Showing papers on "Testbed published in 2004"

The Stanford testbed of autonomous rotorcraft for multi agent control (STARMAC)

Abstract: As an alternative to cumbersome aerial vehicles with considerable maintenance requirements and flight envelope restrictions, the X4 flyer is chosen as the basis for the Stanford testbed of autonomous rotorcraft for multi-agent control (STARMAC). This paper outlines the design and development of a miniature autonomous waypoint tracker flight control system, and the creation of a multi-vehicle platform for experimentation and validation of multi-agent control algorithms. This testbed development paves the way for real-world implementation of recent work in the fields of autonomous collision and obstacle avoidance, task assignment formation flight, using both centralized and decentralized techniques.

MAR: a commuter router infrastructure for the mobile Internet

Abstract: We introduce MAR, a commuter mobile access router infrastructure that exploits wireless diversity (e.g. channel diversity, network diversity, and technology diversity) to provide improved data performance for wireless data users. Our system design stems from the observation that rather than choosing a single wireless service provider (e.g. Sprint, AT&T, BT, Vodafone), a single technology (e.g. GPRS, UMTS, CDMA, 802.11), or a single wireless channel, users can obtain significant benefits by using the multiplicity of choices available. MAR is a wireless multi-homed device that can be placed in moving vehicles (e.g. car, bus, train) to enable high-speed data access. MAR dynamically instantiates new channels based on traffic demand, aggregates the bandwidth and dynamically shifts load from poor quality to better quality channels. MAR, thus, provides a faster, more stable, and reliable communication channel to mobile users.We have implemented and tested the MAR system in our testbed which spans the networks of three different cellular providers. Through our experiments we have performed a detailed evaluation to quantify the benefits of MAR for different protocols and applications. For example, even in highly mobile environments, MAR, on average, improves the end-user experience of web-browsing and streaming applications by a factor of 2.8 and 4.4 respectively. Our results show that significant benefits can be obtained by exploiting the diversity in coverage offered by many cellular operators, different technology networks (e.g. GPRS, CDMA), and diverse wireless channels.

Yaksha: a self-tuning controller for managing the performance of 3-tiered Web sites

Abstract: Managing the performance of multiple-tiered Web sites under high client loads is a critical problem with the advent of dynamic content and database-driven servers on the Internet. This paper presents a control-theoretic approach for admission control in multitiered Web sites that both prevents overload and enforces absolute client response times, while still maintaining high throughput under load. We use classical control theoretic techniques to design a proportional integral (PI) controller for admission control of client HTTP requests. In addition, we present a processor-sharing model that is used to make the controller self-tuning, so that no parameter setting is required beyond a target response time. Our controller is implemented as a proxy, called Yaksha, which operates by taking simple external measurements of the client response times. Our design is noninvasive and requires minimal operator intervention. We evaluate our techniques experimentally using a 3-tiered dynamic content Web site as a testbed. Using the industry standard TPC-W client workload generator, we study the performance of the PI admission controller with extensive experiments. We show that the controller effectively bounds the response times of requests for dynamic content while still maintaining high throughput levels, even when the client request rate is many times that of the server's maximum processing rate. We demonstrate the effectiveness of our self-tuning mechanism, showing that it responds and adapts smoothly to changes in the workload.

Ad hoc networking with directional antennas: a complete system solution

Abstract: In this paper, we present UDAAN ("utilizing directional antennas for ad hoc networking"), which is an interacting suite of modular network- and MAC-layer mechanisms for adaptive control of steered or switched antenna systems in an ad hoc network. UDAAN consists of several new mechanisms - a directional power-controlled MAC, neighbor discovery with beamforming, link characterization with directional antennas, proactive routing and forwarding all working cohesively to provide the first complete systems solution. We describe the development of a real-life ad hoc network testbed using UDAAN with switched directional antennas, and we discuss the lessons learned during field trials. High fidelity simulation results, using the same networking code as in the prototype, are also presented. For the range of parameters studied, our results show that UDAAN can produce up to a factor-of-10 improvement in throughput over omni-directional communications.

Turning 802.11 inside-out

Abstract: The past decade has seen communication revolution in the form of cellular telephony as well as the Internet, but much of it has been restricted to the developed world and metro pockets in the developing world. While the use of cellular technologies can cut down on the time to deploy access networks, the cost economics make this non-viable in growing telecom economies. In the Digital Gangetic Plains (DGP) project, we are exploring the use of 802.11 as a long-distance access technology. 802.11 is currently cost-priced due to competitive mass production and hence is attractive for low cost and rapid deployment in rural areas.We have built an extensive testbed in a rural setting consisting of multi-hop directional 802.11 links, the testbed spanning up to 80km at its longest. To our knowledge such a long-distance, multi-hop testbed based on 802.11 is unique thus far. While 802.11 is attractive in terms of cost economics, it was inherently designed for indoor use. Our novel use of the technology for outdoor, long-distance access links presents several challenges. Our experience with the testbed has brought several research as well as operational issues to the fore. In this paper, we describe the novel technical challenges that lie ahead in using 802.11 to bridge the digital divide.

Flight Demonstrations of Cooperative Control for UAV Teams

Abstract: This paper discusses the development and testing of a unique testbed consisting of a fleet of eight autonomous unmanned aerial vehicles (UAVs) that was designed as a platform for evaluating autonomous coordination and control algorithms. Future UAV teams will have to autonomously demonstrate cooperative behaviors in dynamic and uncertain environments, and this testbed can be used to compare various control approaches to accomplish these coordinated missions. A hierarchical configuration of task assignment, trajectory design, and low-level, waypoint following, are used in a receding horizon framework to control the UAV team. Numerous trajectory optimization and team coordination algorithms have recently been developed to execute these UAV missions. This paper highlights several of these algorithms and presents typical results for representative experiments. These demonstrations of the high-level planning algorithms on scaled vehicles operating in uncertain and dynamic environments represent key steps towards transitioning them to future UAV missions.

Performance issues with vertical handovers - experiences from GPRS cellular and WLAN hot-spots integration

Abstract: Interworking heterogeneous wireless access technologies is an important step towards building the next generation, all-IP wireless access infrastructure. We present an experimental study of inter-network mobility between GPRS Cellular and 802.11b-based WLAN hot-spots, and deeply analyze its impact on active transport TCP flows. Our experiments were conducted over a loosely-coupled, Mobile IPv6-based, GPRS-WLAN experimental testbed. Detailed analysis from packet traces of inter-network (vertical) handovers reveals a number of performance bottlenecks. In particular, the disparity in the round trip time and bandwidth offered by GPRS and WLAN networks, and presence of deep buffers in GPRS, can aggravate performance during vertical handovers. This paper, therefore, summarizes practical experiences and challenges of providing transparent mobility in heterogeneous environments. Based on the observations, we propose a number of network-layer handover optimization techniques, e.g. fast router advertisements (RA), RA caching, binding update (BU) simulcasting and layer-3 based soft handovers that improve performance during vertical handovers. The paper concludes with our experiences of migrating TCP connections, thereby also improving application e.g. FTP, Web performance in this environment.

The Intelligent Home Testbed

Abstract: Intelligent environments are an interesting development and research application problem for multi-agent systems. The functional and spatial distribution of tasks naturally lends itself to a multi-agent model and the existence of shared resources creates interactions over which the agents must coordinate. In the UMASS Intelligent Home project we have designed and implemented a set of distributed autonomous home control agents and deployed them in a simulated home environment. Our focus is primarily on resource coordination, though this project has multiple goals and areas of exploration ranging from the intellectual evaluation of the application as a general MAS testbed to the practical evaluation of our agent building and simulation tools.

Development of a Dynamically Scaled Generic Transport Model Testbed for Flight Research Experiments

Abstract: This paper details the design and development of the Airborne Subscale Transport Aircraft Research (AirSTAR) test-bed at NASA Langley Research Center (LaRC). The aircraft is a 5.5% dynamically scaled, remotely piloted, twin-turbine, swept wing, Generic Transport Model (GTM) which will be used to provide an experimental flight test capability for research experiments pertaining to dynamics modeling and control beyond the normal flight envelope. The unique design challenges arising from the dimensional, weight, dynamic (inertial), and actuator scaling requirements necessitated by the research community are described along with the specific telemetry and control issues associated with a remotely piloted subscale research aircraft. Development of the necessary operational infrastructure, including operational and safety procedures, test site identification, and research pilots is also discussed. The GTM is a unique vehicle that provides significant research capacity due to its scaling, data gathering, and control characteristics. By combining data from this testbed with full-scale flight and accident data, wind tunnel data, and simulation results, NASA will advance and validate control upset prevention and recovery technologies for transport aircraft, thereby reducing vehicle loss-of-control accidents resulting from adverse and upset conditions.

Spatial programming using smart messages: design and implementation

Abstract: Spatial programming (SP) is a space-aware programming model for outdoor distributed embedded systems. Central to SP are the concepts of space and spatial reference, which provide applications with a virtual resource naming in networks of embedded systems. A network resource is referenced using its expected physical location and properties. Together with other SP features, such as reference consistency and access timeout, they help programmers cope with highly dynamic network configurations in a network-transparent fashion. We present the SP design and its implementation using smart messages, a lightweight software architecture similar to mobile agents, that we developed for networks of embedded systems. We also describe the implementation and evaluation of a simple SP application over a testbed consisting of HP iPAQs running Linux and equipped with 802.11 cards for wireless communication. The experimental results indicate that SP is a viable programming model for outdoor distributed computing.

Benchmark probes for grid assessment

Abstract: Summary form only given. Like all computing platforms, grids are in need of a suite of benchmarks by which they can be evaluated, compared and characterized. As a first step towards this goal, we have developed a set of probes that exercise basic grid operations with the goal of measuring the performance and the performance variability of basic grid operations, as well as the failure rates of these operations. We present measurement data obtained by running our probes on a grid testbed that spans 5 clusters in 3 institutions. These measurements quantify compute times, network transfer times, and Globus middleware overhead. Our results help provide insight into the stability, robustness, and performance of our testbed, and lead us to make some recommendations for future grid development.

Coordination and control experiments on a multi-vehicle testbed

Abstract: This paper introduces two unique testbeds that have recently been developed to demonstrate the cooperative control of teams of UAVs. The first testbed uses eight rovers and four blimps operated indoors to emulate a team of heterogeneous vehicles performing a combined reconnaissance and strike mission. The second testbed uses eight small aircraft that are flown autonomously using a commercially available autopilot. This combination of testbeds provides platforms for both advanced research and realistic demonstrations. Numerous trajectory optimization and team coordination algorithms have recently been developed to execute these UAV missions. This paper highlights several of these coordination and control algorithms and presents typical results for representative experiments. These demonstrations of the high-level planning algorithms on scaled vehicles operating in uncertain and dynamic environments represent key steps towards transitioning them to future UAV missions.

Medical Images Simulation, Storage, and Processing on the European DataGrid Testbed

Abstract: The European 1ST DataGrid project was a pioneer in identifying the medical imaging field as an application domain that can benefit from Grid technologies. This paper describes how and for which purposes medical imaging applications can be Grid-enabled. Applications that have been deployed on the DataGrid testbed and middleware are described. They relate to medical image manipulation, including image production, secured image storage, and image processing. Results show that Grid technologies are still in their youth to address all issues related to complex medical imaging applications. If the benefit of Grid enabling for some medical applications is clear, there remain opened research and technical issues to develop and integrate all necessary services.

Networked Sensing for Structural Health Monitoring

Abstract: This paper describes an ongoing project investigating embedded networked sensing for structural health monitoring applications. The vision is of many low-power sensor “motes” embedded throughout the structure with a smaller number of nodes that can provide local excitation. The challenge is to develop both the networking algorithms to reliably communicate within the network, and distributed algorithms to monitor the state of the structure. A wireless data acquisition network is described, including the methods of storing and transmitting the data. A damage detection scheme is described that uses extremely low transmission bandwidth, and is shown to be effective in detecting damage in a simulated structure. Finally, a large-scale structural testbed that is being used for this project is described. The outcome of this work-in-progress is expected to be strong recommendations and algorithms for distributed wireless sensor/actuator structural health monitoring networks.

Performance optimizations for wireless wide-area networks: comparative study and experimental evaluation

Abstract: We present a comparative performance study of a wide selection of optimization techniques to enhance application performance in the context of wide-area wireless networks (WWANs). Unlike in traditional wired and wireless IP-based networks, applications running over WWAN cellular environments are significantly affected by the vagaries of the cellular wireless medium. Prior research has proposed and analyzed optimizations at individual layers of the protocol stack. In contrast, we introduce the first detailed experiment-based evaluation and comparison of all such optimization techniques in a commercial WWAN testbed. This paper, therefore, summarizes our experience in implementing and deploying an infrastructure to improve WWAN performance.The goals of this paper are: (1) to perform an accurate benchmark of application performance over such commercially deployed WWAN environments, (2) to implement and characterize the impact of various optimization techniques across different layers of the protocol stack, and (3) to quantify their interdependencies in realistic scenarios. Additionally, we also discuss measurement pitfalls that we experienced and provide guidelines that may be useful for future experimentation in WWAN environments.

Collaborative sensor networking towards real-time acoustical beamforming in free-space and limited reverberance

Abstract: Wireless sensor networks have been attracting increasing research interest given the recent advances in microelectronics, array processing, and wireless networking. Consisting of a large collection of small, wireless, low-cost, integrated sensing, computing and communicating nodes capable of performing various demanding collaborative space-time processing tasks, wireless sensor network technology poses various unique design challenges, particularly for real-time operation. We review the approximate maximum-likelihood (AML) method for source localization and direction-of-arrival (DOA) estimation. Then, we consider the use of least-squares method (LS) method applied to DOA bearing crossings to perform source localization. A novel virtual array model applicable to the AML-DOA estimation method is proposed for reverberant scenarios. Details on the wireless acoustical testbed are given. We consider the use of Compaq iPAQ 3760s, which are handheld, battery-powered device normally meant to be used as personal organizers (PDAs), as sensor nodes. The iPAQ provide a reasonable balance of cost, availability, and functionality. It has a build in StrongARM processor, microphone, codec for acoustic acquisition and processing, and a PCMCIA bus for external IEEE 802.11b wireless cards for radio communication. The iPAQs form a distributed sensor network to perform real-time acoustical beamforming. Computational times and associated real-time processing tasks are described. Field measured results for linear, triangular, and square subarrays in free-space and reverberant scenarios are presented. These results show the effective and robust operation of the proposed algorithms and their implementations on a real-time acoustical wireless testbed.

Vertical handoff performance in heterogeneous networks

Abstract: We study the problem of handoffs in heterogeneous (both wired and wireless) networks. We first present a testbed that integrates multiple network technologies (Ethernet LAN, WiFi and GPRS cellular data network) to provide seamless connectivity to mobile hosts. We then propose a model to analyze the performance of vertical handoffs as well as experimental measures to validate the model. Finally, we discuss the advantages of handoff detection and triggering through link layer mechanisms. An implementation of handoffs? link layer triggering is presented, and its performance is compared with layer-3 handoff triggering.

Performance measurements of a vehicular ad hoc network

Abstract: Within the framework of the FLEETNET project, a real-world ad hoc network testbed was built using cars as mobile nodes. These cars were equipped with computing and communication devices. As ad hoc routing algorithm, position-based forwarding implemented on Linux-based laptops was used, exploiting position information gathered by on-board navigation systems. We report on measurements and experiences with this testbed for static 1-hop and 3-hop scenarios as well as for mobile 3-hop scenarios. Beside the power, loss-rate, throughput and delivery ratio measurements, we present our methodology for conducting experiments with 'real-world' mobile ad hoc networks and discuss problems of beacon-based position-based routing due to radio fluctuations.

Workflow support for complex grid applications: Integrated and portal solutions

Abstract: In this paper we present a workflow solution to support graphically the design, execution, monitoring, and performance visualisation of complex grid applications. The described workflow concept can provide interoperability among different types of legacy applications on heterogeneous computational platforms, such as Condor or Globus based grids. The major design and implementation issues concerning the integration of Condor tools, Mercury grid monitoring infrastructure, PROVE performance visualisation tool, and the new workflow layer of P-GRADE are discussed in two scenarios. The integrated version of P-GRADE represents the thick client concept, while the portal version needs only a thin client and can be accessed by a standard web browser. To illustrate the application of our approach in the grid, an ultra-short range weather prediction system is presented that can be executed in a grid testbed and visualised not only at workflow level but at the level of individual parallel jobs, too.

Diffusion-based path planning in mobile actuator-sensor networks (MAS-net): some preliminary results

Abstract: In this paper we present preliminary results related to path-planning problems when it is known that the quantities of interest in the system are generated via a diffusion process. The use of mobile sensor-actuator networks (MAS-Net) is proposed for such problems. A discussion of such networks is given, followed by a description of the general framework of the problem. Our strategy assumes that a network of mobile sensors can be commanded to collect samples of the distribution of interest. These samples are then used as constraints for a predictive model of the process. The predicted distribution from the model is then used to determine new sampling locations. A 2-D testbed for studying these ideas is described. The testbed includes a network of ten robots operating as a network using Intel Motes. We also present simulation results from our initial partial differential equation model of the diffusion process in the testbed.

Continuous space estimation for WLAN location determination systems

Abstract: WLAN location determination systems add to the value of a wireless network by providing the user location without using any extra hardware. Current systems return the estimated user location from a set of discrete locations in the area of interest, which limits the accuracy of such systems to how far apart the selected points are. In this paper, we present two techniques to estimate the user location in the continuous physical space, namely the center of mass technique and time averaging technique. We test the performance of the two techniques in the context of the Horus WLAN location determination system under two different testbeds. Using the center of mass technique, the performance of the Horus system is enhanced by more than 13% for the first testbed and more than 6% for the second testbed. The time-averaging technique enhances the performance of the Horus system by more than 24% for the first testbed and more than 15% for the second testbed. The techniques are general and can be applied to any of the current WLAN location determination systems to enhance their accuracy. Moreover, the two techniques are independent and can be applied together to further enhance the accuracy of the current WLAN location determination systems

Network mobility and protocol interoperability in ad hoc networks

Abstract: The integration of various network-level functions, including routing, management, and security, is critical to the efficient operation of a mobile ad hoc network. In this article we focus on network mobility (rather than node mobility), implying the movement of entire subnetworks with respect to one another, while individual users initially associated with one such subnetwork may also move to other domains. One example is a battlefield network that includes ships, aircraft, and ground troops. In this "network of networks", subnets (e.g. shipboard networks) may be interconnected via a terrestrial mobile wireless network (e.g., between moving ships). We discuss the design and implementation of a new ad hoc routing protocol, a suite of solutions for policy-based network management, and approaches for key management and deployment of IPsec in a MANET. These solutions, in turn, are integrated with real-time middleware, a secure radio link, and a topology monitoring tool. We briefly describe each component of the solution, and focus on the challenges and approaches to integrating these components into a cohesive system to support network mobility. We evaluate the effectiveness of the system through experiments conducted in a wireless ad hoc testbed.

Towards Highly Adaptive Services for Mobile Computing

Abstract: The heterogeneity of device capabilities, network conditions and user contexts that is associated with mobile computing has emphasized the need for more advanced forms of adaptation of Internet services This paper presents a framework that addresses this issue by managing distributed profile information and adaptation policies, solving possible conflicts by means of an inference engine and prioritization techniques The profile information considered in the framework is very broad, including user preferences, device and network capabilities, and user location and context The framework has been validated by experiments on the efficiency of the proposed conflict resolution mechanism, and by the implementation of the main components of the architecture The paper also illustrates a specific testbed application in the context of proximity marketing

The SPHERES Guest Scientist Program: collaborative science on the ISS

Abstract: The SPHERES Guest Scientist Program (GSP) supports the efforts of geographically distributed researchers at MIT, the U.S. Department of Defense, NASA, and elsewhere, in the development of algorithms for the SPHERES formation-flying and docking testbed. The GSP consists of a test development framework, a robust and flexible interface to the SPHERES flight software, a portable high-fidelity simulation, two laboratory testbeds, and data analysis utilities. The SPHERES testbed will be operated in bi-weekly test sessions on-board the International Space Station. Updates to the flight software can be uploaded immediately prior to each test session, allowing guest scientists the opportunity to revise and improve their algorithms from one session to the next. The SPHERES flight software architecture and the GSP interface design contribute to the flexibility of the testbed, and minimize nonproductive labor by simplifying algorithm implementation.

The formation control testbed

Abstract: Terrestrial planet finder (TPF) is a space telescope mission which performs spectral analysis of the infrared emissions from extrasolar planets, and which searches for carbon-based life on such planets. One configuration being considered for this mission is a stellar interferometer with several collectors and a combiner on separate spacecraft flying in a tightly controlled formation. The distance to earth for this mission are sufficiently great that having ground in the loop for reconfiguration or collision avoidance maneuvers impractical. Moreover, because of constraints in the orientation of the spacecraft relative to the sun, limitations on the field of view of relative range and bearing sensors, and restrictions on the orientations of thrusters, both the attitude and the relative position of each spacecraft in the formation must be taken into account in the event of a temporary sensing or control fault during maneuvers. These maneuvers include initial deployment of the formation, reconfiguration, and collision avoidance maneuvers. The formation algorithms and simulation testbed (FAST) and the formation control testbed (FCT) at JPL are being built to simulate and demonstrate 6 degree of freedom, autonomous formation flying and reconfiguration for TPF. The testbeds are complementary. Control algorithms simulated in the FAST are tested in the FCT in order to validate the FAST. This paper describes the design and construction of the formation control testbed. The FCT consists of three robots navigating on an air bearing floor, propelled by cold gas thrusters. Each robot contains an attitude platform supported on a spherical air bearing which provides three rotational degrees of freedom. The sixth degree of freedom, vertical translation, is provided by a powered vertical stage, actively controlled to provide a simulated zero-g environment for the attitude platform.

Workflow Support for Complex Grid Applications: Integrated and Portal Solutions

Abstract: In this paper we present a workflow solution to support graphically the design, execution, monitoring, and performance visualisation of complex grid applications. The described workflow concept can provide interoperability among different types of legacy applications on heterogeneous computational platforms, such as Condor or Globus based grids. The major design and implementation issues concerning the integration of Condor tools, Mercury grid monitoring infrastructure, PROVE performance visualisation tool, and the new workflow layer of P-GRADE are discussed in two scenarios. The integrated version of P-GRADE represents the thick client concept, while the portal version needs only a thin client and can be accessed by a standard web browser. To illustrate the application of our approach in the grid, an ultra-short range weather prediction system is presented that can be executed in a grid testbed and visualised not only at workflow level but at the level of individual parallel jobs, too.

Unmanned air vehicle testbed for cooperative control experiments

Abstract: This paper describes the MAGICC Lab unmanned air vehicle (UAV) testbed at Brigham Young University. Motivation for pursuing experimental research with UAVs is given as well as a historical perspective of the UAV testbed is developed. Lessons learned through the development and use of the testbed over the past several years are summarized.

Development of a Haptic Backhoe Testbed

Abstract: To my sons, Brannon and Josh iii ACKNOWLEDGEMENTS I am grateful to many people for helping make this project a success. A master's project of this scope and complexity is far beyond the ability of a single person in a time frame of a year or so, and I humbly acknowledge the fact that without a huge amount of help and support from my teammates, colleagues, and family, I could not have gotten so far so fast. helper from the most difficult technical situations to the most mundane tasks. Matt and J.D. brought a wealth of skills to the team, and I am honored to have been able to work with them. I would also like to thank Dr. Wayne Book, for his wisdom, experience, guidance, and support. Without Dr. Book this project could not have possibly begun in the first place. If ever I was veering off down a dead-end path, he pointed me back in the right direction by giving me suggestions or insight that only comes with the extensive knowledge and experience. I am grateful and honored to have been able to work for him. Dave Knight, and Derek Eagles at John Deere for donating the tractor, backhoe, extra parts, and for their technical expertise. Thanks go to Randy Bobbitt at Sauer-Danfoss for helping us pick the right valve, and to Doug Hedrick for donating the valves. Thanks go to Tim Jordan and Mike Bouts at Balluff for donating the position sensors and helping us make the right choice. Thanks go to Bill Steyer and Jim Raspberry at Georgia Hydraulic Cylinders for donating both time and material by making us custom cylinders. Thanks also I would also like to thank my two sons, Brannon and Josh, for patiently waiting for me to finish grad school while living far away from their family. I would also like to thank my iv parents, Sam and Candy, for their encouragement and belief in me. Finally, but certainly not least, I would like to thank my fiancee, Tami, for her love, support, faith, and encouragement. Not only did she encourage me to go to grad school, but in times of frustration and confusion she always seemed able to give me the right boost. I also owe her a debt of gratitude for putting up with my obsession with building the haptic backhoe, from times when I was focused and consumed, to …