9333650
Cooperative Autonomic Management in Dynamic Distributed Systems
The centralized management of large distributed systems is often impractical, particularly when the both the topology and status of the system change dynamically. This paper proposes an approach to application-centric self-management in large distributed systems consisting of a collection of autonomic components that join and leave the system dynamically. Cooperative autonomic components self-organize into a dynamically created overlay network. Through local information sharing with neighbors, each component gains access to global information as needed for optimizing performance of applications. The approach has been validated and evaluated by developing a decentralized autonomic system consisting of multiple autonomic application managers previously developed for the In-VIGO grid-computing system. Using analytical results from complex random network and measurements done in a prototype system, we demonstrate the robustness, self-organization and adaptability of our approach, both theoretically and experimentally.
18032989
On the Use of Virtualization and Service Technologies to Enable Grid-Computing
The In-VIGO approach to Grid-computing relies on the dynamic establishment of virtual grids on which application services are instantiated. In-VIGO was conceived to enable computational science to take place In Virtual Information Grid Organizations. Having its first version deployed on July of 2003, In-VIGO middleware is currently used by scientists from various disciplines, a noteworthy example being the computational nanoelectronics research community (http://www.nanohub.org). All components of an In-VIGO-generated virtual grid – machines, networks, applications and data – are themselves virtual and services are provided for their dynamic creation. This article reviews the In-VIGO approach to Grid-computing and overviews the associated middleware techniques and architectures for virtualizing Grid components, using services for creation of virtual grids and automatically Grid-enabling unmodified applications. The In-VIGO approach to the implementation of virtual networks and virtual application services are discussed as examples of Grid-motivated approaches to resource virtualization and Web-service creation.
12672425
Support for data-intensive, variable-granularity grid applications via distributed file system virtualization - a case study of light scattering spectroscopy
A key challenge faced by large-scale, distributed applications in grid environments is efficient, seamless data management. In particular, for applications that can benefit from access to data at variable granularities, data management can pose additional programming burdens to an application developer. This work presents a case for the use of virtualized distributed file systems as a basis for data management for data-intensive, variable-granularity applications. The approach leverages on-demand transfer mechanisms of existing, de-facto network file system clients and servers that support transfers of partial data sets in an application-transparent fashion, and complement them with user-level performance and functionality enhancements such as caching and encrypted communication channels. The paper uses a nascent application from the medical imaging field (light scattering spectroscopy -LSS) as a motivation for the approach, and as a basis for evaluating its performance. Results from performance experiments that consider the 16-processor parallel execution of LSS analysis and database generation programs show that, in the presence of data locality, a virtualized wide-area distributed file system setup and configured by grid middleware can achieve performance levels close (13% overhead or less) to that of a local disk, and superior (up to 680% speedup) to nonvirtualized distributed file systems.
14530977
Towards Real-Time Distributed Signal Modeling for Brain-Machine Interfaces
New architectures for Brain-Machine Interface communication and control use mixture models for expanding rehabilitation capabilities of disabled patients. Here we present and test a dynamic data-driven (BMI) Brain-Machine Interface architecture that relies on multiple pairs of forward-inverse models to predict, control, and learn the trajectories of a robotic arm in a real-time closed-loop system. A method of window-RLS was used to compute the forward-inverse model pairs in real-time and a model switching mechanism based on reinforcement learning was used to test the ability to map neural activity to elementary behaviors. The architectures were tested with in vivodata and implemented using remote computing resources.
694816
Distributed file system support for virtual machines in grid computing
This paper presents a data management solution which allows fast virtual machine (VM) instantiation and efficient run-time execution to support VMs as execution environments in grid computing. It is based on novel distributed file system virtualization techniques and is unique in that: 1) it provides on-demand access to VM state for unmodified VM monitors; 2) it supports user-level and write-back disk caches, per-application caching policies and middleware-driven consistency models; and 3) it supports the use of meta-data associated with files to expedite data transfers. The paper reports on its performance in a WAN setup using VMware-based VMs. Results show that the solution delivers performance over 30% better than native NFS and can bring application-perceived overheads below 10% relatively to a local disk setup. The solution also allows a VM with 1.6GB virtual disk and 320MB virtual memory to be cloned within 160 seconds when it is first instantiated (and within 25 seconds for subsequent clones).
34003913
Efficient Transmission Schemes for Multiuser MIMO-OFDM Downlink Systems in Time-Varying Channels
The performance of multiuser MIMO-OFDM downlink systems with block diagonalization (BD) depends on the accuracy of the channel state information (CSI) available at the transmitter (CSIT) to a great extent. In time-varying channels, the CSIT is always outdated due to an inherent time delay between the uplink channel estimation and the downlink data transmission in TDD systems. This will lead to drastic degradation in system capacity. In this paper, based on the analysis of the effect of the outdated CSIT on multiuser MIMO- OFDM downlink systems with BD method, two linear processing methods, BD with user selection at the transmitter and total MMSE decoder at the receiver (TBDUS-RTMMSE) and BD at the transmitter and partial MMSE decoder at the receiver (TBD-RPMMSE), are proposed to mitigate the effect. To fulfill them, a new pilot-sending architecture is introduced. Analysis and simulation results show that the two proposed methods can effectively reduce the impairment of the outdated CSIT and improve the system sum capacity in suitable time delay regions of the CSIT.
17402027
WSN03-4: A Novel Semi-Markov Smooth Mobility Model for Mobile Ad Hoc Networks.
Existing random mobility models have their limitations such as speed decay and sharp turn which have been demonstrated by the previous studies. More importantly, mobility models need to mimic the movements that abide by the physical law for accurate analysis and simulations of mobile networks. Therefore, in this paper, we propose a novel mobility model, semi-Markov smooth (SMS) model. Each SMS movement includes three consecutive phases: speed up phase, middle smooth phase, and slow down phase. Thus, the entire motion in the SMS model is smooth and consistent with the moving behaviors in real environment. Through steady state analysis, we demonstrate that SMS model has no average speed decay problem and always maintains a uniform spatial node distribution. The analytical results are validated by extensive simulation experiments. In addition, we compare the simulation results on link lifetime and percentage of node degree with random waypoint model, Gauss-Markov model and the proposed SMS model.
14192061
CoS-based QoS management framework for grid services
In service oriented grid environment, quality of service (QoS) support becomes more and more important. In this paper, we propose a QoS management framework which is based on class of service (CoS) for grid services, called CQEF. By using CoS instead of SLA in grid environment, grid service users and providers will no longer need to negotiate for a complex SLA. This will reduce the overhead effectively. In addition, using CoS means the whole grid service lifecycle has to be changed. We discuss these modifications during different phases of CQEF, including CoS definition, service registration and discovery, service deployment and monitoring. A CoS-based resource management mechanism is also presented to show how to guarantee the resource requirements of arrived requests.
365973
Morphable face reconstruction with multiple images
Efficient 3D face reconstruction is very important for face animation and recognition. The slow speed of the 3D morphable model is due to the texture mapping. To improve the speed, we only use the shape matching to recover the 3D shape and use texture mapping to get the texture. However, only with the shape information, one image is not enough for accurate 3D face reconstruction. So, we propose to use multiple images with the morphable shape model. First, with the feature points given on the multiple images, the 3D coordinates of the feature points are estimate by the pose estimation. Then, frontal and profile 2D morphable shape models are built to estimate the 3D morphable shape model. These two steps works iteratively to improve the result. At last, the texture is extracted from multiple images with the pose estimation from the estimated 3D face. The effectiveness of our method is demonstrated by the experimental results
45777945
Opportunistic channel selection approach under collision probability constraint in cognitive radio systems
In this work, we consider a cognitive radio system with multiple primary channels and one secondary user, and then we introduce a channel-usage pattern model and some basic concepts in this system. Based on this system model and the basic concepts, we propose two opportunistic channel selection algorithms to optimize the throughput of the secondary user: minimum collision rate channel selection algorithm and minimum handoff rate channel selection algorithm. According to the two algorithms, we, respectively, present the channel selection scheme based on minimum collision rate algorithm (CSS-MCRA) and the channel selection scheme based on minimum handoff rate algorithm (CSS-MHRA) under the constraint that the collision probability is bounded below collision tolerable level. Theoretical analysis and simulation results both show that, on one hand, both CSS-MCRA scheme and CSS-MHRA can follow the constraint of collision tolerable level; on the other hand, the performance of CSS-MCRA scheme is better than that of CSS-MHRA scheme if handoff latency is zero or very low, while the performance of CSS-MHRA scheme is better than that of CSS-MCRA scheme if handoff latency is long enough.