9969552
Design of a Service Discovery Architecture for Mobility-Supported Wired and Wireless Networks
Automatic service discovery will play an essential role in future network scenario and is an important component for MANET and collaboration in ubiquitous computing environment. This paper proposes a service discovery architecture, named as SLPA (Service Location Protocol based on AMAAM) in the mobility-supported wired and wireless environment of which the underlying protocol is AMAAM which is an aggregation-based Mobile IP implementation in MANET. In SLPA, the role of the directory agent is assigned to the mobility agent in AMAAM. The mobility agent periodically beacons an advertisement message which contains both the advertisement of the directory agent in SLP and the advertisement of the mobility agent in Mobile IP. For evaluating the functional correctness of SLPA and the overhead of maintaining a service directory in MANET, we simulate SLPA and analyze the overhead of control overheads for the aggregation. Through the simulation experiments, we investigate the functional correctness of the proposed architecture and analyze the control overheads of the aggregation.
2097503
A Web Services-Based Distributed Simulation Architecture for Hierarchical DEVS Models
The Discrete Event Systems Specification (DEVS) formalism specifies a discrete event system in a hierarchical, modular form. This paper presents a web-services-based distributed simulation architecture for DEVS models, named as DEVSCluster-WS. DEVSCluster-WS is actually an enhanced version of DEVSCluster by employing the web services technology, thereby retaining the advantages of the non-hierarchical distributed simulation compared to the previous hierarchical distributed simulations. By employing the web services technologies, it describes models by WSDL and utilizes SOAP and XML for inter-node communication. Due to the standardized nature of the web service technology, DEVSCluster-WS can effectively be embedded in the Internet without adhering to specific vendors and languages. To show the effectiveness of DEVSCluster-WS, we realize it in Visual C++ and SOAPToolkit, and conduct a benchmark simulation for a large-scale logistics system. We compare the performance of DEVSCluster-WS with DEVSCluster-MPI, the MPI-based implementation of DEVSCluster. The performance result shows that the proposed architecture works correctly and could achieve tolerable performance.
8709932
Mapping Cooperating GRID Applications by Affinity for Resource Characteristics
The Computational Grid, distributed and heterogeneous collections of computers in the Internet, has been considered a promising platform for the deployment of various high-performance computing applications. One of the crucial issues in the Grid is how to discover, select and map possible Grid resources in the Internet for meeting given applications. The general problem of statically mapping tasks to nodes has been shown to be NP-complete. In this paper, we propose a mapping algorithm for cooperating Grid applications by the affinity for the resources, named as MACA. The proposed algorithm utilizes the general affinity of Grid applications for certain resource characteristics such as CPU speeds, network bandwidth, and input/output handling capability. To show the effectiveness of the proposed mapping algorithm, we compare the performance of the algorithm with some previous mapping algorithms by simulation. The simulation results show that the algorithm could effectively utilize the affinity of Grid applications and shows good performance.
26299662
A Resilient Multipath Routing Protocol for Wireless Sensor Networks
Wireless sensor networks should be self-configuring, highly scalable, redundant, and robust in dealing with shifting topologies due to node failure and environment changes. The energy of a sensor node is the most important system resource, and one of the best ways of conserving energy is to distribute the routing load across all sensor nodes as much equally as possible. Considering the load balance for conserving energy, multipath routing protocols have been employed in sensor networks. In this paper we present a resilient multipath routing protocol based on AODV, named as RMRP, for wireless sensor networks. RMRP is an AODV-based multipath routing protocol in which sensor nodes setup double routing paths toward sink nodes in an AODV fashion and select one of them randomly for forwarding a packet. RMRP proposes a resilient route maintenance scheme which repairs broken links by utilizing localized information around neighbor nodes of the broken link, thereby reducing the flooding range of control messages. To show the effectiveness of the proposed route maintenance scheme, we evaluate the performance enhancement of the proposed scheme by ns2-based simulation.
26550730
Performance of Service Location Protocols in MANET Based on Reactive Routing Protocols
Automatic service discovery, the problem of discovering service providers by specifying desired properties of services, is an important and necessary component for collaboration in the ubiquitous computing environment such as MANET. This paper investigates the effects of the on-demand route discovery on the performance of service location protocols in MANET based on on-demand routing protocols. We first design a service discovery architecture in MANET based on AODV and evaluate both the distributed and centralized versions of the architecture by simulation. For evaluating the performance, we examine such performance metrics as service hit ratio, service discovery time, and control message overheads. The results show that the distributed scheme outperforms the centralized scheme in most simulation scenarios because of the on-demand routing overheads.
5861630
Mobility Agent Advertisement Mechanism for Supporting Mobile IP in Ad Hoc Networks
Mobile IP has been proposed to solve the problem of how a mobile node may roam from its network and still maintain connectivity to the internet. Another emerging wireless architecture, mobile ad hoc networks (MANET), can be flexibly deployed in most environments without the need for infrastructure base stations. Integrating Mobile IP and MANET will facilitate the current trend of moving to an all-IP wireless environment. In this paper we propose an architecture of integrating Mobile IP and MANET based on the on-demand routing protocols. The proposed architecture employs two agent advertisement mechanisms, Mobility Agent Advertisement Mechanism (MAAM) and Aggregation-based Mobility Agent Advertisement Mechanism (AMAAM). In both mechanisms the mobility agent uses periodic beaconing of agent advertisement messages with on-demand routing protocols. Despite its architectural advantage, MAAM has some performance issues to be tackled because it incurs excessive generation of registration request messages of mobile nodes. AMAAM is an enhancement of MAAM for reducing the overhead of the beaconing by aggregating the reply messages of the agent advertisement. The simulation results show that AMAAM can effectively reduce the overhead of periodic agent advertisement and registration process.
9243298
Analysis of the competition between wired, DSL and wireless users in an access network
This paper analyzes the performance of a large population composed of several classes of long lived TCP flows experiencing packet losses due to random transmission errors and to congestion created by the sharing of a common tail-drop or RED bottleneck router. Each class has a different transmission error rate. This setting is used to analyze the competition between wired and wireless users in an access network, where one class (the wired class) has no or small (like BER in DSL) transmission error losses whereas the other class has higher transmission error losses, or the competition between DSL flows using different coding schemes. We propose a natural and simple model for the joint throughput evolution of several classes of TCP flows under such a mix of losses. Two types of random transmission error losses are considered: one where losses are Poisson and independent of the rate of the flow, and one where the losses are still Poisson but with an intensity that is proportional to the rate of the source. We show that the large population model where the population tends to infinity has a threshold (given in closed form) below which there are no congestion losses at all in steady state, and above which there is a stationary limiting regime in which we can compute both the mean value and the distribution of the rate obtained by each class of flow. We also show that the maximum mean value for the aggregated rate is achieved at the threshold.
7329667
Iterative kernel principal component analysis for image modeling
In recent years, kernel principal component analysis (KPCA) has been suggested for various image processing tasks requiring an image model such as, e.g., denoising or compression. The original form of KPCA, however, can be only applied to strongly restricted image classes due to the limited number of training examples that can be processed. We therefore propose a new iterative method for performing KPCA, the kernel Hebbian algorithm, which iteratively estimates the kernel principal components with only linear order memory complexity. In our experiments, we compute models for complex image classes such as faces and natural images which require a large number of training examples. The resulting image models are tested in single-frame super-resolution and denoising applications. The KPCA model is not specifically tailored to these tasks; in fact, the same model can be used in super-resolution with variable input resolution, or denoising with unknown noise characteristics, in spite of this, both super-resolution and denoising performance are comparable to existing methods.
5959481
Grid services for earthquake science
We describe an information system architecture for the ACES (Asia–Pacific Cooperation for Earthquake Simulation) community. It addresses several key features of the field—simulations at multiple scales that need to be coupled together; real-time and archival observational data, which needs to be analyzed for patterns and linked to the simulations; a variety of important algorithms including partial differential equation solvers, particle dynamics, signal processing and data analysis; a natural three-dimensional space (plus time) setting for both visualization and observations; the linkage of field to real-time events both as an aid to crisis management and to scientific discovery. We also address the need to support education and research for a field whose computational sophistication is rapidly increasing and spans a broad range. The information system assumes that all significant data is defined by an XML layer which could be virtual, but whose existence ensures that all data is object-based and can be accessed and searched in this form. The various capabilities needed by ACES are defined as grid services, which are conformant with emerging standards and implemented with different levels of fidelity and performance appropriate to the application. Grid Services can be composed in a hierarchical fashion to address complex problems. The real-time needs of the field are addressed by high-performance implementation of data transfer and simulation services. Further, the environment is linked to real-time collaboration to support interactions between scientists in geographically distant locations. Copyright © 2002 John Wiley & Sons, Ltd.
6524269
Real-time foreground-background segmentation using codebook model
We present a real-time algorithm for foreground-background segmentation. Sample background values at each pixel are quantized into codebooks which represent a compressed form of background model for a long image sequence. This allows us to capture structural background variation due to periodic-like motion over a long period of time under limited memory. The codebook representation is efficient in memory and speed compared with other background modeling techniques. Our method can handle scenes containing moving backgrounds or illumination variations, and it achieves robust detection for different types of videos. We compared our method with other multimode modeling techniques. In addition to the basic algorithm, two features improving the algorithm are presented-layered modeling/detection and adaptive codebook updating. For performance evaluation, we have applied perturbation detection rate analysis to four background subtraction algorithms and two videos of different types of scenes.
14214328
Efficient construction of variable-stride multibit tries for IP lookup
Srinivasan and Varghese (1999) have proposed the use of multibit tries to represent routing tables used for Internet (IP) address lookups. They propose an O(n /sub */W/sup 2//sub */ k) dynamic programming algorithm to determine the strides for an optimal variable-stride trie that has at most k levels. Here, n is the number of prefixes in the routing table and W is the length of the longest prefix. We improve on this algorithm by providing an alternative dynamic programming formulation. The complexity of our algorithm is O(n/sub */W/sub */k), on real router data sets. This is an improvement by a factor of W over the corresponding algorithm of Srinivasan. Experiments conducted by us indicate that our variable-stride algorithm is between 2 and 17 times as fast for IPv4 routing table data.