Chih-Ping Chu

Mobile object tracking in wireless sensor networks

Wireless sensor network is an emerging technology that enables remote monitoring objects and environment. This paper proposes a protocol to track a mobile object in a sensor network dynamically. The previous researches almost focus on how to track object accurately and they do not consider the query for mobile sources. Additionally, they need not report the tracking information to user. The work is concentrated on mobile user how to query target tracks and obtain the target position effectively. The mobile user can obtain the tracking object position without broadcast query. The user is moving and approaching the target when he/she knows the targets position. Wireless sensor networks can assist user to detect target as well as keep the movement information of the target. Sensor nodes establish face structure to track the designated target and keep target tracks. The source follows the tracks to approaching target. To chase the object quick and maintain an accurate tracking route, the sensors cooperate together to shorten the route between target and source dynamically. A source can quickly approach a target along a shortened route. Finally, we compare the proposed scheme with three flooding-based query methods. By the simulation results, the proposed protocol has better performance than that of flooding-based query methods.

Gathering-Load-Balanced Tree Protocol for Wireless Sensor Networks

Wireless communications and digital electronics have enabled the development of low-power, low-cost, multifunctional sensors. The functionality of sensor network mainly is the measurement collection. The previous proposed protocols mainly focus on broadcasting tree structure, but it may not be efficient in data gathering. In this paper, we propose novel tree architecture that is a dynamic, adjustable, load-balanced tree in sensor networks to decrease the energy utilization and to prolong the lifetime of sensors. A load-balanced tree can share the forwarding loads between non-leaf nodes. Due to the limit of tree topology, we try to adjust forming a tree that has similar amount of children between non-leaf nodes. When the energy of non-leaf node is lower than a designated threshold, the tree structure can be readjusted to prolong the lifetime of tree. In simulation, we compare our protocol with different adjustment phases and an existed protocol. From the result, our protocol can have better performance than others

A dual-Hamiltonian-path-based multicasting strategy for wormhole-routed star graph interconnection networks

Multicast is an important collective communication operation on multicomputer systems, in which the same message is delivered from a source node to an arbitrary number of destination nodes. The star graph interconnection network has been recognized as an attractive alternative to the popular hypercube network. In this paper, we first address a dual-hamiltonian-path-based routing model with two virtual channels based on two hamiltonian paths (HPs) and a network partitioning strategy for wormhole-routed star graph networks. Then, we propose three efficient multicast routing schemes on basis of such a model. All of the three proposed schemes are proved deadlock-free. The first scheme, network-selection-based dual-path routing, selects subnetworks that are constructed either by the first HP or by the second HP for dual-path routing. The second one, optimum dual-path routing, selects subnetworks with optimum routing path for dual-path routing. The third scheme, two-phase optimum dual-path routing, includes two phases, source-to-relay and relay-to-destination. Finally, experimental results are given to show that our proposed three routing schemes outperform the unicast-based, the HP, and the single-HP-based dual-path routing schemes significantly.

Adjustable convergecast tree protocol for wireless sensor networks

For data-collection applications in sensor networks, it is important to ensure base station receives a complete picture about the monitored area. Convergecast is an important communication pattern commonly used to collect continuous data. The prior broadcast trees are not suitable for convergecast, because convergecast is a reverse broadcast process. We point out the load-balancing problem in the current design of sensor networks. A non-load-balancing tree makes some nodes consume energy faster than others. It is important to design a distributed load-balancing solution due to the lack of global knowledge about the network topology. This paper presents a novel convergecast tree protocol and a distributed adjustment algorithm to attain load balancing and to extend network lifetime. The tree protocol constructs an approximate load-balancing convergecast tree. Additionally, the adjustment algorithm dynamically adjusts tree structure to avoid breaking tree link. The tree adjustment only needs localized information and operations at the sensors. Moreover, the tree adjustment is controlled by a sensors grandparent to avoid loop problem. This study performs extensive simulations, demonstrating that the proposed protocols can effectively increase convergecast throughput.

Defect prevention in software processes

In addition to degrading the quality of software products, software defects also require additional efforts in rewriting software and jeopardize the success of software projects. Software defects should be prevented to reduce the variance of projects and increase the stability of the software process. Factors causing defects vary according to the different attributes of a project, including the experience of the developers, the product complexity, the development tools and the schedule. The most significant challenge for a project manager is to identify actions that may incur defects before the action is performed. Actions performed in different projects may yield different results, which are hard to predict in advance. To alleviate this problem, this study proposes an Action-Based Defect Prevention (ABDP) approach, which applies the classification and Feature Subset Selection (FSS) technologies to project data during execution.Accurately predicting actions that cause many defects by mining records of performed actions is a challenging task due to the rarity of such actions. To address this problem, the under-sampling is applied to the data set to increase the precision of predictions for subsequence actions. To demonstrate the efficiency of this approach, it is applied to a business project, revealing that under-sampling with FSS successfully predicts the problematic actions during project execution. The main advantage utilizing ABDP is that the actions likely to produce defects can be predicted prior to their execution. The detected actions not only provide the information to avoid possible defects, but also facilitate the software process improvement.

Service Discovery in Mobile Ad Hoc Networks Based on Grid

Service discovery is a crucial operation for the usability of mobile ad hoc networks (MANETs). Traditional solutions to service discovery that were adopted on the Internet are not well suited for MANETs because of their dynamic nature. This paper presents a novel service discovery protocol based on a hierarchical grid architecture in an ad hoc network. The geographical area of a MANET is divided into a 2-D logical hierarchical grid. The proposed scheme registers the information of available services to a specific location along a predefined trajectory. To enhance resource availability and effective discovery, each grid cell selects a directory for caching available services. This paper utilizes the transmitting trajectory to improve the efficiency of registration and discovery. First, the service provider registers a service along the proposed register trajectory. The requestor then discovers the service along the discovery trajectory to acquire the service information. This paper also proposes an improved process to avoid the sparse node network topology. This paper adopts analysis and simulation to measure the protocol performance. The analytical and simulation results show that the proposed protocol can raise the discovery success ratio and reduce the discovery cost more than the existing geographical service discovery protocol.

The I+ Test

The I test is an efficient and precise data dependence method to ascertain whether integer solutions exist for one-dimensional arrays with constant bounds. For one-dimensional arrays with variable limits, the I test assumes that there may exist integer solutions. In this paper, we propose the I+ test|an extended version of the I test. The I+ test can be applied towards determining whether integer solutions exist for onedimensional arrays with either variable or constant limits, improving the applicable range of the I test. Experiments with benchmark cited from EISPACK, LINPACK, Parallel loops, Livermore loops and Vector loops showed that among 1189 pairs of one-dimensional arrays tested, 183 had their data dependence analysis amended by the I+ test. That is, the I+ test increases the success rate of the I test by approximately 15:4 percent. Comparing with the Power test and the Omega test, the I+ test has higher accuracy than the Power test and shares the same accuracy with the Omega test when determining integer solutions for these 1189 pairs of one-dimensional arrays, but has much better efficiency over them.

Data Aggregation for Range Query in Wireless Sensor Networks

This work proposes efficient data aggregation algorithms based on a virtual grid for range query in wireless sensor networks. A sensor node is selected to be a manager, called head, in each grid. The responsibilities of head are to detect generated event, announce to all other heads, and respond to a moving user. A user obtains the occurred event information from its grid head. If a user is interested in an event, it issues a query to acquire data from a specified regular-shape or spreading irregular-shape ranges. Users can oversee the spreading event via querying the incurred irregular-shape range. In addition, this work proposes efficient approaches to gather data from sensor networks while voids exist. Finally, experimental results show that the proposed approaches are more energy-efficiency than the existing approach.

An on-demand routing protocol with backtracking for mobile ad hoc networks

A mobile ad hoc network (MANET) is characterized by multihop wireless links in the absence of cellular infrastructure and frequent host mobility. In this paper, a new on-demand routing protocol is proposed, named on-demand routing protocol with backtracking (ORB), for multihop mobile ad hoc networks. Suppose a source host wants to deliver a message to a destination in a MANET. First, the source host issues a request to search the destination. When a node receives the request packet, it gets a hop count value which can point the way to the source. This node broadcasts the request packet to its neighbors. When a destination receives this request, it issues a reply back to the source. We proposed a scoped flooding approach which is applied to reply information to the source. This approach will find out multipath from a source to a destination Every node in the MANET maintains some information for this source-destination pair in its own route table. Each node in the forwarding route uses this information to select a group of nodes, named checkpoint nodes, which may have multipath maintained to that destination. The checkpoint node characteristic is such that a route can be recovered instantly without the need for extra control packets. When a delivering node is aware that the forwarding route is broken, it transmits an error packet back to the source along the return path. When a checkpoint receives the error packet that is backtracked to the source, it has backup paths to recover the broken route. This new route can be used immediately The main advantage of our ORB is to reduce the flooding search time and cost when a route has been broken. We show that the proposed scheme outperforms the on-demand routing protocol existing in mobile ad hoc networks.

Multicast communication in wormhole-routed star graph interconnection networks

Multicast, an important communication mechanism, is frequently applied in parallel computing. The star graph interconnection network, when compared with the hypercube network, being with low degree and small diameter, has been recognized to be an attractive alternative to the popular hypercube network. In this paper, we derive a node labeling formula based on a hamiltonian path and propose four efficient multicast routing schemes in wormhole-routed star networks with multidestination routing capability. All of the four proposed schemes are path-based and deadlock-free. The first scheme, dual-path routing, sends the message in parallel through two independent paths (toward high label nodes and low label nodes). The second one, shortcut-node-based dual-path routing, is similar to dual-path routing except that the routing tries to find a shortcut node to route the message as soon as possible to reduce the length of transmission path. The third one, multipath routing, is a multiple dual-path routing strategy that includes source-to-relay and relay-to-destination phases. The last scheme, proximity grouping routing, is similar to multipath routing except that in the partitioning step of source and destination nodes the relation of spatial locality of nodes is also taken into account to reduce the length of transmission paths. Finally, the experimental results are given to show that the performance based on unicast-based and traditional hamiltonian-path routing schemes can be improved significantly by the four proposed routing schemes respectively.