206977606
Priority Based Overlay Multicast for Distributed Interactive Applications
Distributed Interactive Applications (DIAs) is different with other network-based applications, since the data should be delivered to the receiver node according to its priority. Among the existing overlay multicast protocols the "priority-based directed minimum spanning tree" (PST) is designed for DIAs. But in PST the available bandwidth (avail-bw) is used inefficiently and the system becomes unstable when its scale increases. This paper proposed a novel overlay multicast protocol named Priority Based Overlay Multicast (POM), which uses the entities’ priority, links’ delay and node’s avail-bw to build multicast tree. By using POM the nodes with high priority receive the data in short delay, while the nodes with low priority tolerate a long delay in order to balance the available bandwidth usage among the nodes. The simulation results show that POM uses the avail-bw efficiently and keeps the system stable when its scale increases. Keywords: DIAs; Priority; Available bandwidth.
14850996
Effects of network characteristics on task performance in a desktop CVE system
The influences of network characteristics on the task performance in a desktop collaborative virtual environment (CVE) system were studied. In the experiment, two participants worked together to accomplish a collaborative task and a network emulator was utilized to simulate real network characteristics. The task used in the experiment was designed to be highly interactive and had rigid requirements on network characteristics (e.g. latency and packet loss). The objective performance and subjective assessment were recorded and analyzed quantitatively as a function of network latency and packet loss rate. The experiment results show that network latency has no distinct effect on task performance when network latency is less than 200 ms and lightly affect task performance when network latency is between 200 and 600 ms; packet loss has no effect on task performance when there are 40 state update messages received per second and lightly affect task performance when there are between 15 and 40 state update messages received per second.
8895078
An Adaptive-Filtering Policy for Distributed Virtual Environments
In this paper, an adaptive-filtering policy for distributed virtual environments (DVEs) was brought forward. It took advantages of two traditional filtering policies (static-filtering policy and equidistance-transmission policy) and could adaptively select the fittest filtering policy corresponding to current motion characteristic of the virtual object in DVEs. An experiment was designed to compare this filtering policy with the two traditional filtering policies on task performance. Objective (task completion time, state updates transmitted and state updates per second) and subjective (filtering quality) evaluations were recorded in the experiment. The experiment results show that if mean state updates per second is equal or greater than 20 in the task, SUT and SUPS can be decreased by adaptive-filtering policy without task performance affected obviously. However, if mean state updates per second is around 10 in the task, accompanied with SUT and SUPS decreased by adaptive-filtering policy, task performance also deteriorated badly
21143930
An I/O Optimal and Scalable Skyline Query Algorithm
Given a set of d-dimensional points, skyline query returns the points that are not dominated by any other point on all dimensions. Currently, BBS (branch-and-bound skyline) is the most efficient skyline processing method over static data in a centralized setting. Although BBS has some desirable features (e.g., I/O optimal and flexibility), it requires large main-memory consumption. In this paper, we present an improved skyline computation algorithm based on best-first nearest neighbor search, called IBBS, which captures the optimal I/O and less memory space (i.e., IBBS visits and stores only those entries that contribute to the final skyline). Its core enables several effective pruning strategies to discard non-qualifying entries. Extensive experimental evaluations show that IBBS outperforms BBS in both scalability and efficiency for most cases, especially in low dimensions.
17619661
Your way your missions: from location-based to route-based pervasive gaming
In this paper, we describe the design and implementation of a route-based pervasive game named Your Way Your Missions (YWYM). Since the game obtains the planned routes of players and returns missions in the routes, players can play the game in a casual way, without changing their routes to respond to picked up missions. A self-reporting method is proposed to obtain the planned routes of players, and a corresponding route defining tool is developed upon Google Maps. Two approaches to realize route-based mission adaptation with spatial databases are presented.
11794423
An adaptive consistency maintenance approach for replicated continuous applications
Consistency maintenance is a key problem to replicated continuous applications and dead reckoning (DR) algorithm is widely used in this area. In order to eliminate short-term inconsistency caused by DR algorithm, local-lag approach was proposed. For the purpose of simplicity, fixed lag value is used by local-lag approach and the performance of the approach is greatly deteriorated. In this paper, an adaptive consistency maintenance approach, which is based on local-lag approach, is proposed. The new approach can adjust lag value according to the estimated typical network latency. In order to ensure the criterion of consistency correctness, a lag value adjustment method is also proposed. Through two experiments, the performance of the new approach is evaluated and the results indicate that it is feasible and can greatly improve the performance of the application.
18494182
Improving Bluetooth EDR Data Throughput Using FEC and Interleaving
Wireless communication is inherently vulnerable to errors from the dynamic wireless environment. Link layer packets discarded due to these errors impose a serious limitation on the maximum achievable throughput in the wireless channel. To enhance the overall throughput of wireless communication, it is necessary to deploy link layer transmission schemes that is robust to the errors intrinsic to the wireless channel. In this paper, we investigated the impact of three link layer enhancement techniques on the new Enhanced Data Rate (EDR) mode detailed in the new Bluetooth spec v2.0. We first studied the APT algorithm, and used it to obtain the optimal packet type for different bit error rates. We then evaluated FEC/IFEC coding schemes for the new EDR packet types, assessed their ability to alleviate the impact of burst errors, and discussed the tradeoffs. Using analysis and simulation, we show that the performance of the new Bluetooth EDR mode can be significantly improved when FEC and/or IFEC techniques are employed.
6229211
Resource allocation in a middleware for streaming data
Increasingly, a number of applications rely on, or can potentially benefit from, analysis and monitoring of <i>data streams.</i> To support processing of streaming data in a grid environment, we have been developing a middleware system called GATES (Grid-based AdapTive Execution on Streams). Our target applications are those involving high volume data streams and requiring distributed processing of data arising from a distributed set of sources.
 This paper addresses the problem of resource allocation in the GATES system. Though resource discovery and resource allocation have been active topics in grid community, the pipelined processing and real-time constraint required by distributed streaming applications pose new challenges. We present a resource allocation algorithm that is based on minimal spanning trees. We evaluate the algorithm experimentally and demonstrate that it results in configurations that are very close to optimal, and significantly better than most other possible configurations.
44509988
A threshold criterion, auto-detection and its use in MST-based clustering
Clustering is to group data points into homogenous clusters so that data points within the same cluster are more similar than data points belonging to different clusters. There are many effective clustering algorithms for discovering arbitrary shaped clusters, but one common problem of many algorithms is the difficulty for users to decide appropriate parameters for these algorithms. To reduce the dependence of clustering performance on parameters, this paper proposes a threshold criterion for the single linkage cluster analysis and incorporates it into the Minimum Spanning Tree (MST) based clustering method. Since the threshold can be automatically decided according to the underlying data distributions, arbitrary shaped clusters can be discovered with little human intervention. The experimental results on spatial data are very encouraging.
8727184
Estimating Link Capacity in High Speed Networks
Knowledge of bottleneck capacity of an Internet path is critical for efficient network design, management, and usage. With emerging high speed Internet links, most traditional estimation techniques are limited in providing fast and accurate capacity estimations. In this paper, we propose a new technique, called PBProbe, to estimate high speed links. PBProbe is based on CapProbe; however, instead of solely relying on packet pairs, PBProbe employs a “packet bulk” technique and adapts the bulk length in order to overcome the well known problem with packet pair based approaches, namely the lack of accurate timer resolution. As a result, PBProbe not only preserves the simplicity and speed of CapProbe, but it also correctly estimates link capacities within a much larger range. Using analysis, we evaluate PBProbe with various bulk lengths and network configurations. We then perform emulation and Internet experiments to verify the accuracy and speed of PBProbe on high speed links. The results show that PBProbe is consistently fast and accurate in the great majority of test cases.
11672412
Dealing with Node Mobility in Ad Hoc Wireless Network
A Mobile “Ad hoc” wireless NETwork (MANET) is a network established for a special, often extemporaneous service customized to applications. The ad hoc network is typically set up for a limited period of time, in an environment that may change from application to application. As a difference from the Internet where the TCP/IP protocol suite supports a vast range of applications, in the MANET the protocols are tuned to a specific customer and application (eg, send a video stream across the battlefield; find out if there is a fire in the forest; establish a videoconference among several teams engaged in a rescue effort, etc). The customers move and the environment may change dynamically and unpredictably. For the MANET to retain its efficiency, the ad hoc protocols at various layers may need to self-tune to adjust to environment, traffic and mission changes. From these properties emerges the vision of the MANET as an extremely flexible, malleable and yet robust and formidable network architecture. Indeed, an architecture that can be deployed to monitor the habits of birds in their natural habitat, and which, in other circumstances, can be organized to interconnect rescue crews after a Tsunami disaster, or yet can be structured to launch deadly attacks onto unsuspecting enemies.