility by designating stable nodes, which have the most frequent contact with community members, as community coordinators for intracommunity searching, and highly mobile nodes that visit other communities frequently as community ambassadors for intercommunity searching. An interest-oriented file searching scheme is proposed for high file searching efficiency. Additional strategies for file prefetching, querying-completion, and loop-prevention, and node churn consideration are discussed to further enhance the file searching efficiency. We first tested our system on the GENI Orbit testbed with a real trace and then conducted event-driven experiment with two real traces and NS2 simulation with simulated disconnected and connected MANET scenarios. The test results show that our system significantly lowers transmission cost and improves file searching success rate compared to current methods. View full abstract»

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  • TurfCast: A Service for Controlling Information Dissemination in Wireless Networks

    Page(s): 250 - 262
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1250 KB) |  | HTML iconHTML  

    Recent years have witnessed mass proliferation of mobile devices with rich wireless communication capabilities as well as emerging mobile device-based information dissemination applications that leverage these capabilities. This paper proposes TurfCast, a novel information dissemination service that selectively broadcasts information in particular "turfs,â abstract logical spaces in which receivers are situated. Such turfs can be temporal or spatial based on receivers' lingering time or physical areas, respectively. TurfCast has many applications such as electronic proximity advertising and mobile social networking. To enable TurfCast, we propose two supporting technologies: TurfCode and TurfBurst. TurfCode is a nested 0-1 fountain code that enables the broadcaster to transmit either all information or none at all to receivers. TurfBurst exploits the Shannon bound to differentiate among receivers: those who cannot receive information fast enough receive none at all, even if they linger near the broadcaster. We implement TurfCast on real-world devices and conduct experiments in both indoor and outdoor environments. Our experimental results illustrate TurfCast's potential for controlling information dissemination in wireless networks. View full abstract»

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  • RBTP: Low-Power Mobile Discovery Protocol through Recursive Binary Time Partitioning

    Page(s): 263 - 273
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (929 KB) |  | HTML iconHTML  

    With increasing prevalence of mobile wireless devices with WiFi and Bluetooth capability, new applications that can make use of limited contact opportunities when the devices are physically close are emerging. Proximity-based social networking, and location specific dissemination of advertisements and events, are some such applications. Discovering such services is a challenging problem due to energy budget limitations, user mobility, and nonuniformity and the time-varying nature of energy budgets across users. It is important to rapidly discover such mobile services to make use of limited contact opportunities. To support such applications, we seek to design a localized discovery scheme that can minimize the expected contact latency between mobile phones with limited energy budgets. All the existing neighbor discovery schemes assume lack of any time synchronization. However, in practice sufficiently accurate time synchronization can be achieved with existing time synchronization techniques. We propose Recursive Binary Time Partitioning (RBTP), a scheme that determines how the devices should wake up and sleep to achieve minimal contact latency with other nearby devices. RBTP achieves provable performance bound and outperforms state-of-the-art asynchronous protocols for smartphones. When compared with the optimum scheme, the contact latency is shown to be within a factor of (9/8) in the expected case and 2 in the worst case. View full abstract»

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  • Video Dissemination over Hybrid Cellular and Ad Hoc Networks

    Page(s): 274 - 286
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    We study the problem of disseminating videos to mobile users by using a hybrid cellular and ad hoc network. In particular, we formulate the problem of optimally choosing the mobile devices that will serve as gateways from the cellular to the ad hoc network, the ad hoc routes from the gateways to individual devices, and the layers to deliver on these ad hoc routes. We develop a Mixed Integer Linear Program (MILP)-based algorithm, called POPT, to solve this optimization problem. We then develop a Linear Program (LP)-based algorithm, called MTS, for lower time complexity. While the MTS algorithm achieves close-to-optimum video quality and is more efficient than POPT in terms of time complexity, the MTS algorithm does not run in real time for hybrid networks with large numbers of nodes. We, therefore, propose a greedy algorithm, called THS, which runs in real time even for large hybrid networks. We conduct extensive packet-level simulations to compare the performance of the three proposed algorithms. We found that the THS algorithm always terminates in real time, yet achieves a similar video quality to MTS. Therefore, we recommend the THS algorithm for video dissemination over hybrid cellular and ad hoc networks. View full abstract»

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  • HAWK: An Unmanned Mini-Helicopter-Based Aerial Wireless Kit for Localization

    Page(s): 287 - 298
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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (867 KB) |  | HTML iconHTML  

    This paper presents a fully functional and highly portable mini Unmanned Aerial Vehicle (UAV) system, HAWK, for conducting aerial localization. HAWK is a programmable mini helicopter Draganflyer X6 armed with a wireless sniffer Nokia N900. We developed custom PI-Control laws to implement a robust waypoint algorithm for the mini helicopter to fly a planned route. A Moore space filling curve is designed as a flight route for HAWK to survey a specific area. A set of theorems were derived to calculate the minimum Moore curve level for sensing all targets in the area with minimum flight distance. With such a flight strategy, we can confine the location of a target of interest to a small hot area. We can recursively apply the Moore curve-based flight route to the hot area for a fine-grained localization of a target of interest. We have conducted extensive experiments to validate the feasibility of HAWK and our theory. A demo of HAWK in autonomous fly is available at http://www.youtube.com/watch?v=ju86xnHbEq0. View full abstract»

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  • Evaluation of a Multihop Airborne IP Backbone with Heterogeneous Radio Technologies

    Page(s): 299 - 310
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4508 KB) |  | HTML iconHTML  

    In recent years, there has been increasing interest in the US Department of Defense to build an on-demand airborne network for communications relay utilizing high-capacity, long-range military radio systems. While these systems operate well in a network of homogeneous systems, platforms generally employ multiple heterogeneous radio systems making internetworking difficult due to varying radio characteristics and lack of interoperability. Although simulations and emulation tests can provide a baseline for how systems will perform in a controlled environment, field tests are crucial to demonstrate capabilities in real-world operating environments. In this paper, we present measurement results from a field test involving two airborne platforms forming a dynamically routed aerial IP backbone over 200 nautical miles with various radio systems as part of the C4ISR on-the-move 2010 exercise. We present measurement results on per link performance, radio-to-router interface performance, and multihop network performance results with prototype software on open source platforms. Additionally, key lessons learned and recommendations are given. View full abstract»

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  • LOS and NLOS Classification for Underwater Acoustic Localization

    Page(s): 311 - 323
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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (972 KB) |  | HTML iconHTML  

    The low sound speed in water makes propagation delay (PD)-based range estimation attractive for underwater acoustic localization (UWAL). However, due to the long channel impulse response and the existence of reflectors, PD-based UWAL suffers from significant degradation when PD measurements of nonline-of-sight (NLOS) communication links are falsely identified as line-of-sight (LOS). In this paper, we utilize expected variation of PD measurements due to mobility of nodes and present an algorithm to classify the former into LOS and NLOS links. First, by comparing signal strength-based and PD-based range measurements, we identify object-related NLOS (ONLOS) links, where signals are reflected from objects with high reflection loss, for example, ships hull, docks, rocks and so on. In the second step, excluding PD measurements related to ONLOS links, we use a constrained expectation-maximization algorithm to classify PD measurements into two classes: LOS and sea-related NLOS (SNLOS), and to estimate the statistical parameters of each class. Since our classifier relies on models for the underwater acoustic channel, which are often simplified, alongside simulation results, we validate the performance of our classifier based on measurements from three sea trials. Both our simulation and sea trial results demonstrate a high detection rate of ONLOS links, and accurate classification of PD measurements into LOS and SNLOS. View full abstract»

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  • New Directions into the Stochastic Geometry Analysis of Dense CSMA Networks

    Page(s): 324 - 336
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (679 KB) |  | HTML iconHTML  

    We consider extended wireless networks characterized by a random topology of access points (APs) contending for medium access over the same wireless channel. Recently, stochastic geometry has emerged as a powerful tool to analyze random networks adopting MAC protocols such as ALOHA and CSMA. The main strength of this methodology lies in its ability to account for the randomness in the nodes' location jointly with an accurate description at the physical layer, based on the SINR, that allows considering also random fading on each link. In this paper, we extend previous stochastic geometry models of CSMA networks, developing computationally efficient techniques to obtain throughput distributions, in addition to spatial averages, which permit us to get interesting insights into the impact of protocol parameters and channel variability on the spatial fairness among the nodes. Moreover, we extend the analysis to a significant class of topologies in which APs are not placed according to a Poisson process. View full abstract»

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  • Interference and Outage in Mobile Random Networks: Expectation, Distribution, and Correlation

    Page(s): 337 - 349
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB) |  | HTML iconHTML  

    In mobile networks, distance variations caused by node mobility generate fluctuations in the channel gains. Such fluctuations can be treated as another type of fading besides multipath effects. In this paper, the interference statistics in mobile random networks are characterized by incorporating the distance variations of mobile nodes to the channel gain fluctuations. The mean interference is calculated at the origin and at the border of a finite mobile network. The network performance is evaluated in terms of the outage probability. Compared to a static network, the interference in a single snapshot does not change under uniform mobility models. However, random waypoint mobility increases (decreases) the interference at the origin (at the border). Furthermore, due to the correlation of the node locations, the interference and outage are temporally and spatially correlated. We quantify the temporal correlation of the interference and outage in mobile Poisson networks in terms of the correlation coefficient and conditional outage probability, respectively. The results show that it is essential that routing, MAC, and retransmission schemes need to be smart (i.e., correlation-aware) to avoid bursts of transmission failures. View full abstract»

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  • Cooperative Self-Navigation in a Mixed LOS and NLOS Environment

    Page(s): 350 - 363
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1238 KB) |  | HTML iconHTML  

    We investigate the problem of cooperative self-navigation (CSN) for multiple mobile sensors in the mixed line-of-sight (LOS) and nonline-of-sight (NLOS) environment based on measuring time-of-arrival (TOA) from the cooperative sensing. We first derive an optimized recursive Bayesian solution by adopting a multiple model sampling-based importance resampling particle filter for the development of CSN. It can accommodate nonlinear signal model and non-Gaussian position movement under different levels of channel knowledge. We also utilize a Rao-Blackwellization particle filter to split the original problem by tracking the channel condition with a grid-based filter and estimating the position with a particle filter. The CSN with position and channel tracking exhibits advantage over the noncooperative methods by utilizing additional cooperative measurements. It also shows improvement over the methods without channel tracking. Simulation results validate that both schemes can take the advantage of cooperative sensing and channel condition tracking in mixed LOS/NLOS environments, which motivates future research of cooperative gain for navigation and localization in a more general environment. View full abstract»

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  • Autonomous Mobile Mesh Networks

    Page(s): 364 - 376
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1353 KB) |  | HTML iconHTML  

    Mobile ad hoc networks (MANETs) are ideal for situations where a fixed infrastructure is unavailable or infeasible. Today's MANETs, however, may suffer from network partitioning. This limitation makes MANETs unsuitable for applications such as crisis management and battlefield communications, in which team members might need to work in groups scattered in the application terrain. In such applications, intergroup communication is crucial to the team collaboration. To address this weakness, we introduce in this paper a new class of ad-hoc network called Autonomous Mobile Mesh Network (AMMNET). Unlike conventional mesh networks, the mobile mesh nodes of an AMMNET are capable of following the mesh clients in the application terrain, and organizing themselves into a suitable network topology to ensure good connectivity for both intra- and intergroup communications. We propose a distributed client tracking solution to deal with the dynamic nature of client mobility, and present techniques for dynamic topology adaptation in accordance with the mobility pattern of the clients. Our simulation results indicate that AMMNET is robust against network partitioning and capable of providing high relay throughput for the mobile clients. View full abstract»

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  • Optimal Distributed Malware Defense in Mobile Networks with Heterogeneous Devices

    Page(s): 377 - 391
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB) |  | HTML iconHTML  

    As malware attacks become more frequently in mobile networks, deploying an efficient defense system to protect against infection and to help the infected nodes to recover is important to prevent serious spreading and outbreaks. The technical challenges are that mobile devices are heterogeneous in terms of operating systems, the malware infects the targeted system in any opportunistic fashion via local and global connectivity, while the to-be-deployed defense system on the other hand would be usually resource limited. In this paper, we investigate the problem of how to optimally distribute the content-based signatures of malware, which helps to detect the corresponding malware and disable further propagation, to minimize the number of infected nodes. We model the defense system with realistic assumptions addressing all the above challenges that have not been addressed in previous analytical work. Based on the framework of optimizing the system welfare utility, which is the weighted summation of individual utility depending on the final number of infected nodes through the signature allocation, we propose an encounter-based distributed algorithm based on Metropolis sampler. Through theoretical analysis and simulations with both synthetic and realistic mobility traces, we show that the distributed algorithm achieves the optimal solution, and performs efficiently in realistic environments. View full abstract»

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  • Implementation-Based Evaluation of a Full-Fledged Multihop TDMA-MAC for WiFi Mesh Networks

    Page(s): 392 - 406
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1814 KB) |  | HTML iconHTML  

    Wireless mesh networks in general, and WiFi mesh networks in particular, offer a cost-effective option to provide broadband connectivity in sparse regions. Effective support for real-time as well as high throughput applications requires a TDMAbased approach. However, multihop TDMA implementations in wireless have been few and far-between, and for good reasons. These present significant issues in terms of time synchronization, TDMA schedule dissemination, multichannel support, routing integration, spatial reuse and so on. And achieving these efficiently, in the face of wireless channel losses presents a formidable challenge. In this work, we present an implementation of LiT MAC, a full-fledged multihop TDMA MAC, on commodity WiFi platforms. We undertake extensive evaluations using microbenchmarks as well as application level performance, using outdoor as well as indoor testbeds. We also present an integration of LiT MAC with various routing metrics, and a routing stability study of recently proposed routing metrics (ROMA, SLIQ). Our results show that we can achieve μs granularity time synchronization across several hops, and TDMA slot size as small as 2 ms. These imply low control overheads. Experiments over several days, on our nine-node outdoor testbed shows that LiT MAC's soft-state-based approach is effective in robust operation even in the presence of significant external interference. View full abstract»

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  • Novel Channel-Hopping Schemes for Cognitive Radio Networks

    Page(s): 407 - 421
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1740 KB) |  | HTML iconHTML  

    Recently, cognitive radio (CR) has become a key technology for addressing spectrum scarcity. In CR networks, spectrum access should not interfere the colocate incumbent networks. Due to the requirement above, common control channel approaches, which are widely used in traditional multichannel environments, may face serious CR long-time blocking problem and control channel saturation problem. Although channel-hopping-based approaches can avoid these two problems, existing works still have significant drawbacks including long time-to-rendezvous, unbalance channel loading, and low channel utilization. In this paper, we introduce three channel-hopping approaches, RCCH, ARCH, and SARCH for synchronous and asynchronous environments, respectively. Compared with previous works, our schemes outperform the state of the art in terms of these metrics. View full abstract»

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  • Energy-Aware Resource Allocation Strategies for LTE Uplink with Synchronous HARQ Constraints

    Page(s): 422 - 433
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (922 KB) |  | HTML iconHTML  

    In this paper, we propose a framework for energy efficient resource allocation in multiuser localized SC-FDMA with synchronous HARQ constraints. Resource allocation is formulated as a two-stage problem where resources are allocated in both time and frequency. The impact of retransmissions on the time-frequency problem segmentation is handled through the use of a novel block scheduling interval specifically designed for synchronous HARQ to ensure uplink users do not experience ARQ blocking. Using this framework, we formulate the optimal margin adaptive allocation problem, and based on its structure, we propose two suboptimal approaches to minimize average power allocation required for resource allocation while attempting to reduce complexity. Results are presented for computational complexity and average power allocation relative to system complexity and data rate, and comparisons are made between the proposed optimal and suboptimal approaches. View full abstract»

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  • Energy-Efficient Reliable Routing Considering Residual Energy in Wireless Ad Hoc Networks

    Page(s): 434 - 447
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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (817 KB) |  | HTML iconHTML  

    We propose two novel energy-aware routing algorithms for wireless ad hoc networks, called reliable minimum energy cost routing (RMECR) and reliable minimum energy routing (RMER). RMECR addresses three important requirements of ad hoc networks: energy-efficiency, reliability, and prolonging network lifetime. It considers the energy consumption and the remaining battery energy of nodes as well as quality of links to find energy-efficient and reliable routes that increase the operational lifetime of the network. RMER, on the other hand, is an energy-efficient routing algorithm which finds routes minimizing the total energy required for end-to-end packet traversal. RMER and RMECR are proposed for networks in which either hop-by-hop or end-to-end retransmissions ensure reliability. Simulation studies show that RMECR is able to find energy-efficient and reliable routes similar to RMER, while also extending the operational lifetime of the network. This makes RMECR an elegant solution to increase energy-efficiency, reliability, and lifetime of wireless ad hoc networks. In the design of RMECR, we consider minute details such as energy consumed by processing elements of transceivers, limited number of retransmissions allowed per packet, packet sizes, and the impact of acknowledgment packets. This adds to the novelty of this work compared to the existing studies. View full abstract»

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  • Harnessing the High Bandwidth of Multiradio Multichannel 802.11n Mesh Networks

    Page(s): 448 - 456
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    There has been an increasing interest in deploying wireless mesh networks (WMNs) for communication and video surveillance purposes thanks to its low cost and ease of deployment. It is well known that a major drawback of WMN is multihop bandwidth degradation, which is primarily caused by contention and radio interference. The use of mesh nodes with multiple radios and channels has been regarded as a straightforward solution to the problem in the research community. However, we demonstrate in this paper through real-world experiments that such an approach cannot resolve the multihop TCP throughput degradation problem in IEEE 802.11n mesh networks. With extensive experimentation, we verify that the degradation is principally caused by the increase in TCP Round-Trip Time (RTT) when the number of hops increases. TCP throughput is fundamentally limited inversely by the RTT. We find that the multihop TCP throughput (up to five hops) when using 802.11n is no better than when using 802.11a, despite the much higher data rate 802.11n. We attempt to use multiple parallel TCP connections as a remedy to the problem, and it turns out that the wireless bandwidth can be fully utilized with a sufficient number of parallel streams. In general, our results give a key message that TCP tuning (e.g., setting the correct TCP buffers and use of parallel streams) is of paramount importance in high-bandwidth multihop wireless mesh networks that employ the latest wireless standards. These tuning techniques have to be implemented into commercial products to fully leverage the ever advancing wireless technologies to support the growing demand of multihop communications in wireless mesh networks. View full abstract»

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  • Security Analysis of Handover Key Management in 4G LTE/SAE Networks

    Page(s): 457 - 468
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    The goal of 3GPP Long Term Evolution/System Architecture Evolution (LTE/SAE) is to move mobile cellular wireless technology into its fourth generation. One of the unique challenges of fourth-generation technology is how to close a security gap through which a single compromised or malicious device can jeopardize an entire mobile network because of the open nature of these networks. To meet this challenge, handover key management in the 3GPP LTE/SAE has been designed to revoke any compromised key(s) and as a consequence isolate corrupted network devices. This paper, however, identifies and details the vulnerability of this handover key management to what are called desynchronization attacks; such attacks jeopardize secure communication between users and mobile networks. Although periodic updates of the root key are an integral part of handover key management, our work here emphasizes how essential these updates are to minimizing the effect of desynchronization attacks that, as of now, cannot be effectively prevented. Our main contribution, however, is to explore how network operators can determine for themselves an optimal interval for updates that minimizes the signaling load they impose while protecting the security of user traffic. Our analytical and simulation studies demonstrate the impact of the key update interval on such performance criteria as network topology and user mobility. View full abstract»

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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