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Due to the uncertainty of transmission opportunities between mobile nodes, the routing of delay-tolerant networks (DTNs) exploits the mechanism of opportunistic forwarding. Efficient algorithms and policies for opportunistic forwarding are crucial for maximizing the message delivery probability while reducing the delivery cost. In this paper, we investigate the problem of energy-efficient opportunistic forwarding for DTNs. First, we model the message dissemination by introducing a continuoustime Markov framework. Based on this framework, we formulate the optimization problem of opportunistic forwarding, with the constraint of energy consumed by the message delivery for both two-hop and epidemic forwarding. Then, based on the solution of the optimization problem, we design different kinds of forwarding policies such as static and dynamic policies. Among these policies, we find that the threshold dynamic policy is optimal for both two-hop and epidemic forwarding. By simulation results, we show the accuracy of our continuous-time Markov analysis model. Furthermore, through extensive numerical results, we demonstrate that the performance of the threshold dynamic policy is the best among the static and continuous dynamic policies, and among the continuous dynamic policies, the negative-power policy provides relatively better performance. [ABSTRACT FROM PUBLISHER]

Real Time Systems are currently found in millions of devices such as GPS, laptops, cell phones, computers, etc. These systems process real time tasks in conjunction with common tasks. Their coexistence requires methods and techniques that are necessary for the proper function of the heterogeneous system. Slack Stealing methods are an important tool to know how much the real time system tasks can be delayed without affecting its proper operation, and thus assigning non real-time tasks to the processor. Delaying the execution of real-time tasks in order to reduce the response time of non-real time task could be very useful in applications such as energy saving, fault tolerance, aperiodic tasks execution, among others. Because of the computational complexity, Slack Stealing methods proposed in the literature cannot be implemented at runtime. This paper presents a theoretical analysis to reduce the computational cost of the calculation of the available system slack and an algorithm that makes its implementation feasible during runtime. [ABSTRACT FROM AUTHOR]

In this paper the authors introduce Web services technology and its applications to mobile business trans- actions. This paper shows that the Web services technology is a powerful tool to build next-generation c-Commerce applications for wireless mobile devices following the service-oriented architecture. Such an approach would bring significant benefits to organizations involved with e-Commerce. The authors further discuss the importance of ensuring high dependability of Web services and provide a literature review of state-of-the-art techniques that are critical to the implementation of practical and dependable wireless Web services. Finally, research on the design, implementation, and performance evaluation of a fault tolerance framework for wireless Web services are described. [ABSTRACT FROM AUTHOR]

The integration of Global Positioning System (GPS) receivers and sensors into mobile devices has enabled collaborative sensing applications, which monitor the dynamics of environments through opportunistic collection of data from many users' devices. One example that motivates this paper is a probe-vehicle-based automotive traffic monitoring system, which estimates traffic congestion from GPS velocity measurements reported from many drivers. This paper considers the problem of achieving guaranteed anonymity in a locational data set that includes location traces from many users, while maintaining high data accuracy. We consider two methods to reidentify anonymous location traces, target tracking, and home identification, and observe that known privacy algorithms cannot achieve high application accuracy requirements or fail to provide privacy guarantees for drivers in low-density areas. To overcome these challenges, we derive a novel time-to-confusion criterion to characterize privacy in a locational data set and propose a disclosure control algorithm (called uncertainty-aware path cloaking algorithm) that selectively reveals GPS samples to limit the maximum time-to-confusion for all vehicles. Through trace-driven simulations using real GPS traces from 312 vehicles, we demonstrate that this algorithm effectively limits tracking risks, in particular, by eliminating tracking outliers. It also achieves significant data accuracy improvements compared to known algorithms. We then present two enhancements to the algorithm. First, it also addresses the home identification risk by reducing location information revealed at the start and end of trips. Second, it also considers heading information reported by users in the tracking model. This version can thus protect users who are moving in dense areas but in a different direction from the majority. [ABSTRACT FROM AUTHOR]

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 the best of our knowledge, we are the first to implement SMC-based localization algorithms for wireless sensor networks in real environment. [ABSTRACT FROM AUTHOR]

Relay selection is crucial in improving the performance of wireless cooperative networks. Most previous works for relay selection use the current observed channel conditions to make the relay-selection decision for the subsequent frame. However, this memoryless channel assumption is often not realistic given the time-varying nature of some mobile environments. In this paper, we consider finite-state Markov channels in the relay-selection problem. Moreover, we also incorporate adaptive modulation and coding, as well as residual relay energy in the relay-selection process. The objectives of the proposed scheme are to increase spectral efficiency, mitigate error propagation, and maximize the network lifetime. The formulation of the proposed relay-selection scheme is based on recent advances in stochastic control algorithms. The obtained relay-selection policy has an indexability property that dramatically reduces the computation and implementation complexity. In addition, there is no need for a centralized control point in the network, and relays can freely join and leave from the set of potential relays. Simulation results are presented to show the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Self-stabilization is a theoretical framework of non-masking fault-tolerant distributed algorithms. A self-stabilizing system tolerates any kind and any finite number of transient faults, such as message loss, memory corruption, and topology change. Because such transient faults occur so frequently in mobile ad hoc networks, distributed algorithms on them should tolerate such events. In this paper, we propose a self-stabilizing distributed approximation algorithm for the minimum connected dominating set, which can be used, for example, as a virtual backbone or routing in mobile ad hoc networks. The size of the solution by our algorithm is at most 7.6|Dopt|+1.4, where Dopt is the minimum connected dominating set. The time complexity is O(k) rounds, where k is the depth of input BFS tree. [ABSTRACT FROM AUTHOR]

The main features of the future mobile communication systems are the provisioning of high-speed data transmissions (up to 1 Gb/s) and interactive multimedia services. For effective delivery of these services, the network must satisfy some strict quality-of-service (QoS) metrics, defined typically in terms of maximum delay and/or minimum throughput performances. According to this general vision, the integration of different layered networks play one of the most important roles in the telecommunication systems; for this reason, the paper explains the potential role of an integrated satellite-high-altitude platform (HAP) terrestrial system proposing a new multilayered inter-HAP-satellite routing (IHSR) algorithm integrated with an efficient admission control scheme in order to guarantee an adequate QoS to multimedia traffic connections. The performance of the overall architecture is evaluated through intensive simulations comparing the proposed algorithm with a previous classical routing scheme under several traffic load scenarios and network dimensions. The obtained results demonstrate the goodness of the proposed strategy in terms of handled active connections and inter-HAP link utilization. [ABSTRACT FROM AUTHOR]

This paper proposes an SAMD (Synchronization Algorithms based on Message Digest) algorithm based on message digest in order to facilitate data synchronization between a server-side database and a mobile database. The SAMD algorithm makes the images at the server-side database and the mobile database uses message digest tables to compare two images in order to select the rows needed for synchronization. If the two images are different, the synchronization progresses according to synchronization policy. The SAMD algorithm does not use techniques that are dependent on specific database venders; neither does it use triggers, stored procedures or timestamps. The SAMD uses only the standard SQL functions for the synchronization. Therefore the SAMD algorithm can be used in any combinations of server-side database and mobile database because of its independence of database vender. This feature is important in order to build efficient mobile business systems because the upcoming mobile business environment has heterogeneous characteristics in which diverse mobile devices, mobile databases, and RDBMS exist. [ABSTRACT FROM AUTHOR]

Ad hoc network is a dynamic multihop wireless network that is established by a group of mobile nodes using a shared wireless channel. The key barrier is routing in ad hoc networks does not scale up as easily as in fixed network. This problem can be effectively tackled by bringing in hierarchical routing schemes in ad hoc networks. Clustering provides a method to build and maintain hierarchical routing scheme in ad hoc networks. This paper proposes a fully distributed cluster-based routing algorithm for mobile ad hoc networks. Non-overlapping clusters are formed using the dynamic cluster creation algorithm. The mobility issues are also handled locally in this routing architecture. The proposed cluster maintenance algorithm dynamically adapts to the topology changes and hence efficiency is not degraded by node mobility. In addition, our analysis shows that cluster-based routing scheme is cost-effective and can also be used for providing quality of service support to ad hoc network. [ABSTRACT FROM AUTHOR]

A data mule represents a mobile device that collects data in a sensor field by physically visiting the nodes in a sensor network. The data mule collects data when it is in the proximity of a sensor node. This can be an alternative to multihop forwarding of data when we can utilize node mobility in a sensor network. To be useful, a data mule approach needs to minimize data delivery latency. In this paper, we first formulate the problem of minimizing the latency in the data mule approach. The data mule scheduling (OMS) problem is a scheduling problem that has both location and time constraints. Then, for the 1D case of the DMS problem, we design an efficient heuristic algorithm that incorporates constraints on the data mule motion dynamics. We provide lower bounds of solutions to evaluate the quality of heuristic solutions. Through numerical experiments, we show that the heuristic algorithm runs fast and yields good solutions that are within 10 percent of the optimal solutions. [ABSTRACT FROM AUTHOR]

Inline reference monitoring is a powerful technique to enforce security policies on untrusted programs. The security-by-contract paradigm proposed by the EU FP6 S3MS project uses policies, monitoring, and monitor inlining to secure third-party applications running on mobile devices. The focus of this paper is on multi-threaded Java bytecode. An important consideration is that inlining should interfere with the client program only when mandated by the security policy. In a multi-threaded setting, however, this requirement turns out to be problematic. Generally, inliners use locks to control access to shared resources such as an embedded monitor state. This will interfere with application program non-determinism due to Java's relaxed memory consistency model, and rule out the transparency property, that all policy-adherent behaviour of an application program is preserved under inlining. In its place we propose a notion of strong conservativity, to formalise the property that the inliner can terminate the client program only when the policy is about to be violated. An example inlining algorithm is given and proved to be strongly conservative. Finally, benchmarks are given for four example applications studied in the S3MS project. [ABSTRACT FROM AUTHOR]

In cellular communication systems, in order for a network to keep track of inactive mobile stations (MSs), each inactive MS has to update its location from time to time, called location registration. To lighten the task of tracking inactive MSs, the network divides its cells into groups, called location areas (LAs) and tracks inactive MSs at the LA level: an inactive MS sends a registration message to the network to update its location only when it travels to a new LA. Obviously, the performance of a location area design depends on network traffic and the mobility of MSs. In the paper, we propose a general Markov mobility model for MSs in cellular networks, provide a procedure to automatically estimate the system parameters according to the network traffic, derive the performance of LA design, and provide a clustering algorithm to optimize LA designs. A numerical example is provided to show the effectiveness of the proposed procedures. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

As it has strong security features, GSM (Global System for Mobile communications) becomes a popular system which is widely used in mobile communication. Hand held devices are not only used for delivering communication facilities, but also they are used in mobile commerce (m-commerce) transactions. As such, security concerns become more and more important when using mobile systems. This paper suggests using Hash algorithm within GSM to protect massage sending and receiving. Five famous Hash algorithms (MD5, SHA1, SHA 384, SHA256,SHA512) were tested with 128 Kbyte files to see which is the best algorithm to be used in mobile devices that supports GSM capabilities, depending on memory usage and power consumption. [ABSTRACT FROM AUTHOR]

The Mobile IP Authentication, Authorization, and Accounting (AAA) framework architecture is designed to protect signaling messages from eavesdropping by malicious attackers. The message exchanges for AAA incur heavy signaling overhead and long network access latency for mobility service. To solve this problem, the most typical approach is to adopt a key caching mechanism so that the authentication can locally be done and so that the signaling overhead can be significantly reduced. However, in the literature, very little work has conducted a thorough analytical study on the proposed key caching scheme. As a result, the statistical behavior of these schemes cannot be well justified. In this paper, we develop an analytical model that describes the key caching behavior in Mobile IP networks. The accuracy of this model is validated by simulations. Based on the performance analysis, we then propose an adaptive algorithm that dynamically adjusts key cache size so that the signaling overhead can be minimized. [ABSTRACT FROM AUTHOR]

As functionality of vehicles increases in complexity, the demand on the in-vehicle networks increases as well. Maxi- mum bus utilization often becomes the communication bottleneck. One way to satisfy the high bandwidth requirement for future vehicles is to use a higher bandwidth bus or multiple buses. However, the use of a higher bandwidth bus increases the cost of the network. Similarly, the use of multiple buses increases the cost as well as the complexity of wiring and network handling. Both options are becoming solutions to high bandwidth demand. An alternative option is the development of a higher layer protocol that uses data-reduction (DR) techniques to reduce the amount of data to be transferred. Its goal is to communicate the same amount of information using less bus bandwidth. It would be acceptable, provided that it does not increase the message latencies significantly so that the safety of the vehicle is not compromised. The cost of the protocol is expected to be marginal because it consists of one-time changes to software. Various DR algorithms are available in the literature, but DR technology has not been introduced in in-vehicle protocol standards. This paper presents a unique DR methodology, along with its comparison with other proposed methodologies. The performance of this new DR algorithm is found to be better than that of the existing DR algorithms for a wide range of signal dynamics. The cost, as well as the impact of this protocol on the end-to-end message latency, has been found to be very marginal. [ABSTRACT FROM AUTHOR]

Clustering in mobile ad hoc network (MANET) play a vital role in improving its basic network performance parameters like routing delay, bandwidth consumption and throughput. One-hop clustering scheme adopts the simple mechanism to make the logical partition of the dynamic network where the network topology changes constantly resulting an unstable clustering. This paper makes a comprehensive survey of some bench-mark one-hop clustering algorithms to understand the research trends in this area. The literature provides the logic of cluster formation for different algorithms in achieving a linked cluster architecture and an intensive simulation survey of their performance on the cluster maintenance aspects such as cluster density, frequency of cluster reelection, frequency of cluster changes by the nodes and the granularity of cluster heads. This paper should facilitate the researchers as well as practitioners in choosing a suitable clustering algorithm on the basis of their formation and maintenance overhead, before any routing scheme is adopted in the mobile ad hoc network. [ABSTRACT FROM AUTHOR]

The frequency assignment problem involves the assignment of discrete frequencies to the transmitters of a radio network, such as a radio broadcasting network. Frequency separation is necessary to avoid interference by other transmitters to the signal received from the wanted transmitter at the reception region. Here, it is of major importance to minimize the interference while at the same time using the spectrum efficiently. In this paper we present two original distributed algorithms implemented on clusters of PCs used to solve the frequency assignment problem in the field of radio broadcasting. The first one is based on the island distributed [1] implementation of our hybrid genetic algorithm [2]. The second one uses a distributed cooperative Tabu Search. Experimental results show that our algorithms, applied to several instances given by TDF-C2R, lead to important time performance improvements. [ABSTRACT FROM AUTHOR]

Vehicle-based sensors can be used for traffic monitoring. These sensors are usually set with long sampling intervals to save communication costs and to avoid network congestion. In this paper, we are interested in understanding the traffic-monitoring performance that we can expect from such vehicle-based mobile sensor networks, despite the incomplete information provided. This is a fundamental problem to be addressed. A performance evaluation has been carried out in Shanghai, China, by utilizing the vehicle-based sensors installed in about 4000 taxies. Two types of traffic status-estimation algorithms, i.e., the link-based and the vehicle-based, are introduced and analyzed. The results show that estimations of the traffic status based on these imperfect data are reasonably accurate. Therefore, the feasibility of such an application is demonstrated. [ABSTRACT FROM AUTHOR]

Mobile P2P (MP2P) network has been widely used in everyday life combined with the wireless technology development. However, most previous works concentrate on the assumption that the mobile peers are identical of their inner properties in compositing a MP2P network. However, in current network environment, heterogeneous devices are widely used; they may have different storage sizes, data transmission rate, processing ability and even security levels. In such kind of MP2P Network environment, how to make data transmission effectively is challenge. In this paper, we concentrate on how to effectively obtain a queried multimedia resource and generate a path for such data transmission on the overlay MP2P network, so as to make the resource more effectively transmit among the heterogeneous peers. A new path generating algorithm called SPF-A* (Super Peer First A*) is devised, and simulation studies are conducted to validate our proposal. [ABSTRACT FROM AUTHOR]

The stationary signal-strength-difference (SSSD)-based positioning technique has been proposed as a cost-effective, low-complexity solution. The positioning accuracy with this technique, however, is limited, as a result of the large error in the distance. In this paper, we contribute a simple and efficient method for the accuracy improvement issues in the distance. Starting from the concept of the Global Positioning System (GPS) pseudorange (PD) equation, a complete set of distance difference (DD) is formulated. In addition, we then correct the error in the distance by going in the set of DD, based on the least-squares (LS) sense. The theoretical model is established and verified via experimental data gathered in an urban environment. Results clearly show that the proposed method performs well when encountering a large error in the distance. On top of this, we investigate the accuracy improvement issues in the location estimation and propose an iterative LS algorithm by using the corrected distances. The positioning accuracy is studied based on the analysis of different location errors, and the effect of geometric dilution of precision (GDOP) is also investigated. The improvement of the positioning accuracy is clearly demonstrated through the experimental data collected at 55 different test points with 25 133 samples, which is outstanding. [ABSTRACT FROM AUTHOR]

Wireless sensor networks (WSNs) are an important tool for monitoring distributed remote environments. As one of the key technologies involved in WSNs, node fault detection is indispensable in most WSN applications. It is well known that the distributed fault detection (DFD) scheme checks out the failed nodes by exchanging data and mutually testing among neighbor nodes in this network., but the fault detection accuracy of a DFD scheme would decrease rapidly when the number of neighbor nodes to be diagnosed is small and the node's failure ratio is high. In this paper, an improved DFD scheme is proposed by defining new detection criteria. Simulation results demonstrate that the improved DFD scheme performs well in the above situation and can increase the fault detection accuracy greatly. [ABSTRACT FROM AUTHOR]

Abstract-This paper proposes a dynamic resource-allocation (DRA) algorithm for packet data services in wireless communication systems based on Hopfield neural networks (HNNs). The resource-allocation algorithm assumes a delay-centric approach in that it maximizes resource utilization of the overall system while minimizing the packet delay. The real-time (RT) working capability of HNN hardware implementation means that a very powerful scheduling DRA algorithm can be obtained. A generic formulation of the algorithm is presented to establish the optimal bit rate allocation. In addition, some illustrative examples of this formulation are given, considering specific wireless communication systems, such as General Packet Radio Service (GPRS) or Universal Mobile Telecommunications System (UMTS). lo be more precise, the performance of the proposed DRA algorithm is evaluated in a realistic UMTS scenario, considering both RT and nonreal-time (NRT) services. To obtain the best resource distribution and fulfill the different quality-of-service (QoS) levels required by RT and NRT services, the new HNN-based delay-centric DRA algorithm is performed twice. Initially, only the RT services are considered, and following this, all the NRT services are taken into account. The results reveal that the proposed DRA algorithm outperforms other reference algorithms in terms of not only average packet delay but the allocated total bit rate as well. [ABSTRACT FROM AUTHOR]

In this paper, based on a distributed particle filter, two tracking algorithms are proposed for tracking mobile targets in cluster-based underwater sensor networks (USNs). Both tracking algorithms run local particle filter sequentially at each cluster along target trajectories, but they adopt different methods of selecting measurements from sensor nodes to balance the information contribution against the cost. Performance metrics are proposed and discussed in terms of tracking performance, communication cost, energy cost, and tracking response time. Simulations are conducted to quantitatively compare the proposed algorithms as well as another tracking algorithm based on extended Kalman filter (EKF). Our results indicate that one tracking algorithm achieves higher tracking accuracy while the other achieves dramatic reduction of communication cost, energy cost, and tracking response time. Furthermore, performance of two tracking algorithms has been studied in terms of detection threshold and sensor density. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Service discovery is indispensable to ad hoc networking where establishing a stand-alone and self-configurable communication environment is the main objective. This paper concentrates on designing a distributed service discovery model for service sharing among diverse mobile devices in mobile ad hoc networks (manets). This model is built on top of the network layer of the TCP/IP stack and benefits from the up-to-date routing information enabled by proactive routing protocols that attempt to keep the information in the routing tables of the mobile nodes current. The designed system is based on storing service descriptions in selected nodes that are searched in accordance to the proposed Minimum Distance Packet Forwarding (MDPF) algorithm. In addition to identifying and analyzing the design parameters of the system, this paper studies the delay and traffic performance using analytical derivations and experimental evaluations based on the ns-2 network simulation software. The system is intended to be used in a collaborative manet environment whereby a mobile node can consume services, share them, or facilitate such sharing by helping other nodes find them. [ABSTRACT FROM AUTHOR]

We present a new 3D mesh codec for mobile devices. Mobile devices have limited resources such as low memory, slow CPU speed, low power, and no floating-point processor. Considering these mobile characteristics, we suggest a new approach: a hybrid of a progressive geometry and a single-rate connectivity coding. By this approach, our algorithm achieves fast visual updates of progressive 3D point clouds on a small screen of a mobile device and later finalizes restoring faces of the mesh without intensive computing. For a progressive geometry coding, an octree is created and coded. For a single-rate connectivity coding, a new distance based algorithm is introduced. Our algorithm uses only fixed-point arithmetic with simple data structures. Our new 3D mesh codec has been tested on a real mobile phone and the statistical and visual results are also presented in this paper. [ABSTRACT FROM AUTHOR]

Historically, Error-Resilient (ER) video transmission and Super-Resolution (SR) image reconstruction techniques have evolved separately. In this paper, we propose a coordinated application of ER and SR to enhance the resolution of image transmitted over mobile ad-hoc networks. In order to combat error propagation, a flexible multiple description coding method based on shifted 3-D SPIHT (3-D Set Partitioning In Hierarchical Trees) algorithm is presented to generate variable independent descriptions (substreams) according to the network condition. And then, a novel unequal error protection strategy based on the priority level is provided to assign a higher level of error protection to more important parts of bitstream. Moreover, a robust SR algorithm is proposed in the presence of different kinds of packet loss rate to enhance the image resolution. Experimental results indicate that the proposed robust resolution-enhancement scheme outperforms the competing methods from the aspects of PSNR (Peak-Signal-to- Noise Ratio) and visual quality under different packet loss rates. [ABSTRACT FROM AUTHOR]

In this paper, adaptive sectoring of a CDMA cellular network is investigated, and the aim is to maximize the uplink capacity by utilizing mobiles' spatial information. One important feature of the algorithm developed is that it does not depend on tracking individual mobile, but rather on the statistics of mobiles. The distribution of mobiles is modeled as a spatial Poisson process, whose rate function quantizes mobile concentration and is inferred with a Bayesian estimator based on the statistics of network traffic. In addition, the time dynamics of the rate function is assumed to evolve according to mobiles' mobility pattern and it is formulated using the Influence model. With the knowledge of mobiles' spatial distribution, the interference and thus the outage probability of different sector partitions of a cell can be computed. The adaptive sectoring problem is formulated as a shortest path problem, where each path corresponds to a particular sector partition, and the partition is weighted by its outage probability. In simulation examples, a hot spot scenario is simulated with the adaptive sectoring mechanism, and it is observed that load balancing between sectors is achieved and which greatly reduces the effect of hot spot. [ABSTRACT FROM AUTHOR]

This paper presents a multimodal approach for a biometrics verification system. It is based on face and hand images captured by a cell phone. The algorithm includes all parts that are required for face and hand verification, such as feature extraction, classification and authentication. To find local facial features, such as eyes, mouth and nose, we apply a point distribution model and active shape models. We use the same system to find distinctive points in hand geometry. The face feature vector is constructed by applying a Gabor filter to the image and extracting the key points found by an active shape model. The palm feature vector contains characteristics of the hand geometry features. A support vector machine (SVM) is applied to verify the identity of the user. One SVM machine is built for each person in the database to distinguish that person from others. To test the algorithm we built our own database containing face and hand images taken by a cell phone camera. The database contains 480 frontal face images and 120 hand images of 30 persons (16 face images and 4 hand images per person). [ABSTRACT FROM AUTHOR]

This paper considers the optimal distributed assignment of rates to elastic users in a broadband multicell code-division multiple-access (CDMA) network with variable rate assignments, which is connected to a traditional wired Internet Protocol (IP) network. We show that by using an optimization framework, it is possible to construct a distributed rate assignment algorithm similar to current congestion control protocols that addresses both media access control and transport layer issues (i.e., addresses both interference and congestion control). Practical implementation of this algorithm, as well as its impact on convergence and performance, is also addressed. [ABSTRACT FROM AUTHOR]

This paper proposes a novel downlink spatial scheduling algorithm in multiuser multiple-input--multiple-output (MIMO) systems, which selects a good combination of terminals and base station's (BS's) transmit beams so that the BS's beams nullify interstream interference at the selected terminals. In the derivation process, we reveal the new property that the optimization problem of downlink spatial scheduling is equivalent to that of uplink scheduling under the BS's zero-forcing beamforming. Using this property, an efficient downlink scheduling algorithm is presented, applying the principle of an uplink scheduling algorithm. Numerical results show that the presented spatial scheduling achieves a much higher system throughput than a multiuser MIMO system without spatial scheduling or with conventional spatial scheduling by linear processing. We also present a realistic control structure to achieve the uplink and downlink spatial scheduling in time-division duplex systems. [ABSTRACT FROM AUTHOR]

This paper proposes a panoramic image mosaic system for mobile devices. The proposed panoramic mosaic system is optimized for mobile devices by integer- programmable algorithms, and is user-friendly designed by 4- directional auto-shot interface. The proposed system consists of image acquisition by auto-shot interface, image transform onto cylindrical mosaic surface, luminance and color compensation, local alignment, image stitching, and blending. The images are automatically captured by the auto-shot interface which senses the user ~ camera motion and takes a picture when the camera motion is matched to the predejIned motion model of images. The captured images are transformed and projected onto a cylindrical mosaic surface. Exposure difference is removed by color compensation, and the projected images are locally aligned by translational motion model. Then, the boundary of overlapped images are determined and synthesized by image stitching and blending. According to the experiments using real mobile devices, the proposed mosaic system shows good performance compared with other mosaic algorithms. Especially, since the proposed mosaic system operates on the usual mobile multimedia in real-time, the users can generate panoramic images easier than the personal computer based algorithms'. [ABSTRACT FROM AUTHOR]

With a small amount of software modification, wireless extension points (EPs), which are now commercially available, can be used to improve the throughput capacity of a wireless local area network (WLAN). An EP is an immobile device that has access to the power supply or is equipped with a high-capacity battery but does not have direct access to the Internet. They wirelessly relay data between the access point and the mobile hosts. In this paper, we investigate the optimal placement of the EPs such that the throughput capacity of an urban rectilineal WLAN can be maximized. Two channel models that are based on the Shannon capacity bound and IEEE 802.11 specifications are studied. We first formulate a solution for the optimal EP placement problem in a general network scenario as a nonlinear programming problem; then, we propose an efficient algorithm that determines the optimal locations of a fixed number of EPs in a rectilineal network. Our results show that, for a wide range of system parameters, the optimally placed EPs can significantly increase the network throughput capacity. Moreover, we study how the number of EPs, transmission power, path loss exponent, channel models, and traffic characteristics affect the optimal EP placement and expected throughput capacity of the network. [ABSTRACT FROM AUTHOR]

In this paper, we present an opportunistic packet scheduling algorithm based on buffer management (OSBM) over the downlink of a packet cellular network. OSBM is a channel-dependent scheduling algorithm with a provable delay bound. It is able to provide differentiated services to both real-time and nonreal-time applications. Particularly, these features of OSBM are achieved through a novel buffer management scheme. Since this buffer management scheme does not involve any complex online computation, OSBM is very efficient and easy to implement in an operational environment. We also present a new analytical approach for performance analysis of opportunistic scheduling in wireless networks based on the proposed concept of effective downlink capacity (EDC). This approach attempts to adapt the service curve tool for deterministic quality-of-service analysis to the wireless environment, and the concept of the EDC serves to bridge the deterministic method and the stochastic nature of the wireless link. Using this approach, the explicit expression of the delay bound of the OSBM algorithm is obtained. Simulation results are presented to demonstrate the effectiveness of the proposed opportunistic scheduling algorithm. [ABSTRACT FROM AUTHOR]

Abstract  The autoconfiguration algorithm of the mobile node addresses is important in the practical usage of most mobile ad hoc networks (MANETs). The passive Duplicate Address Detection (PDAD) protocols can detect address conflicts in a passive manner and thus have very low protocol overhead. However, the blindly random assignment algorithm used in PDAD leads to a high initial conflict probability. In this paper, we propose a novel concept of address agent, based on which arises a novel autoconfiguration approach, to obtain the least address conflict probability. Most features of PDAD are inherited, e.g., address conflicts are still detected in a passive manner based on anomalies in routing protocol traffic. Analysis and simulation show that our algorithm outperforms existing methods. [ABSTRACT FROM AUTHOR]

State-of-the-art vehicles are now being equipped with multiple video channels for video-data transmission from multiple surveillance cameras mounted on the automobile, navigation videos reporting the traffic conditions on the planned route, as well as entertainment-multimedia streaming for passengers watching on rear-seat monitors. Wireless LANs provide a low-cost and flexible infrastructure for these emerging in-vehicle multimedia services aimed at the driver's and passengers' safety, convenience, and entertainment. To enable the successful simultaneous deployment of such applications over in-vehicle wireless networks, we propose delay-sensitive streaming and packet-scheduling algorithms that enable simple, flexible, and efficient adaptation of the video bitstreams to the instantaneously changing video source and wireless-channel characteristics while complying with the a priori negotiated quality-of-service (QoS) parameters for that video service. Our focus is on real-time low-cost solutions for multimedia transmission over in-vehicle wireless networks that are derived based on existing protocols defined by QoS-enabled networks, such as the IEEE 802.11e standard. In addition, the aim of this paper is to couple the proposed solutions with a novel multitrack-hinting method that is proposed as an extension of conventional MP4 hint tracks in order to provide real-time adaptation of multimedia streams to multiple quality levels for different in-vehicle applications, depending on their importance and delay constraints. First, the scheduling constraints for these simultaneous wireless video-streaming sessions are analytically expressed as a function of the negotiated QoS parameters. This is imperative because a video stream received from an in-vehicle road-surveillance camera will have a different set of delay and quality constraints in comparison to that of traffic monitoring received from remote video cameras located on the planned route. Hence, transmission parameters, such as peak data rate, maximum burst size, minimum transmission delay, maximum error rate, etc., will differ for the various video streams. For this reason, new low-complexity packet-scheduling algorithms that can fulfill diverse QoS streaming conditions are proposed and analyzed. The proposed algorithms produce viable schedules (i.e., strictly QoS.compliant) that jointly consider the delay constraints and the in-vehicle video-receiver-buffer conditions. Hence, these scheduling schemes can completely avoid the underflow or overflow event of the receiving-device buffer while guaranteeing the agreement between the real-time video traffic and the predetermined traffic specification reached during QoS negotiation for various in-vehicle video channels. When combined with multitrack hinting, an integrated flexible system for adaptive multimedia streaming over QoS-enabled in-vehicle wireless networks can be constructed. We demonstrate the viability of the proposed scheduling mechanisms experimentally by using real video traces under multiple quality levels, as derived by the multitrack-hinting design. In addition, simulations under realistic conditions are also performed to validate the ability of the method to satisfy buffer-occupancy constraints. [ABSTRACT FROM AUTHOR]

With various wireless technologies developed over the past few years, a ubiquitous and integrated architecture is envisioned for future wireless communication. An important optimization issue in such an integrated system is how to minimize the overall communication cost by intelligently utilizing the avail- able heterogeneous wireless technologies while, at the same time, meeting the quality-of-service requirements of mobile users. In this paper, we first identify the cost-minimization (CM) problem to be NP-hard. We then present an efficient minimum-cost data- delivery algorithm based on linear programming (LP), with various constraints, such as channel bandwidth, link costs, delay budgets, and user mobility, taken into consideration. In case of insufficient bandwidth for communication with the core network, prefetch is employed to fully utilize the wireless-network capacity. If multiple routes are available, a probability-based approach is taken for CM. Extensive simulations are carried out to evaluate the proposed CM scheme. Our results show that the proposed LP approach can effectively reduce the overall communication cost, with small overhead (< 3%) for signaling, computing, and handoff. We expect that minimum-cost data delivery will become imperative for the future heterogeneous wireless networks and the emerging 4G wireless systems. [ABSTRACT FROM AUTHOR]

This paper studies link layer throughput maximisation for mobile ad hoc network routing algorithms. We analyse the transmission rates and take into account the interference effects to propose a theoretical model of throughput maximisation called Throughput Aware Link Selection (TALS). TALS can easily be infused into other routing protocols. Simulations show performances increases when compared with other methods. The results demonstrate that TALS helps to increase network throughput. [ABSTRACT FROM AUTHOR]

Mobile networks have faced rapid increase in the number of mobile users and the solution for supporting the growing population is to reduce the cell sizes and to increase the bandwidth reuse. This will cause the number of location management operations and call deliveries to increase significantly, and result in high signaling overhead. We focus on minimizing this overhead, by efficient Location Area Planning (LAP). In this paper we seek to determine the location areas to achieve the minimization of the registration cost, constrained by the paging cost. For that we propose a simulated annealing algorithm, which is applied on a basic Location Area partition of cells formed by a greedy algorithm. We used our realistic mobile environment simulator to generate input (cell changing and incoming call statistics) for our algorithm, and by comparing the values of the registration cost function we recognized that significant reduction was achieved in the amount of the signaling traffic. [ABSTRACT FROM AUTHOR]

Iterative equalization using optimal multiuser detector and optimal channel decoder in coded CDMA systems improves the bit error rate (BER) performance tremendously. However, given large number of users employed in the system over multipath channels causing significant multiple-access interference (MAI) and intersymbol interference (ISI), the optimal multiuser detector is thus prohibitively complex. Therefore, the sub-optimal detectors such as low- complexity linear and non-linear equalizers have to be considered. In this paper, a novel low- complexity block decision feedback equalizer (DFE) is proposed for the synchronous CDMA system. Based on the conventional block DFE, the new method is developed by computing the reliable extrinsic log-likelihood ratio (LLR) using two consecutive received samples rather than one received sample in the literature. At each iteration, the estimated symbols by the equalizer is then saved as a priori information for next iteration. Simulation results demonstrate that the proposed low-complexity block DFE algorithm offers good performance gain over the conventional block DFE. [ABSTRACT FROM AUTHOR]

Abstract??This paper investigates the power saving mechanism of Universal Mobile Telecommunications System (UMTS). UMTS discontinuous reception (DRX) is exercised between the network and a mobile station (MS) to save the power of the MS. The DRX mechanism is controlled by two parameters: the inactivity timer thresholdtIand the DRX cycletD. Analytic analysis and simulation model are proposed to study the optimaltIandtDselections that maximize the MS power saving under the given mean packet waiting time constraint. We also devise an adaptive algorithm called dynamic DRX (DDRX). This algorithm dynamically adjusts thetIandtDvalues to enhance the performance of UMTS DRX. Our study quantitatively shows how to select the best inactivity timer and DRX cycle values for various traffic patterns. We also show that DDRX nicely captures the user traffic patterns, and always adjusts thetIandtDclose to the optimal values. [ABSTRACT FROM AUTHOR]

Mobile displays use Liquid Crystal Displays (LCDs). Such displays have various problems, such as narrow color gamut and color saturation. We propose an algorithm to solve these problems by using data processing without panel replacement. In general, the subtle problems in color adjustment are skin color conversion and color saturation. The human skin tone is the color that is typically remembered; viewers feel awkward when skin colors are converted to unnatural colors. This paper proposes as a solution a skin protection algorithm that detects human skin colors and protects skin colors from changing. It also introduces adaptive quadratic curves that reproduce natural appearances more vividly without color saturation. In addition, the system does not use field-to-field processing but pixel-to-pixel processing in real time so that the incoming image can be displayed without field flickering. [ABSTRACT FROM AUTHOR]

In this paper, novel connection admission control (CAC) algorithms that take into account the effect of mobility of users both inside and outside the cell in the downlink of third-generation mobile systems are developed. First, the system capacity, including the other-cell interference, subject to feedback between cells is studied. Then, effective bandwidth expressions for calls are obtained as a function of both their location in the cell as well as their class of traffic (i.e., voice versus data). Next, this formulation is used to derive two mobility-aware admission control algorithms, i.e., a priority CAC, where calls are accepted not only upon resource availability, but also through acceptance ratios that reflect their levels of priority, and a squeezing CAC, where elastic calls may be squeezed to a minimum agreed value, giving way to admit more calls in the system and to secure further ongoing mobile users. Using Markovian analysis, several performance measures are obtained, namely the blocking probability, the dropping probability, both intracell and intercell, as well as the overall cell throughput. The authors eventually investigate the performance of our CAC and show how to extend the Erlang capacity bounds, i.e., the set of arrival rates such that the corresponding blocking/dropping probabilities are kept below predetermined thresholds. [ABSTRACT FROM AUTHOR]

In this paper, a distributed power allocation scheme for mobile ad hoc networks in Rayleigh fast fading environments is proposed. With fluctuated SINR, outage probability is introduced as a QoS parameter. An optimization model is formulated to minimize total transmit powers with constraint conditions that outage probability of each link should be satisfied. A closed-form near-optimal solution to the model is presented based on the exploration of power ratio factor at the boundary of system capacity. The solution is implemented in the networks by a distributed power allocation scheme. In terms of the scheme, each link can determine its power ratio factor independently. The inequity problem of the power allocation algorithms in incremental fashion is avoided. Meanwhile the scheme is more time-saving to be implemented than those schemes in iterative manner. By performance evaluation, we verify our analysis on the optimization model and validate a better result of our scheme in comparison with the counterpart. That is, a larger system capacity is admissible by our method. [ABSTRACT FROM AUTHOR]

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 (α, β)-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. [ABSTRACT FROM AUTHOR]

In this paper, an advanced experimental plane-wave-based method (EPWBM) for evaluation of the performance of multiantenna systems is considered. The method enables a statistical antenna evaluation without performing long routes of radio-channel sounder measurements to be carried out separately for each antenna under test. The EPWBM utilizes the joint contribution of the estimated signal spectrum and the simulated or measured complex three-dimensional (3-D) radiation patterns of antennas under test. The proposed method enables more comprehensive antenna evaluation in a shorter time period compared to direct measurements. For validation purposes, the results obtained with the EPWBM are compared with the results of direct radio-channel measurements. The method is shown to be sufficiently accurate for comparing the performance of different antenna configurations. The average difference between the two methods is below 1 dB when estimating the diversity gain of two-element antennas. Further, the maximum difference between the methods in multiple-input multiple-output analysis is below 1 b/s/Hz in estimating mean capacity. [ABSTRACT FROM AUTHOR]

This paper presents efficient dynamic resource allocation schemes with interference mitigation techniques for multimedia services in downlink orthogonal frequency-division multiplexing mobile cellular systems. Performance of the proposed algorithms is evaluated in terms of user quality-of-service and system spectral efficiency. It is shown that the best subcarrier allocation scheme with interference mitigation and macrodiversity techniques gives significant performance gains in terms of system spectral efficiency. Furthermore, sharing the system bandwidth among real-time stream-type voice and bursty data services can support much larger system loads than having a hard division. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new empirical formula for handover rate as a function of base stations separation, standard deviation of shadow fading, path loss exponent, averaging distance, and correlation distance. The handover initiation algorithm is based on averaged signal strength measurements using relative signal strength with hysteresis margin approach. We generate the data through computer simulations for the average number of handovers referred to as handover rate, for the practical range of path loss exponent and standard deviation of shadow fading. The proposed formula provides for a practical design tool to optimize the handover initiation performance under varied propagation environments. [ABSTRACT FROM AUTHOR]

Adequate coverage is very important for sensor networks to fulfill the issued sensing tasks. In many working environments, it is necessary to make use of mobile sensors, which can move to the correct places to provide the required coverage. In this paper, we study the problem of placing mobile sensors to get high coverage. Based on Voronoi diagrams, we design two sets of distributed protocols for controlling the movement of sensors, one favoring communication and one favoring movement. In each set of protocols, we use Voronoi diagrams to detect coverage holes and use one of three algorithms to calculate the target locations of sensors if holes exist. Simulation results show the effectiveness of our protocols and give insight on choosing protocols and calculation algorithms under different application requirements and working conditions. [ABSTRACT FROM AUTHOR]

Routing in large-scale mobile ad hoc networks is challenging because all the nodes are potentially moving. Geographic routing can partially alleviate this problem, as nodes can make local routing decisions based solely on the destinations' geographic coordinates. However, geographic routing still requires an efficient location service, i.e., a distributed database recording the location of every destination node. Devising efficient, scalable, and robust location services has received considerable attention in recent years. The main purpose of this paper is to show that node mobility can be exploited to disseminate destination location information without incurring any communication overhead. We achieve this by letting each node maintain a local database of the time and location of its last encounter with every other node in the network. This database is consulted by packets to obtain estimates of their destination's current location. As a packet travels towards its destination, it is able to successively refine an estimate of the destination's precise location, because node mobility has ‘diffused’ estimates of that location. We define and analyze a very simple algorithm called EASE (Exponential Age Search) and show that in a model where Θ (n) nodes perform independent random walks on a square lattice of size n, the length of the routes computed by EASE are of the same order as the distance between the source and destination even for very large n. Therefore, without disseminating any explicit location information, the length of EASE routes are within a constant factor of routes obtained with perfect information. We discuss refinements of the EASE algorithm and evaluate it through extensive simulations. We discuss general conditions such that the mobility diffusion effect leads to efficient routes without an explicit location service. In practical settings, where these conditions may not always be met, we believe that the mobility diffusion effect can complement existing location services and enhance their robustness and scalability. [ABSTRACT FROM AUTHOR]