Hung-Chi Chu

Sweep Coverage Mechanism for Wireless Sensor Networks with Approximate Patrol Times

The coverage problem is a fundamental and important issue with regard to wireless sensor networks. To reduce the number of sensor nodes, mobile nodes can be used to mitigate the sweep coverage problem. In this paper, a sweep coverage mechanism is proposed to keep the patrol times of mobile nodes approximate to one another. In simulation, various moving speeds and waiting times of mobile nodes are considered. Simulation results attest to the feasibility of the proposed method.

Design and implementation of the push-to-talk service in ad hoc VoIP network

Push-to-talk (PTT) is a walkie-talkie like service which performs an efficient and instant voice over Internet protocol (VoIP) communication in mobile ad hoc network especially for certain circumstances, such as battle field and earthquake or disaster relief. The authors have designed and implemented the PTT mechanism in ad hoc VoIP network. The PTT server and user agent combined with the pseudo session initiation protocol (SIP) server in the implementation provide the PTT service without standalone SIP server support. The authors also conduct the experimental measurements, in terms of delay and packet loss, in the test-bed to demonstrate the realisation of PTT service in ad hoc VoIP network.

A study of motion recognition system using a smart phone

As technology fast progressed, information equipment operating interfaces have changed. Traditional instruction operation has evolved into intuitive operation, providing users a convenient operation experience without the need of learning in advance. At present, several kinds of intuitive user interface systems have been developed in smart phones, such as picture vertical/horizontal automatic sensing switch and smart phone face/back sensing switch. In this paper, we developed a motion recognition system, where a G-sensor inside a smart phone records users motions, and then the motions are identified by the proposed recognition algorithm to realize the intuitive operation function.

Performance of Adaptive Hysteresis Vertical Handoff Scheme for Heterogeneous Mobile Communication Networks

This paper studies the performance of adaptive vertical handoff schemes for overlay WCDMA and wireless LAN (WLAN) heterogeneous networks. Simulation results show that the proposed adaptive hysteresis vertical handoff (AHVH) can increase lots of average data rate than the fixed hysteresis vertical handoff (FHVH) scheme. Moreover, the proposed AHVH scheme can reduce the ping-pong handoff rate as well .

Mobility Management of VoIP Services Using SCTP Handoff Mechanism

Voice over Internet protocol (VoIP) is a prevalent multimedia application nowadays. For mobile nodes (MNs) using VoIP services in wireless networks, the handoff issues need to be taken into account. Stream control transmission protocol (SCTP) is a potential transport layer protocol with multi-homing and multi-streaming functions. Mobile SCTP with dynamic address reconfiguration (DAR) extends SCTP to mobile wireless network. In this paper, we design and implement a handoff mechanism using multi-homing, DAR and partially reliable SCTP (PR-SCTP) of mobile SCTP to transport VoIP applications. The switch from UDP or TCP to SCTP for VoIP transport provides the seamless handoff ability for MNs using real-time applications such as VoIP service. This paper also provides the performance analyses of the proposed scheme on the implemented Linux testbed.

Target Tracking in Wireless Sensor Networks with Guard Nodes

Target tracking is one of important applications in wireless sensor networks, hence target tracking has become a widely studied subject. This study proposes a low-cost target tracking method which can very precisely monitor targets in real time, while complying with to various restrictions of wireless sensor networks. In this study, the movement characteristics and historical information of the target were used for selecting appropriate guard nodes, which were in charge of target positioning and tracking, so as to use energy more efficiently and reach a balance between the tracking quality and energy saving. The simulation result showed that the proposed method has the advantages of real-time monitoring, precise positioning, and energy efficiency.

An Acceleration Feature-Based Gesture Recognition System

With the diversification of the sensing element that was built-in smart mobile device, it has become one of the important devices in peoples daily life. Among these sensors, the accelerometer is the most common sensor that was embedded in smart mobile device. Therefore, this study proposed a gesture recognition algorithm based on the acceleration feature. It utilized the fuzzy control technique to classify different gestures. The proposed gesture recognition system provides a low complexity and high accuracy gesture recognition method. The simulation results show that the proposed method can recognize these gestures that include tilted to the left side, turn to the other side, shaking, and Z-shaped and have the accuracy rate of more than 91%. In future works, the system can be applied in health care systems or smart home applications to provide intuitive manipulation via specific gesture.

Recognition of the Ambulance Siren Sound in Taiwan by the Longest Common Subsequence

This paper proposes a method to recognize the ambulance siren sound in Taiwan. Since the ambulance siren sound is composed by a high frequency and a low frequency signal, the sequence of the frequency change is used to be the feature of the sound. The input sound is divided into frames, and each frame is classified into high frequency or low frequency. The Longest Common Subsequence (LCS) is used to compare the arrangement of the frequencies in the frames. We use the results of LCS to recognize whether the sound comes from an ambulance. Real sounds are used to show the performance. According to the experimental results, the accuracy rate is 85%.

Design and implementation of heterogeneous wireless gateway

This study proposed a software-based heterogeneous wireless gateway (HWG) to achieve the integration of multiple heterogeneous wireless networks. In an HWG, received packet is temporarily saved with buffer. And then a packet format conversion mechanism is adopted to enable packet under different wireless network protocols be converted to appropriate formats. Therefore, when the transmission demand occurs, the source nodes and destination nodes at both ends of heterogeneous wireless network can mutually communicate information via this gateway without changing the original communication protocol of each network, based on the modulization design to support multiple communication interface and system extensibility.

A Level-Based Energy Efficiency Clustering Approach for Wireless Sensor Networks

In wireless sensor networks, energy efficiency is an important research issue. The data transmission times could be decreased effectively to achieve energy efficiency by applying a cluster-based structure. This study proposed a level-based energy efficiency clustering approach. Each cluster replaces its cluster head and re-clusters periodically according to the established energy level. A cluster head is a node that has more residual energy and lower communication cost compared to other nodes. This level-based energy efficiency clustering approach could decrease the replacement times of cluster heads, thus avoiding the excessive energy consumption caused by frequent replacement of cluster heads. The simulation results showed that this approach has less energy consumption and can effectively extend the network lifetime.