In order to represent large video collections in the form of key-frame summary on small screen devices, this paper exploits methodology of the visual attention modelling and rapid serial visual presentation. This approach results in an intuitive layout of efficiently generated video summaries. A robust real-time algorithm for key-frame extraction is presented. The system ranks importance of key-frame regions in the final layout by exploiting visual attention modelling. A final layout is created using an optimisation algorithm based on dynamic programming. Algorithm efficiency and robustness are demonstrated by comparing the results with the manually labelled ground truth.

In this paper we investigate the utilization of visual saliency maps for ROI-based video coding of video-telephony applications. Visually salient areas indicated in the saliency map are considered as ROIs. These areas are automatically detected using an algorithm for visual attention (VA) which builds on the bottom-up approach proposed by Itti et al. A top-down channel emulating the visual search for human faces performed by humans has been added, while orientation, intensity and color conspicuity maps are computed within a unified multi-resolution framework based on wavelet subband analysis. Priority encoding, for experimentation purposes, is utilized in a simple manner: Frame areas outside the priority regions are blurred using a smoothing filter and then passed to the video encoder. This leads to better compression of both Intra-coded (I) frames (more DCT coefficients are zeroed in the DCT-quantization step) and Inter coded (P, B) frames (lower prediction error). In more sophisticated approaches, priority encoding could be incorporated by varying the quality factor of the DCT quantization table. Extended experiments concerning both static images as well as low-quality video show the compression efficiency of the proposed method. The comparisons are made against standard JPEG and MPEG-1 encoding respectively.

Live football video is the major content genre in 3G mobile service. In this paper, we introduce a realtime general highlight detection algorithm based on attention analysis. It combines attention-related media modalities into role-based attention curves, namely video director, spectator and commentator, to track viewers' feeling against game content from media data. A series of linear temporal predictors are assumed from video data directly and employed to allocate strong attention changes, which are marked as scroll-back endpoints for mobile video skim. The advantages of our algorithm are that it avoids semantic uncertainty of game highlights and that it requires little training. We evaluated our approach using the test bed with full five games from different content suppliers to prove the robustness.

We approach image compression using an affine symmetric image representation that exploits rotation and scaling as well as the translational redundancy present between image blocks. It resembles fractal theory in the sense that a single prototypical block is needed to represent other similar blocks. Finding the optimal prototypes is not a trivial task particularly for a natural image. We propose an efficient technique utilizing independent component analysis that results in near-optimal prototypical blocks. A reliable affine model estimation method based on Gaussian mixture models and modified expectation maximization is presented. For completeness, a parameter entropy coding strategy is suggested that achieves as low as 0.14 bpp. This study provides an interesting approach to image compression although the reconstruction quality is slightly below that of some other methods. However the high frequency details are well-preserved at low bitrates, making the technique potentially useful in low bandwidth mobile applications.

The DVB-H standard allows broadcasting of audio and video content to mobile terminals that have to face strict requirements concerning computational load and power consumption. Given the already intensive effort required by the decoding of the H.264/AVC video data stream, it is important to implement low complexity strategies for the concealment of the data losses. They are likely to happen, given the error prone nature of the wireless environment. The aim is to provide an acceptable video quality to the final user, without strongly affecting the resources available to the mobile device.

In [1] we introduced a new real-time variable frame rate control scheme. It is based on the video jerkiness and it can be applied to both coding and transcoding. This scheme constantly traces the motion of the incoming video and automatically tunes the outgoing frame rate according to the level of jerkiness acceptable by the user. This scheme has been conceived in the framework of mobile communications, which calls for an optimum use of both the available bandwidth and terminal resources. In this paper we present a subjective assessment of our solution carried out in a professional laboratory suitably equipped. Towards this aim a group of non-expert users was asked to express their preference when watching side by side the same video coded at variable frame rate and at fixed frame rate. Results show that most of the times a variable frame rate control based on a dynamic bit/frame allocation scheme may substantially improve the video quality perceived by the users.

One of the main goals of watermarking is to optimize capacity while preserving high video fidelity. The perceptual adjustment of the watermark is mainly based on Watson Just Noticeable Difference (JND) model. Recently, it was proposed to improve Watson model using the classification blocks inherent to the encoder in a compressed stream. Although, the new model outperforms the previous one, especially in increasing the watermark power in textured blocks, it still underestimates JNDs at block's edges. This work presents a detailed comparison of these two models and proposes a new method that exploits the good characteristics of the two available models. In addition, experimental results on perceptibility are reported.

In this paper, we present a novel framework that serves adaptive sports video to mobile users. Our framework combines content-based sports highlights extraction and quality-domain video compression technologies in video server, capable of reducing wireless bandwidth consumption more effectively. We develop a robust replay-based highlights extraction method, and propose a content-based video streaming coding scheme to handle the problems of bandwidth and capacity of computation. To validate the practicality and effectiveness of our system, we conduct the experiments on several real soccer videos. The experimental results demonstrate the robustness of our highlights extraction method and more than 77.5% of the bandwidth consumption could be reduced.

Rate-Distortion Optimization (RDO) is a new feature of JVT H.264/AVC video encoder that enables a substantial enhanced efficiency with respect to all previous video coding standards. However, RDO causes a considerable increase in encoding computational complexity, proportional to the square of the search window size when the Full-Search motion estimation algorithm is applied. In this paper, a fast block-based predictive-recursive motion estimation algorithm is illustrated in combination with RDO algorithms. Extensive simulations show that, using the proposed algorithms, the time devoted to RDO is significantly reduced while keeping performance extremely close to JVT reference software JM8.6.

The Ultra-wideband (UWB) spread spectrum technology provides a unique platform for (integrated) communication services spanning a wide range of bit rates (from few kbit/s up to hundreds Mbit/s). The acceptance of the UWB technology worldwide is mainly related to coexistence issues with other existing narrowband and wideband systems sharing the spectrum with UWB. In this paper, we present a proposal for a "detect and avoid" (DAA) procedure that UWB devices would use to mitigate interference to indoor broadband wireless communications services and ensure that the appropriate protection criteria are met. We analyze the performance of an UWB system when the proposed procedure is applied. We assess the UWB system throughput and the time actually available to UWB for transmitting. We analyze the dependence of the UWB system performance on the DAA procedure parameters and on the characteristics of the victim system.

Recent research results indicate that cognitive processes are related to emotions. Since emotions are omnipresent in any kind of interaction it can be advantageous to take them into account, particularly in the context of e-learning. Emotions are now seen as closely related to cognition processes including decision-making, memory, attention, etc. Thus, e-learning environments have begun to take into consideration the emotional state of the learner in order to enhance his performance. This paper presents a tool for man-machine interaction which uses facial input. We believe that facial interaction will have its place among the interaction techniques in the near future. Our work concerns the improvement of computer based learning by mean of a lifelike presence in learning environment. Our approach combines Intelligent Tutoring System with research on human emotion in Cognitive Science, Psychology and Communication. According for relations between emotion, cognition and action in contextual learning, we propose an emotional intelligent tutoring system based on multi-agent architecture to design of adaptive distributed collaborative and peer to peer e-learning environments. An emotionally intelligent tutoring system should be able to provide feedback to students, taking into account relevant aspects of the mental state of the student.

Fractal theory gained attention by mathematicians and engineers during the last two decades as a promising technique to obtain compression of signals. Fractals also provides interesting interpolation features that can be used to zoom images or to achieve slow motions of video sequences. This paper proposes a fractal coding technique based on Iterated Function Systems (IFS) to encode color image signals. IFS aim to exploit the redundancy given by the self-similarity always contained in natural images. The novelty of this work is on the use of Earth Mover's Distance (EMD) measure to identify similarities within color images. The results obtained show that the proposed approach allows achieving better quality in the decoded images than a classic fractal coding based on Root Mean Square Error (RMS) measure.

In order to attract customers to a mobile multimedia service, it is important for the service provider which level of Quality-of-Service (QoS) customers find acceptable, respectively appealing, and how perceptual QoS is affected by system level QoS. This paper discusses a mobile service for horse-race betting, which includes the streaming of video clips to 3G phones. Furthermore, an extensive study to evaluate system level and perceptual QoS is covered in detail. The results demonstrate the importance of adapting the video for presentation on small screens. The investigation follows on to discuss the importance of bit and frame data rates and clearly demonstrates that users are sensitive to rate changes, even at very low rates. Finally, the results show that packet loss in the range of three to four percent does not effect the user experience.

Image scrambling is a fundamental task for several applications, from secure digital content transmission to mutual visual authentication. This paper proposes and evaluates several simple techniques with the aim of being efficient in respect to wavelet compression algorithms and fit for mobile applications. Then, the proposed methods are meant to comply with the average structure of wavelet-based coders and require very low computational capacity. Comparative results are provided both for evaluating the scrambling efficacy and the computational complexity.

IEEE 802.11 based WLANs have became popular, but they can only provide best effort services and so they are poorly suitable for multimedia applications. Recently IEEE 802.11e standard has been proposed to support quality of service. The new standard introduces a so-called Hybrid Coordination Function containing two medium access mechanisms: contention-based channel access and controlled channel access. In this paper we propose a novel framework to better support QoS guarantees for multimedia applications. It comprises QoS Manager, Admission Control, Enhanced Scheduler, Predictor and Feedback System. The scheduler adopted supports real-time applications, variable packet sizes and variable bit rate traffic streams. We show that this framework is suitable to be used by applications requesting Application Level Contracts which will be translated in Resource Level Contracts to the scheduler subsystem. The QoS manager component is able to dynamically manage available resources under different load conditions.

With increasing network heterogeneity, adaptive techniques for coding multimedia (and mainly video) signals become mandatory. In this paper we introduce a simple techniques to adapt quantization step size in an open loop transcoder based on a perceptual interpretation of DCT coefficient distribution. Results show that the technique is actually very simple and despite this simplicity, effective in improving the (trans-) coded stream quality.

This paper presents a channel estimation scheme that is designed for time variant propagation channels and it is efficient by means of mean square error (MSE) of channel estimation and tracking and its incorporation in a real MIMO system. Such schemes target in demanding applications with minimum data rates well above the conventional standards under pedestrian level of mobility. The evaluation has been performed over the spatial channel model developed for MIMO simulations according to 802.16e case of 3GPP.25.996. Orthogonality has been applied in space-frequency dimension for both preamble and pilot symbols, as well as for the data symbols, with the application of Alamouti's coding. The estimation scheme is efficient in minimization the processing requirements at the receiver by estimating only the time-varying channel properties, and the presented results refer to MSE of the estimator, as well as to overall performance of the system (BER) in various propagation channels, data rates and FEC modes.

This paper presents the EU project SHARE which is developing a mobile service architecture to support large-scale rescue operations with multimedia communication and information services. The task of planning and controlling large-scale rescue operations requires flexible and robust tools which help the rescue forces to do their search and rescue work with maximum efficiency. Today the main channels of communication are analog radio and paper text forms. The SHARE system introduces an advanced multimedia communication and information system to the highly mobile working environment which supports well established command hierarchies of the rescue organizations. Different operation scenarios for mobile networks using WiMAX, WLAN or UMTS are discussed regarding their usability for large-scale rescue operations.

Joint source-channel turbo decoding is a promising alternative to classical tandem/separate decoding, as the literature has shown in the recent years. It is able at the receiver to jointly use and to benefit both from the redundancy left, or introduced intentionally, by the source code and from the error correcting capabilities of the channel code. This offers great advantages in terms of robustness with particular codecs, at the expense however of a reasonable increase in decoding complexity. We focus in this tutorial presentation on the derivation of such turbo decoders within the factor graph framework and the Sum-Product algorithm, and on theoretical arguments underlining some of the potentials of the joint source-channel turbo decoding concept.

In this paper, we propose a novel Priority-based Distributed flow Admission Control (PDAC) protocol which adds enhancements to the existing Dynamic Source Routing (DSR) protocol in order to provide Quality of Service (QoS) to traffic flows belonging to realtime and multimedia applications in wireless ad hoc networks. PDAC allows a node to establish and/or discard traffic flows based on the global knowledge of traffic flow priority and available throughput together with the local knowledge of prevailing channel conditions, interference neighborhood, and available transmission rate. The PDAC protocol can also operate in 'cross-layer' architecture that encompasses network and MAC layers in order to provide fairness to higher-priority flows, better channel utilization, and effective resource reservation.

This paper evaluates the interference impact of UWB power controlled systems, classified as secondary services, against some narrowband radiosystems, Fixed Wireless Access (FWA), Point-to-Point (PP) and Fixed Satellite Service (FSS), embedded in a square sprawl of randomly distributed UWB devices. This study on the radio-coexistence accounts for various parameters such as the effect of different outdoor radio propagation models, UWB modulation techniques, UWB user bit rate and density, radiation pattern and pointing of victim antennas. We calculate the mean UWB interference level received by the victim receiver to be able to then compare it with the maximum allowed one in accordance with the ITU guidelines (ITU-R F.1094, ITU-R S.1432).

The 4G converged wireless network may benefit by the capability of exploiting location/situation information for more efficient "seamless" integration of heterogeneous radio access networks. In this framework, the paper defines the architecture able to collect the location/situation information, process it and distribute it to the network nodes that will exploit it to successfully implement location/situation aware mobility management mechanisms. Since the architecture is distributed and must interact with different technologies and layers, a multi agent-based middleware has been chosen to implement some components of the proposed communication platform. Moreover, the paper presents a vertical handover decision criterion that combines location/situation information. Challenges and open issues of this new research area are discussed.

In orthogonal frequency division multiplexing (OFDM) systems affected by carrier frequency offsets, the estimation of the frequency offset corresponding to a fractional part of the carrier spacing is a crucial issue. The proper action of the fractional frequency estimator can be strongly affected by the presence of disturbances, like narrowband interference (NBI) signals. In this paper, we derive the data-aided maximum-likelihood (ML) fractional frequency estimator in the presence of (NBI). Based on the ML algorithm which has a high complexity, we propose a number of simplifications to develop a lower complexity algorithm. The susceptibility of the simplified fractional frequency estimator to NBI signals is investigated in an analytical way. The analytical results are verified by means of simulations. Although the simplified estimator turns out to be essentially independent of the bandwidth and the location of interferers, the performance of the estimator is very sensitive to the signal to interference ratio and the number of interferers. In contrast with the simplified estimator, simulation results indicate that the exact ML estimator is essentially independent of the (NBI) signals.

In this work, a novel methodology for radio resource management is considered for multi-rate MC-CDMA WLAN indoor networking. The proposed strategy is based on resource reallocation and rate adaptation depending on the network situation, monitored in terms of achieved QoS by an intelligent access-point (AP). As they access the medium, all users send bit-rate requests on the basis of their application requirements. Then, the AP monitors the QoS in terms of frame-error-rate (FER) and decides a) to reallocate the radio resources (in terms of number of orthogonal subchannels) and b) to reduce the data rate, in order to improve throughput performances for those users penalized by heavy FER. The "rate downshift" process is continued until the FER measured by the AP allows data transfer with an acceptable QoS. The intelligent AP can also issue a "rate upshift" for users previously downshifted, or in presence of explicit requests, when the channel situation improves. Simulation results underline a general improvement of the aggregated throughput deriving from adaptively manage the QoS requirements with respect to the network situation, thus enabling good resource usage with the WLAN cell.

In this paper, we investigate resource management in downlink multi-cell Orthogonal Frequency Division Multiple Access (OFDMA) systems. An efficient and low-complexity subcarrier assignment algorithm as well as power control scheme are proposed to mitigate the co-channel interference (CCI) impact. Based on a new centralized reuse partitioning strategy, our approach aims to minimize the outage probability in the entire system. With this algorithm, adaptive frequency reuse factors are applied according to users' bandwidth requirement and the CCI level they undergo. Transmit power is then adjusted for further improvement of the system capacity and this without increasing the CCI level. Simulation results show that our approach is particularly efficient for services that demand high bit rates.

A mobile ad hoc network (MANET) is a collection of wireless mobile nodes communicating with each other using multi-hop wireless links without any existing network infrastructure or centralized administration. In recent years, a variety of routing protocols targeted specifically at this environment have been developed and some performance simulations are made. However, the related works took the simulation model with a constant network size and a varying pause times or mobility velocities. And these works do not take into account the influence on the protocols when the mobile nodes' pause time is invariable but the network size is changing. On the contrary, This paper considers the problem from a different perspective, using the simulation model with a dynamic network size and an invariable pause time which should be zero under weakest case because a longer pause time of the node may be insignificant for mobile Ad hoc network with frequently and fastly moving nodes. Furthermore, based on the QoS(delay, jitter, throughput, loss ratio), routing load and the connectivity (to our knowledge, we firstly use the jitter and the connectivity as the valued metrics in the simulation of wireless ad hoc network protocols), this paper systematically discuses the performance evaluation and comparison of four typical routing protocols of ad hoc networks with the different simulation model and metrics, and drew more complete and valuable conclusion.

The paper reports on intermediate results of an ongoing R&D project which aims at designing, implementing and evaluating a novel network architecture in order to provide streaming media services in a heterogeneous environment where the subscribers are roaming across different wired/wireless access networks including ADSL, WiFi, 2.5G and 3G cellular and also, in the near future, WiMAX. In such a system, seamless connectivity has to be maintained during all phases of roaming, the quality of the delivered media stream has to be adjusted to the changes of the network characteristics and to the capabilities of a wide variety of devices, and adaptive charging for the content has to be integrated too. An overview of our proposed network architecture is given, its key components such as the methods of media handling on the server and client sides, capability matching considerations, security and payment techniques are outlined, with special emphasis on our NGN-conform, SIP-based vertical handover mechanism.

The integration of heterogeneous access networks into a ubiquitous wireless environment has commenced. However, in contrast with homogeneous networks (e.g., GPRS or UMTS) where there are a lot of handover test-reference scenarios, extensive work has yet to be done for modelling the end-user mobility in heterogeneous wireless networks. This is partially due to the fact that thorough test-case emulations are complex in heterogeneous environments because the scenarios are difficult to put in practice; moreover, the handover algorithms' performances may also depend on the auxiliary mechanisms such as user profiling or decision parameters gathering. Therefore, in order to exclusively assess the vertical handover decision algorithms, we propose and develop a complete methodology and we investigate the associated mechanisms.

This paper addresses an emerging business opportunity for utilising the fixed broadband access line (local loop) as a public resource. The approach foresees WiFi as an access for both private and public users with wireless gateways to the fixed network installed in private residences, business premises and telephone kiosks. By such means, authorized public users will be given access to the local loop infrastructure (ADSL, VDSL and Fibre) for mobile services including voice and broadband. A business case is outlined in this paper and several models utilising diverse market players are briefly described.

Open Broadband Access Networks are an innovative approach to establish high capacity mobile networks, whereby private Wireless Local Area Networks and associated access lines are made available for public use. In this vision, public mobile users share privately owned resources supported by appropriate handover. Where several handover possibilities present themselves, a judicious choice can help meet service quality constraints and distribute traffic load in an equitable manner.

Recently, a multi-hop wireless LAN system that APs (Access Point) are connected by ad-hoc network technology each other without the need for any cable, is introduced to expand the coverage easily. And some WISPs (Wireless Internet Service Providers) announced that they will offer a public wireless LAN service in partnership with a company providing the physical wireless infrastructure. To realize that service, the VLAN technology is very useful. So we proposed VLAN over multi-hop wireless LAN system, VLAN information exchange protocol and developed the prototype system.

In wireless sensor networks, the power of energy- constrained sensor nodes is largely drained by data communication tasks. Designing energy-efficient data communication mechanisms is, therefore, a major key to maximizing the life-time of wireless sensor networks. This challenge is magnified for visual sensor networks, where the collected and transmitted data is often very large and composed of multiple signals (Infrared signals, audio, video, ...) which have different and varying quality of service requirements (QoS). Motivated by this challenge, we investigate a forward error correction recovery mechanism for multi-path data transmission in wireless sensor networks. Based on this mechanism, we propose a fast algorithm for the trade-off between the end-to-end energy cost and reliability requirement of multi-path data transmission. Under the practical considerations of a fixed transmission power and a realistic modulation scheme, we derive the reliability and expected energy cost metrics of transmission paths. We then demonstrate the efficiency of our algorithm through simulations and discuss future work.

A camera sensor network is a wireless network of cameras designed for ad-hoc deployment. The camera sensors in such a network need to be properly calibrated by determining their location, orientation, and range. This paper presents Snapshot, an automated calibration protocol that is explicitly designed and optimized for camera sensor networks. Snapshot uses the inherent imaging abilities of the cameras themselves for calibration and can determine the location and orientation of a camera sensor using only four reference points. Our techniques draw upon principles from computer vision, optics, and geometry and are designed to work with low-fidelity, low-power camera sensors that are typical in sensor networks. An experimental evaluation of our prototype implementation shows that Snapshot yields an error of 1-2.5 degrees when determining the camera orientation and 5-10cm when determining the camera location. We show that this is a tolerable error in practice since a Snapshot-calibrated sensor network can track moving objects to within 11cm of their actual locations. Finally, our measurements indicate that Snapshot can calibrate a camera sensor within 20 seconds, enabling it to calibrate a sensor network containing tens of cameras within minutes.

Camera sensors constitute an information rich sensing modality with many potential applications in sensor networks. Their effectiveness in a sensor network setting however greatly relies on their ability to calibrate with respect to each other, and other sensors in the field. This paper examines node localization and camera calibration using the shared field of view of camera pairs. Using a new distributed camera sensor network we compare two approaches from computer vision and propose an algorithm that combines a sparse set of distance measurements with image information to accurately localize nodes in 3D. Our algorithms are evaluated using a network of iMote2 nodes equipped with COTS camera modules. The sensor nodes identify themselves to cameras using modulated LED emissions. Our indoor experiments yielded a 2-7cm error in a 6x6m room. Our outdoor experiments in a 30x30m field resulted in errors 20-80cm, depending on the method used.

In this paper we address three challenges that are present when building and analyzing wireless sensor networks (WSN) as part of ubiquitous computing environment: the need for an in-situ user interface, a data logger, and a power consumption meter. Solutions for the above have been presented using laptops, personal digital assistants (PDA), onboard flash memory chips of limited size (usually 1MB), and laboratory test equipment. All of them have a good utility for the right applications. However, considering a certain variety of WSNs, where size, battery life, and cost are crucial, none of the above solutions is satisfactory. In this paper we present a compact, lightweight, low power, and low cost multimodal sensor module SeeMote that meets the stated challenges, and is compatible with the popular MICAz mote. Our module has the following components: (1) a graphical user interface component that combines a color liquid crystal display (LCD) and 5-way buttons, (2) a power meter component that is reconfigurable for attaching various low-power devices, and (3) a data logger component that is interfaced to a removable secure digital (SD) or multimedia memory card (MMC). The module dimensions are 34times58times12 mm. This paper describes the hardware and software design and experiences while developing and using the device. The device is evaluated by comparing its parameters and functionality to laptop and PDA solutions. We conclude that SeeMote is preferred for certain WSNs, such as very large scale, difficult to reach, and wearable WSNs. We also present several applications that use the LCD module, such as the portable frequency spectrum analyzer and remote sensory data display device.

Sensor Webs are heterogeneous collections of sensor devices that collect information and interact with the environment. They consist of wireless sensor networks that are ensembles of small, smart, and cheap sensing and computing devices that permeate the environment as well as high-bandwidth rich sensors such as satellite imaging systems, meteorological stations, air quality stations, and security cameras. Emergency response, homeland security, and many other applications have a very real need to interconnect such diverse networks and access information in real-time. While Internet protocols and Web standards provide well-developed mechanisms for accessing this information, linking such mechanisms with resource-constrained sensor networks is very challenging because of the volatility of the communication links. This paper presents a service-oriented programming model for sensor networks which permits discovery and access of Web services. Sensor network applications are realized as graphs of modular and autonomous services with well-defined interfaces that allow them to be described, published, discovered, and invoked over the network providing a convenient way for integrating services from heterogeneous sensor systems. Our approach provides dynamic discovery, composition, and binding of services based on an efficient localized constraint satisfaction algorithm that can be used for developing ambient-aware applications that adapt to changes in the environment. A tracking application that employs many inexpensive sensor nodes, as well as a Web service, is used to illustrate the approach. Our results demonstrate the feasibility of ambient-aware applications that interconnect wireless sensor networks and Web services.

In this paper, we study coverage with connectivity properties in large wireless sensor networks. We consider three classes: full coverage with connectivity, partial coverage with connectivity, and constrained coverage with connectivity. We outline two simple network topologies to satisfy the constrained coverage with connectivity criterion. We compare the surveillance performance and deployment cost for networks with different coverage with connectivity criteria. Together, they cover a whole spectrum of surveillance quality in wireless sensor networks at different cost. We outline potential research topics in the area.

In hierarchical sensor networks, sensor nodes are arranged in clusters, and higher-powered relay nodes can be used as cluster heads. The scalability and the lifetime of sensor networks are affected by the limited transmission range and battery power of the nodes. Proper techniques for assigning sensor nodes to clusters have been shown to improve the lifetime of the network. Previous approaches to clustering focus on different heuristics to achieve load balancing. In this paper, we have proposed two fast and efficient integer linear program (ILP) formulations for assigning sensor nodes to clusters in a two-tiered network, where the relay nodes are used as cluster heads. The first is for single hop routing and the second is a generalized formulation that can be used with any multi-hop routing strategy. The objective, in both cases, is to maximize the lifetime of the relay node network. We have tested our formulations with a number of different routing strategies, and for each case, we have compared our formulation to several existing heuristics for clustering. The results demonstrate that our ILP's consistently outperform the heuristics and are fast enough to be used for practical networks with hundreds of sensor nodes.

Production Grid infrastructure requires end-to- end guarantees on the Quality of Service from the underlying networks. In this paper, we present use cases for advance network resource reservation and then describe a multi-layered architecture that can support them. The architecture presents a single bandwidth broker, called BAR, which sits at the Grid layer. BAR not only provides a single point of access to Grid applications to reserve guaranteed end-to-end bandwidth, but also presents its interface in application terms (instead of networking terms). We expose two guaranteed bandwidth services: the Guaranteed Delivery File Transfer and Virtual Leased Line services. Integrated with the GEANT2 bandwidth on demand infrastructure, our bandwidth broker deals with multiple network domains, further insulating the applications from network concerns. We also define additional components required for an end-to-end reservation as well as the interfaces between the components. Our deployed prototype demonstrated the world's first software-based, inter-domain bandwidth reservations based on Premium IP.

TeraPaths is a DOE MICS/SciDAC-fundedproject conceived to address the needs of the high energy and nuclear physics scientific community for effectively protecting data flows of various levels of priority through modern high-speed networks. TeraPaths is rapidly evolving from a last-mile, LAN QoS provider to a distributed end-to-end network path QoS negotiator through multiple administrative domains. Developed as a web service-based software system, TeraPaths automates the establishment of network paths with QoS guarantees between end sites by configuring their corresponding LANs and requesting MPLS paths through WANs on behalf of end users. The primary mechanism for the creation of such paths is the negotiation and placement of advance reservations across all involved domains. This paper describes the status of the project, our experiences so far, as well as the directions of our continued work.

Lambda Station is an ongoing project of Fermi National Accelerator Laboratory and the California Institute of Technology. The goal of this project is to design, develop and deploy network services for path selection, admission control and flow based forwarding of traffic among data- intensive Grid applications such as are used in High Energy Physics and other communities. Lambda Station deals with the last-mile problem in local area networks, connecting production clusters through a rich array of wide area networks. Selective forwarding of traffic is controlled dynamically at the demand of applications. This paper introduces the motivation of this project, design principles and current status. Integration of Lambda Station client API with the essential Grid middleware such as the dCache/SRM Storage Resource Manager is also described. Finally, the results of applying Lambda Station services to development and production clusters at Fermilab and Caltech over, advanced networks such as DOE's UltraScience Net and NSF's UltraLight is covered.

With the advent of service sensitive applications such as remote controlled experiments, time constrained massive data transfers, and video-conferencing, it has become apparent that there is a need for the setup of dynamically provisioned, quality of service enabled virtual circuits. The ESnet on-demand secure circuits and advance reservation system (OSCARS) is a prototype service enabling advance reservation of guaranteed bandwidth secure virtual circuits. OSCARS operates within the energy sciences network (ESnet), and has provisions for interoperation with other network domains. ESnet is a high-speed network serving thousands of Department of Energy scientists and collaborators worldwide. OSCARS utilizes the Web services model and standards to implement communication with the system and between domains, and for authentication, authorization, and auditing (AAA). The management and operation of end-to-end virtual circuits within the network is done at the layer 3 network level. Multi-protocol label switching (MPLS) and the resource reservation protocol (RSVP) are used to create the virtual circuits or label switched paths (LSP's). quality of service (QoS) is used to provide bandwidth guarantees. This paper describes our experience in implementing OSCARS, collaborations with other bandwidth-reservation projects (including interdomain testing) and future work to be done.

Grid application performance is inherently dependent on the performance and reliability of the underlying network. In a production Grid infrastructure, network performance monitoring (NPM) information is required both for middleware resource-brokering decisions and operational monitoring. A variety of NPM frameworks are available which can provide such information. However, the diverse global nature of the EGEE (Enabling Grids for E-sciencE) fabric means it is impractical to mandate a single monitoring solution. In this paper we propose a broker-based federated architecture for integration of NPM information from a heterogeneous set of monitoring frameworks, which provides simplified access to the frameworks for clients. We also present an overview of the requirements for NPM gathered from EGEE middleware developers and operational monitoring users. Finally, we describe our pilot implementation which has proven the validity of the architecture and demonstrated the first integrated access to backbone and end-to-end data gathered using different monitoring frameworks.

Grid services have tremendously simplified the programming challenges in leveraging large-scale distributed computing. At the same time, the increased level of abstraction reduces the opportunities available to the application for optimizing its performance by monitoring the system. In this paper we introduce a monitoring grid services proxy, which transparently monitors network performance and selects between several replica service providers. This approach provides optimized server selection without any modification to or even awareness of the client application or service providers. We describe how we implement the proxy and monitor the available bandwidth to the service providers using the Wren monitoring toolkit. We present analysis indicating that our monitoring has negligible overhead. Finally, we demonstrate the practicality of our approach by optimizing the server selection for INCOGEN's VIBE, a bioinformatics workflow application that uploads gene sequences for analysis by remote service providers.

This article presents a novel method for evaluating the properties of distances between hosts in a computational grid. Our method allows obtaining several indicators about a given network. We demonstrate why the current monitoring tools are not sufficient in grid environments that lack high level tools taking into account particular constraints for some given applications. We show how this method has been embedded in a grid service, namely the network distance service (NDS). Basically, this service returns the evaluation and characterization of a distance between a given set of sources and destinations. We illustrate the benefit of our approach in terms of accuracy of the returned values. We explain some implementation issues and discuss how the proposed NDS service can be useful to any grid service who needs some accurate evaluation for a decision making process involving such distances.

The nature of grid and distributed computing implies communication between heterogeneous systems over a wide and ever-changing variety of network environments. Often large amounts of data are stored in remote locations and must be transmitted in bulk. It is desirable to have the bulk data transfers be as fast as possible; however, because of the dynamic networks involved, it is often hard to predict what protocol will provide the fastest service for a given situation. In this paper we present XlOPerf, a network protocol testing and evaluation tool. XlOPerf is a command line program written on top of Globus XIO with a simple and well-defined interface to many different protocol implementations. XlOPerf was created to give users a way to quickly and easily experiment with an open-ended set of protocols over real networks to determine which will best suit their needs. We present a brief study of the overhead introduced by XlOPerf and the performance when using a variety of protocols.

The use of a manageable optical network is an important requirement for the new advanced data-intensive grid applications that begin to emerge on the e-Science field. In this paper, we propose an ACO-based algorithm that can provision on-demand and dynamically lightpaths on a grid system. Indeed, the proposed algorithm can schedule jobs by discovering processing and network resources on the grid, assigning the job to a specific system and executing the job. This is achieved with the help of an integrated GMPLS control plane, which allows both resource monitoring and management of networking resources.

Reservation of lightpaths in dynamically switched optical networks facilitates guaranteed bandwidth. However, reservation of bandwidth can often lead to bandwidth fragmentation which significantly reduces system utilization and increases the blocking probability of requests. An interesting approach to mitigating this problem is to induce quasi-flexibility in the user requests. A smart scheduling strategy can then exploit this quasi- flexibility and optimize bandwidth utilization. However, there has to be an incentive for flexibility from the user's perspective as well. In this paper, we explore how the network service provider (NSP) can influence user flexibility by dynamically engineering pricing incentives and by suggesting request realignment to overcome reservation contention. Ultimately, user flexibility will lead to efficient network utilization, reduce the price for the users, and increase the revenue for the NSP.

We introduce a new algorithmic framework for advanced channel reservation in ultra high speed networks, called Graded Channel Reservation (GCR). GCR allows users to specify minimum bandwidth and duration requirements for their connections. GCR returns the highest graded path, selected according to a general, multi-criteria optimization objective. In particular, if the optimization criterion is delay, we prove that GCR returns the earliest time available to establish the connection. The computational complexity is polynomial in the size of the graph and the number of pending requests. We introduce a number of variants to GCR, including one that that provides the capability to switch between different paths during a connection. We present practical methods for minimizing or limiting the number of path switches. Through extensive simulations, we evaluate the performance of GCR and its variants under various topological settings and applications workload. Our results show that, for certain traffic parameters, optimized path selection combined with path switching can reduce the average delay of requests by an order of magnitude and increase the saturation throughput by as much as 50%. I.

Advance reservation is a mechanism to guarantee the availability of resources when they are needed. In the context of LambdaGrid, this mechanism is used to provide data-intensive applications with the needed deterministic network quality of service to transport data between grid instruments, high-performance storage systems, compute clusters and visualization systems. Flexible scheduling affords users greater convenience while also improving resource utilization and acceptance rate. In this paper we propose a flexible advance reservation model (FARM) and describe how to implement this model in the meta-scheduling problem. Then we extend this methodology to the cross-domain lightpath reservation problem by incorporating routing and wavelength assignment algorithms. Next, we present the architecture, implementation and APIs of a coordinated interdomain and intradomain optical control plane called AR-PIN/PDC, which is capable of flexible advance reservations. Our simulation results show that by relaxing the reservation time constraint, the acceptance rate and resource utilization can be improved dramatically. Through simulations, we also analyze the impact of advance reservations on immediate reservations and conclude that both AR and IR requests need admission control algorithms in order to let both types of reservations coexist and use resource properly.