Hie-Cheol Kim

An Effective Data Dissemination in Vehicular Ad-Hoc Network

Vehicular ad-hoc network (VANET) has several characteristics that are different from mobile ad-hoc network (MANET). Due to these characteristics, the network topology based protocol, often used in MANET, can not be applied to VANET. In this paper, we propose an emergency warning message (EWM) broadcast protocol using range-based relay node selecting algorithm, which determines the minimal waiting time spent by a given node before re-broadcasting the received warning message. Because the waiting time for a message transmission is randomly calculated based on the distance between the sender node and the receiver node, the chosen node as the relay node will have have a minimal waiting time. The results of experiment show the proposed algorithm performed better than the flooding and the distance-based relay nodes selecting algorithm in terms of the network load and the end-to-end delay time. Furthermore, the proposed algorithm can reduce message transmission latency under the circumstances of low node density and short transmission range in VANET.

Performance analysis of tag anti-collision algorithms for RFID systems

Lately, the ISO fixed on UHF Gen2 as one of the standard protocols for RFID, called ISO 18000-6 C, along with ISO 18000-6 A/B. It means that the RFID system should provide the multi-protocol support for tag identification and a proper protocol should be chosen depending on the situation. The tag anti-collision algorithm is one of the important research issues to be on top of the protocol’s performance. This paper introduces several anti-collision algorithms for tag identification in the literature and presents the performance comparison and evaluation of those algorithms based on the 96-bit EPCTM (Electronic Product CodeTM). The performance results show that the collision tracking tree algorithm is found to have the highest performance than any other anti-collision algorithm, identifying 749 tags per second.

An effective multi-hop broadcast in vehicular ad-hoc network

Multi-hop broadcast protocols in vehicular ad-hoc network (VANET) require more prompt message dissemination than traditional broadcast protocols because they mainly deal with vital data involved in driver safety. In this paper, a time reservation-based relay node selection algorithm is proposed in order to achieve immediate message dissemination. All nodes in the communication range of a relay node randomly choose their waiting time within a given time-window. The time-window range is determined by a distance from a previous relay node and a reservation ratio of the time-window. A node with the shortest waiting time is selected as a new relay node. The experimental results show that the proposed algorithm has a shorter end-to-end delay time than the distance-based relay node selection algorithm no matter how node density varies. In particular, when the node density is low, the proposed algorithm has a 25.7% shorter end-to-end time and a 46% better performance in terms of the compound metric than the distance-based relay node selection algorithm.

Experimental research testbeds for large-scale WSNs: a survey from the architectural perspective

Wireless sensor networks (WSNs) have a significant potential in diverse applications. In contrast to WSNs in a small-scale setting, the real-world adoption of large-scale WSNs is quite slow particularly due to the lack of robustness of protocols at all levels. Upon the demanding need for their experimental verification and evaluation, researchers have developed numerous WSN testbeds. While each individual WSN testbed contributes to the progress with its own unique innovation, still a missing element is an analysis on the overall system architecture and methodologies that can lead to systematic advances. This paper seeks to provide a framework to reason about the evolving WSN testbeds from the architectural perspective. We define three core requirements for WSN testbeds, which are scalability, flexibility, and efficiency. Then, we establish a taxonomy of WSN testbeds that represents the architectural design space by a hierarchy of design domains and associated design approaches. Through a comprehensive literature survey of existing prominent WSN testbeds, we examine their best practices for each design approach in our taxonomy. Finally, we qualitatively evaluate WSN testbeds for their responsiveness to the aforementioned core requirements by assessing the influence by each design approach on the core requirements and suggest future directions of research.

Subject-independent human activity recognition using Smartphone accelerometer with cloud support

Human activity recognition is an important task in providing contextual user information. In this study, we present a methodology to achieve human activity recognition using a Smartphone accelerometer independent of a subject compared with other user-dependent solutions. The proposed system is composed of four components; a data collector, a data storage cloud, a workstation module and an activity recogniser. The data collector extracts a unique set of defined features from raw data and sends them to the data storage cloud. The workstation module receives the training data from the cloud and generates classification models. The activity recogniser determines the users current activity based on up-to-date available classifier from the cloud. A prototype is implemented on an android platform to recognise a set of basic daily living activities by placing the Smartphone in different positions to the user and evaluated for offline and online testing to show the scalability and effectiveness.

Poster Abstract: Exploiting Virtually Constant Property for Time-Varying Delay Compensation

Delay compensation is becoming increasingly important due to time-varying delay characteristics over wireless network employed in WSAN-based cyber-physical control systems. Time-varying delay is hard to measure and compensate for it accurately in real-time. This paper presents a delay compensation technique with smith predictor by exploiting virtually constant delay property achieved by playback buffer. Simulation results show that the proposed scheme improves the control performance.

An Adaptive Relay Node Selection Scheme for Alert Message Propagation in Inter-vehicle Communication

An adaptive relay node selection method for transmitting an alert message in communication between vehicles is provided to realize a short message transmission waiting time even though a node is not located in an edge of a communication range, thereby minimizing a message transmission delay time. An original source node and location information of a source node are extracted. Location information of a node is obtained through a GPS(Global Positioning System). It is determined whether a received message is re-transmitted by comparing a broadcast range included in the received message with a distance from the original source node. If the node belongs to the broadcast range, a message transmission waiting time is calculated and selected. If the message transmission waiting time is expired, location information of a source node included in a broadcast message is changed into location information of a node. The received message is re-transmitted.

Development of Multi-Sensor Station for u-Surveillance to Collaboration-Based Context Awareness

Surveillance has become one of promising application areas of wireless sensor networks which allow for pervasive monitoring of concerned environmental phenomena by facilitating context awareness through sensor fusion. Existing systems that depend on a postmortem context analysis of sensor data on a centralized server expose several shortcomings, including a single point of failure, wasteful energy consumption due to unnecessary data transfer as well as deficiency of scalability. As an opposite direction, this paper proposes an energy-efficient distributed context-aware surveillance in which sensor nodes in the wireless sensor network collaborate with neighbors in a distributed manner to analyze and aware surrounding context. We design and implement multi-modal sensor stations for use as sensor nodes in our wireless sensor network implementing our distributed context awareness. This paper presents an initial experimental performance result of our proposed system. Results show that multi-modal sensor performance of our sensor station, a key enabling factor for distributed context awareness, is comparable to each independent sensor setting. They also show that its initial performance of context-awareness is satisfactory for a set of introductory surveillance scenarios in the current interim stage of our ongoing research.

A Smart Agent-Based Grid Computing Platform

Most of Grid computing platforms are usually configured with high performance computing servers, supercomputers, and cluster systems. The research is about to design an aggressive Grid computing platform by utilizing a large number of pervasive PCs as a Grid component. For this goal, an effective configuration method to construct a group of PCs is required as a single Grid component to be used in the same way as those cluster systems are designed and utilized as the same system technology. The configuration method is designed as a layered service architecture, i.e., physical information service, mobile management service, and point-based scheduling service, based on agent technology. The physical information service is to gather and maintain the status information of physical nodes, the mobile management service to guarantee the effective resource management by using the mobile agent, and the point-based scheduling service to provide a simple scheduling policy for the PC-based computing resource. Through this configuration method, the efficiency of the resource management and system throughput are expected to be increased. The experimental result shows that the system using this configuration method can support more than 90% of the expected performance given by a chosen set of running PC resources in general computing environment.

Multi-Channel Packet-Analysis System Based on IEEE 802.15.4 Packet-Capturing Modules

There have been increasing demands for research into multi-channel-based wireless sensor network protocols and applications to support requirements such as increased throughput and real-time or reliable transmission. Researchers or developers of these protocols and applications have to simultaneously analyze the exchanged packets for correctness of both their contents and message exchange timelines. However, if developers were to use multiple conventional single-channel packet sniffers for this purpose, debugging during development and the verification process becomes extremely tedious and difficult because of the need to check the correctness of the protocols over multiple channels individually. Therefore, we present a multi-channel packet-analysis system (MPAS) that helps in debugging and verification for multi-channel protocols or applications. Wireless packets are detected and timestamped by each sniffer module in the MPAS for each channel, and packets are preprocessed and transmitted to a GUI-based analyzer, which then parses the received packets and shows them in order. We present the design and implementation results of the MPAS and evaluate its performance by comparing it against a widely used packet sniffer.