Ruay-Shiung Chang - Academia.edu (original) (raw)

Papers by Ruay-Shiung Chang

Wireless Communications and Mobile Computing, 2003

Journal of Internet Technology, 2012

To help solve the problem of uneven energy consumption, we use relay nodes to prolong the lifetim... more To help solve the problem of uneven energy consumption, we use relay nodes to prolong the lifetime of wireless sensor networks (WSNs). Since the energy of sensors may not be consumed evenly, the most important question is how relay nodes should be deployed to prolong the lifetime of WSNs. The solutions are different in singlehop communication mode or multi-hop communication mode. To have better energy-saving WSNs, we deploy relay nodes on regions where the energy is consumed most in both single-hop and multi-hop communication modes. We propose a weight mechanism to help decide the relay node deployment. Our deployment strategy considers uneven traffic problem and biased energy consumption simultaneously. The proposed method leads to a better deployment of relay nodes to help WSNs perform more effectively. Simulation results show the merits of our proposed method.

Wireless Communications and Mobile Computing, 2010

This paper proposes a self-stabilizing distributed algorithm for deploying mobile nodes with load... more This paper proposes a self-stabilizing distributed algorithm for deploying mobile nodes with loaded energy to the stationary nodes by considering the energy those stationary nodes need. The goal is to deploy mobile nodes to appropriate locations for energy supplements such that the network lifetime can be extended. The problem of maximizing the lifetime is NP-hard. Therefore, it is unrealistic to search for an optimal solution in sensor networks. In this paper, we design several simple rules for mobile nodes and stationary nodes separately in order to find a feasible solution. Simple rules are especially suitable and necessary for low computability sensor networks. Our algorithm is simple and distributed. We prove that our method is stable and has good performance. Simulations show its efficiency too.

Lecture Notes in Computer Science

There has been significant effort to build high throughput computing systems out of many distribu... more There has been significant effort to build high throughput computing systems out of many distributed multimedia servers. These systems should accommodate a larger number of servers and should handle the ever-growing user demands. Recently, Grid computing has become one of the promising technologies that can deliver such a system. Among the many problems encountered in building Grid computing systems, resource discovery, overhead reduction, workload balancing and fault tolerance are the most challenging. In this paper, we present a resource discovery and allocation mechanism (RDAM) in a computational Grid system.

2008 3rd International Conference on Communication Systems Software and Middleware and Workshops (COMSWARE '08), 2008

For modern scientific applications such as astrophysics, astronomy, aerography, and biology, a la... more For modern scientific applications such as astrophysics, astronomy, aerography, and biology, a large amount of storage space is required because of the large-scale datasets. Data Grid collects distributed storage resources such as hard disk space across heterogeneous networks to meet such requirements. In data grid environment, data replication service that copies the replicas to proper storage systems increases the reliability of the data access. By means of these replicas, parallel download creates multiple connections from the client side to the replica servers to improve the performance of the data transfer. To adapt the bandwidth-variation and to make the data transferring more efficient, a parallel download scheme which is called EA (Efficient and Adaptive) parallel download is proposed in this paper. The scheme is to re-evaluate all of the replica servers during the download progress and replace the decaying selected servers with better backup servers. According to our experiments in the Unigrid environment, the EA parallel download decreases the completion time by 1.63% to 13.45% in natural Unigrid environment and 6.28% to 30.56% in choreographed Unigrid environment when compared to the Recursive Co-Allocation scheme. It means that the proposed scheme adapts to the dynamic environment nicely and decreases the total download time effectively.

2008 IEEE/ACS International Conference on Computer Systems and Applications, 2008

Data grids deal with a huge amount of data regularly. It is a fundamental challenge to ensure eff... more Data grids deal with a huge amount of data regularly. It is a fundamental challenge to ensure efficient accesses to such widely distributed data sets. Creating replicas to a suitable site by data replication strategy can increase the system performance. It shortens the data access time and reduces bandwidth consumption. In this paper, a dynamic data replication mechanism is proposed, which is called Latest Access Largest Weight (LALW). LALW selects a popular file for replication and calculates a suitable number of copies and grid sites for replication. By setting a different weight for each data access record, the importance of each record is differentiated. The data access records in the nearer past have higher weight. It indicates that these records have higher value of references. In other words, the data access records in the long past have lower reference values. A Grid simulator OptorSim is used to evaluate the performance of this dynamic replication strategy. The simulation results show that LAHW successfully increases the effective network usage. It means that the LALW replication strategy can find out a popular file and replicates it to a suitable site.

Future Generation Information Technology, 2009

Enrollments for computer science have dropped in recent years. Why is the trend? Can we do someth... more Enrollments for computer science have dropped in recent years. Why is the trend? Can we do something to stop it? In this talk, we discuss the issues and propose some research directions with the hope that computer science can be revitalized. Coded as ACGT, we identify four interesting areas for computing. Furthermore, we preach for system openness and a simpler programming environment for small and smart devices.

4th IEEE International Conference on Cloud Computing Technology and Science Proceedings, 2012

ABSTRACT In this research, we propose a performance estimation model based on the queuing theorem... more ABSTRACT In this research, we propose a performance estimation model based on the queuing theorem including execution time and network transmission delay. With the evaluation, the proposed delay model enables a cloud system to perform resource allocation for cloud applications with lower delay and the lowest cost. Both the numerical analyses and simulation results clearly show the enough evidences to validate the proposed model. The findings are also in favor of the applicability of the proposed model for HPC (High-Performance Computing) applications in a distributed computing environment such as cloud systems.

2007 IEEE Wireless Communications and Networking Conference, 2007

In many scenarios, sensor nodes have to rely on a limited supply of energy (using batteries). To ... more In many scenarios, sensor nodes have to rely on a limited supply of energy (using batteries). To support long lifetime of Wireless sensor networks (WSN), an energy-efficient way of operation of the WSN is necessary. In this paper, we propose a new controlled layer deployment (CLD) routing protocol to guarantee coverage and energy efficiency on a sensor network. CLD outperforms PEAS (Probing Environment and Adaptive Sleeping) and the TTDD (Two-Tier Data Dissemination) protocols in that it can guarantee full area coverage and connection. It can also solve the "cascading problem" which reduces the whole network lifetime. Finally, we show the results of the simulation to prove that the new protocol can use fewer sensor nodes for coverage and increase the lifetime as compared to the PEAS protocol.

Telecommunication Systems, 2009

Neither the current TCP protocol nor the standard backoff algorithm of IEEE 802.11 protocol is ab... more Neither the current TCP protocol nor the standard backoff algorithm of IEEE 802.11 protocol is able to distinguish corruption loss from congestion or collision loss. Hence, high transmission errors and a varying latency inherent in wireless channel would have a seriously adverse effect on the performance of TCP. In this paper, we propose a novel and pragmatic cross-layer approach with joint congestion and contention window control scheme to improve the performance of TCP in IEEE 802.11 wireless environments. In addition to theoretical analysis, simulations are conducted to evaluate the proposed scheme. As it turns out, our design indeed provides a more efficient solution for frequent transmission loss and enables TCP to distinguish between congestion loses and transmission errors, thus to take proper remedial actions.

Software: Practice and Experience, 2013

ABSTRACT Cloud computing has become more and more popular nowadays since it possesses various con... more ABSTRACT Cloud computing has become more and more popular nowadays since it possesses various conveniences such as pay as you go, dynamically deployment, and high efficiency. A numbers of cloud computing platforms are now in the market. Apache Hadoop, an open-source platform, is one of these platforms which has been widely used by companies and organizations, because it is free for both research and production. From the perspective of service providers, it is better to see infrastructure running at the lowest possible power consumption and in the same time satisfying the QoS. From the viewpoint of the service clients, it is also the best situation that all functions they desire are running well at the lowest service cost. By putting ourselves in their shoes, in this paper, we propose the event trigger, which provides an automatic event recording mechanism. The event trigger applies the recorded parameters onto an easy-understanding visual graph. By doing so, users will be able to adjust their deployment of hardware resource through a simple and straightforward understanding of their system performance records. Copyright © 2013 John Wiley & Sons, Ltd.

Journal of Intelligent Manufacturing, 2009

Abstract Services in the ubiquitous computing are heterogeneous in nature. To be pervasive, these... more Abstract Services in the ubiquitous computing are heterogeneous in nature. To be pervasive, these services should be defined in terms of their functionality and capabilities rather than the meaningless Universally Unique IDentifiers (UUIDs) or types of services. With that, clients can access the proper service based on semantic requests, rather then a pre-configured profile. In this paper, we study the requirements for semantic query to be feasible in service discovery processes. Current discovery protocols and the concept of ...

International Journal of Wireless Information Networks, 1995

A distributed algorithm for the conflict-free channel allocation in CDMA (code division multiple ... more A distributed algorithm for the conflict-free channel allocation in CDMA (code division multiple access) networks is presented. Dynamic adjustment to topological changes is also considered. Though the schedules produced by our algorithm are not optimal with respect to link schedule length, the algorithm is simple and practical. The link schedule length minimization problem is NP-complete. Here the length of a link schedule is the number of time slots it uses. The algorithm guarantees a bound 2?—1 time slots on the TDMA cycle ...

International Journal of Radio Frequency Identification Technology and Applications, 2013

Radio Frequency Identification (RFID) readers use radio waves to interact with the tagged objects... more Radio Frequency Identification (RFID) readers use radio waves to interact with the tagged objects and continuously transfer the reading data to the middleware. Because of the high error reading rate, RFID readers generate a large amount of duplicate and inaccurate data. In this paper, we propose a filtering model to correct and clean RFID data generated by RFID readers. We group the readers in an RFID system into several clusters according to their deployed locations. In every cluster, the cluster header uses the readings generated by the readers in the cluster and other clusters to assist the data cleaning processing. Our filtering model can not only increase the accurate rate of the reading but also share the heavy work load of the middleware. The experimental results show that our approach is efficient and accurate.

Information Sciences, 2012

When human culture advances, current problems in science and engineering become more complicated ... more When human culture advances, current problems in science and engineering become more complicated and need more computing power to tackle and analyze. A supercomputer is not the only choice for solving complex problems any more as a result of the speed-up of personal computers and networks. Grid technology, which connects a number of personal computer clusters with high speed networks, can achieve the same computing power as a supercomputer does, also with a lower cost. However, grid is a heterogeneous system. Scheduling independent tasks on it is more complicated. In order to utilize the power of grid completely, we need an efficient job scheduling algorithm to assign jobs to resources in a grid. In this paper, we propose an Adaptive Scoring Job Scheduling algorithm (ASJS) for the grid environment. Compared to other methods, it can decrease the completion time of submitted jobs, which may compose of computing-intensive jobs and data-intensive jobs.

Information Sciences, 1993

In this paper, three types of problems for single-step searching weighted graphs are defined. The... more In this paper, three types of problems for single-step searching weighted graphs are defined. They are the summation cost minimization, the bottleneck cost minimization, and a hybrid to minimize the maximum of the summation cost and the bottleneck cost. All three are shown to be NP-hard but polynomially solvable for trees. The bottleneck minimization is shown to be reducible to the summation minimization problem.

Information Processing Letters, 1991

The problem of single step searching a graph is investigated. We show that this problem can be s&... more The problem of single step searching a graph is investigated. We show that this problem can be s&cd by solving the maximum two-independent set problem. Results about solving the single step graph searching problem on special graphs are listed.

Information Processing Letters, 1997

One of the fundamental problems in graph theory is to compute a minimum weight spanning tree. In ... more One of the fundamental problems in graph theory is to compute a minimum weight spanning tree. In this paper, a variant of spanning trees, called the minimum labeling spanning tree, is studied. The purpose is to find a spanning tree that tries to use edges that are as similar as possible. Giving each edge a label, the minimum labeling spanning tree is to find a spanning tree whose edge set consists of the smallest possible number of labels. This problem is shown to be NP-complete even for complete graphs. Two heuristic algorithms ...

IEEE Transactions on Vehicular Technology, 2003

Advances in computer and telecommunication industries have made wireless networks increasingly po... more Advances in computer and telecommunication industries have made wireless networks increasingly popular and ubiquitous. Basically, there are two types of systems for wireless networks. One is base-station (BS) oriented and the other is the ad hoc wireless network. In BS-oriented wireless networks, the mobile hosts communicate with base stations, while in the ad hoc wireless networks, the mobile hosts communicate with one another directly. The BS-oriented wireless network has better performance and is more reliable. However, the ad hoc wireless network topology is more desirable because of its low cost, plug-and-play convenience, and flexibility. Its usage of bandwidth and battery power is more efficient. The disadvantage is that the route and communication connectivity is fairly weak. Any migration by mobile hosts participating in one or more routes could make the route invalid. It incurs a lot of cost in keeping communication among them. Thus, the ad hoc wireless network is only suitable for applications in a small geographical area. In this paper, we propose hybrid wireless network protocols to combine the advantages of BS-oriented and ad hoc wireless networks. We allow two mobile hosts to communicate directly (one-hop direct transmission) or through another mobile host (two-hop direct transmission) within the BS-oriented networks. The hybrid protocols are more flexible, reliable, and have better performance than the traditional wireless network protocols. The simulation results show that two-hop direct-transmission has a lower noncomplete probability. If the communicating parties were always within a two-hop direct-transmission area, the rate of complete communication would improve about 20%.

IEEE Transactions on Vehicular Technology, 2008

Sensing coverage is an important issue in wireless mobile sensor networks. The strategy of how to... more Sensing coverage is an important issue in wireless mobile sensor networks. The strategy of how to deploy sensor nodes in an environment, particularly in an unknown expanse, will affect the utility of the network just like the quality of communication. In this paper, using the concept of molecule spreading from physics, we present an efficient method for sensor deployment, assuming that global information is not available. Our algorithm, i.e., Self-Deployment by Density Control (SDDC), uses density control by each node to concurrently deploy sensor nodes. We make the nodes form clusters to achieve area density balance. The characteristics in SDDC are concurrent multisensor moving, distributed operation, localized calculation, and self-deployment. Simulations show its good performances compared to the incremental self-deployment algorithm.